Repro - Embryology (Aortic/Branchial derivatives & Cleft lip/palate) Flashcards
Pg. 558-560 in First Aid 2014 Sections include: -Aortic arch derivatives -Branchial apparatus -Branchial cleft derivatives -Branchial arch derivatives -Branchial pouch derivatives -Cleft lip and cleft palate
Into what do aortic arch derivatives develop?
Develop into the arterial system
What is derived from the 1st aortic arch? Of what major vessel is this a branch?
Part of maxillary artery (branch of external carotid); Think: “1st arch is MAXimal”
What is derived from the 2nd aortic arch?
Stapedial artery and Hyoid artery; Think: “Second = Stapedial”
What is derived from the 3rd aortic arch?
Common Carotid artery and proximal part of internal Carotid artery; Think: “C is 3rd letter of alphabet”
What is derived from the 4th aortic arch?
On left, aortic arch; on right, proximal part of right subclavian artery; Think: “4th arch (4 limbs) = systemic”
What is derived from the 6th aortic arch?
Proximal part of pulmonary arteries and (on left only) ductus arteriosus; Think: “6th arch = pulmonary and the pulmonary-to-systemic shunt (ductus arteriosus)”
How do right and left recurrent laryngeal nerves relate to the aortic arch?
See p. 558 in First Aid 2014 for visual
What is another name for the branchial apparatus? What are its 3 components?
Also called pharyngeal apparatus; Composed of branchial clefts, arches, and pouches
From what germ layer are branchial clefts derived?
Derived from ectoderm
What is another name for branchial clefts?
Also called branchial grooves
From what 2 embyrological origins are branchial arches derived? What are 2 examples of each source?
Derived from mesoderm (muscles, arteries) and neural crest (bones, cartilage)
From what germ layer are branchial pouches derived?
Derived from endoderm
List the components of the branchial apparatus from outside to inside. What germ layer gives rise to each?
Clefts = ectoderm, Arches = mesoderm, Pouches = endoderm; Think: “CAP covers outside to inside”
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.
See p. 558 in First Aid 2014 for visual near bottom right of page
Into what does the 1st branchial cleft develop?
1st cleft develops into external auditory meatus
What do the 2nd through 4th clefts form? What is the fate of this (these) structure(s), and what causes this?
2nd through 4th clefts form temporary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme
What abnormality does a persistent cervical sinus cause, and where?
Persistent cervical sinus => branchial cleft cyst within lateral neck
To what kind of cartilage does the 1st branchial arch give rise? What are 3 structures that result?
Meckel cartilage: (1) Mandible (2) Malleus (3) spheno-Mandibular ligament; Think: “M’s (also like most of its muscle derivatives)”
To what 8 muscle derivatives does the 1st branchial arch give rise?
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)
To what 2 nerve derivatives does the 1st branchial arch give rise?
CN V2 and V3; Think: “chew (like Muscles of Mastication)”
What abnormality is associated with 1st branchial arch? What causes this? What 2 symptoms/signs result?
Treacher Collins syndrome: 1st-arch neural crest fails to migrate => (1)mandibular hypoplasia, (2) facial abnormalities
To what kind of cartilage does the 2nd branchial arch give rise? What are 4 structures that result?
Reichert cartilage: (1) Stapes (2) Styloid process (3) lesser horn of hyoid (4) Stylohyoid ligament; Think: “S’s (also most of muscle derivatives)”
To what 5 muscles does the 2nd branchial arch give rise?
(1) Muscles of facial expression, (2) Stapedius, (3) Stylohyoid, (4) platySma, (5) belly of diastric; Think: “S’s (also most of cartilage derivatives)”
To what nerve does the 2nd branchial arch give rise?
CN VII (facial expression); Think: “smile (like S’s of most cartilage and muscle derivatives)
What abnormality is associated with the 2nd branchial arch? What causes this disorder? What symptom/sign results, and where?
Congenital pharyngo-cutaneous fistula: persistence of cleft and pouch => fistula between tonsilar area and lateral neck
To what cartilage does the 3rd branchial arch give rise?
Cartilage: greater horn of hyoid
To what muscle does the 3rd branchial arch give rise?
Stylopharyngeus; Think: “styloPHARYNGEUS innervated by glossoPHARYNGEAL nerve”
To what nerve does the 3rd branchial arch give rise?
CN IX; Think: “STYLOpharygeus SWALLOW STYLishly”
To what 5 cartilages do the 4th through 6th arches?
Cartilages: (1) Thyroid, (2) Cricoid, (3) Arytenoids, (4) Corniculate, (5) Cuneiform
To what 3 muscles does the 4th branchial arch give rise?
4th arch: (1) most pharyngeal constrictors; (2) cricothyroid, (3) levator veli palatini
To what muscles does the 6th branchial arch give rise?
6th arch: all intrinsic muscles of larynx except cricothyroid
To what nerve does the 4th branchial arch give rise?
4th arch: CN X (superior laryngeal branch); Think: “SIMPLY SWALLOW”
To what nerve does the 6th branchial arch give rise?
6th arch: CN X (recurrent laryngeal branch); Think: “SPEAK”
What body part do the 3rd and 4th branchial arches form? Be specific.
Arches 3 and 4 form posterior 1/3 of tongue
What is derived from the 5th branchial arch?
Arch 5 makes no major development contributions
What do the nerves derived from branchial arches have in common? What is the exception?
These are the only CNs with both motor and sensory components (except V2, which is sensory only)
To what nerve(s) does each branchial arch give rise?
(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).”
Into what 3 structures does the 1st branchial pouch develop? What embryologic similarity do these derivatives of the 1st branchial pouch have?
Develops into middle ear cavity, eustachian tube, mastoid air cells; 1st pouch contributes to endoderm-lined structures of ear
Into what does the 2nd branchial pouch develop?
Develops into epithelial lining of palantine tonsil
To what 2 major divisions does the 3rd branchial pouch give rise? To what structures does each of these give rise?
(1) DORSAL WINGS - develops into the INFERIOR parathyroids (2) VENTRAL WINGS - develops into thymus
To how many structures does the 3rd branchial pouch give rise, and which ones?
3rd pouch contributes to 3 structures (thymus, left and right inferior parathyroids)
To what major division does the 4th branchial pouch give rise? To what structure does this give rise?
DORSAL WINGS - develops into the SUPERIOR parathyroids
Which branchial pouches give rise to the dorsal wings? Given this, into which dorsal wing structures does each of these branchial pouches develop?
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”
To what major derivatives does each of the branchial pouches give rise?
1 (ear), 2 (tonsils), 3 dorsal (bottom for interior parathyroids), 3 ventral (to = thymus), 4 (top = superior parathyroids); Think: “Ear, tonsils, bottom-to-top”
What is (are) the embryologic defect(s) in DiGeorge syndrome? What 2 conditions result? What other kind of conditions is associated with DiGeorge syndrome?
Aberrant development of 3rd and 4th pouches => T-cell deficiency (thymic aplasia) and hypocalcemia (failure of parathyroid development). Associated with cardiac defects (conotruncal anomalies)
What causes MEN2A syndrome?
Mutation of germline RET (neural crest cells)
What are 3 manifestations of MEN2A syndrome? Give embryologic origins where applicable.
(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
What causes cleft lip?
Cleft lip - Failure of fusion of the maxillary and medial nasal processes (formation of primary palate)
What are 2 potential causes of cleft palate?
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)
How are cleft lip and cleft palate related, if at all?
Cleft lip and cleft palate have two distinct etiologies, but often occur together
