Overview of Gastrointestinal Function Flashcards Preview

ESA 3 - Gastrointestinal System > Overview of Gastrointestinal Function > Flashcards

Flashcards in Overview of Gastrointestinal Function Deck (99):
1

What do metabolic processes need? 

A specific range of small molecule

2

What does food have? 

A wide range of mostly large molecules

3

What is the problem with food? 

The large molecules are locked into complex structures

It may be contaminated with pathogens

4

What does digestion do to food? 

Makes it into a sterile, neutral, and isotonic solution of small sugars, amino acids and small peptides, small particles of lipids, and other small molecules

5

What can happen once food has been digested? 

It is now ready for absorption and excretion 

6

Give the processes that occur in the GI tract, from eating food to excreting it

  1. Initial physical disruption 
  2. Ingestion and transport to storage
  3. Initial chemic disruption and creation of suspension (Chyme)
  4. Disinfection
  5. Controlled release of Chyme
  6. Diluration and neutralisation 
  7. Completion of chemical breakdown
  8. Absorption of nutrients and electrolytes
  9. Final absorption of water and electrolytes
  10. Producing faeces for controlled excretion

7

What are the regions of the GI tract? 

  • Mouth and Oesophagus
  • Stomach
  • Duodenum 
  • Small intestine 
  • Large intestine 
  • Rectum

8

What are the functions of the mouth and oesophagus? 

  • Mastication
  • Saliva
  • Swallowing

9

What is the purpose of saliva? 

  • Protects mouth
  • Lubricates food for mastication and swallowing
  • Starts digestion

10

How does saliva protect the mouth? 

  • Wets
  • Bacteriostatic
  • Alkaline
  • High Ca2+

11

How does saliva lubricate food? 

  • Wet
  • Mucus

12

What does the saliva digest?

Sugars

13

What is the function of the mouth and oesophagus in swallowing? 

  • Formation of bolus
  • Rapid oesophageal transport

14

What is the function of the stomach? 

  • Storage
  • Initial disruption 
  • Delivers Chyme slowly into duodenum 

15

How does the stomach acheive it's storage function? 

It relaxes to accommodate food 

16

How does the stomach acheive initial disruption? 

  • Contracts rhythmically to mix and disrupt
  • Secretes acid and proteolytic enzymes to break down tissues and disinfect 

17

What happens once stomach has performed initial disruption of food? 

The food is now called Chyme 

18

What is the function of the duodenum? 

Dilation and neutralisation of Chyme 

19

How does the duodenum dilate and neutralise Chyme? 

  • Water drawn in from ECF. The stomach is impermeable, the duodenum is permeable 
  • Alkali (bile) added from liver and pancreas
  • Enzymes added from pancreas and intestine

20

What is the function of the small intestine? 

  • Absorption of nutrients and electrolytes
  • Absorbs the majority of water 

21

How does the small intestine absorb nutrients and electrolytes?

  • Fluid passes very slowly through the small intestine
  • Large surface area
  • Epithelial cells absorb molecules 
  • Pass into hepatic portal circulation

22

How do epithelial cells absorb molecules?

Some actively, some passive

Often coupled to Natransport

23

How much water does the small intestine absorbed?

Compare to large intestine 

1.5L

Compared to 0.15L in large intestine

24

What is the function of the large intestine? 

  • Final absorption of water
  • Faeces form and accumulate 

25

How fast is transit in the large intestine? 

Very slow

26

Where does faeces form and accumulate in the large intestine? 

In the descending and sigmoid colon

27

What happens to faeces after formation and accumulation in the large intestines? 

It is propelled periodically into the rectum

28

What happens once the faeces has been propelled into the rectum? 

