Chapter 9- The Digestive System Flashcards
(62 cards)
1
Q
What does the digestive system do
A
- extracts nutrients from the food we eat and absorbs them into the body for use by the cells
- the nutrients provide materials for cell growth, cell re production, secretion and other metabolic processes
2
Q
What is the alimentary canal
A
- a continuous tube that runs from the mouth to the anus
- with associated organs (pancreas, gall bladder) the alimentary canal makes up the digestive system
3
Q
Where are the nutrients absorbed in the alimentary canal
A
- the lining.
4
Q
What do body cells require to function normally
A
Simple sugars Amino acids Fatty acids Vitamins Minerals Water
5
Q
Vitamins, minerals and water
A
- in the form of small molecules that are able to pass through the differentially permeable membrane
6
Q
Simple sugars, amino acids, fatty acids (eaten as complex carbohydrates, proteins and fats)
A
- large molecules that mist be broken down into smaller ones before they can be absorbed
7
Q
Digestion
A
The process in which carbohydrates, fats and proteins are broken down enough to be absorbed into the blood and into the cells
8
Q
Organs of digestive system are structured and arranged so that can carry out what activities
A
. Ingestion of food and water
. Mechanical digestion of food
. Chemical digestion of food
. Movement if food along the alimentary canal
. Absorption of digested food and water along the blood and lymph
. Elimination of material that is not absorbed
9
Q
Mouth cavity
A
. Mechanical digestion of teeth occurs
. Chemical digestion of starch by the saliva occurs which breaks down the large molecules into smaller ones
10
Q
Salivary glands
A
. Three pairs of glands produce saliva which dissolves food so it can be tasted
11
Q
What does saliva contain
A
Mucus- that lubricates mouth and food and holds food in a lump for swallowing
Salivary amalayse- begins starch digestion
12
Q
Pharynx
A
. Back of mouth cavity
. By moving upwards and backwards the tongue pushes the food into the pharynx for swallowing
13
Q
Oesophagus
A
. Carries food from the mouth to the stomach
. Passes through the diaphragm and into the abdominal cavity
14
Q
Liver
A
. Produces bile which is stored and concentrated in the gall bladder
. Bile emulsifies lipids in the small intestine
.
15
Q
Stomach
A
. Mechanical digestion by churching action
. Chemical digestion by pepsin which begins protein digestion
. In infants rennin coagulates milk protein
16
Q
Pyloric sphincter
A
Band of circular muscle that regulates flow of material from stomach to duodenum
. Prevents the stomach contents from moving through unless it is moved by peristalsis, after two to eight hours the stomach contents are gradually pushed into the small intestine
17
Q
Duodenum
A
First part of the small intestine
18
Q
Ascending colon
Transverse colon
Descending colon
A
Longest part of the large intestine that absorbs water, minerals and vitamins
19
Q
Pancreas
A
Produces pancreatic juice containing enzymes for digesting proteins lipids and nucleic acids
20
Q
Caecum
A
First part of the large intestine
21
Q
Small intestine description
A
. Six metres long
. Lining secretes intestinal juice which contains enzymes
. Internal surface is lined with villi for absorption of digested food
22
Q
Anus
A
. Opening surrounded by anal sphincter
. A muscle that can be voluntarily controlled
23
Q
Rectum
A
Final part of large intestine in which faeces are formed
24
Q
Appendix
A
Has no function in humans
25
What occurs in the mouth
. Intake of food (ingestion)
. Action of jaw and teeth (begin mechanical digestion) where food is broken up into small pieces
. As was the food is chewed it is mixed with saliva secreted into the mouth cavity by three pairs of salivary glands
.
