Term
What are the 4 functions of epithelial tissue |
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Definition
1.provide physical protection 2.control permeability and allow absorption/secretion 3.provide sensation 4.produce specialised secretions |
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Term
How does epithelial tissue produce specialised secretions |
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Definition
1.release their secretions onto the surface of the epithelium (to provide physical protection/temperature regulation) 2.release them into surrounding interstitial fluid and blood (to act as chemical messengers |
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Term
How is epithelia classified |
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Definition
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Term
Describe squamous epithelia |
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Definition
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Term
Describe simple squamous epithelia |
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Definition
Single layer Used in absorption and secretion |
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Term
Describe stratified squamous epithelia |
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Definition
Many layers Protects against attacks Keratin protein adds strength and water resistance |
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Term
Describe cuboidal epithelia |
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Definition
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Term
Describe simple cuboidal epithelia |
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Definition
single layer secretion and absorption |
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Term
Describe stratified cuboidal epithelia |
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Definition
Many layers Sweat ducts and ammory ducts |
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Term
Describe columnar epithelia |
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Definition
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Term
Describe simple columnar epithelia |
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Definition
Single layer Protection, secretion and absorption |
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Term
Describe stratified columnar epithelia |
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Definition
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Term
Epithelial cells are polarised, what does this mean? |
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Definition
they can target proteins to discrete cell domains |
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Term
What is the role of a tight junction |
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Definition
to seal the gap between epithelial cells prevents diffusion of plasma membrane proteins (eg receptors/channels) between apical and basolateral domains |
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Term
What is the role of an adherens junction |
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Definition
connect actin filament bundle in one cell with that in the next cell |
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Term
What is the role of a desmosome |
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Definition
connects intermediate filaments in on cell to those in the next cell |
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Term
What is the role of gap junctions |
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Definition
allows the passage of small water soluble molecules from cell to cell |
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Term
How can apical surfaces be specialised |
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Definition
Microvilli: increase membrane surface area by 20/30 fold. Especially involved in bulk absorption or secretion. (motile) Cilia: maintain flow of fluid over the surface of epithelia (non-motile) cilia: involved in sensing flow |
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Term
Define absorption and give an example |
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Definition
movement from the external compartment (lumen of the renal tube/gut_ to the internal compartment (blood) eg glucose absorption in the gut and renal tube |
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Term
Define secretion and give an example |
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Definition
movement from the internal compartment to the external comparment eg. H+ and K+ in the renal tubule; HCO3- secreted by pancreas |
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Term
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Definition
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Term
How can net flux be determined |
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Definition
by using radioactive isotopes as tracers which we assume move in exactly the same way and by the same routes as the non radioactive solutes |
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Term
Describe passive transport across cell membranes |
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Definition
-solutes move down their electrochemical gradients -can occur via pores/channels -transporters facilitate diffusion of small non electrolytes (eg glucose) |
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Term
Describe primary active transport across cell membranes |
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Definition
-energy to drive comes directly from ATP -substrate moves against an electrochemical gradient |
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Term
Describe secondary active transport across cell membranes |
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Definition
-energy to drive comes from electrochemical gradient for one substrate (set up from primary active transport) -second substrate moves against its electrochemical gradient |
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Term
Describe the mechanics of NaCl transport |
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Definition
-apical entry of Na+ -pumped out the basal membrane into into the interstitium -3Na+ are pumped out whilst 2K+ are pumped in (requires ATP) -K+ is recycled via pumpa and leak -Paracellular movement of Cl- |
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Term
Describe sugar absorption |
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Definition
-Na+ glucose symporter (driven by high extracellular Na+) enters the cell. SECONDARY ACTIVE. -Glucose leaves the cell into the ECF via PASSIVE transport -Na+ leaves the cell by a Na+K+ pump. PRIMARY ACTIVE. |
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Term
How would water move through those cells? |
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Definition
Moves lumen to ECF through paracellular junctions/transcellular pathway |
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Term
Where in the body could this represent? |
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Definition
Renal proximal tubule or small intestine |
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Term
Why does net solute movement usually drive net fluid movement? |
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Definition
water flows from areas of low osmotic pressure to areas of high osmotic pressure |
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Term
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Definition
one tube, 8-9m long, up to 15cm wide mouth > pharynx > esophagus > stomach >small intestine >colon > rectum > anus |
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Term
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Definition
20-55mm long, about 50 micrometres wide
Glomerulus > proximal tubule > loop of Henle > Distal tubule > collecting duct
More than a million of them |
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Term
What do the kidneys maintain |
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Definition
the volume and composition of the body's fluids |
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Term
What hormones regulate the kidneys |
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Definition
