CH 6 The Digestive System Flashcards
1
Q
What is active transport?
A
The use of energy to move substances, usually ions, across a cell membrane
2
Q
What is the alimentary canal?
A
The tube via which food passes through the body, consisting of the mouth, oesophagus, stomach and intestines
3
Q
What is bile?
A
A secretion of the liver, stored in the gall bladder and released into the small intestine
4
Q
What are bile salts?
A
Substances that breakdown fats into tiny droplets
5
Q
What is a bolus?
A
A ball-like structure of food and saliva
6
Q
What is a canine?
A
The pointed tooth between the incisors and premolars
7
Q
What is chemical digestion?
A
The breakdown of food to small molecules by chemicals
8
Q
What is chyme?
A
The semifluid mass of partially digested food that leaves the stomach
9
Q
What is a circular muscle?
A
Smooth muscle with fibres arranged in a circle around an organ
eg. the stomach
10
Q
What is coeliac disease?
A
An autoimmune disease due to the immune system reacting to gluten
11
Q
What is colorectal cancer?
A
Cancer in the colon and rectum (bowel cancer)
12
Q
What is constipation?
A
A condition in which defection is difficult, with faeces being hard and dry
13
Q
What is deoxyribonuclease?
A
An enzyme in pancreatic juice that digests DNA
14
Q
What is diarrhoea?
A
The frequent passing of watery faeces
15
Q
What is digestion?
A
The mechanical breakdown of food to small molecules that can be absorbed
16
Q
What is the digestive system?
A
The system that breaks down the food taken in the body ready for absorption into the body
17
Q
What is elimination?
A
Removal of indigestible material, bacteria and bile pigments from the body
18
Q
What does emulsify mean?
A
To mix two liquids that would not normally mix
19
Q
What is faeces?
A
Material passed out of the rectum
20
Q
What is the gastric gland?
A
The secretory unit of the stomach located in gastric pits, produces gastric juice
21
Q
What is gastric juice?
A
The digestive juice secreted by the glands of the stomach
22
Q
What is an incisor?
A
The narrow-edged tooth at the front of the mouth, use for cutting
23
Q
What is ingestion?
A
The intake of food, liquids or drugs into the mouth
24
Q
What is intestinal juice?
A
The digestive juice secreted by the glands of the small intestine
25
What is lacteal?
A lymph capillary in the small intestine; absorbs fat from digested food
26
What is the large intestine?
The part of the intestine between the small intestine and the anus; it is made up of the caecum, colon and rectum
27
What is a longitudinal muscle?
Smooth muscle with fibres arranged length wise along an organ
28
What is mastication?
The process of chewing; to grind or crush food with teeth
29
What is mechanical digestion?
The mechanical breakdown of food into small particles
30
What is microvilli?
Microscopic projections from the membranes of cells lining the small intestine; they increase the surface area for absorption
31
What is a molar?
A grinding tooth at the back of the mouth
32
What is mucosa?
A mucous membrane in particular the mucous membrane that forms the internal lining of the alimentary canal
33
What is the oesophagus?
The tube that carries food from the throat to the stomach
34
What is pancreatic amylase?
An enzyme in pancreatic juice that breaks down starch
35
What is pancreatic juice?
The liquid secreted by the pancreas
36
What is pancreatic lipase?
An enzyme in pancreatic juice that breaks down fats
37
What is peristalsis?
Waves of muscular contraction that push food along the alimentary canal
38
What is the pharynx?
The throat; the pharynx joins the mouth cavity to the oesophagus and larynx
39
What is a premolar?
The teeth between the canine and molars
40
What is the pyloric sphincter?
A ring of smooth muscle between the stomach and the duodenum
41
What is ribonuclease?
An enzyme in pancreatic juice that digests RNA
42
What is saliva?
A fluid secreted into the mouth by salivary glands to begin digestion of food
43
What is the salivary gland?
Gland in the mouth that secretes saliva
44
What is segmentation?
A process occurring in the small intestine which uses the contraction of circular muscles to push the chyme into segments, mixing it with digestive juices
45
What is the small intestine?
The longest part of the alimentary canal; receives material from the stomach
46
What is the stomach?
A muscular organ the receives food from the oesophagus and mixes it with acid and enzymes to form chyme
47
What is trypsin?
An enzyme in pancreatic juice that breaks down protein
48
What is villi?
Projections from the internal lining of the small intestine
49
What do carbohydrates, proteins and fats breakdown to?
Carbohydrates- simple sugars
Proteins- amino acids
Fats- fatty acids and glycerol
50
What processes does mechanical digestion do in the mouth, stomach and small intestine?