26
The teeth and mechanical digestion
. There are four types of teeth and each has a different function
. The four types of teeth include incisors, canines, pre-molars and molars
. The same number of teeth that occur in the lower jaw occur in the upper jaw
. After chewing the food is formed by the tongue into a rounded lump to swallow
. To swallow the tongue move upwards and backwards pushing the food lump into the back of the mouth which is the pharynx
. The pharynx leads into the oesophagus which then leads into the stomach
27
Incisors
. There are four of them
| . They are chisel shaped teeth used for biting or cutting
28
Canines
. There is one on each side of the incisors
. They are conical teeth used for tearing
. the human canines are the same length as the other teeth but in carnivorous animals the canines a much longer than the other teeth and the tearing role is more important
29
Pre-molars
. Two on each side of the jaw
30
Molars
. There are six of which have three on each side of the jaw behind the pre-molars
. Pre-molars and will have broad crowns with rounded cusps the cusps of the teeth of one jaw fit into the depressions on the surface of teeth on the other jaw making the pre-molars and molars ideal for crushing and grinding food
31
Muscle layer in the oesophagus
. Like the rest of the alimentary canal, the wall of the oesophagus has a double layer of muscle
. Circular muscle with muscle fibres arranged in a circle and longitudinal muscle with fibres arranged along the length of the canal
32
Peristalsis
. As lump of food enters the pharynx and oesophagus the circular muscle behind it contracts while the muscle in front of the food relaxes which pushes food along the oesophagus
33
The stomach
. Oesophagus passes through the diaphragm and then opens up into the stomach
. No nutrients are absorbed in the stomach because the internal surface is covered with a thick layer of mucus
. Some alcohol and drugs can be absorbed in the stomach
. At the lower end of the stomach there is a thickening of the circular muscle which results in a constriction called the pyloric sphincter
34
Mechanical digestion in the stomach
. Achieved by waves in muscular contraction that move along the stomach wall
35
Muscle in the stomach wall
. Unlike the rest of the alimentary canal the stomach has an oblique muscle layer as well as a circular and longitudinal layer
. The oblique muscle layer allows the stomach to contract in a variety of ways to church the food snd mix it with the stomach juices until the food is converted into a thick soupy liquid
36
Mucosa
. Surrounds the lining of the stomach
| . Secretes gastric juice which is responsible for the chemical digestion in the stomach
37
Gastric juice
. Secreted by the gastric glands
. Contains hydrochloric acid, mucus and digestive enzymes and each is secreted by a different type of cell in the gastric pits
38
Gastric glands
. Located in narrow tube like structures called gastric pits
| .
39
Chemical digestion
. Brought about by digestive enzymes in the gastric juice
| . Most chemical activity in the stomach is called concerned with the start of of protein digestion
40
The small intestine
. Approx six metres long and the longest part of the alimentary canal
. It receives material pushed through the pyloric sphincter from the stomach
. First part of the small intestine is called the duodenum which extends from the bottom end of the stomach in a curve around the pancreas
.
41
Digestion in the small intestine
. Occurs under the influence of: intestinal juice secreted by glands in the lining, pancreatic juice which is secreted by the pancreas and bile secreted by the liver and stored in the gall bladder
. Pancreatic juice enters the duodenum through a duct and helps neutralise the acid that has come with the material of the stomach
. Many enzymes involved with the digestion of food are contained in the pancreatic juice
42
What enzymes are contained in the pancreatic juice that are involved with digestion and what do they break down
Pancreatic amalayse which breaks down starch
Trypsin which spilts proteins into smaller units
Ribonuclease and deoxyribonuclease which digest DNA and RNA
Pancreatic lipases breaks down fats into fatty acids and glycerol
43
Bile in digestion in the small intestine
. Doesn't contain any enzymes
. But bile salts are important in the digestion of fats
. acts as a detergent and emulsify the fat breaking it into tiny little droplets and this is a form of mechanical digestion which increases the surface area on which the lipases can act to bring about chemical digestion of fats
. Enters duodenum through a duct
44
Intestinal juice
Contains many enzymes that complete the digestion of carbohydrates, proteins and lipids and lipids
. When chemical digestion in the stomach has been completed the complex carbohydrates will have been broken down into simple sugars, the proteins into amino acids and the fats into fatty acids and glycerol
45
What enzymes are in intestinal juice and what do they break down
- complex carbohydrates breakdown
- pancreatic protease breaks down amino acids into small chains of amino acids
- lipases break down fats into fatty acids and glycerol
46
Where are the products of digestion along with water vitamins and minerals absorbed
. Through the walls of the small intestine and into the blood
. Nutrients are absorbed through the internal surface of the small intestine
47
How is a large internal surface area of the small intestine achieved
- the small intestine is very long (6m)
. The inner lining known as the mucosa, has folds that extend into the interior
. The mucosa has small finger like projections called villi that extend from the folded surface
. The cells covering the outside of the villi have tiny microscopic projections from their external surfaces and these are called microvilli
48
Structure of villi
. Suited to its function of nutrient absorption
. Each villi is 1mm long and 1 cell thick
. Inside villus is a lymph capillary called a lacteal
. Lacteal is surrounded by a network of blood capillaries
. Absorption is further enhanced by continual movement of villi brought about by movement of intestinal wall
. Moving brings the villi in contact with different parts of the intestinal contents
. These contents are constantly changing as new material is emptied into the small intestine from the stomach
49
Absorption of nutrients through the villi
. Absorption through constant movement of the villi
. Simple diffusion because there is a higher concentration of nutrient in the interior of the small intestine than in the cells lining the villi
. Active transport- cells of the villi using energy to take in nutrients against the concentration gradient which taking it molecules from a lower concentration to a higher concentration
50
What gets absorbed from the walls of the villi to the blood capillaries, and where does it go after?
