Embryo

Question 1

1st aortic arch

Answer 1

Maxillary artery

1st is max

Question 2

2nd aortic arch

Answer 2

Stapedial artery and hyoid artery

Second = stapedial

Question 3

3rd aortic arch

Answer 3

Common carotid artery and proximal part of internal carotid artery
C is 3rd letter

Question 4

4th aortic arch

Answer 4

On left, aortic arch; on right, proximal part of subclavian artery
4th arch = 4 limbs

Question 5

6th aortic arch

Answer 5

Proximal part of pulmonary arteries and (on left only) ductus arteriosus

Question 6

1st branchial arch

Answer 6

Cartilage: Meckel cartilage, Mandible, Malleus, incus, sphenoMandibular ligament
Muscles: Muscles of mastication (temporalis, Masseter, lateral and Medial pterygoids), Mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini)
Nerves: CN V2 and V3 chew
Abnormalities/Comments: Treacher Collins syndrome - 1st arch neural crest fails to migrate causes mandibular hypoplasia, facial abnormalites

Question 7

2nd branchial arch

Answer 7

Cartilage: Reichert cartilage: Stapes, Styloid process, lesser horn of hyoid, Stylohyoid ligament
Muscles: Muscles of facial expression, stapedius, Stylohyoid, platySma, posterior belly of digastric
Nerves: CN VII (facial expression). Smile
Abnormalities/Comments: Congenital pharyngocutaneous fistula - persistence of cleft and pouch -> fistula between tonsillar area and lateral neck

Question 8

3rd branchial arch

Answer 8

Cartilage: greater horn of hyoid
Muscles: Stylopharyngeus (think of styloPHARYNGEUS innervated by glossoPHARYNGEAL nerve)
Nerves: CN IX (stylopharyngeus) swallow stylishly
Abnormalities/Comments:

Question 9

4th-6th branchial arch

Answer 9

Cartilage: Thyroid, cricoid, arytenoids, corniculate, cuneiform
Muscles: 4th - most pharyngeal constrictors, cricothyroid, levator veli palatini. 6th - all intrinsic muscles of larynx except cricothyroid
Nerves: 4th - CN X (superior laryngeal branch) simply swallow. 6th - CN X (recurrent laryngeal branch) speak.
Abnormalities/Comments: Arches 3 and 4 form posterior 1/3 of tongue; arch 5 makes no major contributions.

Question 10

Mnemonic for arches

Answer 10

When at the golden ARCHES, children tend to first chew (1), then smile (2), then swallow stylishy (3), or simply swallow (4), and then speak (6)

Arches are mesoderm

Question 11

1st branchial pouch

Answer 11

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

Question 12

2nd branchial pouch

Answer 12

Derivatives: Develops into epithelial lining of palatine tonsils
Notes:

Question 13

3rd branchial pouch

Answer 13

Derivatives: Dorsal wings - develop into inferior parathyroids. Ventral wings - develop into thymus
Notes: 3rd pouch contributes 3 structures (thymus, left and right inferior parathyroids). 3rd pouch structures end up below 4th pouch structures

Question 14

4th branchial pouch

Answer 14

Derivatives: Dorsal wings - develop into superior parathyroid
Notes:

Question 15

Mnemonic for branchial pouches

Answer 15

Ear, tonsils, bottom to top: 1 (ear), 2 (tonsils), 3 dorsal (Bottom = inferior parathyroids), 3 ventral (To = thymus), 4 (Top = superior parathyroids).

Pouches are endoderm

Question 16

DiGeorge Syndrome

Answer 16

3rd and 4th branchial pouch issue. No thymus or parathyroid (hypocalcemia). Also associated with cardiac defects (conotruncal anomalies).

Question 17

1st branchial cleft

Answer 17

External auditory meatus

Branchial clefts are from ectoderm

Question 18

2nd-4th branchial cleft

Answer 18

form temporary cervical sinuses, which are pbliterated by proliferation of 2nd arch mesenchyme.

Branchial clefts are from ectoderm

Question 19

Anterior 2/3 of tongue formation

Answer 19

1st and 2nd branchial (pharyngeal) arch. Thus sensation via CN V3, taste via CN VII

Question 20

Posterior 1/3 of tongue formation

Answer 20

3rd and 4th branchial (pharyngeal) arch. Thus sensation and taste mainly by CN IX, extreme posterior by CN X.

Lesion of CN IX - loss of gag reflex, loss of sensation over upper pharynx, p. tongue, tonsils, middle ear cavity, loss taste sensation over posterior 1/3 tongue.

Question 21

Motor of tongue

Answer 21

CN XII to hypoglossus (retracts and depresses tongue), genioglossus (protrudes tongue), styloglossus (draws sides of tongue up to swallow).

CN X to palatoglossus - elevates posterior tongue during swallowing.

Question 22

Taste innervation for tongue

Answer 22

CN VII, IX, X (solitary nucleus)

Question 23

Pain innervation for tongue

Answer 23

CN V3, IX, X

Question 24

Motor innervation for tongue

Answer 24

CN X, XII