Mtc: Block 3 - Cell/tissue Bio

Front 1

What are the four types of tissue?

Back 1

- Muscle
- Connective Tissue
- Epithelium
- Nerve

Front 2

What are the three types of muscle?

Back 2

- Skeletal
- Cardiac
- Smooth

Front 3

What types of cells are found in skeletal muscle?

Back 3

- Skeletal myocytes (muscle cells)
- Endothelial cells (blood vessel epithelium - vascular system for nourishment)
- Connective tissue (fibroblasts)

Front 4

What is the hierarchy of skeletal muscle? What units is it measured in?

Back 4

- Gross anatomical muscle (cm)
- Fascicles (mm)
- Skeletal myocytes aka fibers/cells (10-100 µm)
- Myofibrils (1-2 µm)
- Myofilaments (nm)

Front 5

How does the number of nuclei per myocyte (muscle cell) differ for skeletal and cardiac muscle?

Back 5

- Skeletal muscle - hundreds of nuclei
- Cardiac muscle - 1-3 nuclei

Front 6

Where are nuclei located in a healthy myocyte (muscle cell)?

Back 6

Periphery (side) of cell (as opposed to in the middle of the cell)

Front 7

What are the three layers of connective tissue that surround muscular tissue?

Back 7

- Epimysium (aka deep fascia) - surrounds whole gross muscles
- Perimysium - surrounds fascicles (bundles of myocytes)
- Endomysium - surrounds individual myocytes

Front 8

What connective tissue is the basal lamina continous with?

Back 8

Endomysium (which surrounds the individual myocyte; therefore there is a basal lamina for every muscle cell)

Front 9

What is the structure at the end of the muscle where the connective tissue invests the skeletal myocytes called?

Back 9

Myotendon junction

Front 10

The connective tissue at the myotendon junction (CT that invests skeletal muscle) is continous with what?

Back 10

Dense regular connective tissue of tendons that attach the muscle to the bone

Front 11

What tool can be used to visualize the striations of skeletal and cardiac muscle

Back 11

Light micrograph

Front 12

What does it mean if the nuclei of skeletal myocytes are centrally located (as opposed to on the periphery)?

Back 12

Pathology or injury

Front 13

What causes the striations in skeletal muscle?

Back 13

- Light bands (I-bands)
- Dark bands (A-bands)

Front 14

What breaks up the light band (I-band)?

Back 14

Z-line (contains α-actinin)

Front 15

What is the space between successive Z-lines called?

Back 15

Sarcomere - fundamental unit of muscle contraction

Front 16

What is the fundamental unit of muscle contraction? Where is it located?

Back 16

Sarcomere - between successive Z-lines

Front 17

What is the light structure that bisects the dark band (A-band)?

Back 17

H-zone - which is bisected by a dark line, the M-line

Front 18

What is found on the M-line (which is in the middle of the H-zone, in the middle of the A-band)?

Back 18

- Skeletal: MM-creatinine kinase (MM-CK)
- Cardiac: MB-CK

Front 19

What are the two types of myofilaments in a myofibril?

Back 19

- Thick filaments (myosin)
- Thin filaments (actin, troponin, tropomyosin)

Front 20

Why are I-bands light?

Back 20

They contain ONLY thin myofilaments (actin, troponin, and tropomyosin)

Front 21

Why are A-bands dark?

Back 21

They contain both thin and thick myofilaments (thick - myosin; thin - actin, troponin, and tropomyosin)

Front 22

What two membrane systems are found at the A-I junction in each myofibril?

Back 22

- Transverse Tubules (T-tubules)
- Sarcoplasmic Reticululm (SR)

Front 23

T-tubules are invaginations of what structure? What is their purpose?

Back 23

- Invaginations of sarcolemma
- Carry depolarization deep into cell to stimulate SR to release Ca2+

Front 24

What structures form the 'triad' at the A-I Junction?

Back 24

- T-tubule in middle
- Two SR membranes surround T-tubule

Front 25

What steps happen in the excitation phase of the excitation-contraction copuling?

Back 25

1. ACh binds the ACh-Receptor
2. Wave of depolarization runs down sarcolemma
3. Wave travels deep into muscle via T-tubule
4. At triad, the T-tubule depolarizes the SR
5. SR releases stored Ca2+, increasing Ca2+ conc. in myofibrils

Front 26

What steps happen in the contraction phase of the excitation-contraction coupling?

Back 26

1. In the thin filament, Ca2+ binds troponin-C (TnC)
2. Troponin-I (TnI) moves, opening up the myosin-binding-sites on actin
3. Actin binds to myosin 'head', which contains ATP that is then hydrolyzed
4. ATP hydrolysis provides energy for 'power-stroke' (thin filaments are pulled into A-band)
5. Sarcomeres shorten; multiple cycles of attachment and release results in contraction

Front 27

How does striated muscle relax?

Back 27

- Specialized ion-channel Ca2+ pump in SR pumps Ca2+ back into SR
- When Ca2+ levels decrease, fresh ATP binds myosin head, actin and myosin are dissociated, and myocyte relaxes

Front 28

What gene is affected in malignant hyperthermia?

Back 28

RYR (Ryanodine Receptor) gene

Front 29

What happens in malignant hyperthermia?

Back 29

- Inherited autosomal dominant mutation of RYR (ryanodine receptor) gene in SR membrane
- Dysregulated Ca2+ transport

Front 30

Why is malignant hyperthermia significant for patients undergoing anesthesia?

Back 30

- Dysregulated Ca2+ transport in Ryanodine Receptor (RYR)
- Sustained skeletal muscle contraction
- Increase in body temperature

Front 31

What is a preventative intervention for dealing with patients with malignant hyperthermia?

Back 31

Administer dantrolene - muscle relaxant that inhibits Ca2+ release through the RYR (ryanodine receptor) channel

Front 32

What causes Rigor Mortis?

Back 32

Absence of fresh ATP prevents acto-myosin dissociation, preventing relaxation thereby resulting in stiffening

Front 33

Can you see striations of skeletal muscle in cross-section?

Back 33

No

Front 34

How many thin filaments surround each thick filament (can be viewed in cross-section with EM)?

Back 34

Six thin filaments surround each thick filament

Front 35

How does skeletal muscle store energy?

Back 35

- ATP
- Creatine Phopshate
- Glycogen
- Fatty acids

Front 36

Sprinters rely more on what type of energy?

Back 36

Glycogen

Front 37

Marathoners rely more on what type of energy?

Back 37

Fatty Acids

Front 38

What are the two types of muscle fibers?

Back 38

Type I = red = slow-twitch
Type II = white = fast-twitch

Front 39

What characteristics define Type I muscle fibers?

Back 39

- Red / slow-twitch
- Enriched in mitochondria and myoglobin
- Use FA oxidation and oxidative metabolism to support continuous contraction

Front 40

What characteristics define Type II muscle fibers?

Back 40

- White / fast-twitch
- Less myoglobin
- Modified for rapid, discontinuous contraction
- Glycolytic or mixed oxidative / glycolytic

Front 41

How can skeletal muscle be regenerated?

Back 41

Resident Adult Stem Cells (Satellite Cells / Myoblasts)

Front 42

Describe the resident adult stem cells (aka satellite cells / myoblasts)?

Back 42

- Regenerate skeletal muscle cells
- Mononuclear, residing between sarcolemma and basal lamina of myocyte (niche)
- Rest in Go phase of cell-cycle in normal tissue
- Enter cell cycle at G1 when basal lamina is damaged

Front 43

What phase of the cell cycle do satellite cells / myoblasts (adult stem cells of muscle tissue) stay in when resting? What stimulates them to leave that phase?

Back 43

- Rest: stay in Go phase
- Enter G1 phase when basal lamina damaged

Front 44

What factor limits the growth of satellite cells / myoblasts (adult stem cells in muscle tissue)?

Back 44

The growth factor myostatin - released by mature myocytes

Front 45

What are myotubes? When are they formed? What happens to them?

Back 45

- Multinuclear muscle cells
- Form when cells irreversibly withdraw from cell-cycle and fuse together
- Undergo robuts muscle differentiation

Front 46

What are two clinical cases in which satellite cells/myoblasts can be used as a part of the treatment?

Back 46

- Cardiac Insufficiency
- Duchenne Muscular Dystrophy (DMD)

Front 47

What were the implications of studies that tried to utilize satellite cells/myoblasts for treatment of cardiac insufficiency?

Back 47

- Modest improvement of ejection fraction
- Several patients exhibited arrhythmia however

Front 48

What was discovered to be the cause of Duchenne Muscular Dystrophy (DMD)?

Back 48

- Mutations in genes encoding dystrophin (sub-sarcolemmal protein that participates in stabilization of myocyte cytoskeleton)
- Without dystrophin, sarcolemma breaks down leading to muscle cell death

Front 49

What is the function of the Dystrophin gene?

Back 49

Sub-sarcolemmal protein that participates in stabilization of myocyte cytoskeleton

Front 50

Describe the gene for Dystrophin and how it can be mutated.

Back 50

- Enormous (2.6 million bp with 97 exons) - takes 16 hrs to transcribe
- Mutations usually introduce premature stop signals for transcription
- X-linked mutation (so affects males only)

Front 51

What is the best available treatment for Duchenne Muscular Dystrophy (DMD)?

Back 51

- Prednisone, or gentamicin, which enable transcription read-through of stop codons
- Also new interventions are being studied including cellular therapy, gene therapy, orally administered drugs, and inhibition of myostatin

Front 52

How would cellular therapy be targetted towards Duchenne Muscular Dystrophy (DMD)?

Back 52

Use myo-satellite or bone marrow-derived adult stem cells

Front 53

How would gene therapy be targetted towards Duchenne Muscular Dystrophy (DMD)?

