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

Overview of Gastrointestinal Function Flashcards

1
Q

What do metabolic processes need?

A

A specific range of small molecule

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2
Q

What does food have?

A

A wide range of mostly large molecules

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3
Q

What is the problem with food?

A

The large molecules are locked into complex structures

It may be contaminated with pathogens

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4
Q

What does digestion do to food?

A

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

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5
Q

What can happen once food has been digested?

A

It is now ready for absorption and excretion

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6
Q

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

A
  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
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7
Q

What are the regions of the GI tract?

A
  • Mouth and Oesophagus
  • Stomach
  • Duodenum
  • Small intestine
  • Large intestine
  • Rectum
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8
Q

What are the functions of the mouth and oesophagus?

A
  • Mastication
  • Saliva
  • Swallowing
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9
Q

What is the purpose of saliva?

A
  • Protects mouth
  • Lubricates food for mastication and swallowing
  • Starts digestion
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10
Q

How does saliva protect the mouth?

A
  • Wets
  • Bacteriostatic
  • Alkaline
  • High Ca2+
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11
Q

How does saliva lubricate food?

A
  • Wet
  • Mucus
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12
Q

What does the saliva digest?

A

Sugars

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13
Q

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

A
  • Formation of bolus
  • Rapid oesophageal transport
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14
Q

What is the function of the stomach?

A
  • Storage
  • Initial disruption
  • Delivers Chyme slowly into duodenum
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15
Q

How does the stomach acheive it’s storage function?

A

It relaxes to accommodate food

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16
Q

How does the stomach acheive initial disruption?

A
  • Contracts rhythmically to mix and disrupt
  • Secretes acid and proteolytic enzymes to break down tissues and disinfect
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17
Q

What happens once stomach has performed initial disruption of food?

A

The food is now called Chyme

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18
Q

What is the function of the duodenum?

A

Dilation and neutralisation of Chyme

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19
Q

How does the duodenum dilate and neutralise Chyme?

A
  • 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
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20
Q

What is the function of the small intestine?

A
  • Absorption of nutrients and electrolytes
  • Absorbs the majority of water
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21
Q

How does the small intestine absorb nutrients and electrolytes?

A
  • Fluid passes very slowly through the small intestine
  • Large surface area
  • Epithelial cells absorb molecules
  • Pass into hepatic portal circulation
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22
Q

How do epithelial cells absorb molecules?

A

Some actively, some passive

Often coupled to Na+ transport

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23
Q

How much water does the small intestine absorbed?

Compare to large intestine

A

1.5L

Compared to 0.15L in large intestine

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24
Q

What is the function of the large intestine?

A
  • Final absorption of water
  • Faeces form and accumulate
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25
Q

How fast is transit in the large intestine?

A

Very slow

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26
Q

Where does faeces form and accumulate in the large intestine?

A

In the descending and sigmoid colon

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27
Q

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

A

It is propelled periodically into the rectum

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28
Q

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

A

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

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29
Q

Label this diagram of the alimentary canal

A
  • 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
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30
Q

What does the alimentary canal consist of?

From the oval cavity to the anus

A

Four layers

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31
Q

What are the 4 layers of the alimentary canal?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis Externa
  4. Serosa/Adventita
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32
Q

What does the alimentary mucosa consist of?

A
  • Surface epithelia
  • Lamina propria
  • Muscle layer
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33
Q

What does the alimentary submucosa consist of?

A

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

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34
Q

What does the alimentary Muscularis Externa consist of?

A

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

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35
Q

What does the alimentary serosa/adventitia consist of?

A

A thin outer covering of connective tissue

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36
Q

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

A

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

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37
Q

How much food do we ingest per day?

A

About 1kg

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38
Q

How much liquid do we ingest per day?

A

About a litre

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39
Q

What is food mixed with?

A

1.5L of saliva and about 2.5L of gastric secretions

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40
Q

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

A

Chyme

41
Q

What are the characteristics of Chyme?

A
  • It is very hypertonic (has a high osmotic strength)
  • Very acidic
42
Q

What happens when Chyme is slowly released from the stomach?

A

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

43
Q

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

A

~12.5L

44
Q

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

A

~1.35L

45
Q

What is the enteric nervous system?

A

A subdivision of the autonomic nervous system

46
Q

What does the enteric nervous system do?