Mouth- the teeth cut, tear and grind the food
Stomach- churning action in the stomach breaks down the food further
Small intestine- gall bladder releases bile into the small intestine> bile salts act as emulsifying agents, breaking down fat into smaller droplets
51
Explain the mouth:
- Ingestion of food occurs at the mouth
- the food is chewed (mastication)
- chemical and mechanical digestion commences before the food is swallowed
>Saliva (chemical)
- mucous to lubricate
- salivary amylase to commence the chemical digestion of starch into maltose
>Teeth (mechanical)
- 4 incisors for biting and cutting
- 2 canines for tearing
- 4 premolars for for crushing and grinding
- 6 molars for crushing and grinding
52
Explain the oesophagus:
- a bolus from the mouth and the pharynx goes into the oesophagus
- double muscle layer, contains circular and longitudinal muscle
- then peristalsis occurs to move the bolus downwards assisted with mucous that lubricates the inner lining
53
Explain the stomach:
- mechanical digestion in the stomach is achieved by waves of contractions along the stomach wall
- chemical digestion is achieved through the secretion of enzymes in the stomach
- the stomach has a third muscle layer called the obliques muscle layer which allows the stomach to contract in a variety of waves to churn the food and mix it with the stomach juices until the food is converted to a thick mixture called chyme
- the lining of the stomach (the mucosa) is specialised for the secretion of gastric juice by gastric glands
- the acidic environment allows the enzyme pepsinogen to convert to pepsin (active form) and also breaks down DNA and RNA
- alcohol and some drugs are absorbed in the stomach but not nutrients as there is a thick layer of mucous
54
Explain gastric juice:
- contains HCL, mucous and digestive enzymes
- responsible for chemical digestion in the stomach
- pH is approximately 2-3 due to the hydrochloric acid
55
Explain the pyloric sphincter:
- the lower end of the stomach there is a thickening of the circular muscle which results in a constriction
- the constriction is to prevent the stomach contents moving through
56
Explain the small intestine?
- 6-7m in length
- receives material from the pyloric sphincter
- mechanical digestion continues through segmentation
- contractions help break up the bolus and mix it with juices and bile
- chemical digestion occurs under the influence of pancreatic juice, bile and intestinal juice
57
What are the 3 regions of the small intestine?
1. Duodenum- mostly chemical digestion occurs
2. Jejunum- lining allows effective absorption of carbohydrates and proteins
3. Ileum- vitamin B12, bile salts and any remaining products of digestion are absorbed
58
What are the components of pancreatic juice?
Pancreatic amylase- breaks down starch to maltose
Pancreatic protease- splits proteins into peptides
Pancreatic lipase- breaks down fats to fatty acids and glycerol
Deoxyribonuclease/Ribonuclease- enzymes that digest RNA and DNA
59
Explain bile:
- secreted into the duodenum through the common bile duct
- contains bile salts that act like detergent and emulsifies fats into tiny droplets
- mechanical digestion as it increases surface area
60
Explain intestinal juice:
- contains enzymes that complete the breakdown of proteins, carbohydrates and lipids
>Peptidase- breaks down peptides into amino acids
>Sucrase, lactase and maltase> breaks these down into glucose, fructose and galactose
>Lipases- break down lipids into fatty acids and glycerol
61
How is a large surface area required In the system?
- small intestine is very long 6-7m
- the mucosa (inner lining) has folds extending into the interior of the small intestine
- 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 surface called microvilli
62
Explain villi and their function:
- the structure of villi is suited to its function of nutrient absorption
- each villus is 1mm long and is covered with a layer of cells
- in the villus is a lymph capillary called a lacteal which is surrounded by.a network of blood capillaries
63
What happens to different nutrients in the small intestine?
- fatty acids, glycerol and fat soluble vitamins goes into the lacteal
- everything else gets absorbed into the blood
- water and water soluble vitamins are absorbed by diffusion
64
Explain the large intestine?
- 1.5 m long
- made up of the caecum, colon, rectum and anus
- no villi or digestive juices are secreted but a large amount of mucous is
- movement is slow taking 18-24 hours
- water becomes absorbed so the contents get more solid
- bacteria breaks down most of the remaining organic compounds
- the semi solid material left makes up the faeces
65
Describe what faeces is:
- contains water, undigested food material, bacteria, bile pigments and the remains of cells that have broken from the internal lining of the alimentary canal
- Passes through the rectum and anus to the exterior of the body
- this is "defamation" which is best described as "elimination"
66
Explain the effect of diet on the alimentary canal:
- size and contents of a meal effect how fast it moves through the alimentary canal
Size> the greater the size, the greater the stretch of the stomach which pushes material to the small intestine faster
Contents>
- high protein/fat content slows movement from the stomach to the small intestine
- alcohol and caffeine stimulate the movement
67
Explain constipation:
- when the movement of the large intestine is reduced and the contents remain there for a long time
- water is absorbed and faeces becomes drier and harder
68
What are the causes of constipation?
- caused by lack of roughage in the diet which contains cellulose (insoluble fibre and component of plant foods)
- lack of exercise
- emotional problems
69
Explain diarrhoea:
- frequent defecation of watery faeces
-caused by the irritation of the small or large intestine
>Irritation may be caused by
- a bacteria
- a virus
- a parasite
- cancer such as bowel cancer
- coeliac disease
- lactose intolerence
70
What is the importance of soluble fibre in a diet?
- linked to lower cholesterol levels in the blood, decreased risk of heart disease and cancer and beneficial effects on blood glucose levels
- fats are trapped by soluble fibre preventing their absorption by the body
- good sources of soluble fibres is fruit, vegetables, oat bran, barley and soy products
71
Explain bowel cancer:
- uncontrolled growth of cells in the wall of the large intestine
- may be linked to diet, high alcohol consumption or smoking
- a diet high in red and processed meat and low in fibre (fruit and veg) may increase the risk as well as being overweight
72
Explain coeliac disease:
- unable to tolerate a protein called gluten (found in wheat, rye and barley)
- if it is ingested their immune system responds by damaging or destroying their villi therefore cannot absorb nutrients and person becomes malnourished
>Symptoms vary but include:
- muscle cramps
- joint pain or tingling in legs
>Treatment
- having a gluten free diet
- inherited and no cure
