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GI System > Session 3 > Flashcards

Session 3 Flashcards

1
Q

what is physiological herniation of the midgut

A

it protudes into the abdominal wall as by week 6 it grows faster than the abdominal wall and into the umbilical cord

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2
Q

what is the midgut connected to

A

yolk sac

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3
Q

how does the mid gut rotate

A

it forms a loop with the superior mesenteric artery within the umbilical cord

the distal part of the loop develops a caecal bulge and the proximal part becomes convuluted

the midgut states while in the umbilical cord and then returns to the abdomen around week 10- 3x 90 degree rotations

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4
Q

where is the midget connected to the yolk sac

A

midpoint

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5
Q

what is meckel’s diverticulum

A

when the vitelline duct doesn’t obliterate and the contents can herniate out into the yolk sac through the umbilicus

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6
Q

what forms the transverse colon

A

The hindgut through the superior portion of the anal canal

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7
Q

how does the anal canal have 2 origins

A

At first the hindgut ends blindly at the cloacal membrane which separates it from the proctodaeum. When the membrane ruptures, the hindgut is connected to the exterior

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8
Q

where does recanalisation occur

A

oesophagus, bile duct and small intestine

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9
Q

when does canalisation occur

A

weeks 6-8

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10
Q

what is pyloric stenosis

A

hypertrophy of the pyloric sphincter

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11
Q

What is one consequence of pyloric stenosis

A

Vomiting in infants

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12
Q

What is gastroschisis

A

Failure of closure of the abdominal wall following folding of the embryo which results in gut tube and derivates outside the body cavity

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13
Q

What is an omphalocoele

A

Persistence of the physiological herniation of midgut

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14
Q

What divides the anal canal into superior and inferior parts

A

Pectinate line

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15
Q

What is the cloaca

A

A region at the end of the hindgut that divides into an anterior urugenital sinus and a posterior anorectal canal

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16
Q

What is the primary constituent of saliva

A

Water

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17
Q

What is contained in saliva that maintain oral hygiene

A

IgA, lysozymes and lactoferrin an initiate the process of digestion

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18
Q

What is xerostomia

A

Reduced flow of saliva in the oral cavity

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19
Q

What are the three paired salivary glands

A

Parotid
Submandibular
Sublingual

20
Q

What is the primary regulator of saliva production

A

Autonomic system - parasympathetic

21
Q

What causes dry mouth and what is the name for it

A

Xerostomia

Anything that reduces parasympathetic innervation

22
Q

What are the three phases of swallowing

A

Oral
Pharyngeal
Oesophageal

23
Q

Oral phase

A

Voluntary

Results i bolus being pushed back onto pharyngeal wall

24
Q

Pharyngeal phase

A

Involuntary
Involves bolus moving from oral cavity ti the beginning of the oesophagus

Elevation of the soft palate to protect the nasopharynx
Elevation of the larynx (which closes the epiglottis)
Adduction of the vocal cords
Relaxation of the upper oesophageal sphincter.

25
Q

What protects the nasal cavity during swallowing

A

Soft palate

26
Q

What protects the respiratory tract during swallowing

A

Elevation of the larynx (which closes the epiglottis)and addiction of the vocal cords

27
Q

Oesophageal phase

A

Involuntary
Involves closure of upper oesophageal sphincter to prevent reflux
Rapid peristaltic movement of the oesophagus propelling the bolus into the stomach

28
Q

What is teh sensory component of the swallow reflex

A

The glossophryngeal nerve - cranial nerve 9

29
Q

What innervates most of the muscles involved in the swallow reflux

A

Cranial nerve 10

30
Q

What moves the bolus from the posterior aspect o the oral cavity to the oesophagus

A

Pharyngeal constrictor

31
Q

How can you distinguish between the sublingual gland and submandibular gland

A

Submandibular sits medially and sublingual sits laterally

32
Q

What is the main driver of Salivary secretion

A

Parasympathetic- increases production

33
Q

Parotid sialography

A

Medium has been inserted using a thin catheter which allows us to look at the ducts in the gland

34
Q

What is the difference of anatomy in babies

A

The epiglottis extend into the nasopharynx so there is a patent airway constantly as the neck grows the epiglottis descends- allows speech

35
Q

Gag reflex

A

Mechanoreceptors -> glossopharyngeal nerve -> medulla -> vagus nerve -> pharyngeal constrictors

36
Q

How does the muscle change down the oesophagus

A

Goes from voluntary skeletal muscle to involuntary smooth muscle

37
Q

What is dysphagia

A

Difficulty swallow and can have a neural cause or a physical obstructive cause

38
Q

Rule of 2’s meckels diverticulum

A
  1. 2% of population
  2. Located 2 feet proximal to ileo-caecal valve
  3. Detected in under 2s
  4. 2:1 ration M:F
39
Q

which hindgut derivatice does not form part of the GI tract

A

bladder epithelia

40
Q

what wedge of mesoderm separates the cloaca into separare urogenital and anorectal spaces

A

urorectal septum

41
Q

what is the proctodeum

A

a layer of ectoderm overlying a depression where the anus will form

42
Q

The anal canal is formed from both ectoderm and endoderm. In basic terms why is this significant?

A

Two different epithelia (stratified squamous and columnar)
Different pain receptors above and below pectinate line
Different blood supply/venous drainage and lymphatic drainage above and below pectinate line

43
Q

Explain why salivary glands produce a less hypotonic saliva when they are activated compared to
when they are rest

A

When saliva is produced in volume it flows through the ducts quicker and so has less contact time with the
ductal cells. As a result, when active the saliva produced is less modified and has had less Na and Cl ions
removed and so is relatively hypertonic compared to saliva produced at rest.

44
Q

Briefly describe how saliva ends up hypotonic when the initial solution produced by the acinar cells is
isotonic

A

The acinar cells of the salivary gland produce an isotonic solution.
This passes through the ductal cells (myoepithelial cells contract the acinus) where there is movement of ions
More Na and Cl ions are removed from the saliva than K and HCO3 ions secreted into the saliva and since the
ductal cells are relatively impermeable to water, the result is a relatively hypotonic solution

45
Q

Briefly explain how acid secretion is inhibited when the stomach empties

A

Stretch is reduced so there is no direct stimulation of G cells by the vagus nerve.
D cells detect a drop in pH and release the hormone Somatostatin, which then goes and inhibits G cells from
releasing the hormone Gastrin

46
Q

. Briefly explain why there is a transient rise in the pH of blood draining the stomach (alkaline tide)
when parietal cells are producing acid?

A

Carbonic acid dissociates into H+ ions and HCO3- ions in the cytosol of the stomach. The H+ is moved into the
stomach lumen by the proton pumps and the Bicarbonate ions are exchanged with Cl- on the basolateral
membrane. These Bicarbonate ions are then moved into the venous drainage of the stomach and temporarily
raise its pH

47
Q

Briefly explain how it is possible to develop an adenocarcinoma in the lower oesophagus despite the
fact that this area is lined with stratified squamous epithelia?

A

If you have chronic reflux disease then you lower oesophageal epithelia can undergo a metaplastic change to
gastric columnar epithelia. If this becomes dysplastic then the result can be a carcinoma of glandular tissue, an
adenocarcinoma.

GI System (16 decks)

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