Chapter 5: Nutrition in Humans Flashcards
1
Q
What processes does ‘Nutrition In Humans’ consist of?
A
- Ingestion
- Digestion
- Absorption
- Assimilation
- Egestion
2
Q
What are the organs in our human digestive system and its accessory organs?
A
- Mouth
- Oesophagus
- Stomach
- Small intestine (duodenum & ileum)
- Large intestine (Colon, rectum and anus)
- Liver (bile duct)
- Gall bladder
- Pancreas
3
Q
Where does the oesophagus pass through and what does it join together?
A
It passes through the thorax (chest), and joins the mouth to the stomach.
4
Q
What are the names of the 2 layers of muscles?
A
- Longitudinal muscles
- Circular muscles
4
Q
What is special about the walls of the oesophagus?
A
It contains two layers of muscles, and they are present along the whole alimentary canal from the oesophagus to the rectum.
5
Q
What are the positions of the 2 muscles in the oesophagus?
A
- Longitudinal muscles are found on the outer side of the gut wall.
- Circular muscles are found on the inner side of the gut wall.
6
Q
What is peristalsis?
A
It is the rhythmic, wave-like muscular contractions in the wall of the alimentary canal.
7
Q
What does peristalsis enable food to do?
A
It enables the food to be mixed with digestive juices and also pushes the food along the gut.
8
Q
What happens when the circular muscles contract?
A
The longitudinal muscle relaxes. As a result, the wall of the gut constricts and becomes narrower and longer, causing food to be pushed forward.
9
Q
What happens when the longitudinal muscles contract?
A
The circular muscles relax. As a result, the gut dilates and becomes wider and shorter, widening the lumen for food to enter.
10
Q
Describe the features of the stomach.
A
It is a distensible muscular bag, with thick and well-developed muscular walls
10
Q
What is special about the inner surface of stomach wall?
A
They have numerous pits, the walls of which are lined with gastric glands. These gastric glands secrete gastric juice which plays an important part in digestion.
11
Q
What is in gastric juice?
A
Protease and hydrochloric acid (pH 2)
12
Q
Why are these 2 components needed in gastric juice for digestion?
A
- Protease allows for chemical digestion.
- Hydrochloric acid allows the protease to have a suitable environment to function as the optimum pH level for protease is pH 2, which is the pH level of hydrochloric acid.
12
Q
What are the different parts of the small intestine?
A
- Duodenum
- Ileum
13
Q
What parts is the duodenum connected to?
A
Stomach, pancreas and bile duct
14
Q
What is the function of the pancreas being connected to the duodenum?
A
This allows the pancreas to release pancreatic juice.
14
Q
What is special about the lining of the walls of the small intestine?
A
They contain glands that secrete digestive enzymes.
15
Q
What are the different parts of the large intestine?
A
- Colon
- Rectum
- Anus
15
Q
What happens in the rectum?
A
- Faeces are stored temporarily in the rectum.
- When the rectum contracts, the faeces are expelled through the anus.
16
Q
What is the main function of the colon?
A
It absorbs about 90% of the remaining water and mineral salts from the undigested food material.
17
Q
What are the accessory organs for the alimentary canal?
A
- Liver
- Gall bladder
- Pancreas
18
Q
What do liver cells do?
A
They produce and secrete bile.
18
Q
What is bile?
A
It is an alkaline yellowish-green liquid that contains bile salts.
19
How does bile help in digestion of food?
Though it does not contain any enzymes, it aids in the physical digestion of food.
20
What is the gall bladder's function?
It stores bile temporarily in itself.
21
What happens when the gall bladder contracts?
Bile flows into the duodenum via the bile duct.
22
How is the pancreas connected to the duodenum?
The pancreatic duct connects the two organs together.
23
What is the function of the pancreas?
1. Produces pancreatic juice, which has pancreatic amylase, protease and liapse in it, which aids in chemical digestion
2. Secretes hormones such as insulin and glucagon, which are hormones that control the blood sugar level in the body.
23
What is digestion?
It is the process where large, insoluble food molecules are broken down into small, soluble molecules that can enter the body cells' cell membrane be absorbed by it.
