Tissues Of The Body

Front 1

State the relationship between milli-micro and nanometers.

Back 1

1m
1mm-3
1microm-6
1nanometre -9
( most human cells are 10-20 micrometres, red blood cells are 7.2micrometres so that they can squeeze through capilaries)

Front 2

State the meaning of the term tissue.

Back 2

A collection of cells which are specialised to perform a specific function.

Front 3

Explain the value of histology in diagnosis.

Back 3

Histology provides the final proof of diagnosis along with biopsy. It is the gold standard of diagnosis.

Front 4

Describe common biopsy techniques giving examples of tissues which can be sampled by each method.

Back 4

Biopsy is the removal of a small piece of tissue from part of an organ or part of the body for microscopical examination.
methods:
Curretage - ( spoon shaped knife) - endometrial lining
Smear - cervix, buccal cavity
Needle - breast, brain, kidney
Direct incision - skin, mouth, larynx
Transvascular - heart, liver
Endoscope - Lungs, GI tract, bladder

Front 5

Explain why tissues need to be fixed and state which fixatives are usually used.

Back 5

Glutaraldehyde and formaldehyde are usual fixatives and form covalent cross links with free amino acids in tissue cells. Tissues need to be fixed to prevent autolysis ( break down by its own enzymes) and putrefacation (slow decay by bacteria followed by offensive odour).

Front 6

Describe how how tissue processing can lead to the formation of shrinkage artefacts and what could account for seeing many gaps within a sample.

Back 6

The dehydration process of fixation can cause shrinkage artefacts along lines of weakness. The gaps could have been adipocytes where the fatty acids where dissolved by xylene during fixation.

Front 7

Discuss the value of histological staining and state the components of tissue stained by PAS, haematoxylin and eosin and others.

Back 7

Histological staining is important to be able to differentiate between different layers of the tissue as they stain different colours. Before staining the biospsy must be rehydrated as the stains are water soluble. Xylene is added to remove the wax ( which also dissolves fat molecules) and is then hydrated by alcohol.
PAS - periodic acid shiff stains carbohydrates and glycoproteins MAGENTA.
Haematoxylin is a basic stain which stains acid components such as nucleus, mucus, cartilage and some proteins(basophillic) BLUE.
Eosin in an acidic stain which stains basic components such as RBCs and most cytoplasmic proteins PINK.
Weigerts elastin stains elastic fibres BLACK.
Elastic van geison - stains collagen PINK, elastic fibres BLUE/BLACK, muscle YELLOW

Front 8

Outline the advantages conferred by phase contrast, dark field, fluorescence and confocal light microscopy.

Back 8

Phast contrast - particularly useful for enhancing the image of unstained cells ( don't have to kill cells by staining - still active)
Dark field - Image formed from scattered light with a dark background. Used for routine detection of syphilis and malaria.
Confocal - Illumination, achieved by scanning one or more focused beams of light across a thick, fluorescently labelled specimen, eliminates ' out of focus flare'. Optical imaging technique - non invasive.
Fluorescent - UV radiation is often used as the incident radiation and fluorochrome-conjugated monoclonal antibodies as the stain - used to see individual structures and components of the cell.

Front 9

Define the term 'limit of resolution'.

Back 9

The minimum distance needed to be able to distinguish between two objects.

Front 10

Explain why electron microscopes are capable of finer resolution than light microscopes

Back 10

limit of resolution is directly proportional to wavelength. Electrons have a smaller wavelength than light and so electron microscropes have smaller limits of resolution, 0.002nm compared to 200 nm in light microscrope.

Front 11

Draw a simplified diagram of a cell, clearly labelling those ultrastructural components common to eukaryotic animal cells.

Back 11

must include:
- nucleus
- nuclear membrane
- nucleolus
- chromatin
- nuclear pore
- endoplasmic reticulum (rough and smooth)
- golgi apparatus
- lysosomes
- ribosomes
- mitochondria
- plasma cell membrane

Front 12

Describe the structure and function of membranes (bilipid) and plasmamembrane (plasmalemma).

Back 12

Amphipathic- both hydrophilic and hydrophobic
selectively permeable barrier, signal transduction, intercellular recognition and adhesion.

Front 13

Describe the structure and function of the glycocalyx.

Back 13

Made up of oligosaccharides (dextrins- small polymers) and polysaccharides, used as receptors.

Front 14

Describe the structure and function of the nucleus and explain the difference between heterochromatin and euchromatin.

Back 14

The nucleus contains DNA, nucleoproteins and RNA. Chromatin is DNA and associated nucleoproteins eg histones. euchromatin (eg barr bodies) is electon dense and is not active in RNA synthesis (not being transcribed) - inactive cells have small nuclei and form the X chromomes present in mitosis. heterochromatin is uncoiled chromatin and is active in RNA synthesis. Active cells habe large nuclei with heterochromatin dispersed throughout. Nucleus not found in eythrocytes, lens fibre cells.