You get the urge to defecate, and there is controlled relaxation of sphincters and expulsion of faeces

29

Label this diagram of the alimentary canal

  • A - Salivary glands
    • ai - Parotid
    • aii - Submandibular
    • aiii - Sublingual 
  • B - Oral cavity
  • C- Pharynx
  • D - Tounge 
  • E - Oesophagus
  • F - Pancreas 
  • G - Stomach
  • H - Pancreatic duct
  • I - Ileum (small intestine)
  • J - Anus
  • K - Rectum
  • L - Appendix 
  • N - Cecum 
  • N - Colon 
    • ni- Transverse colon
    • nii- Ascending colon 
    • niii- Descending colon
  • O - Common bile duct
  • P - Duodenum 
  • Q- Gallbladder
  • R - Liver

30

What does the alimentary canal consist of? 

From the oval cavity to the anus

Four layers

31

What are the 4 layers of the alimentary canal? 

  1. Mucosa
  2. Submucosa
  3. Muscularis Externa
  4. Serosa/Adventita

32

What does the alimentary mucosa consist of? 

  • Surface epithelia 
  • Lamina propria
  • Muscle layer

33

What does the alimentary submucosa consist of? 

Fibroelastic tissue with vessels, nerves, leucocytes, and fat cells 

34

What does the alimentary Muscularis Externa consist of? 

Inner circular and outer longitudinal layer of smooth muscle, with the myenteric plexus lying between the layers 

35

What does the alimentary serosa/adventitia consist of? 

 A thin outer covering of connective tissue

36

What does the variation in cellular composition of alimentary layers do? 

Provides adaptations for specific functions, whilst remaining a continuous hollow tube of variable diameter and shape 

37

How much food do we ingest per day? 

About 1kg

38

How much liquid do we ingest per day? 

About a litre

39

What is food mixed with? 

1.5L of saliva and about 2.5L of gastric secretions

40

What is formed when food is mixed with saliva and gastric secretions? 

Chyme

41

What are the characteristics of Chyme? 

  • It is very hypertonic (has a high osmotic strength
  • Very acidic

42

What happens when Chyme is slowly released from the stomach? 

Around 9L of water and alkali moves into it from the ECF via osmosis

43

How much of the fluid from Chyme is absorbed by the small intestine 

~12.5L

44

How much of the fluid from Chyme is absorbed by the large intestine? 

~1.35L

45

What is the enteric nervous system? 

A subdivision of the autonomic nervous system 

46

What does the enteric nervous system do? 

Directly controls the GI system 

47

What is the enteric nervous system made up of? 

Two nerve plexuses

48

Where are the nerve plexuses that make up the enteric nervous system located? 

In the wall of the gut

49

Can the nerve plexuses that make up the enteric nervous system act independantly of the CNS? 

Yes, in the short reflex pathway

50

How can the activity of the enteric nervous system be modified? 

By both branches of the ANS (long reflex pathway)

Parasympathetic control is most significant

51

What is the role of the enteric nervous system? 

Coordinates secretion and motility 

52

How does the enteric nervous system perform its coordination role? 

Using a range of neurotransmitters, not just ACh as you may expect 

53

Where are the endocrine cells of the alimentary canal found? 

In the walls of the gut

54

What do the endocrine cells in the wall of the gut do? 

A dozen or more peptide hormones 

55

What kind of signalling do the hormones secreted by the wall of the gut use? 

Both endocrine and paracrine 

56

What do the hormones secreted by the wall of gut comprise? 

Two structurally related groups- the gastrin group and the secretin group 

57

What is the function of the hormones of the gut? 

Released from one part of the gut to affect the secretions or the motility of other parts

58

Give 18 common disease processes affecting the gut

  1. Dysphagia
  2. Acid reflux
  3. Barrett's Oesophagus 
  4. Oesophageal Varices 
  5. Peptic Ulceration 
  6. Pancreatitis 
  7. Jaundice
  8. Gallstones
  9. Malabsorption
  10. Appendicitis 
  11. Peritonitis 
  12. Inflammatory Bowel Disease
  13. Acute blockage of small intestines
  14. Haemorrhoids 
  15. Prolapse
  16. Diverticula
  17. Meckels' Diverticulum 
  18. Colorectal cancer 

59

What is dysphagia? 

Difficulty swallowing

60

What may cause dysphagia? 