Back 53

Via adenovector-mediated introduction of normal dystrophin genes into skeletal myocytes

Front 54

What orally-administered drug can be used to treat Duchenne Muscular Dystrophy (DMD)?

Back 54

PTC124 - circumvents unscheduled stop signals in mutated Dystrophin gene

Front 55

How are cardiac muscle and skeletal muscle similar?

Back 55

- Basal lamina
- Striated
- Contractile proteins
- Mechanism of contraction

Front 56

How is cardiac muscle different from skeletal muscle?

Back 56

- Involuntary
- Smaller myocytes
- Only 1-3 central nuclei
- Myocytes branch
- More vascular, more mitochondria, more myoglobin, and more lipid droplets
- MB-Creatinine Kinase (MB-CK)
- Intercalated discs (enables synchronous contraction)

Front 57

What is the objective of the vascular system?

Back 57

To maintain quality and volume (10-15L in adults) of ECF

Front 58

How far can a cell be from a nurturing capillary?

Back 58

200 μm

Front 59

The vascular system is covered by what three 'tunics'?

Back 59

- Tunica adventitia
- Tunica media
- Tunica intima

Front 60

What kind of tissue makes up the tunica adventitia? What layer is this?

Back 60

Mostly Connective Tissue (CT) - outermost

Front 61

What kind of tissue makes up the tunica media? What layer is this?

Back 61

Smooth muscle cells (SMCs) and CT - middle layer

Front 62

What kind of tissues make up the tunica intima? What layer is this?

Back 62

Endothelium with basal lamina and CT - innermost layer

Front 63

What is the 'vasa vasorum'? Where is it located?

Back 63

- 'Vessels of the vessels' - the blood vessels have their own blood supply
- Found in tunica adventitia (outermost layer)

Front 64

What is the 'nervi vascularis'? Where is it located?

Back 64

- Nerve supply of blood vessels
- Found in tunica adventitia (outermost layer)

Front 65

Which layer of the three tunics of the vascular system is the most variable?

Back 65

Tunica media

Front 66

What kind of cells form the endothelium of the tunica intima (aka epithelium) of the vascular structures?

Back 66

Single flat (i.e., squamous) cells

Front 67

What connects the endothelial cells of blood vessels?

Back 67

Tight junctions

Front 68

What is the name of the three tunics when applied to the heart?

Back 68

- Epicardium (~ tunica adventitia = outer)
- Myocardium (~ tunica media = middle)
- Endocardium (~ tunica intima = inner)

Front 69

What kind of cells are found in the epicardium (~ tunica adventitia)?

Back 69

- Simple squamous mesothelium
- CT
- Blood vessels and nerves (vasa vasorum and nervi vascularis) enter heart here

Front 70

What kind of cells are found in the myocardium (~tunica media)?

Back 70

- Cardiac myocytes
- Cardiac fibroblasts

Front 71

At what tunic do the coronary arteries and veins enter the heart?

Back 71

Myocardium (~tunica media)

Front 72

What kind of cells are found in the endocardium (~ tunica intima)?

Back 72

- Simple squamous endothelium with basal lamina
- Connective Tissue (CT)

Front 73

Where are the cardiac conduction system (Purkinje fibers) located?

Back 73

'Sub'-endocardium

Front 74

How do arteries compare to veins?

Back 74

- Arteries have relatively thick, highly developed wall, with small lumen
- Veins have a relatively thin, under-developed wall with a large lumen

Front 75

Which tunic is highly developed in arteries? What is significant about this layer?

Back 75

Tunica media - with elastin and smooth muscle cells (SMCs)

Front 76

Which tunic is the most developed in veins? Which layer is almost non-existant?

Back 76

- Tunica adventitia - thickest covering (outer)
- Tunica media - relatively nondescript (middle)

Front 77

What defines the tunica intima of large (elastic) arteries?

Back 77

- Tight junctions
- Pinocytotic vesicles that transport nutrients from lumen to tissue and endothelial cells that secrete Factor VIII, which functions in blood coagulation

Front 78

What is the function of large elastic arteries?

Back 78

Maintain blood pressure during diastole

Front 79

In what layer of the vessel tunic does an aneurysm occur?

Back 79

Outpocketing of tunica media of large arteries

Front 80

What characterizes the medium (muscular) arteries?

Back 80

- Prominent external elastic lamina in tunic adventitia
- Prominent layer of ~40 smooth muscle cells (SMCs) in tunica media (less elastin)
- Prominent elastic lamina in tunica intima

Front 81

What is the function of the medium (muscular) arteries?

Back 81

Maintain blood pressure via Smooth Muscle Cell (SMC) contraction in tunica media

Front 82

In what vessels do atherosclerotic plaques form?

Back 82

Medium (muscular) arteries

Front 83

What cells can form atherosclerotic plaques?

Back 83

- Macrophages
- Smooth muscle cells (SMCs)

Front 84

How do macrophages contribute to atherosclerotic plaque formation in medium arteries?

Back 84

Macrophages migrate to sites of endothelial wall damage (caused by hypertension, microbes, etc) where they ingest lipid (LDL and cholesterol)

Front 85

How do Smooth Muscle Cells (SMCs) contribute to atherosclerotic plaque formation in medium arteries?

Back 85

SMCs migrate to tunica intima where they proliferate and take-up LDL (bad cholesterol)

Front 86

What does the term 'foam cells' refer to?

Back 86

The combination of lipid-laden macrophages and smooth muscle cells (SMCs) which form artery-blocking plaques

Front 87

Which type of venules have valves?

Back 87

Medium veins and small veins

Front 88

What are the valves in the medium and small veins made from?

Back 88

Folds of tunica intima

Front 89

What is 'phlebitis'?

Back 89

Inflammation of a vein, usually in the leg, which can be a prelude to thrombosis

Front 90

What are 'varicosities'?

Back 90

Stretching of veins (medium and small); exacerbated by a sedentary lifestyle

Front 91

How large is the diameter of the small arteries and arterioles? How does this compare to the size of an RBC?

Back 91

- 50 μm in diameter
- 6-7 RBCs can pass at once

Front 92

How many layers of smooth muscle cells (SMCs) are found in small arteries and arterioles?

Back 92

- Small arteries = 8 layers
- Arterioles = 2 layers
- Found in tunica media

Front 93

What is a clinical problem associated with the small arteries and arterioles?

Back 93

- Narrowing of lumen due to uptake of lipid by SMCs in tunica media
- Leads to hypertension

Front 94

What regulates the bloodflow to the vascular bed?

Back 94

Smooth muscle cells (SMCs) in the arteriolar wall

Front 95

How large is the diameter of the venules?

Back 95

~ 50 μm (same as the small artery diameter)

Front 96

How do leukocytes enter the tissue space?

Back 96

- Via diapedesis
- Enter into post-capillary venules

Front 97

How large is the diameter of the capillaries?

Back 97

~10 μm (1/5 the size of the small arteries/arterioles/venules)

Front 98

What tunics are found in the capillary wall?

Back 98

Only a single layer of endothelium with basal lamina (no tunica adventitia or tunica media)

Front 99

The diameter of the capillary allows how many RBCs to pass?

Back 99

~10 μm allows 1 RBC to pass at a time
- 1 RBC = 7.5 μm

Front 100

What is the size of a RBC (diameter)?

Back 100

~7.5 μm

Front 101

What are the three morphological types of capillaries?

Back 101

- Continuous capillaries (Type I)
- Fenestrated capillaries (Type II)
- Sinusoidal (discontinuous) capillaries (Type III)

Front 102

What kind of tissues contain continuous capillaries (Type I)?

Back 102

Heart, skeletal muscle, CNS, lung

Front 103

What kind of tissues contain fenestrated capillaries (Type II)?

Back 103

Endocrine organs, GI tract, kidney

Front 104

What kind of tissues contain sinusoidal (discontinuous) capillaries (Type III)?

Back 104

Bone marrow, liver, spleen

Front 105

What can continuous capillaries transport?

Back 105

O2

Front 106

What can fenestrated capillaries transport?

Back 106

Hormones, nutrients, ions

Front 107

What can sinusoidal (discontinuous) capillaries transport?

Back 107

Whole cells

Front 108

What characterizes the continuous capillaries (Type I)?

Back 108

- Endothelial cells with tight junctions
- Pinocytotic vesicles (except in CNS) transport stuff from blood vessel to adjacent connective tissue

Front 109

What characterizes the fenestrated capillaries (Type II)?

Back 109

- Fenestrations are ~100 nm
- Windows may represent permanent pinocytotic vesicles
- Fenestrations admit passage of molecules >10 kDa

Front 110

What characterizes the sinusoidal (discontinuous) capillaries (Type III)?

Back 110

- Large structures, including whole cells can pass between them
- Basal lamina is also discontinuous
- ~30 μm diameter
- Filter out whole RBCs

Front 111

What is the function of the capillary endothelial cells? How do molecules pass across membrane?

Back 111

- Exchange gases and nutrients
- Gases go directly through cell membrane
- Nutrients pass via pincoytotic vesicles, fenestrations, and discontinuities
- Small molecules (<10 kDa) pass between adjacent endothelial cells
- Larger molecules (>10 kDa) transported directly through cell via pinocytosis or fenestrae

Front 112

What are the vasoactive factors secreted by endothelial cells?

Back 112

- Endothelin - potent vasoconstrictor
- NO (nitric oxide) - vasorelaxant

Front 113

What are the growth factors / cytokines secreted by endothelial cells?

Back 113

- Fibroblast Growth Factor (FGFs)
- Platelet-Derived Growth Factor (PDGF)
- Interleukins

Front 114

Lymphatics are found in all tissues except for what?

Back 114

- Bone marrow
- CNS

Front 115

What is the function of lymphatics?

Back 115

- One-way drainage from extracellular space to venules/veins
- Very leaky vessels

Front 116

Lymphatic fluid contains what components?