Front 15

Describe the structure and function of the nucleolus.

Back 15

The nucleolus comprises of one or more electron dense structures which are more prominent in active cells. The nucleolus is a region of the nucleus where rRNA is transcribed and is the site of assembly of the small and large ribosomal subunits which enter the cytosol individually. Nucleoli disappear during cell division.

Front 16

Describe the structure and function of the nuclear envelope.

Back 16

A double membrane consisting of nuclear pores which surrounds the nucleus. It is surrounded by intermediate filaments and is continuous with RER.

Front 17

Describe the structure and function of RER.

Back 17

Rough endoplasmic reticulum is comprised of interconnecting membranes, vesicles and cisternae (flattened sacs with lumen). It has receptors on it's surface for ribosomes to bind to, proteins which are processed here are usually destined for the plasma membrane, lysosomes, golgi/ER or secretion. Proteins are processed in RER before being released to golgi apparatus.

Front 18

Describe the structure and function of ribosomes.

Back 18

Ribosomes are made up of a large subunit and a small subunit ( 70s -eukaryotic, 80s- prokaryote). They are used in translation and or either attached to ER or free in cytoplasm. If attached to ER the proteins made are usually destined for cell membrane, cell exterior or lysosomes. If free in cytoplasm, the proteins are usually for cytosol.

Front 19

Describe the structure and function of SER.

Back 19

Smooth endoplasmic reticulum has less flattened cisternae compared to RER. It is not associated with ribosomes. Its functions are lipid synthesis eg steroid (anti-inflammatory) production ( cholesterol) and intracellular transport.

Front 20

Decribe the structure and function of golgi apparatus.

Back 20

Saucer shaped sacks of cisternae.
cis --> trans
convex -> concave
They sort, concentrate, package and modify proteins from RER and form secretory vesicles or lysosomes.

Front 21

Describe the structure and function of lysosomes.

Back 21

Secreted from golgi apparatus. They contain digestive enzymes pH 5. Membrane is highly glycosylated for protection from these enzymes which digest macromolecules by phagoctosis. Primary lysosome: enzyme content. Secondary lysome: contents degraded and macromolecule is phagocytosed.

Front 22

Describe the structure and function of mitochondria.

Back 22

Double membrane organelle. Inner membrane folded to form cristae- increase surface area. Site of ATP synthesis by oxidative phosphorylation. Contains own DNA - maternal lineage.

Front 23

Describe the structure and function of peroxisomes.

Back 23

Found in liver and kidney cells and detoxify molecules eg alcohol.

Front 24

Describe the structure and function of the cytoskeleton.

Back 24

-Maintains and/or changes shape
- structural support
- movement of organelles
-locomotor mechanism
- contractility eg muscle cells
-3 main types. intermediate filaments, microfilaments and microtubules

Front 25

Describe the structure and function of microfilaments.

Back 25

- 5nm diamerer
- 2 strings of actin twisted together
- associated with ATP
- can assemble and dissociate (dynamic) - sliding filament theory
- microvilli have a core of actin filaments which allow them to maintain their shape

Front 26

Describe the structure and function of intermediate filaments.

Back 26

- not dynamic
- 10-12nm diameter
- Common in nerver and neuroglial cells
- common in epithelial cells -> cytokeratin
- form tough supporting meshwork in cytoplasm (outside of nucleus)
- anchored to plasma membrane at strong intracellular junctions (desmosomes)

Front 27

Describe the structure and function of microtubules.

Back 27

- 13 alpha and beta tubulin subunits polymerise to form wall of the hollow mircrotubule
- originate from centrosome - next to nucleus, collection of centrioles
- found in site where structures in cells are moved eg nerve fibres, cilia and flagella
- attachment proteins( dynein and kinesin) can attach to organelles and move them along the microtubules eg movement of chromosomes along mitotic spindle.

Front 28

Define epithelia.

Back 28

Sheets of contiguous cells of varied embryonic origin, that cover the surface of the body and line the internal surfaces

Front 29

Explain the position, structure, and function of the basement membrane.

Back 29

position: Between epithelial cells and subtending connective tissue
structure: thin and flexible layer comprised of 2 regions: basal lamina and lamina reticularis
function: cellular and molecular filter and a strong surface for epithelial cells to adhere to.

Front 30

Describe the ways in which epithelia are clasified, explaining what is meant by the classification.

