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BIOM2012 (1, 2, 3, & 6) > 3 - renal + GI > Flashcards

3 - renal + GI Flashcards

1
Q

TRUE OR FALSE

the left kidney is higher than the right

A

TRUE

left kidney more superior due to the liver on the right side

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2
Q

describe the structure and function of the kidney

A

RENAL CORTEX = outer layer, site of glomerular filtration and the convoluted tubules

RENAL MEDULLA = inner part, location of the longer loops of Henle, and the drainage of the collecting ducts into the renal pelvis and ureter

RENEL PELVIS = entry point for blood vessels and nerves

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3
Q

what is the individual functional unit of the kidney?

draw a diagram of its structure

A

individual functional units = “nephrons”

nephron made up of:
– a filtration component (renal corpuscle = the glomerulus and bowmans capsule)
– a complex set of renal tubules, which are further divided into structural and functional regions

glomerulus* → bowmans capsule → proximal tubule → thin descending + ascending limb of Henle → thick ascending limb of Henle → macula densa → distal tubule → connecting tubule → cortical connecting tubule → medullary connecting tubule → collecting duct

GLOMERULUS = filtration unit of nephron:
– tuft of interconnected capillaries (glomerular capillaries)
– a fluid filled capsule (bowmans capsule)

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4
Q

describe the flow through and excretion of urine from the nephron

A
  1. plasma volume enters afferent arteriole
  2. 20% volume filtered in glomerulus to bowmans capsule
  3. 80% enters efferent arteriole and peritubular capillaries
  4. 99% of filtered volume is reabsorbed into peritubular capillaries
  5. > 99% of plasma entering the kidney returned to systemic circulation, rest is excreted

EXCRETION = filtration - reabsorption + secretion

glomerular filtration:
– the movement of fluid and solutes from the glomerular capillaries into Bowman’s space

tubular reabsorption:
– taking fluids back into body
– movement of materials from the filtrate in the tubules into the peritubular capillaries

tubular secretion:
– removing fluid from body
– movement of solutes from the peritubular capillaries into the tubules

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5
Q

give a detailed description on how fluid is filtered through the glomerular filtration barrier

A

glomerular filtration barrier consists of 3 layers:
– single-celled endothelial fenestrations
– non-cellular basement membrane
– single-celled epithelial lining of Bowmans capsule (podocytes + slit diaphragm)

fluid forced through the barrier by hydrostatic pressure from cardiac pump

fluid is filtered from the blood through fenestra in the glomerular capillaries into slit pores between the foot processes of the podocytes

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6
Q

what is starlings law?

A

hydrostatic pressure from the heart FAVOURS filtration

Plasma osmotic pressure and hydrostatic pressure of the filtrate oppose it

increasing protein concentration inside glomerular capillary will oppose filtration

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7
Q

what is GFR and how does it depend on filtration pressure?

A

glomerular filtration rate (GFR) equals the volume of filtrate formed each minute

GFR is directly proportional to the net filtration pressure

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8
Q

why does GFR need to be kept constant?

A

GFR must be kept constant as reabsorption of H2O & other substances from filtrate partly dependent on rate of flow through tubules

↑ GFR = inadequate reabsorption = substances lost in urine
↓ GFR = reabsorption increased = wastes not excreted

small changes in GFR equal large changes in the
volume of filtrate that must be processed

10% increase in GFR equals 18L more filtrate to be processed

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9
Q

use a diagram to describe how P(G) / GFR is affected by:

1) arterial pressure
2) afferent arteriolar resistance
3) efferent arteriolar resistance

A

ARTERIAL PRESSURE
↑ AP = ↑ P(G) = ↑ GFR

AFFERENT ARTERIOLAR RESISTANCE
↑ AAR = ↓ P(G) = ↓ GFR
↓ AAR = ↑ P(G) = ↑ GFR

EFFERENT ARTERIOLAR RESISTANCE
↑ EAR = ↑ P(G) = ↑ GFR
↓ EAR = ↓ P(G) = ↓ GFR

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10
Q

how does GFR effect systemic blood pressure?

A

increased GFR = decreased urine output = reduced BP (vice versa)

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11
Q

in what MAP range is GFR auto-regulated?

A

GFR automatically maintained constant when MAP = 80-180mmHg

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12
Q

name the two types of autoregulation?

