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how much does the compound stomach of ruminants take up

3/4 of the abdominal cavity - fills almost the entire left half of the abdominal cavity and squashed intestines to the right


what are the four compartments of the compound stomach of ruminants and group them into glandular and non-glandular

The fore-stomach (or proventriculus) which is non glandular -
- Rumen -
- Reticulum -
- Omasum -
The Abomasum which is glandular - monogastric type digestion


what occurs in terms of the compound stomach from milk to forage diet

- At birth, the abomasum is the largest compartment - on the milk diet not forage so much more like monogastric, don't need large amount of bacteria to get nutrients; In the adult, the rumen is the largest


Reticulum where located in the abdomen and where will illicit pain response

Lies on the left side, opposite the 6th to 8th ribs; it is the most cranial compartment
- The reticulum reaches from the cardia to the most forward part of the diaphragm and occupies the full height of this shallower part of the abdomen.
lies above the xiphoid process of the sternum. External pressure applied in this position will elicit a pain response in cases of reticulitis (inflammation of the reticulum).


what does the internal surface of the reticulum look like and its function and what occurs when sharp objects fall into stomach

Has honeycomb areas with papillae - holds onto longest ends of fibres so with forcible contraction thrown back into rumen so can be further digested, the smooth paste like substances can move through the hole to the omasum
Sharp objects ingested fall into reticulum, if sharp can poke through the wall and into the diaphragm on the other side is the heart which can pierce the heart - traumatic reticuloperitonitis - can present as heart failure


list and describe the 3 opening in the reticulum

1) Cardia - is the slit like opening of the oesophagus positioned at the junction of the rumen and reticulum and opens into both chambers.
2) Ruminoreticular orifice - wide opening between the rumen and reticulum which communicate over the U-shaped ruminoreticular fold - separate reticulum and rumen (pillars)
3) Reticulo-omasal orifice - round exit into the omasum at the lower end of the reticular groove


functions of the reticulum

o Serves as a sieve for coarse material
o Absorbs fatty acids, water, salts, etc.
o Passes coarse material back to the rumen and fine material to the omasum by very forceful contractions.


correlation between treatment of bloat and dorsal sac of rumen

can use rumen - left fland area to palpate and relieve gas from dorsal sac


what are the two curvatures of the external rumen

o Dorsal curvature - is firmly attached to the sublumbar muscles on the left by peritoneum and connective tissue as far caudal as the 4th lumbar vertebrae.
o Ventral curvature - lies on the floor of the abdomen with the superficial wall of the omental bursae between.


describe the two surfaces of the rumen

1) parietal or left surface - right up against the body wall - convex - related to diaphragm has superficial wall of greater omentum between ventral sac and abdominal wall
2) visceral or right surface - right up against internal organs - has many grooves denoting the different sacs


List the 11 grooves found in the rumen

1) cranial
2) rumino-reticular
3) right longitudinal
4) left longitudinal
5) right accessory
6) left accessory
7) right dorsal coronary
8) left dorsal coronary
9) right ventral coronary
10) left ventral coronary
11) caudal


where does the cranial and rumino-reticular groove go to and from and the function in rumen

Cranial groove - transverse groove that divides the cranial end of the rumen into the cranial sac (ruminal atrium) and the cranial end of the ventral sac
o Rumino-reticular groove - is the line of separation between the ruminal atrium and the reticulum. It is deep ventrally but dorsally the wall of the reticulum and the rumen are continuous and form the dome-like ventricular atrium on which the oesophagus terminates. Muscular fold


where does the left/right longitudinal, left and right dorsal and ventral coronary and caudal groove go to and from and the function in rumen

longitudinal grooves - extend from the cranial to caudal grooves and indicate the division of the rumen into dorsal and ventral sacs.
coronary grooves - demarcates the caudodorsal blind sac from the dorsal sac - curve
ventral coronary grooves same thing but ventral
caudal groove - deep transverse groove that divides the rumen into the caudodorsal and caudoventral blind sacs


what is the Ruminal atrium and Tympany

Ruminal atrium is that part of the rumen caudal to the rumino-reticular fold.
when rumen is filed with gas


groove and pillars relationship

internally the grooves correspond to bands of smooth muscle known as pillars. These pillars bear the same name as the grooves: Form the different sacs


papillae of the rumen, where present and what stimulates the development of them

- not found on the pillars
- Are long and numerous in the ventral and dorsal caudal blind sacs.
- Fewer and less prominent in the ventral sac.
- Are short or absent on the roof of the dorsal sac - due to the presence of gas bubbles resulting from fermentation.
Volatile fatty acids stimulate development of papillae.


