Ruminant Anatomy + Physiology Flashcards
What are the 4 chambers of the ruminant stomach?
Reticulum, Rumen, Omasum, Abomasum
What type of stomach do ruminants have - simple or complex?
Complex
What is rumination?
When an animal regurgitates previously consumed food and chews it further and re-swallows.
What is eructation?
The release of gas produced by fermentation from the stomach or oesophagus through the mouth.
Name 2 examples of pseudo-ruminants.
Camelids, hippopotami
Explain the function of the 3 compartments of a pseudo-ruminant forestomach
(C1,2,3)
C1 = essentially a fermentation vat
C2 = some nutrient absorption occurs
C1&2 -> rhythmic contractions then eructation and regurgitation
C3 = “true stomach” distal part secretes HCl
What makes the reticulum so distinctive?
Honeycomb structure covered in short papillae.
What sort of mucosa and epithelium does the reticulum have?
Non-glandular mucosa lined by stratified squamous epithelium.
What type of mucosa and epithelium does the rumen have?
Non-glandular - keratinised stratified squamous epithelium.
What is the internal parallel laminae of the omasum?
Thick muscular sheets covered with non-glandular mucosa, which form short papillae.
Why is the abomasum known as the ‘true’ stomach?
It is the only glandular region of the stomach
What sort of epithelium does the abomasum have?
Simple columnar
What is the origin and insertion of the external abdominal oblique in ruminants?
Origin
Costal part - outer surface of the last 8 ribs
Lumbar part - last rib and thoracolumbar fascia
Insertion
Via aponeurosis onto the linea alba and pre-pubic tendon. Fibres run caudoventrally
What is the origin and insertion of the internal abdominal oblique in ruminants?
Origin
Tuber coxae and the pelvic tendon of the EAO and transverse processes of the lumbar vertebrae
Insertion
Via aponeurosis onto the linea alba and last rib forming external lamina of rectus sheath. Fibres run cranioventrally.
What is the origin and insertion of the rectus abdominus in ruminants?
Origin = Xiphoid process and ventral aspect of last 10 ribs
Insertion = Cranioventral pubic brim
Fibres run craniocaudally.
Why are the intestines and liver located on the RHS in ruminants?
The development of the rumen pushed the intestines and liver entirely to the right half of the abdomen.
How many lobes does a ruminant liver have compared to a dog liver?
Dog = 6 lobes
Ruminant = 4 lobes (Left and right hepatic lobe, quadrate lobe and caudate lobe)
Discuss the process by which mixing contractions occur.
1) Contractions start in reticulum and move caudally along rumen as a peristaltic wave.
2) Reticular muscle contracts twice in 5-10 sec with brief pause.
3) Contraction forces coarse fibrous material from top of reticulum to contral and dorsal rumen.
4) Completely empties reticulum of finely-dispersed well-fermented content from lower portion
5) Rumen contracts - starts in cranial sac and passes dorsally and caudally in dorsal rumen sac moving ingest into the caudodorsal blind sac. Contraction of caudodorsal sac forces content cranially.
Discuss the process of rumination
1) Hydrostatic pressure difference between the oesophagus and reticulum draws reticular content into oesophagus.
2) Anti-peristaltic contractions in the oesophagus propels bolus into oral cavity.
3) Fluid fraction re-swallowed whilst rest of bolus masticated before being re-swallowed.
4) Increased saliva secretion increases fluid and ions delivered to reticulorumen.
Secondary contractions = rumen contractions associated with eructation.
Discuss the process of the secondary contraction.
1) Contractions start in the caudal blind sacs and move cranially along the dorsal sac.
2) Gas cap pushed towards oesophageal opening
3) Negative intra-thoracic pressure draws gas into oesophagus when sphincter opens.
4) Gas passes to mouth via anti-peristaltic waves.
How are contractions regulated in ruminants?
Long reflexes mediated by the vagus nerve
Short reflexes mediated by enteric nervous system within myenteric and submucosal plexus.
