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Physiology 1B > GI System > Flashcards

GI System Flashcards

1
Q

What is digestion?

A

The process by which foodstuffs are are degraded to produce smaller molecules which can be absorbed

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2
Q

What is absorption?

A

The processes by which nutrient molecules are absorbed by cells that line the GI tract and enter the bloodstream

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3
Q

Where can you find a myenteric plexus?

A

Through the whole length of the GI tract

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4
Q

Where can you find a submucosal plexus?

A

Only in the small and large intestine

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5
Q

Which layers make up the mucosa?

A

Epithelium, lamina propria, muscularis mucosae

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6
Q

What composes the muscularis externa?

A

An internal layer of circular muscle and an external layer of longitudinal muscle

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7
Q

What is the glycocalyx?

A

The network of proteins on the microvilli

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8
Q

What are the 2 routes of cellular transport in the small intestine?

A

Paracellular and transcellular

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9
Q

Which hormones are produced in the stomach/by which cells?

A

Gastrin (G cells) and somatostatin (D cells)

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10
Q

Which hormones are produced in the small intestine/by which cells?

A

Cholecystokinin (I cells), GIP (K cells), secretin (S cells), somatostatin (D cells)

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11
Q

The GI system is contained under which part of the nervous system?

A

Enteric

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12
Q

What happens to the membrane potential during GI smooth muscle contraction?

A

It oscillates between -40 mV and -60 mV in slow waves - frequency of slow waves determines frequency of muscle contraction

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13
Q

What type of contraction do sphincters have?

A

Long-lasting tonic contractions

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14
Q

What sphincters are in the GI tract?

A

Upper and lower oesophageal, pyloric, ileocaecal, internal and external anal

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15
Q

Where is the sphincter of Oddi?

A

Wraps around the ducts coming from the liver and gallbladder to the duodenum

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16
Q

Where do contractions begin in the stomach?

A

Corpus (body of stomach)

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17
Q

Where does mixing/grinding begin in the stomach?

A

Antrum (just before pylorus)

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18
Q

What is the most common type of movement in the small intestine?

A

Non-propulsive movements (caused by rhythmic contraction and relaxation of muscularis externa)

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19
Q

What is the name given to the process of moving GI contents towards the rectum/anus?

A

Segmentation

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20
Q

Which nerves control defection/the rectosphincteric reflex?

A

Somatic = pudendal nerve, parasympathetic = pelvic nerves

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21
Q

What important components are in saliva?

A

Mucin glycoproteins, lysozyme, a-amylase

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22
Q

What is the function of lysozyme in saliva?

A

Clean and protect cavity of the mouth

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23
Q

What is the function of a-amylase in saliva?

A

Reduce starch into oligosaccharides

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24
Q

What type of saliva does the parotid gland secrete?

A

Serous secretion, rich in a-amylase

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25
Q

What type of saliva do the submandibular and sublingual gland secrete?

A

Seromucous secretion

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26
Q

What type of saliva do the minor salivary glands secrete?

A

Mucous secretion, rich in mucin glycoproteins

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27
Q

What effect does acetylcholine have on the acinar and duct cells?

A

Stimulates fluid/protein secretion in the acinar cells, decreases absorption in the duct cells

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28
Q

What effect does noradrenaline have on the acinar and duct cells?

A

Stimulates protein secretion in the acinar cells, stimulates bicarbonate secretion in the duct cells

29
Q

Is there any hormonal control of salivary gland secretion?

A

No!

30
Q

Which branch of the autonomic nervous system stimulates saliva secretion?

A

Both sympathetic and parasympathetic branches

31
Q

Where is B12 absorbed in the GI tract?

A

Stomach

32
Q

What is the pH of gastric secretions?

A

0.9-1.5

33
Q

What are the 5 main components of gastric secretions?

A

HCl, pepsins, intrinsic factor, mucus and bicarbonate ions

34
Q

Which cell type secretes bicarbonate ions into the stomach?

A

Surface epithelial cells

35
Q

What do the mucous neck cells of the stomach secrete?

