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GI Alimentary Year 2 Medicine > GI physiology > Flashcards

GI physiology Flashcards

1
Q

Grand tour of alimentary canal

what are the 4 main processes of the digestive system?

A
  • Digestion
  • Secretion
  • Absorption
  • Motility
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2
Q

Grand tour of alimentary canal

Is the lumen part of the inside or outside of the body?

A

Lumen is technically outside of body. Continuous tube from mouth to anus.

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3
Q

Grand tour of alimentary canal

What is gastric motility?

A

Movement of material from mouth to anus

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4
Q

Grand tour of alimentary canal

Explain Gastric motility

A
  • Peristaltic contractions originate in the upper fundus, move to pyloric sphincter
  • Moves gastric chyme forward → gastric emptying into duodenum
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5
Q

Grand tour of alimentary canal

Explain GI Absorption of nutrients and locations

A

○ Digested nutrients absorbed by GI mucosal cells into blood/lymph (liver will filter out before entering blood etc)

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6
Q

Grand tour of alimentary canal

name the Accessory Organs

A

Gallbladder, liver, pancreas

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7
Q

Grand tour of alimentary canal

In relation to GI explain what the liver does

A

Hepatocytes produce bile which emilsifies lipid globules, aids in abdorption

Stores glucose in form of glycogen

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8
Q

Grand tour of alimentary canal

in relation to GI explain the function of Gallbladder

A

Storage and concentrated Bile; releases bile into small intestine in reponse to hormonal stimulus

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9
Q

Grand tour of alimentary canal

In relation to GI explain the function of the pancreas

A

Exocrine function: acini secrete various digestive enzymes; “pancreatic juice;” e.g. secretin, cholecystokinin (CCK)

Endocrine function: islets produce glucagon, insulin to maintain normal glucose levels; somatostatin, pancreatic polypeptide production

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10
Q

Grand tour of alimentary canal

Explain the function of the mouth

A

Foodstuffs are broken down by chewing; saliva is added as a lubricant

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11
Q

Grand tour of alimentary canal

Explain the function of the oesophagus

A

Acts as a conduit between the mouth and the stomach

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12
Q

Grand tour of alimentary canal

Explain the function of the stomach

A

for Digestion of proteins; foodstuffs reduced to liquid form

for storage

for sterilisation hydrochloric acid and kills microorganisms.

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13
Q

Grand tour of alimentary canal

What is the function of the pancreas in the alimentary system?

A

Production of digestive enzymes for digestion of fats, carbohydrates and proteins

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14
Q

Grand tour of alimentary canal

What is the function of the small intestine?

A

Final stages of chemical digestion and nutrient absorption

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15
Q

Grand tour of alimentary canal

What is the function of the large intestine?

A

Water absorption
Bacterial fermentation
Formation of faeces

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16
Q

Grand tour of alimentary canal

Name the four layers of the alimentary canal?

A

Mucosa
Submucosa
Muscularis external
Serosa/ adventitia

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17
Q

Grand tour of alimentary canal

What type of epithelium is found in the mouth, oesophagus and anal canal?

A

Stratified squamous

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18
Q

Grand tour of alimentary canal

What are the layers of mucosa?

A

epithelium
lamina propria
muscularis mucosa

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19
Q

Grand tour of alimentary canal

What type of epithelium is found in the stomach and intestines?

A

simple columnar

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20
Q

Grand tour of alimentary canal

What is the function of the epithelium in the alimentary canal?

A

Synthesis and secretion of digestive enzymes, hormones, mucus
Absorbs products of digestion

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21
Q

Grand tour of alimentary canal

What is the lamina propria?

A

loose connective tissue

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22
Q

Grand tour of alimentary canal

What is the muscularis mucosae?

A

thin layer of smooth muscle

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23
Q

Grand tour of alimentary canal

What does the submucosa contain?

A

Neurones
Blood vessels
Lymphatic vessels

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24
Q

Grand tour of alimentary canal

Where are the submucosal glands found?

A

Oesophagus
Duodenum

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25
Q

Grand tour of alimentary canal

What do the neurones in the submucosa form?

A

Parasympathetic submucosal plexus

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26
Q

Grand tour of alimentary canal

Describe the submucosa layer

A

Thick, irregular connective tissue

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27
Q

Grand tour of alimentary canal

What is the serosa?

A

Connective tissue outer layer

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28
Q

Grand tour of alimentary canal

What is the difference between serosa and adventitia

A

Adventitia is outside peritoneal cavity
Serosa is inside peritoneal cavity

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29
Q

Grand tour of alimentary canal

What does serosa surround?

A

Stomach
Small intestine
Large intestine

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30
Q

Grand tour of alimentary canal

What does the adventitia attach?

