GI

Question 1

what is the embryology of the gut?

Answer 1

foregut, midgut, hindgut

Question 2

what is the foregut? what is its blood supply/contents?

Answer 2

starts from mouth to the common bile duct

pharynx, oesophagus, stomach, proximal half of the duodenum and the derivative (liver, biliary apparatus and pancreas)

celiac trunk

Question 3

what is the midgut? what is its blood supply/contents?

Answer 3

common bile duct to proximal 2/3s of the transverse colon

distal half of duodenum, jejunum, ileum, caecum, appendix, ascending colon, proximal 2/3s of transverse colon

SMA

Question 4

what is the hindgut? what is its blood supply/contents?

Answer 4

distal 2/3s of transverse colon to anal canal

distal 2/3s of transverse colon, descending colon sigmoid colon, rectum, anal canal

IMA

Question 5

what is embryonic folding? when does it occur?

Answer 5

4th week of development

embryo begins to fold and change shape from a flat trilaminar disk into a cylinder

Question 6

in what planes does embryonic folding occur? why?

Answer 6

horizontal and medial planes

due to differing rates of growth of structures

Question 7

what does folding in the horizontal plane lead to?

Answer 7

formation of 2 lateral body folds

Question 8

what does folding in the medial plane lead to?

Answer 8

cranial and caudal folds

Question 9

when does folding in planes occur in relation to eachother?

Answer 9

simultaneously

Question 10

what is mainly responsible for the development of the GI tract?

Answer 10

endoderm

Question 11

how is the primitive gut tube formed? what is it derived from?

Answer 11

as embryonic folding continues, the endoderm moves towards the midline and fuses - incorporating dorsal part of the yolk sac to form the primitive gut tube

endoderm and visceral mesoderm

Question 12

what does endoderm give rise to?

Answer 12

epithelial lining of digestive tract

hepatocytes of liver

endocrine and exocrine cells of the pancreas

Question 13

what does the visceral mesoderm give rise to?

Answer 13

muscle, connective tissue and peritoneal components of gut wall

connective tissue for the glands

Question 14

what does the primitive gut tube differentiate into?

Answer 14

foregut, midgut and hindgut

Question 15

where does the foregut lie? how does it develop?

Answer 15

cranial end of the embryo

temporarily closed by oropharyngeal membrane which ruptures at the end of the 4th week to form the mouth

Question 16

how does the mouth develop?

Answer 16

foregut is temporarily closed by oropharyngeal membrane - ruptures at end of 4th week

Question 17

where does the midgut lie? how does it develop?

Answer 17

between the foregut and hindgut

connected to yolk sac until 5th week of development

connection narrows into stalk called vitelline duct

Question 18

how is the vitelline duct develop?

Answer 18

connects midgut to yolk sac

Question 19

where does the hindgut lie? how does it develop?

Answer 19

caudal end of the embryo

temporarily closed by cloacal membrane - ruptures during 7th week to form anus

Question 20

how does the anus develop?

Answer 20

hindgut is temporarily closed by cloacal membrane - ruptures during 7th week

Question 21

what are the pharyngeal arches?

Answer 21

part of foregut

extend from oropharyngeal membrane to respiratory diverticulum

Question 22

when do pharyngeal arches develop?

Answer 22

4th and 5th week

Question 23

how many arches are there?

Answer 23

5: 1,2,3,4,6

Question 24

what contributes to the external appearance of the embryo?

Answer 24

pharyngeal arches

Question 25

what are the pharyngeal arches formed by? what are they covered by?

Answer 25

masses of mesenchymal tissue - invaded by cranial neural crest cells externally by endoderm (pharyngeal clefts) internally by ectoderm (pharyngeal pouches)

Question 26

what forms the pharyngeal clefts?

Answer 26

pharyngeal arch covered externally by endoderm

Question 27

what forms the pharyngeal pouches?

Answer 27

pharyngeal arch covered internally by ectoderm

Question 28

what is mesenchymal tissue?

Answer 28

connective tissue derived from mesoderm

Question 29

what do the pharyngeal arches develop into?

Answer 29

structures of the pharynx and larynx

Question 30

what is the innervation of the 1st pharyngeal arch?

Answer 30

mandibular nerve (V3)

Question 31

what muscles does the 1st pharyngeal arch give rise to?

Answer 31

mastication, tensor tympani, digastric, mylohyoid, tensor veli palatinii

Question 32

what bones does the 1st pharyngeal arch give rise to?

