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3 ADAPTATIONS FOR NUTRITION > THE HUMAN DIGESTIVE SYSTEM > Flashcards

THE HUMAN DIGESTIVE SYSTEM Flashcards

1
Q

why is food digested? (2)

A
  • insoluble/too big to cross membrane and be absorbed into blood
  • polymers must be broken into monomers to be rebuilt into useful molecules
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2
Q

gut (4)

A
  • where digestion occurs
  • long hollow muscular tube
  • movement in one direction by peristalsis
  • several sections of unique mechanical/chemical digestion and absorption
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3
Q

functions of the gut (4)

A
  • 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
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4
Q

types of digestion (2)

A
  • mechanical - chewing/crushing

- chemical - secreted enzymes

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5
Q

function of parts table 223

A

function half

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6
Q

structure of the gut wall (4)

A
  • 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
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7
Q

unlabelled gut

A

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

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8
Q

what must the gut wall do before absorption

A
  • break down macromolecules into smaller molecules
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9
Q

how are carbohydrates digested? (4)

A
  • digested from polysaccarides to disaccarides to monosaccarides
  • amylase hydrolyses starch into maltose
  • maltase digests maltose into glucose
  • sucrase digests sucrose, lactase digests lactose`
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10
Q

how are proteins digested? (4)

A
  • 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
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11
Q

how are fats digested?

A
  • into fatty acids and monoglycerides by lipase
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12
Q

buccal cavity (3)

A
  • where mechanical digestion begins (the mouth)
  • food is mixed with saliva and chewed by the teeth
  • increases foods surface area for enzymes to access
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13
Q

what is in saliva? (3)

A
  • amylase
  • HCO3- and CO3^2- so the pH is akaline for amylase
  • mucus to lubricate the food’s passage down the oesophagus
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14
Q

oesophagus

A
  • carries food from the mouth to the stomach
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15
Q

the stomach (3)

A
  • 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
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16
Q

what does gastric juice contain?

A
  • 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
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17
Q

how are peptidases secreted?

A
  • as inactive pepsinogen from the zymogen cells and activated by H+ to pepsin, an endopeptidase
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18
Q

gastric pit picture p225

A

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

19
Q

what are the regions of the small intenstine (2)

A
  • the duodenum

- the ileum

20
Q

how is partially-digested food allowed into the duodenum?

A
  • relaxation of pyloric sphincter muscle at the base of the stomach, allowing food through in small doses
21
Q

bile (3)

A
  • made in the liver
  • stored in the gallbladder
  • passed into the duodenum by the bile duct
22
Q

what is in bile? (3)

A
  • 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
Q

amphipathic

A
  • contain both hydrophilic and hydrophobic parts
24
Q

pancreatic juice (2)

A
  • secreted by islet cells (exocrine glands in the pancreas)

- enters duodenum through pancreatic duct

25
Q

what is in pancreatic juice?

A
  • enzymes

- sodium hydrogen carbonate

26
Q

enzymes in pancreatic juice? (4)

A
  • 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
Q

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

A
  • raises pH
  • neutralises acid from the stomach
  • providing pH for pancreatic enzymes
28
Q

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

A
  • lubricated by mucus

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

29
Q

enzymes associated with villi (3)

A
  • 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
Q

how is the ileum well-adapted (4)

A
  • very long with folded lining
  • villi on the surface of the folds
  • microvilli on the epithelial cells
  • all produce large SA for absorption
31
Q

how does absorption occur? (2)

A
  • by diffusion, facilitated diffusion and active transport

- epithelial cells have many mitochondria for ATP

32
Q

how are amino acids absorbed? (3)

A
  • absorbed into epithelial cells by active transport
  • pass into capillaries by facilitated diffusion
  • water-soluble and dissolve in plasma
33
Q

how is glucose absorbed? (4)

A
  • 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
Q

how are fatty acids / monoglycerides absorbed? (2)

A
  • 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
Q

how are minerals absorbed? (2)

A
  • into the blood by diffusion/facilitated diffusion/active transport
  • dissolve in plasma
36
Q

how are vitamins absorbed? (2)

A
  • B/C water soluble and absorbed into blood

- A,D,E fat soluble absorbed into lacteals

37
Q

how is water absorbed? (2)

A
  • absorbed into epithelial cells in ileum

- into capillaries via osmosis

38
Q

what happens to lipids after absorption (2)

A
  • used in membranes and to make hormones

- excess is stored

39
Q

where do glucose and amino acids go after absorption?

A
  • taken to the liver by the hepatic portal vein
40
Q

what happens to glucose in the liver? (2)

A
  • taken to body cells and respired for energy or stored as glycogen in liver/muscle cells
  • excess stored as fat
41
Q

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

A
  • 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
Q

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

A
  • the caecum
  • the appendix
  • the colon
  • the rectum
43
Q

what passes into the colon? (4)

A
  • undigested food
  • mucus
  • bacteria
  • dead cells
44
Q

how does the colon work? (6)

A
  • 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

3 ADAPTATIONS FOR NUTRITION (4 decks)

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