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51 Cards in this Set

  • Front
  • Back
Types of Connective Tissues (6)
1) loosely organized embryonic CT is called Mesenchyme
2) Connective tissue proper
– epithelia, nerves and muscles rest on or are ensheathed in it
forms tendons, ligaments, organ capsules

3) Adipose tissue – fat
4) Cartilage
5) Bone
6) Blood & Bone Marrow
CT's main constituent and its 3 parts
Extracellular Matrix (ECM), which is made up of:
1. Ground substance (proteoglycans, glycoproteins)
2. Fibers – collagen, reticular, elastic
3. Tissue fluid – derived from blood

*CT is relatively ACELLULAR
CT Proper's principle cells, what do they produce, part of what population
Produce ECM components
Are part of the Resident Population of cells, meaning they are produced locally and remain there
Ground Substance - function, formed by what 2 classes of components
-Acts as a lubricant and a barrier to the penetration of particles such as bacteria
Formed by:
1) Proteoglycans
2) Glycoproteins
What do proteoglycans consist of?
-Protein core with many covalently attached glycosaminoglycans (GAGs), which are linear polysacharrides formed by repeating disaccharide units.
Types of GAG's (5)
1) Hyaluronic Acid - found in loose CT, not attached to protein; often found as a free polysaccharide that attaches to other proteoglycan molecules to form proteoglycan aggregates.
2) chondroitin Sulfate
3) dermatan sulfate
4) keratan sulfate
5) heparan sulfate

#'s 2-5 are covalently attached to a protein core unlike #1
Polarity of proteoglycans, what this polarity leads to, and what proteoglycans and their GAGs are synthesized and secreted by
-Proteoglycans are extremely hydrophilic (negatively charged) which allows them to contribute to the gel-like quality of the ECM, which helps to Cushion Compressive Forces and Limit the Spread of Bacteria.
- Synthesized and secreted by Fibroblasts w/ the protein portion synthesized in the RER of the fibroblats. GAG formation begins here and is completed in Golgi
Proteoglycan turnover and related genetic defects
-Occurs when lysosomal hydrolases derived from CT cells catabolize proteoglycans during growth and development

-Genetic defects in hydrolases cause fatal childhood syndromes (Hurler’s and Hunter’s syndromes)
- Accumulation of
partially digested
proteoglycans in skull, face, brain
What do structural (adhesive) glycoproteins consist of and what is their main function? What are two of the main structural glycoproteins?
-A protein core to which branched carbohydrates are attached; here the protein is the predominant portion of the molecule.
-Responsible for linking the components of the ECM to each other and to cells
2 Main ones:
Fibronectin - synthesized by what and function
– synthesized by fibroblasts and some epithelium
- binds collagen and proteoglycans to form network in ECM; also binds to cells via integrins
Laminin - part of what, and function
-part of epithelial basal lamina
- binds to proteoglycans, type IV collagen, and epithelial cells via integrins
Integrins are what kind of proteins that allow cells to do what
-Integrins are the transmembrane
proteins that link cells to glycoproteins
-Bind with low affinity to collagen IV, fibronectin, laminin
-Allows proper epithelial cell orientation (polarity)
-Fibroblasts have integrins too
2nd component of ECM - FIBERS - assembled mainly from what 2 proteins and what are the three main types of CT fibers?
-Assembled mainly from the proteins Collagen and Elastin
3 types:
1) Collagen Fibers
2) Elastin Fibers
3) Reticular Fibers (Type III Collagen)
3 Main types of Collagen
Type I – Dermis (skin), tendons, ligaments, organ capsules, bone, teeth
- Flexible, great tensile strength

Type III – Reticular fibers
- form delicate meshwork to support cells in lymphoid & glandular organs (lymph nodes, spleen, liver)
- in reticular lamina of basement membranes
-usually co-localized w/ Type I

Type IV – structural network of epithelial basal lamina (lamina densa)
- does not form fibrils
Biosynthesis occurs in what cell types? (6)
Epithelial cells
Muscle Cells
First 2 steps of collagen biosythesis
1) Polypeptide alpha chains are synthesized on polyribosomes on RER. These chains are called PREPROCOLLAGEN b/c they have a Signal Peptide on them that allows the chains to be inserted into the RER cisternae. They also have Registration Peptides on both ends of the chains to ensure that the alpha chains assemble correctly to form fibrils.
2) Within the RER cisternae, the signal peptide is cleaved, forming PROCOLLAGEN
Last 2 steps of collagen biosythesis
3) Golgi packages the procollagen molecules into secretory vesicles
4) Released by cells via exocytosis. Outisde the cell, the proteases called Procollagen Peptidases cleave the registration peptides, forming TROPOCOLLAGEN. These assemble into Collagen Fibrils. Type I and III fibrils will assemble to form fibers
The orientation of the tropocollagen molecules within a fibril makes them...
Birefringent - there is a characteristic, distinct CROSSBANDING visible using a polarizing microscope
Errors in collagen synthesis lead to diseases (3)
1) Ehlers-Danlos syndromes – genetic defects in procollagen or tropocollagen synthesis
- Hyperextensible skin, hypermobile joints, hernias, aortic or intestinal rupture, skeletal deformities, poor wound healing

