Session 1 - Introduction to the GI system Flashcards Preview

Semester 3 - Gastrointestinal > Session 1 - Introduction to the GI system > Flashcards

Flashcards in Session 1 - Introduction to the GI system Deck (56):
1

What is the overall function of the gastrointestinal system?

• Secretion
• Digestion
• Motility
• Absorption

2

What are the qualities of the products of digestion?

• Sterile
• Neutral
• Isotonic

3

What solutions does the process of digestion create?

• Small sugars
• Amino acid and small peptides
• Lipids in very small particles

4

Define absorption

• Specific active or passive uptake of nutrient molecules, water and electrolytes

5

Give three waste products of the GI tract

• Residue from food
• Gut debris
• Materials secreted from liver

6

What needs to happen to food for digestion to occur?

• Disrupted physically to release large molecules
• Broken down chemically to release small molecules

7

Why do ingested foods need to be stored?

• We can eat much faster than we can digest

8

Outline the overall process of digestion

• Initial physical disruption
• Ingestion & transport to storage
• Initial chemical disruption & creation of suspension – forming chyme
• Disinfection
• Controlled release of chyme
• Dilution and neutralisation of chyme
• Completion of chemical breakdown
• Absorption of nutrients and electrolytes
• Final absorption of water and electrolytes,
• Producing faeces for controlled excretion

9

List the two mechanisms involved in physical disruption of food

Mastication
Saliva

10

Outline the functions of saliva

• Protects mouth
• Lubricates food
• Starts digestion

11

Give four ways in which saliva protects the mouth

• Wet - maintains mucosae
• Bacteriostatic
• Alkaline - protects teeth
• High calcium - protects teeth

12

What does saliva initially digest?

• Sugars

13

What is food called after it has been physically disrupted?

• Bolus

14

Where does storage, initial disruption and disinfection take place?

Stomach

15

How is chyme produced in the stomach?

• Action of acid, enzymes and agitation

16

Where does dilution and neutralisation of chyme take place?

• Duodenum and jejunum

17

Why does dilution take place?

• To ensure that the chyme is of the same osmotic potential as the small intestine

18

What do enzymes from pancreas and intestine do?

• Cleave peptides to amino acids
• Cleave polysaccharides to monosaccharaides
• Breakdown and re-form lipids
• Break down nucleic acids

19

How does absorption of nutrients and electrolytes take place?

• Intestine has large SA due to brush border
• Epithelial cells absorb small molecules - some actively, some passively
• Often coupled to sodium absorption

20

What are absorbed nutrients taken into?

• Hepatic portal circulation

21

Where does final absorption of water and electrolytes occur?

• Large intestine

22

Where does faeces accumulate?

• Descending and sigmoid colon

23

How does defecation occur?

• Faeces propelled into rectum
• Controlled relaxation of sphincters and expulsion of faeces occurs

24

What is the function of the stomach?

• Relaxes to accommodate food
• Rhythmical contraction
• Secretes acid and proteolytic enzymes to break down tissues
• Disinfects bolus

25

Outline the process of receptive relaxation

• Stomach strongly contracted between meals
• Relaxes as bolus enters
• Prevents a rise in pressure of the stomach

26

What takes place in the duodenum and jejunum?

• Water drawn in from ECF
• Bile added to chyme
• Pancreas, liver and intestinal secretions (enzymes and bile acids)
• Liver and pancreas secrete alkali and neutralise acid

27

How is duodenum adapted to the highly concentrated chyme it receives from the stomach?

• Wall permeable to water
• Draws water in to dilute contents

28

Outline the four layers of alimentary canal

• Mucous membrane
• Submucosa
• Muscularis externae
• Serosa

29

What makes up the mucous membrane?

• Lining epithelium
• Connective tissue
• Thin layer of smooth muscle

30

What makes up the submucosa?

• Fibroelastic tissue with
• Vessels
• Nerves of the submucosal plexus
• Leucocytes
• Fat cells

31

What makes up the muscularis externa?

An inner circular layer
Outer longitudinal layer

32

What lies between the two layers of the muscularis externae?

• Myenteric plexus

33

What is the serosa?

• A thin outer covering of connective tissue

34

What is endoscopy?

• A long, thing tube which allows direct visual examination, biopsy sampling and therapeutic treatment of the gastro-intestinal tract

35

What is nasendoscopy?

• Allows visualisation of the nose, mouth and pharynx

36

What structure marks the beginning of the oesophagus?

• Cricopharyngeal sphincter

37

Where does the diaphragm cuff the oesophagus, and why is this clinically relevant?

• At the oesophagogastric mucosal junction
• This relationship may be disrupted by a hiatus hernia, which allows the stomach to herniate into the thorax

38

Outline the venous drainage of the oesophagus

• Drains into the left portal system via the left gastric vein

39

How is the oesophagus adapted to rapid transport?

• Streamlined structure which minimises friction

40

What are the longitudinal ridges of the stomach called?

• Rugae, increase SA

41

Where is gastric ulceration most common?

• Lesser curve at the angulus

42

What is the normal maximal fluid contents of the gut?

• 14L
• 1kg food, 1.5L saliva, 2.5L gastric secretions, 9l of water and alkali

43

How are the contents of the gut removed?

• Small intestine absorbs 12.5l
• Large intestine absorbs 1.35
• 150g faeces expelled

44

What happens if the balance between secretion and absorption altered?

• Considerable loss of water and electrolytes, mostly from body fluids
• Rapid dehydration and electrolyte disturbance

45

Name three control systems of the gut

• Neural
• Paracrine
• Endocrine

46

Why are three overlapping control systems needed in the gut?

• Motility and secretion need precise control

47

What is the somatic motor used for in the gut?

• Ingestion (chewing) and excretion (defecation)

48

What is the most significant neural control system of the gut?

• Autonomic (specifically parasympathetic) control

49

What do post ganglionic neurones form in the gut?

• Plexuses

50

What does the "gut nervous system" control?

• Coordinates secretion and motility

51

What enteric nervous system of the gut made up of?

• Two nerve plexuses which may act independently of CNS and be modified by both branches of the ANS

52

What is paracrine secretion?

• Chemical messengers diffuse locally

53

Name a chemical messenger secreted via the paracrine method

Histamine

54

Give three factors the endocrine system controls in the digestive system

• Stomach acid
• Alkali secretion from liver and pancreas
• Enzyme secretion

55

What type of structure do gut hormones share?

• All peptide derived

56

What are the two groups of gut hormones?

• Gastrin group
• Secretin group