A

Oesophagus and rectum to surrounding structures

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31
Q

Grand tour of alimentary canal

What is the muscularis externa?

A

Two concentric thick laters of smooth muscle

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32
Q

Grand tour of alimentary canal

What type of muscle in the inner layer of muscularis externa?

A

Circular muscle

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33
Q

Grand tour of alimentary canal

What type of muscle in the outer layer of muscularis externa?

A

Longitudinal muscle

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34
Q

Grand tour of alimentary canal

Where is the myenteric plexus located?

A

Between the inner circular and outer longitudinal muscular layers

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35
Q

Grand tour of alimentary canal

What is the function of muscularis externa?

A

peristalsis and segmentation

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36
Q

Grand tour of alimentary canal

What is the enteric nervous system made up of?

A

submucosal plexus and myenteric plexus

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37
Q

Grand tour of alimentary canal

What is the function of the enteric nervous system?

A

Independent control of gut function

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38
Q

Grand tour of alimentary canal

What provides autonomic control of the alimentary canal?

A

Long parasympathetic and short ENS reflexes

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39
Q

Grand tour of alimentary canal

What provides parasympathetic control of the alimentary canal?

A

Vagus nerve

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40
Q

Grand tour of alimentary canal

What nerves control salivation?

A

Facial (7th)
Glossopharyngeal (4)

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41
Q

Grand tour of alimentary canal

What provides sympathetic control of the alimentary canal?

A

Splanchnic nerve

Splachnic = Sympathetic

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42
Q

Grand tour of alimentary canal

What does the celiac trunk supply?

A

Stomach
Small intestine
Pancreas
Liver

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43
Q

Grand tour of alimentary canal

What does the superior mesenteric artery supply?

A

Small intestine
Caecum
Ascending colon
Transverse colon

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44
Q

Grand tour of alimentary canal

What does the inferior mesenteric artery supply?

A

Descending colony
Sigmoid colon
Rectum

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45
Q

Grand tour of alimentary canal

What provides venous drainage from the stomach?

A

Gastric veins

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46
Q

Grand tour of alimentary canal

What provides venous drainage from the pancreas?

A

Splenic vein

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47
Q

Grand tour of alimentary canal

What does all venous drainage from GI tract travel via?

A

Hepatic portal vein

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48
Q

Grand tour of alimentary canal

what is splenic artery branch of

A

Coeliac trunk behind pancreas

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49
Q

Grand tour of alimentary canal

portal triad

A

Common hepatic duct, portal vein hepatic artery

in lesser omentum.

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50
Q

Grand tour of alimentary canal

Name the monosaccharides

A

glucose, fructose, galactose

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51
Q

What are monosaccharides?

A

Hexose sugars

simplest carbohydrates (simplest sugars)

prefix indicates number of carbons: suffix –ose, indicates a saccharide

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52
Q

What are disaccharides?

A

two monomers linked by glycosidic bond

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53
Q

What are disaccharides broken down by?

A

Brush boarder enzymes in small intestine epithelial cells (enterocytes)

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54
Q

What is lactose made of?

A

glucose and galactose

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55
Q

What is sucrose made of?

A

glucose and fructose

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56
Q

What is maltose made of?

A

glucose and glucose

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57
Q

Name the polysaccharides

A

starch, glycogen, cellulose

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58
Q

What is starch?

A

storage form of glucose in plants

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59
Q

What are glucose monomers in starch linked by?

A

Alpha-1,4 glycosidic bonds

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60
Q

What makes glucose chains branched?

A

Amylopectin

70%-80% of starch)

Similar structure as amylose but branched

Glycosidic (α-4) bonds join glucose in the chains but branches

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61
Q

What links glucose in straight chains?

A

Alpha-amylose

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62
Q

How is stratch hydrolysed and where

A

Hydrolysed by amylases (saliva, pancreas)

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63
Q

Describe the structure of cellulose

A

Unbranched linear changes of glucose monomers

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64
Q

What links the cellulose chains?

A

B-1,4 glycosidic bonds

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65
Q

What are the glucose monomers in glycogen linked by?

A

Alpha 1,4 glycosidic bonds

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66
Q

What digests polysaccharides?

A

Alpha amylase

Mouth:

Begins carbohydrate digestion

Enzyme: salivary amylase hydrolyses (α1→ 4) bonds of starch

Starts starch digestion → Dextrins, maltose, maltotriose

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67
Q

Can we absorb disaccharides?

A

No

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68
Q

What does SGLT1 transport?

A

glucose and sodium

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69
Q

What does SGLT1 absorb?

