(a) In sequence, name the organs that constitute the alimentary canal of humans (b) State: (i) three structural differences; (ii) three structural similarit...

Answer Details

(a) Organs of the alimentary canal of humans, in sequence

1. Mouth (buccal cavity)
2. Pharynx
3. Oesophagus (gullet)
4. Stomach
5. Small intestine (duodenum, then ileum)
6. Large intestine (colon)
7. Rectum
8. Anus

(b) Bird versus human alimentary canal

(i) Three structural differences

(ii) Three structural similarities

1. Both have a mouth for taking in food.
2. Both have an oesophagus leading to the stomach.
3. Both have a small and large intestine for digestion and absorption.

(c) How the dentition of herbivores is adapted for feeding

Herbivores have wide, chisel-like incisors that bite and crop grass and leaves. The canines are reduced or absent, leaving a gap (diastema) in which the tongue turns and rolls food. The premolars and molars are broad with ridged (interlocking) grinding surfaces and grow continuously to replace the wear caused by chewing tough, fibrous plant material. The lower jaw also moves sideways so the ridged cheek teeth grind the food thoroughly.

(d) Two roles of the pancreas in digestion

• It secretes pancreatic juice containing digestive enzymes (amylase, trypsin and lipase) that act on carbohydrates, proteins and fats.
• It secretes sodium hydrogen carbonate (an alkali) that neutralises the acidic food arriving from the stomach, giving the enzymes the right pH.