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3 - GI > deck_1295876 > Flashcards

deck_1295876 Flashcards

1
Q

What is the overall function of the gastrointestinal system?

A

• Secretion• Digestion• Motility• Absorption

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2
Q

What are the qualities of the products of digestion?

A

• Sterile• Neutral• Isotonic

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3
Q

What solutions does the process of digestion create?

A

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

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4
Q

Define absorption

A

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

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5
Q

Give three waste products of the GI tract

A

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

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6
Q

What needs to happen to food for digestion to occur?

A

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

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7
Q

Why do ingested foods need to be stored?

A

• We can eat much faster than we can digest

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8
Q

Outline the overall process of digestion

A

• 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

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9
Q

List the two mechanisms involved in physical disruption of food

A

MasticationSaliva

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10
Q

Outline the functions of saliva

A

• Protects mouth• Lubricates food• Starts digestion

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11
Q

Give four ways in which saliva protects the mouth

A

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

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12
Q

What does saliva initially digest?

A

• Sugars

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13
Q

What is food called after it has been physically disrupted?

A

• Bolus

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14
Q

Where does storage, initial disruption and disinfection take place?

A

Stomach

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15
Q

How is chyme produced in the stomach?

A

• Action of acid, enzymes and agitation

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16
Q

Where does dilution and neutralisation of chyme take place?

A

• Duodenum and jejunum

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17
Q

Why does dilution take place?

A

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

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18
Q

What do enzymes from pancreas and intestine do?

A

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

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19
Q

How does absorption of nutrients and electrolytes take place?

A

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

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20
Q

What are absorbed nutrients taken into?

A

• Hepatic portal circulation

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21
Q

Where does final absorption of water and electrolytes occur?

A

• Large intestine

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22
Q

Where does faeces accumulate?

A

• Descending and sigmoid colon

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23
Q

How does defecation occur?

A

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

24
Q

What is the function of the stomach?

A

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

25
Q

Outline the process of receptive relaxation

A

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

26
Q

What takes place in the duodenum and jejunum?

A

• 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
Q

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

A

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

28
Q

Outline the four layers of alimentary canal

A

• Mucous membrane• Submucosa• Muscularis externae• Serosa

29
Q

What makes up the mucous membrane?

A

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

30
Q

What makes up the submucosa?

A

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

31
Q

What makes up the muscularis externa?

A

An inner circular layerOuter longitudinal layer

32
Q

What lies between the two layers of the muscularis externae?

A

• Myenteric plexus

33
Q

What is the serosa?

A

• A thin outer covering of connective tissue

34
Q

What is endoscopy?

A

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

35
Q

What is nasendoscopy?

A

• Allows visualisation of the nose, mouth and pharynx

36
Q

What structure marks the beginning of the oesophagus?

A

• Cricopharyngeal sphincter

37
Q

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

A

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

38
Q

Outline the venous drainage of the oesophagus

A

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

39
Q

How is the oesophagus adapted to rapid transport?

A

• Streamlined structure which minimises friction

40
Q

What are the longitudinal ridges of the stomach called?

A

• Rugae, increase SA

41
Q

Where is gastric ulceration most common?

A

• Lesser curve at the angulus

42
Q

What is the normal maximal fluid contents of the gut?

A

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

43
Q

How are the contents of the gut removed?

A

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

44
Q

What happens if the balance between secretion and absorption altered?

A

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

45
Q

Name three control systems of the gut

A

• Neural• Paracrine• Endocrine

46
Q

Why are three overlapping control systems needed in the gut?

A

• Motility and secretion need precise control

47
Q

What is the somatic motor used for in the gut?

A

• Ingestion (chewing) and excretion (defecation)

48
Q

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

A

• Autonomic (specifically parasympathetic) control

49
Q

What do post ganglionic neurones form in the gut?

A

• Plexuses

50
Q

What does the “gut nervous system” control?

A

• Coordinates secretion and motility

51
Q

What enteric nervous system of the gut made up of?

A

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

52
Q

What is paracrine secretion?

A

• Chemical messengers diffuse locally

53
Q

Name a chemical messenger secreted via the paracrine method

A

Histamine

54
Q

Give three factors the endocrine system controls in the digestive system

A

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

55
Q

What type of structure do gut hormones share?

A

• All peptide derived

56
Q

What are the two groups of gut hormones?

A

• Gastrin group• Secretin group

3 - GI (36 decks)

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