EMBRYOLOGY

Question 1

Where does foregut start and end

Answer 1

starts from the mouth to the common bile duct

Question 2

Where does midgut start and end

Answer 2

starts from the common bile duct to 2/3rds of the transverse colon

Question 3

where does handgun start and end

Answer 3

starts from 2/3rds of the transverse colonto the anal canal

Question 4

what is embryonic folding

Answer 4

During the 4th week of development the embryo begins to fold and change shape from a flat trilaminar disc into a cylinder - this process is known as embryonic folding

Question 5

how does embryonic folding occur

Answer 5

Folding occurs in two planes, the horizontal & medial planes

Question 6

Why does embryonic folding occur in two planes

Answer 6

Folding occurs in two planes due to the differing rates of growth of the embryonicstructures

Question 7

Folding in the horizontal planeresults in the formation of

Answer 7

of the two lateral body folds

Question 8

Folding in the medial plane results in the

Answer 8

the formation of the cranial & caudal folds

Question 9

What is mainly responsible for the formation of the GI tract

Answer 9

the endoderm

Question 10

As embryonic folding continues, the endoderm moves towards the midline and fuses

Answer 10

incorporating the dorsal part of the yolk sac to form the primitive gut tube

Question 11

The primitive gut is derived from the

Answer 11

endodermand the visceral mesoderm:

Question 12

Endoderm gives rise to

Answer 12

Epithelial lining of digestive tract

Hepatocytes of the liver

Endocrine and exocrine cells of the pancreas

Question 13

Visceral mesoderm gives rise to

Answer 13

1. Muscle, connective tissue & peritoneal components of the wall of the gut
2. Connective tissue for the glands

Question 14

The primitive gut tube, differentiates into three distinct parts

Answer 14

the foregut, midgut & hindgut

Question 15

As embryonic folding continues, the connection to the yolk sac narrows into a stalk called the

Answer 15

vitelline duct

Question 16

How many pharyngeal arches are there

Answer 16

There are five arches; 1,2,3,4 & 6 (there is no 5th in humans - sort of combines into the 4th)

Question 17

What are the pharyngeal arches are part of

Answer 17

foregut

Question 18

when do the pharyngeal arches develop

Answer 18

In the 4th & 5th week of fetal life

Question 19

Where do the pharyngeal arches extend from to

Answer 19

Extends from the oropharyngeal membrane to the respiratory diverticulum

Question 20

what are the pharyngeal arches made of

Answer 20

Formed of masses of mesenchymal tissue (connective tissue derived from mesoderm) which are invaded by cranial neural crest cells

Question 21

Each pharyngeal arch is covered externally by

Answer 21

endoderm (forming the pharyngeal clefts)

Question 22

ach pharyngeal arch is covered internally by

Answer 22

ectoderm (forming the pharyngeal pouches)

Question 23

Each arch has its own

Answer 23

nerve supply, arterial supply & venous supply

Question 24

innervation of first arch

Answer 24

Mandibular nerve (V3 - i.e third branch of trigeminal (V)

Question 25

1st arch gives rise to which muscles

Answer 25

mastication, tensor tympani, digastric, myolohyoid

Question 26

1st arch gives rise to which bones

Answer 26

maxilla, mandible, incus, malleus

Question 27

2nd arch innervation

Answer 27

facial nerve (VII)

Question 28

2nd arch muscles

Answer 28

facial expression, stapedius, stylohyoid

Question 29

2nd arch bones

Answer 29

stapes, styloid and lesser horn of hyoid cartilage

Question 30

3rd arch innervation

Answer 30

Glossopharyngeal nerve (IX)

