Chapter 7- Nutrition in man

Question 1

What is nutrition? Define it.

Answer 1

Nutrition is the process by which organisms obtain food and energy, for growth, repair, and maintenance of the body.

Question 2

What are the four processes that food goes through during digestion?

Answer 2

1. Ingestion
2. Digestion
3. Absorption
4. Egestion

Question 3

Explain what happens in the buccal cavity.

Answer 3

1. Teeth- physical digestion. The teeth help break down food molecules into smaller molecules, increasing surface area to vol. ratio.
2. Saliva- contains mucin, which softens food. Salivary amylase helps break starch down into maltose.
3. Tongue- rolls the food into slippery round masses called boli.

Question 4

What happens to the epiglottis during respiration vs during swallowing of food substances?

Answer 4

1. During breathing- air passes into the trachea, and the larynx moves downwards. The glottis is kept open for air to pass through.
2. During swallowing- larynx moves upwards and the epiglottis covers the glottis, preventing the food particle from entering the trachea.

Question 5

What happens if food molecules pass down the trachea?

Answer 5

When this happens, the person will start coughing violently. Coughing is automatically induced to force the food particle out of the trachea.

Question 6

Describe the function and structure of the oesophagus.

Answer 6

It is a narrow and muscular tube that extends to the stomach. It is made up of mainly two muscles- the longitudinal and the circular muscle. Peristalsis occurs here, all the way to the large intestine. Food goes down the oesophagus to the stomach.

Question 7

Describe the movement of the longitudinal and circular muscles.

Answer 7

1. The circular muscles contract first, and the longitudinal muscles will relax. This causes the walls of the oesophagus to constrict and become narrower and longer, pushing the food molecules forward.
2. The longitudinal muscles then contract while the circular muscles relax, causing the walls to dilate and become wider and shorter. This widens the lumen for food to enter.

Question 8

Describe the function and how peristalsis works.

Answer 8

Peristalsis is a wave like, rhythmic muscular contractions in the walls of the alimentary canal. It helps enable food to be mixed with digestive juices, and pushes or propels food along the gut.

Question 9

Describe the function and the structure of the stomach.

Answer 9

The stomach is a thick, muscular and distensible muscular bag. It helps to digest and liquefy food particles, specifically proteins.

Question 10

Describe the composition and function of gastric juices.

Answer 10

Composition- dilute sol. of hydrochloric acid, pepsin and mucus.
1. Denatures salivary amylase- no more digestion of starch.
2. Provides acidic medium for pepsin to function.
3. Converts pepsinogen to pepsin.
(Pepsinogen + HCL > Pepsin (active form)).
4. Kills harmful microorganisms in food.

Question 11

What happens after digestion in the stomach?

Answer 11

1. Food usually stays there for 3-4 hours.
2. Food becomes partially liquefied, aka chyme.
3. Passes in small amounts into the duodenum when the pyloric sphincter is relaxed and opens.

Question 12

What is the structure and function of the small intestine?

Answer 12

1. Duodenum, jejunum, ileum (highly coiled- small space).
2. Up to 6m long in adults.
3. Walls secret digestive juices from glands, which contains enzymes. (Digests starch, fats and proteins).
4. Adapted to absorb digested food particles (ileum).

Question 13

Chyme enters the duodenum and stimulates the release of ___________.

Answer 13

1. Pancreatic juices
2. Bile
3. Intestinal juices

Question 14

How is trypsin oven activated, and what does it act on?

Answer 14

1. Trypsinogen + enterokinase > trypsin.
2. Proteins + trypsin > polypeptides.
3. Polypeptides + peptidases > amino acids.

Question 15

What is the pancreatic juice made up of?

Answer 15

1. Pancreatic amylase, to digest starch to glucose.
2. Pancreatic lipase, to digest fats to fatty acids and glycerol.
3. Trypsinogen, an inactive enzyme.
   (pH > 7, to neutralize the acidic chyme and provide and alkaline medium for prancreatic enzymes)

Question 16

What does bile contain? What does it do?

Answer 16

1. Bile emulsifies fats by breaking fat globules to small fat droplets which are suspended in water. (Emulsification- increases surface area to volume ration = only physical digestion.)
2. These small fat droplets are then broken down by pancreatic lipase.
3. Alkaline, greenish-yellow substance.

