Ruminant Abdomen - Lecture 157

Ruminant Abdomen - Lecture 157

1. Describe the topography of the ruminant abdomen and the position of the omenta in the adult

A: cutaneous trunk line m.
     - loosely arranged through fat tissue
     - thicker in ruminant and horses
     - can 'flick' to get flies off

B: external oblique m.

C: internal oblique m.

D: transverse abdominus m.
and rectus abdominus m.

Aponeurosis of external, internal, transverse muscles come together to form rectus sheath - facial sheath covering rectus abdominus m.
Left side: 

Right side: 

• Access to abdomen should be made through the left side, as the greater omentum covers a lot of the right side
• Order of digestion: 
• oesophagus
• rumen/reticulum (act together)
• omasum
• abomasum
• duodenum
• jejunum
• ileum
• caecum (limited)
• ascending colon (coiled)
• transverse colon
• descending colon (dorsocaudal)

Omenta: 

2. Describe the adult form of the ruminant stomach and intestinal tract

Rumen: 

Longitudinal groove/pillar - divides dorsal/ventral sac

Sheep - caudodorsal sac is much smaller than cow (dorsal region is smaller than ventral) 

Papillae - increase surface area

Reticulum: 

• Papillae very different from rumen although almost the same function
• next to diaphragm/heart
• hardware disease - weight of hardware causes it to drop straight into reticulum, next to diaphragm and possibly paracardium

Omasum: 

• wall foldings increase surface area
• 'leaves' of a book
• covered in papillae to absorb fluid
• foldings help 'squeeze' to get fluid out for absorption - like milking
• needs a lot of saliva from ruminating
• cow produces ~ 200 l saliva per day  
• saliva also for pH buffering

Absomasum: 

• full of rugi - folds in wall
• for absorption
• omasum empties in omasoabomasal opening. Sphincter muscles control. ~2 cm diameter
• torus - muscular thickening near pyloric sphincter

Bloody supply to stomach: 

• Celiac artery - all of foregut
• Splenic artery to spleen
• Very muscular stomach, needs a lot of blood
• also needed for fluid reabsorption and food absorption

Intestines: 

• duodenum is attached to the mesentery
• caecum - caudally projected
• common to have it flip over when filled with gas
• access via right paralumbar fossa
• Ascending colon is spiral shape
• 2.5 turns in - centrapedal - ansa proximalis
• 2.5 turns out - centrafugal - ansa distalis
• attached to the mesentery
• Cone shape in sheep/goats
• flat in bovine
• transverse colon
• not attached to mysentry
• descending colon
• attached to short mesocolon
• unsacculated

Liver: 

• lies mostly on right side - barely crosses midline
• not very lobed compared with dog

3. Describe the position of the ruminant liver, pancreas and spleen

Liver: 

• lies over reticulum, omasum, duodenum, gallbladder and pancreas
• lies mostly on right side - barely crosses midline

Pancreas: 

• runs along liver near dorsal body wall
• has L-shaped structure
• right lobe runs craniocaudally
• only one duct that drains into duodenum (rum)
• cow - lesser duct (separate from bile duct)
• sheep - 1 duct at same place as bile duct

Spleen: 

• lies on left side on top of rumen
• distinct hilus in ruminant (at 'top' of spleen)

                       

4. Describe the development of the ruminant stomach.

A.
- Gut tube dilates
- extra bumps on ruminant stomach

B. 
- Cranial region develops out





C. 
 - Cranial region flips over (with greater omentum)

D. 
- Cranial region flips over completely
- Now it faces caudally
- Greater omentum is around longitudinal groove and abomasum


Calf Stomach: 

• very small rumen
• big abomasum
• rumen not needed - milk is digested in abomasum
• no fermentation until weaning and then rumen develops

Gastric groove - reticular/oesophageal groove

• groove that forms incomplete channel to avoid rumen, reticulum
• muscular 'lips' guide milk straight to omasum/abomasum
• goes away as calf grows
• calf needs to stretch throat for best results