2)Osteogenesis imperfecta – genetic defect in Type I collagen production
- Brittle bones, deformities, thin skin

3) Scurvy – lack of dietary Vitamin C (co-factor for proline hydroxylase during a-chain synthesis)
- gum ulcerations, hemorrhages
Errors in collagen degradation (turnover)
-Degradation of collagen (via Collagenases) occurs normally growth, remodeling & tissue repair. B/c of increased collagen synthesis and decreased collagen degradation, diseases like...

Progressive Systemic Sclerosis may occur with error in collagen turnover
– May be autoimmune disease
- Collagen accumulates in skin, internal organs due to inadequate degradation and increased collagen synthesis
Reticular fibers - composed of, present where, form what, function, selectively stained b/c?
-composed of small groups of type III collagen fibrils (20 - 30 nm diameter)
-Present in reticular lamina of basement membranes
-Form supporting meshworks (stroma) around fat, muscle, nerve cells
-Support for cells of liver, lymph nodes, spleen
-Their flexibility of these meshworks allows for change in volume or form
-Selectively stained b/c of their ability to absorb silver (Argyrophilia)
Elastic Fibers - contain what 2 things, structure, present where/most abundant where
-Are tissues that contain Elastic Fibers or Elastic Lamellae.
-easily stretched, return to normal length due to content of elastin
- most abundant in respiratory system, elastic ligaments; elastin sheets
-present in larger blood vessels
What makes up elastic fibers and elastic lamellae
-Contain bundles of thin microfibrils that are composed of the large glycoprotein FIBRILLIN, which are encased by the protein ELASTIN
-The concentric layers of ELASTIC LAMELLAE that are present in blood vessels consist of fenestrated sheets of elastin protein; they do not contain fibrillin.
What is elastin produced by (2)? how is it made (in simple terms, one step), and what 2 unusual amino acids does it contain and their function
-Secreted as PROELASTIN and then develops into elastin (similar pathway to that of collagen)
-Contains Desmosine and Isodesmosine whose ability to form crosslinks allows elastin molecules to bind to each other.
Marfan Syndrome - what happens in it
Defective fibrillin gene expression --> deficiency of fibrillin microfibrils --> destruction of elastic fibers and elastic lamellae --> thus the elastic lamellae of aorta not well attached to smooth muscle cells by fibrillin --> aortic aneurysm and dissection (rupture) due to degeneration
What is Tissue Fluid derived from and what does it contain (2)
- Derived from capillaries of CT
-Contains ions, low molecular
weight proteins
Two Common causes of Edema formation
1) Injury
a)Vasodilation of arterioles
(via low O2 tension) increases capillary blood flow
b) Inflammatory cells produce
agents that increase capillary permeability (e.g.histamine)

2) Venous obstruction or
decreased venous blood flow
(e.g. congestive heart failure)
2 General Categories of CT Proper
1) Loose (areolar) – predominance of ground substance and cellular elements over fibrous elements

2) Dense – predominance of fibers over cells
a)Dense irregular – fiber bundles not preferentially oriented (dermis of skin)
b) Dense regular – fiber bundles arranged in a definite pattern – parallel collagen bundles, rows of fibroblasts (tendons, ligaments, cornea)
Fixed/Resident Cells in Loose CT
3)Mast cells
Fibroblasts - function and may differentiate into
-Synthesize and secrete all components of ECM.
-May differentiate into MYOFIBROBLASTS during wound contraction and healing
Macrophages - differentiate from what cell, function, 2 special organelles found inside them, what happens when the encounter large foreign bodies
-Monocytes enter the CT and differentiate into Macrophages, which may then proliferate locally
-Job is to phagocytize, either as a defense activity or as a clean up operation. Macrophage
secretion products
during infection.
Can also present antigens to
lymphocytes to initiate an immune response
-Phagocytic vacuoles and lysosomes
-when they encounter large foreign bodies, they fuse to form large cells with up to 100 nuclei called Foreign Body Giant Cells
Mast Cells (metachromatic) - their basophilic granules contain chemical mediators of inflammation (2) and mediators of what other type of reaction
-Histamine - causes smooth muscle contraction and increases capillary dilation and permeability, resulting in edema.
-Heparin - blood anticoagulant
-Mediators of the immediate hypersensitivity reaction (Anaphylaxis)

*Mast cells are numerous in the CT of skin and organ capsules
What other things are found in mast cell granules?
Leukotrienes - produce slow contractions of smooth muscle

Eosinophil Chemotactic Factor (ECF) and Neutrophil Chemotactic Factor (NCF) attract blood eosinophils and neutrophils to the site.
Wandering population of cells do what and consist of what cells (6)
Migrate into CT from blood in response to specific stimuli.

