Chapter 6 - Nutrition in Man Flashcards
1
Q
Define “nutrition”
A
The process by which organisms obtain food and energy for growth, repair and maintenance of the body
2
Q
What are the processes involved in nutrition?
A
- Ingestion
- Digestion
- Absorption and assimilation
- Egestion
3
Q
What happens in ingestion?
A
Food is taken into the body
4
Q
What happens in digestion?
A
Large food molecules are broken down into smaller soluble molecules
5
Q
What happens in absorption?
A
The digested food molecules are absorbed into the blood stream and into the cells.
6
Q
What happens in assimilation?
A
The absorbed food molecules are converted into new protoplasm or used to provide energy
7
Q
What happens in egestion?
A
Undigested food is removed from the body
8
Q
The human digestive system consists of the ________ and the ________
A
alimentary canal
organs associated with it
9
Q
What are the organs in the digestive system? [13]
A
Mouth, salivary gland, pharynx, oesophagus, stomach, liver, gall bladder, pyloric sphincter, pancreas, small intestine, large intestine, rectum, anus
10
Q
Food enters the body through the ________, which leads into the ________
A
mouth
buccal cavity
11
Q
Digestion of food is begun in the mouth by the ________, ________ and ________
A
teeth
salivary glands
tongue
12
Q
The pharynx connects the ________ to the ________ and ________
A
buccal cavity
oesophagus
larynx
13
Q
The pharynx leads to the ________, which in turn leads to the lungs
A
trachea
14
Q
The pharynx is part of both the ________ system and ________ system
A
digestive
respiratory
15
Q
The larynx has a slit-like opening called the ________, which is covered by a flap-like tissue known as the ________
A
glottis
epiglottis
16
Q
If both food and air must pass through the pharynx to enter the oesophagus and trachea, how is food prevented from entering the trachea when swallowing?
A
- During breathing, air passes into the trachea, the larynx moves downwards and the glottis is open.
- During swallowing, the larynx moves upwards and the epiglottis covers the glottis, preventing food particles from entering the trachea.
17
Q
Oesophagus
A
A narrow, muscular tube that extends to the stomach
18
Q
Stomach
A
- A distensible muscular bag
- Food in the stomach is digested by gastric juice secreted by the gastric glands
19
Q
The wall of the oesophagus is made up of two layers of muscles: ________ and ________ muscles
A
longitudinal
circular
20
Q
Small intestine
A
- Food passes from the stomach to the small intestine
- Consists of the duodenum, jejunum and ileum
- About 6m long
21
Q
Large intestine
A
- Small intestine leads to it
- Consists of the colon and rectum
- About 1.5m long
22
Q
What are the organs associated with the gut?
A
Liver, gall bladder and pancreas
23
Q
Function of the gall bladder
A
Stores bile temporarily
24
Q
Structure of the liver
A
- Made up of 5 lobes
- 3 blood vessels are attached to the lower surface of the liver: hepatic portal vein, hepatic vein, hepatic artery
25
Function of the pancreas
- Secretes pancreatic juice, which contains digestive enzymes
- Secretes the hormones insulin and glucagon, which play an important role in controlling the concentration of glucose in the blood and carbohydrate metabolism
26
What is peristalsis?
The rhythmic, wave-like muscular contractions in the wall of the alimentary canal
27
Function of peristalsis
- Helps the movement of food along the gut
| - Enables food to be mixed with digestive juices
28
What are antagonistic muscles?
A pair of muscles whose movements oppose each other i.e. when one muscle contracts, the other relaxes and vice versa
29
The ________ and _________ muscles in the wall of the alimentary canal are antagonistic muscles
circular
| longitudinal
30
How do the antagonistic muscles in the wall of the alimentary canal help in the movement of food?
1. Wall contracts. The circular muscles contract and the longitudinal muscles relax. The food is pushed forward.
2. Wall dilates. The longitudinal muscles
contract and the circular muscles relax. This
widens the lumen to allow food to enter.
31
What is physical digestion?
- Involves mechanical break-up of food into smaller particles
- By chewing
- By peristalsis
32
What is chemical digestion?
