THE HUMAN DIGESTIVE SYSTEM Flashcards Preview

3 ADAPTATIONS FOR NUTRITION > THE HUMAN DIGESTIVE SYSTEM > Flashcards

Flashcards in THE HUMAN DIGESTIVE SYSTEM Deck (44):
1

why is food digested? (2)

- insoluble/too big to cross membrane and be absorbed into blood
- polymers must be broken into monomers to be rebuilt into useful molecules

2

gut (4)

- where digestion occurs
- long hollow muscular tube
- movement in one direction by peristalsis
- several sections of unique mechanical/chemical digestion and absorption

3

functions of the gut (4)

- ingestion, taking food in
- digestion, break down of molecules by mechanical/chemical digestion
- absorption, passage of useful molecules into gut wall into blood
- egestion - elimination of waste not made by the body

4

types of digestion (2)

- mechanical - chewing/crushing
- chemical - secreted enzymes

5

function of parts table 223

function half

6

structure of the gut wall (4)

- serosa - tough connective tissue, reduces friction
- muscle - two layers (circular/longitudinal), make waves of contractions (peristalsis) to push food along
- submucosa - connective tissue w/ blood/lymph vessels, remove ab

7

unlabelled gut

label lumen, serosa, longitudinal muscle, circular muscle, epithelium,

8

what must the gut wall do before absorption

- break down macromolecules into smaller molecules

9

how are carbohydrates digested? (4)

- digested from polysaccarides to disaccarides to monosaccarides
- amylase hydrolyses starch into maltose
- maltase digests maltose into glucose
- sucrase digests sucrose, lactase digests lactose`

10

how are proteins digested? (4)

- they are very large molecules so digested into polypeptides, into dipeptides, into amino acid
- protein digesting enzymes = protease, peptidase
- endopeptidases hydrolyse peptide bonds in the protein
- exopeptidases hydrolyse peptide bonds at the end of the polypeptides

11

how are fats digested?

- into fatty acids and monoglycerides by lipase

12

buccal cavity (3)

- where mechanical digestion begins (the mouth)
- food is mixed with saliva and chewed by the teeth
- increases foods surface area for enzymes to access

13

what is in saliva? (3)

- amylase
- HCO3- and CO3^2- so the pH is akaline for amylase
- mucus to lubricate the food's passage down the oesophagus

14

oesophagus

- carries food from the mouth to the stomach

15

the stomach (3)

- food is digested in the stomach
- kept there by contraction of two sphincters/rings of muscle
- stomach wall muscles contract rhythmically and mix food with gastric juice secreted by the glands in the wall

16

what does gastric juice contain?

- peptidases, secreted by zymogen/chief cells at the base of the gastric pit
- hydrochloric acid, secreted by oxyntic cells to lower the pH for enzymes
- mucus, secreted by goblet cells, at the top of the gastric pit, forms a lining to protect the stomach wall from enzymes and lubricate food

17

how are peptidases secreted?

- as inactive pepsinogen from the zymogen cells and activated by H+ to pepsin, an endopeptidase

18

gastric pit picture p225

labels: gastric pit, goblet cells, submucosa, immature goblet cells, zymogen cells, oxyntic cells

19

what are the regions of the small intenstine (2)

- the duodenum
- the ileum

20

how is partially-digested food allowed into the duodenum?

- relaxation of pyloric sphincter muscle at the base of the stomach, allowing food through in small doses

21

bile (3)

- made in the liver
- stored in the gallbladder
- passed into the duodenum by the bile duct

22

what is in bile? (3)

- no enzymes
- amphipathic bile salts, emulsify lipids in food by lowering surface tension and increasing surface area by breaking globules into smaller globules
- is alkaline and neutralises acid from stomach, makes pH suitable for small intestine

23

amphipathic

- contain both hydrophilic and hydrophobic parts

24

pancreatic juice (2)

- secreted by islet cells (exocrine glands in the pancreas)
- enters duodenum through pancreatic duct

25

what is in pancreatic juice?

- enzymes
- sodium hydrogen carbonate

26

enzymes in pancreatic juice? (4)

- endopeptidases, to hydrolyse protein to peptides
- amylase, to digest any remaining starch to maltose
- lipase, lipids to fatty acids and monoglycerides
- trypsinogen, inactive enzyme converted into protease trypsin by enterokinase (duodenal enzyme)

27

purpose of sodium hydrogen carbonate in pancreatic juice? (3)

- raises pH
- neutralises acid from the stomach
- providing pH for pancreatic enzymes

28

what happens to food coming from the stomach? (2)

- lubricated by mucus
- neutralised by alkaline secretions from cells at the base of the crypts of Lieberkühn, called Brunner's glands

29

enzymes associated with villi (3)

- endo/exopeptidases secreted by cells at villus tips to digest polypeptides
- enzymes on epithelial cell membranes that digest dipeptides into amino acids
- carbohydrases digest disaccarides and they are absorbed into epithelial cells of the villi

30

how is the ileum well-adapted (4)

- very long with folded lining
- villi on the surface of the folds
- microvilli on the epithelial cells
- all produce large SA for absorption

31

how does absorption occur? (2)

-by diffusion, facilitated diffusion and active transport
- epithelial cells have many mitochondria for ATP

32

how are amino acids absorbed? (3)

- absorbed into epithelial cells by active transport
- pass into capillaries by facilitated diffusion
- water-soluble and dissolve in plasma

33

how is glucose absorbed? (4)

- passes into epithelial cells w/ glucose by co-transport
- move into capillaries, sodium by active transport, glucose by facilitated diffusion
- dissolve in plasma
- diffusion/facilitated diffusion are slow so active transport is used for some to prevent it being lost in faeces

34

how are fatty acids / monoglycerides absorbed? (2)

- diffuse into epithelial cells into lacteals, ending lymph capilaries in villi
- lacteals transport fat-soluble molecules through lymphatic system to left subclavian vein near heart

35

how are minerals absorbed? (2)

- into the blood by diffusion/facilitated diffusion/active transport
- dissolve in plasma

36

how are vitamins absorbed? (2)

- B/C water soluble and absorbed into blood
- A,D,E fat soluble absorbed into lacteals

37

how is water absorbed? (2)

- absorbed into epithelial cells in ileum
- into capillaries via osmosis

38

what happens to lipids after absorption (2)

- used in membranes and to make hormones
- excess is stored

39

where do glucose and amino acids go after absorption?

- taken to the liver by the hepatic portal vein

40

what happens to glucose in the liver? (2)

- taken to body cells and respired for energy or stored as glycogen in liver/muscle cells
- excess stored as fat

41

what happens to amino acids in the liver? (3)

- taken to body cells for protein synthesis
- excess not stored so liver deanimates and converts amine groups to urea and carried in blood, excreted at kidney
- remains of amino acid conversed into carbohydrate for storage or conversion to fat

42

what is the large intestine made up of? (4)

- the caecum
- the appendix
- the colon
- the rectum

43

what passes into the colon? (4)

- undigested food
- mucus
- bacteria
- dead cells

44

how does the colon work? (6)

- less villi with a major role in water absorption
- vitamin K and folic acid secreted by mutualistic microorganisms living there
- minerals absorbed from colon
- as material passes along, water absorbed
- reaches the rectum semi-solid
- passes along rectum and egested as faeces in defecation