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Semester 3 > GI Session 2 > Flashcards

GI Session 2 Flashcards

1
Q

Which gland mainly secretes serous saliva?

A

Parotid

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2
Q

Which gland mainly secretes mucous saliva?

A

Sublingual

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3
Q

Which gland mainly secretes mixed saliva?

A

Submandibular

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4
Q

What are the two modes of secretion of saliva?

A

By minor glands of which there are 100s to 1000s

Secretion by 3 pairs of large glands

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5
Q

How much saliva is produced per day?

A

0.5-1.5 l

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6
Q

Is saliva produced at a constant rate?

A

No, peaks in afternoon and troughs at night

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7
Q

What does salivary composition depend on?

A

Whether it is baseline or stimulated

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8
Q

What are the main components of saliva?

A 
Water
Mucus
Antibodies
Electrolytes esp calcium to protect teeth
Enzymes 
Bacterial flora
Epithelial cells
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9
Q

What control are minor salivary glands under?

A

ANS

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10
Q

What is the function of minor salivary glands releasing trace amounts of saliva?

A

Maintain hydration
Decrease friction
Prevent bacterial build up

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11
Q

What does failure of the minor sail vary glands lead to?

A

Dry mouth
Halitosis
Poor dental hygiene

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12
Q

What is the function of the mass-ejecting salivary glands?

A

Produce and store large amounts of saliva until release is stimulated by thought/sight/smell/taste of food

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13
Q

What are the three pairs of mass-ejecting salivary glands?

A

Parotids
Sublingual
Submandibular

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14
Q

What are the functions of saliva?

A 
Soften solid food to prevent mucosal tearing
Taste perception
Soft tissue repair
Maintain integrity of teeth
Dilute and clear oral sugars
Initiate oral phase of digestion
Detoxification and buffering
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15
Q

What are the three general types of saliva?

A

Serous
Mucous
Mixed

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16
Q

Where is the parotid gland situated?

A

In front of and level with external ear with deep portions behind mandible Ramos

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17
Q

What is the secretory function of the parotid gland?

A

Secretes 25-30% of all saliva but only secretes serous

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18
Q

What do the salivary secretions of the parotid gland drain through?

A

Stenson’s ducts

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19
Q

What can develop on the duct which drains the parotid gland?

A

Accessory parotid

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20
Q

Where are the submandibular salivary glands located?

A

Floor of mouth

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21
Q

What is the secretory function of the submandibular glands?

A

Produces 65-75% of all saliva which is mixed but mainly serous and amylase rich

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22
Q

How are the submandibular glands drained?

A

Wharton’s duct which emerges either side of the lingual frenulum

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23
Q

Which system innervates the submandibular glands?

A

PNS

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24
Q

What is the secretory function of the sublingual salivary glands?

A

Smallest, produce less than 5% of all saliva which is mixed but mainly mucus

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25
Q

What controls secretion by sub lingual glands?

A

ANS control of BV supplying gland

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26
Q

What does the acinus do in the secretion of saliva?

A

Primary stage of production: secretes fluid isotonic with plasma

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27
Q

What happens in the secondary stage of saliva production?

A

Ions reabsorbed –> hypotonic saliva with low sodium and chloride and high potassium and bicarbonate

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28
Q

Which cells are involved in the secondary stage of saliva production?

A

Striated duct cells

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29
Q

What happens to the composition of saliva is production is increased?

A

Reduced time for second stage therefore saliva is more hypertonic and acidic

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30
Q

What cells make up a salivary secretory unit?

A

Myoepithelial cells
Acinus cells
Secretory cells

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31
Q

What does the saliva pass through on its exit of the salivary secretory unit?

A

Acinus –> intercalated duct –> striated duct –> excretory duct

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32
Q

How do serous salivary secretory units appear histologically?

A

Dispersed chromatin
Dark staining due to zymogens
Large striated ducts

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33
Q

How do mucous salivary secretory ducts appear histologically?

A

Nuclei flattened against BM
Condensed chromatin
Light staining
Smaller striated ducts

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34
Q

What can a mixed salivary gland consist of?

A

Serous and mucus acini whose ducts join

Acini with serous and mucous cells

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35
Q

What is seen in a mixed salivary gland where mucus cells predominate?

A

Serous cells form semilunar caps on the terminal part of the mucous acini

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36
Q

What occurs if ingested foods are not recognised as food?

A

Gag reflex

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37
Q

What does testing the gag reflex examine?

