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MW1012 Anatomy and Physiology > GI Tract > Flashcards

GI Tract Flashcards

1
Q

What is the purpose of the gut?

A

Break down food, absorb the food through the gut wall into blood/lymph so that energy/nutrients can be used, get rid of waste, absorb water, excrete cholesterol, synthesise vitamins

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2
Q

What does GI stand for?

A

Gastro-intestinal system

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3
Q

What makes up the GI tract?

A

Mouth, oesophagus,stomach, pancreas, small intestine, large intestine, salivary glands, liver (gall bladder), anus

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4
Q

What are the features of the peritoneum?

A

Serous Membrane sac in abdomen, the two layers (parietal and visceral) have serous fluid between them

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5
Q

What is the basic function of the peritoneum?

A

Structure, holds organ, contain developing infections to stop them,

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6
Q

Describe the structure of the GI tract

A

adventitia/peritoneum, longitudinal smooth muscle layer, circular smooth muscle layer, myenteric plexus on circular muscle, submucosa, submucosal plexus on submucosa, mucosa (lumen), epithelium (mucuos membrane)

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7
Q

define plexus

A

network of nerves

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8
Q

describe the function of the peritoneum

A

covers the abdominal organs to provide structure and hold them in place, contain any developing infections to stop the spread, reduces friction so prevents inflammation

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9
Q

how does the peritoneum reduce friction?

A

between the two layers (parietal and visceral) there is serous fluid and that makes them slippery so it stops inflammation

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10
Q

describe the motility of the gut

A

contraction of the muscle layers, peristalsis, segmentation and mass movements

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11
Q

describe peristalsis

A

food moving forward by rhythmic squeezes of muscles, its required for movement

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12
Q

describe segmentation

A

squeezing the churned food and breaking it down so they can absorb the nutrients

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13
Q

describe the broad functions of the mouth

A

mastication (chewing) - physically breaking down the food by tongue and teeth
hard palate made of bone
soft palate made of muscle
initial digestive enzymes released
infection control

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14
Q

describe the broad functions of the pharynx

A

3 sections naso-(nose), oro-(near throat), laryngo-(near oesophagus)
food travels from oral cavity to oesophagus via pharynx

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15
Q

describe the broad function of the oesophagus

A

fast transport of bolus to stomach through thorax

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16
Q

describe the broad function of sphincters

A

upper oesophagul/ pyloric and lower oesophagul/ cardiac , thickened rings of circular muscle, keep GI tract a one way system to prevent backflow.
Upper- stops food being aspirated and upper - stops stomach acid rising up oesophagus

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17
Q

describe the broad structure of the tongue

A

voluntary muscle covered by mucous membrane, stuck to the floor by the frenulum, covered in papillae which contain taste buds

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18
Q

describe the broad function of the tongue

A

needed for deglutition

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19
Q

what is the word for swallowing

A

deglutition

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20
Q

describe the slalivary glands

A

3 main pairs, parotid, submandibular, sub-lingual, saliva contains enzymes

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21
Q

describe the broad function of saliva

A

secrete digestive enzymes (e.g. amylase) to break down complex sugars, oral hygiene: prevent tooth decay, antimicrobial antibodies to prevent infections, lubricate food bolus

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22
Q

describe the broad functions of the stomach

A

produces chyme(bolus + gastric acid), physical breakdown, chemical breakdown, digestion starts, storage

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23
Q

describe how the structure of the stomach aids its function

A

3 muscle layers to help churn food into chyme, mucous membrane thrown into rugae (folds) allowing it to stretch when full
gastric glands release the ingredients of gastric juice

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24
Q

describe the function of gastric juice

A

breaks down proteins, activates enzymes, e.g. pepsinogen to pepsin, disinfects stomach contents

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25
Q

describe chyme (kime)

A

partially digested, acidic (Hydrochloric), very concentrated

26
Q

describe the broad function of the duodenum

A

acidic chyme neutralised, water enters through gut walls which dilutes chyme, digestive enzymes enter

27
Q

describe how the structure of the duodenum aids its fucntion

A

c-shaped to curve around the pancreas, pancreas and liver join gut tube here, start of small intestine

28
Q

describe the broad function of the liver

A

hepatocytes, produces bile, synthesises proteins like albumin/clotting factors, detoxifies blood, energy storage (glycogen)

29
Q

describe the broad functions of the gall bladder

A

stores and concentrates bile, contracts when fat is detected in the duodenum and releases bile into the duodenum, connected to liver above and duodenum, below

30
Q

describe the broad functions of bile

A

contains bile salts, contains bilirubin

31
Q

describe the function of bile salts

A

helps emulsify fats into smaller droplets
makes it possible to absorb cholesterol and fatty acids and fat-soluble vitamins

32
Q

describe the broad function of bilirubin

A

bilirubin is released when red blood cells die, needs to be excreted out of the body or it can lead to jaundice, it gives stool their colour

33
Q

describe the broad function of the pancreas

A

endocrine function: secretes insulin/glucagon directly into the bloodstream
exocrine function: secretes pancreatic juice into ducts/tubes, it contains active enzymes for digestion (amylase/lipase) and inactive enzymes (trypsinogen activates on arrival)

34
Q

describe the broad function of the jejunum and ileum

A

duodenum, jejunum, ileum
secretes alkaline intestinal juice (neutralises gastric juice), final digestion, nutrient absorption (jejunum mainly), water/electrolyte absorption (ileum mainly)

35
Q

describe how the structure of the small intestine aids its function

A

small circular folds which are the folding of the gut called plicae, has villi, enterocytes have microvilli in order to increase the surface area of the mucous membrane

