L4: Motility and Secretions of the GIT Flashcards Preview

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

List the 4 main functions of motility

 

  • 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

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

Describe proximal stomach gastric motility

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

3

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

Motor output occurs via..?

  • 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

Describe the importance of mastication

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

5

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

Describe distal stomach gastric motility

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

6

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

Describe gastric emptying

  • 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

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

Describe small intestine motility

  • Two phases
    -1. During digestive  period after food intake
    -2. 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

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

Describe forestomach (rumen) motility
-Pillars

  • Pillars divide rumen
    -enable mixing & controlled movemen of lrg fluid volumes
    -help stabilise fluid contents of reticulorumen & limit movement of digesta towards reticulum

9

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

Describe forestomach (rumen) motility
-primary contractions

  • 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

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

Describe forestomach (rumen) motility
-secondary contractions

  • 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

Describe the importance of reticulorumen motility in maintaining a favourable environment

 

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

12

Describe the process of rumination & its importance to digestion

 

  • 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

List & ID the types & origins of the GIT secretions

Salivary

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

14

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

  • 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

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

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

16

List & ID the types & origins of the GIT secretions

Gastric

  • 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

List & ID the types & origins of the GIT secretions

Pancreatic

  • 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