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Systems 2 - The Gastrointestinal System > Upper GI Tract Structure and Function > Flashcards

Upper GI Tract Structure and Function Flashcards

1
Q

What two reasons do we chew for?

A
  • Prolonging taste

- Defence against respiratory failure (choking)

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2
Q

How is chewing controlled?

A

Voluntary and reflex

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3
Q

How is the voluntary aspect of chewing regulated?

A

Somatic nerves innervate skeletal muscles in jaw/mouth

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4
Q

What reflexes play a role in chewing?

A

Contraction of jaw muscles increased pressure of food against gums, hard palate and tongue which stimulates mechanoreceptors which inhibit jaw muscles

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5
Q

What is the oesophagus?

A

Conduit between pharynx and stomach

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6
Q

Approx. how long is the oesophagus?

A

25cm

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7
Q

What four layers does the oesophagus have?

A

Mucosa, submucosa, Muscular externa and adventitia

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8
Q

Describe the histology of the mucosa of the oesophagus

A

Stratified, non-keratinised, squamous epithelium

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9
Q

What structures are contained in the submucosa?

A

Mucous glands and ducts

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10
Q

Describe the muscle distribution in the oesophagus

A

Upper third = skeletal muscles

Lower two thirds = smooth muscle

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11
Q

What two structures in the oesophagus regulate movement of material?

A

Upper and lower sphincters

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12
Q

What three phases of swallowing are there?

A

Oral phase
Pharyngeal phase
Oesophageal phase

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13
Q

What occurs during the oral phase?

A

Bolus is pushed to the back of the mouth by the tongue

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14
Q

What occurs during the pharyngeal phase?

A

Presence of bolus stimulates a series of reflex contractions of pharyngeal muscles

Soft palate reflected upwards to close nasopharynx

Upper oesophageal sphincter relaxes and epiglottis covers larynx

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15
Q

What region of the brain coordinates swallowing?

A

Swallowing centre in the medulla

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16
Q

What happens once food has entered the oesophagus?

A

Propulsion of food towards stomach (approx. 10s) by peristaltic wave.

Lower oesophageal sphincter relaxes

Receptive relaxation of stomach by vagal reflexes (relaxation of funds and body of stomach)

17
Q

What is the volume range of the stomach with no change in pressure?

A

50-1500ml

18
Q

What three glands produce saliva?

A

Parotid , submandibular and sublingual

19
Q

What are the components of saliva?

A 
Water (99%)
Mucins
alpha-Amylase
Electrolytes 
Lysozyme
20
Q

What is mucus?

A

Combination of water and mucins (lubricartes, softens, moistens and good solvent)

21
Q

What is the function of alpha-amylase?

A

Catalyses breakdown of polysaccharides (starch and glycogen) into maltose

22
Q

What is the function of electrolytes in saliva?

A

Maintains pH and tonicity

23
Q

What is the function of lysozyme in saliva?

A

Bactericidal - cleaves polysaccaride component of bacteria cell wall

24
Q

What division of the nervous system regulates saliva secretion?

A

Autonomic (both parasympathetic and sympathetic)

25
Q

What parasympathetic nerves control secretion of saliva?

A

Cranial nerves VII (facial) and IX (glossopharyngeal)

26
Q

What is the effect of the parasympathetic system on saliva secretion?

A

Stimulates profuse watery saliva

27
Q

What is the effect of the sympathetic system on saliva secretion?

A

Small volume of highly viscous saliva

High mucus (alpha-1 adrenoreceptors) and high amylase (beta-2 adrenoreceptors)

28
Q

What reflexes are involved in the salivary system?

A

Presence of food in the mouth stimulates chemoreceptors and mechanoreceptors which stimulate secretion

29
Q

What are the main functions of the stomach?

A
  • Temporary food storage
  • Dissolves food and initiates digestion
  • Controls delivery of contents into the small intestine
  • Sterilises ingested material
  • Produces intrinsic factor
30
Q

What type of tissue is the serosa made of?

A

Connective tissue

31
Q

The stomach has THREE layers to the muscularis externa in the stomach. What are they?

A

Outer - longitudinal
Middle - circular
Inner - oblique

32
Q

How is the stomach folded when empty?

A

Folded into rugae

Accommodates volume range from 50ml-1500ml without pressure change

33
Q

Describe the lumenal surface of the stomach

A
  • Surface mucus cells
  • Gastric pits which house gastric glands
  • Mucus neck house parietal and chief cells

Systems 2 - The Gastrointestinal System (15 decks)

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