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Structure & Function 2 > GI tract physiology > Flashcards

GI tract physiology Flashcards

1
Q

What is prehension?

A

The act of moving food into the mouth
- Directly controlled by CNS

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2
Q

Which nerves are involved in prehension?

A
  • facial nerve
  • glossopharyngeal nerve
  • motor branch of trigeminal nerve
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3
Q

What is mastication?

A

The first act of digestion
- Breaks food into particles; increase SA for digestion
- Moisten and lubricate food
- Involves stratified squamous epithelial cells & terminal branches of sensory neurons

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4
Q

Types of saliva

A
  • Mucous saliva; thicker, for binding food into a bolus
    ZYGOMATIC & SUBLINGUAL
  • Serous saliva; watery, contains amylase
    PAROTID
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5
Q

What gland/s produce mucous saliva?

A

ZYGOMATIC & SUBLINGUAL

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6
Q

What gland/s produce serous saliva?

A

PAROTID

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7
Q

Control of salivary glands

A
  • Mainly regulated by parasympathetic NS
  • Nerve fibres end on the acini
  • Stimulation causes increase saliva production
  • Salivary secretory cells; B-adrenergic receptors activated by sympathetic NS
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8
Q

What are the main components of saliva?

A
  • Mucins (glycoproteins)
  • Hydrogencarbonate ions (HCO3-)
  • Lysozyme & antibodies
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9
Q

Function of mucins in saliva

A

LUBRICATION; mix with water to form mucous

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10
Q

Function of HCO3- in saliva

A

pH REGULATION; neutralisation

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11
Q

Function of lysozyme & antibodies in saliva

A

ANTIBACTERIAL; keep number of bacteria in check

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12
Q

SPECIES SPECIALISATION; starch digestion

A

WHO? omnivores, single stomached herbivores & some birds
HOW? amylase

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13
Q

SPECIES SPECIALISATION; fat digestion

A

WHO? young calves
how? lingual lipase

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14
Q

SPECIES SPECIALISATION; theromoregulation

A

WHO? dogs and rodents
HOW? panting and spreading saliva

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15
Q

SPECIES SPECIALISATION; binding of tanins

A

WHO? leaf-eaters
HOW? binding proteins

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16
Q

SPECIES SPECIALISATION; providing urea

A

WHO? animals with forestomachs
HOW? urea diffuses from blood into saliva

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17
Q

RUMINAT SPECIALISATIONS

A
  • Bicarbonate phosphate makes saliva alkaline
  • needed for neutralising fermentation products
  • cows can become easily dehydrated
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18
Q

What are the two phases of deglutition?

A

VOLUNTARY; chewed food is moulded into a bolus and moved to pharynx
INVOLUNTARY

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19
Q

The involuntary phase of deglutition

A

1) Breathing pauses
2) Soft palate elevates
3) Tongue pressed on hard palate
4) Glottis pulled under the epiglottis
5) When openings to pharynx are closed muscular contraction
passes over
6) upper oesophageal sphincter relaxes

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20
Q

Control of deglutition

A

Involuntary phase; by motor neurons in centres of the brainstem
- efferent nerve fibres travel in facial, hypoglossal and glossopharyngeal nerves

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21
Q

Differences in oesophageal muscle between species

A
  • Dogs, cattle & sheep; entire length is striated muscle
  • In horses, primates & cats; portion is smooth muscle
  • striated muscle; vagus nerve
  • smooth muscle; ENS
22
Q

Sphincters of oesophagus

A

Upper and lower; when deglutition NOT taking place body of oesophagus is relaxed but sphincters are closed

23
Q

3 main tasks of the stomach

A

1) Temporary food store
2) Some degradation of protein and starch
3) HCl kills bacteria in food

