Nutrition in Man

Hi all,
Please note that we've contacted the exam board with regards to the concept of water absorption in the gut. As previously mentioned in class, the greatest amount of water is absorbed in the ileum, not the colon, and this is recognised by Cambridge as being correct. So in the case of questions like this:
Where in the alimentary canal is most water absorbed?
A. Colon B. Ileum C. Oesophagus D. Stomach

The answer should be B, not A as stated by some TYS books.

However, the main function of the colon of course, will be to absorb water and mineral salts. So in cases of questions like this:
The main function of the colon of a mammal is to
A. get rid of undigested food material
B. produce enzymes to digest any remaining food
C. absorb digested food materials
D. absorb water

The answer in this case should be D.

MORE QUESTIONS..
1(a) The composition of blood is affected by the organs through which it circulates. Describe the changes that occur as blood passes through:-
(i) the pancreas
(ii) the wall of the small intestine after a meal [4]

(b) What are the changes to the body when a person receives a sudden shock? Discuss and identify what causes these changes. [6]

ANSWERS
1(a)(i) As blood passes the pancreas, the level of blood glucose & amino acids decreases as the cells take up glucose for respiration, and amino acids for protein synthesis (insulin production);
The level of insulin in the blood increases as the pancreas secretes insulin into the blood (if blood glucose concentration is higher than usual) [1/2]
At the same time, oxygen is used up by respiring cells and carbon dioxide is released, decreasing oxygen levels and increasing carbon dioxide levels [1/2]

(ii) After a meal, the amount of glucose/monosaccharides, amino acids (but not fatty acids and glycerol) increases in the blood in the walls of the small intestine;
Respiring cells use oxygen and release carbon dioxide, decreasing oxygen levels and increasing carbon dioxide levels;

(b) When a person receives a shock, the adrenal gland secretes adrenaline which brings about the fight or flight response:
• increases blood glucose levels due to the conversion of glycogen stored in the liver into glucose;
• increases metabolic rate to release more energy during respiration to cope with the situation;
• increase heart rate and blood pressure allows oxygen and glucose to be carried faster to the muscles for respiration;
• vasoconstriction of arterioles to digestive system and skin, so less blood gets directed to non-essential organs;
• vasodilation of arterioles to the skeletal muscles results in more blood directed to the muscles;
• bronchi dilate to increase amount of air entering lungs;

2(a) Name a function of protein and the disease caused by its deficiency [2]
(b) Explain what happens to a fried fish burger in the small intestine. [6]

ANSWERS
(a)- growth ; OR
- repair of worn out tissues and cells ; OR
- synthesis of hormones / enzymes ;
Kwashiorkor ;

(b) - starch in the bread broken down by pancreatic amylase into maltose, maltose broken down by maltase (intestinal glands) into glucose;
-proteins in the fish broken down by trypsin into peptones, which are broken down by erepsin into amino acids ;
- fats in the oil broken down by lipase into fatty acids and glycerol ;
- bile from liver helps to emulsify fats, to increase surface area for lipases to work on ;
- glucose and amino acids absorbed into the blood capillaries in the villi;
- fatty acids combine with bile salts to become soluble soaps, absorbed with glycerol into villi, recombine into fat globules and are absorbed into the lacteal in the villi;

3. Distinguish between endocrine and exocrine glands. Describe the different roles of exocrine and endocrine glands in the pancreas.
ANSWER
An endocrine gland secretes its product (e.g. hormone) directly into the blood. An exocrine gland has a duct to take the gland’s secretion to its site of action.
For example: the islet of Langerhans are patches of endocrine tissue scattered throughout the exocrine tissue (pancreactic gland) of the pancreas.
Islet of Langerhans produces insulin – lowers blood glucose level …..;
Pancreatic glands produces digestive juices containing enzymes to help in hydrolysis of food. It has a pancreatic duct to bring its secretion to the duodenum …. ;