Animal Anatomy, Physiology and Histology
Animal anatomy, physiology and histology in this exam tests structure–function links in cattle, buffalo, sheep, goat, pig and poultry, plus microscopic identification of tissues. Expect questions that combine a species difference with a functional consequence, not isolated labels.
Core rules
- The ruminant stomach has four compartments: reticulum (honeycomb mucosa), rumen (fermentation vat, papillae), omasum (manyplies; absorbs water and volatile fatty acids) and abomasum (glandular true stomach).
- Adult cattle have 32 teeth: I0/4, C0/0, P3/3, M3/3; upper incisors are replaced by a dental pad. Ageing by incisors is unreliable in buffalo.
- Rumen pH is normally about 6.5–7.0. Microbial fermentation produces VFAs; eructation removes gas; rumination reduces particle size.
- Histology: rumen has stratified squamous keratinised epithelium; small intestine has simple columnar epithelium with villi and goblet cells; trachea has pseudostratified ciliated columnar epithelium.
- Horse and pig are monogastric; the horse is a hindgut fermenter, so fibre digestion occurs in the caecum and colon, not the stomach.
Worked example
A cow is off feed, has a distended rumen, pH 5.6, few active protozoa and sloppy manure after a sudden maize meal overload. Reasoning: rapid starch fermentation lowers pH, kills protozoa and favours lactate-producing bacteria; this is rumen acidosis, not simple bloat. Bloat would show gas distension with a frothy or free-gas cap and usually near-neutral pH.
Traps
Do not label the omasum as the true stomach. Do not give upper incisors to cattle. Do not confuse stratified squamous rumen mucosa with glandular gastric mucosa. In histology, match epithelium to organ before choosing a function.