Rumen anatomy

Question 1

What are the components of the ruminant stomach and their basic functions

Answer 1

Rumen - fermentation vat
Reticulum - part of rumen
Omasum - water absorption
Abomasum - true stomach

Question 2

Why do ruminants have a rem-reticulum + omasum?

Answer 2

Mammals are unable to digest beta-lined polysaccharides (such as cellulose in plants)
The rumen-reticulum + omasum allow utilisation of microorganisms to digest cellulose and hemicellulose

Question 3

What is the origin of the fore-stomachs of the ruminants

Answer 3

derived from gastric spindle

Question 4

What is the lining of the forestomachs of ruminants

Answer 4

stratified keratinised epithelium

Question 5

Why is surgery in ruminants performed on the LHS?

Answer 5

the rumen acts as a plug to prevent abdominal contents from escaping the body cavity

Question 6

Where is the spleen attached in ruminants?

Answer 6

attached to rumen as greater curvature of the stomach has been lost embryologically

Question 7

Answer 7

Question 8

Describe the anatomy of the ruminant oesophagus

Answer 8

Large and distensible
Striated muscle along whole length
Insensitive mucosa
Heavily keratinised

Question 9

Where does chock (oesophageal obstruction) occur most in ruminants?

Answer 9

close to pharynx at thoracic inlet

Question 10

Describe the features of the reticulorumen

Answer 10

Watm
Moist
Anaerobic
pH ~6.5
Suitable environment for range of microorganisms

Question 11

What is the product of fermentation in the reticulorumen

Answer 11

Volatile fatty acids (acetate, butyrate, propionate), CO2 and methane

Question 12

What happens to the rumen if there is too much grain in diet?

Answer 12

causes rumen acidosis which kilkls off flora

Question 13

What happens to fibrous feedstuffs in the reticulorumen

Answer 13

They remain long enough for complex carb digestion
Surface area of fibres is increased by initial chewing and ruminating
Long fibre particles are regurgitated and re-chewed

Question 14

How often are reticulorumen contraction?

Answer 14

~3 every 2 mins

Question 15

Label the rumen from the LHS

Answer 15

Question 16

What is the anatomy and function of rumen papillae

Answer 16

Leaf shaped
Keratinised
Poorly developed in roof of dorsal sac
Increased surface area for flora and absorption

Question 17

How does diet affect the rumen papillae

Answer 17

Long fibres sit at top of rumen -> long papillae
Short fibres sit at bottom of rumen -> short fibre
Gas cap at top of rumen (no fibre) -> no papillae

Question 18

What stimulates growth rumen papillae?

Answer 18

High conc of VFAs
Long fibres

Question 19

Which section of the ruminant forstomach is this?

Answer 19

Rumen

Question 20

Describe the anatomy of the reticulum

Answer 20

Series of cells with smaller cells inside
Small conical papillea
Keratinised

Question 21

What part of the ruminant forestomach is this?

Answer 21

Reticulum

Question 22

How does feed quality affect rumination time?

Answer 22

Poor quality feed e.g., rough hay spends more time in the rumen - this is good for the rumen as ruminants are designed to be slow digesters
Grains - spend less time in rumen but leads to acidity problems

Question 23

What is the function of the omasum?

Answer 23

Still unclear:
- probably water absorption
- pumping ingesta from reticulum into abomasum

Question 24

Describe the anatomy and function of the omasum

Answer 24

Contains ~100 laminae covered with conical papillae -> huge SA
Laminae are 3 different sizes
Regular contractions squeeze material into recesses and progresses fluid forward
Water reabsorption

Question 25

Which part of the ruminant forestomach is this?

Answer 25

omasum

Question 26

Describe the anatomy of the abomasum of ruminants

Answer 26

large longitudinal rugae columnar epithelium essentially the same as a monogastric stomach

Question 27

What part of the ruminant is this

Answer 27

abomasum

Question 28

How does the neonatal ruminant digest milk?

Answer 28

Digested in the abomasum Fundic glands produce renin which coagulates casein (milk protein) in acidic environments The clot retains milk to allow complete digestion by pepsin

Question 29

How does milk bypass the reticulo-rumen in neonates?

Answer 29

The reticular groove contracts creating a tunnel between oesophagus and reticulo-omasal orifice When relaxed the oesophagus empties into reticulo-rumen Only functions when drinking milk

Question 30

What happen if the reticular groove fails?

Answer 30

Milk enters reticulo-rumen Milk ferments and causes scour

Question 31

what is the reticular-groove reflex stimulated by and what is it poorly reactive to?

Answer 31

Stimulated by the vagus nerve due to: - suckling milk/pharyngeal stimulation - noises associated with the 'feeding routine' Poorly reactive to: - drinking (hence bucket-fed calves are prone to scour - stomach tubing

Question 32

Describe the development of the ruminant forstomach after birth

Answer 32

- development after birth promoted by presence of forage in rumen as young animals start to eat solid food - rumen flora develops within a couple weeks and is functional by 6-8 weeks