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58 Cards in this Set

  • Front
  • Back
How many arches are there? What are their names
Five arches. Named either pharyngeal or branchial
What's located between the arches?
Grooves or clefts externally

Pouches internally (each pouch has a ventral or dorsal wing)
Are the arches derived from mesoderm, ectoderm or endoderm?

How about the grooves and the pouches?
Arches - mesoderm (muscle, bone, vessels, cartilage)
Grooves - ectoderm
Pouches - endoderm
What are the contents of each arch?
Artery, nerve and cartilage bar
How is the nerve positioned in proximity to the arteries within the arches?
Nerves are anterior to their respective arteries, except in the 5th arch where then nerve is posterior.
How many dorsal aortas are there in early embryonic life?

Where do they fuse?
Two ventral and two dorsal.

The two ventral arteries fuse ventrally
The two dorsal arties fuse dorsally/caudally
During the couse of embryoinic development, which two arche arteries degenerate early?
First and second arch arteries degenerate
The second arch artery has an upper branch...what does it become after the artery degenerated?
The branch passes through a mass of mesoderm, which later chondrifies and ossifies as the stapes.

This stapedial artery usually degenerates during late fetal life but occasionally persists in the adult.
The third arch artery is the precursor of what?
Carotid arteries
The LEFT fourth arch artery becomes what?

How about the RIGHT?
Arch of the aorta

Proximal subclavian
The LEFT fifth arch artery becomes what?

The RIGHT fifth arch artery becomes what?
Pulmonary artery + ductus arteriosus

Pulmonary artery
What is dysphagia lusoria?
Abnormal condition characterized by difficulty in swallowing caused by aberrant right subclavian artery.

Occurs where the RIGHT 4th arch artery degenerates (which would have become the right subclavian), causing the right subclavian to arise from the dorsal aorta instead. The right subclavian becomes posterior to the esophagus, thus causing a constriction of the esophagus w/o effect on the tracha.
Describe anomalous innominate
Normally the innominate/brachiocephalic artery arises ventrally. However, if it arises too far from the left (towards midline), and anterior compression of the trachea results.
On the right side, the recurrent laryngeal nerve loops around what?

How about on the left?
Right - around the subclavian artery

Left - around the aorta & ductus arteriosus.
What are the adult derivatives of the embryologic pouches?

1st pouch
2nd pouch
3rd pouch
4th pouch
1st pouch - middle ear & external auditory canal
2nd pouch - tonsillar fossa & palatine tonsil
3rd pouch - thymus, inferior parathyroid glands (3 structures = 3rd pouch)
4th pouch - superior parathyroid glands
Which nerves are derived from the following arches?

1st arch
2nd arch
3rd arch
4th arch
5th arch
1st arch (mandibular) - CN V3
2nd arch (hyoid) - CN VII (geniculate ganglion)
3rd arch - CN IX
4th arch - Superior laryngeal nerve (CN X)
5th arch - Inferior laryngeal nerve (CN X)
Name the derivatives of the first branchial arch (no nerves)
Mandible
Head, neck, manubrium of malleus
Body & short process of incus
Anterior malleal ligament
Sphenomandibular ligament
Tensor tympani
Mastication muscles, mylohyoid
Anterior belly of digastric muscle
Tensor palati muscle
Name the derivatives of the second branchial arch (no nerves)
Manubrium of malleus
Long process of incus
All of stapes superstructure except footplate & annular ligament (vestibular portion)
Stapedial artery
Styloid process
Stylohyoid ligament
Lesser cornu of hyoid
Part of body of hyoid
Stapedius muscle
Facial muscles
Buccinator, posterior belly of digastric m.
Styloid muscle
Part of pyramidal eminence
Lower part of facial canal
Name the derivatives of the third branchial arch (no nerves)
Greater cornu of hyoid and rest of hyoid
Stylopharyngeus muscle
Superior and middle constrictors
common and internal carotid arteries.
Name the derivatives of the fourth branchial arch (no nerves)
Thyroid cartilage
Cuneiform
Inferior pharyngeal constrictors
Cricopharyngeus
Cricothyroid muscles
Aorta on the left
Proximal subclavian on the right
Name the derivatives of the fifth branchial arch (no nerves)
Cricoid
Arytenoids
Corniculate
Trachea
Intrinsic laryngeal muscles
Inferior constrictor muscle
Ductus arteriosus
What is the cause of a branchial cyst?
As the "out-pocketing" pouches develop into glandular elements, their connections withthe pharyngeal lumen, referred to as pharyngobranchial ducts, become obliterated. Should obliteration fail to occur, a branchial sinus (cyst) will result.
Where does the first branchial cleft cyst open into?
Usually originates at the angle of the mandible and extends to the EAC.
Where does the second branchial cleft cyst open into?