A

Galactose

SGLT1 also helps get WATER into body

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70
Q

What channel does glucose move out the cell?

A

Glut-2

absorbed into enterocytes via sodium ion cotransport (secondary active transport) → GLUT2 transporter extrudes glucose, galactose across basolateral membrane into blood in apical membrane → GLUT2 transporter extrudes fructose across basolateral membrane into blood;

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71
Q

How does fructose enter the cell?

A

(GLUT5)

absorbed into enterocytes via facilitated diffusion by GLUT5 transporter in apical membrane → GLUT2 transporter extrudes fructose across basolateral membrane into blood; fructose absorption cannot occur against electrochemical gradient. Moved down concentration gradient (↑ in gut lumen ↓ in blood)

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72
Q

What are proteins?

A

polymers of amino acids linked by peptide bonds

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73
Q

What are peptides?

A

Small proteins, 3-10 amino acids in length

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74
Q

What is the addition of CHO to a protein called?

A

Glycoproteins

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75
Q

What is the addition of a lipid to a protein called?

A

Lipoprotein

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76
Q

What are proteases?

A

Enzymes which hydrolyse peptide bonds and reduce proteins

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77
Q

What does endopeptidase do?

A

digests internal peptide bonds

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78
Q

What does exopeptidase do?

A

Digests terminal peptide bonds

Proteases (endopeptidases, exopeptidases

Endopeptidases: tripsin, chymotrypsin, pepsin; hydrolyse interior peptide bonds

Digest large polypeptides/peptide

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79
Q

Name the types of exopeptides?

A

Aminopeptidase
Carboxypeptidase

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80
Q

What do amino acids travel through the cell via?

A

SAAT1 with sodium

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81
Q

What does PEPT1 transport?

A

Hhydrogen
Dipeptide

PepT1 (hydrogen dependent) in bacteria transports around 70% protein in diet.

Penicillin tripeptide is transported via PepT1.

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82
Q

What happens to the hydrogen that enters the cell with the dipeptide?

A

Exits via NHE3 to allow sodium to enter cell

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83
Q

What is most of the ingested fat in the form of?

A

Triacylgycerol

(triglycerides)

Esters of fatty acids and glycerol. (Esters - neutral uncharged lipids)

Water insoluble large lipid droplets

Dietary fuel and insulation.

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84
Q

What is all fat digested by? Where?

A

Pancreatic enzymes (pancreatic lipase, cholesterol ester hydrolyse, phospholipase A2) colipase finish digestion in small intestine. Lipase = water-soluble

Promote emulsification (dispersion) by bile salts & peristalsis (mixing) amphipathic (charged polar and non-polar non-charged) stop reaggregation,

Site of digestion: small intestine by pancreatic enzyme

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85
Q

Why is fat digestion so slow?

A

As digestion can only take place at surface of droplet

emulsify dietary lipids from large lipid droplets into smaller droplets → create ↑ surface area for pancreatic enzymes.

Nonpolar- lipid interior

Polar - water at surface, repels other droplets.

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86
Q

What is emulsification?

A

Dividing large lipid droplets into smaller droplets

(dispersion) by bile salts & peristalsis (mixing)

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87
Q

What does emulsification do?

A

Increase surface area and accessibility of lipase action

mulsify dietary lipids from large lipid droplets into smaller droplets → create ↑ surface area for pancreatic enzymes.

Nonpolar- lipid interior

Polar - water at surface, repels other droplets.

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88
Q

What does emulsification require?

A

Mechanical disruption
Emulsifying agent

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89
Q

What produces mechanical disruption for emulsification?

A

Smooth muscle contraction grinds and mixes lumeneal contents

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90
Q

What produces mechanical disruption for emulsification?

A

Smooth muscle contraction grinds and mixes lumeneal contents

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91
Q

Why is an emulsifying agent needed in the formulation of an emulsion?

A

Prevents small droplets reforming into large droplets

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92
Q

Give examples of emulsifying agents

A

Bile salts and phospholipids secreted in bile
Amphiaphatic molecules

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93
Q

What do polar portions do in terms of emulsification?

A

Repel other small lipid droplets and prevent reforming into large droplets

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94
Q

What is absorption of lipase digestion enhanced by?

A

Formation of micelles

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95
Q

What are micelles made of?

A

Bile salts
Monoglycerides
Fatty acids
Phospholipids

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96
Q

Where are the polar portions of molecules found on micelle?

A

Surface

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97
Q

What part of the micelle do non polar portions form?

A

Core

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98
Q

Describe micelle breakdown

A

Release of small amounts of free fatty acids and monoglycerides into solution resulting in diffusion across plasma membrane of absorbing cells

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99
Q

What does the dynamic equilibrium between fatty acids and monoglycerides in solution and in micelles retain?