Back 116

WBCs and lipid

Front 117

What is the difference between angiogenesis and vasculogenesis?

Back 117

- Angiogenesis - regeneration of blood vessels in adults
- Vasculogenesis - generation of blood vessels in embryo

Front 118

What are the various vascular endothelial cell membrane ligands/receptors involved in angiogenesis?

Back 118

- Vascular endothelium growth factor / receptor (VEGF/R)
- Fibroblast growth factor / receptor (FGF/R)
- TIE-2 receptor for angiopoietin

Front 119

What are some inhibitors of blood vessel formation?

Back 119

- Angiostatin (derivative of plasminogen)
- Endostatin (derivative of collagen isoform XVIII)

Front 120

In what kind of diseases would pro-angiogenic therapy be beneficial?

Back 120

- Ischemic heart disease
- Diabetes

Front 121

What hormones are used for pro-angiogenic therapy?

Back 121

- VEGF (vascular endothelium growth factor)
- FGF (fibroblast growth factor)

Front 122

In what kind of diseases would anti-angiogenic therapy be beneficial?

Back 122

Cancerous tumors - starve tumors to death by preventing formation of vascular supply

Front 123

What drug can be used to inhibit angiogenesis to a tumor? How results have been shown with this drug in mice with cancer?

Back 123

Endostatin --> decreases tumor volume in mice

Front 124

What is the purpose of the drug 'Avastin' aka Bevacizumab?

Back 124

- Anti-angiogenic molecule
- Inhibits VEGF (vascular endothelium growth factor)
- Used to treat colo-rectal, breast, and non-small cell lung tumors that have metastacized

Front 125

What other drug can be used in combination with Avastin?

Back 125

- Thalidomide - synthetic anti-angiogenic
- Avastin - inhibits VEGF

Front 126

Where are the nuclei of skeletal muscle fibers located?

Back 126

Peripherally

Front 127

What are the pink, wispy material found in the endomysium of skeletal muscles?

Back 127

Collagen fibers

Front 128

What structures can be seen within the endomysium of skeletal muscles?

Back 128

- Collagen fibers (light pink wispy material)
- RBCs in capillaries (refractile/shiny, eosinophilic)

Front 129

Groups of myofibers (muscle cells) are called what? What surrounds them?

Back 129

Fascicles - surrounded by perimysium

Front 130

What structures can be seen within the perimysium of skeletal muscles?

Back 130

- Arterioles
- Venules
- Nerves

Front 131

What shape are the myofibers (muscle cells)?

Back 131

Cylindrical

Front 132

How many nuclei are associated with each skeletal muscle myofiber?

Back 132

Many

Front 133

Do skeletal muscle myofibers normally branch?

Back 133

No

Front 134

Dark patches on the muscle fibers mark location of what?

Back 134

Motor end plates

Front 135

What is located at the motor end plate?

Back 135

Region where a motor neuron contacts a skeletal muscle myofiber

Front 136

A motor neuron releases what hormone at the motor end plate?

Back 136

Acetylcholine (ACh)

Front 137

What enzyme deactivates ACh?

Back 137

Acetylcholinesterase

Front 138

Where is acetylcholinesterase located?

Back 138

In the synaptic cleft (at the motor end plate)

Front 139

What happens to a muscle with disuse?

Back 139

- Muscle atrophy
- Muscle fatigues more readily
- Structurally weaker sarcomeres and myotendinous junctions
- Microscopic tears occur when weight is put on the muscle - this further weakens the muscle

Front 140

What is located between the basal lamina and plasma membrane of muscle cells?

Back 140

Satellite cells - distinct class of myogenic cells

Front 141

What is the source of myoblasts?

Back 141

Satellite cells

Front 142

What would the clinical significance of finding or engineering satellite cells for cardiac muscle?

Back 142

Possibility of cardiac mucle regeneration

Front 143

What is the function of the neuromuscular spindle?

Back 143

Stretch receptor that regulates muscle tone

Front 144

Which structure is surrounded by a capsule in the perimysium?

Back 144

Neuromuscular spindle (inside capsule are intrafusal fibers)

Front 145

What layer is found on the proximal 1/3 of the esophagus (outer-most layer)? What is found in this layer?

Back 145

Muscularis externa - skeletal muscle

Front 146

What is found in the distal 1/3 of the esophagus (inner-most layer)?

Back 146

Smooth muscle

Front 147

What is found in the middle 1/3 of the esophagus?

Back 147

Combination of skeletal and smooth muscle

Front 148

What is the shape of smooth muscle cells? How does this affect the diameter of the cells in cross-section?

Back 148

Spindle-shaped (as opposed to cylindrical) --> this causes a variable diameter size

Front 149

Do cross-sections of smooth muscle cells often show nuclei?

Back 149

No, because of their spindle shape

Front 150

How many nuclei are in a smooth muscle cell?

Back 150

1

Front 151

Where is the smooth muscle cell nucleus located?

Back 151

Centrally

Front 152

How can the ductus deferens be identified in a spermatic cord cross-section?

Back 152

Lumen surrounded by a thick muscular wall; elongated nuclei in smooth muscle cells ('cigar-shaped')

Front 153

How are smooth muscle cells arranged around the lumen of a blood vessel?

Back 153

Circular (not longitudinal)

Front 154

Why is it functionally advantageous for smooth muscle cells to be arranged circularly around the lumen of a blood vessel?

Back 154

Enables regulation of blood vessel diameter thereby affecting blood pressure and flow

Front 155

What mucle is located around the periphery of the spermatic cord?

Back 155

Cremaster

Front 156

Do cardiac muscle cells normally branch?

Back 156

Yes

Front 157

Where are cardiac muscle cell nuclei located?

Back 157

Centrally

Front 158

Why are the cross-sectional diameters of cardiac myofibers variable?

Back 158

Branching of myofibers

Front 159

What are the two components of the circulatory system?

Back 159

- Cardiovascular system
- Lymphatic system

Front 160

What are the functions of the cardiovascular system?

Back 160

- Transportation of O2, nutrients, waste products, body fluid, solutes, and immune system components
- Facilitates body heat homeostasis

Front 161

What separates the tunica intima from the tunica media?

Back 161

Internal elastic lamina

Front 162

What kind of vessels have external elastic lamina? What is it between?

Back 162

Large arteries - found between tunica media and tunica adventitia

Front 163

What are the three elastic laminae levels?

Back 163

- Internal elastic lamina (between tunica intima and tunica media)
- Fenestrated elastic laminae (within tunica media)
- External elastic lamina (between tunica media and tunica adventitia)

Front 164

What does 'fenestra' mean?

Back 164

Windows

Front 165

What do the fenestrated elastic laminae in the tunica media look like on a slide?

Back 165

Dark pink wavy lines

Front 166

What is the function of the fenestrated elastic laminae?

Back 166

Maintain constant arterial pressure by stretching during ventricular contraction (systole) and recoiling during ventricular relaxation (diastole)

Front 167

The nuclei within the tunica media of elastic arteries belong to what cell type?

Back 167

Smooth muscle cells

Front 168

What can be said about the tunica adventitia in elastic arteries?

Back 168

Unremarkable

Front 169

How do the fenestrated elastic laminae compare in the elastic arteries vs muscular arteries?

Back 169

Less prominent in the muscular arteries

Front 170

What is the function of the vasa vasorum? Where is it located?

Back 170

- Provide nutrients to smooth muscle of artery
- Found in tunica adventitia

Front 171

What procedure can enlarge the coronary artery lumen?

Back 171

Angioplasty

Front 172

What can prevent restenosis after an angioplasty?

Back 172

Endothelialization - promoted by local administration of endothelial cell growth factor (e.g. VEGF) or estrogen-loaded stents (which promote healing and reduce SMC migration and proliferation as well as attract circulating endothelial cells)

Front 173

What kind of cells line the uterine tube?

Back 173

Simple columnar epithelium

Front 174

What characterizes an arteriole?

Back 174

- External diameter <100 μm (~15 RBC)
- Wall thickness approximately equals lumen diameter
- Little or no subendothlial connective tissue
- 2-5 SMC layers in tunica media
- No external elastic lamina
- Very thin tunica adventitia

Front 175

What regulates blood flow from arterioles to capillaries?

Back 175

Metarterioles with precapillary sphincters

Front 176

What is the lumen diameter of the capillaries?

Back 176

~ 7 μm (~1 RBC)

Front 177

What forms the wall of the capillary?

Back 177

Single endothelial cell

Front 178

What tool is needed to distinguish between capillary type?

Back 178

Electron Microscopy (EM)

Front 179

How do tumor cells signal the need for angiogenesis?

Back 179

- Secrete vascular permeability factor (VPF) aka vascular endothelial growth factor (VEGF)
- VEGF binds endothelial cells of nearby blood vessels and induces a microvascular hyperpermeability
- Leakiness leads to extravasation of plasma proteins and stromal changes which promote angiogenesis

Front 180

What happens in the in situ hybridization technique?

Back 180

- Radioactive nucleotide used to synthesize a nucleic acid 'probe' that contains a sequence complementary to the mRNA of interest
- Probe is applied to a tissue section that is mounted on a microscope slide
- Probe hybridizes with mRNA of interest in tissue
- Site of probe and the mRNA is detected by autoradiography

Front 181

What is the purpose of the in situ hybridization technique?

Back 181

To localize specific mRNAs within cells

Front 182

How is epithelial tissue (ET) distinguished from connective tissue (CT)?

Back 182

- ET is entirely cellular with the only CT being from the basement membrane
- CT has very few cells with abundant extracellular matrix (ECM)

Front 183

What are the functions of the epithelial tissue?

