digestive system

Question 1

what is the digestive system made up of

Answer 1

alimentary canal
pancreas
liver

Question 2

what is the alimentary canal

Answer 2

long tube which runs from the mouth to the anus

Question 3

how are the liver and pancreas connected to the alimentary canal at the small intestine

Answer 3

via ducts

Question 4

list order of organs in the digestive system

Answer 4

mouth
oesphagus
stomach
small intestine
large intestine
rectum
anus

Question 5

define digestion

Answer 5

process by which food is broken down from large insoluble complex substances into small soluble simple substances so that they can be absorbed into the food

Question 6

list and define the two types of digestion

Answer 6

mechanical or physical digestion – involves break down of food into smaller pieces without changing the chemical structure of the food
chemical digestion – involves break down of food with the aid of special proteins called enzymes
chemical structure of the food is altered

Question 7

what do the teeth do

Answer 7

in the mouth they bite and chew food breaking it up into smaller pieces
form of mechanical digestion

Question 8

what do the salivary glands do

Answer 8

produce saliva which mixes with food moistening it making it easier to swallow
saliva has a neutral to slightly acidic pH 6,2 to 7.6
saliva contains water and mucus
saliva also contains salivary amylase enzyme which speeds up the breakdown of starch a polysaccharide into maltose a disaccharide
this is chemical digestion

Question 9

what does the tongue do

Answer 9

rolls up the food into a ball called the bolus and pushes it to the back of the throat towards the oesophagus

Question 10

what is the oesophagus

Answer 10

narrow tube with strong muscular walls
rings of muscles alternate contracting and relaxing pushing food downward into the stomach

Question 11

define peristalsis

Answer 11

wave like motion which pushes food along

Question 12

what is the stomach

Answer 12

muscular sac which temporarily stores food before it moves on to the small intestine

Question 13

list a characteristic of the stomach

Answer 13

its walls are slightly elastic allowing the stomach to stretch to accommodate large amounts of food while being able to revert to its original size

Question 14

how does the stomach have mechanical digestion

Answer 14

contracts churning up the food breaking it up further

Question 15

what do the stomach walls secrete

Answer 15

gastric juice which contains hydrochloric acid mucus and pepsin enzyme

Question 16

what is the acids role in the stomach

Answer 16

kills any harmful bacteria present in the food and also provides an acidic environment around pH 2 for pepsin enzyme to work well

Question 17

what is the pepsin enzyme role in the stomach

Answer 17

speeds up the breakdown of proteins into shorter polypeptide chains called polypeptides or peptides

Question 18

what is the enzyme present in infants

Answer 18

rennin which coagulates milk breaking down milk protein

Question 19

what is gastric juice role in the stomach

Answer 19

as the stomach churns the food mixed with the gastric juice it becomes a semi liquid called chyme
which is released in small amounts at a time into the small intestine

Question 20

what are the parts of the small intestine called

Answer 20

first part is duodenum
last part is ileum

Question 21

what happens to chyme when it enters the duodenum

Answer 21

mixed with alkaline fluids to neutralise the acid from the stomach
the enzymes in the small intestine work best in an alkaline environment
pH starts at 6 and gets progressively more alkaline along the small intestine

Question 22

what does the liver do

Answer 22

produces a substance called bile which is stored in the gall bladder and is released into the duodenum via bile duct
bile mixes with the fats and lipids present in food causing them to be broken up into smaller fat globules
process is called emulsification and is mechanical digestion

Question 23

what does the pancreas do

Answer 23

produces pancreatic juice pH 8.3 to 8.6 which makes it way to the duodenum via the pancreatic duct the alkaline pancreatic juice contains several enzymes which aid with chemical digestion

Question 24

list the enzymes and what they break down present in pancreatic juice

Answer 24

trypsin breaks down protein into polypeptides
pancreatic amylase breaks down starch into maltose
lipase breaks down lipids or fats into fatty acids and glycerol

Question 25

what is secreted by the walls of the small intestine

Answer 25

intestinal juice pH 7.5 to 8.5 and also mixes with food alkaline fluid which contains the enzyme maltase which breaks down maltose into glucose peptidases (group of enzymes) which break down polypeptides into amino acids sucrase which breaks down sucrose into glucose and fructose lactase breaks down lactose into glucose and galactose chemical digestion

Question 26

how does food move along the intestines

Answer 26

peristalsis contraction of intestinal walls during peristalsis further helps which mechanical digestion

Question 27

what happens once food reaches the ileum

Answer 27

digestion is complete

Question 28

what happens to the digested food in the ileum

Answer 28

it is absorbed glucose amino acids fatty acids glycerol

Question 29

how is the ileum specially adapted for absorption on the small products of digestion

Answer 29

has a large surface area thin walls rich blood supply lacteals

Question 30

what is the ileum

Answer 30

longest part of the small intestine with a length of about 3.5 m

Question 31

what do the ileum walls have

Answer 31

special finger like projection called villi which help to increase the surface area for absorption making it more efficient villi also have microvilli which further increase SA for absorption

Question 32

how thin are the ileum walls

Answer 32

one single layer of epithelial cells allows for rapid diffusion of digested substances across villi into blood vessels and lacteals

Question 33

what does the dense network of capillaries do

Answer 33

where nutrients absorbed

Question 34

what do each villus have

Answer 34

lacteal located at its centre which absorbs lipids and drains into the lymphatic system

Question 35

what do goblet cells in the epithelium of villi produce

Answer 35

mucin which forms a mucus layer which helps with lubrication to protect against physical injury to ileum and to trap bacteria acting as a physical barrier

Question 36

what occurs in the large intestine

Answer 36

any undigested food passes into the large intestine where water is reabsorbed from the food across intestinal walls back to the body

Question 37

what is the large intestine also known as

Answer 37

colon

Question 38

what happens when the water is removed from the undigested food in the large intestine

Answer 38

undigested food becomes more solid and is called faeces s

Question 39

where are faeces stored

Answer 39

in last part of the large intestine called rectum until it is passed out of the body through the anus

Question 40

define egestion

Answer 40

removal of undigested food from the body through the anus

Question 41

define assimilation

Answer 41

process of incorporating and making use of digested food into the body

Question 42

what is the fate of monosaccharides

Answer 42

such as glucose is utilised by cells in respiration to produce energy in the form of ATP if there is excess it can be converted into glycogen and stored short term in the liver and muscle cells further excess monosaccharides converted into fat and stored in fat cells which form adipose tissue which is stored around organs and below skin

Question 43

what is the fate of amino acids

Answer 43

amino acids are taken from the ileum to the liver via the hepatic portal vein they are absorbed by cells and reassembled to make proteins which are used for growth in cell membranes and other living parts of cells used to make hormones and enzymes excess amino acids are never stored but can be converted into glycogen or fat to be stored excess amino acids are also broken down in the liver in a process called deanimation which produces urea urea is then transported to the kidneys to be excreted in urine

Question 44

what is the fate of fatty acids and glycerol

Answer 44

used in cell membranes and cell organelles used in respiration to produce energy in the form of ATP excess is stored in fat cells and adipose tissue below skin and around organs unlike glycogen there is no limit to how much fat can be stored in the body