Session 3

Question 1

what is physiological herniation of the midgut

Answer 1

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

Question 2

what is the midgut connected to

Answer 2

yolk sac

Question 3

how does the mid gut rotate

Answer 3

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

Question 4

where is the midget connected to the yolk sac

Answer 4

midpoint

Question 5

what is meckel’s diverticulum

Answer 5

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

Question 6

what forms the transverse colon

Answer 6

The hindgut through the superior portion of the anal canal

Question 7

how does the anal canal have 2 origins

Answer 7

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

Question 8

where does recanalisation occur

Answer 8

oesophagus, bile duct and small intestine

Question 9

when does canalisation occur

Answer 9

weeks 6-8

Question 10

what is pyloric stenosis

Answer 10

hypertrophy of the pyloric sphincter

Question 11

What is one consequence of pyloric stenosis

Answer 11

Vomiting in infants

Question 12

What is gastroschisis

Answer 12

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

Question 13

What is an omphalocoele

Answer 13

Persistence of the physiological herniation of midgut

Question 14

What divides the anal canal into superior and inferior parts

Answer 14

Pectinate line

Question 15

What is the cloaca

Answer 15

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

Question 16

What is the primary constituent of saliva

Answer 16

Water

Question 17

What is contained in saliva that maintain oral hygiene

Answer 17

IgA, lysozymes and lactoferrin an initiate the process of digestion

Question 18

What is xerostomia

Answer 18

Reduced flow of saliva in the oral cavity

Question 19

What are the three paired salivary glands

Answer 19

Parotid
Submandibular
Sublingual

Question 20

What is the primary regulator of saliva production

Answer 20

Autonomic system - parasympathetic

Question 21

What causes dry mouth and what is the name for it

Answer 21

Xerostomia

Anything that reduces parasympathetic innervation

Question 22

What are the three phases of swallowing

Answer 22

Oral
Pharyngeal
Oesophageal

Question 23

Oral phase

Answer 23

Voluntary

Results i bolus being pushed back onto pharyngeal wall

Question 24

Pharyngeal phase

Answer 24

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.

Question 25

What protects the nasal cavity during swallowing

Answer 25

Soft palate

Question 26

What protects the respiratory tract during swallowing

Answer 26

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

Question 27

Oesophageal phase

Answer 27

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

Question 28

What is teh sensory component of the swallow reflex

Answer 28

The glossophryngeal nerve - cranial nerve 9

Question 29

What innervates most of the muscles involved in the swallow reflux

Answer 29

Cranial nerve 10

Question 30

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

Answer 30

Pharyngeal constrictor

Question 31

How can you distinguish between the sublingual gland and submandibular gland

Answer 31

Submandibular sits medially and sublingual sits laterally

Question 32

What is the main driver of Salivary secretion

Answer 32

Parasympathetic- increases production

Question 33

Parotid sialography

Answer 33

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

Question 34

What is the difference of anatomy in babies

Answer 34

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

Question 35

Gag reflex

Answer 35

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

Question 36

How does the muscle change down the oesophagus

Answer 36

Goes from voluntary skeletal muscle to involuntary smooth muscle

Question 37

What is dysphagia

Answer 37

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

Question 38

Rule of 2’s meckels diverticulum

Answer 38

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

Question 39

which hindgut derivatice does not form part of the GI tract

Answer 39

bladder epithelia

Question 40

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

Answer 40

urorectal septum

Question 41

what is the proctodeum

Answer 41

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

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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.

Question 44

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

Answer 44

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

Question 45

Briefly explain how acid secretion is inhibited when the stomach empties

Answer 45

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

Question 46

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

Answer 46

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

Question 47

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?

Answer 47

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.