Ruminant anatomy and physiology Flashcards
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What are the four chambers of the ruminant stomach and which are non-glandular and which are glandular?
- reticulum
- rumen
- omasum
= non-glandular - abomasum
= glandular
What are foregut fermenters?
- digestive process in which plant material is fermented in a specialized combination of stomach compartments
What is rumination?
- animal regurgitates previously consumed food and chews it further and re-swallows
What is eructation?
- release of gas produced by fermentation from the stomach or oesophagus through the mouth
What are pseudo-ruminants?
- like ruminants use foregut fermentation but have 3 compartments instead of 4
- camels and hippos
What do the three compartments of the pseudo-ruminant stomach do?
- C1 - essentially a fermentation vat
- C2 - some nutrient absorption occurs
- rhythmic contractions then eructation and regurgitation
- C3 - true stomach - distal part secretes HCL
Where does the reticulum lie?
- lies cranial to the rumen under the 6th-8th ribs
- lies up against the diaphragm
What distinct feature does the reticulum have?
- distinct honey comb structure covered in short papillae
The rumen and reticulum are often together - what is their joint term?
- reticulorumen
What lines the reticulum?
- non-glandular mucosa lined by stratified squamous epithelium
What lines the rumen?
- non-glandular mucosa
- keratinised stratified squamous epithelium
What in the rumen increases the surface area 7-fold?
- papilla present formations of the lamina propria and submucosa
What layer is not present in the rumen?
- muscularis mucosa is absent
Where are papillae not present in the rumen?
- not present over the centre of the roof or the free margins of the pillars
Where does the omasum lie?
- lies within the intrathoracic part of the abdomen to the right of the reticulorumen
How are short papillae formed in the omasum?
- internal parallel laminae - thick muscular sheets covered with non- glandular mucosa forms papillae
Where does the muscularis mucosa extend into in the omasum?
- extends into the laminae
What is the abomasum?
- the true stomach with glandular mucosa containing gastric glands and pyloric glands
What covers the abomasum?
- simple columnar epithelium
What increases the mucosal surface area if the abomasum?
- mucosal surface area increased by large folds which do not disappear when the stomach distends
The muscularis externa (found in the abomasum) is comprised of what?
- inner circular layers
- outer longitudinal layers of smooth muscle
In calves what prevents milk from entering the rumen (which isn’t fully developed)?
- oesophageal groove = muscular folds of the reticulorumen
What are new-born calves described as?
- pre-ruminants
What is the transition phase in calves?
- from pre-ruminant to ruminant
During the ruminant phase was is the sole source of feed?
- dry feed
The rumen accounts for how much of all stomach compartments?
- 70%
What muscles make up the abdominal wall?
- cutaneous trunci
- external abdominal oblique
- internal abdominal oblique
- transversus abdominus & rectus abdominus
What is the origin of the external abdominal oblique?
- costal part - outer surface of the last eight ribs
- lumbar part - last rib and thoracolumbar fascia
Where does the external abdominal oblique insert?
- via aponeurosis onto the Linea alba and pre-pubic tendon
How do the fibres run in the external abdominal oblique?
- caudoventrally
What is the origin of the internal abdominal oblique?
- tuber coxae and the pelvic tendon of the EAO and transverse processes of the lumbar vertebrae
Where does the IAO insert?
- via the aponeurosis onto the Linea alba and last rib forming the external lamina of rectus sheath
How do IAO fibres run?
- cranioventrally
How is the caudal border of the paralumbar fossa formed?
- attachments from the tuber coxae from a distinct ridge
What is the origin of the transverse abdominus?
- tips of the transverse process of the lumbar vertebrae and last rib
Where does the TA insert?
- via aponeurosis dorsal to the rectus abdominis onto linea alba, forming the internal lamina of the rectus sheath
How do TA fibres run?
- dorsoventrally
What is the origin of the rectus abdominus?
- xiphoid process and ventral aspect of the last 10 ribs
Where does the RA insert?
- cranioventral pubic brim
How do RA fibres run?
- caudoventrally
What gives the RA an interrupted appearance?
- transverse tendinous intersections
What nerves innervate the abdominal wall from T12?
- costoabdominal nerve
- iliohypergastric nerve
- ilioinginal nerve
- gentiofemoral nerve
What nerve innervates the abdominal wall from the L5 vertebrae?
- ventral perineal nerve
What does the top of the complex stomach touch?
- the diaphragm
What does the base of the complex stomach touch?
- the abdominal wall
What is the left side and the right side of the complex stomach called?
- left = parietal surface
- right = visceral surface
During ruminant development what nutrient is required?
- volatile fatty acids
When do rumen contractions begin?
- 3 weeks of age
Why is it important to know where nerves are?