Back 183

- Protection
- Diffusion
- Absorption
- Secretion
- Excretion
- Sensation

Front 184

What does epithelial tissue (ET) protect the body from? What kind of ET's main function is protection?

Back 184

- Mechanical injury
- Chemical injury
- Pathogenic invasion
- Water loss
- E.g., epidermal layers of skin

Front 185

What does epithelial tissue (ET) promote diffusion of? What kind of ET's main function is diffusion?

Back 185

- Gases
- Liquids
- Nutrients
- E.g., lung epithelium

Front 186

How does epithelial tissue (ET) function in absorption? What is an example of this?

Back 186

- Uptake of materials from a lumen
- E.g., digestive tract

Front 187

What kind of substances do epithelial tissues (ET) secrete? What kind of ET secretes?

Back 187

- Mucus
- Hormones
- Enzymes
- E.g., glands (pancreas)

Front 188

What kind of epithelial tissues excrete waste products from the body?

Back 188

Renal epithelium

Front 189

What are some examples of epithelial tissue that detect sensory stimuli?

Back 189

- Inner ear cells
- Eye (retina) cells

Front 190

What are the three characteristics of epithelial tissues (ET)?

Back 190

- Polarized (basal vs apical vs lateral surfaces)
- Avascular (no direct blood supply; receives nutrients by diffusion)
- Basement membrane (ECM that basal layer lies upon)

Front 191

What are the three surfaces of an epithelial cell?

Back 191

- Apical (towards lumen)
- Basal (against basement membrane)
- Lateral (sides)

Front 192

How do epithelial cells receive nutrients/hormones/etc. and remove waste products?

Back 192

In and out of cell via diffusion; there is no blood supply directly to cells ('avascular')

Front 193

What are the ways in which epithelial cells can be organized?

Back 193

- Number of cellular layers (simple/stratified/pseudostratified)
- Shape of cells (squamous/cuboid/columnar)
- Presence of cell-surface modifications

Front 194

What is the difference between simple, stratified, transitional, and pseudostratified epithelia?

Back 194

- Simple = single layer of cells
- Stratified = 2+ layers of cells (only basal cell layer contacts basement membrane)
- Transitional = stratified but number of apparent layers differs when it is relaxed vs stretched
- Pseudostratified = appears to have more than one layer but really all cells contact basement membrane making it really a 'simple' epithelia

Front 195

What kind of epithelium is found in the urinary tract? Why does this make sense?

Back 195

- Transitional epithelium
- When bladder is full, epithelium stretches causing appearance of fewer layers than when relaxed

Front 196

Where is a location where pseudostratified epithelium is found?

Back 196

Respiratory epithelium

Front 197

What is a quick way to distinguish between pseudostratified and a truly stratified epithelium?

Back 197

Stratified epithelium are NEVER ciliated; so if you see cilia it is pseudostratified

Front 198

What does a squamous cell look like? What function does this serve?

Back 198

Flat (Scale-like) - ideally suited for diffusion (simple squamous)

Front 199

What does a cuboid cell look like? What function do they typically serve?

Back 199

Cube-shaped (intermediate between squamous and columnar); small ducts and tubules (simple cuboidal)

Front 200

What does a columnar cell look like? What function does it commonly serve?

Back 200

Rectangular in shape - ideally suited for high metabolic function; also for absorptive tissues and secretory tissues

Front 201

What are the types of epithelium?

Back 201

- Simple squamous
- Simple cuboidal
- Simple columnar
- Stratified squamous
- Stratified cuboidal
(NO stratified columnar!)
- Pseudostratified columnar
- Transitional

Front 202

What are examples of cell surface specializations for epithelial cells?

Back 202

- Keratinized epithelium
- Glycocalyx

Front 203

What happens to epithelial cells that are keratinized?

Back 203

- Outermost surface of stratified epithelium becomes covered by intermediate filament protein keratin
- During maturation, cells accumulate protein keratin and lose their nuclei
- Keratin protein is wrapped in residual plasma membrane
- Keratinization provides a tough, water-resistant, non-living surface to protect from abrasion and dehydration

Front 204

What is the function of keratinization of epithelium?

Back 204

- Provide a tough, water-resistant, non-living surface on outside
- Protects from abrasion and dehydration

Front 205

What is another name for a keratinized epithelium?

Back 205

'Cornified epithelium' = (epithelium of skin)

Front 206

What kind of cells typically become keratinized?

Back 206

Stratified epithelium; skin cells

Front 207

What happens to epithelial cells that have the glycocalyx modification?

Back 207

- Carbohydrate-rich complex formed on extracellular surface
- Functions in cellular protection and recognition

Front 208

What is an example of a type of epithelium that has the glycocalyx modification?

Back 208

Intestinal epithelium

Front 209

Where are cilia commonly found?

Back 209

- Respiratory tract
- Oviduct
- Single, highly elaborated cilium (aka flagellum) used by sperm
- Cells that have a need to propel material through a tube

Front 210

What are the mechanical-structural components of cilia?

Back 210

- Basal body / centriole anchors cilia at surface (contains 9 triplets of microtubules)
- 9 doublets of peripheral microtubules with dynein (ATPase motor) arms + 2 central microtubules project outward forming the fingerlike extension
- 9+2 arrangement = axoneme

Front 211

What is the function of microvilli? Where are they commonly found?

Back 211

Increase surface area for absorption (commonly found in intestinal tract and proximal renal tubule)

Front 212

What are the mechanical-structural components of microvilli?

Back 212

- Each microvillus contains actin microfilaments cross-linked by villin
- Actin and villin connect to a 'terminal web' consisting of actin and spectrin molecules and intermediate filaments
- Actin bundles attach to lateral plasma membrane via myosin and calmodulin

Front 213

What is another name for microvilli when they are on the apical surface?

Back 213

Brush border

Front 214

What are some lateral cell membrane specializations?

Back 214

- Zonula occludens (aka tight junctions or occluding junctions)
- Zonula adherens (aka adherens junctions)
- Macula adherens (aka desmosome)
- Gap junctions

Front 215

What are examples of apical cell membrane specializations?

Back 215

- Cilia
- Microvilli

Front 216

What kind of microscope must be used to detect cilia?

Back 216

Light microscope

Front 217

What kind of microscope must be used to detect microvilli?

Back 217

Electron microscope

Front 218

What are some of the general functions of lateral cell membrane specializations?

Back 218

- Coherence
- Communication
- Distribute stress

Front 219

What kind of microscope must be used to detect lateral cell membrane specializations?

Back 219

Electron microscope

Front 220

Where are zonula occludens (or tight junctions) located?

Back 220

- Lateral cell membrane near apical cell surface
- Completely surrounds cell

Front 221

What can pass through a zonula occludens (tight junction)?

Back 221

- Water
- Small solutes

Front 222

What special purpose do zonula occludens (tight junctions) provide?

Back 222

Coerce transcellular transport across polarized cells instead of paracellularly

Front 223

What feature can be viewed on an EM to classify a zonula occludens (tight junction)?

Back 223

Pentalaminar (five-layered) appearance = dark-light-dark-light-dark

Front 224

What causes the pentalaminar appearance of the zonula occludens (tight junction)?

Back 224

Fusion of outer members of lipid bilayers of two adjacent cells

Front 225

What proteins are involved in zonula occludens (tight junction)?

Back 225

- Occludin
- Claudin
- Junctional adhesion molecule (JAM)

Front 226

What do the tight junction proteins (occludin, claudin, and JAM) interact with in the sub-plasmalemmal plaque?

Back 226

Interact with actin cytoskeleton via Zonula Occludens proteins (ZOs)

Front 227

Where are the zonula adherens (adherens junction) modifications located?

Back 227

- Lateral cell surface just beneath the Zonula Occludens (which is found closest to apical surface)
- Completely surround cell like a belt

Front 228

What are the three components of the zonula adherens (or adherens junctions)?

Back 228

- Cadherin - transmembrane linker proteins
- Sub-plasmalemmal plaque proteins (catenins, α-actinin, vinculin, and others)
- Actin microfilaments - cytoskeletal filaments

Front 229

What is cadherin? What is it a part of?

Back 229

- Ca2+ dependent protein in the CAM (Cell Adhesion Molecule) family
- Important for transmembrane linkage for zonula adherens (adherens junctions)

Front 230

What proteins are found in the sub-plasmalemmal plaques of zonula adherens?

Back 230

- Catenins
- α-actinin
- Vinculin

Front 231

What are the prominent members of the cadherin family found in adherens junctions? Where are they commonly found?

Back 231

- E-cadherin - many epithelia
- N-cadherin - neurons, heart, skeletal muscle, lens, and fibroblasts
- P-cadherin - placenta, epidermis, breast epithelium
- VE-cadherin - endothelial cells

Front 232

Where is the macula adherens (aka desmosome) located?

Back 232

Lateral surface of epithelial cells; do not encircle cell like a belt, rather aka 'spot welds'; common in epidermis

Front 233

What are the components of the macula adherens (desmosomes)?

Back 233

- Transmembrane linker protein: non-classical cadherin (aka desmogleins and desmocollins)
- Sub-plasmalemmal plaque proteins: desmoplakin, plakoglobin, and plakophilin
- Cytoskeletal filaments: keratin (intermediate filament)

Front 234

What are the functions of macula adherens (desmosomes)?

Back 234

Provide mechanical strength (hence why they are common in the epidermis)

Front 235

What do macula adherens (desmosomes) look like on an EM?

Back 235

Train tracks

Front 236

What is the function of gap junctions?

Back 236

To provide electrical and metabolic communication channels on lateral membrane of epithlial cells

Front 237

What is the structure of a gap junction?

Back 237

- 2 Connexons join two adjacent cells
- Each connexon is made of 6 subunits called connexins
- Total of 12 Connexins
- Channel is ~1.5 nm

Front 238

What is the size of the gap junction? What size molecules can fit through this?

