L4: Motility and Secretions of the GIT Flashcards
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
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
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
Describe the importance of mastication
- FIRST ACT OF DIGESTION
- initiates mechanical breakdown
- moistens, LUBRICATES
- stimulates secretion of saliva, gastric/pancreatic juices, bile
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
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
Describe the motility patterns of different sections of the GIT & explain the benefits of these patterns
Describe small intestine motility
- Two phases
- During digestive period after food intake
- 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
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
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
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
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
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)
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
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
What is the differences of ruminant saliva when compated to monogastric saliva?
- lrg v produced
- isotonic
- > pH
- > [] bicarbonate
- > [] phosphate (buffer)
- > [] Na+ (osmolarity)
