The Digestive System Flashcards Preview

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Flashcards in The Digestive System Deck (69):
1

Name the structures of the alimentary canal (GI tract) from mouth to anus.

Mouth
Tongue
Pharynx
Oesophagus
Stomach
Small intestine
Colon of large intestine
Appendix
Rectum
Anus

2

What are some accessory organs of the digestive system?

Salivary glands
Pancreas
Liver
Gall bladder

3

What are the 4 layers of the gut wall?

Mucosa
Submucosa
Muscularis externae
Serosa

4

What is the structure of the mucosa of the gut?

Epithelium
Lamina propria
Muscularis mucosae

5

What is the lamina propria?

Middle layer of the mucosa
Layer of connective tissue with peyer's patches/mucosal glands

6

What is the structure of the submucosa layer of the gut wall?

Connective tissue with vessels, veins and glands

7

What is the structure of the muscularis externae of the gut wall?

2 layers of smooth muscle
Inner circular layer
Outer longitudinal layer

8

What is the structure of the serosa layer of the gut wall?

Serous membrane
Mesothelium + thin layer of CT

9

What is mesothelium?

The simple squamous epithelium found in serous membranes

10

What is the function of the muscularis externae?

Contracts to create successive peristaltic waves - moving contents of lumen along the gut

11

What is digestion?

The conversion of what we eat into a solution from which we absorb our nutrients

12

What are some functions of the GI tract?

Provides a port of entry for food into the body
Mechanical disruption of the food
Chemical digestion of the food
Kills pathogens in the food
Nutrients absorbed
Waste eliminated

13

What enzymes does saliva contain, what are the functions of these?

Amylase, lipase - to begin chemical digestion of the food

14

What are the bacteriostatic features of saliva?

Contains IgA

15

Where is IgA secreted?

Throughout the GI tract

16

What are some features of saliva?

High in calcium (protecting the teeth)
Bacteriostatic (IgA)
Contains digestive enzymes
Alkaline
Assists in swallowing
Protects the mouth

17

What is a bolus?

Circular mass of food

18

Where does the bolus move once it has been formed in the mouth?

Oesophagus

19

What muscle is present in the oesophagus?

Upper end (voluntary) - contains skeletal muscle
Lower end (involuntary) - contains smooth muscle

20

What is the structure of the wall of the oesophagus?

Same as normal gut wall layer but NO serosa --> adventitia (connective tissue) instead

21

Why does the oesophagus not contain serosa in its wall?

It is not surrounded by a serous membrane and is outside the peritoneum

22

What innervation is found in the walls of the gut?

Submucosal plexus (found between submucosa and muscle)
Myentric plexus (found between external layers of muscle)

23

How is food physically disrupted in the stomach?

By churning

24

How is food chemically disrupted in the stomach?

Digestion by HCl and pepsin (enzyme)

25

In what way does the stomach contract?

Rhythmically

26

What epithelium is found in the oesophagus?

Stratified squamous epithelium

27

What does the stomach produce that passes to the duodenum of the small intestine?

Hypertonic chyme

28

What is chyme?

Produced in the stomach, partially digested food and gastric juices that pass to the duodenum

29

What epithelium is found in the GI tract (excluding the oesophagus)?

Simple columnar

30

What does the mucosa secrete in the stomach?

Acid, enzymes and the hormone GASTRIN

31

What is the structure of the wall of the stomach?

Same as usual with its 4 layers EXCEPT

Muscularis externae contains 3 layers of smooth muscle
(Oblique, circular and longitudinal)

32

What are rugae? Where do they exist?

Folds of mucosa forming ridges

In the stomach

33

Where are surface mucous cells found? What is their function?

In the gastric pits in the stomach

Secretes mucus in response to distension

34

What are some features of mucus?

Is resistant to pepsin
Contains HCO3- which neutralises the H+ protecting the stomach lining

35

What sort of cell renewal do surface mucous cells show?

Quickly divide by mitosis if damaged by aspirin/alcohol

36

What is the position and shape of the duodenum in the body?

Start of the small intestine
C shaped
Curved around the head of the pancreas

37

Which organs does the duodenum connect with?

Pancreas
Liver

38

What structure secretes mucus in the duodenum?

Brunner's glands

39

What mixture does the duodenum receive from the stomach?

Acid chyme

40

What is the function of the duodenum?

To neutralise and dilute the chyme

41

What does the duodenum receive from the pancreas?

Pancreatic juices

42

What does the duodenum receive from the liver?

Bile (via the gallbladder)

43

How is chyme neutralised in the duodenum?

Bile is alkali
Alkali secretions from the pancreas/liver

44

How is chyme diluted in the duodenum?

Water drawn in from extracellular fluid

45

The pancreas, liver and intestine secrete specific _____ to complete digestion of chyme

Enzymes

46

What does absorption of nutrients from solution require?

Large surface area
Adequate contact time
Energy - is an active process
Good blood supply/drainage

47

What is the surface area found in the small intestine?

Very large due to folding

48

What is the structure of the jejunal wall?

Same + mucosa contains microvilli

49

What are pilcae circulares?

Long extensions of the mucosa/villi found in the jejunum

50

What parts does the small intestine consist of?

Duodenum
Jejunum
Ileum

51

What nutrients does the duodenum absorb?

Iron

52

What nutrients does the jejunum absorb?

Sugars, amino acids and fatty acids

53

What nutrients does the ileum absorb?

Vitamin B12, bile acids and remaining nutrients

54

By the time the contents of the small intestine pass to the colon of the large intestine, what has been absorbed and what still needs to be absorbed?

Nutrients have been absorbed
Water needs to be absorbed

55

What are the different parts of the large intestine?

Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anus

56

What is the structure of the wall of the large intestine?

Same 4 layers as normal
Mucosa form numerous Krypts of Lieberkuhn

57

What is absorbed in the large intestine? And by which cells?

Water and electrolytes

Surface epithelial cells

58

What mixture exits in the lumen of the large intestine once it has passed through?

A semi-solid content that awaits expulsion

59

Where is most of the bacteria in the GI tract found? How is most of it lost?

In the colon

In faeces

60

What is bacteria in the colon useful for?

Synthesis of vitamin K, B12, thiamine, riboflavin

Breakdown of bilirubin and bile acids

61

By which 3 methods is the gut controlled?

Endocrine control
Paracrine control
Neural

62

What is an example of paracrine control in the gut?

Release of histamine - controls production of acid in the stomach

Vasoactive substances affecting blood flow in the gut

63

What are some examples of neural control in the gut?

Control of ingestion and excretion due to skeletal muscle
Autonomic nervous system controls the rest

64

Generally the gut is controlled by hormones made in the _____

Gut

65

What is the function of secretin in the gut?

Hormone

Promotes HCO3- secretion from duct cells of pancreas
Promotes production of bile in liver
Inhibits acid secretion by parietal cells of the stomach

66

Where is cholecystokinin (CCK) produced/secreted?

Enteroendocrine cells of the duodenum

67

What is the function of CCK in the gut?

Promotes bile release from gallbladder
Promotes digestive enzyme release from pancreas
Acts as a hunger suppressant

68

Where is gastrin released and by which cells?

G cells of the stomach, pancreas and duodenum

69

What is the function of gastrin?

Promotes production of HCl by parietal cells of the stomach