A

Most of fat digestion products in solution while constantly replenishing supply of free molecules for absorption

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100
Q

What does the dynamic equilibrium between fatty acids and monoglycerides in solution and in micelles retain?

A

Most of fat digestion products in solution while constantly replenishing supply of free molecules for absorption

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101
Q

What happens to epithelial cels, fatty acids and monoglycerides when the enter the smooth endoplasmic reticulum?

A

They are reformed to triacylglycerolsThey are reformed to triacylglycerols

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102
Q

What are triacylglycerols droplets coated with?

A

Amphiphatic protein for emulsification

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103
Q

What are triacylglycerols droplets transported though?

A

Cell in vesicles from sER membrane

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104
Q

What are triacylglycerols droplets processed though?

A

Golgi apparatus and exocytosed into Extracellular fluid at serosa membrane

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105
Q

What are chylomicrons?

A

Extracellular fat droplets

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106
Q

Where do chylomicrons pass into?

A

Lacteals between endothelial cells

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107
Q

What are lacteals?

A

Finger like projections

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108
Q

What are the two classes of vitamins?

A

fat soluble and water soluble

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109
Q

What are the fat soluble vitamins?

A

A, D, E, K

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110
Q

What are the water soluble vitamins?

A

B, C and folic acid

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111
Q

What are the water-soluble vitamins absorbed by?

A

Passive diffusion or carrier- mediated transport

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112
Q

What are the water soluble vitamins absorbed by?

A

Passive diffusion or carrier- mediated transport

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113
Q

What is vitamin b12?

A

vitamin - large charged molecule (can not across membrane)

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114
Q

What does vitamin b12 bind to?

A

binds to intrinsic factor in stomach form complex → absorbed via specific transport mechanism in distal ileum

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115
Q

What is the vitamin B12 intrinsic factor complex absorbed via?

A

Specific transport mechanism in distal ileium

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116
Q

What does B12 deficiency lead to?

A

pernicious anemia

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117
Q

What is iron transported across?

A

Brush border membrane via DMT1 into duodenal enterocytes

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118
Q

What does iron in blood bind to?

A

Transferrin

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119
Q

What are iron ions incorporated into?

A

Ferritin

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120
Q

What is hyperaemia?

A

Increased ferritin levels so more iron bound in enterocytes

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121
Q

What is anaemia?

A

Decreased ferritin levels so more iron released to blood

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122
Q

What is ferritin expression regulated depending on?

A

Body’s irons status

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123
Q

The process of chewing is for…

A

Prolong taste experience
Defence against respiratory failure

food broken down into smaller pieces is easier to digest.

When mixed with saliva, allows the body to extract the greatest possible amount of nutrients

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124
Q

How is chewing voluntary controlled?

A

Somatic nerves innervate skeletal muscles of the mouth/ jaw

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125
Q

Describe the chewing reflex

A
  • Contraction of jaw muscles causing pressure of food against gums
  • Hard palate and tongue stimulates mechanoreceptors stimulation inhibition of jaw muscles reducing pressure
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126
Q

What glands secrete saliva?

A

parotid, submandibular, sublingual

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127
Q

What is in saliva?

A

Water - mucosal integrity
Mucins - lubrication, digestion, pellicle formation
Alpha- amylase - initiates digestion in stomach
Electrolytes - moistens food
Lysozyme - cell membrane hydrolysis

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128
Q

What is the function of water in saliva?

A

Softens, moistens and dilutes particles

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129
Q

What is the function of mucins in saliva?

A

lubrication

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130
Q

What is the major protein component of saliva?

A

Mucins

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131
Q

What is the function of alpha-amylase in saliva?

A

Catalyses breakdown of polysaccharides into disaccharide and glucose

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132
Q

What is the function of electrolytes in saliva?

A

Maintains tonicity

133
Q

What is the function of lysozyme in saliva?

A

Bactericidal - cleaves polysaccharides component of bacterial cell wall

134
Q

What controls salivary secretion?

A

Parasympathetic and sympathetic ns

135
Q

What are the parasympathetic nerves that control salivary secretion?

A

Cranial nerves VII and IX

136
Q

What is the stimulation of sympathetic nerves that control salivary secretion?

A

Small volume, viscous salivary secretion

137
Q

What is the stimulation of parasympathetic nerves that control salivary secretion?

A

Profuse watery salivary secretion

138
Q

Describe the reflex control of salivary secretion?