Question 17

What does intestinal juice contain?

Answer 17

Intestinal juices are secreted from intestinal glands.

1. Maltase
2. Sucrase
3. Lactase
4. Peptidases
5. Intestinal lipase

Question 18

How is the small intestine adapted for absorption?

Answer 18

1. Thin walls of villi- easy diffusion into bloodstream.
2. Length of the intestine (>6m)- increases time for absorption.
3. Many blood capillaries- carry the nutrients away quickly.

Question 19

What methods of transport are used to transport the food into the blood capillaries?

Answer 19

1. Active transport- glucose, amino acids
(Lumen to epithelial to blood cells)
2. Diffusion- glucose, amino acids
3. Diffusion- glycerol and fatty acids
(Lacteal / lymphatic capillaries)

Question 20

What is the structure of the large intestine?

Answer 20

1. Colon
2. Rectum
3. Caecum and appendix
4. Anus
   It is shorter, but broader than the large intestine. It is about 1.5m long.

Question 21

What are the functions of the large intestine?

Answer 21

Colon- Absorb mineral salts and water from undigested food material?
Rectum- Stores faeces temporarily.
Anus- expels faeces (egestion).
General- absorption of water and mineral salts.

Question 22

State the function and structure of the pancreas.

Answer 22

The pancreas is a gland connected to the duodenum via the pancreatic duct. It secretes insulin, which regulates blood glucose levels, as well as glucagon, which stimulates the liver to release glucose. Pancreatic juice also comes from the pancreas.

Question 23

Define assimilation.

Answer 23

Assimilation is the process whereby some substances are converted into new protoplasm or used to provide energy for the body.

Question 24

What is the function and structure of the hepatic portal vein?

Answer 24

The hepatic portal vein consists of blood capillaries that supply the small intestine which unite to form the vein. It transports sugars, fats and amino acids to the liver. Proteins are distributed for new growth and repair in cells, as well as to form enzymes and hormones. These nutrients leave the liver via the hepatic vein.

Question 25

What are the functions of the liver?

Answer 25

1. Regulates blood glucose levels. 2. Production of bile. 3. Recycling and storing of iron. 4. Detoxification. 5. Synthesis of proteins.

Question 26

How is the blood glucose concentration kept constant?

Answer 26

(Normal sugar levels are at 60-70mg/100cm3) 1. When there is too much sugar, the pancreas secretes insulin, which stimulates the liver to store glucose in the form of glycogen. 2. When there is too little sugar, the pancreas secretes glucagon, which stimulates the liver to convert glucagon back to glucose, hence increasing the blood glucose level.

Question 27

How is protein synthesis carried out?

Answer 27

1. Liver uses amino acids to synthesize the proteins. 2. Breakdown of proteins: Amine group gets removed from the amino acids, where it gets converted into urea in the liver. Carbon residues are converted into glucose in the liver. (Deamination)

Question 28

What happens during the storage and breakdown of iron?

Answer 28

1. Red blood cells are destroyed in the spleen. 2. The iron from the red blood cells are stored in the liver, 3. Haemoglobin is also recycled in the liver. 4. These two components are recycled for synthesis of new RBCS. 5. Bile is also produced in the process.

Question 29

How is detoxification carried out?

Answer 29

Detoxification is the process of converting harmful substances into harmless products. An example would be the conversion of alcohol to acetaldehyde, via the enzyme alcohol dehydrogenase. Acetaldehyde becomes a new source of energy for the cells, and can also be broken down further into compounds that can be used during respiration, for cellular activities.

Question 30

What are the harmful effects of alcohol consumption?

Answer 30

1. Slows down brain function 2. Reduced self control | bipolarity 3. Symptoms of drunkenness 4. Addiction 5. Increased risks of gastric ulcers 6. Liver cirrhosis

Question 31

Explain what happens during liver cirrhosis.

Answer 31

1. It's a disease which destroys liver cells. 2. The liver cells are replaced by fibrous tissue (less functionable) 3. Hemorrhage / bleeding in the liver. 4. This can lead to liver failure and eventually death.