- to block nerves
- for muscle suturing
Where can you find the lumbar fosser?
- at the end of the transverse processes of the lumber vertebra
Where is the liver located in the thoracic abdomen?
- immediately behind the diaphragm
What does development of the rumen do to the liver?
- pushes the liver entirely to the right half of the abdomen
What does the ruminant liver not have?
- no fissures
What does the ruminant liver consist of?
- left and right hepatic lobes
- quadrate lobe and caudate lobe
What does the ruminant pancreas have?
- 2 limbs
What is the pancreas closely associated with?
- with the liver and descending duodenum
What duct is present in small ruminants?
- pancreatic duct
What duct in present in the ox?
- accessory duct
The large rumen occupies the left side of the abdomen - therefore what happens to the intestines?
- they are pushed to the right side of the abdomen
What is the position of the jejunal coil dependant on?
- of the fullness of the rumen and size of the uterus
What side of the abdomen is the cecum located on?
- the right side
What is not present in the large intestine?
- no taenia nor haustra
= big thick bands of longitudinal muscle that pulls intestine together
Which direction does the blind end of the large intestine point?
- points caudally
What is the longest part of the intestines and what characteristic does it have?
- ascending colon = longest
- has a characteristic spiral arrangement
What is the ox’s intestinal arrangement?
- 2 centripetal turns reversed in central flexure and succeeded by 2 centrifugal turns
What is a sheep intestinal arrangement?
- 3 centripetal turns and 3 centrifugal turns
What is a goats intestinal arrangement?
- 4 centripetal turns and 4 centrifugal turns
How does the short transverse colon continue as the descending colon?
- it crosses the midline cranial to the root of the mesentery to continue as the descending colon
How is the rectum formed?
- descending colon upon entering the pelvis becomes the rectum
In a rectal examination where would you find the rumen and left kidney?
- left abdomen = rumen
- right abdomen = left kidney - just right of midline
During a rectal exam what would you find in the caudal abdomen?
- ovaries and uterus
- bladder
- aorta
- pelvis
What layers would you find in the complex stomach?
- gas
- fibre mat = moderate fermentation
- intermediate zone = intense fermentation
- liquid zone = moderate fermentation
What are the 3 types of rumen contractions?
- primary contractions (mixing contractions)
- contractions related to rumination
- secondary contractions (contractions related to eructation)
How do mixing contractions move?
- start in the reticulum and move caudally along the rumen as a peristaltic wave
How do reticular muscles contract?
- contract twice in 5-10 secs with brief pause
what do mixing contractions do?
- forces coarse fibrous material from top of reticulum to central and dorsal rumen
- completely empties the reticulum of finely-dispersed well-fermented content from lower portion
How do rumen contractions move?
- starts in cranial sac and passes dorsally and caudally in dorsal rumen sac moving ingest into the caudodorsal blind sac
What does contraction of the caudodorsal sac do?
- forces content cranially
- similar occurs in the ventral rumen sac
What is rumination?
- transportation of swallowed ingesta back into oral cavity for additional chewing
How does rumination occur?
- Extra reticular contraction preceding the biphasic contraction
- Hydrostatic pressure difference between oesophagus and reticulum draws reticular content into oesophagus
- Anti-peristaltic contractions in the oesophagus propels bolus into oral cavity
- Fluid fraction re-swallowed whilst rest of bolus masticated before being re-swallowed
5.Increased saliva secretion increases fluid and ions delivered to reticulorumen
In the course of 24 hours how much gas can a high yielding cow produce from fermentation?
- 250-500L gas
What are secondary contractions?
- rumen contractions associated with eructation
How many primary contractions are between each secondary contraction?
- 2-3
How does eructation happen?
- Contraction start in the caudal blind sacs and move cranially along the dorsal sac
- Gas cap pushed towards oesophageal opening
- Negative intra-thoracic pressure draws gas into oesophagus when sphincter opens
- Gas passes to mouth via anti-peristaltic waves
How do we assess forestomach activity?
- number and strength of contractions of the dorsal sac of the rumen over 5 minutes
During assessment of forestomach activity you can auscultate/fell over the paralumbar fossa.
How many contractions should you expect to feel at rest and during feeding?
- at rest = 1 contraction/min
- during feeding = 2-3/min
How are contractions regulated/
- Long reflexes mediated via the vagus nerve
- Short reflexes mediated via ENS
Why is is good to assess ruminal contractions?
- Strength and frequency of ruminal contractions good indicator of a ruminants well- being
What can go wrong in ruminants?
- LDA
- RDA
- Abdominal volvulus - twist of abomasum
- Ruminal tympani – bloat
- Hardware disease – traumatic
reticulopericarditis