24
Q

Proximal stomach

A
  • mainly refers to fundus and cardia
  • stomach= empty; remains contracted (tonic contraction)
  • when animal eats; receptive relaxation which is regulated by vagal fibres
  • this aids food storage function
25
Distal stomach
- refers mainly to the pyloric area - more active digestion; stronger peristalsis - large part of wall contract forcing chyme through sphincter - large particles held back
26
4 types of cells in the pits of the stomach wall
- mucin-producing - parietal - chief -endocrine
27
Gastric Secretions
- produced in glands of fundus and corpus - glands in cardia region ONLY secrete mucus - gastric juice= HCl and pepsinogen
28
Hydrochloric acid
- Secreted from parietal cells - pepsinogen to pepsin - kills microorganisms
29
Pepsinogen
- synthesised by chief cells - inactive form of pepsin - pepsin degrades proteins into peptides
30
Three substances involved in regulation of gastric sectretion
- ACH - Gastrin - Histamine
31
Regulation of gastric sectretion
- production of HCl after a meal requires parietal cells to be stimulated by all 3 substances - gastrin; into blood to stimulate HCl secretion & pepsinogen - histamine; acts as a paracrine hormone; HCl secretion
32
Inhibition of gastric secretion
-signals from duodenum if pH drops too low; blocks further HCl secretion
33
Degradation through stomach
Proximal; recently swallowed food - enzymes act; amylase Distal; food is well mixed -HCl -Pepsin
34
Factors affecting stomach emptying
- Expansion of stomach wall - gastrin - Distention of duodenum; as D fills pyloric sphincter closes slowing chyme from S to I -High fat and protein conc. - Reduced pH
35
The Abomasum
- Epithelial glands produce pepsinogen and HCl - Young ruminants also produce rennin for milk digestion -NOT storage organ - low pH
36
What are the two types of small intestine contraction?
Segmentation Peristalsis
37
Segmentation (SI)
Mixing movements/contractions Non-propulsive
38
Peristalsis (SI)
Propulsive movements, moves chyme through intestines
39
Movements during the interdigestive period
Propulsive movements Sweeps the intestine clean between meals Between periods of peristaltic contraction gets rid of bacteria
40
Pacemaker cells in the small intestine
INTERSTITIAL CELLS OF CAJAL (ICC) - Modified smooth muscle cells - Slow waves constantly - Muscle contractions only occur at same or lesser frequency than slow waves
41
What structures in the small intestine increase surface area?
1) Folds in the inner surface of intestine (mucosa) 2) Mucosa covered in villi 3) Villi have microvilli
42
Enterocyte structure
- Apical membrane; contact with intestinal lumen - Tight junctions (loose); connect adjacent enterocytes
43
2 Mechanisms of absorption from SI
Transcellular; organic nutrients transported from intestine to interstitial fluid across enterocytes Paracellular; inorganic ions & water can diffuse through tight junctions
44
4 types of large intestine contraction
- Segmentation - Peristalsis - Anti-peristalsis - Mass Movements
45
Segmentation (LI)
- Haustra formed - Movement of content back and forth
46
Antiperistalsis
Increase transit time; delaying transit of chyme filling the caecum
47
Pelvic flexure
- narrow portion between ventral and dorsal colon in horses - Similar function to a sphincter - large particles cannot pass through
48
Mass Movements
-Produce faeces - Then peristaltic contractions of the rectum follow to defecate.
49
Diarrhoea
An increase in defecation frequency or fecal volume - results in disturbed balance between influx and efflux
50
Malabsorptive diarrhoea
Occurs when absorption is inadequate to recover a sufficient amount of secreted water - can be caused by infection - causes loss of epithelium and aquaporins
51
Hypersecretory diarrhoea
- occurs when rate of intestinal secretion increases and overwhelms absorptive capacity
52
How does E. coli and Salmonella cause diarrhoea?
Causes Hypersecretory diarrhoea - produces enterotoxins - bind to the epithelium and causes cAMP activity causing the opening of chloride channels - causes water and electrolytes to be secreted from crypt epithelium

Structure & Function 2 (16 decks)

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