A

Directly controls the GI system

47
Q

What is the enteric nervous system made up of?

A

Two nerve plexuses

48
Q

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

A

In the wall of the gut

49
Q

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

A

Yes, in the short reflex pathway

50
Q

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

A

By both branches of the ANS (long reflex pathway)

Parasympathetic control is most significant

51
Q

What is the role of the enteric nervous system?

A

Coordinates secretion and motility

52
Q

How does the enteric nervous system perform its coordination role?

A

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

53
Q

Where are the endocrine cells of the alimentary canal found?

A

In the walls of the gut

54
Q

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

A

A dozen or more peptide hormones

55
Q

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

A

Both endocrine and paracrine

56
Q

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

A

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

57
Q

What is the function of the hormones of the gut?

A

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

58
Q

Give 18 common disease processes affecting the gut

A
  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
Q

What is dysphagia?

A

Difficulty swallowing

60
Q

What may cause dysphagia?

A
  • Problems with the oesophagus
  • Neurological
61
Q

What problems of the oesophagus can cause dysphagia?

A
  • Musculutare
  • Obstruction by tumour
62
Q

What neurological problems can cause difficulty swallowing?

A

Stroke

63
Q

What are the tumours of the oesophagus called?

A
  • High up are squamous cell carcinoma
  • Lower down are adenocarcinomas
64
Q

What are the symptoms of acid reflux?

A
  • Irritation
  • Pain (heartburn)
65
Q

What causes acid reflux?

A

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

66
Q

What is Barrett’s Oesophagus?

A

Metaplasia of the lower oesophageal squamous epithelium to gastric columnar

67
Q

What causes Barrett’s Oesophagus?

A

It is a protective mechanism against acid reflux

68
Q

What is Oesophageal Varices?

A

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

69
Q

What causes Oesophageal Varices?

A

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

70
Q

What is peptic ulceration?

A

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

71
Q

What is peptic ulceration due to?

A

Irritation from gastric acid

72
Q

What is pancreatitis?

A

Inflamed pancreas

73
Q

What are the symptoms of pancreatitis?

A

Considerable pain

74
Q

What is pancreatitis characterised by?

A

The release of amylases into the blood stream

75
Q

What causes jaundice?

A

Liver cannot excrete bilirubin, which accumulates in the blood.

76
Q

What are the types of jaundice?

A
  • Pre-hepatic jaundice
  • Post-hepatic/obstructive jaundice
77
Q

What is pre-hepatic jaundice?

A

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

78
Q

What is post-hepatic/obstructive jaundice?

A

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

79
Q

What forms gallstones?

A

Precipitatin of bile acids and cholesterol in the bladder

80
Q

What are the consequences of gallstones?

A

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

81
Q

What may mimic the effects of gallstones?

A

Tumours of the pancreas may also obstruct outflow

82
Q

What is malabsorption?

A

Several conditions that affect how well the intestines can absorb things

83
Q

What is appendicitis?

A

Inflammation of the appendix

84
Q

How does appendicitis present?

A

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

85
Q

What is peritonitis?

A

Inflammation of the peritoneum

86
Q

Give two types of inflammatory bowel disease

A
  1. Ulcerative colitis
  2. Crohn’s disease
87
Q

How does acute blockage of the small intestines present?

A
  • Pain (in the back)
  • Vomiting
  • Bloating
88
Q

What are haemorrhoids?

A

Vascular structures in the anal canal that aid with stool control

89
Q

What is the clinical significance of haemorrhoids?

A

They may become swollen and inflamed

90
Q

What happens when haemorrhoids become swollen and inflamed?

A

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

91
Q

What is a prolapse?

A

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

92
Q

Give an example of a location that can prolapse

A

The rectum

93
Q

What is a diverticula?

A

An abnormal ‘outpouching’ in the colon to form a hollow

94
Q

What causes a diverticula?

A

Pressure being too high in the colon

95
Q

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

A

The sigmoid colon

96
Q

Why is the sigmoid colon most prone to a diverticula?

A

As the blood supply causes an area of weakness

97
Q

What is Meckels’ Diverticulum?

A

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

98
Q

What is the clinical significance of Meckels’ Diverticulum?

A

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

99
Q

What is the clinical significance of colo-rectal cancer?

A

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

ESA 3 - Gastrointestinal System (12 decks)

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