Back 238

~1.5 nm
Small molecules <1500 Daltons can fit through (Ions, sugars, AAs, nucleotides, vitamins, cAMP, IP3)
NOT: proteins, nucleic acids, polysaccharides, etc.

Front 239

What are some basal membrane specializations of epithelial cells?

Back 239

- Hemidesmosomes
- Adhesion plaques

Front 240

In general, what is the function of basal membrane specializations of epithelial cells?

Back 240

Mechanical attachment to ECM of basement membrane - anchoring junctions

Front 241

What is the structure of hemidesmosomes?

Back 241

Transmembrane linker proteins: integrins - attach to major ECM components (laminin, collagen, and fibronectin)

Front 242

What do hemidesmosomes attach to?

Back 242

Major ECM components: laminin, collagen, fibronectin) rather than to the cell

Front 243

What do adhesion plaques attach to?

Back 243

ECM components via integrins rather than directly to the cell

Front 244

What are adhesion plaques similar to? How?

Back 244

Zonula adherens (type of lateral epithelial cell modification) because the plaque contains α-actinin and vinculin which attach to the actin microfilaments

Front 245

What kind of junctions utilize actin microfilaments?

Back 245

- Zonula occludens
- Zonula adherens
- Adhesion plaques

Front 246

What kind of junctions utilize intermediate filaments?

Back 246

- Macula adherens (desmosomes)
- Hemidesmosomes

Front 247

What kind of junctions utilize integrin as their transmembrane linker protein?

Back 247

- Hemidesmosomes
- Adhesion plaques
(Both basal membrane specializations)

Front 248

What are the junction(s) that function for occlusion?

Back 248

Zonula occludens

Front 249

What are the junction(s) that function for anchoring?

Back 249

- Zonula adherens
- Macula adherens (desmosomes)
- Hemidesmosomes
- Adhesion plaques

Front 250

What are the junction(s) that function for communication?

Back 250

Gap junctions

Front 251

What is a junctional complex?

Back 251

Group of cell membrane specializations along the lateral surface of epithelial cells including the zonula occludens, zonula adherens, and macula adherens

Front 252

Can epithelial cells replace themselves?

Back 252

Yes; turnover rate depends upon location and function (although some do not renew at all)
- Ex: skin - 28 days; small intestine - 5 days

Front 253

What is metaplasia?

Back 253

Changes in epithelial cells to a biochemically different type

Front 254

What are carcinomas?

Back 254

Malignant tumors of epithelial cells

Front 255

What are adenocarcinomas?

Back 255

Malignant tumors of epithelial glandular cells

Front 256

How common are carcinomas and adenocarcinomas relative to all cancers?

Back 256

Comprise 85% of all cancers

Front 257

What is the explanation for why carcinomas and adenocarcinomas are so common among cancers?

Back 257

- Mitotic activity of epithelial cells
- And/or the position of epithelial cells as barriers to an environment from which they receive insults

Front 258

What is important for preventing the metastatic spread of carcinomas and adenocarcinomas?

Back 258

Mechanisms that prevent loss of epithelial adhesiveness

Front 259

What can be done to detect the type of intermediate filament proteins present in tumor cells? Why would this be important?

Back 259

- Immunohistochemical staining
- Determine origin of tumor so that you can use appropriate anti-tumor therapies

Front 260

What are some markers of different cell types that make them identifiable by immunohistochemical staining?

Back 260

- Keratin - epithelial tumors
- Glial fibrillary acidic protein - glia tumors
- Desmin - muscle tumors
- Vimentin - connective tissue tumors

Front 261

What are the functions of connective tissue?

Back 261

- Mechanical support / structure
- Exchange of metabolites
- Storage of energy reserves
- Protection from infection
- Repair following injury

Front 262

What are the components of connective tissue?

Back 262

- Fixed cells
- Free (or wandering) cells
- Extracellular matrix (ECM)

Front 263

How do fixed cells and free cells differ in connective tissue?

Back 263

- Fixed cells - stable, long-lived (wks-months), develop from mesenchyme
- Free cells - changing, short-lived (days), enter CT from blood vessels

Front 264

What is a unique capability of fixed cells of connective tissue? What does this mean?

Back 264

Regenerate in mature tissue - indicates population of stem cells persist

Front 265

What are the two types of fixed cells in connective tissue?

Back 265

- Fibroblasts - form ECM
- Adipocytes - store lipids

Front 266

What is the general function of free (wandering) cells of connective tissue?

Back 266

Specific defense cells (WBCs)

Front 267

What are the types of free (wandering) cells of connective tissue?

Back 267

WBC:
- Eosinophils
- Macrophages
- Lymphocytes
- Plasma cells
- Mast cells
- Neutrophils

Front 268

What does extracellular matrix consist of?

Back 268

- Fibers and fluid matrix (ground substance)
- Determines physical properties of each type of supporting tissue

Front 269

How does connective tissue function in mechanical support?

Back 269

- Bundles cells of the same tissue type together
- Anchors tissues to each other to form organs
- Binds organs together

Front 270

How does connective tissue function in the exchange of metabolites between blood and tissues?

Back 270

Ground substance of ECM provides hydrated medium for diffusion of metabolites

Front 271

How does connective tissue function in the storage of energy reserves?

Back 271

- Storage of lipids in fat cells
- Storage of proteins (albumin, immunoglobulin) in the ECM and the blood

Front 272

How does connective tissue function in protection against infection?

Back 272

- Phagocytosis by macrophages, neutrophils and eosinophils
- Mast cell degranulation during inflammation

Front 273

How does connective tissue function in repair following injury?

Back 273

Fibroblasts proliferate and secrete during wound healing

Front 274

What is the non-cellular component of connective tissue?

Back 274

Extracellular matrix (ECM)

Front 275

What is the extracellular matrix (ECM)?

Back 275

- Non-cellular component of connective tissue
- Non-living macromolecules that are manufactured by the cells that make up the tissue
- Exported by them into the extracellular space

Front 276

What is the function of the extracellular matrix (ECM)?

Back 276

- Structural stability
- Determine properties of tissues

Front 277

How does the matrix:cell ratio differ for various tissues?

Back 277

- High (lots of matrix, not a lot of cells) in connective tissue
- Low (lots of cells, not a lot of matrix) in nervous tissue

Front 278

What happens to extracellular matrix (ECM) in bones?

Back 278

Becomes calcified to form rock-hard substances

Front 279

What are some variations in extracellular matrix that are suited for the needs of the tissue?

Back 279

- Calcified to become rock-hard for bone and teeth
- Transparent for cornea
- Rope-like organization to give tendons tensile strength

Front 280

What is the function of the ground substance in the extracellular matrix (ECM)? of the fibers?

Back 280

- Ground substance resists forces of compression
- Fibers withstand tensile forces

Front 281

What is the ground substance of ECM composed of?

Back 281

- Glycosaminoglycans (GAGs) - unbranched polysaccharide chains consisting of repeating disaccharide units
- Proteoglycans - core protein linked to GAGs

Front 282

What are the fibrous components of ECM?

Back 282

- Collagen - triple helix of α chains
- Cross-linked Elastin - coated with fibrillin - capable of stretch and recoil

Front 283

What binds the extracellular matrix (ECM) to the cell?

Back 283

Adhesive glycoproteins such as laminin and fibronectin by binding to integrins located in cell membrane

Front 284

What is found at the interface between epithelium and connective tissue?

Back 284

Felt-like cell rug called the basal lamina

Front 285

What is the purpose of the basal lamina?

Back 285

- Provides stability
- Interfaces with the ECM
- Important in controlling cell behavior

Front 286

What is the 'beginning' of the ECM?

Back 286

Basal lamina

Front 287

What are the two repeating sugars in Glycosaminoglycans (GAGs)?

Back 287

- One is always an amino sugar (N-acetylglucosamine or N-acetylgalactosamine)
- Other is typically a uronic acid (glucuronic or iduronic)

Front 288

What charge are glycosaminoglycans (GAGs)? What makes them that way?

Back 288

- Highly negatively charged
- Amino sugar is usually sulfated
- Carboxyl groups projecting from them

Front 289

What is the impact of glycosaminoglycans (GAGs) being negatively charged?

Back 289

- Negative charges bind Na+
- Osmotically attracts water into matrix
- Matrix swells and occupies a lot of space/mass
- Resulting porous, hydrated, gel serves as a cushion to absorb and disperse compressive loads

Front 290

What are the four main types of glycosaminoglycans (GAGs)?

Back 290

1. Hyaluronate (not sulfated)
2. Chondroitin sulfate and dermatan sulfate
3. Heparan sulfate and heparin
4. Keratan sulfate

Front 291

What is the predominant glycosaminoglycan (GAG) in loose supporting tissues?

Back 291

Hyaluronate (hyaluronic acid, hyaluronan)

Front 292

What is the structure of the glycosaminoglycan (GAG) hyaluronate?

Back 292

- Non-sulfated
- Single disaccharide unit
- Long chains, >300 units up to 25,000 units
- Does not form covalent links to protein molecules

Front 293

What are proteoglycans formed from?

Back 293

- Sulfated glycosaminoglycan (GAG) chains (other than hyaluronate) form covalent links with a protein core
- GAGs are attached to protein core in golgi

Front 294

What kind of proteoglycans are found in cartilage and connective tissue?

Back 294

- Large multimeric complexes
- Aggregan proteoglycans are bound by 'link proteins' to a hyaluronate backbone

Front 295

What are the functions of proteoglycans?

Back 295

- Form molecular filters of variable pore size and charge density (screen and retard macromolecules)
- Contain binding sites for secreted growth factors (FGF and TGFα), proteases, and protease inhibitors (can impede function by preventing molecules from reaching destination or enhance function by concentrating them in specific location)

Front 296

What is an example of proteoglycan function in filtering?

