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First year semester 2 > Intestines > Flashcards

Intestines Flashcards

1
Q
  1. What is the role of the small intestine in simple stomached mammals?
A

a. Digestion and MAINLY absorption

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2
Q

What are the 2 phases of digestion?

A
  1. Luminal = enzymes secreted by salivary glands/ pancreas,

2. Membranous = enzymes attached to epithelial surface of intestinal cells

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3
Q

What kind of process absorption and how?

A

Absorption = selective process

HOW: specific transporter proteins, diffusion and secondary active transport)

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4
Q

What nutrients are absorbed irrespective of body requirements? What aren’t and why

A

a. Absorbed irrespective = Organic nutrients
b. NOT absorbed = Carbohydrates, protein, fat
c. Why? Those that could cause toxicity aren’t: Divalent ions and trace elements (copper)

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5
Q
  1. What is the only nutrient that is absorbed in the large intestine and can’t be absorbed in the small? Where is water absorpbed in most specied BUT?
A

a. FIBRE

b. 80% water absorbed in small I in most species BUT horses where it is large I

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6
Q

Functional anatomy of the small intestine?

compartments and what made up of

A

a. 3 parts: DUODENUM (15%), JEJUNUM (75%), ILEUM (10%)
b. Can’t distinguish between each part by eye
c. Mucosa = epithelium facing lumen, submucosa, muscle = 2 parts: inner circular and outer longitudinal, serosa = outer casing

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7
Q
  1. How is the surface area of the SI increased?
A

a. Mucosal folds
b. Villi = folds on mucosal folds
c. Microvilli = folds on each villi, that create a brush border

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8
Q
  1. What are the types of intestinal epithelial cell?
A

a. Goblet = secrete mucous for lubrication and protection of mucosa. Secrete HCO3- for neutralisation of stomach acid
b. Enteroendocrine cells = control digestive function via sensory mechanism and release hormones
c. Paneth cells – defence vs microbial penetration
d. Enterocytes (mainly) = responsible for absorption. Membrane bound enzymes. “brush border” appearance

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9
Q

What part of the SI are goblet cells more prominent in? WHY?

A

a. Proximal part (duodenum)

b. Neutralise acid with bicarbonate

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10
Q

What is the purpose of motility in the small intestine?

A

a. Mix luminal contents (segmental contractions)

b. Move contents down SI at appropriate rate for max digestion and absorption (peristalsis)

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11
Q
  1. What are the main types of contraction when digestive and absorbing and when stopped
A

a. D and A = segmental

b. Stopped = peristaltic

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12
Q
  1. What determines the type of motility?
A

a. Coordination between contraction and relaxation of longitudinal and circular muscles

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13
Q
  1. How is motility regulated?
A

a. By interstitial cells of Cajal which are pacemaker cells
b. Continuous oscillation of membrane potential always just below threshold
c. Above threshold = action potential.
d. Frequency of these determines the strength of AP
e. AP propagates from cell to cell via gap junctions
f. Regulated by enteric nervous system
g. Strength inc by parasympathetic and decreased by sympathetic

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14
Q
  1. Hydrolysable carbohydrate
A

a. Alpha glycosidic bonds = digestible by mammalian enzymes
b. Starch
c. Amylopectin
d. Glycogen

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15
Q
  1. Non hydrolysable carbohydrate
A

a. Beta glycosidic bonds = indigestible by mammalian enzyme
b. Cellulose
c. Requires microbial fermentation

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16
Q
  1. Name disaccharides

2. Name monosaccharides

A 
DIA = 
a.	Maltose (glucose and glucose)
b.	Sucrose (glucose and fructose)
c.	Lactose (glucose and 
MONO = 
a.	Glucose, fructose, galactose
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17
Q
  1. What is the largest carbohydrate component that can be absorbed?
A

MONOsaccharides

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18
Q
  1. What hydrolyses disaccharides into mono?
A

a. Disaccharidases: maltase, sucrase, lactase

b. Attached to enterocyte brush border

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19
Q
  1. How does the disaccharidase enzyme levels change with age
A

a. Neonate = high lactase, low maltase
b. Adult = low lactase, high maltase
c. Ruminants = no sucrase

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20
Q
  1. What are the different types of carbohydrate transporter protein and what do they absorb?
A

a. Glucose and galactose absorbed by sodium-glucose co transporter (SGLT1)
b. Fructose absorbed down conc gradient by facilitative transporter (GLUT5)

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21
Q
  1. How is glucose and galactose absorbed by sodium-glucose co transporter?
A

a. Secondary active transport
b. Na+ and glucose/ galactose bind to transported on luminal side
c. Conformational change in T protein moves NA+ and glu/gal into cell and release them into cytosol
d. High levels Na+ in digestive juice = luminal conc Na+ high
e. Conc glucose/ galactose in cyctol high so diffuse down conc gradient into blood stream via facilitative transporter GLUT2

