Flashcards in Digestion 4 Deck (107)
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1
ruminants and herbivores association
all herbivores ruminate but not all herbivores are ruminants
2
ruminant motility - what type of contractions occur which one more important
Intrinsic contractions
- consist of low amplitude waves travelling in the smooth muscle wall of the reticulo-rumen
- occur even when the nerves to the reticulo-rumen are severed
- Limited in ruminants as very localised contractions - not across the whole rumen - occurs more in the abomasum
Extrinsic contractions
- occur only when the vagal or splanchnic nerves are intact - main one for ruminants
- Initiated by a burst of activity in the vagal nerves - which originate in the gastric centres of the medulla
- Main contractions within the rumen so if cut vagal nerves then paralysed rumen essentially
3
oesophageal groove what formed from and between what openings
- Specialised region of the reticulum which is formed from reticular and omasal smooth muscle and oesophageal muscles.
- can be formed into a tube between the oesophageal orifice and the reticulo-omasal orifice, by contraction of the muscles forming the two lips
4
How to move material from dorsal sac rumen into the retirculum and steps in regurgitation and what makes the animal stop chewing
contract rumen-reticular pillar (lower it) and fluid will flow into reticulum
1) The material will be in the raft that flows into reticulum then all you have to do is raise the liquid level in the reticulum up until the rough raft is level with oesophageal opening
2) Will now be aligned with the oesophageal opening so reflex opening
3) Tense the abdominal muscles
4) Breath in against closed glottis - lower pressure in oesophagus - material move into the oesophagus
5) once in oesophagus reverse peristalsis
- possible that chew until buccal receptors detect that particles are smaller than when brought up once finished fall back into reticulum
5
steps in moving food from reticulum to the omasum and step in eructation
1) Rough stuff floating on top and fine stuff on the bottom
- Know how fine the material is by mechanoreceptors in the reticulum lining - detect no rough stuff then can move onto step 2
2) Close oesophageal opening and raise the liquid level up by contracting base of reticulum
3) Get the liquid level with omasal orifice then relax omasal orifice then material will flow in and will be the finest material if you raise the liquid level up high enough
open the oesophageal sphincter and allow gas pressure to send the gas up the oesophagus
6
what are the 4 main functions of the parotid gland
1) Recycling salt absorbed from gut
2) Recycling water from gut
3) Maintaining the pH (7.4) of the reticulo-rumen
4) Maintaining an optimal electrolyte concentration in the reticulo-rumen
Effectively reduces the amount of water and electrolytes which have to be ingested by recycling
7
Name the 6 ruminant families and which one doesn't ruminate
Tragulidae, Giraffidae, Cervidae, Moschidae, Antilocapridae, and Bovidae
Tragulinidae - mouse deer primiative with 3 stomachs dont ruminate
8
List 10 characteristics of ruminants
1) a complicated four-chambered stomach.
2) no incisors on upper jaw
3) a long diastema
4) incisor-like lower canines.
5) metapodial limb bones fused into a single, elongated cannon bone.
6) Large fermentative fore-stomach.
7) High yield metabolism of low-nutrient yield food - utilise ethanol as a food source - bi-product from micro bacteria which also produce a lot of methane
8) Water and electrolyte conservation mechanisms.
9) Control of complex digestive systems - rumen movement goes caudally and cranially
10) Control of complex digestive behaviours: – Rumination.
9
origin of ruminants
- Assume evolutionary advantage in being a ruminant over ordinary herbivore
- Possibly the competition for reducing niches increased the chances of those animals with enhanced fermentation to do better than those without.
