Repro - Embryology (Aortic/Branchial derivatives & Cleft lip/palate)

Question 1

Into what do aortic arch derivatives develop?

Answer 1

Develop into the arterial system

Question 2

What is derived from the 1st aortic arch? Of what major vessel is this a branch?

Answer 2

Part of maxillary artery (branch of external carotid); Think: “1st arch is MAXimal”

Question 3

What is derived from the 2nd aortic arch?

Answer 3

Stapedial artery and Hyoid artery; Think: “Second = Stapedial”

Question 4

What is derived from the 3rd aortic arch?

Answer 4

Common Carotid artery and proximal part of internal Carotid artery; Think: “C is 3rd letter of alphabet”

Question 5

What is derived from the 4th aortic arch?

Answer 5

On left, aortic arch; on right, proximal part of right subclavian artery; Think: “4th arch (4 limbs) = systemic”

Question 6

What is derived from the 6th aortic arch?

Answer 6

Proximal part of pulmonary arteries and (on left only) ductus arteriosus; Think: “6th arch = pulmonary and the pulmonary-to-systemic shunt (ductus arteriosus)”

Question 7

How do right and left recurrent laryngeal nerves relate to the aortic arch?

Answer 7

See p. 558 in First Aid 2014 for visual

Question 8

What is another name for the branchial apparatus? What are its 3 components?

Answer 8

Also called pharyngeal apparatus; Composed of branchial clefts, arches, and pouches

Question 9

From what germ layer are branchial clefts derived?

Answer 9

Derived from ectoderm

Question 10

What is another name for branchial clefts?

Answer 10

Also called branchial grooves

Question 11

From what 2 embyrological origins are branchial arches derived? What are 2 examples of each source?

Answer 11

Derived from mesoderm (muscles, arteries) and neural crest (bones, cartilage)

Question 12

From what germ layer are branchial pouches derived?

Answer 12

Derived from endoderm

Question 13

List the components of the branchial apparatus from outside to inside. What germ layer gives rise to each?

Answer 13

Clefts = ectoderm, Arches = mesoderm, Pouches = endoderm; Think: “CAP covers outside to inside”

Question 14

Draw a visual of the branchial apparatus including and labeling the following: (1) Arches (2) Cleft (3) Epicardial ridge (4) Pharyngeal arches - 1st through 4th (5) Pouch (6) Primitive esophagus (7) Primitive pharynx.

Answer 14

See p. 558 in First Aid 2014 for visual near bottom right of page

Question 15

Into what does the 1st branchial cleft develop?

Answer 15

1st cleft develops into external auditory meatus

Question 16

What do the 2nd through 4th clefts form? What is the fate of this (these) structure(s), and what causes this?

Answer 16

2nd through 4th clefts form temporary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme

Question 17

What abnormality does a persistent cervical sinus cause, and where?

Answer 17

Persistent cervical sinus => branchial cleft cyst within lateral neck

Question 18

To what kind of cartilage does the 1st branchial arch give rise? What are 3 structures that result?

Answer 18

Meckel cartilage: (1) Mandible (2) Malleus (3) spheno-Mandibular ligament; Think: “M’s (also like most of its muscle derivatives)”

Question 19

To what 8 muscle derivatives does the 1st branchial arch give rise?

Answer 19

Muscles of Mastication [(1) temporalis (2) Masseter (3) lateral and (4) Medial pterygoid], (5) Mylohyoid, (6) Anterior belly of digastric, (7) Tensor tympani, (8) Tensor veli palatini; Think: “M’s, also like most of cartilage derivatives)

Question 20

To what 2 nerve derivatives does the 1st branchial arch give rise?

Answer 20

CN V2 and V3; Think: “chew (like Muscles of Mastication)”

Question 21

What abnormality is associated with 1st branchial arch? What causes this? What 2 symptoms/signs result?

Answer 21

Treacher Collins syndrome: 1st-arch neural crest fails to migrate => (1)mandibular hypoplasia, (2) facial abnormalities

Question 22

To what kind of cartilage does the 2nd branchial arch give rise? What are 4 structures that result?

Answer 22

Reichert cartilage: (1) Stapes (2) Styloid process (3) lesser horn of hyoid (4) Stylohyoid ligament; Think: “S’s (also most of muscle derivatives)”

Question 23

To what 5 muscles does the 2nd branchial arch give rise?

Answer 23

(1) Muscles of facial expression, (2) Stapedius, (3) Stylohyoid, (4) platySma, (5) belly of diastric; Think: “S’s (also most of cartilage derivatives)”

Question 24

To what nerve does the 2nd branchial arch give rise?

Answer 24

CN VII (facial expression); Think: “smile (like S’s of most cartilage and muscle derivatives)

Question 25

What abnormality is associated with the 2nd branchial arch? What causes this disorder? What symptom/sign results, and where?

Answer 25

Congenital pharyngo-cutaneous fistula: persistence of cleft and pouch => fistula between tonsilar area and lateral neck

Question 26

To what cartilage does the 3rd branchial arch give rise?

Answer 26

Cartilage: greater horn of hyoid

Question 27

To what muscle does the 3rd branchial arch give rise?