  • Problems with the oesophagus 
  • Neurological 

61

What problems of the oesophagus can cause dysphagia?

  • Musculutare 
  • Obstruction by tumour 

62

What neurological problems can cause difficulty swallowing? 

Stroke

63

What are the tumours of the oesophagus called? 

  • High up are squamous cell carcinoma 
  • Lower down are adenocarcinomas

64

What are the symptoms of acid reflux? 

  • Irritation
  • Pain (heartburn)

65

What causes acid reflux? 

Sphincter between oesophagus and stomach is weak, and so acid refluxes into the oesophagus 

66

What is Barrett's Oesophagus? 

Metaplasia of the lower oesophageal squamous epithelium to gastric columnar

67

What causes Barrett's Oesophagus? 

It is a protective mechanism against acid reflux 

68

What is Oesophageal Varices? 

Dilation of sub-mucosal veins in the lower part of the oesophagus 

69

What causes Oesophageal Varices? 

The portal venous system is overloaded due to cirrhosis, and so blood is diverted to the oesophagus through connecting vessels

70

What is peptic ulceration? 

An area of damage to the inner mucosa of the stomach or duodenum

71

What is peptic ulceration due to? 

Irritation from gastric acid 

72

What is pancreatitis? 

Inflamed pancreas

73

What are the symptoms of pancreatitis? 

Considerable pain 

74

What is pancreatitis characterised by? 

The release of amylases into the blood stream

75

What causes jaundice? 

Liver cannot excrete bilirubin, which accumulates in the blood. 

76

What are the types of jaundice? 

  • Pre-hepatic jaundice
  • Post-hepatic/obstructive jaundice

77

What is pre-hepatic jaundice? 

If the build up of bilirubin is due to excess haemoglobin breakdown 

78

What is post-hepatic/obstructive jaundice? 

If build up of bilirubin is due to bile duct obstruction, and the back up of bile causes liver damage

79

What forms gallstones? 

Precipitatin of bile acids and cholesterol in the bladder

80

What are the consequences of gallstones? 

Often asymptomatic, but may move within the gall bladder causing painful biliary colic, or move to obstruct biliary outflow 

81

What may mimic the effects of gallstones? 

Tumours of the pancreas may also obstruct outflow 

82

What is malabsorption? 

Several conditions that affect how well the intestines can absorb things 

83

What is appendicitis? 

Inflammation of the appendix 

84

How does appendicitis present? 

As a sharp pain in the side at the same level as T10, which then localises to the right lower quadrant 

85

What is peritonitis? 

Inflammation of the peritoneum 

86

Give two types of inflammatory bowel disease

  1. Ulcerative colitis 
  2. Crohn's disease

87

How does acute blockage of the small intestines present? 

  • Pain (in the back)
  • Vomiting
  • Bloating 

88

What are haemorrhoids? 

Vascular structures in the anal canal that aid with stool control 

89

What is the clinical significance of haemorrhoids? 

They may become swollen and inflamed

90

What happens when haemorrhoids become swollen and inflamed? 

They are painful, itchy, and blood may be present in the stool 

91

What is a prolapse? 

A condition where the organs fall or slip down out of place 

92

Give an example of a location that can prolapse

The rectum 

93

What is a diverticula? 

An abnormal 'outpouching' in the colon to form a hollow

94

What causes a diverticula? 

Pressure being too high in the colon 

95

What portion of the colon is most prone to a diverticula? 

The sigmoid colon

96

Why is the sigmoid colon most prone to a diverticula? 

As the blood supply causes an area of weakness

 

97

What is Meckels' Diverticulum? 

A pouch in the lower part of the small intestine, a vestigal remnant of the yolk sac

98

What is the clinical significance of Meckels' Diverticulum? 

It can produce ectopic gastric mucosa, that may then produce gastric acid, causing irritation 

99

What is the clinical significance of colo-rectal cancer? 

The large intestine is a common site of malignancies, and colo-rectal cancer is a major cause of mortality