Answer 32

maxilla, mandible, incus, malleus, sphenomandibular ligament, zygomatic bone

Question 33

what pharyngeal cleft gives rise to what permanent structure in the adult?

Answer 33

1st cleft - external auditory meatus

Question 34

what do the other clefts form? what are they then obliterated by?

Answer 34

2nd, 3rd, 4th - temporary cervical sinuses rapidly proliferating 2nd pharyngeal arch

Question 35

what muscles does the 2nd pharyngeal arch give rise to?

Answer 35

facial expression, stapedius, stylohyoid

Question 36

what bones does the 2nd pharyngeal arch give rise to?

Answer 36

stapes, styloid and lesser horn of hyoid cartilage

Question 37

what is the innervation of the 2nd pharyngeal arch?

Answer 37

facial nerve

Question 38

what is the innervation of the 3rd pharyngeal arch?

Answer 38

glossopharyngeal nerve (IX)

Question 39

what muscles does the 3rd pharyngeal arch give rise to?

Answer 39

stylopharyngeus of the pharynx

Question 40

what bones does the 3rd pharyngeal arch give rise to?

Answer 40

body and greater horn of hyoid cartilage

Question 41

what is the innervation of the 4th pharyngeal arch?

Answer 41

superior laryngeal nerve of the vagus nerve (X)

Question 42

what muscles does the 4th pharyngeal arch give rise to?

Answer 42

cricothyroid

Question 43

what bones does the 4th pharyngeal arch give rise to?

Answer 43

thyroid cartilage and epiglottic cartilage

Question 44

what is the innervation of the 6th pharyngeal arch?

Answer 44

recurrent laryngeal nerve of the vagus nerve (X)

Question 45

what muscles does the 6th pharyngeal arch give rise to?

Answer 45

all muscles of the larynx except the cricothyroid

Question 46

what bones does the 6th pharyngeal arch give rise to?

Answer 46

cricoid cartilage, arytenoid cartilages, corniculate and cuneiform cartilages

Question 47

when do the respiratory diverticulum appear? where?

Answer 47

at 4th week end of pharynx and beginning of oesophagus, at ventral wall of foregut

Question 48

what separates the respiratory diverticulum from the dorsal foregut?

Answer 48

tracheoesophageal septum - divided into ventral respiratory primordium and dorsal oesophagus

Question 49

how does the oesophagus develop?

Answer 49

initially it's short, but it lengthens rapidly with descent of heart and lungs

Question 50

what are mesenteries?

Answer 50

double layers of peritoneum surround and organ and connect it to the body wall (intraperitoneal)

Question 51

what is an intraperitoneal organ?

Answer 51

mesentery surrounding an organ and connecting it to the body wall

Question 52

what is a retroperitoneal organ?

Answer 52

sitting directly on posterior abdominal wall and covered by peritoneum on its anterior surface only

Question 53

what are ligaments?

Answer 53

double layers of peritoneum which pass from one organ to another or from one organ to the body wall

Question 54

what can mesenteries provide?

Answer 54

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

Question 55

when does the dorsal mesentery appear? what does it do?

Answer 55

5th week lower part of foregut, midgut and major part of hindgut are suspended from posterior abdominal wall by dorsal mesentery

Question 56

where does the dorsal mesentery extend?

Answer 56

from the lower part of the oesophagus to the cloacal region

Question 57

where is the ventral mesentery present?

Answer 57

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

Question 58

what mesenteries does the foregut have?

Answer 58

ventral and dorsal

Question 59

what mesenteries do the midgut and hindgut have?

Answer 59

dorsal mesentery

Question 60

where is the ventral mesentery derived from?

Answer 60

septum transversum

Question 61

what does the free lower margin of the ventral mesentery contain?

Answer 61

hepatic artery, portal vein, bile duct

Question 62

what develops in the ventral mesentery?

Answer 62

liver divides it into the lesser omentum and the falciform ligament

Question 63

when does the stomach first appear?

Answer 63

fusiform (spiral shaped) dilation in the foregut in the 4th week

Question 64

why does the position and appearance of the stomach change?

Answer 64

different rates of growth in various regions of the wall

Question 65

how is the developing stomach attached to body walls?

Answer 65

dorsal and ventral mesentaries

Question 66

what lies beside the developing stomach?

Answer 66

left and right vagus nerves

Question 67

what forms the greater and lesser curvatures of the stomach?

Answer 67

dorsal wall grows faster than the ventral wall