A

Integrity of soft palate sensation and motor innervation which must both be intact to initiate reflex

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38
Q

When can difficulties in swallowing be seen?

A

Congenital abnormalities of the mouth
Cerebrovascular accidents causing paralysis of soft palette nerves
Hypertrophy of pharyngeal tonsils

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39
Q

What divides the oral cavity into two parts?

A

Palatoglossal arch

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40
Q

What is the oral cavity divided into?

A

Anteriorly is the mouth proper

Posteriorly is the oropharynx

41
Q

What happens in the oral phase of swallowing?

A

Preparatory phase: voluntary chewing of food to form bolus –> food bolus on tongue by pushing up onto hard palate –> bolus touches soft palate activating receptors on palatoglossal arch and pharyngeal tongue –> transit phase

42
Q

What does the transit phase of the oral phase of swallowing result in?

A

Reflex activation of pharyngeal phase

43
Q

What happens in the pharyngeal phase of swallowing?

A

Soft palate rises to close off opening between naso- and oropharynx –> hyoid bone and larynx rise to allow epiglottis to seal off airways –> tongue movement pushes food into oesophagus

44
Q

What usually identifies failure of the pharyngeal phase of swallowing?

A

Nasal regurgitation

45
Q

What happens in the oesophageal phase of swallowing?

A

Bolus enters UOS –> sphincter reflexively constricts –> primary peristaltic wave initiated below UOS by brain –> wave takes 10s to travel length of oesophagus

46
Q

What happens in the oesophageal phase of swallowing if sensory fibres in the distended oesophagus sense bolus not cleared?

A

Fibres signal for central and enteric nervous systems to initiate a secondary peristaltic wave

47
Q

What controls the lower oesophageal sphincter?

A

ANS by vagus nerve with time affected by hormones and natural variation

48
Q

Why does the oesophagus have a small diameter?

A

To ensure downward movement of food

49
Q

What causes the primitive gut to become tubular in the 4th week of development?

A

Lateral folding

50
Q

What forms the cranial and caudal pockets from the yolk sac endoderm in the 4th week of development?

A

Craniocaudal folding

51
Q

What can be said about structures developing close to embryonic divisions of the gut?

A

They have mixed blood supply

52
Q

Which adult derivatives of the embryonic gut have mixed blood supply due to their embryonic origins?

A

Duodenum proximal to the bile duct
Duodenum distal to the bile duct
Pancreas

53
Q

What gives blood supply to the GI tract?

A

3 midline branches of the aorta: coeliac trunk, SMA, IMA

54
Q

What are the adult derivatives of the foregut?

A 
Oesophagus
Stomach
Pancreas
Liver
Gallbladder
Duodenum proximal to Spincter of Oddi
55
Q

What are the adult derivatives of the midgut?

A 
Duodenum distal to sphincter of Oddi
Jejunum
Ileum
Caecum
Ascending colon
Proximal 2/3 transverse colon
56
Q

What are the adult derivatives of the hindgut?

A 
Distal 1/3 transverse colon
Descending colon
Sigmoid colon
Rectum
Upper anal canal
Internal lining of bladder and urethra
57
Q

Which aortic branch corresponds with which section of the embryonic gut?

A

Coeliac trunk - foregut
SMA - midgut
IMA - hindgut

58
Q

When does the primitive gut tube begin to develop?

A

3rd week when it pinches off from the yolk sac cavity

59
Q

What do the cranial and caudal pockets from yolk sac endoderm form?

A

Cranial –> foregut as blind diverticula

Caudal –> hindgut as blind diverticula

60
Q

Where does the primitive gut tube from and to?

A

From stomatodeum to proctodeum with opening at the umbilicus

61
Q

Where does the internal lining of the primitive gut tube derive and what will it become?

A

Endoderm –> future epithelial linings

62
Q

Where is the external lining of the primitive Gut tube from and what will it become?

A

Splanchnic mesoderm –> gut wall musculature and visceral peritoneum

63
Q

What suspends the primitive gut tube in the intraembryonic coelom?

A

Double layer of splanchnic mesoderm

64
Q

Describe how the intraembryonic coelom develops to form the abdominal cavity.

A

Endoderm lined tube as one large cavity –> diaphragm splits into abdominal and thoracic cavities –> abdominal lined by 2 separate leaves of peritoneal membrane from somatic and splanchnic mesoderm –> leaves line cavity and invest in viscera

65
Q

What is the peritoneal cavity?

A

A potential space in the abdominal cavity

66
Q

What is a mesentery?

A

Double layer of peritoneum attaching but tube to abdominal wall

67
Q

What is the function of a mesentery?