Answer 27

Stylopharyngeus; Think: “styloPHARYNGEUS innervated by glossoPHARYNGEAL nerve”

Question 28

To what nerve does the 3rd branchial arch give rise?

Answer 28

CN IX; Think: “STYLOpharygeus SWALLOW STYLishly”

Question 29

To what 5 cartilages do the 4th through 6th arches?

Answer 29

Cartilages: (1) Thyroid, (2) Cricoid, (3) Arytenoids, (4) Corniculate, (5) Cuneiform

Question 30

To what 3 muscles does the 4th branchial arch give rise?

Answer 30

4th arch: (1) most pharyngeal constrictors; (2) cricothyroid, (3) levator veli palatini

Question 31

To what muscles does the 6th branchial arch give rise?

Answer 31

6th arch: all intrinsic muscles of larynx except cricothyroid

Question 32

To what nerve does the 4th branchial arch give rise?

Answer 32

4th arch: CN X (superior laryngeal branch); Think: “SIMPLY SWALLOW”

Question 33

To what nerve does the 6th branchial arch give rise?

Answer 33

6th arch: CN X (recurrent laryngeal branch); Think: “SPEAK”

Question 34

What body part do the 3rd and 4th branchial arches form? Be specific.

Answer 34

Arches 3 and 4 form posterior 1/3 of tongue

Question 35

What is derived from the 5th branchial arch?

Answer 35

Arch 5 makes no major development contributions

Question 36

What do the nerves derived from branchial arches have in common? What is the exception?

Answer 36

These are the only CNs with both motor and sensory components (except V2, which is sensory only)

Question 37

To what nerve(s) does each branchial arch give rise?

Answer 37

(1) 1st arch - CN V2 and V3 (2) 2nd arch - CN VII (facial expression) (3) 3rd arch - CN IX (stylopharyngeus) (4) 4th arch - CN X (superior laryngeal branch) (5) 6th arch - CN X (recurrent laryngeal branch); Think: “when at the restaurant of the golden ARCHES, children tend to first CHEW (1st), then SMILE (2nd), then SWALLOW STYLishly (3rd) or SIMPLY SWALLOW (4th), and then SPEAK (6th).”

Question 38

Into what 3 structures does the 1st branchial pouch develop? What embryologic similarity do these derivatives of the 1st branchial pouch have?

Answer 38

Develops into middle ear cavity, eustachian tube, mastoid air cells; 1st pouch contributes to endoderm-lined structures of ear

Question 39

Into what does the 2nd branchial pouch develop?

Answer 39

Develops into epithelial lining of palantine tonsil

Question 40

To what 2 major divisions does the 3rd branchial pouch give rise? To what structures does each of these give rise?

Answer 40

(1) DORSAL WINGS - develops into the INFERIOR parathyroids (2) VENTRAL WINGS - develops into thymus

Question 41

To how many structures does the 3rd branchial pouch give rise, and which ones?

Answer 41

3rd pouch contributes to 3 structures (thymus, left and right inferior parathyroids)

Question 42

To what major division does the 4th branchial pouch give rise? To what structure does this give rise?

Answer 42

DORSAL WINGS - develops into the SUPERIOR parathyroids

Question 43

Which branchial pouches give rise to the dorsal wings? Given this, into which dorsal wing structures does each of these branchial pouches develop?

Answer 43

3rd and 4th branchial pouches; 3RD BRANCHIAL POUCH: Dorsal wings - develops into the INFERIOR parathyroids; 4TH BRANCHIAL POUCH: Dorsal wings - develops into the SUPERIOR parathyroids; Think: “3rd-pouch structures end up BELOW 4th-pouch structures”

Question 44

To what major derivatives does each of the branchial pouches give rise?

Answer 44

1 (ear), 2 (tonsils), 3 dorsal (bottom for interior parathyroids), 3 ventral (to = thymus), 4 (top = superior parathyroids); Think: “Ear, tonsils, bottom-to-top”

Question 45

What is (are) the embryologic defect(s) in DiGeorge syndrome? What 2 conditions result? What other kind of conditions is associated with DiGeorge syndrome?

Answer 45

Aberrant development of 3rd and 4th pouches => T-cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development). Associated with cardiac defects (conotruncal anomalies)

Question 46

What causes MEN2A syndrome?

Answer 46

Mutation of germline RET (neural crest cells)

Question 47

What are 3 manifestations of MEN2A syndrome? Give embryologic origins where applicable.

Answer 47

(1) Adrenal medulla (pheochromocytoma) (2) Parathyroid (tumor): 3rd/4th pharyngeal pouch (3) Parafollicular cells (medullary thyroid cancer): derived from neural crest cells; associated with the 4th/5th pharyngeal pouches

Question 48

What causes cleft lip?

Answer 48

Cleft lip - Failure of fusion of the maxillary and medial nasal processes (formation of primary palate)

Question 49

What are 2 potential causes of cleft palate?

Answer 49

Cleft palate - (1) Failure of fusion of the two lateral palatine processes or (2) Failure of fusion of lateral palatine proceses with the nasal septum and/or median palatine process (formation of secondary palate)

Question 50

How are cleft lip and cleft palate related, if at all?

Answer 50

Cleft lip and cleft palate have two distinct etiologies, but often occur together