Back 296

In kidney, heparan sulfate proteoglycan in glomerular basal lamina

Front 297

What is an example of a proteoglycan that remains attached to the cell membrane?

Back 297

Syndecan - core proteins act as transmembrane proteins and are attached to actin filaments of cytoskeleton and to collagen and fibronectin in ECM

Front 298

What is the function of syndecans (proteoglycan that is attached to the cell membrane) in fibroblasts?

Back 298

In fibroblasts, they bind FGF and present it to cell membrane FGF receptors in their vicinity

Front 299

What protein constitutes the largest percentage of protein mass in mammals? What percentage?

Back 299

Collagen (25%)

Front 300

What synthesizes and secretes collagen?

Back 300

Connective tissue fibroblasts

Front 301

What is the structure of collagen?

Back 301

- Triple helix of three α chains
- α chain sequence is usually a repeat of Gly-X-Y, where X and Y can be any AA (proline is most common X and hydroxyprolineis most common Y)
- Polymerizes to form collagen fibrils typical of Types I, II, III, and IV
- Covalent bonds formed between lysine and hydroxylysine
- Further aggregated into collagen fibers

Front 302

Collagen is secreted into ECM as what?

Back 302

Tropcollagen

Front 303

Why is vitamin C important for formation of collagen?

Back 303

- Vit. C is required for hydroxylation of proline residues
- Without it get scurvy - α chains are unable to form stable helices and tropocollagen fibers incapable of aggregating into fibrils

Front 304

What are the symptoms of scurvy? (Vit. C deficiency)

Back 304

- Collagen not made properly
- Fragile blood vessels
- Poor wound healing
- Teeth loosen in sockets

Front 305

What happens if there is excessive accumulation of collagen during wound healing?

Back 305

Elevated scar - aka keloid

Front 306

What is osteogenesis imperfecta?

Back 306

- Defect in type I collagen (fibril-forming)
- Leads to easily fractured bones

Front 307

What is chondrodysplasia?

Back 307

- Defect in type II collagen (fibril-forming)
- Results in cartilage joint deformities (and Dwarfism)

Front 308

What is Ehlers-Danlos syndrome?

Back 308

- Defect in type III collagen (fibril-forming)
- Characterized by weak skin, fragile blood vessels, and hypermobile joints
- Wide-gaping wounds

Front 309

Where are elastic fibers found?

Back 309

ECM of skin, lung, and blood vessels

Front 310

What are elastic fibers composed of?

Back 310

- Elastin - rich in glycine, lysine, and proline; covalently linked by lysine residues
- Fibrillin - elastic glycoprotein

Front 311

How are elastic fibers synthesized?

Back 311

Elastin synthesized by fibroblasts, assembled in ECM into elastic fibers consisting of an elastin core and surrounded by sheath of microfibrils composed of fibrillin

Front 312

What is Marfan syndrome?

Back 312

Mutations in fibrillin gene; patients may have ruptured aneurysms of root of aorta
- Fibrillin is important for elastic fibers in connective tissue

Front 313

How is the basal lamina linked to a cell?

Back 313

- Fibronectin and laminin are adhesive proteins that link basal lamina to integrins
- Integrins are linked intracellularly to cytoskeleton

Front 314

What are integrins important for?

Back 314

- Transmembrane proteins similar to cell receptors
- Linked to actin filaments by carboxyl ends in cytoskeleton and ECM proteins by amino ends
- Important for linking the basal lamina to the cells

Front 315

What is the structure of integrins?

Back 315

- Heterodimers composed of α and β subunits
- Carboxyl ends of α/β chains link to actin filaments (cytoskeleton)
- Amino ends bind proteins in ECM
- Different isoforms determine specificity

Front 316

How can the attachment of cells to matrix components be modulated?

Back 316

Down-regulation of the number of integrin molecules on the cell surface

Front 317

What is the structure of laminin?

Back 317

- Large glycoprotein (950,000 daltons)
- Three large polypeptide chains (α, β1, and β2)
- β chains wrap around the α chain, forming a cross like pattern of one long and three short chains
- Held together by disulfide bonds

Front 318

Where are laminins found?

Back 318

Basal lamina - forms links between cell membranes and other constituents of basal lamina

Front 319

What is the structure of fibronectin?

Back 319

- Large glycoprotein heterodimer
- Disulfide-linked
- Contains collagen, heparin, and cell (integrin) binding domains separated by flexible hinge peptides

Front 320

What is fibronectin's role in binding the basal lamina to the cell?

Back 320

- Contains cell binding site (for integrin) is an RGD (Arg-Gly-Asp) tripeptide sequence
- Fibronectin receptors on integrin within cell membrane bind to actin filaments within cytoskeleton and to fibronectin in ECM
- Fibronectin binds collagen and heparin sulfate in ECM to establish continuity

Front 321

What is the basal lamina?

Back 321

- AKA basement membrane
- Sheet-like network of ECM proteins which acts as an interface between epithelia and connective tissue
- Composed of Type IV collagen, proteoglycan perlecan heparan sulfate, and adhesive glycoproteins laminin and entactin

Front 322

What are the functions of the basal lamina?

Back 322

- Molecular filter
- Selective barrier to cells
- Scaffolding for regeneration

Front 323

What about the structure of the basal lamina makes it a good molecular filter?

Back 323

- Anionic charge of heparan sulfate proteoglycan glycosaminoglycan (GAG) chains
- Regulates movement based on charge (negatively charged molecules are repelled)

Front 324

What kind of cells does the basal lamina form a barrier to?

Back 324

Fibroblasts and endothelial cells - normally do not penetrate basal membrane and migrate among the skin epithelial cells

Front 325

How does the basal lamina influence regeneration of cells?

Back 325

Skeletal muscle fiber regeneration is orchestrated by myoblasts migrating along the inside of the basement membrane

Front 326

How is the extracellular matrix (ECM) degraded?

Back 326

- By extracellular proteases (matrix metaloproteinases and serine proteases)
- Degrade collagen, laminin, and fibronectin

Front 327

What is able to penetrate the basal lamina when it is being degraded?

Back 327

Macrophages, lymphocytes, and nerve fibers

Front 328

How does proteolysis of matrix proteins contribute to cell migration?

Back 328

- Clears a path through matrix
- Exposes cryptic sites on cleaved proteins for cell binding and/or migration
- Promotes cell detachment so cell can move
- Releases extracellular signal proteins to stimulate migration

Front 329

How is matrix degradation regulated?

Back 329

- Peptide tissue inhibitors of metalloproteaes (TIMPs)
- Serine protease inhibitors (serpins)
- Diffusion of these peptides and others in ECM is limited by binding to proteoglycans
- Secreted by cells in margins of areas of active protein degradation to protect uninvolved matrix
- Also protect cell-surface proteins required for cell adhesion and migration

Front 330

How does WBC movement relate to basal lamina?

Back 330

- WBC migrate across basal lamina of a blood vessel into a tissue
- In response to infection or injury

Front 331

How does metastasis of malignant melanoma skin epithelial cells relate to the basal lamina?

Back 331

- Usually skin epithelial cells remain attached to basal lamina (except during cell division)
- Proteolytic breaking through basal lamina allows metastases of cancer cells into blood stream

Front 332

How does angiogenesis relate to the basal lamina?

Back 332

- During angiogenesis, sprouting endothelial cells penetrate ECM by secreting hyaluronidase and plasminogen activator
- These enzymes break down basal lamina allowing new blood vessels to penetrate matrix

Front 333

What are the cellular components of connective tissue?

Back 333

- Fibroblasts (myofibroblasts)
- Adipose cells
- Leukocytes (monocytes, neutrophils, eosinophils, lymphocytes, mast cells)

Front 334

What is the most abundant and widely distributed cell in connective tissue?

Back 334

Fibroblasts

Front 335

What is the function of fibroblasts?

Back 335

Synthesis of almost all of ECM of connective tissue

Front 336

Where are fibroblasts located?

Back 336

- Close association with collagen fibers
- Lie parallel to axis of collagen fibers

Front 337

What is the structure of fibroblasts?

Back 337

- Large ovoid fibroblast nucleus
- Contains patches of marginal heterochromatin and 1 or 2 well defined nucleoli
- Prominent golgi apparatus
- Slender mitochondria
- Abundant rough ER - for manufacture and secretion of collagens and ground substance (especially during wound healing)
- No basal lamina

Front 338

How do you know that fibroblasts are active in synthesis of protein (collagen and ground substance)?

Back 338

Lots of rough ER

Front 339

What are myofibroblasts?

Back 339

- Modified fibroblasts
- Characteristics of both fibroblasts and smooth muscle cells
- Result from transdifferentiation of fibroblasts and SMCs

Front 340

How are myofibroblasts similar to fibroblasts?

Back 340

- Little or no basal lamina
- Abundant in areas of wound healing (for synthesis of collagen and ground substance)

Front 341

How are myofibroblasts similar to smooth muscle cells?

Back 341

- Contain bundles of actin filaments and dense bodies
- Allows for contraction of and shrinkage of scar tissue

Front 342

Besides from areas surrounding wound healing, where are myofibroblasts found?

Back 342

Periodontal ligament - assist in tooth eruption

Front 343

Lipids found in adipose cells are derived from what sources?

Back 343

- Dietary fat circulating in bloodstream as chylomicrons
- TGs synthesized in liver and transported in blood
- TGs synthesized from glucose within adipose cells themselves

Front 344

What kind of receptors do adipose cells have? Why are these important?

Back 344

- Insulin, glucocorticoids, growth hormone, and NE receptors
- Modulate uptake and release of fat

Front 345

What hormone is released by adipocytes? What does it do?

Back 345

Leptin - involved in regulation of appetite

Front 346

What influences fat metabolism?

