ANSWERS

1. What is the function of the digestive system?
   This visceral system is responsible for the ingestion of food and breaking it down into simple compounds that can be absorbed and utilised by the body.
2. List the components of the digestive system.
   • The mouth, teeth (see Part I - Chapter 6 - Anatomy & Physiology:
   • The Skeletal System), tongue & salivary glands.
   • The pharynx.
   • The stomach.
   • The small intestine.
   • The large intestine.
3. List 3 functions of the tongue.
   • The manipulation of food.
   • The tasting of food (the surface is covered with taste buds).
   • Grooming.
4. What is the collective name given to the numerous small projections on the surface of the tongue used for grooming?
   Papillae.
5. Can you list the 4 pairs of salivary glands found in the cat and dog?
   • Zygomatic.
   • Sublingual.
   • Mandibular.
   • Parotid.
6. List 5 functions of saliva.
   • Moistening and softening of the food to optimise the effect of the digestive enzymes.
   • Lubrication of the food in order to enable it to pass with ease down the oesophageal tract.
   • Moistening the mouth to prevent the mucous membranes from drying out.
   • Production of mucous which keeps the mouth moist (the zygomatic, sublingual and mandibular glands all produce mucous).
   • Production of alpha amylase (ptyalin) which starts the digestion of carbohydrates (the parotid gland produces this enzyme).
7. Briefly describe the sequence of events that take place during swallowing.
   • A bolus of food is positioned on the tongue and pushed to the back of the mouth.
   • The soft palate is raised in order to block off the nasopharynx.
   • The hyoid apparatus moves forward and the epiglottis closes the larynx.
   • The pharynx is opened.
   • The bolus is pushed to the top of the pharynx by the tongue.
   • The pharynx closes.
   • Waves of muscular contraction carry the food down the oesophagus from the pharynx to the stomach.
   • The soft palate is lowered.
   • The hyoid apparatus moves backward, the epiglottis moves forward, and the larynx is opened.
8. What is the name given to the waves of muscular contraction, which carry the food down the oesophagus from the pharynx to the stomach?
   Peristalsis.
9. Name the 3 parts of the stomach and briefly describe each.
   • Cardia - the oesophageal opening.
   • Fundus - the body.
   • Pylorus - the narrowed entrance to the small intestine.
10. What are rugae?
    Longitudinal folds of the mucosal lining of the stomach that flatten when the stomach is full.
11. What is the name given to a fold of the peritoneum which connects the intestine to the dorsal abdominal wall?
    The mesentery.
12. What is the great omentum?
    The dorsal mesentery of the stomach. This is massively expanded into a double sheet and also houses the spleen.
13. What is meant by gastric?
    Pertaining to the stomach.
14. A number of secretions are produced by cells in the stomach wall. These include mucus, hydrochloric acid, pepsinogen, gastrin and lipase. Can you state the function of each?
    • Mucus - protection of the stomach lining.
    • Hydrochloric acid - provides the low pH necessary for pepsin activity.
    • Pepsinogen - pepsin production (in conjunction with hydrochloric acid).
    • Gastrin - stimulation of hydrochloric acid production.
    • Lipase - breakdown of fat.
15. What is chyme?
    The mixture of food, saliva and gastric secretions that leave the stomach.
16. What is the function of the goblet cells of the stomach wall?
    Mucus production.
17. Define vomiting.
    A reflex act of expulsion of the stomach contents via the oesophagus and mouth. Vomiting may occur as a response to over-distension of the stomach or irritation to the stomach lining (gastritis).
18. Describe the following: stercoraceous vomit, bilious vomit and haemorrhagic vomit.
    • Stercoraceous vomit - vomit containing faeces.
    • Bilious vomit - vomit containing bile.
    • Haemorrhagic vomit - vomit containing blood.
19. List the 3 organs that comprise the small intestine.
    • Duodenum.
    • Jejunum.
    • Ileum.
20. What occurs within the small intestine?
    • Digestion.
    • Absorption.
21. List the 3 secretions of the small intestine.
    • Pancreatic juice.
    • Bile.
    • Intestinal juice.
22. The pancreas is described as a mixed gland. What is meant by this?
    It has both endocrine and exocrine functions. The endocrine part is concerned with the secretion of chemical messengers called hormones, whilst the exocrine part secretes enzymes involved in digestion.
23. List the enzymes secreted by the pancreas and briefly describe the function of each.
    • Amylase - carbohydrate digestion.
    • Trypsinogen - this is converted to trypsin by an enzyme called enterokinase which is secreted in the intestinal juice; trypsin is involved in protein digestion.
    • Lipase - fat breakdown (converts fats to fatty acids and glycerol).
    • Peptidases - protein breakdown (convert polypeptide chains to free amino acids).
    • Nucleotidases - breakdown of DNA and RNA.
24. Which organ is responsible for bile production?
    The liver.
25. Which organ is responsible for the storage of bile?
    The gall bladder.
26. What are the 2 main constituents of bile?
    • Bile salts (involved in fat breakdown).
    • Bile pigments (waste products originating from the liver as a result of haemolysis).
27. Name the 2 bile pigments. These are responsible for the colouration of the faeces.
    • Bilirubin.
    • Biliverdin.
28. List the functions of the liver.
    • Synthesis of fibrinogen and other proteins used in blood clotting.
    • Breakdown of ammonia to urea.
    • Storage of glycogen.
    • Fat metabolism.
    • Bile formation.
    • Detoxification and storage of steroid hormones.
    • Storage of the fat-soluble vitamins A, D, E & K.
    • Heat production and regulation of body temperature.
    • Storage of iron.
29. Where are the cells responsible for the production of intestinal juice located?
    The wall of the crypts of Lieberkuhn (these lie between the villi of the small intestine).
30. List the enzymes contained within intestinal juice. Briefly describe the function of each.
    • Disaccharides - breakdown of maltose, sucrose and lactose.
    • Peptidases - breakdown of peptidases into amino acids.
    • Nucleotidases - breakdown of DNA and RNA.
    • Enterokinase - conversion of trypsinogen to trypsin.
31. What is the collective name of the projections of the small intestine, which increase the surface area available for absorption?
    Villi.
32. What is the name of the milky fluid containing digested fats which are absorbed into the lacteals of the small intestine?
    Chyle.
33. What are lacteals?
    Lymphatic vessels within the villi of the small intestine which absorb chyle.
34. List the 3 parts that comprise the large intestine.
    • Caecum.
    • Colon.
    • Rectum.
35. Why is the caecum of little significance in the cat and dog?
    It is a site where bacteria are used to breakdown coarse vegetable matter, and the cat and dog are carnivores.