A

Presence of food in mouth stimulates chemoreceptors and pressure receptors

139
Q

What are the layers of the oesophagus

A

mucosa, submucosa, muscularis, adventitia

140
Q

what supplied blood to the thoracic part of the oesophagus

A

Azygous and hemizygous veins

141
Q

What are the layers of the oesophagus

A

mucosa, submucosa, muscularis, adventitia

142
Q

What is the mucosa in the oesophagus lined by?

A

Nonkeratinized stratified squamous epithelium

143
Q

What regulates movement of material into and out of oesophagus?

A

Upper and lower oesophageal sphincters

144
Q

What is the muscularis externa in the oesophagus made up of?

A

Upper 1/3 - skeletal muscle
Lower 1/3 - smooth muscle

145
Q

What happens in the oral phase of swallowing?

A

Bolus pushed back of mouth by tongue from oral cavity into the oropharynx; voluntary process

146
Q

What happens in the pharyngeal phase of swallowing?

A

Presence of bolus initiates sequence of reflex contractions of pharyngeal muscle
Soft palate reflected backwards and upwards

147
Q

What co-ordinates the pharyngeal phase of swallowing?

148
Q

What happens of the bolus approaches the oesophagus?

A

Upper oesophageal sphincter relaxes and epiglottis covers opening to larynx

149
Q

What happens when food enters the oesophagus?

A

Upper oesophageal sphincter contracts

150
Q

What happens in the oesophageal phase of swallowing?

A

Propulsion of bolus to stomach
The peristaltic wave sweeps along the entire oesophagus

151
Q

What happens as the bolus nears the stomach?

A

Lower oesophageal sphincter relaxes and bolus enters stomach

152
Q

What is the receptive relation of the stomach initiated by?

A

Relaxation of LOS and entry of bolus into stomach

153
Q

What causes receptive relaxation of stomach?

A

Vagal reflexes, relaxation of thin elastic smooth muscle of gastric fundus and body

154
Q

What are the functions of the stomach?

A

Temporary storage of food
Dissolve food particles and initiate digestive process
Control delivery of contents to small intestine
Sterilise ingested material
Produce intrinsic factor

155
Q

What does the oesophagus enter the cardiac region of the stomach via?

A

Gastroesophageal opening

156
Q

Name the layers of the muscularis externa in the stomach

A

Longitudinal
Circular
Oblique

157
Q

What is the outer layer of the stomach?

158
Q

What does the submucosa and mucosa look like when the stomach is empty?

159
Q

What does the body of the stomach secrete?

A

Mucus
HCL
Pepsinogen
Intrinsic factor

160
Q

What part of the stomach are involved in storage?

A

Fundus and body

161
Q

What is the function of the Antrum?

A

Mixing and grinding
Secretes gastrin

162
Q

What do mucous neck cells secrete?

163
Q

What do chief cells secrete?

A

pepsinogen

164
Q

What do parietal cells secrete?

A

HCl and intrinsic factor

165
Q

What is the gastric pit?

A

Gastric pits are indentations in the stomach that denote entrances to the gastric glands.

166
Q

What happens to H2CO3 in the cells of the stomach?

A

Broken down into H and HCO3
Hydrogen enters the stomach lumen in exchange for potassium
HCO3 exits to blood in exchange for Cl

167
Q

What happens to Cl in the cells of the stomach?

A

Exits to acidic stomach lumen

168
Q

What binds to receptors to allow ca to enter the cells of the stomach?

A

Gastrin and acetylcholine

169
Q

What does histamine bind to and what is the effect?

A

Binds to GS which binds to AC to stimulate the conversion of ATP to cAMP

170
Q

What do prostaglandins bind to and what is the effect?

A

Binds to GI to inhibit conversion of ATP to cAMP

171
Q

Name the mechanisms which gastric acid secretion is controlled by?

A

Neurocrine
Endocrine
Paracrine

172
Q

Describe the cephalic phase

A

Sight, smell and taste of food stimulate the vagus nerve to produce gastrin and aCh to stimulate parietal cells
Gastrin and aCH also acts on ECL cells to produce histamine

173
Q

Describe the gastric phase

A

Distension of stomach stimulates vagal/enteric reflects to produce Ach
Peptides in the lumen stimulate G cells to produce gastric
Gaston/ACH acres on ECL cells to produce histamine

174
Q

How is the cephalic phase inhibited?

A

Stopping eating decreases vagal activity

175
Q

How is the gastric phase inhibited?

A

Increased HCL decreases PH and therefore Gastrin

176
Q

How is the intestinal phase inhibited?

A

Acid in duodenum stimulates enterogastic reflex and release of secretion decreasing gastrin secretional and stimulation

177
Q

What decreases parietal HCL secretion in the intestinal phase?

A

Fat/ CHO in duodenum stimulating GIP release

178
Q

What are enterogastrones?

