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Human Bio > The Digestive System [6] > Flashcards

The Digestive System [6] Flashcards

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1
Q

6 basic activities of the digestive system:

A

1) ingest food & water
2) mechanical digestion
3) chemical digestion
4) move food along alimentary canal
5) absorb nutrients into blood and lymph
6) eliminate material that is not absorbed

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2
Q

Define digestion

A

The process in which carbohydrate, protein, and fat molecules are broken down into products small enough to be absorbed into blood.

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3
Q

What do body cells require

A

Simple sugars, amino acids, fatty acids, vitamins, minerals, water

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4
Q

Purpose of mechanical digestion

A

Physical breakdown of food to increase SA, so chemicals can access more food and be more effective.

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5
Q

Where does mechanical digestion occur

A

Teeth grind food

Stomach churning

Small intestine: bile secreted from gall bladder, emulsifies fat into smaller droplets.

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6
Q

What occurs during chemical digestion

A

Enzymes (-ase) break down:

  • carbohydrates into glucose/fructose/galactose
  • proteins into peptides & amino acids
  • DNA & RNA into nucleotides
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7
Q

Alimentary canal and its organs

A

Continuous tube making up digestive system, along with associated organs (liver, pancreas, bile duct, gall bladder)

Mouth, oesophagus, stomach, small intestine, large intestine, anus

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8
Q

Mechanical digestion in mouth

A

Intake of food & mastication, teeth chew food.

In one jaw:
- 4 incisors (front teeth, cutting)
- 2 canines (pointy, tearing)
- 4 premolars & 6 molars (broad crowns with cusps, crushing and grinding)

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9
Q

Chemical digestion in mouth

A

Saliva, secreted by 3 pairs of salivary glands

Contains: mucus to lubricate food, salivary amylase (enzyme, digests starch into disaccharide maltose)

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10
Q

Function of tongue

A

Shapes chewed food into bolus, then moves up and back to push into pharynx

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11
Q

Structure & function of oesophagus

A

Double smooth muscle layer, as with the rest of alimentary canal:
- circular, fibres arranged in circles
- longitudinal, fibres along length of canal

Achieves peristalsis - circular muscle behind and ahead of bolus contracts and relaxes simultaneously to push food.

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12
Q

Mechanical digestion in stomach, and structure

A

Circular, longitudinal, and oblique muscle to churn food, mixing it with juices until it is converted into chyme.

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13
Q

Where does peristalsis occur

A

Throughout the whole canal

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14
Q

Structure of stomach mucosa

A

Gastric glands - located in gastric pits.

Has specialised cells that secrete each of the components of gastric juice

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15
Q

Structure and function of gastric juice

A

HCl - acidic, (pH 2-3), allows enzyme pepsinogen to activate into pepsin, which breaks down proteins into shorter peptides, and DNA and RNA

Mucus - protects stomach from acid

Digestive enzymes - pepsinogen

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16
Q

Duodenum

A

First part of small intestine, 25 cm. Most chemical digestion occurs here.

Receives bile and pancreatic juice

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16
Q

Pyloric sphincter

A

Thickening (constriction) of circular muscle at the end of the stomach to prevent contents from passing unless pushed by peristalsis

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17
Q

Jejunum

A

Middle section of s. intestine, with a lining suited for absorption of carbohydrates and proteins.

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18
Q

Ileum

A

Final part of s. intestine. Vitamin B12, bile salts, and remaining products of digestion are absorbed.

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19
Q

What substances influence digestion in the small intestine, and where do they come from

A

Pancreatic juice - produced by pancreas, secreted via bile duct

Bile - produced by liver, stored in gall bladder, secreted via bile duct

Intestinal juice - secreted by intestine (intestinal glands, secretory cells in villi)

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20
Q

Purpose of pancreatic juice, and enzymes it contains (ignore purpose of enzymes)

A

Neutralises acid from stomach (has high pH), and continues chemical digestion

Pancreatic amylase, pancreatic protease, pancreatic lipase, deoxyribonuclease, ribonuclease