Question 31

3rch arch muscles

Answer 31

stylopharyngeus of the pharynx

Question 32

3RD arch bones

Answer 32

body & greater horn of hyoid cartilage

Question 33

4th arch innervation

Answer 33

Superior laryngeal nerve of Vagus nerve (X)``

Question 34

4th arch muscles

Answer 34

Cricothyroid

Question 35

4th arch bone

Answer 35

thyroid cartilage & epiglottic cartilage

Question 36

6th arche innervation

Answer 36

Recurrent laryngeal nerve of Vagus nerve (X)

Question 37

6th arch muscles

Answer 37

All muscles of the larynx except the cricothyroid

Question 38

6th arch bone

Answer 38

cricoid cartilage, arytenoid cartilages, corniculate & cuneiform cartilage

Question 39

what is a mesentery

Answer 39

double layers or peritoneum that surround an organ and connect it to the body wall, such an organ is called intraperitonea

Question 40

what is a retroperitoneal organ

Answer 40

When an organ is sitting directly on the posterior abdominal wall and covered by peritoneum on its anterior surface only

Question 41

what are ligaments

Answer 41

are double layers of peritoneum which pass from one organ to anotheror from one organ to the body wall

Question 42

what do Mesenteries & ligaments provide

Answer 42

pathways for blood vessels, lymphatics & nerves to go to and come from the abdominal viscera

Question 43

By the 5th week the lower part of the foregut, midgut & major part of the hindgutare suspended from the posterior abdominal wall by

Answer 43

DORSAL MESENTERY - which extends from the lower part of the oesophagus to the cloacal region

Question 44

where is the ventral mesentery present

Answer 44

Present only in the region of the foregut - terminal part of the oesophagus, the stomach and the upper part of the duodenum

Question 45

what mesentary does the foregut have

Answer 45

the foregut has both ventral & dorsal mesenteries

Question 46

what mesentery does hindgut have

Answer 46

only dorsal mesentery

Question 47

what mesentery does midgut have

Answer 47

only dorsal mesentery

Question 48

what is The ventral mesentery derived from

Answer 48

derived from the septum transversum

Question 49

what does the free lower margin of the ventral mesentery contain

Answer 49

the hepatic artery, portal vein and bile duct

Question 50

where does the liver develop and how does this affect the mesentery

Answer 50

The liver develop IN the ventral mesentery and divides IT into the lesser omentum& the falciform ligament

Question 51

how does the stomach first appear at the 4th week

Answer 51

Appears as a fusiform (spiral-shaped) dilation in the foregut in the 4th week

Question 52

the appearance and position of the stomach changes greatly as a result of

Answer 52

the different rate of growth in variousregions of its wall

Question 53

The developing stomach is attached to the body walls by

Answer 53

the dorsal & ventral mesenteries

Question 54

The left & right vagus nerves flank

Answer 54

the left andright side of the developing stomach respectively

Question 55

what part of the stomach grows faster than what what does this from

Answer 55

The dorsal wall of the stomach grows faster thanthe ventral wall, this differential growthforms the greater & lesser curvatures of the stomach

Question 56

During the 7th week what happens to the stomach

Answer 56

the stomach rotates 90 degrees CLOCKWISEabout a longitudinal axis - this rotate produces a space behind the stomach called the lesser sac

Question 57

What happens to the stomach and duodenum in the 8th week

Answer 57

In the 8th week the stomach and duodenum ROTATE about a ventrodorsal axis, pulling the end of the stomachupwards, theypull the duodenum into a C-shape

Question 58

what do the rotations in the 8th week result in

Answer 58

These rotations result in the thinning of the dorsal mesentery, which now hangs from the greater curvature of the stomach - it is now called the greater omentum The ventral mesentery is now attached to the developing liver and has formed the lesser omentum

Question 59

The space anterior to the stomach is called the

Answer 59

greater sac

Question 60

The greater and lesser sacs communicate via

Answer 60

a small opening (located near the hilum of the liver) called the epiploic foramen

Question 61

During the fetal period, the anterior & posterior folds of the greater omentumFUSE to form oneTHICK sheet formed from

Answer 61

4 layers of peritoneum