36
Q

how do villi aid with the function of the small intestine

A

1 mm long projections, covered by enterocytes which are cells which complete the chemical digestion of proteins, carbs and fats as they contain digestive enzymes, e.g. sucrase, lipase, maltase, peptidase, lactase

37
Q

describe the broad functions of the large intestines

A

made up of the caecum, colon (ascending, descending, transverse, sigmoid), rectum, anal canal
final water and electrolyte absorption, temporary storage, secretes mucus to lubricate food waste moving along

38
Q

describe the broad function of the caecum

A

where small intestine joins large intestine, wide pouch that acts as a reservoir. once full food moves along the large intestine

39
Q

describe the broad function of the rectum/anus

A

defaecation, waits for a build up of stool, the stretch alerts us to the need to defaecate, then mass movement occurs

40
Q

describe gut microbiota/microbiome

A

bacteria/fungi/viruses living in our gut
produce some vitamins, prevent bad bacteria from causing disease from reproducing

41
Q

how does gut microbiota/microbiome relate to infants

A

infants intestines are kind of sterile but quickly gain bacteria as they pass through the mother’s birth canal and brush up against the anus being covered in their mum’s faecal matter and gain the good bacteria
c-section babies have reduced gut bacteria initially

42
Q

define egestion

A

voiding undigested material as faeces

43
Q

how does the colon work in egestion

A

unabsorbed materials pass through the colon which absorbs most of the remaining fluid from the material producing semi-solid faeces
temporarily stores faeces and then 1-2 times/day its moved into the rectum.

44
Q

how does the anus work in egestion

A

has two sphincters, internal and external
internal is involuntary, faeces is allowed through it to pass from rectum to anus, an urge to defecate arises
external is voluntary, so controlled over time

45
Q

describe how carbohydrates are digested from mouth to small intestine

A

starts in mouth and oesophagus via salivary amylase broken down starch into disaccharides
HCl denatures and inhibits salivary amylase, pancreatic amylase breaks down digestable starches into disaccharides and then lactase, maltase and sucrase
in enterocytes break them down from disaccharides to monosaccharides

46
Q

describe carbohydrates

A

long chains of sugars (starch) in rice, potatoes, etc
shorter chains of sugars like lactose in milk

47
Q

describe how proteins are digested

A

stomach HCl activates pepsinogen into pepsin. pepsin: from protein to polypeptides
in small intestine: enterkinase in enterocytes activates chymotrypsinogen and trypsinogen from pancreas into chymotrypsin and trypsin
they break down polypeptides to di- and tri-peptides
peptidases in enterocytes break them down into amino acids

48
Q

describe proteins

A

long chain of amino acids (polypeptides)
for growth and rep

49
Q

how do we stop the enzymes digesting the gut?

A

proteases are stored as inactive form and activate only in a safe environment
activated by gastric juice(HCl) in the stomach: pepsiongen to pepsin
chymotrypsinogen and trypsinogen from pancreas activated to chymotrypsin and trypsin by enterokinase in enterocytes

50
Q

describe how fat is digested

A

fat globules are emulsified by bile salts in bile
broken down further by pancreatic lipases into fatty acids and glycerol also by lipases in enterocytes

51
Q

what happens to bile salts and fatty acids after fats have been digested?

A

the bile salts and the fatty acids form micelles which can be absorbed by the villi of the small intestine

52
Q

describe the role of bile in digestion

A

breaks up fat into smaller droplets called emulsion

53
Q

describe the role of lipase in digestion

A

further break down the fat globules into smaller units called fatty acids and glycerol

54
Q

where does absorption occur?

A

the small intestine, specifically enterocytes from lumen to blood/lymph

55
Q

give examples of absorption

A

sugar and amino acids absorbed into blood capillaries of villi then travel to liver
fats absorbed into lacteals of villi then lymph vessels then travel to venous blood

56
Q

describe the portal venous system

A

liver accepts blood drained from the GI tract (venous blood)
then goes to heart
so liver receives both venous and arterial blood which mixes

57
Q

how does the central nervous system controls the gut?

A

autonomic nervous system (unconscious control)
parasympathetic enables
sympathetic inhibits

58
Q

how does the endocrine system control the gut?

A

hormones
e.g. gastrin increases gastric acid secretion
secretin increases the releases of bicarbonate to neutralise the acid

59
Q

describe the metabolism of carbohydrates

A

glucose used by liver or stored as glycagon
glucose used in aerobic respiration by all cells
stored as glycogen by muscles
stored as fat by fat depots

60
Q

outline the role of insulin and glucagon in the metabolism of carbs

A

high BGL: insulin secreted, stimulates uptake of glucose by cells, glycogenesis (formation of glycogen), glycolysis (breakdown of glucose into pyruvate)
low BGL: glucagon secreted, stimulates glycogenolysis (breakdown of glycogen into glucose), gluconeogenesis (formation of new glucose from non-carbs e.g. amino acids, glycerol)

61
Q

describe the metabolism of fats

A

liver turns fatty acids and glycerol into triglycerides
tissue cells use fatty acids and glycerol in aerobic respiration to form ATP and heat
adipose tissue cells store excess triglycerides, release fatty acids and glycerol when required

62
Q

describe the metabolism of proteins

A

amino acids pass to tissues, e.g. muscle, skin, mucous membrane
carried to liver for deamination or transamination
excreted by kidneys as urea
or provides energy and transamination (new non-essential amino acids

MW1012 Anatomy and Physiology (25 decks)

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