A

Hormones released from gland cells in duodenal mucosa

179
Q

Give examples of enterogastrones

A

Secretion
CCK
GIP

180
Q

What are enterogastrones released in response to?

A

Acid, hypertonic solutions, fatty acids or monoglycerides in duodenum

181
Q

What do enteroendocrine cells do?

A

Act collectively to prevent further acid build up in duodenum

182
Q

Name the strategies that enterogastrones use to prevent acid build up?

A

Inhibit gastric acid secretion
Reduce gastric emptying

183
Q

What simulates the conversion of pepsinogen to pepsin?

184
Q

What does zymogen storage prevent?

A

Cellular digestion

185
Q

Define zymogen

A

inactive enzyme precursor

186
Q

When are pepsins inactivated?

A

Neutral pH

187
Q

What is the role of gastric mucus?

A

Protects mucosal surface from mechanical injury
Neutral pH protects against gastric acid corrosion and pepsin digestion

188
Q

Where do peristaltic waves move from?

A

Body to antrum

189
Q

Why is there no mixing in the body?

A

Due to thin muscles causing a weak contraction

190
Q

What is the function of the thick muscle in the antrum?

A

Mixing
Contraction of the pyloric sphincter

191
Q

What is the result of the pyloric sphincter contracting?

A

Only small quantity of gastric content entering the duodenum
Further mixing as antral contents forced back towards body

192
Q

What produces peristaltic waves?

A

Peristaltic rhythm
Slow waves

193
Q

What is the peristaltic rhythm generated by?

A

Pacemaker cells in the longitudinal muscle layer

194
Q

What is the slow wave rhythm also known as?

A

Basic electrical rhythm

195
Q

Where are slow waves conducted though?

A

Gap junctions along longitudinal muscle layer

196
Q

What determines the strength of contraction of the slow wave?

A

Number of action potentials

197
Q

How does gastrin affect contraction?

198
Q

What are secreted by Brunner’s gland duct cells?

A

Bicarbonate

199
Q

What does acid in the duodenum trigger?

A

Long vagal and short ENS reflected and release of secretin from S cells stimulating HCO3 secetion

200
Q

What does acid neutralisation inhibit?

A

Secretin release

201
Q

Where is the head of the pancreas located?

A

in the curve of the duodenum

202
Q

Where is the endocrine portion of the pancreas located in?

A

Islets of Langerhans

203
Q

What do islet cells produce?

A

Insulin
Glucagon
Somatostatin

204
Q

What does somatostatin do?

A

Controls secretion of insulin and glucagon

205
Q

Where is the exocrine portion of the pancreas located?

A

Acinar cells

206
Q

What do lobules connected by intercalated ducts form?

A

Intralobular ducts which form the main pancreatic duct

207
Q

What is the sphincter of Oddi?

A

opens and closes common bile duct entrance into the duodenum

208
Q

What is the exocrine pancreas responsible for?

A

Digestive function of pancreas

209
Q

What do duct cells secrete?

A

Bicarbonate

210
Q

What do acinar cells secrete?

A

digestive enzymes

211
Q

How are digestive enzymes stored in acinar cells? And why?

A

As zymogen granules to prevent auto digestion of pancreas

212
Q

What converts trypsinogen to trypsin?

A

enterokinase

213
Q

What does trypsin do?

A

Converts zymogen to active forms

214
Q

What is the function of proteases?

A

cleave peptide bonds

215
Q

What is the function of nucleases?

A

Hydrolyse DNA/RNA

216
Q

What is the function of elastase?

A

Collagen digestion

217
Q

What is the function of phospholipase?

A

splits fatty acids from phospholipids

218
Q

What is the function of lipases?

A

Hydrolysis of triacylglycerols to fatty acids and glycerol

219
Q

What is the function of alpha-amylase?

A

starch digestion

220
Q

What is bicarbonate secretion stimulated by?

221
Q

What is secretin released in response to?

A

low pH in duodenum

222
Q

What is zymogen secretion stimulated by?

223
Q

What is CCK released in response to?

A

presence of fat in the duodenum

224
Q

What is the largest internal organ?

225
Q

Where is the liver located?

A

Upper right quadrant of abdomen

226
Q

Name two minor lobes liver

A

caudate and quadrate

227
Q

What are the two major liver nodes?

A

Right and left

228
Q

What blood vessels supply the liver?

A

Hepatic portal vein
Hepatic artery

229
Q

What lymphatic ducts supply the liver?

A

Right and left hepatic ducts

230
Q

What nerves supply the liver?

A

Hepatic nerve plexus

231
Q

What do vessels enter the liver via?

