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Gastrointestinal > Intro to Functions of Alimentary Tract > Flashcards

Intro to Functions of Alimentary Tract Flashcards

1
Q

What is the gastrointestinal tract?

A

The main organs of the digestive system form the gastrointestinal (GI) tract to create an open tube that runs from the mouth to the anus

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2
Q

What passes through the GI tract?

A

Everything we eat is processed through the GI tract

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3
Q

What is the role of the digestive system?

A

The digestive system:

  • prepares ingested nutrients for digestion & absorption
  • protects against consumed micro organisms and toxins
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4
Q

What processes occur to ensure the functions of the digestive system are carried out?

A
  • ingestion
  • digestion
  • absorption
  • elimination
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5
Q

What do the processes of the GI tract depend upon?

A

The processes occurring in the GI tract depend upon the motility / movement of the GI tract and the digestive juices & enzymes secretions

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6
Q

What are the functions of the digestive tract?

A

Accommodation & Storage
Mechanical & enzymatic breakdown
Slow delivery of chyme to duodenum

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7
Q

What does the pancreas secrete?

A

a bicarbonate rich solution

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8
Q

How does the stomach accommodate storage during digestion?

A

Food stored during the first stage of digestion may remain in the stomach for ~1 hr unmixed - acts as a reservoir

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9
Q

Explain how the fundus is adapted to aid storage of food in the stomach?

A

The fundus and body of the stomach have thinner muscle tone which relax to allow a larger volume (~1.5 L) of food storage

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10
Q

What is the role of vagal reflex in storage of food?

A

Vagal reflex inhibits smooth muscle tone - mechanoceptors cause fundic relaxation via VIP/NO

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11
Q

What is the role of the antrum in storing food in the stomach?

A

The antral region mixes / grinds food with gastric secretions enabling digestion

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12
Q

What is the role of the colon / rectum?

A

Storage of indigestive residues and faecal matter

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13
Q

Where are gastric secretions stored?

A

The stomach stores 2-3 Litres of gastric juices every 24 hrs

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14
Q

What does gastric juice consist of?

A

mucus
pepsinogen
intrinsic factor
lipase

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15
Q

What is the role of gastric secretions?

A

Aid in digestion and food absorption

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16
Q

Where is mucus secreted from?

A

Goblet cells and mucus neck cells

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17
Q

What is the role of mucus?

A

Acts as a lubricant by acting as a barrier to protect the stomach and colon esp. from gastric acid
- prevents trauma

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18
Q

What is the role of lipase?

A

converts TG → FA + glycerol

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19
Q

Where is pepsin scereted from?

A

Secreted by chief cells / peptic cells as the precursor pespinogen

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20
Q

What is the role of pepsin?

A

protein digestion

21
Q

Where is HCl secreted from?

A

Parietal cells

22
Q

What is the role of HCl?

A

important in defence and converts pepsinogen →pepsin

23
Q

Which cells secrete Intrinsic factor (IF)?

A

parietal cells

24
Q

What is the role of Intrinsic Factor?

A

aids vitamin B12 absorption

25
Q

Describe features of paracrine secretions

A

local hormones
secreted from cells in mucosa
Chemicals act locally on adjacent cells via interstitial fluid

26
Q

Give an example of a paracrine secretion

A

somatostatin - inhibits gastrin release in stomach

27
Q

What is the role of gastrin?

A

Controls parietal cell acid secretion

28
Q

Where are exocrine secretions from?

A

Salivary glands
Gastric glands
Liver
Pancreas

29
Q

What exocrine secretions are produced in the salivary glands?

A

Mucus; lubrication for mastication and speech

Lipase

30
Q

What does the exocrine pancreas secrete?

A

Bicarbonate ions

Enzymes; amylase, lipase, carboxypeptidase

31
Q

What exocrine secretions are produced by the gastric glands?

A

HCl, pepsin, mucus

32
Q

What does the exocrine liver secrete?

A

bile salts and bile acids

33
Q

What is the role of exocrine secretions?

A

Secretions from numerous glands with ducts enter lumen of the gut and are involved in digestion, lubrication and protection

34
Q

What is carboxypeptidase?

A

Protease enzyme that hydrolyses a peptide bond at the carboxy-terminal (C-terminal) end of a peptide/protein

35
Q

What is amylase?

A

hydrolyses starch -> sugars

36
Q

What are endocrine secretions?

A

Hormones synthesised by ductless glands

37
Q

How do endocrine secretions achieve their effect?

A

Enter bloodstream to travel to their target tissue(s) where they bind to specific receptors to elicit their effects

38
Q

Name endocrine secretions and where they’re secreted

A

Gastrin - stomach (G cells in antrum)

Secretin - duodenal mucosa

pancreozymin-CCK - duodenal mucosa

Insulin - pancreatic beta Cell

39
Q

How is food made of use to the body?

A

Nutrients resulting from digestion must be transported across the intestinal epithelium into the blood
e.g. glucose, amino acids
or, lymph via lacteals (fats/lipids)

40
Q

Where does absorption of food occur?

A

absorption occurs mainly in small intestine

41
Q

Where is fluid mostly absorbed?

A

Absorption of fluid occurs in the small intestine and colon

- colon absorbs 90% water

42
Q

Where is digested food predominantly stored before excretion?

A

proximal stomach and descending colon

43
Q

How does motility of food occur in the GI tract?

A

Movement of muscular wall (mostly smooth muscle except extreme ends of the upper oesophagus / rectum)

44
Q

What is the significance of gut motility?

A

Allows:
- movement from one region to another; mass of
evacuation
- Mechanical degradation (gastric antrum)
- Mixing lumen contents e.g. small intestine
- Transport of nutrients, water and of urea and
electrolytes
- Digestion and absorption

45
Q

How are drugs and metabolism excreted?

A

Drugs and some products of normal metabolism may leave the body in:

  • saliva
  • bile
  • faeces
  • vomit

Indigestible food residues (e.g. tomato skin) leave the body via the faeces

46
Q

What is the significance of the gut epithelium in defence?

A

If there is a breach in the barrier ‘toxins’ will enter the blood
it’s largest lympho-epithelial organ and mucosal surface
Is exposed to the heaviest burden of environmental antigens

47
Q

How is the gut protected from the external environment?

A
  • Sight, smell and taste alerts us to harmful food
    substances
  • vomit reflex
  • HCl in stomach kills bacteria
  • Mucus secretions
  • Natural bacteria flora prevents harmful bacteria
    colonisation
  • Lymphoid tissue aggregation; react to food borne
    antigens
  • Peyer’s patches in lamina propria
48
Q

Where are the metabolic functions of the gut carried out?

A

In the liver
- involved in carbohydrate, nitrogen and lipoprotein
metabolism
- produces bile and excretes bilirubin

49
Q

Outline the functions and mechanisms of the GI tract

A
  1. Storage
  2. Paracrine secretions
  3. Exocrine secretions
  4. Endocrine secretions
  5. Absorption
  6. Motility / transport
  7. Excretion / transport
  8. Defence
  9. Metabolism

Gastrointestinal (18 decks)

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