Back 346

- Dietary uptake
- Energy expenditure
- Insulin (increases conversion of glucose to TG)
- NE (stimulates lipase activity)

Front 347

What are the two main types of adipose tissue?

Back 347

- White adipose tissue
- Brown adipose tissue

Front 348

What percentage of a normal male and female is from white adipose tissue?

Back 348

- Males: 20%
- Females: 25%

Front 349

What is the structure of a white adipose cell?

Back 349

- Single, large lipid droplet (unilocular)
- Thin rim of cytoplasm
- Thin basal membrane
- Heavily supplied with blood vessels (type III collagen)

Front 350

What is the structure of a brown adipose cell?

Back 350

- Multiple, small lipid droplets (multilocular)
- Abundant capillaries and mitochondria

Front 351

What are the two types of obesity?

Back 351

- Hypertrophic obesity - accumulation and storage of fat in white adipose cells (increase in size by as much as 4x)
- Hypercellular obesity - more severe, overabundance of adipocytes

Front 352

What regulates adipose mass?

Back 352

Leptin - hormone secreted by adipocytes that is involved in regulation of appetite

Front 353

How does leptin function?

Back 353

- Leptin secreted by adipocytes
- Binds to leptin receptors in appetite center of hypothalamus
- Activates SNS to release NE
- NE shifts adipose tissue from storage to mobilization and oxidation

Front 354

What happens to someone who does not produce enough leptin or an inactive form of leptin?

Back 354

- Voracious appetite
- Uncontrollable weight gain

Front 355

Where do monocytes come from and what do they mature to form?

Back 355

- Enter the connective tissue from the blood
- Mature into free (mobile) or fixed resident macrophages

Front 356

How long do macrophages live for?

Back 356

2 months

Front 357

What are the two types of macrophages?

Back 357

- Phagocytes
- Antigen presenting cells

Front 358

What are the more location specific names for macrophages?

Back 358

- Histiocytes in CT, lymphoid organs, and bone marrow
- Alveolar phagocytes in lungs
- Kupffer cells in liver
- Microglia in CNS
- Osteoclasts in bone

Front 359

What are the functions of macrophages?

Back 359

- Phagocytosis and degradation of dead cells and cellular debris
- First-line cellular defense against bacteria
- Process and present antigens to lymphocytes for antibody generation

Front 360

What are the structural characteristics of macrophages?

Back 360

- Kidney-shaped indented nucleus
- Abundant lysosomes (cytoplasm contains primary and actively digesting secondary lysosomes)
- Large juxtanuclear golgi
- Cell surface receptors for Fc portions of antibodies
- Complement peptides (bind immunoglobulins to bacteria)

Front 361

What is the purpose of complement peptides?

Back 361

- Bind immunoglobulins to surface of bacteria
- Makes bacteria susceptible to phagocytosis (aka opsinization)

Front 362

What is opsinization?

Back 362

Phagocytosis of bacteria

Front 363

When/where are neutrophils located?

Back 363

- Rare in normal CT
- Attracted to injured tissue

Front 364

What attracts neutrophils?

Back 364

Injured tissues:
- Cleavage products of complement
- Cytokines
- Bacterial lipopolysaccharide liberated during the inflammation process

Front 365

What is the function of neutrophils?

Back 365

- Phagocytosis and digestion of bacteria in areas of acute inflammation
- Form pus

Front 366

What are the structural characteristics of neutrophils?

Back 366

- Multilobulated nucleus
- Non-specific cytoplasmic granules (primary lysosomes)

Front 367

What attracts eosinophils?

Back 367

- Areas of inflammation by leukocyte chemotactic factors
- Sites of allergic inflammation

Front 368

What is the function of eosinophils?

Back 368

- Attack parasitic organisms by releasing cytotoxins to degrade membranes
- Phagocytose antibody-antigen complexes and degrade histamines to moderate the allergic reaction

Front 369

What are the structural characteristics of eosinophils?

Back 369

- Multilobulated nucleus
- Cell type-defining eosinophilic specific granules

Front 370

Where are eosinophils in high numbers?

Back 370

Regions associated with allergic reactions (nasal mucosa, lung, skin, and lamina propria of gut)

Front 371

What are the structural characteristics of lymphocytes?

Back 371

- Small dark cells
- Contain a dark round nucleus
- Thin rim of cytoplasm

Front 372

What are the principal cells of the immune system?

Back 372

Lymphocytes

Front 373

Where are lymphocytes in high numbers?

Back 373

- Lymphoid tissue
- Lamina propria of gut
- Sites of chronic inflammation

Front 374

What are plasma cells derived from?

Back 374

B Lymphocytes that have interacted with antigen and secrete antibodies

Front 375

What are the structural characteristics of plasma cells?

Back 375

- Large cells
- Round nucleus
- 'Clock face' pattern of heterochromatin
- Extensive basophilic cytoplasm of RER

Front 376

Where do mast cells come from? How long do they live?

Back 376

- Bone marrow
- Weeks to months

Front 377

What are the functions of mast cells?

Back 377

Involved in mediating inflammatory process and immediate hypersensitivity reactions

Front 378

What are the structural characteristics of mast cells?

Back 378

- Large cells
- Basophilic granules (contain heparin, histamine, neutral proteases, neutrophil and eosinophil chemotactic factors, and leukotrienes)
- Small round nucleus
- Surface receptors for immunoglobulins

Front 379

Where are mast cells prevalent?

Back 379

Connective tissue surrounding small blood vessels

Front 380

What chain of events occurs when IgE molecules bind to the Fc receptors on mast cells?

Back 380

- IgE molecules bind and are cross-linked by antigen to activate degranulation
- Histamine release increases capillary and postcapillary venule permeability
- Mucosal edema results

Front 381

What happens to patients with hay fever?

Back 381

- Suffer from effects of histamine released by mast cells of nasal mucosa
- Causes localized edema from increased permeability of small blood vessels
- Leads to feeling 'stuffed up' and hinders breathing

Front 382

What happens to patients with asthma?

Back 382

- Release of leukotrienes from mast cells in lungs
- Initiates bronchial smooth muscle contractions
- Causes difficulty breathing

Front 383

What are the types of connective tissue?

Back 383

- Mesenchymal CT
- Loose (areolar) CT
- Dense CT (Regular and Irregular)
- Reticular CT

Front 384

Where is mesenchymal CT present?

Back 384

Only in the embryo

Front 385

Which type of connective tissue is also known as embryonic CT?

Back 385

Mesenchymal CT

Front 386

What are the structural characteristics of mesenchymal CT?

Back 386

- Mesenchymal cells
- Gel-like ground substance
- Reticular fibers
- Hyaluronic acid and some fibrillar collagens

Front 387

What does mesenchymal CT give rise to?

Back 387

Loose connective tissue

Front 388

What are the structural characteristics of loose (areolar) connective tissue?

Back 388

- Loose arrangement of fibers and dispersed cells
- Cells: fibroblasts, macrophages, mast cells, and some WBCs
- Gel-like ground substance

Front 389

Where is loose (areolar) connective tissue found?

Back 389

- Under epithelia of body
- Packages organs and surrounds capillaries

Front 390

What are the functions of loose (areolar) connective tissue?

Back 390

- Wraps and cushions organs
- Holds tissues together
- Macrophages phagocytose bacteria

Front 391

How does dense connective tissue compare to loose CT?

Back 391

- Dense has a greater abundance of fibers
- Also has fewer cells

Front 392

What are the structural characteristics of Irregular Dense CT?

Back 392

- Irregularly arranged collagen fibers
- Few cells

Front 393

Where is irregular dense CT found?

Back 393

- Reticular layer of dermis of skin
- Submucosa of digestive tract
- Fibrous capsule of visceral organs and joints

Front 394

What are the functions of irregular dense CT?

Back 394

- Withstands tension in multiple directions
- Provides structural strength

Front 395

What are the structural characteristics of Regular Dense CT?

Back 395

- Coarse collagen bundles densely packed and oriented in parallel cylinders or sheets
- Few cells

Front 396

What are the functions of Regular Dense CT?

Back 396

- Withstands great tensile strength in one direction
- Attach muscles to bones or muscle, and bones to bones

Front 397

Where is regular dense CT found?

Back 397

- Tendons, most ligaments, and aponeurosis
- Cornea

Front 398

Why is the cornea transparent (normally)?

Back 398

- Contains overlapping Type I collagen fibers stacked at nearly right angles and embedded in proteoglycans (regular dense CT)
- Orderly packing makes it transparent

Front 399

Why does cornea surgery temporarily generate hazy vision?

Back 399

- Normally the collagen fibers are organized neatly and embedded in proteoglycans (regular dense CT)
- After surgery the orderliness is temporarily disrupted

Front 400

What are the structural characteristics of reticular CT?

Back 400

Network of reticular fibers (composed from collagen type III) in loose ground substance

Front 401

What is the location and function of reticular CT?

Back 401

- Supports the parenchyma of organs
- Liver, lymph nodes, spleen, and pancreas

Front 402

What is a big difference between epithelial cells and connective tissue re: intercellular space?

Back 402

- Epithelial cells have little intercellular space
- Connective tissues have lots of intercellular space

Front 403

Where are simple squamous epithelia found?

Back 403

- Lining of blood vessels (endothelium)
- Lining of body cavities (mesothelium)
- Lining of renal corpuscle

Front 404

Where are simple cuboidal epithelia found?

Back 404

- Lining of kidney tubules
- Lining of ducts of some glands
- Covering of the free surface of ovary

Front 405

Where are simple columnar epithelia found?

Back 405

- Lining of stomach, intestines, and rectum,
- Lining of uterus and oviducts
- Lining of ducts of some glands

Front 406

The oval nuclei in columnar cells are located closer to which surface of the cell?

Back 406

Basal

Front 407

Where are pseudostratified epithelia found?