- Involves break-down/hydrolysis of large molecules in food into small soluble molecules that can be absorbed
- Involves hydrolytic reactions catalysed by digestive enzymes
33
How is food digested in the mouth?
| salivary glands
The salivary glands in the mouth secrete saliva, which is mixed with the food by the tongue.
34
How is food digested in the mouth?
| saliva
- The saliva contains mucin which softens the food
| - Salivary amylase digests starch to maltose
35
How is food digested in the mouth?
| chewing
The chewing action of teeth breaks up larger pieces of food into smaller pieces (physical digestion)
36
How is food digested in the mouth?
| tongue
The tongue rolls the food into boli (small, slippery, round masses).
37
How is food digested in the oesophagus?
Peristalsis in the walls of the oesophagus and gravity push the bolus into the stomach.
38
How is food digested in the stomach?
- When the bolus enters the stomach, it stimulates the release of gastric juice by the gastric glands.
- Peristalsis in the walls of the stomach mixes the food with the gastric juice.
39
What is gastric juice?
A dilute solution of hydrochloric acid, mucus and the enzyme, pepsin.
40
Function of hydrochloric acid in gastric juice [4]
- stops the action of salivary amylase by denaturing it
- converts pepsinogen (the inactive form) into pepsin (the active form)
- provides an acidic medium for the action of pepsin
- kills potentially harmful microorganisms in food
41
Function of pepsin in gastric juice
Digests proteins to polypeptides
42
Food remains in the stomach for ________ hours
3 to 4
43
What is chyme?
Partially digested food in the stomach, which passes into the duodenum when the pyloric sphincter relaxes
44
Chyme in the duodenum stimulates the release of... [3]
- pancreatic juice by the pancreas
- bile by the gall bladder
- intestinal juice by the small intestine
45
Pancreatic juice, bile and intestinal juice are ________ fluids which ________ the acidic chyme
alkaline
| neutralise
46
The alkaline medium is needed for ...
the action of intestinal and pancreatic enzymes
47
In the small intestine, the gall bladder ...
releases its stored bile
| The bile passes through the bile duct into the duodenum
48
In the small intestine, the pancreas ...
secretes pancreatic juice
49
Pancreatic juice contains the enzymes ________, ________ and ________
pancreatic amylase
pancreatic lipase
trypsinogen
50
In the small intestine, the intestinal glands ...
secrete intestinal juice
51
Intestinal juice contains the enzymes ________, ________, ________, ________ and ________
These enzymes ________ food molecules
```
maltase
sucrase
lactase
peptidases
intestinal lipase
digest
```
52
Amylases act on ________
starch
53
Proteases act on ________
proteins
54
Lipases act on ________
fats
55
How are carbohydrates digested in the mouth?
starch --salivary amylase--> maltose
56
How are carbohydrates digested in the small intestine?
starch --pancreatic amylase--> maltose --maltase--> glucose
lactose --lactase--> glucose + galactose
sucrose --sucrase--> glucose + fructose
57
The end products of carbohydrate digestion are ________
simple sugars (glucose, fructose and galactose)
58
How are proteins digested in the stomach?
proteins --pepsin--> polypeptides
59
How are proteins digested in the small intestine?
proteins --trypsin--> polypeptides --peptidases--> amino acids
60
The end products of protein digestion are ________
amino acids
61
How are fats digested in the small intestine?
- Bile salts emulsify fats
- They break up the fats (fat globules) into small fat droplets that are suspended in water
fats --pancreatic and intestinal lipase--> fatty acids + glycerol
62
The end products of fat digestion are ________
fatty acids and glycerol
63
The small intestine is the ________ of the products of digestion
site of absorption
64
Factors affecting the rate of absorption [3]
- surface area
- thickness of separating membrane
- concentration gradient
65
Absorption at the small intestine is made more efficient with ... [3]
- large surface area
- thin separating membrane
- steep concentration gradient
66
How is the small intestine adapted for absorption? [4]
- The surface area to volume ratio is increased for absorption
- The thin walls of the villi make it easy for nutrients to pass through to the bloodstream
- The length of the small intestine (~6m) increases the time for absorption
- Many blood capillaries are present to help carry away absorbed nutrients quickly
67
Increasing surface area to volume ratio for absorption: ________ in the inner wall of the small intestine
numerous folds (villi)
68
Increasing surface area to volume ratio for absorption: ________ in the epithelium of villi
microvilli
69
Presence of blood capillaries for absorption: ________ help to transport amino acids and glucose to the body
blood capillaries network
70
Presence of blood capillaries for absorption: ________ helps to transport fats to the body
lacteal/lymphatic capillary
71
Absorption of nutrients into the small and large intestines by active transport [1]
Glucose and amino acids are absorbed into the epithelial cells of the villi by active transport (from the lumen into the epithelial cells)
72
Absorption of nutrients into the small and large intestines by diffusion [2]
- Glucose and amino acids in the epithelial cells are transported into the blood capillaries of the villi via facilitated diffusion
- Glycerol and fatty acids diffuse into the epithelium, and combine to form minute fat globules which enter the lymphatic capillary
73
What happens to the undigested and unabsorbed matter?