A

Allow conduit for blood and nerve supply

Allow for mobility

68
Q

How does the mesentery suspending the embryonic gut tube form?

A

Splanchnic mesoderm surrounds primitive gut tube and condensation of this forms a mesentery

69
Q

Where is mesentery found in the primitive gut tube?

A

Dorsal mesentery suspends entire gut tube form dorsal body wall
Ventral mesentery only suspends the foregut

70
Q

What are omenta?

A

Specialised folds of the peritoneum

71
Q

What is the greater omentum?

A

First structure seen on opening the anterior abdominal wall formed by the dorsal mesentery

72
Q

What is the lesser omentum?

A

Formed by the ventral mesentery, free edge conducts the portal triad

73
Q

What do the dorsal and ventral mesentery in the foregut region split the abdominal cavity into?

A

L and R peritoneal sacs

74
Q

What is the left peritoneal sac?

A

Gives rise to the greater peritoneal sacs which is entered upon opening of the abdominal cavity and peritoneum

75
Q

What is the R peritoneal sac?

A

Gives rise to lesser peritoneal sac which lies behind the stomach

76
Q

What does rotation of the stomach around the longitudinal axis cause?

A

Formation of lesser and greater curvatures of the stomach

77
Q

What happens to the mesentery as the stomach rotates 90 degrees around its longitudinal axis?

A

Fold as stomach moves –> bulge in dorsal mesentery as space between leaves increases

78
Q

What aorta of the stomach are the mesenteries attached to?

A

Ventral mesentery –> lesser curvature

Dorsal mesentery –> greater curvature

79
Q

What is the result for the innervation of the stomach following longitudinal rotation?

A

L vagus nerve innervating L side –> anterior wall

R vagus nerve innervating R side –> posterior wall

80
Q

Where does the liver develop?

A

Within the leaves of the ventral mesentery

81
Q

What happens during rotation of the stomach around the anteroposterior axis?

A

Dorsal mesentery bulge –> greater omentum and two leaves fuse
Move cardia and Pylorus from midline –> stomach lies obliquely
Moves lesser sac behind stomach

82
Q

What is the definition of a retroperitoneal structure?

A

One that was never in the peritoneal cavity and never had a mesentery e.g. Abdominal aorta, kidney

83
Q

What are secondary retroperitoneal structures?

A

Began development invested by peritoneum and had mesentery but with growth this has been lost through fusion with the posterior abdominal wall e.g. Duodenum except duodenal cap, pancreas

84
Q

What is formed in the ventral mesentery?

A

Liver
Biliary system
Ucinate process and inferior head of pancreas

85
Q

What is formed in the dorsal mesentery?

A

Superior head, neck, body and tail of pancreas

86
Q

How do the respiratory primordium and oesophagus develop from the foregut?

A

Resp diverticulum buds off from oesophagus and enlarges –> tracheosophageal septum forms to create two separate tubes

87
Q

What can result in disruption of the respiratory primordium and oesophageal development?

A

Proximal blind-ended oesophagus

Tracheosophageal fistula

88
Q

What creates the greater curvature of the stomach?

A

Faster growth on the dorsal border

89
Q

What indicates the position of the stomach primordium in the foregut?

A

Slight dilation of distal foregut

90
Q

What is the earliest GI tract associated gland to develop?

A

Liver

91
Q

How does the liver develop within the leaves of the ventral mesentery?

A

Hepatic bud forms in mesentery and grows rapidly to occupy a large proportion of the abdomen thus affecting development of lesser sac and peritoneum

92
Q

What attaches the liver to the ventral body wall and travels up the anterior aspect of the liver where it splits?

A

Falciform ligament

93
Q

What is the bare area of the liver?

A

Area not covered by visceral peritoneum as it develops in parallel where the liver is attached to the diaphragm

94
Q

Where is the lesser omentum found during development of the liver?

A

Between liver and foregut

95
Q

How does the duodenum develop?

A

Caudal foregut+cranial midgut –> grows rapidly –> stomach rotation pushes it right then against posterior abdominal wall –> c-shaped duodenum

96
Q

What happens to the duodenal endoderm all lining in the 6th week of development?

A

Becomes so well developed lumen is obliterated

97
Q

When is the duodenum lumen recanalised?

A

By the end of the embryonic period

98
Q

What grows over the duodenum making it secondarily retroperitoneal except from its cap?

A

Parietal peritoneum to form fusion fascia so structure is mobilised

Semester 3 (50 decks)

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