- Progressive development of more and more complicated digestive systems which increased the “yield” from poor quality food as rumination increases the efficiency of digestion
10
strengths of ruminants - list 6
1) able to cope with diverse climatic conditions
2) efficient conversion of low quality feeds
3) great tolerance of dry conditions due to water and salt conservation in the rumen
4) reasonable reproductive capacity - twins
5) very rapid post-partum mobility - within few hours of birth high capability
6) capable of traveling extreme distances
11
weaknesses of ruminants - list 6
1) birth-weight high
2) limited defenses beyond size and social behaviour
3) prolonged digestive processes - long time for nutrients to be available for the animal
4) require large areas of pasture for grazing
5) complicated digestive process can be disrupted
6) susceptible to parasite infection
12
gastric secretion - what is secreted and from what cells and from where in the stomach
1) acid HCl - from parietal cell - fundic - gastric pits
2) pepsinogen (activated at low pH to pepsin - from chief cell - fundic
3) mucus - from surface mucosal cell and mucous neck cell
13
characteristics of parietal cell
- huge membrane surface area
- secretory canaliculus
- tubulovesicles - within cell and become microvilli when secreting
- dense with mitochondria
- has a membrane lined H/K ATPase (proton pump) that actively secretes H+ into lumen
14
differences between resting and secreting parietal cell
when resting have canaliculus that is small without microvilli as they are tubulovesicles that are within the cell
when secreting canaliculus moves deeper into cell and exposes microvilli on the surface which start secreting acid
15
what enzyme is involved with making the H+ within the parietal cell and how does it work
Carbonic anhydrase
produces - Carbonic acid and H+ from CO2 - bicarbonate secreted out of cell into interstitular space and exchanged for chloride which is passively secreted, H+ is secreted through proton pump
16
how is gastric acid secretion controlled
the one cell and two cell theories
One cell - Parietal cell can respond directly to vagus (ACh) and gastrin stimulation
Two cell - Mast cell/EC (enterochromaffin) cell releases histamine in response to gastrin or vagus (ACh) stimulation which acts on the parietal cell to release H+
Also - prostaglandins act directly on parietal cell to block the hydrogen pump
17
stimuli for acid release - the different phases and what stimuli
1) cephalic phase: - stimuli coming from the head
- Sight/ smell of food
- Chewing/ taste of food
2) Gastric phase - stimuli from the stomach
- Stretch
- Mechanical stimulation
- Protein in stomach
- Certain drugs (eg caffeine)
3) Intestinal phase - stimuli from the intestines
Protein in intestine - suggests more digestion needs to occur in stomach
18
what phases are nerves involved in and what hormones are involved in gastric acid release and their actions
vagus nerve with long reflexes
cephalic phase
gastric phase
hormones
- Gastrin - excitatory
- Secretin - inhibitory
- Gastric inhibitory peptide - inhibitory
- Cholecystokinin - inhibitory
19
what is the source of the following enterogastrones
gastrin, histamine, secretin, cholecystokinin, gastric inhibitory peptide
1) GASTRIN from G cells in pyloric antrum & duodenum
2) Histamine from EC cells in lamina propria of stomach
3) SECRETIN from S cells in duodenal mucosa
4) Cholecystokinin from EC cells in intestinal wall
5) Gastric Inhibitory Peptide from EC cells in intestinal wall
20
Ways in which the gastric mucosa protects against ulceration and where problems can occur
1) gastric mucus secretion
2) gastric bicarbonate secretion
3) epithelial cell turnover - lifespan 3-4 days and upward migration and replacement
4) gastric mucosal blood flow - wash away HCl - when in ICU circulatory shock reduce cardiac output reduce capacity to wash away H+
5) tight junctions between cells - lateral walls not protected by layer so important and gastric ulceration can occur
6) abundant mucus secretions from surface mucosal cells (glycocalyx layer) and mucus neck cell
21
Helicobacter pylori what does it do, why is it an issue
bacteria that destroys gastric barrier and creates ulceration - human now given antibiotics against
22
what are the 3 classes of drugs that are involved with gastric acid secretion
1) drugs that suppress acid secretion - H2 receptor antagonists and proton pump inhibitors
2) cytoprotective drugs - prostaglandin analogues and sucralfate
3) antacids
23
name the two class of drugs that suppress acid secretion and how they do it
1) H2 receptor antagonists: - Histamine receptor type 2 - receptor found in stomach and heart
– Important drug- drug interactions involving liver metabolism and cytochrome p450 enzyme (these interactions also occur with grapefruit juice and alcohol!)
2) Proton pump inhibitors
– Irreversibly block active transport of H+ ions - persistent in action
– Used for unresponsive gastric ulcer
– Are tending to replace histamine antagonists
24
what are the two class of drugs in the cytoprotective drug class and what they do
1) Prostaglandin analogues (synthetic prostaglandin) - as prostaglandins turn off acid secretion
– Increased mucus secretion, increased blood flow, increased cell turnover
– Decreased acid secretion
- Used when risk of gastric ulceration - ICU - reduced blood supply - Jack the Dog case-study
2) Sucralfate
– Sucrose octosulfate and aluminium hydroxide - ulcer band-aid - sticks to lesion and provides protection and neutralisation
– Dissociates --> sticky adherent gel + neutralising agent
25
antacids how do they work, what do you use and what medicine used in
• Act to neutralise hydrochloric acid, bind bile acids and decrease pepsin activity
• Provide symptomatic relief
• Generally contain AlOH, CaCO3, Mg(OH)2, N
HCO3
• Mg--> increased bowel motility,
• Al---> decreased bowel activity
Use together
• Used only in human medicine
26
what is the intestine in the dog and cat divided into and how to distinguish the two parts. what is the end of the small intestines called
proximal small intestine and distal large intestine distinguished by presence of blind diverticulum - the caecum at end of small and start of large
ileo-colic orifice - start of colon
27
What are the 3 parts of the small intestine and the large intestine in the dog and cat
small
1) initial duodenum
2) jejunum
3) ileum
large
1) proximal blind ending caecum
2) colon
3) rectum
28
List the 4 external features of the duodenum for cats and dogs
1) cranial flexure
2) descending portion
3) caudal flexure
4) ascending portion
29
cranial flexure what does it run along and what separates it from the stomach for cats and dogs
runs from the pylorus, passes dorsally and right against the visceral surface of liver
ventrally separated from the stomach by greater omentum
30