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22
Q
  1. How is fructose absorbed by GLUT5?
A

a. Down conc gradient
b. Passive transport
c. Diffuse out of cytosol down conc gradient into blood stream via GLUT2

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23
Q
  1. How are glucose, galactose and fructose transported OUT of the cell
A

a. By GLUT2 transporter protein

24
Q
  1. Where are the monosaccharides then transferred to once in cell from lumen?
A

a. Transferred to liver via hepatic portal vein

b. Stored as glycogen or continue in circulation to be metabolised for energy

25
Q
  1. Lactose intolerance
A

a. Main carb in milk = lactose
b. Requires lactase  glucose and galactose
c. High in neonates, negligible in adults
d. Absence of lactase, lactose accumulates in gut lumen
e. Creates osmotic force = water out of blood, into gut = diarrhoea
f. Diarrhoea into large intestine, where fermentation occurs, lactose is fermented = lactic acid
g. Increases pH, bacteria like neutral pH so die when the pH inc so fermentation stops
h. Excessive gas produced, lactic acid build up, lots of diarrhoea

26
Q
  1. Protein digestion and absortion:
A

a. Initiated in stomach
b. Continues in small I with pancreatic proteases secreted into lumen of gut and break down protein into small enough unit to be absorbed
c. Can absorb 3, 2 or 1 amino acid component
d. Absorbed along Na+ by co transport
e. Di/ tri peptides absorbed along with H+ co transport

27
Q
  1. What affects the rate of protein digestion and absorption?
A

a. Enzymatic digestion is very fast therefore rate limiting factor is rate of absorption

28
Q
  1. What are differences between protein and carbohydrate digestion/ absorption?
A

a. Final stage of digestion C = membranous phase P = luminal
b. C = only monomers absorbed P = monomers/ dimers/ trimers
c. C = small number enzymes required as complex CHO composed of 3 types of monomer (monosaccharides) P = large number of enzymes as protein composed of 20 diff AA

29
Q
  1. What is a similarity between Carb and Pro absorption?
A

a. Both transported via secondary active transport.

b. Require Na+ gradient/ co transport

30
Q
  1. What is different with ungulate neonates and antibodies?
A

a. Don’t receive maternal placental transfer of antibodies

b. Occurs in first 24-36 hrs of life via colostrum

31
Q
  1. If we can’t eat antibodies because they’d just be broken down into amino acids, why can ungulate neonates receive them in this way?
A

a. In first 24 hrs of life epithelial cells of intestine = permeable to intact protein
b. These close up to prevent bacteria from getting into same holes
c. So that is how they absorb antibodies intact so AB can carry on functioning as a antibody and transfer immunity to the neonate ungulate

32
Q
  1. Fat digestion
A

a. Lipase, secreted from pancreas breaks down triglycerides into monoglycerides and free fatty acids (FFA)

33
Q

What is the rough composition of fat, protein and carbs in carnivores, omnivore, herbivore

A

a. Carnivores = high fat, high protein
b. Omnivore = high fat, high protein, high carbs
c. Herbivore = low fat (but can still absorb so added in commercial herbi diets), low protein, high carbs

34
Q
  1. How is water absorbed?
A

a. 2 main routes
b. Para cellular – across tight junctions between epithelial cells
c. Trans cellular – across cell membrane via transporter proteins (aquaporins in luminal membranes) (main route is osmosis through Na+/ glucose or amino acid transporter)

35
Q
  1. Where does most water reabsorption occur?
A

a. Small intestine
b. Carnivores/ omnivores = 90%
c. Ruminants = 70%
d. Horses – most absorption occurs in LI

36
Q
  1. If huge dehydration, how to inc water absorption?
A

a. Water along, absorbed by aqua porins.
b. Eventually level of solutes in lumen = level of solutes in cell
c. Add salt and glucose to water, due to Na+/ glucose co transporters, lot more water can be absorbed

37
Q
  1. Mineral absorption
A

a. Most absorbed irrespective of requirements, kidney then gets rid of XS
b. Trace elements Cu, Zn Mg = essential for cellular function but can be toxic if too high = absorbed selectively

38
Q
  1. Absorption of Ca
A

a. Divalent ion
b. Bone growth and calcification
c. Passively absorb if high Ca2+ in body
d. If need lots = actively absorbed. Vit D dependent

39
Q
  1. Absorption of iron
A

a. Regulated according to requirements
b. Divalent
c. 2ndary active transport, with H+
d. Fe2+ low = transferred to blood
e. High = remains in cell bound with apoferritin to form ferritin (intracellular storage of iron)
f. Fe3+ poorly absorbed so reduced to 2+ by vit C