A

Porta on inferior surface

232
Q

What is the common hepatic duct joined by?

A

Cystic duct from gallbladder

233
Q

What is the bare area of the liver?

A

Small area on diaphragmatic surface surrounded by coronary ligament

234
Q

What do the septa divide into?

A

Hexagonal lobules

235
Q

What is located at the corner of each hexagonal lobule?

A

Portal triad

236
Q

What is the portal triad made up of?

A

Hepatic artery, common bile duct, portal vein

237
Q

What do connective tissues capsules form at the porta?

A

The branching network of septa

238
Q

What radiates out from central veins?

A

Hepatic cords

239
Q

What are hepatic cords composed of?

A

hepatocytes

240
Q

Define hepatocytes?

A

Functional cells of liver

241
Q

What are the spaces between hepatic cords called?

A

Hepatic sinusoids

242
Q

What lies between cells within each hepatic cord?

A

Bile canliculus

243
Q

What is the function of hepatocytes?

A

synthesize bile
Nutrient storage

244
Q

Name the six components of bile

A

Bile acids
Lecithin
Cholesterol
Bile pigments
Toxic metals
Bicarbonate

245
Q

Where are toxic metals detoxified?

246
Q

What is HCO3 secreted by?

A

Duct cells

247
Q

What part of bile is synthesised in the liver and solubilises fat?

A

Bile acids
Lecithin
Cholesterol

248
Q

What are bile pigments?

A

breakdown products of haemoglobin

249
Q

What causes yellow bile?

A

Bilirubin extracted from blood by hepatocytes and secreted into bile

250
Q

What causes brown faeces?

A

Bilirubin modified by bacterial enzymes

251
Q

What causes yellow urine

A

Reabsorbed bilirubin excreted in urine

252
Q

What is the predominant bile pigment?

253
Q

Where are bile acids synthesised?

A

In liver from cholesterol

254
Q

What do bile acids conjugate with before secretion?

A

Glycine to taurine to form bile salts

255
Q

What are secreted bile salts recycled via?

A

Enterohepatic circulation

256
Q

Where is the gallbladder located?

A

inferior surface of the liver

257
Q

Name the layers of the gall

A

Mucosa
Muscularis
Serosa

258
Q

What type of muscle is the muscularis in the gallbladder?

A

Smooth muscle

259
Q

What does the sphincter of Oddi do?

A

Controls release of bile and pancreatic secretions into the duodenum

260
Q

What happens when sphincter of oddi contracts?

A

Bile is forced back into gallbladder

261
Q

What does the release of CCK result in?

A

Sphincter of oddi relaxes
Gallbladder contracts

262
Q

What is the longest part of the small intestine?

263
Q

Where does most nutrient absorption in the small intestine take place?

264
Q

What is the function of the duodenum?

A

Gastric acid neutralisation
Digestion
Iron absorption

265
Q

What is the function of the Ileum?

A

NaCl/H2O absorption stimulating chyme dehydration

266
Q

What are the absorptive surface of the small intestine enhanced by?

A

Folds
Villi
Microvilli

267
Q

What do crypt cells secrete?

A

Cl and water

268
Q

What do villus cells absorb?

A

NaCl
Monosaccharides
Amino acids
Peptides
Fats
Minerals
Vitamins
Water

269
Q

How much water does the small intestine secrete?

A

1500ml a day

270
Q

Where does H2O secretion come from in the small intestine?

A

Epithelial cells lining crypts of lieberkuhn

271
Q

What are crypts?

A

Tubular glands that secret juices into the small intestine

272
Q

Why is H2O secretion important for normal digestive processes?

A

Maintains luminal contents in liquid state
Promotes mixing
Nutrient presentation
Washes away injurious substances

273
Q

How does chloride leave the cell?

A

Via CFTR genes

274
Q

What does adenylyl cyclase do?

A

converts ATP to cAMP

275
Q

Name the two types of movement in the intestines?

A

Segmentation
Peristalsis

276
Q

Which intestinal movement is most common during a meal?

A

Segmentation

277
Q

What does segmentation bring chyme into contact with?

A

Absorbing surface

278
Q

Describe the process of segmentation

A

Contraction moves chyme into adjacent areas of relaxation
Related areas then contract and push chyme back
Provides thorough mixing

279
Q

What is segmentation contractions initiated by?

A

Depolarisation generated by pacemaker cells in longitudinal muscle layer

280
Q

What is the frequency of segmentation determined by?

A

Basic electrical rhythm

281
Q

What does the basic electrical rhythm produce?

A

Oscillations in membrane potential causing contraction

282
Q

How does BER differ throughout the body?

A

Decreases as moves down intestine to rectum

283
Q

What does segmentation produce?