A

A protective mucus

36
Q

What do the parietal cells of the stomach secrete?

A

HCl and intrinsic factor

37
Q

Which cell type secretes pepsinogens into the stomach?

A

Chief cells

38
Q

Where are the G cells (gastrin-producing) in the stomach?

A

Antrum region

39
Q

What is the secondary role of pepsin in the stomach?

A

Stimulate production of HCl

40
Q

How is bicarbonate and mucus release regulated in the stomach?

A

Via acetylcholine and prostaglandins

41
Q

What provides anatomical protection for the apical cells of the stomach?

A

Impermeability to H+ and the presence of tight junctions

42
Q

What provides physiological protection for the apical cells of the stomach?

A

Thick layer of mucus impregnated with bicarbonate ions (mucus gel neutralisation zone)

43
Q

Which agonist is involved in neuronal control of HCl secretion?

A

Acetylcholine and stimulation of ECL cells (indirect)

44
Q

Which agonist is involved in hormonal control of HCl secretion?

A

Gastrin (secretion by G cells) stimulation of ECL cells (indirect)

45
Q

Which agonist is involved in paracrine control of HCl secretion?

A

Histamine from ECL cell to activate cAMP within cell

46
Q

Which nerve controls the cephalic phase of secretion?

A

Vagal nerve (entirely dependent)

47
Q

What pH are pancreatic secretions?

A

7.8-8.4

48
Q

Which type of digestive enzymes are released in an inactive form?

A

Proteases (trypsin, chymotrypsin, carboxypeptidases)

49
Q

Where is cholecystokinin released from?

A

I cells in the small intestine

50
Q

What is the effect of parasympathetic/enteric Ach release on pancreatic acinar cells?

A

Stimulation of enzyme release

51
Q

How is NaCl secretion by the pancreatic acinar cells regulated?

A

Ach (neuronal) and CCK both increase intracellular calcium concentration

52
Q

What is the most powerful stimulus for bicarbonate secretion from the pancreas?

A

Secretin

53
Q

Which enzyme converts trypsinogen into trypsin?

A

Enteropeptidase

54
Q

What is produced in the hepatocytes and stored in the gallbladder?

A

Bile salts, cholesterol, phospholipids - all together form a mixed micelle

55
Q

What happens to bile acids once they have been utilised?

A

Absorbed by ileum then returned to the liver where they are taken up by hepatocytes (sodium-driven process)

56
Q

What are the main 3 differences between the small and large intestines?

A

Large intestine does not have villi and is not involved in nutrient reabsorption; large intestine actively secrets K+ but small does not

57
Q

What is the maximal absorptive capacity of the small intestine?

A

15-20L per day!!!

58
Q

Which type of small intestine cell secretes salts?

A

Crypt-lining epithelial cells

59
Q

Which type of small intestine cell absorbs salt/glucose?

A

Villus-lining epithelial cells

60
Q

How is starch broken down in the small intestine?

A

Broken down by a-amylase into maltose, maltotriose and a-limit dextrins

61
Q

How is maltose broken down in the small intestine?

A

Hydrolysed by maltase into 2 isolated glucose units

62
Q

How is maltotriose broken down in the small intestine?

A

Hydrolysed by maltase into 1 glucose and 1 maltose

63
Q

How is lactose broken down in the small intestine?

A

Hydrolysed into 1 unit glucose and 1 galactose

64
Q

How is sucrose broken down in the small intestine?

A

Hydrolysed by sucrase into 1 fructose and 1 glucose

65
Q

What is the SGLT1?

A

Sodium-coupled glucose transporter, transports glucose and galactose across the apical membrane of the SI

66
Q

What is the GLUT5?

A

Glucose-transporter 5, transports fructose across apical membrane using facilitated diffusion (small intestine)

67
Q

What is GLUT2?

A

Glucose-transporter 2, transports glucose, galactose and fructose across the basolateral membrane (small intestine) via facilitated diffusion

68
Q

How many types of amino acid transport are there across the apical membrane?

A

7

Physiology 1B (6 decks)

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