```
Simple sugars
Amino acids
Water
Water soluble vitamins
. When they get absorbed into the blood capillaries they get carried by the hepatic portal vein to the liver and they then get removed for further processing or they remain in the blood to get carried to other body cells
.
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51
What substances enter the lacteals and where do they go after?
. Fatty acids and glycerol recombine to form fats and fat soluble vitamins and they enter the lacteals
. These substances get transported to the lymph system which eventually empties into the blood through veins in the upper part of the chest
52
Structure of large intestine
. 1.5m long
. Larger in diameter than the small intestine
. No digestive juices are secreted
. Lining secrets mucus
. Movement of materials is slow (18-24 hours)
53
Movement and absorption of materials in the large intestine
. Movement of materials is slow
. When materials are moving through is when most of the water is absorbed and contents become more solid
. Bacteria in large intestine break down remaining organic compounds, some bacteria produce vitamins which are then absorbed through the walls and into the blood and mineral nutrients are also absorbed
.
54
Faeces
. Semi solid material left after water absorption and bacterial action make up the faeces
.
55
What do faeces contain
```
Water
Undigested food
Bacteria
Bile pigments
Remains of cells that have broken away from the internal lining of the alimentary canal
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56
elimination/excretion
. Removal of metabolic waste that has been produced by the chemical activity of the body cells except the bile pigments, the contents of the faeces isn't metabolic waste
57
Diet affects absorption in the alimentary canal
. Speed of movement of alimentary canal depends of the size and the contents of a meal
. Large meal causes greater stretching of the stomach and material is pushed into the small intestine much more quickly when the stomach is less swollen (large meals take longer)
. High protein or high fat content meals take slower to move from the stomach to small intestine
. Alcohol and caffeine speed up movements of the stomach
58
Constipation
. Occurs when the movement of the large intestine is reduced and the contents remain there for a long period of time
. As water is absorbed the faeces become drier and harder than usual and defection can therefore be painful
. Caused by lack of roughage in diet (cellulose, plant foods)
. Humans have no enzymes to digest cellulose buts its important because it speeds up movement of the alimentary canal
. Also caused by lack of exercise and emotional problems
59
Diarrhoea
. Frequent defecation of watery faeces
. Caused by irritation of the small or large intestine
. Irritation increases peristalsis so that the contents are pushed through quickly without adequate absorption
. May be result of bacterial or viral infection
. Bacteria that produce food poisoning may cause diarrhoea
. Cholera can cause severe diarrhoea and can cause death because of dehydration
60
Bowel cancer
. Colorectal cancer
. Uncontrolled growth of cells in the wall of the large intestine
. May be linked to diet, high alcohol consumption and smoking
. A diet in high red and processed meat and low in fibre may increase risk of developing bowel cancer
. Being overweight or physical inactivity can also be risk factors
61
Importance of soluble fibre in the diet
. Soluble and insoluble fibre are only found in plant foods
. Soluble fibre includes- pectins, gums, mucilage
. Soluble fibre is linked to low cholesterol levels, decreased risk of heart disease and cancer, and beneficial effects on blood glucose levels
. Fats in the intestine are trapped by soluble fibre which helps absorption of the body
62
Coeliac
. People who are unable to tolerate gluten which is found in wheat, rye and barley
. If food is eaten containing gluten the body responds by damaging or destroying the villi
. Without healthy villi nutrients cannot be absorbed
. Symptoms include muscle cramps, joint pain or tingling in the legs
. Its inherited and only cure is to follow a gluten free diet
. Some people don't have symptoms