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Term
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Definition
an adrenal steroid that promotes sodium reabsorption |
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Term
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Definition
a hormone released form the heart that promotes loss of sodium (natriuresis) |
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Term
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Definition
a hormone released from the pituitary glands that promotes retention of water. Produces small more concentrated volume of water |
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Term
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Definition
a parathyroid hormone that affects excretion of phosphate and calcium as well as synthesis of vitamin D |
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Term
Which hormones do the kidneys synthesise and release? |
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Definition
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Term
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Definition
involved in the formation of angiotensin II, a peptide with effects on the vasculature and adrenal gland. |
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Term
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Definition
involved in calcium and phosphate metabolism |
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Term
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Definition
a protein that promotes formation of RBCs |
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Term
What is the rate of renal plasma flow |
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Definition
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Term
What is the glomerular filtration rate |
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Definition
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Term
How much salt is filtered each day? |
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Definition
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Term
Where do the kidneys lie? |
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Definition
between the levels of the 12th thoracic and 3rd lumbar vertebrae |
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Term
Which kidney is lower than the other and why? |
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Definition
The right kidney is lower because it is overlain by the right lobe of the liver (and spleen) |
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Term
What is the source of ADH? |
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Definition
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Term
Which is more lateral the renal cortex or renal medulla? |
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Definition
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Term
How much blood plasma do the kidneys filter? |
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Definition
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Term
Describe the arterial blood supply to the nephron |
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Definition
Renal artery > segmental arteries > interlobal arteries > arcuate arteries > cortical radiate arteries > NOW IN THE NEPHRONS: afferent arterioles > Glomerulus > Efferent arteriole |
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Term
Describe the venous blood supply to the nephron |
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Definition
Efferent arterioles > Peritubular capillaries > OUT OF NEPHRON: venules > cortical radiate veins > arcuate veins > interlobal veins > renal vein |
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Term
What are the functions of peritubular capillaries and what do they surround |
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Definition
-provides nutrients -retrieve reabsorbate -remove metabolites
renal tubule |
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Term
State the tubular components in order |
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Definition
Glomerulus > Bowman's/renal capsule > Loop of Henle > distal convoluted tubule > collecting duct |
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Term
What is glomerular filtration |
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Definition
movement of plasma solutes and water across glomerular capillaries into Bowmans space and delivering a 'protein free' ultrafiltrate of plasma into the proximal tubule |
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Term
How is the movement of fluid caused in urine formation? |
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Definition
the force of filtration causes movement along the renal tubule |
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Term
What is tubular reabsorption? |
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Definition
movements of solutes and water from the lumen of the tubule back into the blood |
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Term
What is tubular secretion? |
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Definition
movements of solutes (not water) from the blood into tubular lumen |
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Term
What effects to diuretics have |
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Definition
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Term
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Definition
water channels are abundant in plasma membrane of the proximal tubular cells (apical and basolateral). This allows water to move osmotically after solutes have been reabsorbed. |
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Term
Proximal tubule: Which compounds are actively absorbed and hence conc falls? |
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Definition
glucose, amino acids, bicarbonate |
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Term
Why does insulins conc increase |
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Definition
It is not absorbed or secreted by the tubule so its conc rises as water follows other absorbed solutes out of tubule |
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Term
Why does sodium concentration remain constant |
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Definition
It is the main cation in the tubular fluid. As it is reabsorbed water is being reabsorbed at the same rate, so conc remains constant. |
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Term
How is concentrated urine achieved in the loop of henle with no active water pumps? |
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Definition
-an osmotic gradient to extract the water from the tubular fluid -the loop of henle achieves this by pumping salt into the interstitium of the renal medulla |
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Term
Whats present in the descending limb and what does this mean? |
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Definition
lots of APQ1 present therefore high water permeability |
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Term
Whats present in the ascending limb and what does this mean? |
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Definition
lots of mitochondria active salt pumping into interstitium making it hypertonic |
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Term
How is blood moved in and out of the medulla without destroying the osmotic gradient set up by the loop? |
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Definition
capillaries have own hairpin arrangement blood flows down, loses water to interstitium and picks up salt blood flows up, loses salt and picks up water |
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Term
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Definition
major antidiuretic hormone in mammals |
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Term
What does a antidiuretic do? |
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Definition
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Term
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Definition
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Term
What does the ability to produce conc urine depend on? |
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Definition
