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Gastrointestinal System > Week 1 > Flashcards

Week 1 Flashcards

1
Q

are accessory organs hollow or solid?

A

solid

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2
Q

What are the four main functions of the digestive system?

A

digestion
absorption
secretion
motility

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3
Q

What is digestion?

A

the breakdown of the food we eat into simple substances that our bodies can absorb

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4
Q

What is digestive absorption?

A

The movement of the end-products of digestion from the GI tract into the blood, and lymphatic vessels.

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5
Q

what is motility?

A

the ability of an organism to move independently, using metabolic energy.

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6
Q

Function of stomach?

A

digestion of proteins
foodstuffs reduced to semi-liquid form
storage
sterilisation

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7
Q

Function of pancreas in digestion?

A

digestive enzyme production for digestion of fats, carbs and proteins

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8
Q

Function of liver in digestion?

A

production of bile salts for digestion/absorption of fats in small intestine

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9
Q

Function of gallbladder?

A

stores and concentrates bile

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10
Q

Function of small intestine?

A

Final stages of chemical digestion and nutrient absorption

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11
Q

function of large intestine/colon?

A

water absorption, bacterial fermentation and formation of faeces

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12
Q

How long is the alimentary canal?

A

8 metres long

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13
Q

does the tube wall have the same structural organisation throughout length?

A

yes

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14
Q

What are the four distinctive layers of the alimentary canal?

A
  • Mucosa: epithelium, lamina propria, muscularis mucosae
  • Submucosa
  • Muscularis externa
  • Serosa/adventitia
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15
Q

What is the peritoneum?

A

The serous membrane forming the lining of the abdominal cavity.

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16
Q

Where is stratified squamous epithelium present in the digestive tract?

A

mouth
esophagus
anus

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17
Q

Where is simple columnar epithelium present in the digestive tract?

A

stomach
intestines (with microvilli)

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18
Q

what is the submucosa composed
of?

A

dense irregular connective tissue with neurones, blood vessels and glands.
Meissner’s nerve plexus (parasympathetic)

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19
Q

what is the muscularis externa composed of?

A

an inner circular layer of smooth muscle.
a nerve plexus (Auerbach’s
an outer longitudinal smooth muscle layer.

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20
Q

what is the outer connective tissue layer called if its outside the peritoneal cavity?

A

adventitia

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21
Q

what is the connective tissue outer layer called if its inside the peritoneal cavity?

A

serosa

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22
Q

what is the function of the muscularis externa?

A

produce motility > peristalsis, segmentation

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23
Q

What ensures independent control of gut function in the muscularis externa?

A

submucosal and myenteric (Auerbach’s) plexuses = enteric nervous system

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24
Q

Describe parasympathetic control of alimentary function

A

via vagus nerve (except salivation > facial (VII) and glossopharyngeal (IX))
STIMULATORY
increased secretion and motility

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25
Q

describe the sympathetic control of alimentary function

A

via splanchnic nerve
inhibitory (except salivation)
decreased secretion and motility.

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26
Q

celiac trunk provides arterial supply to?

A

stomach
small intestine
pancreas
liver

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27
Q

superior mesenteric artery supplies blood to?

A

small intestine
caecum
ascending colon
transverse colon

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28
Q

inferior mesenteric artery supplies blood to?

A

descending colon
sigmoid colon
rectum

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29
Q

describe venous drainage from GI tract

A

gastric veins, splenic vein, superior mesenteric vein, inferior mesenteric vein

to

hepatic portal vein

to

hepatic vein

to

inferior vena cava

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30
Q

what are the principal dietary constituents ?

A

carbs
protein
fat
vitamins
minerals
water

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31
Q

describe monosaccharides and give examples

A

hexose sugars (6C) - glucose, galactose, fructose
breakdown products of complex carbohydrates which are absorbed by small intestine

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32
Q

describe disaccharides, their breakdown, and give examples

A
  • two monosaccharides linked together by glycosidic bond
  • broken down to constituent monomers by brush border enzymes (microvilli) in small intestine.
  • lactose, sucrose, maltose
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33
Q

give an example of a moderately branched polysaccharide

A

starch

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34
Q

give an example of a highly branched polysaccharide

A

glycogen

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35
Q

give an example of an unbranched polysaccharide

A

cellulose

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36
Q

give an example of a dietary fibre and describe its digestion

A

cellulose
no enzymatic digestion in vertebrates - require bacteria (cellulase).