23
What is physical digestion?
It is the mechanical break-up of large food pieces into smaller pieces.
23
What does physical digestion do to help in the digestion process?
It increases the surface area-to-volume ratio of the ingested food so that enzymes can act on it more efficiently.
23
What is chemical digestion?
It is the breaking down of large insoluble food molecules into smaller, soluble food molecules that can enter the body cell's cell membrane to be absorbed.
23
What are the processes that take place in the mouth? (Physical Digestion)
1. Food in the mouth stimulates salivary glands to secrete saliva.
2. Saliva is mixed with the food, softening it.
3. Teeth chews the large food pieces into smaller pieces, increasing the surface area-to-volume ratio for the salivary amylase to work on.
4. The tongue rolls the food into boli and moves it to the back of the throat during swallowing.
5. Boli are swallowed and passed down into the oesophagus via pharynx.
6. Peristalsis in the walls of the oesophagus pushes each bolus of food down into the stomach.
23
What are the processes that take place in the mouth (Chemical Digestion)
1. Saliva contains salivary amylase, which digests starch to maltose.
2. The optimum pH for salivary amylase is pH7, which is the mouth's pH level.
23
What are the processes that take place in the stomach (Physical Digestion)
1. The presence of food in the stomach stimulates the gastric glands to secrete gastric juice into the stomach cavity.
2. Peristalsis in the stomach wall churns and breaks up the food, and mixes the food with gastric juice.
3.The mucus layer in the stomach protects the stomach wall against being digested by the enzymes it produces, and moistens the food to allow easy movement within the stomach.
4. Food nromally remains in the stomach for about 3-4 hours. The partly digested food becomes liquefied, forming chyme.
5. Chyme passes in small amounts into the duodenum when the pyloric sphincter relaxes and opens.
24
What are the processes that take place in the stomach (Chemical Digestion)
Gastric juice in the stomach contains hydrochloric acid (about pH2), mucus and pepsin, a protease. The protease digests proteins into polypeptides.
24
What is the role of hydrochloric acid in the stomach's gastric juice?
1. It stops the action of salivary amylase by denaturing it.
2. It provides a lwo pH environment within the stomach, about pH2, which is the optimum pH level for pepsin to digest proteins.
3. It kills certain potentially harmful microorganisms in food.
24
What are the processes that take place in the small intestine? (Physical Digestion)
When chyme enters the dudodenum, it stimulates the gall bladder to release bile. Bile passes through the bile duct into the duodenum. Bile salts speed up the digestion of fats.
24
What are the processes that take place in the small intestine? (Chemical Digestion)
When chyme enters the duodenum, it stimulates:
1. the pancreas to secrete pancreatic juice. It passes through the pancreatic duct into the duodenum.
2. the epithelial cells in the small intestine to produce intestinal juice, which contains maltase, protease and lipase.
25
What do pancreatic juice, bile and intestinal juice have in common?
They are all alkaline.
25
What is the function of pancreatic juice, bile and intestinal juice being alkaline?
1. It neutralises the acidic chyme.
2. It provides a suitable alkaline medium (pH8) for the action of the pancreatic and intestinal enzymes.
25
What are the different enzymes that digest carbohydrates and what is the process?
1. Amylase digests starch to maltose
2. Maltase digests maltose to glucose
25
Tell me about carbohydrate digestion in the alimentary canal.
1. Carbohydrate digestion begins in the mouth. Salivary amylase in the mouth's saliva digests starch into maltose. Only a little starch is digested as food does not stay in the mouth for long.
2. Carbohydrates are fully digested into simple sugars in the small intestine. Starch is digested by pancreatic amylase into maltose, which is then further digested by maltase into glucose.
26
What happens to the end-products of carbohydrate digestion?
They become simple sugars that can be absorbed into the bloodstream.
27
Tell me about protein digestion in the alimentary canal.
1. Protein digestion begins in the stomach, where stomach proteases digest proteins into polypeptides.
2. The polypeptides that enter the small intestine are further digested by pancreatic protease into smaller polypeptides.
3. These smaller polypeptides are further digested by to amino acids by intestinal protease.
28
What happens to the end-products of protein digestion?
