Cardiofacial embryology

Question 1

1st aortic arch

Answer 1

Part of maxillary a. (branch of ext. carotid. a.)

Question 2

2nd aortic arch

Answer 2

stapedial and hyoid aa.

Question 3

3rd aortic arch

Answer 3

Common carotid a. and the proximal part of the int. carotid a.

Question 4

4th aortic arch

Answer 4

L: aortic arch
R: proximal right subclavian a.

Question 5

6th aortic arch

Answer 5

Proximal parts of pulmonary aa. and ductus arteriosus

Question 6

Recurrent laryngeal nn.

Answer 6

R: loops under right subclavian a.
L: loops under aortic arch DISTAL to ductus arteriosus

Question 7

Branchial (pharyngeal) apparatus

Answer 7

Clefts, arches and pouches
Clefts- ectoderm
Arches- mesoderm (mm, aa) and neural crest (bones, cartilage)
Pouches- endoderm

Question 8

1st cleft

Answer 8

ext. auditory meatus

Question 9

2nd, 3rd and 4th

Answer 9

Form temporary cervical sinuses (obliterated by 2nd arch mesenchyme)

Question 10

Persistant cervical sinus

Answer 10

Branchial cleft cyst within lateral neck, anterior to SCM m. immobile in swallowing

Question 11

1st branchial arch

Answer 11

Maxillary process makes maxilla and zygomatic process
Mandibular process makes Meckel cartilage, mandible, malleus and incus, spenomandibular ligament

Muscles of mastication (masseter, temporalis, lateral and medial pterygoids) mylohyoid, ant. belly of digastric m., tensor tympani and anterior 2/3 of tongue

CNs V2 and V3

Pierre Robin sequence- micrognathia, glossoptosis, cleft palate, airway obstruction

Treacher Collins syndrome- neural crest dysfunction leads to mandibular hypoplasia, facial abnormalities

Question 12

2nd branchial arch

Answer 12

Reichert cartilage: stapes, styloid process, lesser horn of hyoid, stylohyoid ligament

Muscles of facial expression, stapedius, stylohyoid, platysma, post. belly of digastric

CN VII

Pierre Robin sequence- micrognathia, glossoptosis, cleft palate, airway obstruction

Treacher Collins syndrome- neural crest dysfunction leads to mandibular hypoplasia, facial abnormalities

Question 13

3rd branchial arch

Answer 13

Greater horn of hyoid

Stylopharyngeus m.

CN IX (glossopharyngeal n.)

Question 14

4th-6th branchial arches

Answer 14

Arytenoids, cricoid, corniculate, cuneiform, thyroid (ACCCT)

4th- most pharyngeal constrictors; cricothyroid, levator veli palatini

6th- all intrinsic mm of larynx EXCEPT cricothyroid

4th- CN X (sup. laryngeal br.) simply swallow

6th: CN X (recur. laryngeal branch)

3 an 4 make posterior third of tongue

Question 15

1st branchial pouch

Answer 15

Middle ear cavity, eustachian tube, mastoid air cells

endoderm-lined ear structures

Question 16

2nd branchial pouch

Answer 16

Epithelial lining of palatine tonsil

Question 17

3rd branchial pouch

Answer 17

Dorsal wings become inferior parathyroids
Ventral wings become thymus

Ends up BELOW 4th

Question 18

4th branchial pouch

Answer 18

Dorsal wings become superior parathyroids

Ventral wings become ultimobranchial body and parafollicular C cells of thyroid

Question 19

Truncus arteriosus

Answer 19

Ascending aorta and pulmonary trunk

Question 20

Bulbus cordis

Answer 20

Smooth (outflow track) of L and R ventricles

Question 21

Endocardial cushions

Answer 21

Atrial septum, membranous intraventricular septum, AV and semilunar valves

Question 22

Primitive atrium

Answer 22

Trabeculated parts of atria

Question 23

Primitive ventricle

Answer 23

Trabeculated parts of ventricles

Question 24

Primitive pulmonary vein

Answer 24

Smooth part of left atrium

Question 25

left horn of sinus venosus

Answer 25

coronary sinus

Question 26

right horn of sinus venosus

Answer 26

smooth part of right atrium (sinus venarum)

Question 27

Right common cardinal vein and right anterior cardinal vein

Answer 27

SVC