37
Q

which bonds compose polysaccharides such as starch and glycogen

A

glucose monomers linked by alpha- 1,4 glycosidic bonds

38
Q

what enzyme breaks down starch and glycogen into disaccharides?

A

amylase

39
Q

what happens in lactose intolerance

A

An absence of lactase prevents the breakdown of lactose into glucose and galactose. This causes bacteria to ferment the lactose leading to acids and gas buildup which causes irritation. Water is also drawn to the lactose, causing diarrhea.

40
Q

glucose and sodium enters the cells of the small intestine via which transporter?

A

SGLT1

41
Q

glucose leaves the cells of the small intestine and enters the bloodstream via which transporter?

A

GLUT-2

42
Q

fructose enters the cells of the small intestine via which transporter?

A

GLUT-5

43
Q

Fructose leaves the cells of the small intestine > bloodstream via which transporter?

A

GLUT-2

44
Q

describe proteins

A

Polymers of amino acids linked together by peptide bonds.
Small proteins, 3-10 amino acids in length = peptides.

45
Q

which enzymes hydrolyse peptide bonds and reduce proteins or peptides to amino acids?

A

protease or peptidase

46
Q

amino acids and sodium enter the basolateral apical epithelium of the small intestine via which transporter?

A

SAAT1

47
Q

why does the transport of glucose into the cells of the small intestine require energy (via sodium potassium pump), but fructose doesnt?

A

glucose is already present in our cells, so it has to move against a concentration gradient. Fructose is not present in cells so it moves with the concentration gradient so it doesn’t require energy.

48
Q

almost all ingested fat is in the form of what?

A

triacylglycerol.

49
Q

where does fat digestion take place and by which enzyme?

A

small intestine by pancreatic lipase

50
Q

triacylglycerols present as?

A

large lipid droplets which are insoluble in water.

51
Q

describe the process of emulsification

A

dividing large lipid droplets into smaller droplets > increased surface area and accesibility to lipase action.

52
Q

what is triacylglycerol broken down into?

A

monoglyceride + 2 fatty acids

53
Q

describe the process of emulsification

A

dividing large lipid droplets into smaller droplets > increased surface area and accesibility to lipase action.

54
Q

what does emulsification require?

A

-mechanical disruption of large lipid droplets into small droplets > smooth muscle contraction.
- emulsifying agent.

55
Q

give an example of emulsifying agent and how it works.

A

e.g. bile salts and phospholipids secreted in bile.
Prevents small droplets reforming into large droplets.

56
Q

Despite emulsifiers, the absorption of lipase digestion products is still a very slow process. How can the absorption be enhanced?

A

By the formation of micelles.

57
Q

What is a micelle composed of?

A

Micelle = bile salt + monoglycerides + fatty acids + phospholipids.

58
Q

describe the core and outer layer of a fatty acid micelle

A

hydrophobic fatty acids & monoacylglycerols are in the interior core.
Bile salts are on the exterior.

59
Q

what is the diameter of a micelle?

A

4-7 um

60
Q

Describe micelle breakdown?

A

micelle breakdown > release of small amounts of free fatty acids (FFA) and monoglycerides into solution > diffusion across plasma membrane of absorbing cells.

61
Q

What happens to FA and monoglycerides after entering the epithelial cells? (previously part of micelle)

A

They enter the smooth endoplasmic reticulum (sER) where they are reformed into triacylglycerols (by enzymes located within the sER).

62
Q

What are extracellular fat droplets called? and how do they cross membranes

A

chylomicrons and they pass into lacteals between endothelial cells as they cannot pass through capillary basement membrane.

63
Q

What are the two classes of vitamins?

A

fat-soluble vitamins and water-soluble vitamins.

