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Alimentary System > Upper GI Tract Structure and Function > Flashcards

Upper GI Tract Structure and Function Flashcards

1
Q

What is the purpose of chewing?

A

Prolong taste experience

Defence against respiratory failure

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2
Q

How is chewing controlled?

A

Voluntarily - somatic nerves controlling the skeletal muscles of the mouth/jaw

Reflex - contraction of jaw muscles causes pressure of food against gums, hard palate and tongue, activates mechanoreceptors causing inhibition of jaw muscles, reducing pressure causing contractions

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3
Q

Explain the process of the reflex that controls chewing?

A

1) Contraction of jaw muscles causes pressure of food against gums, hard palate and tongue
2) Activates mechanoreceptors causing inhibition of jaw muscles
3) Reduces the pressure causing contractions

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4
Q

What are the 3 pairs of glands that secretes saliva?

A

Parotid

Submandibular

Sublingual

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5
Q

What is in saliva?

A

Water

Mucins

a-Amylase

Electrolytes

Lysozyme

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6
Q

What is the function of water in saliva?

A

Softens, moistens, dilutes particles (controls osmosis)

Solvent

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7
Q

What is the function of mucin in saliva?

A

Combines with water to make mucus, viscous solution to perform lubricant function

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8
Q

What is the function of a-Amylase in saliva?

A

Catalyses breakdown of polysaccharides into disaccharide

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9
Q

What is the function of electrolytes in saliva?

A

Tonicity/pH

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10
Q

What is the function of lysozyme in saliva?

A

Bactericidal - cleaves polysaccharide component of bacterial cell wall

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11
Q

Why would teeth enamel dissolve without saliva?

A

Saliva increases the pH

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12
Q

What class are the glands that secrete saliva?

A

Exocrine

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13
Q

What does the serous alveolus of glands release?

A

a-amylase and other proteins

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14
Q

What does the mucous alveolus of glands release?

A

Mucus which enters the duct where water is secreted

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15
Q

What controls salivary secretion?

A

Parasympathetic nervous system

Sympathetic nervous system

Reflex control

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16
Q

What parasympathetic nerves control salivary secretion?

A

Cranial nerve VII (facial)

Cranial nerve IX (glossopharyngeal)

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17
Q

What effect does parasympathetic nerves have on saliva secretion?

A

Stimulates profuse watery salivary secretion

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18
Q

What effect does sympathetic nerves have on salivary secretion?

A

Stimulates small volume, viscous salivary secretion, high mucus content (a1 adrenoceptors) and high amylase content (B2 adrenoceptors)

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19
Q

What receptor does the sympathetic system act on to create high mucus content saliva?

A

a1 adrenoceptors

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20
Q

What receptor does the sympathetic system act on to create high amylase content saliva?

A

B2 adrenoceptors

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21
Q

Explain the reflex control of salivary secretion?

A

Presence of food in mouth activates chemoreceptors/pressure receptors in the walls of mouth/tongue

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22
Q

What is special about the sympathetic and parasympathetic effects on salivary secretion?

A

They are both stimulatory

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23
Q

What is the oesophagus?

A

25cm conduit (pipe) between the pharynx and stomach

24
Q

What is the length of the oesophagus?

A

25cm

25
Q

What are the 4 layers of the oesophagus?

A

Mucosa

Submucosa

Muscularis externa

Adventitia

26
Q

What is the mucosa of the oesophagus lined by?

A

Stratified squamous epithelium (non-keratinised)

27
Q

Why is it important that musosa of oesophagus is stratified and not simple?

A

Food would destroy a simple layer

28
Q

Why is it important that the mucosa of the oesophagus is non-keratinised?

A

So it is flexible

29
Q

What is contained by the submucosa of the oesophagus?

A

Submucosal mucous glands

30
Q

What do submucosal glands secrete?

A

Mucous for lubrication

31
Q

What part of the muscularis externa of the oesophagus is skeletal muscle?

A

Upper 1/3

32
Q

What part of the muscularis externa of the oesophagus is smooth muscle?

A

Lower 2/3

33
Q

What regulates movement of materia into and out of the oesophagus?

A

Upper and lower oesophageal sphincters

34
Q

What is the function of the lower oesophageal sphincter (LOS)?

A

Stops reflux and corrosion of oesophagus due to acid produced in the stomach

35
Q

Summarise the process of swallowing?

A

1) Bolus pushed to back of mouth by the tongue (oral phase)
2) Presence of bolus causes sequence of reflex contractions of pharyngeal muscle, soft palate reflected backwards and upwards (closes of nasopharynx)
3) Upper oesophageal sphincter (UOS) relaxes and epiglottis covers opening to larynx
4) UOS contracts once food enters oesophagus
5) Propulsion of bolus to stomach due to peristaltic wave sweeping the entire oesophagus
6) LOS relaxes and bolus enters tomach
7) Vagus reflexes causes relaxation of thin, elastic smooth muscle of gastric fundus and body of stomach

36
Q

What is the pharyngeal phase of swallowing coordinated by?

A

Swallowing centres in the medulla

37
Q

Why is the soft palate reflected backwards and upwards once bolus is pushed to the back of the mouth during swallowing?

A

To block of nasopharynx

38
Q

Why does the epiglottis cover the opening to the larynx during swallowing?

A

Prevent food entering the trachea

39
Q

Why does the UOS contract once food enters the oesophagus?

A

Prevent food reflux

40
Q

How long does it take for bolus to be propelled down the oesophagus to the stomach?

A

About 10 seconds

41
Q

Where is the hard and soft palate?

A

Soft palate is roof of mouth distal to entrace, hard palate is proximal to entrance

42
Q

What does the volume of the stomach range from?

A

50ml to 1500ml

43
Q

How does the pressure inside the stomach change as the volume changes?

A

Pressure does not change

44
Q

What are some functions of the stomach?

A

Temporary store of ingested material

Dissolve food particles and initiate digestive process

Control delivery of contents to small intestine

Sterilise ingested material

Produce intrinsic factor

45
Q

What is intrinsic factor required for?

A

Vitamin B12 absorption

46
Q

What is the anatomy of the pathway through the stomach?

A

Oesophagus -> gastroesophageal (cardiac) opening guarded by lower oesophageal sphincter -> cardiac region -> fundus -> body -> pyloric region -> pyloric opening (guarded by pyloric sphincter)

47
Q

What part of the stomach are the greater and lesser curvature in?

A

Body

48
Q

What guards the gastroesophageal opening of the stomach?

A

Lower oesophageal sphincter (LOS)

49
Q

What guards the pyloric opening of the stomach?

A

Pyloric sphincter

50
Q

Is adventitia or serosa present in the stomach?

A

Serosa (connective tissue outer layer)

51
Q

What are the 3 layers of the muscularis externa in the stomach?

A

Oblique (inner)

Circular (middle)

Longitudinal (outer)

52
Q

Discuss the structure of the submucosa and mucosa of the stomach?

A

Folded (known as rugae) so when empty can stretch as the stomach fills

53
Q

What are the folds in the stomach called?

A

Rugae

54
Q

What is the lumenal surface of the stomach formed from?

A

Surface mucus cells in gastric pits containing gastric glands, parietal cells and chief cells

55
Q

What is the structure of the stomach wall from superficial to deep?

A

Epithelium

Lamina propria

Muscularis mucosae

Submucosae

Oblique muscle

Circular muscle

Longitudinal muscle

Serosa

56
Q

Between what layers of the stomach wall is the myenteric plexus located?

A

Longitudinal muscle and circular muscle

Alimentary System (41 decks)

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