They become amino acids, which can be absorbed into the bloodstream.
29
What happens in the small intestine to fats? Explain.
Fats are emulsified by bile salts. They lower the surface tension of the fats by reducing the attractive forces between the fat molecules. This causes the fats to break into tiny fat droplets suspended in water, forming an emulsion.
29
How does emulsification of fats help digestion of fats?
It increases the surface area-to-volume ratio of the fats, speeding up their digestion by lipase.
30
What is emulsification?
The breaking up of fats into tiny fat droplets.
31
What are emulsified fats digested by?
Pancreatic and intestinal lipases.
32
What are the end-products of fat digestion?
Fatty acids and glycerol
33
What is absorption?
The process where digested food substances are absorbed in the body cells.
34
How do the absorbed nutrients, which are products of digestion, get transported by the bloodstream to all parts of the body?
They diffuse from the small intestine cells' into the bloodstream
34
What are the adaptations of the small intestine?
1. Inner surface of ileum is folded extensively and has many villi to increase the surface area-to-volume ratio for absorption.
2. The epithelium (wall of the villius) is only one cell thick to provide a short diffusion distance for nutrients to pass through.
3. The cells of the epithelium have many microvilli to further increase the surface area-to-volume ratio of the small intestine.
4. Each villius has many blood capillaries that allow the blood to transport the absorbed glucose and amino acids in order to maintain a concentration gradient.
5. Each villius contains a lacteal to transport the absorbed fats away and maintain a steep concentration gradient.
6. The epithelial cells contain many mitochondria to provide energy for active transport of nutrients into the villi.
35
How does absorption of glucose, amino acids and fatty acids and glycerol take place in the intestines?
1. Glucose and amino acids are absorbed by diffusion into the blood capillaries of the villi.
2. Glucose and amino acids are also absorbed by active transport. This happens when there is a lower concentration of tehse digested food substances in the lumen of the small intestine than in the blood capillaries.
3. Glycerol and fatty acids diffuse into the epithelium. They then combine to form minute fat globules that enter the lacteals.
36
What happens to undigested and unabsorbed matter?
It is stored temporarily int eh rectum, before it is discharged as faeces through the anus. (Egestion)
36
What is assimilation?
it is the process where some of the absorbed nutrients are converted into new cytoplasm or used to provide energy.
37
Why is the blood in the villi rich in nutrients after absorption?
Majority of absorption of nutrients take place in ileum.
38
How are glucose and amino acids transported?
The blood capillaries unite to form larger blood vessels, which then unite to form a large vein, the hepatic portal vein.
39
What does the hepatic portal vein do?
It transports nutrients from the small intestine to the liver.
39
How are glucose and amino acids utilised?
1. Most of the absorbed sugars are converted into glycogen and stored.
2. Some glucose is transported by the blood leaving the liver and distributed around the body.
3. All the cells then use this glucose as a source of energy. Glucose is assimilated and then broken down during tissue respiration to release energy for the vital activities of the cell.
4. Excess glucose is returned to the liver and stored as glycogen. Insulin stimulates the liver cells to convert excess glucose into glycogen. When the body needs energy, the liver converts the stored glycogen back into glucose. This glucose is then transported by the blood to the different body cells.
5. Amino acids that enter the cells are converted into new cytoplasm that is used for growth and repair of worn-out parts of the body.
6. They are also used to form enzymes and hormones.
7. Excess amino acids are deaminated in the liver.
40
How are fats transported?
1. They are absorbed into lymphatic capillaries. They unite to form larger lymphatic vessels, which discharge fats into the bloodstream.
2. Blood then carries the fats to all aprts of the body, especially the liver.
41
How are fats utilised?
1. Under normal conditions when there is a sufficient supply of glucose, fats are not broken down. They are instead used to build protoplasm.
2. When glucose is in short supply, fats are broken down to provide the energy needed for the vital activities of the body.
3. Excess fats are stored in adipose tissues, which can be found beneath the skin and around the heart and kidneys. They protect these organs by acting as shock absorbers.
42
What are the functions of the liver?