A

tubuloglomerular feedback mechanism

myogenic mechanism

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13
Q

describe how the tubuloglomerular feedback mechanism regulates glomerular filtration

A

TUBULOGLOMERULAR FEEDBACK

as distal tubule passes through parent glomerulus, there are macula densa (MD) cells

MD cells sense NaCl concentration inside tubule
——> NKCC2 cotransporter transports Na, Cl and K into MD cells

increase GFR, increase sodium filtration —> detected by MD

ATP passes through basolateral membrane, converted to AMP —> adenosine

binds A1 receptor on extraglomerular cells —> activates Gi —> inhibits adenylate cyclase
—> also activates Go —> increases intracellular calcium

calcium spreads to surrounding smooth muscle cells via junctions

calcium causes contraction —> afferent arteriole constriction —> reduce GFP

MD sends signal to afferent arteriole to constrict = reduce GFR

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14
Q

describe how the myogenic mechanism regulates glomerular filtration

A

MYOGENIC MECHANISM

– increased pressure in afferent arteriole is detected by smooth muscle = stretch = arteriole dilates
– stretching opens stretch-activated ion channels in arteriole membrane
– sodium ions enters cell —> depolarisation
– this opens Ca2+ channels on SR reticulum
– intracellular calcium facilitates muscle contraction —> membrane returns to normal shape

this mechanism helps maintain normal GFR despite fluctuations in BP
constrict afferent arteriole = GFR decrease = less blood is entering glomerulus

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15
Q

give an example of a substance that is not filtered

A

large proteins

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16
Q

give an example of a substance that is filtered but not reabsorbed or secreted

A

insulin

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17
Q

give an example of a substance that is filtered, completely reabsorbed, but not secreted

A

glucose

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18
Q

give an example of a substance that is filtered, some reabsorbed and some secreted

A

electrolytes

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19
Q

where is sodium reabsorbed?

give percentages

A

64% in proximal tubules

28% in loop of Henle

7% in distal tubule and collecting duct

1% excreted

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20
Q

where is water reabsorbed?

give percentages

A

67% in proximal tubules

10% in loop of Henle

9% in distal tubule and collecting duct

<1% excreted

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21
Q

what is the transport maximum?

A

point at which carrier proteins are saturated i.e. no more can be reabsorbed

at transport maximum, solute begins to be excreted

22
Q

the reabsorption of which particular solute drives reabsorption of other solutes?

A

sodium reabsorption drives other substances to be reabsorbed

23
Q

draw a diagram depicting the ion flow across the proximal tubule

A

1) at the basolateral membrane, Na is pumped into the interstitial space by the Na+-K+ ATPase. active Na+ transport creates concentration gradients that drive:
2) “downhill” Na+ entry at the apical membrane
3) reabsorption of organic nutrients and certain ions by cotransport at the apical membrane
4) reabsorption of water by osmosis through aquaporins. water reabsorption increases the concentration of the solutes that are left behind. these solutes can then be reabsorbed as they move down their gradients:
5) lipid-soluble substances diffuse by the transcellular route.
6) various ions (e.g., Cl−, Ca2+, K+) and urea diffuse by the paracellular route.

24
Q

draw a diagram depicting the ion flow across the thick ascending loop of henle

A

{:-D~

25
Q

draw a diagram depicting the ion flow across the cortisol collecting ducts

A

8^]¢

26
Q

how is urine concentration regulated?

describe this process at each point in the nephron

A

remember: water diffuses from HYPO-osmotic compartment to HYPER-osmotic
i. e. water follows sodium

for example:

  1. in the ascending limb, NaCl is actively transported out of the tubule
  2. medullary interstitial fluid becomes HYPERosmotic
  3. water diffuses out from the descending limb of the Loop of Henle (simple diffusion) into the hyperosmotic medullary ISF

proximal tubules:
– always reabsorb sodium and water in the same proportions

ascending limb:
– Na+ and Cl- are reabsorbed from the tubule into the medullary interstitium
– requires energy = active transport
– impermeable to water
– medullary interstitial fluid becomes hyperosmotic

descending limb:
– highly permeable to water
– dilutes concentrated fluid

27
Q

which four receptors detect changes in ECF and where are they found?

A

OSMORECEPTORS
– hypothalamus
– changes in composition

ADRENAL CORTEX
– zona glomerulosa
– changes in composition

BARORECEPTORS
– aortic arch + carotid artery
– changes in volume

STRETCHRECEPTORS
– atrium + pulmonary vessels + ventricles
– changes in volume

28
Q

how does ADH respond to excess water intake?

A

1) excess water ingested
2) ↓ ECF osmolarity
3) ↓ firing by hypothalamic osmoreceptors
4) ↓ ADH secretion by post. pituitary
5) ↓ plasma ADH
6) collecting ducts ↓ permeability to H2O = ↓ reabsorption
7) ↑ H2O excretion

29
Q

what is the body’s response to dehydration?

A

1) DEHYDRATION
2) ↑ ECF osmolarity

3) a) thirst
b) osmoreceptors shrink and the supraoptic and paraventricular nuclei and send neural signal to post. pituitary to ↑ ADH secretion

4) ↑ plasma ADH
5) ADH stimulates V2 receptors in collecting ducts = actvate adenylate cyclase = insertion of aquaporins into luminal membrane= ↑ permeability to H2O = ↑ reabsorption
6) ↓ H2O excretion

30
Q

what is the action of atrial natriuretic peptide?

