TOB epithelium Flashcards
Describe the term ‘peritoneal’ organs.
Peritoneal organs are covered in serosa (a layer of mesothelium, the visceral peritoneum). (Stomach, liver, colon)
Describe the term ‘retroperitoneal organ’.
Retroperitoneal organs lie outside the peritoneum, they are coveted in adventitia (loose connective)
Define epithelia
Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line the internal surfaces.
What is meant by the term simple squamous epithelia?
Simple means that the epithelia is one layer thick. With all the cells being in contact with the basement membrane. Squamous is the cell shape, its very thin and flat, with the nucleus making a bulge in the cell.
What are the main functions of squamous epithelia?
Lubrication (Peri, pleu, perit/viscera)
Gas exchange (Pulmonary alveoli)
Barrier (Bowmans Capsule)
Active transport by pinocytosis (Mesothelium and endothelium)
What is meant by the term simple cuboidal epithelia?
One cell thick. Central nuclues, as wide as they are long. Lining the ducts of most galnds.
What is meant by the term simple columnar epithelia?
One cell thick. Basal nuclei, taller than they are wide. Lining most of the GI tract
What is meant by the term pseudostratified epithelia?
One cell thick, give the appearance of being stratified because of the position of the nuclei. Line the trachea, bronchi, nasal cavity and the epididymis.
What is meant by the term stratified squamous (non-keritinized) epithelia?
more than one cell layer thick. Flattened with nuclei. Line the mouth, oesophagus, vagina.
What is meant by the term stratified squamous keratinized epithelia?
more than one cell thick, flattened with out nuclei. Epidermis of the skin and cornea of eye. (invaginated on the soles of feet so cells don’t sloughed off)
What is meant by the term stratified cuboidal epithelia?
More than one cell thick, each cell is as tall as it is wide. Line the ducts of the sweat glands.
What is meant by the term stratified columnar?
More than one cell thick, basal nuclei. Conjunctiva of the eye, lining of some large excretory ducts.
What is meant by the term transitional epithelia?
More than one cell thick. Large dome-shaped cells, which get flattened when distended. Line the bladder, renal calayces, renal pelvis, ureter, urinary bladder, proximal portion of the urethra.
What is the basement membrane?
It is the thin, flexible, acellular layer which lies between epithelial cells and the subtending connective tissue.
What is the structure and position of the basement membrane?
It consists of basal lamina which is laid down by the epithelial cells and therefore lies closest to them.
How is the thickness of the basement membrane varied?
The thickness of the basement membrane can be augmented by a variably thick layer of reticular fibrils (type III collagen) elaborated by the subtending connective tissue.
What is the function of the basement membrane?
Serves as a strong and flexible layer to which the epithelial cells can adhere. It also serves as a cellular and molecular filter.
What is a bowmans capsule?
the cup shaped end of a nephron, which encloses a knot of blood capillaries (gomerulus). It is the site of primary filtration of the blood into the kidney tubule. Simple squamous epithelia line the parietal layer of the B.C.
What is the term given to simple squamous epithelia that lines all vascular elements (arterial, venous, capillary and lymphatic)?
endothelium
Define the term mesothelium.
The simple squamous epithelia that lines the; pericardial sac, the pleural sac and the peritoneum.
What is the function of the simple cuboidal epithelium linging the collecting ducts of the kidney?
these cells partly determine the urine volume and concentration by reabsorbing urea and water. (They respond to ADH and aldosterone)
What are the functions of simple cuboidal epithelium?
Absorption and Conduit (Exoctine glands)
Absorption and secretion (kidney tubules)
Barrier/covering (ovary)
Hormone synthesis, storage and mobilisation (thyroid)
What are the functions of the simple cuboidal epithelia lining the thyroid?
lining the follicles, cells synthesise thyroxine, store it in the colloid and transport it in to the blood stream.
What are the main locations of simple columnar epithelium?
Stomach lining and gastric glands
Small intestine and colon
What are the functions of the simple columnar epithelium?