medullary osmotic gradient generated by loop |
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Term
What does change in permeability depend on? |
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Definition
-insertion of APQ2 water channels into apical plasma membrane -APQ2 are only seen in principle cells |
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Term
What events follow when vasopressin/ADH bind to receptors in basolateral membrane? |
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Definition
This is a GPCR linked to adenylate cyclase, cAMP, protein kinase A which phosphorylates APQ2. APQ2 moves to apical membrane and are inserted |
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Term
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Definition
APQ3/4 water channels on basolateral membrane |
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Term
What occurs when ADH levels fall? |
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Definition
AQP2 is retrieved endocytically and membrane returns to highly permeable state. |
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Term
What is the main stimulus to ADH release |
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Definition
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Term
What can also trigger an ADH release |
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Definition
fall in blood pressure/circulatory volume |
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Term
What is the normal osmolarity |
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Definition
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Term
What follows increased osmolarity |
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Definition
Water retention or thirst then normal osmolarity and increased ECF volume |
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Term
What follows decreased osmolarity |
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Definition
Water excretion then normal osmolarity and decreased ECF volume |
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Term
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Definition
specialised cells which sense the amount of water, in the glomerulus. |
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Term
what occurs if water levels are too high |
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Definition
signal afferent artery to contract, decreasing GFR |
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Term
what occurs if water levels are too low |
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Definition
stimulate the granular cells to secrete renin |
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Term
Functions of the GI tract |
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Definition
ingestion mechanical processing secretion (release of water, acids, enzymes, buffers and salts) absorption (movement of organic substrates, electrolytes, vits and water) |
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Term
What is the Gi tracts blood supply |
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Definition
Coeliac artery (becomes hepatic) Superior mesenteric artery Inferior mesenteric artery |
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Term
Describe the general structure of the gi tract (inner to outer) |
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Definition
mucosa submucosa muscularis externa serosa |
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Term
What are the stomach glands? |
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Definition
parietal cells chief cells g cells |
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Term
what do the parietal cells do |
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Definition
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Term
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Definition
secrete pepsinogen (inactivates proenzyme) which is converted by hcl in gastric lumen to pepsin |
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Term
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Definition
secrete gastrin (endocrine stimulator of parietal cells) |
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Term
What are the functions of bile? |
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Definition
emulsification of fat -dietry lipids are not water soluble -mechanical processing in stomach creates large droplets containing lipids -bile breaks droplets apart therefore increases surface area exposed to pancreatic lipase |
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Term
What are the main GI hormones |
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Definition
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Term
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Definition
comes from g cells and modifies acid secretion and stimulates gastrin contractions |
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Term
What are the 3 phases of gastric secretion |
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Definition
cephalic, gastric and intestinal |
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Term
What occurs in the cephalic phase of secretion? |
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Definition
1.the taste/smell/tactile sensation of food in the mouth sends nerve impulses to the medulla oblongata 2.this increases parasympathetic activity 3.vagus nerve innervate the submucosal plexus of the stomach |
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Term
What do the postganglionic parasympathetic fibres innervate? |
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Definition
parietal and cheif cells G cells |
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Term
What is the outcome of the cephalic phase? |
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Definition
G cells increase gastrin secretion and plasma gastrin acid and pepsinogen secretion is increased |
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Term
What occurs in the gastric phase of secretion? |
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Definition
1.begins with arrival of food in stomach 2.stimuli include: -distension of the stomach -increase in the pH of gastric contents -presence of undigested food in stomach |
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Term
What are the short and long reflexes? |
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Definition
short: straight to G cells long: chemoreceptos and mechanoreceptors |
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Term
What is the gastric of the cephalic phase? |
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Definition
Acid and pepsinogen secretion |
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Term
What is the stimuli for secretin? |
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Definition
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Term
What is secretin secreted by? |
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Definition
APUD cells in duodenal mucosa |
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Term
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Definition
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Term
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Definition
-stimulates fluid and bicarbonate secretion -weak effects on pancreatic proenzymes and insulin -inhibits gastric and intestinal motility -inhibits gastric acid secretion -example of negative feedback |
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Term
What is the stimuli for CCK-PZ secretion? |
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Definition
fatty acids, proteins and amino acids |
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Term
What is CCK-PZ secreted by? |
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Definition
APUD cells in duodenal mucosa |
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Term
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Definition
gall bladder and pancreas |
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Term
What are the effects of CCK-PZ |
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Definition
-gall bladder contraction -relaxation of Sphincter of Oddi -stimulation of pancreatic secretion (bicarb and proenzymes) -inhibits gastric emptying -stimulates gastric and intestinal motility |