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21
Q

Pancreatic amylase

A

Breaks down starch into maltose

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22
Q

Pancreatic protease

A

Breaks down proteins into smaller peptides

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23
Q

Pancreatic lipase

A

Breaks down lipids into fatty acids and glycerol

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24
Deoxyribonuclease and ribonuclease
Digest DNA and RNA
25
Bile
Contains bile salts which emulsifies fats into smaller droplets Mechanical digestion
26
Purpose of Intestinal juice and enzymes it contains (ignore purpose of enzymes)
Complete chemical digestion of carbohydrates, lipids and proteins Peptidase Sucrase/Maltase/Lactase Lipase
27
Purpose of peptidase, and location
Component of Intestinal juice, breaks down peptides into amino acids
28
Purpose of sucrase, maltase, and lactase
Digest disaccharides sucrose, maltose and lactose into monosaccharides glucose, fructose and galactose (not respectively)
29
What mechanical digestion occurs in the small intestine?
Segmentation - circular muscle narrows the intestine, which breaks up food and mixes it with juices and bile
30
How is a large SA achieved in the small intestine
6-7m Mucosa has folds extending into the interior Villi lines mucosa Microvilli extend reach of villi
31
Structure of villi and function
**1 cell thick** - easy diffusion **Lacteal** (lymph capillary) - allows fats to enter lymphatic system, as they are large and insoluble **Capillaries** - transport nutrients via blood to body **Microvilli** - increases SA
32
In which part of the small intestine is villi the longest
Jejunum, as it is the primary site of absorption.
33
How do muscles in the small intestine assist in absorption?
Movements brings villi into contact with different parts of food, as contents constantly change as new material enters from stomach.
34
How are amino acids absorbed in villi
Active transport through villi, then into capillaries
35
How are simple sugars absorbed in villi
Active transport through villi, then into capillaries
36
How are water and water-soluble vitamins absorbed in villi
Simple diffusion through villi, then into capillaries
37
How are fatty acids, glycerol, and fat-soluble vitamins absorbed in the villi, and why?
Simple diffusion through villi, then recombined into lipids as chylomicrons, then into lacteals (lead to lymphatic system) Enter lacteals because molecules are too big and insoluble to enter bloodstream.
38
Where are nutrients absorbed in capillaries transported to
Carries by hepatic portal vein to liver. Here: either removed for further processing, or remain in the blood to be carried to body.
39
Where are nutrients absorbed in lacteals transported to
Lymphatic system (in lymph), eventually emptying into blood through veins in upper part of chest.
40
Structure and features of large intestine
Caecum(and appendix), colon, rectum, anus 1.5 m long No villi/digestive juices Mucus secreted by lining Bacteria
41
Caecum
Pouch where small intestine joins with large intestine
42
Colon
Largest part of large intestine, inverted "U" shape
43
Structure and features of large intestine
Caecum(and appendix), colon, rectum, anus 1.5 m long No villi/Intestinal juices Mucus secreted by lining Bacteria
44
Caecum
Pouch where small & large intestines join
45
Colon
Longest part of large intestine, inverted "U" shape
46
Rectum
Place where contents of colon are pushed into via peristalsis. As walls stretch, process of **defecation** is triggered.
47
Structure and function of anus
External opening, circular muscle around it called *anal sphincter*. During defecation, muscle relaxes and faeces are expelled
48
Functions of large intestine
Absorb water, absorb vitamins and minerals, eliminate faeces
49
Purpose of bacteria in large intestine
Break down remaining organic compounds, and produce some vitamins
50
Contents of faeces
Water, undigested food (particularly cellulose), bacteria, bile pigments (gives colour), cells broken away from alimentary canal
51
Cause and effect of constipation
Cause: lack of roughage (cellulose, stimulates movement in canal), inactivity, emotional problems Effect: faeces are drier & harder, making defecation difficult
52
Causes of diarrhoea
Irritation of intestines, increasing peristalsis so contents move through before proper water absorption Triggers: pathogens, cancer, coeliac disease, lactose intolerance
53
What is diarrhoea and consequences (ignore causes)
Defecation of watery faeces May lead to dehydration as water is lost in intestines.
54
Bowel (colorectal) cancer and causes
Uncontrolled growth of cells in large intestine walls Diet: red/processed meat, low in fibre Overweight/obese/inactivity
55
What is coeliac disease
Condition where gluten (protein) in wheat/rye/barley triggers immune response that damaged villi Leads to malnourishment, as nutrients can't be absorbed Inherited, no cure.
56
Importance of soluble fibre in diet
Pectins, gums, mucilage from plants linked to lower cholesterol levels (fats trapped by fibre), decreased risk of heart disease & cancer, beneficial effects on blood glucose levels
57
What does maltose break down into
2 glucose
58
What does sucrose break down into
1 glucose, 1 fructose
59
What does lactose break down into
1 glucose, 1 galactose

Human Bio (6 decks)

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