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THE PATIENT > GI ANATOMY > Flashcards

GI ANATOMY Flashcards

1
Q

What is the GIT/alimentary canal composed of?

A 
mouth
pharynx
oesophagus
stomach
small intestine 
large intestine
rectum 
anus
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2
Q

What are the secondary accessories of the GIT?

A 
teeth
tongue
salivary glands
liver 
pancreas
gall bladder
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3
Q

What are the 4 parts of the large intestine?

A

cecum
colon
rectum
anus

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4
Q

What is the role of the rectum?

A

to store faeces

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5
Q

What is the role of large intestine?

A

Absorbs water and electrolytes from residual food contents from small intestine

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6
Q

What do the salivary glands produce?

A

Secrete saliva

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7
Q

What does saliva contain?

A 
Amylase
lipase
mucin
water
ions
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8
Q

What are the 3 types of salivary glands?

A

Parotid- sides of cheek/face
sub mandibular- below jaw
sublingual- under tongue

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9
Q

What is the role of the oesophagus?

A

Transfers food from Pharynx to stomach

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10
Q

What is the structural composition of the oesophagus?

A

Upper sphincter- allows food to pass

lower sphincter- allows food into stomach and keeps it their and prevents heartburn and acid reflux

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11
Q

What causes gastric acid reflux into oesophagus?

A

Lower oesophageal sphincter relaxation

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12
Q

What is the role of the pancreas?

A 
Secretes digestive enzymes 
amylase for starch digestion
lipase for lipid digestion
trypsin and chymotrypsin 
HCO3 secretion= neutralises duodenum gastric acid
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13
Q

What is the role of the liver?

A

Synthesises bile acids- taurocholic acids

bile acids needed for lipid emulsification for absorption of fat soluble vitamins

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14
Q

What is the mechanism of bile acid synthesis?

A

Acetyl co A produces bile acid
stored in gall bladder then into bile duct then into duodenum and absorbed from ileum to liver
AcoA recycled and reused
cholesterol= intermediate product and high levels= atherosclerosis

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15
Q

What is the role of the stomach?

A

protein digestion

some absorption

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16
Q

What are the contents of the stomach?

A

proteases- pepsinogen

gastric acid= hcl + mucous + water + enzymes + electrolytes

17
Q

What cell types make up the stomach and what is their?

A

G cells= found in antrum and secrete gastrin
Mucous secreting cells in cardiac region
Chief cells found in fundus or stomach body and secretes pepsinogen and lipase
Parietal/oxyntic cells and secrete hcl by 3 processes
1. sight and smell of food= brain signals g cells to release gastrin and stomach stretching also releases gastrin this binds to parietal cell receptor synthesising H+/K+ atpase so H+ secreted into stomach
2. stomach nerves= Ach released and binds parietal cell receptor producing HCl
3. Ach binds enterochromaffin ECL cells and releases histamine which binds parietal cell receptor and produces HCl

18
Q

Describe the positive feedback mechanism of chief cells?

A

pepsinogen secreted in inactive pepsin form/zymogen
pepsin secreted into stomach lumen
exposed to HCl
converted into active pepsin
when more pepsinogen secreted its converted into pepsin by the action of pepsin acting by a positive feedback mechanism

19
Q

How is the stomach protected from HCl and proteases?

A

Alkaline mucous barrier from foveolar cells
Tight junctions between epithelial cells so HCl and protease movement restricted
High cell turnover
Cell migration every 2-3 days to replace damaged cells and maintain the barrier

20
Q

What are the consequences of the mucous barrier being broken?

A

HCl and protease exposed to epithelial cells
food secretions and bacteria enter peritoneal cavity
cause damage to blood vessels and GIT bleeding= gastric/duodenal ulcers and peritonitis

21
Q

What is the role of the small intestine?

A

Absorption

some digestion

22
Q

What does the intestinal juice contain?

A

carb digesting enzymes maltase, lactase and sucrase

23
Q

Describe the structure of the small intestine?

A

duodenum
jejunum
ileum

24
Q

Explain the structural adaptations of the small intestine?

A

Plicae= folds= increase SA
Villi= finger like projections on the plicae= increase SA
Microvilli= microscopic projections on villi= increase SA
Epithelium one cell thick= short diffusion distance from lumen to circulatory system
Enterocytes= responsible for digestion as they have enzymes that convert non-absorbable macro molecules to absorbable small molecules

25
Q

Describe carbohydrate digestion and absorption in the small intestine?

A

Digestion
Sucrase= sucrose to glucose + fructose
Lactase= lactose to glucose + galactose
Maltase= maltose to glucose + glucose

Absorption
Glucose and galactose= SGLT1 or Na/glucose transporter allows entry into enterocytes from lumen high conc down electrochemical gradient
Fructose= Na dependent GLUT 5 transporter in basolateral memb

26
Q

Describe protein digestion and absorption in the small intestine?

A

Digestion
Proteins digested by protease into small peptides and AA’s

Absorption
small peptide= H+ dependent PEPT1 down electrochemical gradient form high conc lumen to low conc cell

27
Q

Describe Lipid absorption in the small intestine?

A

triglyceride into free fatty acids
solubilised by bile acids into micelle
micelle absorbed by diffusion

28
Q

What is another type of absorption that also occurs in the small intestine?

A

mineral absorption

29
Q

What are the steps in the swallowing process?

A
  1. Food swallowed
  2. Food down oesophagus
  3. Oesophagus passes through diaphragm through the oesophageal hiatus then to stomach
30
Q

What structures are involved in the swallowing process?

A
  1. Trigeminal nerve
  2. Facial- tongue, tonsils
  3. Glossopharyngeal nerve
  4. Hypoglossal nerve
  5. Vagus nerve
31
Q

How is the swallowing process initiated?

A

Mouth and throat receptors relay information to medulla oblongata in brain stem
Brain processes information about food
Brain sends impulses to throat musculature
Process of swallowing triggered

32
Q

Describe the gastric acid secretion mechanism?

A

G cells in antrum= gastrin into blood in response to food
Activates receptor on ECL cells
ECL releases histamine
Histamine binds parietal cell receptor
Induces h+/k+ atpase
Acid release into lumen suppresses gastrin release

33
Q

What is peristalsis?

A

Wave of muscular contraction which propels contents along GIT

34
Q

Describe the mechanism of peristalsis?

A

Circular muscles in intestine contract= moves food bolus along GIT
Material doesn’t move backwards
Longitudinal muscle contract: squeezes on the food pushing it forward
Then more circular muscle encountered

THE PATIENT (8 decks)

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