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NUT1005 > The Gastrointestinal Tract > Flashcards

The Gastrointestinal Tract Flashcards

1
Q

What are the 3 key processes in digestion

A

Mechanical digestion, chemical digestion and microbial digestion

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2
Q

What is the mechanical digestion

A

Digestion via mastication and muscular movements from mouth to anus

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3
Q

What is chemical digestion

A

Hydrolysis by enzymes

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4
Q

What is microbial digestion

A

Digestion via enzyme produced by gut microorganisms in colon

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5
Q

What is the gross structure of the GI tract

A
  • muscular tube with central lumen, with 4 major layers
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6
Q

What are the 4 major layers of the digestive tract

A

Mucosa, submuscisa, muscularis externa and serosa

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7
Q

What is the Mucosa layer

A

Epithelial cells

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8
Q

What is the submucosa

A

Connective tissue beneath mucosa containing large blood vessels, lymphatic vessels and exocrine glands

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9
Q

What is the muscularis externa

A

Layer beneath submucosa that is dominated by smooth muscle in two layers (circular layer and longitudinal layer) involved in mechanical processing of molecules

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10
Q

What is the serosa

A

Layer of visceral peritoneum that covers muscularis externa, dense network of collagen fibres that firmly attaches digestive tract to adjacent structures

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11
Q

How many pairs of salivary glands are there in the mouth

A

3

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12
Q

What regulate saliva production in the mouth

A

Acetylcholine secretion/ parasympathetic stimulation

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13
Q

What enzymes are secreted by the salivary glands

A

Salivary alpha amylase and lingual lipase

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14
Q

Which salivary gland secretes salivary alpha amylase

A

Parotid gland

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15
Q

Which salivary gland secretes lingual lipase

A

Von ebners gland

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16
Q

What regulates the passage of food in the oesophagus

A

Epiglottis and cardiac sphincter

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17
Q

What is peristalsis

A

Rhythmic contraction of smooth muscle

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18
Q

Why is peristalsis important in the oesophagus

A

Ensures one way movement of food from mouth to stomach

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19
Q

What do chief cells secrete in the stomach

A

Gastric lipase and pepsinogen (zymogen)

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20
Q

What do parietal cells secrete in the stomach

A

Hydrogen and chloride ions (gastric acid as passively followed by water)

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21
Q

What regulates gastric acid secretion in the stomach

A

Histamine, gastric and acetylcholine

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22
Q

What is the gastric pit

A

Invagination in the stomach where specialised cells are located

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23
Q

What are the specialised cells in the stomach

A

Parietal cells, chief cells and G cells

24
Q

How is pepsinogen activated (into pepsin)

A

HCL secreted by parietal cells cleaves pepsinogen secreted by chief cells to pepsin (active form)

25
Q

What are the digestive accessory organs

A

The Liver and pancreas

26
Q

What stimulates the secretion of bile (liver) and pancreatic digestive enzymes (pancreas)

A

CCK and secretin

27
Q

What is the key function of the liver in digestion

A

Synthesis of bile salts from cholesterol

28
Q

What is the function of the gall bladder

A

Storage of bile acids

29
Q

What stimulates the release of CCK

A

Food entering the duodenum

30
Q

What two cells types are in the pancreas

A

Exocrine (enzymes) and endocrine (hormones)

31
Q

What are the cells in the pancreas that secrete digestive enzymes

A

Acinar cells

32
Q

What are the crypts of lieberkuhn

A

Intestinal crypts at base of villi in the small intestine

33
Q

What are CBC stem cells

A

Stem cells located at base of villi (crypts of lieberkuhn) that differentiate into specialised epithelial cells

34
Q

What are paneth cells

A

Specialised epithelial cells at base of villi that have immune function

35
Q

What are enterocytes

A

Specialised epithelial cells

36
Q

What are enteroendocrine cells

A

Specialised epithelial cells
that secrete hormones

37
Q

What are goblet cells

A

Specialised epithelial cells that secrete mucus

38
Q

What are tuft cells

A

Specialised epithelial cells with immune function

39
Q

What is the hepatic portal vein

A

Transports blood from GI tract, pancreas, gallbladder and spleen to liver to supply metabolic substrates and for detoxification of ingested toxins

40
Q

What is the caecum

A

Small pouch on the right side of ascending colon that is a reservoir for chyme

41
Q

What is the appendix

A

Tube like structure connected to caecum that is a reservoir for beneficial gut bacteria to repopulate gut flora and immune system

42
Q

What is the Ilecocaecal valve

A

Valve separating small and large intestine

43
Q

What are the three main components of the large intestine

A

Ascending, transverse and descending colon

44
Q

What are the three components of the small intestine

A

Duodenum, jejunum and ileum

45
Q

What is the function of the large intestine

A

Microbial digestion of nutrients not digested and absorbed in the small intestine ( e.g. dietary fibre)

46
Q

What is the symbiotic relationship in the large intestine

A

We provide environment for growth and nutrients and gut microorganism facilitate digestion of beta bonds

47
Q

What is the rectum

A

Long chamber at the end of the descending colon that descending colon does

48
Q

What stimulates defaecation

A

Entry of stool into rectum

49
Q

What is the anus

A

Anal sphincter regulates stool leaving the body (egestion)

50
Q

What does the central core of chylomicrons contain

A

Triacylglycerides and cholesterol esters

51
Q

What does the outer membrane of chylomicrons contain

A

Phospholipid monolayer, free (unesterified) cholesterol and apoproteins

52
Q

How are lipids absorbed in the small intestine

A
  • bile salts from liver coat fat droplets and emulsify them
  • pancreatic lipase and co-lipase break down fats into monoglycerides and FA stored in micelles
    -monoglycerides and fatty acids move out of micelles and diffuse into epithelial cells, cholesterol is transported into cells
  • absorbed fats reassemble and combine with cholesterol and protein in chylomicrons
  • chylomicrons are removed by the lymphatic system
53
Q

What is the difference between the apical and basolateral membrane the epithelial cells of the small intestine

A

Apical- facing lumen of small intestine
Basolateral- facing hepatic portal vein

54
Q

How is glucose absorbed in the small intestine

A

-Na+ bind to SGLUT1 (sodium dependent glucose transporter) on apical membrane enabling glucose/galactose to bind and be cotransported into the entereocyte
- Glucose is transported out of cell to hepatic portal vein by GLUT2
-Sodium potassium pump actively transports Na+ out of cell by exchange with k+ (energy dependent)

55
Q

Why is fructose absorption not energy dependent

A

sodium independent GLUT5 transported transports fructose into cell instead of SGLUT1 so Na+/K+ pump not need

56
Q

How are amino acids absorbed in the small intestine

A

Na+ dependent AA transporter on apical membrane co transports AA with Na+ into cell
X Na+/K+ pump maintains Na+ concentration gradient (energy dependent)
Facillitative AA transfer on basolateral membrane transports AA to hepatic portal vein

57
Q

How are di and tripeptides absorbed in the small intestine

A
  • Hydrogen-dependent di- and tri-peptide transporter (PepT1) on apical membrane cotransports
  • energy dependent as Na+/ H+ pump (apical membrane) removes H+ from cell and then Na+/K+ pump (requires ATP) actively transports Na+ out of cell (basolateral membrane)
  • Intracellular peptidases hydrolyse do and tripeptides → amino acids
    -Facilitative amino acid transporter on basolateral
    membrane, AA enter hepatic portal vein

NUT1005 (18 decks)

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