L4: Motility and Secretions of the GIT Flashcards Preview

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Flashcards in L4: Motility and Secretions of the GIT Deck (17)
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1
Q

List the 4 main functions of motility

A
  • 1. Propel ingesta along tract
  • 2. Retain ingesta @ given site (enables digestion, absorption or storage to occur)
  • 3. Physical breakdown of food & mixing
  • 4. Circulate ingesta. > contact w/ absorptive mucosal surfaces
  • Motility can be repulsive, retentive, breaking down or mixing in nature
2
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe proximal stomach gastric motility

A
  • reservoir to store & digest
  • wall undergoes receptive & adaptive relaxation to accomodate meal
  • contractions push digesta
3
Q

What are the two kinds of neural control on the GIT?
Sensory input occurs via..?

Motor output occurs via..?

A
  • Intrinsic or enteric control w/in walls of gut
  • Extrinsic autonomic NS
  • Sensory input via
  • chemorecpt. in mucosa
  • mechano in muscular layers
  • Motor output via
  • stimulatory/inhibitory neurons
  • Hormones also have large effect
4
Q

Describe the importance of mastication

A
  • FIRST ACT OF DIGESTION
  • initiates mechanical breakdown
  • moistens, LUBRICATES
  • stimulates secretion of saliva, gastric/pancreatic juices, bile
5
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe distal stomach gastric motility

A
  • Peristaltic waves move digesta along
  • grinding, mixing & emptying function
  • constricted pylorus only lets sml particles through <2mm
6
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe gastric emptying

A
  • neural response initiates hormonal response. -VE FEEDBACK
  • Reflexes control gastric emptying by regulating stomach motility
  • Rate of flow => rate of food leaving stomach must = rate of digestion & absorption by SI
7
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe small intestine motility

A
  • Two phases
    1. During digestive period after food intake
    1. During interdigestive period when there is little food in gut
  • Digestive phase has 2 motility patterns:
  • Propulsive: peristaltic contractions that move down gut
  • Segmentation: mixes digesta w/ juices & moves it over digestive mucosal surfaces
8
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe forestomach (rumen) motility
-Pillars
A
  • Pillars divide rumen
  • enable mixing & controlled movemen of lrg fluid volumes
  • help stabilise fluid contents of reticulorumen & limit movement of digesta towards reticulum
9
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe forestomach (rumen) motility
-primary contractions
A
  • Primary contractions = mixing
  • start in reticulum, 1-3 p/min
  • reticular V < by 50%, forces coarse material from top of retic. to atrium & dorsal parts
  • 2nd retic. contraction almost empties retic. of fine material
  • dorsal/ventral sac contractions (circular movement), mix well w/ digested material

-moves back/forth to/from reticulum, eventually into omasum

10
Q

Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns

Describe forestomach (rumen) motility
-secondary contractions
A
  • secondary contractions = eructation
  • forces fermentation gases cranially
  • dorsal rumen contraction waves reach atrium, cranial pillar elevates, moves fluid away from oesophagus, gas enters & leaves mouth
  • methane (CH4) and CO2 eructated
11
Q

Describe the importance of reticulorumen motility in maintaining a favourable environment

A
  • mixing
  • rumination (further breakdown of plant material)
  • eructation of toxic gases (ch4 & co2)
  • absorption of nutrients
12
Q

Describe the process of rumination & its importance to digestion

A
  • 1. Regurgitation
  • short (2-4s) reticular contraction
  • recently ingested material near oesophageal opening replaced by semi-liquid, partially fermented material
  • lower pressure in thorax sucks material into oesoph. antiperistaltic waves propel cud into mouth
  • 2. Re-mastication
  • re-insalivation
  • Re-swallow (re-deglutition)
13
Q

List & ID the types & origins of the GIT secretions

Salivary

A
  • 3 main glands
  • parotid
  • mandibular
  • sublingual
  • 2 types of saliva secretion
  • serous (thin, watery) from parotid
  • viscous (mucus rich) from sml glands
14
Q

What are the functions of saliva, and what does it contain?

A
  • LUBRICANT. Also:
  • antibacterial
  • digestive, solvent
  • evaporative cooling
  • aids taste
  • Contains:
  • 98% H2O
  • mucin: forms mucus, lubricates
  • amylase: enzyme which converts starch => disacc. maltose. NOT in ruminants
  • Bicarbonate: neutralises acids
  • lysozyme & antibodies: antibacterial
  • urea: important N source for protein synth. in ruminants
15
Q

What is the differences of ruminant saliva when compated to monogastric saliva?

A
  • lrg v produced
  • isotonic
  • > pH
  • > [] bicarbonate
  • > [] phosphate (buffer)
  • > [] Na+ (osmolarity)
16
Q

List & ID the types & origins of the GIT secretions

Gastric

A
  • Major SA of stomach & lining of pits covered w/ surface mucous cells
  • produce thick mucus, important to protect stomach epithelium from acidic cond. & abrasion
  • mucus is > protein & > sugar
  • produced by crypt & surface epithelial cells
  • contains:
  • glycoproteins & mucopolysaccherides
  • Protection against HCL & pepsin, but this req. bicarb & continuous mucus synth
  • low pH (2) in lumen provides barrier against microorganisms & endotoxins
17
Q

List & ID the types & origins of the GIT secretions

Pancreatic

A
  • Exocrine portion secretes pancreatic juice
  • very alkaline (> bicarb)
  • important for monogastrics
  • acinar cells: digestive enzymes
  • duct cells: aqueous NaHCO3 solution
  • Endocrine
  • hormones, insulin, glucagon, islets of langerhans
  • Main types of enzymes:
  • proteolytic: protein dig.
  • pancreatic amylase & chitinase: CHD dig
  • pancreatic lipase: lipids