Absorption (S.I and colon, gall bladder)
Secretion (stomach lining and gastric glands, small intestine and colon)
Lubrication (s.i and colon)
Transport (oviduct)
What is the function of simple columnar epithelium in the gall bladder?
Absorb water and electrolytes from the bile produced by the liver thus reducing its volume
Where do you find straited columnar epithelia?
in part of the parotid salivary gland, the basal portion of each epithelial cell is striated. This refers to the basal membrane being infolded.
What epithelial cells line the fallopian tube?
Simple columnar, some cells are ciliated; others are non-ciliated.
What is the name given to the proein that binds adjacent membranes?
Occludin
What is the ‘zonula occludens’?
A basolateral surface modification. Occuldin binds adjacent PM tightly together in the apical portions of some epithelia. Membrane proteins cannot bypass this, allowing the cell to restrict certain proteins to its apical surface and segregate others to the lateral and basal surface.
What disrupts occudin and thereby affects the zonula occudens?
Cholera
How many microvilli on average are there per cell?
~1000
What is a Lacteal?
A dilated lympahtic capillary vessel in the small intestine which absorbs digested fats
What lines the villus of the small intestine?
Simple columnar epithlium
What epithelium lines the upper respiratory tract?
ciliated pseudostratified epithelia.
The cilia beat at 12Hz within a watery solution exuded by the epithelium
How are particles that enter the trachea swallowed?
the mucous layer that lies on top of the ciliated psuedostratifed, this mucous is secreted by the goblet cells and immobilises particles and lubricates there passage to the pharynx where they are then swallowed
What is the epididymis and what epithelia lines it?
The epididymis is a highly coiled tube that transports the sperm from the testis. pseudostratified epithelium bearing stereocilia line the ducts.
What are stereocilia?
elongated microvilli, not cilia
What are principle cells in the epididymis?
Principal cells found in the epididymis absorb fluid and secrete substances which promote sperm maturation and also phagocytose residual bodies and any degenerate sperm.
What are the functions of pseudostratifed epithelium?
Secretion and conduit (Respiratory tract, ductus deferens)
Absorption (epididymis)
Mucus secretion (respiratory tract)
Particle trapping and removal (respiratory tract)
Where do you find pseudostratifed epithelia?
Lining of the nasal cavity, trachea, bronchi
epididymis and ductus deferens
auditory tube and part of the tympanic cavity
lacrimal sac
large excretory ducts
Why are the stratified squamous epithelia that line the vagina rich in glycogen?
A substrate for lactobacilli which produce lactic acid and thereby maintain a suitably low pH
What happens to the epithelial cells in the vagina in response to lack of hormonal stimulation?
They atrophy (pre-puberty and menopause)
What epithelia lines the epiglottis?
pseudostratified on one side and stratified squamous non-keratinized epithelium lines the other. (elastic cartilage inbetween).
What are the functions of stratified squamous (non-k) epithelia?
protection against abrasion (all sites)
Reduces water loss but remains moist (all sites)
What are the functions of stratified squamous keratinized epithelium?
Protection against abrasion and physical trauma
Prevents water loss
prevents ingress of microbes
Shields against UV light damage
What are the functions of transitional epethelium?
Distensibility
Protection of underlying tissues from toxic chemicals
Why does the rate of renewal of different epithelia vary? What can accelerate renewel?
turnover differs depending upon location and function. The time frame for each type of epithelium remains constant unless injury leads to acceleration.
Whats the renewel rate for skin epithelia?
approx 28 days
What is the renewel rate of cells lining the small intestine?
Replaced by regenerative cells in the base of the crypts every 4 to 6 days
What are microvilli?
Apical extensions which greatly increase the surface area for selective absorption of intestinal contents
What are cilia?
elongated, motile, plasmalemma- covered extensions of the cytoplasm that move material alone the cell surface
Cilia structure
9 pairs of peripheral doublets and two single centrally placed microtubles (singlets). nexin linking protein joins the doublets. Dyenin arms are present on each microtuble doublet, these have ATPase activty.
radial spoke connects doublets to central sheet composed of elastin.