functions of the rumen and the papillae

o Ruminal contractions (waves of contractions caudally) mix the ingesta and furthers the process of microbial fermentation releasing volatile fatty acids and gases - coordinated to push gas into oesophagus (eructation)
o The absorption of volatile fatty acids, sodium, water, etc.
o Papillae increase the surface area for absorption and assist mixing of ingesta.
o Papillae also serve as heating rods for speeding up the fermentation process.
o Rumination and eructation. Rumen gas - gas cap normal - left paralumbar fossa (last few ribs) where gas sits


the omasum what curvatures does it have, where attached to the abomasum and what is it covered with

greater and lesser curvature
o Lower pole of the omasum has an extensive attachment to the fundic region of the abomasum around the omaso-abomasal orifice.
o Much of the right surface of the omasum is covered by, and is partly connected to, the lesser omentum - between true stomach and the liver


what are the two openings of the omasum

1) Reticulo-omasal orifice is at the upper end of the omasal canal.
2) Omaso-abomasal orifice at the lower end of the omasal canal is large and oval and partly obscured by the prolapse of the abomasal folds.


what is the omasal groove and omasal laminae in the omasum

Omasal groove -
Runs between the two openings and is in fact the floor of the omasal canal.
Mucosa in this region is smooth except for a few low longitudinal ridges.
Omasal laminae - or leaflets
Many parallel folds of four different sizes that fill the omasum.
Arise from the sides and greater curvature and project towards the lesser curvature - site of the omasal canal.
Lots of smooth muscle - two types in longest folds - 1. inner portion tunica muscularis 2. differentiates mucosa from sub mucosa - lamina muscculars mucosa


what is the interlaminar recess, omasal canal of the omasum
Where are papillae and what type

Interlaminar recesses - spaces between the folds.
Omasal canal - central area not occupied by folds.
Papillae – The mucosa forms numerous projections or papillae that cover the surface of the laminae. Most are small and somewhat flattened but there are a few large conical projections.


functions of the omasum

o Absorbs fatty acids, water, salts.
o Serves as a two-stage pump for transfer of ingesta from the reticulum to the abomasum.
o It is a sieve for quality control separation - lots of folds


what problems can arise with the abomasum

abomasal displacement - left or right occurs often in dairy cows as it is not well attached


what are the two poles of the abomasum

o The larger cranial pole:
- Forms a pear-shaped sac equated with the fundus and body of the simple stomach - Connected by muscle bundles to the reticulum, ruminal atrium and the ventral sac of the rumen.
o The narrower caudal pole:
- Forms the pyloric region. This passes transversely to the right; Terminates at the pylorus just caudal to the lower part of the omasum


what are the two opening of the abomasum

Omaso-abomasal orifice
Pylorus - opens into the duodenum


spiral folds of the abomasum where do they arise, how are they coordinated, their function

spiral folds that arise around the entrance and course over the walls of the fundus and body, decreasing as they approach the flexure
they serve to increase the mucosal surface area. In the region of the omasal-abomasal orifice these folds help to form a mucosa "plug" that limits reflux of ingesta into the omasum.


structure of the wall in the compound stomach

o Mucosa - is smooth pink and glandular; a thick muscularis mucosa is present
o Submucosa
o Muscularis externa - smooth muscle thicker inner (circular around length of organ) and a thin outer (longitudinal outer length) layer.
o Serosa is absent from the surface only along the origin of the omentum


function of the abomasum

Is rich in glands that produce digestive enzymes and HCl for digestion and mucus for protection.


torus - where is it what does it do

abomasum - The lighter mucosa of pylorus bears a few low rugae but is marked by a large swelling that projects from the lesser curvature to narrow the pyloric passage. The vascular structure of the torus suggests it is capable of engorgement, but its functional significance is unknown.


oesophageal groove what is its function and the 3 segments

Serves as a conduit for conveying milk from the oesophagus into the abomasum without having to go through the rumen
1) Reticular groove -
- From the cardia to the reticulo-omasal orifice
- Bounded by two prominent muscular folds
- It is open along its left side facing the cavity of the reticulum and rumen
- Muscular folds roll into a tube when a young animal drinks milk
2) Omasal groove -
- From reticulo-omasal orifice to omaso-abomasal orifice on floor of omasum
- Muscular folds are not very prominent
- It is open along its right side facing the cavity of the omasum
3) Abomasal groove -
- Not a proper groove, just an area without gastric folds
- It extends along the lesser curvature of the abomasum