Back 407

- Male reproductive tract
- Respiratory epithelium (in ciliated form)

Front 408

What are the two types of stratified squamous epithelia? How are they distinguished? Where are they found?

Back 408

- Keratinized - surface layer of dead, anucleated cells filled with keratin (skin)
- Non-keratinized - surface layer of nucleated cells, aka mucous membrane (oral cavity, esophagus, vagina, anal canal, and vocal folds

Front 409

How can the layers of the skin be distinguished on a slide?

Back 409

- Surface - dark pink - epidermis (keratinized, stratified squamous epithelium)
- Underlying connective tissue - light pink - dermis
- Separated by a jagged line

Front 410

Do non-keratinized stratified squamous cells have nuclei?

Back 410

Yes

Front 411

What is the functional advantage of having multiple cell layers in the epithelia of the skin, oral cavity, esophagus, vagina, anal canal, and vocal folds?

Back 411

Surface cells are sloughed, thereby protecting underlying tissues from friction, abrasion, and infection

Front 412

What is the functional advantage of having a keratinized (cornified) vs. nonkeratinized (non-cornified) epithelium in a given region?

Back 412

Non-keratinized epithelia are less resistant to water loss

Front 413

Where are stratified cuboidal and stratified columnar epithelia located?

Back 413

Rare but in parts of pharynx, larynx, urethra, conjunctiva, ducts of salivary, sweat, and mammary glands, and anorectal junction

Front 414

Where is transitional epithelia located?

Back 414

- Bladder
- Renal pelvis
- Ureters
- Proximal urethra

Front 415

When the bladder is distended the transitional epithelia appear as what?

Back 415

Squamous cells

Front 416

What are three examples of tissues in the body in which zonula occludens between adjacent cells is necessary for proper functioning?

Back 416

1. Intestinal epithelium - restricts food to lumen and only allows access of nutrients to bloodstream through cells
2. Vasculature of brain and spinal cord - make up blood-brain barrier
3. Urinary bladder and kidney

Front 417

What layer of skin cells are located just superficial to the basal cells at the epidermal/dermal junction?

Back 417

Stratum spinosum

Front 418

What specialization is found on the stratum spinosum?

Back 418

Spiny projections apparent as fine lines between cells that represent etensions of cytoplasm from adjacent cells linked by desmosomes

Front 419

How do desmosomes and hemidesmosomes differ functionally?

Back 419

- Desmosomes - link adjacent cells
- Hemidesmosomes - link cells to basal lamina (via intermediate filaments to transmembrane proteins)

Front 420

What proteins are involved in hemidesmosomes?

Back 420

- Transmembrane proteins - BP180 and α6β4 integrin - receptors
Basal Lamina proteins - laminin 5
- Anchoring fibrils of collagen type VII (extra linkage to ECM)

Front 421

What type of cytoskeletal proteins insert into a zonula adherens?

Back 421

Actin microfilaments

Front 422

What type of cytoskeletal proteins insert into a desmosome?

Back 422

Intermediate filaments

Front 423

In which tissues of the body would you expect to find numerous adhering junctions? Why?

Back 423

Tissues subject to mechanical stress (e.g. skin, cardiac muscle and skeletal muscle) have numerous adhering junctions to prevent tissue tearing by shear forces

Front 424

What are the implications of pemphigus vulgaris (PV) and vullous pemphigus (BP)?

Back 424

- Autoimmune disease in which patient develops antibodies against proteins of desmosome or hemidesmosome
- Patients experience blisters in response to mechanical trauma

Front 425

What is the advantage of having cells electrically coupled (e.g. cardiac muscle cells)?

Back 425

Act in synchrony

Front 426

What is the main component of the basal lamina? What is its function?

Back 426

Extracellular molecules secreted by epithelial cells to provide structural support and to serve as a barrier to materials that might pass between the epithelium and connective tissue

Front 427

What does a Periodic Acid-Schiff stain do to cells?

Back 427

Makes the acellular basement membrane appear magenta by reacting with proteoglycan-rich macromolecules concentrated in this structure

Front 428

What is the light microscope term for the layer between the basal surface of epithelial cells and their underlying CT?

Back 428

Basement membrane

Front 429

What is the electron microscope term for the layer between the basal surface of epithelial cells and their underlying CT?

Back 429

Basal lamina

Front 430

Epithelial cells on surfaces are always polarized; the side adjacent to the basement membrane is what side?

Back 430

Basal

Front 431

What is the function of cilia in the trachea?

Back 431

Remove particles in air passageways towards the oropharynx for removal by swallowing

Front 432

What is the name of cancers that come from epithelial cells?

Back 432

Carcinomas

Front 433

What are some changes that are noted in carcinomas (cancers of epithelial cells)?

Back 433

- Anaplasia - loss of polarity of nuclei
- Loss of orderly maturation of cells (esp. in squamous cells)
- Variation in size and shape of cells
- Hyperchromatism of nuclei (w/ clumping of chromatin)
- Increase in nuclear-cytoplasmic ratio

Front 434

What are the characteristics of dense regular connective tissue?

Back 434

- Purple stained, elongated nuclei are scattered among the thick pink collagen fibers
- Cytoplasm is difficult to distinguish
- Normally fibers are packed but tissue prep makes separations appear between parallel fibers

Front 435

What type of collagen predominates in dense regular CT?

Back 435

Type I

Front 436

The nuclei in dense regular CT are from what cells?

Back 436

Fibroblasts

Front 437

What are the layers of the skin?

Back 437

- Epidermis
- Papillary layer of dermis (pale pink)
- Reticular layer of dermis (dark pink, containing thick fibers)

Front 438

Why is the reticular layer of the dermis called that?

Back 438

Because the thick collagen fibers are oriented in all directions, forming a reticulum (network) although it is classified as 'dense, irregular CT' NOT reticular CT

Front 439

What type of CT encapsulates most organs?

Back 439

Dense irregular CT

Front 440

What is the advantage of having collagen fibers oriented in all directions in dense irregular CT?

Back 440

Protects from mechanical stress in multiple directions

Front 441

What is the function of the fibroblasts in dense regular and dense irregular CT?

Back 441

Synthesize, secrete, and maintain ECM

Front 442

Is epithelium or CT more cellular?

Back 442

Epithelium

Front 443

Does epithelium or CT have more ECM?

Back 443

Connective tissue

Front 444

What is found at the core of a villus? What is it called?

Back 444

Lamina propria - filled with loose connective tissue

Front 445

What is the function of the loose connective tissue in the villus?

Back 445

- Physical support for epithelium
- Metabolic support for avascular epithelium
- Support for lymphoid tissues dealing with foreign antigens from gut

Front 446

What cells are found in the loose connective tissue? Which two are identifiable and how?

Back 446

- Fibroblasts (not identifiable)
- Macrophages (not identifiable)
- Mast cells (not identifiable)
- Smooth muscle cells (not identifiable)
- Eosinophils (bright pink granules with bi-lobed nuclei)
- Lymphocytes (small intensely basophilic cells w/ little cytoplasm)

Front 447

What are the characteristics of plasma cells?

Back 447

- Mature B lymphocyte
- Eccentric nucleus (displaced to one side)
- Clock-faced arrangement (large clumps of heterochromatin regularly spaced arund inner nuclear membrane)
- Cytoplasm is basophilic and more pale in region near nucleus where Golgi is located

Front 448

Where does some of the connective tissue found in the lamina propria of the GI tract villi originate?

Back 448

Bone marrow and gets to lamina propria via the circulatory system

Front 449

Where is loose connective tissue often found?

Back 449

- Lamina propria in villi of GI tract
- Epithelia and mesothelia of pleural, pericardial, and abdominal cavities
- Supports blood vessels and nerves
- Fills spaces between other tissues

Front 450

What is the collective function of the cells in the loose connective tissue that underly epithelia of the GI tract, respiratory tract, and skin?

Back 450

First line of defense against invasion of the body by microorganisms or foreign antigenic substances

Front 451

What structure appears as thin black branching lines in loose connective tissue? as thick green lines?

Back 451

- Thin branching black lines - elastic fibers
- Thick green lines - type I collagen fibers

Front 452

What is the function of the elastic fibers in loose connective tissue?

Back 452

Distensibility and flexibility

Front 453

What two vital organs require elastic fibers for proper funtionality?

Back 453

- Blood vessels (especially elastic arteries for modifying BP)
- Lungs

Front 454

What are the empty spaces called in loose connective tissue? What is found here?

Back 454

Intersitial spaces - filled with non-fibrous ECM material (glycosaminoglycans, proteoglycans, and glycoproteins)

Front 455

What are the three components of the non-fibrous ECM material?

Back 455

- Glycosaminoglycans
- Proteoglycans
- Glycoproteins

Front 456

What is it called when there is excess watery fluid in interstitial spaces?

Back 456

Edema

Front 457

What are the two types of cells in an organ? What are they specialized for?

Back 457

- Parenchyma - functional units of organ
- Stroma - suppertive connective tissue framework

Front 458

What are the thin, black lines in reticular connective tissue? What is its function?

Back 458

- Reticular fibers
- Form supportive scaffolding for parenchyma; confer resilience to the tissues

Front 459

What type of collagen makes up reticular fibers?

Back 459

Type III

Front 460

How do Type I and Type III collagen fibers compare?

Back 460

- Reticular fibers (type III) are thinner and shorter than Type-I fibers
- Reticular fibers (type III) also branch whereas Type-I do not

Front 461

What is the major function of adipose tissue?

Back 461

Energy storage

Front 462

During conventional tissue preparation, what happens to lipid droplets?

Back 462

The lipid is extracted leaving an empty space

Front 463

Where are the nuclei and cytoplasmic organelles located in unilocular adipocytes?

Back 463

Peripherally around droplet