64
Q

give examples of fat-soluble vitamins

a dinny even ken

A

vitamins A, D, E, K

65
Q

give examples of water soluble vitamins

A

B, C and folic acid

66
Q

how are fat-soluble vitamins absorbed?

A

follow same absorptive path as fat

67
Q

how are water-soluble vitamins absorbed?

A

either absorbed by passive diffusion or carrier-mediated transport

68
Q

Describe vitamin B12 and its absorption.

A

Vitamin B12 is a large charged water-soluble vitamin. It binds to intrinsic factor in stomach to form complex which is absorbed via specific transport mechanism in distal ileum of small intestine.

69
Q

What causes pernicious anaemia?

A

B12 deficiency > failure of red blood cell maturation.

70
Q

Describe the transport of ingested iron and what happens after?

A

Iron transported across brush border membrane via transporter DMT1 into duodenal enterocytes.
Iron ions incorporated into ferritin.
Some iron remains unbound.

71
Q

what is ferritin?

A

protein-iron complex > intracellular ion store.

72
Q

what happens to unbound iron?

A

Transported across serosal membrane > bloodstream.
iron in blood binds to transferrin.

73
Q

what happens in anaemia? related to ferritin

A

decreased ferritin levels > more iron released to blood.

74
Q

what are the components of saliva?

A

water
mucins
alpha-amylase
electrolytes
lysozome

75
Q

what is the function of mucins in saliva?

A

major glycoprotein component
mucins + water = mucus
viscous solution so has a lubricant function

76
Q

what is the function of alpha-amylase?

A

catalyses breakdown of polysaccharides such as starch into simpler sugars > maltose + glucose

77
Q

what is the function of lysozome in saliva?

A

bacteriocidal - cleaves polysaccharide component of bacterial cell wall.

78
Q

describe the parasympathetic control of salivary secretion.

A
  • cranial nerves VII (facial) & IX (glossopharyngeal)
  • stimulation > profuse watery salivary secretion.
79
Q

describe the sympathetic control of salivary secretion.

A

stimulation > small volume, viscous salivary secretion
high mucus content (alpha 1 adrenoceptors)
high amylase content (b2 adrenoceptors)

80
Q

describe the reflex control of salivary secretion

A

presence of food in mouth > chemoreceptors/pressure receptors (walls of mouth/tongue).

81
Q

Describe the process of swallowing

A

oral phase volunatry:
- bolus pushed to back of mouth by tongue.

pharyngeal phase:
- presence of bolus > sequence of reflex contractions of pharyngeal muscles.
- coordinated by swallowing centre (medulla).
- soft palate reflected backward and upward (closes off nasopharynx)

as bolus approaches oesophagus:
- upper oesophageal sphincter (UOS) relaxes and epiglottis covers opening to larynx.

once food has entered oesophagus:
- UOS contracts (prevents food reflux)

82
Q

where are bile salts reabsorbed from?

A

Bile salts are reabsorbed in the distal ileum and recycled to the liver via the hepatic portal vein. This means that only 0.5g of the total 5g bile salt pool need to be synthesised each day.

83
Q

what initates segmentation contractions in the small intestine?

A

the arrival of food in the stomach

84
Q

what do Brunner’s glands of the small intestine do?

A

They secrete bicarbonate rich fluid which acts to help neutralise gastric acid.
Stimulated by secretin.

85
Q

where is intrinsic factor/vitamin B12 absorbed?

A

Intrinsic factor/Vitamin B12 complex is absorbed in the terminal ileum

86
Q

Proteins are broken down into amino acids which are absorbed coupled to which ion for transport?

A

Na+

87
Q

what is the difference between segmental contractions and peristalsis?

A

Peristalsis and segmentation are fundamentally different from one another since segmentation refers to the rhythmic contractions of the circular muscles in the digestive system. In contrast, peristalsis refers to the contractile activity of the longitudinal muscles in the gastrointestinal tract.

88
Q

how is vitamin K produced?

A

via colonic bacteria

Gastrointestinal System (16 decks)

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