Back 30

simple: 1 layer of cells, all cells touching basement membrane.
stratified: more that 1 layer of cells, classified on type of most superficial layer.
pseudostratified: simple epithelia as all cells touch basement membrane but looks stratified, not all cells reach surface.

Front 31

List the types of simple epithelia, giving functions and positions.

Back 31

squamous: flattened cells
Position: endothelium (blood and lymphatic vessels), mesothelium (lining body cavities-peritoneum, pericardium,pleural sac), alveoli, glomerulus.
Function: Lubrication( reduce friction), gaseous exchange, active transport, barrier, lining.
Cuboidal: central nucleus
Position: Lining ducts of most glands, thyroid follicles, proximal kidney tubules.
Function: Absorbtion, synthesis, storage, secretion.
Columnar: basal nucleus
Position: Much of GI tract (large intestine), jejunum, falopian tubes, salivary glands, uterus.
Function: Transport, absorption, lubrication, secretion
Pseudostratified: simple but looks stratified, all cells touch basement membrane
Pseudostratified cilliated columnar - upper respiratory tract ( nasal cavity, trachea, bronchi), testes,
Function: secretion - mucus, particle trapping and removal, absorption.

Front 32

List the types of stratified epithelia and give their positions and functions.

Back 32

stratified squamous - thickest epithelia, protection, some keratinised for more protection.
squamous non-keratinised:
Position: oral cavity, oesophagus, vagina
Function: protection against abrasion, reduce water loss, retain moisture.
Stratified squamous keratinised - keratin at surface of layer, dead epithelial cells - more protection.
Position: skin
Function: Prevent water loss, protection against abrasion and physical trauma, prevents invasion by microbes, shields against UV rays.
stratified cuboidal: very rare.
Position: glandular ducts of sweat glands, some ducts of salivary glands and in ducts of mamary glands.
Function: in sweat glands, the cells reabsorb sodium ions so that sweat is hyotonic with respect to plasma, microvilli may assist in reabsorption. Protection.
Stratified columnar: rare
Position: some parts of salivary and mammary glands, pharynx, larynx & male urethra. superficial cells- columnar, underlying cells are polyhedral.
Function: secretion and protection.
Transitional: Superficial layer rounded when relaxed, flattened when distended.
Postion: urinary passages
Function: distensibility, osmotic barriers between urine and cells of lamina propria - protection against toxins.

Front 33

Describe the layers of the epidermis: the stratified squamous keratinized epithelium.

Back 33

- stratum basale, single layer of cuboidal epithelial cells attached to the basal lamina.
- stratum spinosum, several layers of irregular polyhedral cells
- stratum granulosum, layer of flattened squamous epithelial cells- (keratinocytes)which contain keratohyalin. These cells begin to cornify( become heavily keratinized-dead).
- stratum corneum - numerous layers of dead. flattened, keratinized cells- no nucelus, thickened plasmalemma ( horny layer), particularly thick on palms and soles.

Front 34

Explain the reasons for the different rates of renewal of each type of epithelium.

Back 34

Renewal rates are different depending on location and function of cells.
Stratified squamous keratinized epithelium- 28days
Small intestine simple columnar - 4-6 days

Front 35

Describe how stratified epithelia are classified.

Back 35

Stratified epithelia are made up of more than one layer of cells. The type of epithelia it is depends on the superficial cell layer eg cuboidal, columnar, squamous keratinized or non keratinzed, transitional. Only the basal layer of cells is in contact with the basement membrane.

Front 36

Describe how the structure of cilia is related to its function.

Back 36

Cilia are specialised projections of the epithelial plasma membrane. They contain a core of microtubules (cytoskeleton) arranged in 9+2 structure ( all in pairs, one pair in the middle, the other pairs arranged around). Cilia beats in a synchronous fashion to propel material across the cell surface. Found in respiratory tract (pseudostratified ciliated columnar epithelium) to propel particles of dust and bacteria, trapped in mucus, out of the airways. Also found in fallopian tubes ( pseudostratified ciliated columnar) to move the fluid contains ovum towards uterus for implantation. Peristaltic contractions of smooth muscle also assist. Fluid is secreted by non ciliated simple columnar epithelial cells, interspersed with the ciliated cells.

Front 37

Describe how the structure of microvilli is related to its function.

Back 37

microvilli = brush border. Microvilli are sites of increased cell surface area for increased absorption. They do not beat in rhymic waves. Their shape is maintained by microfilaments of actin (cytoskeleton) Stains strongly magenta with PAS due to carbohydrates of dense, protective glycocalyx on membrane of microvilli. Found in small intestine and on simple cuboidal epithelial cells of proximal convoluted tubules of kidney.

Front 38

Describe how the structure of stereocilia are related to its function.

