Upper GI Tract Structure & Function Flashcards

1
Q

What is the purpose of chewing?

A

Prolonging Taste

Breaking up food so we dont choke and undergo resp. failure

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2
Q

How is chewing controlled?

A

Both voluntarily and reflexively
Voluntary:
- Somatic nerves to skeletal muscle of jaw and mouth

Reflex:

  • A cycle
  • Contraction of jaw -> pressure of food on gum, hard palate and tongue -> Mechanoreceptor -> Inhibits jaw muscles -> Loss of pressure- > Contraction of jaw….
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3
Q

NAme the salivary glands

A

3 paired glands
Parotid
Submandibular
Sublingual

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4
Q

What are the constituents of saliva?

A
Water
Mucins
Alpha-amylase
Electrolytes (Na+/K+/Cl-/HCO3-)
Lysozyme
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5
Q

What is the function of water in saliva?

A

Water is about 99% of saliva

IT softens, moistens and dilutes food particles, basically acting as a solvent

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6
Q

What is the function of mucins in saliva?

A

They make up most of the protein in saliva and combine with water to make mucous.
This creates a viscous solution to act as a lubricant to chewing/swallowing

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7
Q

What is the function of alpha-amylase in saliva?

A

It begins catalysing breakdown of polysaccharides into maltose & glucose.

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8
Q

What does alpha-amylase act on and why does it only produce specific di/monosaccharide products?

A

Polysaccharides bound by alpha-1,4-glycosidic bonds only, specifically starch & glycogen as only cellulase breaks the beta-1,4-glycosidic bonds in cellulose.

Startch and glycogen are entirely glucose so can only be broken down to maltose and glucose not any other saccharide

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9
Q

What are the purpose of electrolytes in saliva?

A

To balance tonicity and pH

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10
Q

What is lysozyme and what does it do in saliva?

A

Its a bacteriocidal enzyme that cleaves polysaccharides in bacterial cell walls

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11
Q

What alveoli are in salivary glands?

A
  • Mucous alveoli which have cells that produce mucins
  • Serous alveoli produce preotinaceous fluid full of enzymes
  • Mixed alveoli have both cells
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12
Q

How is salivation controlled?

A

Parasympathetic & Sympathetic NS stimulate salivation as does reflex control.

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13
Q

How does the parasympathetic system affect salivation?

A

Cranial nerves VII & IX (facial & Glossopharyngeal)

They stimulate secretion of a profuse watery secretion

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14
Q

How does the sympathetic system affect salivation?

A

It releases adrenaline which stimulates production of a small volume of viscous saliva.
Alpha1 adrenoceptors -> high mucous content
Beta2 adrenoceptors -> high amylase content

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15
Q

How do reflexes stimulate salivation?

A
  • Food goes in your mouth
  • Activates chemoreceptors and pressure receptors in the walls of the mouth/tongue
  • Triggers salivation
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16
Q

Whats different about the muscularis externae in the stomach to the rest of the GI tract?

A

its has 3 layers

The normal circular and longitunidal + a 3rd internal oblique layer

17
Q

How does the muscularis externa vary throughout the oesophagus?

A

In the upper 3rd its skeletal muscle & therefore has voluntary control through the somatic NS.
In the lower 2/3rds it has smooth muscle and lacks conscious control.

18
Q

How do we control entry/exit of stuff into oesophagus

A

the upper and lower oesophageal sphicters (UOS + LOS)

19
Q

What are the phases of swallowing?

A

Oral (voluntary) Phase
Pharyngeal Phase
Oesophageal Phase

20
Q

What happens in the oral phase of swallowing?

A

The bolus is pushed to the back of the mouth by the tongue

21
Q

What happens in the pharyngeal phase of swallowing?

A
  • Presence of bolus leads to a sequence of reflex contractions in the pharyngeal muscles
  • Soft palate is reflected back and up closing off the nasopharynx
  • UOS relaxes and the epiglottis covers the larynx opening
22
Q

What happens during the oesophageal phase of swallowing?

A
  • UOS contracts to prevent regurgitation
  • Peristaltic wave sweeps oesophagus
  • LOS relaxes and bolus enters stomach
23
Q

What kind of reception does the stomach give a bolus?

A

When the LOS opens the stomach relaxes.

24
Q

What controls the stomach relaxing upons recieving food? and how is its structure different when empty?

A

A vagal reflex that leds to relaxation of elastic smooth muscle in the fundus and body.

When empty this muscle is arranged in pleats called rugae to shrink the stomach

25
Q

Where are the swallowing centres that control swallowing?

A

the medulla right next to your respiratory centres

26
Q

How big can the stomach go?

A

From 50ml to 1500ml

27
Q

What are the functions of the stomach?

A
  • Temporary food store
  • Dissolves (liquidises) food & begins digestion
  • Controls steady delivery into small intestine
  • Sterilises ingested material
  • Produces intrinsic factor
28
Q

What are the sections of the stomach?

A
  • Gastroesophageal (Cardiac) opening (around LO/cardiac sphincter)
  • Cardiac region (cardia)
  • Fundus
  • Body
  • (pyloric) antrum
  • Pyloric region
  • Pyloric sphincter