digestive system

Question 1

functions of digestive system

Answer 1

1. ingestion of food and water
2. mechanical digestion of food
3. chemical digestion of food
4. movement of food along the alimentary canal
5. absorption of digested food and water into the blood and lymph
6. elimination of material that is not absorbed

Question 2

nutrients

Answer 2

• carbohydrates
• proteins
• lipids (fats)
• vitamins
• minerals
• water

Question 3

carbohydrates

Answer 3

Carbohydrates break up into simple sugars, Amylase acts on carbohydrates (starch) resulting simple sugars (e.g. glucose)

function: source of energy and movement

Question 4

lipids

Answer 4

Lipids (fats) break up into fatty acids and glycerol, Lipase acts on lipids resulting fatty acids

function: energy reserves and insulation

Question 5

proteins

Answer 5

Proteins break up into amino acids, Protease acts on proteins resulting amino acids

function: repair and growth

Question 6

what is digestion

Answer 6

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

Question 7

mechanical digestion: definition and location

Answer 7

Mechanical digestion = physical breakdown of food particles

• The mouth – teeth cut, tear and grindfood
• The stomach – churning action in thestomach breaks the food down further
• The small intestine – The gall bladderreleases bile into the small intestine. Bile salts act as emulsifying agents, breakingfat down into smaller droplets

Question 8

effect of mechanical digestion on surface area

Answer 8

Mechanical digestion increases surface areawhich allows more effective chemicaldigestion, as the chemicals can access more ofthe food

Question 9

chemical digestion

Answer 9

chemicals break down large, complex molecules into smaller, simpler molecules. Molecules are then small enough to beabsorbed into the bloodstream, chemical digestion achieved by enzymes (catalysts which increase reaction rate)

Question 10

alimentary canal

Answer 10

continuous tube that runs from mouth to anus, it is the lining of the alimentary canal that absorbs nutrients

• the alimentary canal and associated organs (pancreas & gall bladder) make up digestive system

Question 11

mastication

Answer 11

process in which food is chewed
The action of the jaws & teeth begin mechanical digestion, mastication

Question 12

bottom teeth + function

Answer 12

• Fourincisors(biting and cutting)
• Twocanines(tearing)
• Fourpremolars, two on each side of the jaw
• Sixmolars, threeon eachside of the jaw. Third molars = Wisdom teeth (crushing and grinding)

Question 13

tongue function

Answer 13

shapes food into a bolus - to swallow, the tongue moves upwards & backwards,pushing the bolus to the pharynx which leads to theoesophagus

Salivary glands secrete salivary amylase which breaks down carbohydrates into disaccharides.

Question 14

salivary glands

Answer 14

Three pairs of salivary glands secrete saliva (fluid) containing salivary amylase which lubricates the food and breaks down carbohydrates into disaccharides.

Question 15

oesophagus

Answer 15

the oesophagus is a tube that is about 23-25 cm long, has a double layer of muscle (circular muscle and longitudinal muscle) like the rest of the canal apart from the stomach (has a oblique muscle)

Question 16

peristalsis

Answer 16

The contraction of successive bands ofcircular muscle causes the constrictionto move in a wave-like motion called peristalsis, contractions and relaxations of the circular muscle move the bolus along canal

Question 17

stomach: mechanical digestion

Answer 17

• contains three types of muscle: circular (prevents food from travelling backwards), longitudinal (propels everything forward), oblique
• Mechanical digestion is achieved by waves of muscular contraction whichchurnthe food, mixing it withstomach juices until it is concerted to a thick, soupy liquid calledchyme.
• The lining of the stomach (mucosa) are flat and smooth when full, but as it empties the layers formconspicuous longitudinal wrinkles calledgastricrugae
• Cardiac sphincter and pyloric (gastroduodenal) sphincter – thick ring of smooth muscle -(to prevent acid from leaving the stomach and regulate chyme into the duodenum)

Question 18

gastric juice

Answer 18

stomach - chemical digestion
- The lining of the stomach, themucosa, is specialised for the secretionof gastric juice bygastric glands* located in narrow, tube-likestructures calledgastric pits
- Gastric juiceis a digestive juice containingHCl, mucus and digestiveenzymes(all secreted by different cells in the gastric pits)*
- Gastric juice is responsible for chemical digestion in the stomach,which is mainly the start of protein digestion

Question 19

what cells secrete components of gastric juice?

Answer 19

• parietal cells secrete HCl which kills bacteria and activates pepsinogen forming pepsin which breaks down proteins into polypeptides
• chief cells secrete pepsinogen
• goblet cells secrete mucus which protects inner layer from self digestion

Question 20

small intestine structure

Answer 20

6m, large surface area

Question 21

small intestine: mechanical digestion

Answer 21

from bile secreted from the liver (emulsification and segmentation which is where the muscles break the bolus and mix it with juices and bile)

Question 22

small intestine: chemical digestion

Answer 22

intestinal juice secreted by glands in the lining of the small intestine and pancreatic juices secreted from the pancreas into the duodenum

Question 23

pancreatic juices

Answer 23

• pancreatic amylase: breaks down carbohydrates into disaccharides
• typsin (pancreatic protease): breaks down polypeptides into peptides
• pancreatic lipases: breaks down lipids into fatty acids and glycerol

Question 24

intestinal juices

Answer 24

• amylases (maltase, lactase, sucrase): breaks down disaccharides (maltose, lactose, sucrose) into simple sugars
• peptidases: breaks down peptides into amino acids
• lipases: breaks down lipids into fatty acids and glycerol

Question 25

absorption of nutrients

Answer 25

nutrients are absorbed through the internal surface of the small intestine into the blood, effective absorption requires surface area

Question 26

duodenum

Answer 26

first part
- most of chemical digestion occurs here
- bile salts emulsifies fats (increasing surface area) (bile secreted from the liver into duodenum)

Question 27

jejunum

Answer 27

middle section
- allows for effective absorption of carbohydrates and proteins

Question 28

ileum

Answer 28

last part
- B12, bile salts and any remaining products of digestion and absorption

Question 29

villus

Answer 29

• 1mm, covered by a single cell, for small intestines inside is a lacteal (lymph capillary) surrounded by a network of capillaries, Glucose, amino acids, water and minerals are absorbed into the blood capillaries, Fatty acids and glycerol are absorbed into the lacteals (forming chyle)
• Small Intestine and Stomach have villi but small intestine has lacteals.

Question 30

functions of large intestine

Answer 30

• Further absorption of water and some salts
• Takes 18-24 hours to pass through → Semi-solid material calledfaeces→elimination

Question 31

pathway for food

Answer 31

mouth + salivary glands → pharynx → esophagus → stomach → small intestine (bile from liver/gallbladder) → large intestine → anus

Question 32

bile

Answer 32

• made in liver which aids in the digestion and absorption of fat
• stored in gall bladder and secreted into small intestine when needed

Question 33

bacterial activity in digestive system

Answer 33

there are trillions of resident bacteria in the large intestine. They are believed to have several important roles in addition to digesting cellulose in plant foods and synthesising some vitamins (e.g. folic acid)

Question 34

constipation

Answer 34

the movements of the large intestine are reduced and the contents remain there for a long period of time, the faeces become drier and harder than usual

Question 35

diarrhoea

Answer 35

the frequent defecation of watery faeces, irritation of small intestine or large intestine leads contents of the intestines move through before there is adequate absorption of water