1. Produces bile
2. Deamination of amino aicds
3. Regulation of blood glucose concentration
4. Breakdown of hormones
5. Detoxification
43
Explain the function of the liver. (Production of bile)
The liver helps in the digestion of fats by secreting bile.
43
Explain the function of the liver. (Deamination of amino acids)
1. Excess amino acids are transported to the liver, where their amino groups are deaminated
2. Urea is removed from the body in urine.
3. The remains of deaminated amino acids are converted into glucose in the liver.
4. Any excess glucose formed this way is converted into glycogen.
43
What is deamination?
It is the process where amino groups are removed from amino acids and converted to urea.
44
Explain the function of the liver. (Regulation of blood glucose concentration)
1. The liver helps to keep the blood glucose concentration constant, especially after a heavy meal or during fasting.
2. After a heavy meal, the body's blood glucose concentration is higher than normal. Insulin is secreted and it stimulates the conversion of glucose into glycogen, where glycogen is then stored in the liver. This decreases the blood glucose concentration, bringing it back to normal.
3. During fasting, the body's blood glucose concentration is lower than usual. Glucagon is secreted to stimulate the conversion of glycogen into glucose to be released into the bloodstream. This increases the blood glucose concentration in the body, bringing it back to its normal concentration
45
Explain the function of the liver. (Breakdown of hormones)
After hormones have surved their purpose, they are broken down in the liver.
46
Explain the function of the liver. (Detoxification)
1. Harmful substances may be absorbed into the blood from the alimentary canal.
2. The liver cells detoxify these harmful substances into harmless substances.
3. Liver cells contain an enzyme which breaks down alcohol to compounds that can be used in respiration, providing energy for cell activities.
47
What are the harmful effects of alcohol consumption on the digestive system?
1. Alcohol stimualtes acid secretion in the stomach. Excess stomach acid increases the rik of gastric ulcers.
2. Prolonged alcohol abuse may lead to cirrhosis of the liver, where liver cells are destroyed and replaced with fibrous tissue, making the liver less able to function.
3. Patients with alcoholic cirrhosis may haemorrhage in the liver, leading to lvier failure and eventually death.
47
What are the harmful effects of alcohol consumption on the nervous system?
1. Depressant
2. Reduced self-control
3. Effect on reaction time
4. Long term effects of the alcohol consumption on the brain.
48
Explain the harmful effects of alcohol consumption on the nervous system. (Depressant)
It is a depressant and it slows down brain functions.
49
Explain the harmful effects of alcohol consumption on the nervous system. (Reduced self control)
1. Under the influence, a person becomes carefree as alcohol takes away their self-control.
2. With self-control reduced, they may do things they regret after the effects of alcohol have worn off.
49
Explain the harmful effects of alcohol consumption on the nervous system. (Effect on reaction time)
1. As you drink more alcohol, this may cause slurred speech.
2. Blurred vision and poor muscular coordination makes you clumsy and unable to walk steadily.
3. Your judgement deteriorates and you tends to underestimate speed.
4. If you drive while drunk, you may tend to drive faster with less caution, and your reaction time becomes slower. Thus, drunk drivers have a higher tendency to be involved in traffic accidents.
77
Explain the harmful effects of alcohol consumption on the nervous system. (Long term effects of alcohol consumption on the brain.)
1. 'Wet brain': A type of dementia cause by brain damage as alcohol interferes with the absorption of Vitamin B1 in the small intestine. Vitamin B1 is part of an enzyme needed to break down sugar to release energy for brain activities (e,g conduction of nerve impulses)
2. Shrinkage of brain volume: The brain becomes smaller than normal, especially the region associated to memory and reasoning.
3. Heavy consumption of alcohol during pregnancy may interfere with the development of the fetus' brain, which may lead to lifelong physical, mental and behavioural problems.
78
What are the social implications that alcohol has on society?
1. If someone drinks alcohol frequently, they may become addicted to alcohol, unable to stop drinking until they are drunk and their body becomes dependent on alcohol and he becomes an alcoholic.
2. Alcoholics may neglect their work and families
3. Alcoholics may exhibit violent behaviour, especially towards family members
4. People under the influence may tend to commit crimes.
