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The Alimentary Canal > Upper GI Tract Structure and Function > Flashcards

Upper GI Tract Structure and Function Flashcards

1
Q

Why chew?

A

Prolong taste experience
Defence against resp. failure

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2
Q

How is chewing controlled voluntary?

A

Somatic nerves - skeletal muscles of mouth and jaw

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3
Q

Explain chewing controlled by reflex

A

Contraction of jaw muscles then pressure of food against gums, hard palette and tongue - mechanoreceptors - inhibition of jaw muscles so reduced pressure - contraction etc.

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4
Q

What are some main structures in the mouth?

A

Parotid duct
Parotid gland
Ducts of sublingual gland
Sublingual gland
Submandibular gland

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5
Q

What glands secrete saliva?

A

Parotid
Submandibular
Sublingual

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6
Q

What is saliva made up of?

A

Water, Mucins, Alpha amylase, electrolytes and lysozymes

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7
Q

Why is water in saliva?

A

Softens, moistens, dilutes particles
Acts as solvent

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8
Q

Why is mucins in saliva?

A

Major glycoprotein component
Lubricant function
Mucins + water is mucus

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9
Q

Why is alpha amylase in saliva?

A

Catalyses the breakdown of polysaccharides (starch and glycogen) into disaccharides and glucose

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10
Q

Why is electrolytes in saliva?

A

Tonicity and pH

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11
Q

Why is lysozymes in saliva?

A

Bactericidal so cleaves polysaccharide component of bacteria cell wall

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12
Q

How is salivary secretion controlled?

A

Parasympathetic and sympathetic
Both stimulatory

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13
Q

Explain the parasympathetic control of salivary secretion

A

Cranial nerves - facial (7) and glossopharyngeal (9)
Stimulation causes profuse watery salivary secretion

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14
Q

Explain sympathetic control of salivary secretion

A

Stimulation causes small volume and viscous saliva
High mucus content then alpha 1 adrenoreceptors
High amylase content then alpha 2 adrenoreceptors

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15
Q

Explain the reflex control of salivary secretion

A

Pressure of food in mouth activates chemoreceptors and pressure receptors

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16
Q

What causes lubrication of the oesophagus?

A

Submucosal mucous glands that secrete mucus out of ducts

17
Q

Explain the muscularis externa of the oesophagus

A

Upper 1/3 is skeletal muscle
Lower 2/3 is smooth muscle

18
Q

What is the function if the upper and lower oesophageal sphincters?

A

Regulate movement of material into and out of oesophagus

19
Q

Describe the oral phase of swallowing

A

Voluntary
Bolus pushed to back of mouth by tongue

20
Q

Describe the pharyngeal phase of swallowing

A

Presence of bolus causes sequence of reflex contractions of pharyngeal muscles
Co-ordinated by medulla
Soft palette reflected back and upwards

21
Q

Describe what happens when bolus approaches oesophagus?

A

Upper oesophageal sphincter UOS relaxes and epiglottis covers opening to larynx

22
Q

What happens when food has entered the oesophagus?

A

UOS contracts so prevention of food reflux

23
Q

Explain the oesophageal phase of swallowing

A

Propulsion of bolus to stomach
Peristaltic wave sweeps along entire oesophagus
Propelled to stomach in about 10 seconds

24
Q

What happens as bolus nears stomach?

A

Lower oesophageal sphincter (LOS) relaxes so bolus can enter stomach

25
Q

Explain receptive relaxation of stomach

A

Initiated following relaxation of LOS and entry of bolus into stomach
Vagal reflexes - relaxation of thin smooth muscle of gastric fundus and body

26
Q

How much is stomach volume?

A

50ml to 1500ml

27
Q

What are the functions of the stomach?

A

Temporary store of ingested material
Dissolve food particles and initiates digestion
Control delivery to small intestine
Sterilisation
Produce intrinsic factor

28
Q

Describe the anatomy of the stomach in order

A

Oesophagus - gastroesophageal opening - cardiac region - fundus - body - pyloric region - pyloric opening

29
Q

What are the layers of stomach tissue?

A

Serosa
Muscularis externae
Submucosa and mucosa
Lumen surface

30
Q

What are the 3 layers of the stomach muscularis externae?

A

Longitudinal
Circular
Oblique

The Alimentary Canal (33 decks)

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