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8.2 The Digestive System
1. What is homeostasis?
Homeostasis is the maintenance of a constant internal state, e.g. temperature, water,
salt, sugar, oxygen, carbon dioxide concentration.
2. What is the function of the digestive system?
The function of the digestive system is to prepare food for absorption.
3. Name and describe the two types of digestion.
The two types of digestion are mechanical (physical) and chemical digestion. Physical
digestion takes large pieces of food and breaks it down into smaller pieces of food.
Chemical digestion takes large molecules and breaks them down into smaller molecules.
4. What is the difference between the following:
Ingestion: Food enters the GI tract
Digestion: Food is prepared for absorption – large pieces are food are broken into
smaller pieces and large molecules are broken into small molecules
Absorption: Small nutrient molecules pass through a cell membrane into the cytoplasm.
Egestion/elimination: Waste materials leave the GI tract
4. Describe the digestive tract.
The digestive tract is a long tube which passes through the body.
6. What are the accessory organs and what do they do?
The accessory organs are the saliva glands, the pancreas, liver and gall bladder.
7. What is the lumen?
The lumen is space inside the GI tract.
8. Describe the types of teeth and the types of teeth found in different animals.
The three types of teeth are the incisors, the canines and the molars. The incisors are flat,
blade-like teeth used for cutting. The canines are saw-like (triangular) teeth which are
used for tearing. The molars are flat, cube-shaped teeth which are used for grinding and
crushing. Carnivores have more canines whereas herbivores have incisors and molars.
9. What is the function of the tongue during chewing?
The tongue is used to manipulate and move food around the mouth. It shapes the bolus.
10. Describe bolus.
Bolus is the ball of crushed and mixed food which is formed in the mouth and swallowed.
11. Describe the following:
Pharynx: passage for both air and food connecting nasal and oral cavities to esophagus
and trachea.
Epiglottis: Flap of tissue which prevents food from entering the trachea
Trachea: windpipe, passage for air to lungs, held open by D-shaped rings of cartilage
Esophagus: tube connecting pharynx to stomach
Peristalsis: wave-like contractions which propel food through the GI tract
12. Describe the stomach.
The human stomach is a J-shaped stretchable organ that can hold approximately 1.5L
food.
13. What substances are secreted in the stomach?
Hydrochloric acid, pepsin(ogen) and rennin are secreted into stomach.
14. What is the function of mucus?
Mucus protects the stomach lining from acid.
15. What is chyme?
Chyme is a liquefied paste that is found in the stomach.
16. What occurs in the small intestine?
The small intestine is the major site of digestion and absorption.
17. What is the function of the villi and the microvilli?
The villi and microvilli provide surface area for absorption of nutrients.
18. Describe the large intestine and its functions.
The large intestine is short tube of large diameter. It has four sections – the caecum,
colon, rectum and anus. The colon is divided into four sections – the ascending,
transverse, descending and sigmoid colon. Its main function is to reabsorb water and to
hold and compact the unabsorbed material.
19. Comment on the appropriateness of the names ‘small’ intestine and ‘large’
intestine.
The small intestine is small in diameter but extremely long whereas the large intestine has
a large diameter but is relatively short.