40
Q

Function of the large intestine

A

a. Absorption of water (20%) apart from Horses
b. Fermentation: mechanism by which we deal with non hydrolysable carbo i.e fibre – all species ferment but degree depends on diet of species. Minimal in carnivores/ extensive in horse
c. Glands in mucosa secrete mucous for protection/ lubrication. HCO3- to neutralise VFAs. No digestive enzymes. Only digestion here is microbial (fermentation)

41
Q
  1. Anatomy of LI
A

a. Caecum – ileum enters LI at junction between caecum and colon in all species except horse
b. Colon
c. Rectum (not strictly part of LI as no digestion but storage)

42
Q
  1. What is unique about horse SI going into LI
A

a. Ileum enters into caecum for horses whereas for all other species ileum finishes where colon starts and is attached to caecum – the junction)

43
Q
  1. Anatomy of colon
A

a. Ascending (up, right) , transverse, descending (down on left)
b. Ascending is modified in the different species
i. Carnivore = simple
ii. Omni/ ruminants = moderate
iii. Horse = extensive

44
Q
  1. What are the 4 layers of the GI
A

a. Mucosa
b. Submucosa
c. Muscularis
d. Serosa

45
Q
  1. What are the 2 major cell types of the GI
A

a. Colonocytes (absorptive function). No villi, only crypts, microvilli (much less dense than SI)
b. Goblet cells (secrete mucous/ HCO3-) Prodominant in crypts and lot more than SI

46
Q
  1. SI vs LI determination down microscope
A

a. No villi in colon as not much absorption

b. Lot more goblet cells in colon as needs lots of lubrication!

47
Q
  1. What makes non hydrolysable carbohydrates non hydrolysable?! How can we break these down?
A

a. No mammalian enzymes can break down beta glycosidic bonds (bonds of monosaccharides in structural or non hydrolysable carbohydrates)
b. Only way we can is by exploiting populations of microbes that can break these bonds

48
Q
  1. What kind of environment must fermentation occur in and what is the end product?
A

a. Anaerobic environment – if not forms CO” and water which are useless
b. VFS which can be used for energy and for building and creating glucose. VFA also maintain homeostasis of colonic epithelium

49
Q
  1. What are the types of volatile fatty acid
A

a. Acetate = used in liver, oxidised in most other cells to generate ATP, major source of acetyl CoA for lipid synthesis
b. Propionate = Substrate for gluconeogenesis
c. Butyrate = cellular homeostasis and energy production

50
Q
  1. Absorption in LI

VFAs, Na+, Cl- and water

A

a. VFAs absorbed by VFA/ HCO3- exchanger
b. Na+ absorbed by Na+ channels and Na+/H+ exchanges
c. Cl- absorbed by bicarbonate/ hydroxyl exchange
d. Water – any left over from SI due to osmotic pressure, hydrostatic pressure and solvent drag. HOWEVER extensive reabsorption in horse

51
Q
  1. Diarrhoea
A

a. Clinical sign NOT disease
b. Inc water content of gut contents, increases motility further reducing absorption
c. Water is lost in faeces due to decreased absorption and increased secretion
d. Normal circumstance almost all water reabsorbed in GI tract

52
Q
  1. Cause of diarrhoea (pathophysiology)
A

a. Nutritional – overload of gut capacity to absorb causes osmotic flow of water into gut lumen
b. Infections – e.g. ecoli, salmonella, cholera
c. Stress – strong activation of parasympathetic system inc secretion and motility

53
Q
  1. Treat Diarrhoae
A

a. Intravenous fluid = quickest way in if severe. To maintain blood volume and pressure
b. Oral rehydration = moderate dehydration. Solution of NaCl and glucose as inc osmotic gradient

54
Q
  1. Motility in LI
A

a. Segmental contractions high, not as much as in SI
b. Peristalsis moderately to rectum
c. Antiperistalsis (higher in herbivore) more prominent in proximal colon. To slow down movement
d. Mass movement = evacuate large masses

55
Q
  1. Constipation
A

a. Clinical sign
b. Abnormal accumulation of food material in gut
c. Common cause = dry food, prostate or anal gladns = inhibition of motility due to inflammation/ pain, megacolon = weakened colonic contractions
d. Treat: oral fluids to soften faecal material, paraffin oils to lubricate, drugs to strengthen contractions

56
Q
  1. Defaevation
A

a. Normally rectum empty and store waste material in descending colon
b. Mass movement of colon transfers faeces to rectum
c. Pressure sensitive cells stimulate defaecation reflex = terminal colon and rectum contract
d. • Terminal colon & rectum contract • Inner anal sphincter muscle (smooth muscle) relaxes • Outer anal sphincter muscle (striated muscle) under conscious control in carnivores / omnivores but not horses / ruminants • Can consciously retain outer anal sphincter closed until urgency to defaecate diminishes till next mass movement contraction • Contraction of abdominal muscles help

First year semester 2 (50 decks)

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