Back 38

Stereocilia are not cilia, but elongated microvilli which are not motile. They are found on the pseudostratified columnar epithelium lining the tubules of the epididymis (7m long). The sterocilia extend into the lumen of the epitdymis and are believed to absorb excess fluid from the lumen.

Front 39

Describe the position and structure of the mucous membrane.

Back 39

Position: lines internal tubes which open to exterior such as: urinary tract. GI (alimentary) tract and respiratory tract.
Structure: 3 layers of mucous membrane: epithelium ( type depends on location)- secrete mucus into lumen, lamina propria - (dense, irregular connective tissue), muscularis mucosa - layer of smooth muscle.

Front 40

Describe the position and structure of the serous membrane.

Back 40

Position: lines closed body cavites (which are not open to exterior) and envelops the viscera (internal organs).
- peritoneal sac envelops the adominal organs
- percardial sac envelops the heart
- pleural sac envelops the lungs
Structure:
- simple squamous epithelium - secretes a watery, lubricating fluid
- connective tissue layer - attaches epithelium to other tissues and carries nerves and blood vessels
- the outer wall - parietal serosa
- the inner wall - visceral serosa
Function - to secrete watery lubricating fluid to reduce friction of movement for the structures they surround

Front 41

Describe the 4 layers making up the wall of the alimentary canal.

Back 41

MUCOSA - epithelium, lamina propria, muscularis mucosae (mobility of mucosa- 2 thin smooth muscle layers)
SUBMUCOSA - connective tissue provides neural, vascular and lymphatic supply to mucosa. May contain glands.
MUSCULARIS EXTERNA - usually 2 layers: inner circular layer, outer longitudinal smooth muscl layer. Control peristalsis - circular muscles reduce diameter of the lumen and longitudinal muscles contract to propel food in right direction.
SEROSA OR ADVENTITIA
serosa is connective tissue surrounded by mesothelium and is present if organ has a mesentery.
Adventitia is an outer CT layer and is present if the region of gut is retroperitoneal

Front 42

List the special modifications of walls of stomach, jejunum, colon and oesophagus.

Back 42

oesophagus: stratified squamous non-keratinized epithelium for protection against abrasion.
Stomach: has a 3rd smooth muscle layer in muscularis externa, middle layer: oblique. Also has pronounced folds - rugae.
Jejunum: plical circulares - circular folds of mucosa and submucosa
Colon: has many crypts of lieburkuhn -intestinal glands.

Front 43

What are peyers patches and where are they found?

Back 43

Peyers patches are agregations of lymphocytes and are found in lamina propria of some tissues eg large intestine (colon)

Front 44

What are the 2 different portions of the respiratory system? describe which parts of the respiratory system belong to each portion and list the epithelium that is found at each part.

Back 44

Conducting portion: nasal cavity-> bronchioles
- nasal cavity to bronchi are pseudostratified cililated columnar
- trachea - C shaped hyaline cartilage ring
- bronchus - cresent shaped cartilage (support - keep lumen open)
Respiratory portion: Bronchioles -> alveoli
bronchioles- simple ciliated columnar -> cuboidal, no cartilage-lumen kept open by surrounding alveoli
alveoli - simple squamous, some are cuboidal which secrete surfactant.

Front 45

Describe the differences and similarities of the walls of the ureter, bladder and urethra.

Back 45

Ureter - transitional epithelium
- lamina propria contains fibroelastic connective tissue
- muscularis externa has circular smooth muscle layer only.
Bladder - transitional epithelium
- lamina propria contains smooth muscle
- muscularis externae contains 3 smooth muscle layers - longitudinal, circular, longitudinal
Urethra - transitional in women, stratified columnar in males
- stellate shaped lumen --> ovoid when urine runs through

Front 46

Discuss how structure of GI mucosa relates to its function.

Back 46

Oesophagus has stratified squamous non keratinized epithelium to protect against abrasion. Lamina propria of colon has peyers patches - aggregation of lymphocytes to fight bacteria. Stomach has 3 smooth muscle layers (Muscularis externae) - peristalsis. Stomach has rugae - folds of mucosa and submucosa to increase surface area to provide expansion when food arrives.

Front 47

Discuss how the structure of respiratory and urinary mucosa, relate to their functions.

Back 47

Respiratory- pseudostratified ciliated columnar epithelium - wafting of dust particles and bacteria trapped mucus out of the tract. Goblet cells within the epithelia to secrete mucus. Bronchioles- simple columnar- diffusion and support. Trachea - C shaped cartilage ring for structural support, keep open lumen. Alveoli - simple squamous for gaseous exchange, some cuboidal to synthesise and secrete surfactant.
Urinary - transitional epithelium- disensibility, protection from toxins (impermeable to urine due to thick plasma membrane and tight intercellular junctions)