A

atrial natriuretic peptide is a hormone released by the cardiac atria

it is a potent vasodilator which acts on post. tubule to inhibit sodium reabsorption
= regulates sodium balance and blood volume

can also increase GFR – further contributes to increased sodium excretion

31
Q

give a detailed description of the renin-angiotensin-aldosterone system

A

renin is synthesised, stored and released by the granular cells in the JGA region of the afferent arteriole

renin release is stimulated by:
– intrarenal baroreceptors upon low BP
– MD cells upon ↓ NaCl delivery
– renal sympathetic nerves
* neg. feedback system where angiotensin II decreases renin release

angiotensin released from liver

renin + angiotensin = angiotensin II

angiotensin II:
• potent vasoconstrictor
• activates sodium reabsorption
• stimulates aldosterone
production from adrenal cortex = increase sodium reabsorption
• stimulates ADH release
32
Q

aldosterone is released from ______ in response to ______

aldosterone acts on ______ to increase the absorption of ______ from the tubule

A

aldosterone is released from adrenal cortical zona glomerulosa cells in response to increased plasma K+ and angiotensin II

aldosterone acts on the renal distal tubule to increase the absorption of sodium from the tubule

33
Q

what are the two categories of digestive organ?

A

1) ALIMENTARY CANAL (Gi tract/ gut)
– continuous muscular tube that runs from the mouth to anus
– digests food: breaks down into smaller fragments
– absorbs fragments through lining into blood
– organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

2) ACCESSORY DIGESTIVE ORGANS
– teeth and tongue (mechanical breakdown)
– gallbladder
– digestive glands which produce secretions that help breakdown foodstuffs (salivary glands, liver, pancreas)

34
Q

list and briefly describe the 6 essential activities in digestion

A

1) ingestion

2) propulsion
• movement of food through alimentary canal:
• swallowing
• peristalsis (major means of propulsion of food that involves alternating waves of contraction and relaxation)

3) mechanical breakdown
• chewing
• mixing with saliva
• churning food in stomach
• segmentation (local constriction of intestine that mixes food with digestive juices)

4) digestion
• series of catabolic steps that involves enzymes that break down complex food molecules into chemical building blocks

5) absorption
• passage of digested fragments from lumen of GI tract into blood or lymph

6) defecation
• elimination of indigestible substances via anus in form of feces

35
Q

describe the digestive process in the mouth

A

mechanical breakdown of food with teeth, tongue and saliva

deglutition (swallowing) involves 22 muscle groups and two phases:
phase 1 = buccal phase + phase 2 = pharyngeal-oesophageal phase

  1. BUCCAL PHASE
    – upper oesophageal sphincter is contracted (closed)
    – tongue presses against the hard palate, forcing the food bolus into the oropharynx

2) PHARYNGEAL-OESOPHAGEAL PHASE
– tongue blocking the mouth, nasopharynx closed and epiglottis blocking the trachea.
– upper oesophageal sphincter relaxes = food enters the oesophagus
– constrictor muscles of the pharynx contract, forcing food down oesophagus
– upper oesophageal sphincter contracts after food enters
– mood moved to stomach via peristalsis
– gastro-oesophageal sphincter surrounding the cardial orifice opens to allow food into stomach (closes afterwards to prevent regurgitation)

36
Q

where does the oesophagus join the stomach?

A

cardial orifice

gastroesophageal (cardiac) sphincter surrounds cardial orifice

37
Q

what is gastritis?

A

gastritis = inflammation caused by anything that breaches stomach’s mucosal barrier

38
Q

what are gastric ulcers

A

erosions in stomach wall
if erosions perforate wall, can lead to peritonitis and haemorrhage

mostly caused by bacteria or anti-inflammatory drugs

39
Q

describe the digestive process in the stomach

A

1) food enters stomach via the cardial orifice (gastro-oesophageal sphincter opens)
2) denatures proteins by HCl
3) pepsin carries out enzymatic digestion of proteins / in infants, milk proteins broken down by rennin = curdy substance
4) lipid-soluble alcohol and aspirin are absorbed into blood

5) secretion of intrinsic factor for vitamin B12 absorption (only stomach function essential for life)
– B12 needed for red blood cells to mature
– lack of intrinsic factor causes pernicious anemia
– treated with B12 injections

40
Q

how is gastric secretion regulated?