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Term
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Definition
anticipatory phase: affects saliva production and medulla passes on signal to stomach to produce gastrin therefore producing acid and pepsin |
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Term
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Definition
gastric: sensory receptors detect distension stimulates gastrin and to medulla |
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Term
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Definition
intestinal: as food enters the duodenum, further hormone wave is triggered which causes the release of bile and pancreatic secretions into gut lumen |
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Term
Which nutrients must be digested before absorbed? |
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Definition
carbohydrates proteins lipids |
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Term
Which nutrients can immediately be absorbed? |
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Definition
water electrolytes vitamins |
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Term
What do brush border enzymes digest? |
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Definition
tri and di saccharides and tri and di peptides |
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Term
How are carbohydrates digested? |
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Definition
-soluble amalyse (in saliva and pancreas) breaks internal alpha1-4 bonds (not alpha1-6 bonds) -reamining short carbs broken by brush border enzymes -monosaccharides absorbed by 2ndary active transporters |
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Term
why is fructose different? |
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Definition
fructose monosaccharides are absorbed passively |
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Term
What does gastric acid do to pepsinogen in the stomach |
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Definition
cleaves pepsinogen hence activating it into pepsin which degrades food proteins into peptides |
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Term
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Definition
enzymes that help hydrolysis of polypeptides |
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Term
What is the major site of protein digestion |
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Definition
duodenum pepsin is inactivated here trypsinogen is cleaved into trypsin which activates other enzymes |
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Term
What is the fate of the small produced peptides |
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Definition
diffuse into the brush border where peptidases chop them into amino acids and dipeptides |
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Term
Carbohydrates: how do starch/disaccharides become poly/disaccharides? |
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Definition
salivary amylase (mouth) pancreatic amylase (small intestine) 1,4 alpha bonds broken only |
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Term
Carbohydrates: how do poly/disaccharides become mono? |
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Definition
broken down by specific enzymes on brush border enzymes (small intestine) |
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Term
Carbohydrates: what is the fate of the produced monosaccharides? |
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Definition
absorbed by secondary active transporters transported to the liver via hepatic portal vein |
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Term
Proteins: how do proteins become large polypeptides |
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Definition
pepsin (from stomach glands) in presence of HCl
stomach |
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Term
Proteins: how do large polypeptides become small poly and small peptides? |
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Definition
pancreatic enzymes trypsin (small intestine) |
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Term
Proteins: how small poly and small peptides become amino acids? |
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Definition
brush border enzymes small intestine |
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Term
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Definition
diffuse into the brush border where peptidases chop them into amino acids and dipeptides |
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Term
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Definition
mainly triglycerides and phospholipids |
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Term
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Definition
1.fats are broken down pacreatic lipase aided by bile salts which break up lipid droplets (increasing surface area) 2.mixed micelles diffuse close to the brush border, delivery contents to membrane |
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Term
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Definition
monoglycerides and fatty acids complex with bile salts (which solubilise them) |
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Term
How are mono's re-synthesised back into tri's? |
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Definition
once in the cell. they must be broken down to cross the cell membrane. |
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Term
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Definition
in the liver by hepatocytes |
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Term
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Definition
1.specific transports in the distal ileum move bile salts from the lumen of the DI to the intestinal capillaries 2.they are transported directly to the liver via the hepatic vein |
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Term
How are fat-soluble vitamins absorbed? examples |
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Definition
absorbed with lipids dissolved in lipid droplets, micelles, chylomicrons A, D, E and K |
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Term
How are water-soluble vitamins absorbed? examples |
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Definition
required special transport proteins (Na+) |
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Term
How is vit b12 absorbed? examples |
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Definition
absorbed only when bound to intrinsic factor (secreted by gastric parietal cells) |
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Term
What would occur that meant you were no longer able to absorb vit b12? |
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Definition
removed part of stomach (to lose weight) lost aprt of small intestine (Chromes disease) |
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Term
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Definition
precursor to rbc production |
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Term
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Definition
creatinine technique measurement of creatinine conc and urine flow rate |
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Term
what occurs in the renal corpuscle |
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Definition
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Term
proximal convulated tubule |
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Definition
reabsorption of water, ions and all organic nutrients |
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Term
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Definition
secretion of ions, acids, drugs and toxins variable reabsorption of water, sodium ions and calcium ions |
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Term
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Definition
variable reabsorption of water and reabsorption or secretion na, k, h and bicarb ions |
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Term
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Definition
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