1) Plasma Cells
-Derived from B lymphocytes
that have been stimulated by
a specific antigen (usually a pathogen)
- Production of
antibodies against

White blood cells:
2) Lymphocytes
3) Neutrophils
4) Eosinophils
5) Basophils
6) Monocytes
5 Major Functions of CT
1. Structural support for epithelial, muscle, nervous tissue cells

2. Defense – cells regulate inflammatory processes
- ECM gel inhibits spread of bacteria

3. Repair – granulation tissue formed by fibroblasts, blood vessels, macrophages
- scar tissue
- inhibited by hormones such as cortisol

4. Transport of nutrients from blood vessels to cells and waste products from cells to blood

5. Storage of water, electrolytes, plasma proteins and lipids (adipose tissue)
Adipose Tissue - general info
Specialized CT for: storage of triglycerides
shock absorber (padding)
limitation of movement

Very vascular; adipocytes secrete and are surrounded by
External Lamina and collagen (reticular) fibers
Two types of adipocytes
Unilocular Adipocytes and Multilocular
Unilocular Adipocytes
-Characteristic cell of White Adipose Tissue.
-Characteristic Signet Ring
-Primary Energy Storage Compartment of the Mammal
-Act as mechanical shock absorbers
Adipose tissue stores what
Adipose tissue is an Energy Storage Organ - Triglycerides are stored as a large droplet in the cytoplasm
Storage in unilocular adipocytes
Triglycerides in the blood are hydrolyzed by endothelial Lipoprotein Lipase to form free fatty acids and glycerol.
Insulin increases glucose uptake and glycolysis in fat cells.
Lipolysis - what hormones activate Lipase, and what is Lipase's job, Insulin's role, and what happens during starvation
Lypolytic hormones (ACTH, epinephrine, glucagon) activate Hormone-Sensitive Lipase, which hydrolyzes the triglycerides to form glycerol and FFAs.

Insulin blocks the activity of hormone-sensitive lipase.
During starvation or cold exposure, the sympathetic nervous system releases Norepinephrine which causes triglyceride hydrolysis.
Besides being an energy storage organ, what type of organ is adipose tissue and how?
-Fat coordinates how, when, and where the body's energy supply is stored and how and when it is mobilized
Increased amounts of fat (obesity) produce
An increase in Leptin
A decrease in Adiponectin
An increase in Resistin
An increase in Leptin causes
acts on hypothalamus to decrease appetite and increases metabolic rate.
A decrease in Adiponectin causes
increases insulin sensitivity in the liver, causing it to decrease gluconeogenesis in the liver and causing muscle to "burn" glucose
An increase in Resistin causes
causes Decreased Sensitivity to Insulin, which results in Type II diabetes.
Fat also produces what else that affect the immune system and its inflammatory response
Produces cytokines that affect the immune system to increase immune and inflammatory responses
What does fat do in terms of blood clots and blood vessels and in terms of reproduction
It influences when blood clots and when blood vessels constrict.
Increase in fat --> increase in Angiotensin --> increase in blood pressure

Fat tells body when it can reproduce and when it must wait for more favorable conditions:
Decrease in fat --> decrease in leptin and decrease in estrogen --> exercise-induced amenorrhea (absence of menstruation)
Multilocular Adipocytes - characterized by what type of adipose tissue, tissue's function
-Characteristic of Brown Adipose Tissue
-Functions as a heat production organ in which the energy stored in the fatty acids is transduced into heat which warms the blood passing through adjacent capillaries.
What do the many mitochondria in brown adipose tissue contain and what does it do
-Contain a unique Uncoupling Protein (UCP-1) that uncouples the oxidation of fatty acids from the production of ATP, allowing the energy produced by oxidation to be used as heat.

*Brown fat utilizes its on FFA's from its own triglycerides to produce heat, the FFA's are not released into bloodstream like they are in white fat.
Brown fat found prominently where, what is thermogenesis stimulated by?
during infancy when heat production is most necessary.

Thermogenesis in brown fat is stimulated by the Sympathetic Nervous Sys. (norepinephrine)