A

neural regulation:
– vagus nerve stimulation increases secretion
– sympathetic stimulation decreases secretion

hormonal regulation:
– gastrin stimulates enzyme and HCl secretion
– gastrin antagonists are secreted by small intestine

41
Q

list and describe the three phases of gastric secretion

A

1) CEPHALIC / REFLEX PHASE
– conditioned reflex triggered by aroma, taste,
sight, thought

2) GASTRIC PHASE
– distension activates stretch receptors, initiating both
long and short reflexes
– chemical stimuli (partially digested proteins,
caffeine, low acidity) activate G cells to secrete gastrin
– release of gastrin then initiates HCl release from
parietal cells and activates enzyme secretion
– low pH inhibits gastrin release
– lasts 3–4 hours and provides two-thirds of gastric juice released

3) INTESTINAL PHASE
– partially digested food enters small intestine, causing
a brief release of intestinal gastrin
– this encourages gastric glands to continue activity
– stimulatory effect is brief and overridden by inhibitory stimuli as intestine fills
– presence of chyme in duodenum inhibits gastrin secretion
– inhibition is achieved in two ways: enterogastric reflex and enterogastrones

enterogastric reflex:
• duodenum inhibits acid secretion in stomach by enteric nervous system short reflexes and sympathetic nervous system/vagus nerve long reflexes

enterogastrones:
• duodenal enteroendocrine cells release two important
hormones that inhibit gastric secretion - secretin + CCK

42
Q

list in order the sphincters which control the passage of food along the gut

A
  1. Upper oesophageal sphincter
  2. Lower osoephageal sphincter
  3. Pyloric sphincter = the opening from the stomach
    into the duodenum
  4. Oddi (hepatopancreatic) sphincter = muscular valve that controls the flow of digestive juices (bile and pancreatic juice)
  5. Ileocecal sphincter = muscle valve that separates the small intestine and the large intestine
  6. Internal anal sphincter
  7. External anal sphincter
43
Q

what is the MMC?

A

MMC = migrating myoelectric complex

peristaltic contractions of several adjacent segments from stomach to large intestine

moves undigested remains to large intestine

functions in between meals to empty stomach for next meal (stops when meal enters stomach)

initiated by ↑ chyme pH or [motilin]* in plasma i.e. feeding inhibits release of motilin
* motilin = hormone released by small intestine to trigger epistaltic contractions

modulated by ENS & ANS

44
Q

TRUE OR FALSE

the GI tract contains pacemakers

A

TRUE

slow waves begin spontaneously in interstitial cells of Cajal (ICC)

ICCs act as pacemakers in GI tract

slow waves that begin in ICCs spreads to adjacent smooth muscle layers via gap junctions

45
Q

describe the digestive processes in the small intestine

A
  • chyme mixed with digestive juices and slowly moved along SI
  • chemical digestion is completed
  • nearly all nutrient absorption occurs
  • moves undigested remains to large intestine
46
Q

describe the digestive processes in the large intestine

A
  • mixing contractions
  • chemical digestion by enteric bacteria • absorption (H2O & electrolytes)
  • propulsive actions
  • excretion
  • note: large intestine not essential for life
47
Q

name and describe the two factors which regulate pressure in the stomach

A

two factors cause pressure to remain constant until 1.5 L of food is ingested

1) RECEPTIVE RELAXATION
reflex-mediated relaxation of smooth muscle coordinated by swallowing centre of brain stem

2) GASTRIC ACCOMODATION
intrinsic ability of smooth muscle to exhibit stress-relaxation response = Hollow organs can stretch
without increasing tension or contractions

48
Q

TRUE OF FALSE

peristaltic waves move toward pylorus at rate of four per minute

A

FALSE

peristaltic waves move toward pylorus at rate of THREE per minute

49
Q

use three steps to describe to movement of food from the stomach to the duodenum

A

1) PROPULSION:
– peristaltic waves move from the fundus toward the pylorus

2) GRINDING:
– most vigorous peristalsis and mixing action occur close to the pylorus
– pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum

3) RETROPULSION:
– peristaltic wave closes the pyloric valve
– most of the contents of the pylorus forced backward into the stomach

50
Q

how does chemotherapy effect the digestive tract?

A

• Chemotherapy targets rapidly dividing cells,
such as cancer cells

  • Negative side effect is that it also targets rapidly dividing GI tract epithelium
  • Reason why many patients undergoing chemotherapy have symptoms of nausea, vomiting, and diarrhoea
51
Q

describe how defecation is controlled

A

1) feces move into and distend the rectum, stimulating stretch receptors there
2) receptors transmit signals along afferent fibres to spinal cord neurons
3) spinal reflex is initiated in which parasympathetic motor (efferent) fibres stimulate contraction of the rectum and sigmoid colon, and relaxation of the internal anal sphincter
4) if it is convenient to defecate, voluntary motor neurons are inhibited, allowing the external anal sphincter to relax so feces may pass

BIOM2012 (1, 2, 3, & 6) (4 decks)

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