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Digestive system and renal biology > GI tract > Flashcards

GI tract Flashcards

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1
Q

What are the organs that makeup the GI tract ?

A
  • mouth
  • pharynx
  • salivary glands
  • oesophagus
  • stomach
  • pancreas
  • liver
  • gallbladder
  • small intestine
  • large intestine
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2
Q

What is meant by exocrine secretions ?

A

secretions out of the body

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3
Q

What is the exocrine secretions and functions of the mouth, pharynx and salivary glands ?

A
  • salt and water
  • mucus
  • amylase
  • chewing
  • swallowing reflex
  • moistens, lubricates and digests polysaccharides
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4
Q

What is the exocrine secretions and functions of the oesophagus ?

A
  • mucus
  • lubricates contents
  • peristaltic waves
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5
Q

What is the exocrine secretions and functions of the stomach ?

A
  • HCl
  • pepsin
  • mucus
  • food solubilisation
  • kills microbes
  • digests proteins
  • lubrication
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6
Q

What is the exocrine secretions and functions of the pancreas ?

A
  • enzymes
  • bicarbonate
  • digests carbohydrates, fats and proteins
  • neutralises HCl
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7
Q

What is the exocrine secretions and functions of the liver ?

A
  • bile salts
  • bicarbonate
  • organic waste products
  • solubilises water insoluble fats
  • neutralises HCl
  • elimination of waste
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8
Q

What is the exocrine secretions and functions of the gallbladder ?

A
  • no exocrine secretions
  • storage and concentration of bile
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9
Q

What is the exocrine secretions and functions of the small intestine ?

A
  • enzymes
  • salt and water
  • mucus
  • food digestion
  • maintain fluidity
  • lubrication
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10
Q

What is the exocrine secretions and functions of the large intestine ?

A
  • mucus
  • lubrication
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11
Q

How much water is ingested and lost overall per day from the body ?

A

ingested = 2 litres per day
lost = 100 ml per day lost in faeces

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12
Q

How much water is secreted through saliva and what is the pH ?

A
  • 1.5 litres per day
  • pH 6.8 - 7
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13
Q

How much water is secreted through gastric secretions and what is the pH ?

A
  • 2.3 litres per day
  • pH 1.5 - 3
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14
Q

How much water is secreted through bile and what is the pH ?

A
  • 500 ml per day
  • pH 7.8 - 8
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15
Q

How much water is secreted through pancreatic juices and what is the pH ?

A
  • 1 litre per day
  • pH 8 - 8.4
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16
Q

How much water is secreted through intestinal secretions and what is the pH ?

A
  • 1.5 litres per day
  • pH 7 - 7.4
17
Q

How much water is reabsorbed into the body and where does this take place ?

A

small intestine = 8 - 8.5 litres per day
colon = 0.4 - 1 litre per day

18
Q

How long does the food remain in the mouth ?

A

30 seconds - 1 minute

19
Q

How long does the food remain in the oesophagus ?

A

8 - 12 seconds

20
Q

How long does the food remain in the stomach ?

A

1 - 3 hours

21
Q

How long does the food remain in the small intestine ?

A

4 - 6 hours

22
Q

How long does the food remain in the colon ?

A

10 - 20 hours

23
Q

How long does the food remain in the rectum ?

A

20 - 100 hours

24
Q

Describe the nervous system in relation to the gut

A
  • the gut has its own nervous system known as the enteric nervous system
  • the Myenteric plexus or Auerbach’s plexus is located in the muscularis externa and it is largely motor in function
  • the submucosal plexus or Meissner’s plexus is located in the submucosa and is mainly sensory in function
  • parasympathetic innervation to the gut increases motility
  • sympathetic innervation to the gut decreases motility
25
Q

Describe the basic histological features of the gut

A
  • innermost layer = mucosa
    consists of simple squamous non keratinised epithelium, lamina propria and muscularis mucosa
  • next layer = submucosa
    contains the submucosal plexus
  • next layer = muscularis externa
    consists of longitudinal and circular muscle
    contains the myenteric plexus
  • outermost layer = serosa
    this is a connective tissue layer
26
Q

What are the 3 main phases of swallowing ?

A

1) oral
2) pharyngeal
3) oesophageal

27
Q

Describe the oral phase of swallowing

A
  • voluntary
  • chewing and rolling of the tongue
  • stimulates mechanoreceptors on the soft palate
  • initiates the involuntary phase
28
Q

Describe the pharyngeal phase of swallowing

A

1) raising of the soft palate allows for contraction of the superior constrictor muscles to stop food from the nasopharynx
2) initiation of peristaltic contractions - pushes the food bolus to the upper oesophageal sphincter
3) raising of the larynx closes the epiglottis
4) deglutition apnoea - inhibition of respiration

29
Q

Describe the oesophageal phase of swallowing

A
  • continuation of the peristaltic wave down the oesophagus pushes the food bolus down
  • secretion of mucus from glands in the oesophageal submucosa lubricates the oesophagus - happens in response to pressure from the food bolus
  • peristaltic wave relaxes the lower oesophageal sphincter allowing food to enter the stomach
30
Q

Describe the structure of the upper third of the oesophagus

A
  • largely striated muscle
  • peristalsis is organised from the brainstem
31
Q

Describe the structure of the lower third of the oesophagus

A
  • largely smooth muscle
  • peristaltic wave is largely innervated by the enteric nervous system
32
Q

Describe the upper oesophageal sphincter

A
  • composed of striated muscle
  • innervated by the cranial nerves
33
Q

Describe the lower oesophageal sphincter

A
  • barrier between the stomach and oesophagus
  • composed of smooth muscle
  • innervated by the enteric nervous system
34
Q

Summarise pressure changes in the oesophageal phase of swallowing

A
  • at rest the UES is closed
  • relaxation causes the UES to open
  • contraction will cause food to be pushed down the oesophagus
  • relaxation of the LES causes food bolus to move down and the LES opens
35
Q

Describe the gastric motor functions

A
  • the stomach has a basic electrical rhythm - slow phasic contraction ~ 3 contractions per minute
  • the orad region of the stomach has tonic contraction only
36
Q

What happens in the pacemaker region of the stomach ?

A
  • the basic rhythmic contraction is initiated here
  • slow waves are initiated here
37
Q

What causes the initiation of slow waves ?

A
  • caused by smooth muscle cell depolarisation
  • triggers action potentials
  • causes mechanical contraction
38
Q

Describe postprandial movements in the small intestine

A
  • villi cause small sweeping movements and mix acidic chyme and neutralised chyme
  • pendular movements allow contraction and relaxation of longitudinal muscles causing sections of the small intestine to shorten and lengthen
  • segmentation movements cause contraction and relaxation of circular smooth muscles
  • peristaltic waves propel food along the small intestine
39
Q

Describe the peristaltic reflex

A
  • stimulation of stretch receptors
  • widens the path ahead of the bolus and narrows the path behind
  • inhibitory neurones can cause an area of receptive relaxation

Digestive system and renal biology (6 decks)

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