Embryology

Question 1

Pharyngeal arch 1 derivatives (Ms and Ts)

Answer 1

Cartilage:  
Meckel's cartilage
Mandible
Mandibular ligament
Malleus and Incus

Muscle:
M. of mastication: master, medial pterygoid, lateral pterygoid, temporals

myohyoid
Tensor tympani
Tensor veli palatini
Ant 2/3 tongue

Nerve: V2, V3

Defect in Arch 1 –> Treacher Collins Sn

Question 2

Pharyngeal arch 2 derivatives (Ss)

Answer 2

Cartilage:
Stapes
Styloid process
Stylohyoid ligament
Lesser horn of hyoid

Muscle:
M. of facial expression
Stapedius
Stylohyoid

defects - pharyngocutaneous fistula

Nerve: CN 7

Question 3

Pharyngeal arch 3 derivatives

Answer 3

Muscle:
StyloPHARYNGEUS

Nerve:
GlossoPHARYNGEAL n.

Question 4

Pharyngeal arch 4 and 6 derivatives

Answer 4

Cartilage:
Cricoid
Thyroid
Larynx

Muscle:

4: Cricothyroid, pharyngeal m. (swallow)
6: Rest of laryngeal m. (speech)

Nerves: 4+6 = 10

CN 10: superior laryngeal to swallow; recurrent laryngeal for speech

Question 5

Aortic arch derivatives

Answer 5

1: part of maxillary a.
2: stapedial and hyoid a.
3: Common carotid and proximal internal carotid a.
4: L- adult aorta; R-proximal part of R subclavian a.
6: proximal part of pulmonary a. and ductus arteriosis

Question 6

Truncus arteriosis

Answer 6

proximal aorta and proximal pulmonary trunk

Question 7

Primitive ventricle

Answer 7

muscular (trabeculated) L and R ventricles

Question 8

Bulbus cordis

Answer 8

R/L ventricular outflow tracts (smooth parts)

Question 9

Primitive atrium

Answer 9

muscular (trabeculated) L and R atria

Question 10

Sinus venosis left horn

Answer 10

coronary sinus

Question 11

Sinus venosis right horn

Answer 11

smooth portion of right atria

Question 12

Right common cardinal v. and right anterior cardinal v

Answer 12

superior vena cava

Question 13

Foregut

Answer 13

Esophagus
stomach
1st and 2nd parts of duodenum
Liver
Gallbladder
Pancreas

Blood supply: celiac trunk
Nerve: parasym: vagus n.
Sympath: splanchnic n.

Question 14

Midgut

Answer 14

3rd and 4th parts duodenum
jejunum
ileum
appendix
colon to splenic flexure

Blood supply: SMA
Nerve: parasym: vagus n.
Sympath: splanchnic n.

Question 15

Hind gut

Answer 15

distal 1/3 colon
rectum to pectinate line

Blood: IMA
Nerve: parasym: pelvic splanchnic n.
Sympath: lumbar splanchnic n.

Question 16

Thymus origin

Answer 16

3rd branchial arch

Question 17

Adult derivatives of hepatic diverticulum and where it develops from

Answer 17

Endodermal

develops on ventral surface of foregut

becomes liver, gallbladder, biliary tree
ventral pancreatic bud –> head of pancreas

Question 18

embryologic origin of body and tail of pancreas

Answer 18

endodermal

dorsal pancreatic bud develops on foregut

Question 19

Formation of pancreas

Answer 19

ventral bud rotates around as duodenum formed, fuses w/ dorsal bud around 8 weeks

Question 20

Spleen origin

Answer 20

mesodermal

arises from dorsal mesentery of stomach

blood supply from foregut (celiac trunk)

Question 21

Liver development

Answer 21

Endoderm
Hepatic diverticulum
weeks 3-4 grows off anterior part of distal foregut
–> liver, biliary system, head of pancreas

Question 22

Major site of hematopoiesis in fetus weeks 3-28

Answer 22

Mesodermal hematopoietic stem cell migrate from mesonephrosis to the liver at 3 weeks

Liver becomes the major site of hematopoiesis until week 28

Question 23

Diaphragm development

Answer 23

Septum transversum: thick mass of cranial mesenchyme
- part of diaphragm and anterior mesentery of foregut

Merges with:
Pleuroperitoneal membrane
Dorsal mesentery of esophagus
Muscles of abdominal wall

Question 24

Kidney embryology

Answer 24

Pronephros – week 4 -> disappears

Mesonephros – fetal kidney first trimester -> male genital system

Metanephros -> adult kidney, appears week 5

Question 25

Ureteric bud

Answer 25

Caudal end of mesophros -> collecting system

Induces metanephros to differentiate into renal tubular epithelial structures -> nephrons

Question 26

Fetal erythropoiesis

Answer 26

3 wks – 1st primitive blood cell progenitors in yolk sac

true hematopoietic from mesoderm near mesonephros region
-migrate to liver

“Young Liver Synthesizes Blood”
Yolk sac 3-8 wks
Liver – most important site in fetal development
Spleen
Bone marrow 28 wks