They are stored temporarily in the rectum and discharged as faeces through the anus (egestion)
74
The hepatic portal vein is formed by ...
the blood capillaries that supply the small intestine
75
What is the function of the hepatic portal vein?
Transports absorbed sugars and amino acids to the liver
76
What happens to the absorbed sugars in the liver?
- Most of the sugars are converted to glycogen and stored
| - Glucose is transported by the hepatic vein to the different parts of the body
77
The hepatic artery transports blood ________ the liver
| The hepatic vein transports blood ________ the liver
into
| out of
78
Glucose is the ________ for all cells in the body.
energy source
79
What is insulin?
A hormone that stimulates the liver to convert excess glucose to glycogen
80
What is the function of insulin?
Regulates the amount of glucose that enters the blood stream
81
What happens to the absorbed amino acids in the liver?
- Excess amino acids are converted to urea by deamination
| - Amino acids are transported by the hepatic vein to the different parts of the body to be utilised
82
Functions of amino acids distributed by hepatic vein [2]
- Used for growth and repair in cells
| - Used to form enzymes and hormones
83
Functions of the liver [5]
- Regulation of blood glucose concentration
- Production of bile
- Protein synthesis
- Storage of iron
- Detoxification
84
Liver function 1: Carbohydrate metabolism
- The liver keeps the blood glucose concentration constant (~70–90 mg/100 cm3 of blood)
- The liver is stimulated by insulin and glucagon to store and release glucose respectively
85
How do insulin and glucagon control carbohydrate metabolism?
1. Too much glucose in blood → Pancreas secrete insulin → Liver converts glucose into glycogen → Blood glucose level decreases
2. Too little glucose in blood → Pancreas secrete glucagon → Liver converts glycogen into glucose → Blood glucose level increases
86
Liver function 2: Production of bile
The liver produces bile, which emulsifies fats
87
Liver function 3: Protein synthesis
The liver uses amino acids to synthesise proteins such as prothrombin and fibrinogen
88
Deamination of excess amino acids in the liver
- The amino group of amino acids are removed(deamination) and converted to urea in the liver
- The carbon residues of amino acids from deamination are converted to glucose in the liver
89
Liver function 4: Storage of iron
Iron is stored in the liver and used in the synthesis of new red blood cells
90
When red blood cells are worn out, ...
they are destroyed in the spleen and their haemoglobin is sent to the liver to be ‘recycled’
91
Breakdown of haemoglobin produces ________ and ________
iron
| bile
92
Liver function 5: Detoxification
- The process of converting harmful substances into harmless products
- Enzyme alcohol dehydrogenase converts alcohol into acetaldehyde
(alcohol --alcohol dehydrogenase--> acetaldehyde)
93
Acetaldehyde is used as ________ in cells
a source of energy
94
Harmful effects of excessive alcohol consumption [5]
- Reduced self-control
- Depressant
- Effect on reaction times
- Damage to liver
- Social implications
95
Alcohol stimulates ________ in the stomach
acid secretion
| excess acid increases risk of gastric ulcers
97
Alcohol effect 2: depressant
Slows down some brain functions
98
Alcohol effect 3: reaction times
Slurred speech
Blurred vision
Poor muscular coordination
99
Alcohol effect 4: damage to liver
May lead to liver cirrhosis (liver cells are destroyed)
100
Alcohol effect 5: social implications
Addiction
| Tendency to exhibit violent behaviour and commit crimes