A

Slow migration of chyme towards large intestine

284
Q

How does the parasympathetic nervous system affect segmentation contractions?

A

Increases contractions

285
Q

How does the sympathetic nervous system affect segmentation contractions?

A

Decreases contractions

286
Q

How does the autonomic nervous system affect segmentation contractions?

287
Q

When does peristalsis begin?

A

Following absorption of nutrients

288
Q

What stops the migrating motility complex

A

Arrival of food in stomach

289
Q

What hormone is involved in the initiation of MMC?

290
Q

What is the migrating motor complex?

A

Pattern of peristaltic activity travelling down small intestine

291
Q

Where does the migrating motor complex begin?

A

Gastric antrum

292
Q

What does the MMC act to do?

A

Move undigested material into large intestine
Limit bacterial colonisation of small intestine

293
Q

What happens if the intestinal smooth muscle is distended?

A

Muscle on oral side contacts
Muscle on anal side relaxes
Bolus is moved towards colon

294
Q

What mediates the law of the intestine?

A

Neurones in myenteric plexus

295
Q

What does gastric emptying increase?

A

Segmention activity in ileum

296
Q

What is the result of increased segmentation activity in the ileum?

A

Opening of iloecaecal valves
Entry of chyme into large intestine
Distension of colon
Reflex contraction of ileocaecal sphincter

297
Q

What does reflex contraction of ileocaecal sphincter prevent?

A

Backflux into small intestine

298
Q

What does the ileum enter the caecum via?

A

Ileocaecal valve

299
Q

Name the parts of the colon

A

ascending, transverse, descending, sigmoid

300
Q

Which muscle layer of the small intestine is incomplete?

A

Longitudinal layer

301
Q

What are teniae coli?

A

3 separate longitudinal ribbons of smooth muscle that run the length of the colon

302
Q

What do contractions of teniae coli result in?

303
Q

What is the mucosa of the large intestine comprised of?

A

Simple columnar epithelium

304
Q

What provides lubrication for movement of faeces?

A

Large straight crypts lines with large number of goblet cells

305
Q

What is the mucosa of the rectum?

A

Simple columnar epithelium

306
Q

How does he muscularis externa in the rectum differ?

A

It is thicker compared to other regions of alimentary canal

307
Q

What type of muscle is the external anal sphincter?

A

skeletal muscle

308
Q

What is the internal anal sphincter made up of?

A

Muscularis thicker than rectum

309
Q

What is the epithelium in the anal canal?

A

Moves from simple columnar to stratified squamous

310
Q

What is the function of the colon?

A

Transports sodium from lumen into blood resulting in osmotic absorption of water dehydrating chyme resulting in solid faecal pellets

311
Q

Why is there a long residence time in the colon?

A

Bacterial colonisation

312
Q

What does bacterial fermentation of undigested carbohydrates result in?

A

Short chain fatty acids
Vitamin K
Gas

313
Q

What gas is found in the colon?

A

Nitrogen
CO2
Hydrogen
Methane
Hydrogen sulphide

314
Q

what is the anus closed by?

A

Internal anal sphincter and external anal sphincter

315
Q

Which anal sphincter is voluntary?

316
Q

What occurs following a meal?

A

Wave of intense contraction
Distension of rectal wall produced by mass movement of faecal mater into rectum
Urge to defaecate

317
Q

What controls the defaecation reflex?

A

Parasympathetic control via pelvic splanchnic nerves

318
Q

What happens in the defaecation reflex?

A

Contraction of rectum
Relation of internal and contraction of external anal sphincters
Increased peristaltic activity in colon

319
Q

What is the voluntary delay of defaecation controlled by?

A

Descending pathways

320
Q

What are the symptoms associated with constipation?

A

Headaches
Nausea
Loss of appetite
Abdominal distension

321
Q

What is constipation due to?

A

Distension of rectum

322
Q

What are the causes of diarrhoea?

A

Pathogenic bacteria
Protozoan
Viruses
Toxins
Food

323
Q

Define diarrhoea

A

Too frequent passage of faeces which are too liquid

324
Q

Give examples of enterotoxigenic bacteria?

A

Vibrio chloerae
Escherichia coli

325
Q

What do enterotoxigenic bacteria do?

A

Produce protein enterotoxins which maximally turn on intestinal chloride secretion from crypt cells increasing H2O secretion

326
Q

How does enterotoxigenic bacteria act by?

A

Elevating intracellular second messengers

327
Q

What is the treatment of secretory diarrhoea?

A

Drive H2O absorption
Oral rehydration therapy
Sodium/glucose solution

GI Alimentary Year 2 Medicine (7 decks)

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