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GIT Physiology > Introduction to GIT Function > Flashcards

Introduction to GIT Function Flashcards

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Git Commands flashcards
1
Q

The digestive system consists of?

A
  1. neuronal and muscular tissues
  2. epithelia with absorptive and secretory functions 3. endocrine cells
  3. target cells for the gastrointestinal hormones
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2
Q

Name the 2 components of the digestive system?

A
  1. gastrointestinal tract 2. accessory digestive organs
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3
Q

Describe the course of the digestive system?

A

extends from mouth to anus - 9 m long

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4
Q

Name the organs of the GIT?

A
  1. oral cavity 2. pharynx 3. oesophagus 4. stomach 5. small intestine 6. large intestine
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5
Q

Name the accessory digestive organs?

A
  1. teeth 2. tongue 3. salivary glands 4. liver 5. gall bladder 6. pancreas
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6
Q

What are the 7 functions of the GIT?

A
  1. ingestion
  2. mechanical digestion and chemical digestion
  3. secretion
  4. absorption
  5. motility/peristalsis
  6. excretion
  7. immune and protective role of GIT
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7
Q

What is ingestion?

A

when materials enter the digestive tract via the mouth

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8
Q

Describe ingestion?

A

is an active process involving conscious choice and decision making

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9
Q

What is mechanical digestion?

A

physical manipulation and distortion through the actions of the teeth, tongue, and palatal surfaces

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10
Q

Describe mechanical digestion?

A

Tearing and crushing with teeth followed by squashing and compaction by the tongue (preliminary mechanical processing) - may or not be required before ingestion

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11
Q

What is the importance of mechanical digestion?

A
  1. make food easier to propel along the digestive tract

2. increases the surface area for enzymatic attack

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12
Q

What is chemical digestion?

A

chemical breakdown of food into small organic fragments suitable for absorption by the digestive epithelium

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13
Q

What is the purpose of chemical digestion?

A

to break down food into simple molecules - simple molecules in food such as glucose can be absorbed intact, but large molecules e.g. polysaccharides or triglycerides cannot be absorbed

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14
Q

What are the 2 types of secretions?

A
  1. endocrine 2. exocrine
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15
Q

Describe exocrine secretions?

A

the release of saliva, acids, digestive enzymes, buffers and salts by the epithelium of the digestive tract

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16
Q

Describe endocrine secretions?

A

secretion of hormones that regulate the digestive system

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17
Q

What is absorption?

A

The movement of organic substrates, electrolytes (inorganic ions), vitamins and water across the digestive epithelium into the interstitial fluid of the digestive tract

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18
Q

What is motility/peristalsis?

A

The rhythmic wavelike contractions of the smooth muscle of the intestines that move food through the GI tract.

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19
Q

What is excretion?

A

elimination of waste products from the body - The digestive tract and glandular organs secrete waste products in secretions discharged into the lumen of the tract

20
Q

Waste products are ejected through?

A

defecation/egestion

21
Q

Waste products are ejected as?

A

faeces - waste products + indegestable residue

22
Q

Describe the protective role of the lining of the GIT?

A
  1. Corrosive effects of the digestive acids and enzymes
  2. Mechanical stresses such as abrasion
  3. Bacteria that either is swallowed with food or reside inside the digestive tract
  4. Bacteria reaching the underlying tissues are attacked by macrophages and other cells of the immune system
23
Q

The activities of the digestive system are regulated by?

A

neural, hormonal and local mechanisms

24
Q

What is the nervous system of the GI tract?

A

enteric nervous system - 100 million neurons

25
Q

What does the enteric nervous system consist of?

A
  1. myenteric plexus 2. submucosal plexus
26
Q

Where is the myenteric plexus? (Auerbachs plexus)

A

lies between the longitudinal and circular muscles

27
Q

Function of the myenteric plexus?

A

controls mainly GI movements

28
Q

Where is the submucosal plexus? (Meissners plexus)

A

lies in the submucosa

29
Q

Function of the submucosal plexus?

A

regulates GI blood flow and epithelial cell function (local intestinal secretion and absorption)

30
Q

Nerve plexuses near the GI tract initiate what? (intrinsic)

A

short reflexes

31
Q

What are the extrinsic controls of the GI tract?

A
  1. sympathetic 2. parasympathetic 3. somatic
32
Q

Extrinsic controls initiate what?

A

long reflexes arising within or outside the GI tract

33
Q

What do motor neurons that terminate in the smooth muscle do?

A

stimulate contractions

34
Q

What do motor neurons that terminate on the intestinal crypts do?

A

stimulate salt and water secretion into lumen

35
Q

What does the parasympathetic nervous system do?

A

stimulates motility + secretions by the GI tract

36
Q

What does the sympathetic nervous system do?

A
  1. reduces peristalsis + secretory activity
  2. stimulate the contraction of sphincter muscles along the GI tract
    - inhibit GI functions
37
Q

What are the receptors of the GIT?

A
  1. mechanoreceptors 2. chemoreceptors
38
Q

What do these receptors of the GIT respond to?

A
  1. stretch
  2. presence of substrate
  3. osmolarity
  4. pH
  5. end product of digestion
39
Q

Receptors of the Git initiate reflexes that?

A
  1. activate or inhibit digestive glands

2. mix lumen contents and move them along

40
Q

Describe long reflexes?

A
  • provide a higher level of control that coordinates activities along the length of the digestive tract
  • generally control large scale peristaltic waves that move materials from one region of the digestive tract to another
  • may involve motor fibres in the glossopharyngeal, vagus, or pelvic nerves that synapse in the myenteric plexus
41
Q

How can neural commands be affected?

A

the sensitivity of the smooth muscle cells to neural commands can be enhanced or inhibited by digestive hormones

42
Q

Function of gastrin?

A

stimulates acid production

43
Q

Function of secretin?

A

stimulates pancreatic bicarbonate secretion

44
Q

Function of chlocystokinin?

A

stimulates gall bladder contractility

45
Q

Describe local/paracrine mechanisms?

A

prostaglandins, histamine and other chemicals released into the interstitial fluid affect cells within a small segment of the digestive system

46
Q

Function of these mechansims?

A

these local messengers are important in coordinating a response to conditions that affect a portion of the digestive tract (e.g. pH) - for example histamine in the lamina propria of the stomach stimulates secretion of acid by cells in the adjacent epithelium

GIT Physiology (5 decks)

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