What is its course?
Tonsillar fossa (MOST COMMON ~ 95% of branchial cleft cysts)

- Anterior to the SCM & superficial to the 12th nerve.
- Passes typically through or superficial to the carotid sheath/bifurcation
- Superficial to the 9th nerve, pierces middle constrictor,deep to stylohyoid ligament, opens into tonsillar fossa.
Where does the third branchial cleft cyst open into?

What is its course?
pyriform sinus

-Starts similar to 2nd branchial arch - subplatysmal and opens externally anterior to the SCM.
- Superficial to the 12th nerve, deep to the internal carotid artery & 9th nerve
- Pierces the thyrohyoid membrane above the internal branch of the superior laryngeal nerve & opens into the pyriform fossa.
Where does the fourth branchial cleft cyst open into?

What is its course?
lower part of the pyriform sinus or larynx

Right side - similar to the others, subplatysmal and anterior to SCM
- Loops around the subclavian & deep to it, deep to the carotid
- Lateral to the 12th nerve, inferior to the superior laryngeal nerve
- Opens into the lower part of the pyriform sinus or into the larynx

Left side - because the 4th arch vessel is the adult aorta, the cyst may be intrathoracic, medial to the ligamentum arteriosus and the arch of the aorta.
- lateral the 12th nerve, inferior to the superior laryngeal nerve
- opens into the lower pyriform sinus or into the larynx
What's the name of the cartilage in the first arch?

What happens to the artery?
Meckel's cartilage

degenerates
What's the name of the cartilage in the second arch?

What happens to the artery?
Reichert's cartilage

the ventral second aortic arch degenerates, leaving a branch - "persistent stapedial artery"
What is the embryology of the thyroid gland?
Develops as a ventral diverticulum (endoderm) between the 1st and 2nd arches of the floor of the pharynx.

The ventral diverticulum develops into the thyroid gland, which descends caudally within the mesodermal tissues.

By 4.5 weeks, the connection between the thyroid diverticulum and the floor of the pharynx begins to disappear. By 6th week it should be obliterated & atrophied.
Embryology of the tongue

What tissue origin is it derived from?
Ectoderm (anterior 2/3rds)

Endoderm (posterior 1/3rd)
Embryology of the tongue

Describe the tongue development
At the 4th week, two lingual swellings are noted at the FIRST arch, and a swelling, the tuberculum impar, appears between the 1st & 2nd arches. These three prominences develop into the anterior 2/3rd of tongue.

Meanwhile, another swelling is noted between the 2nd & 3rd arches, called the copula. It develops into the posterior 1/3rd of tongue.

At the 7th week, the somites from high cervical areas differentiate into voluntary muscles of the tongue.

Pappillae - develop between 8-20th week.
Embryology of the tonsils & adenoids

When do the the palatine & lingual tonsils, and adenoids develop?

Which pouch/arch do they develop from?
Lingual tonsils - 6.5 weeks - between 2nd & 3d arch

Palatine tonsils - 8 weeks - from 2nd pouch

Adenoids - 16 weeks - as a subepithelial infiltration of lymphocytes
Embryology of salivary glands

When do the the parotid, submandibular and sublingual glands develop?

Which pouch do they develop from and what's the origin?
ALL are ECTOderm origin and derived from the FIRST pouch

Parotid gland - 5.5 weeks
Submandibular gland - 6 weeks
Sublingual gland - 8 weeks
Embryology of the nose

What is the origin of the nasal placode? When does it develop?
ectoderm

appears between the middle of the 3rd & 4th weeks of gestation
Embryology of the nose

What happens to the nasal placodes during the 5th week of gestation?
The placodes become depressed below the surface and appear as invaginated pits. The nasal pit extends backward into the oral cavity but is separated from it by the bucconasal membrane. This membrane ruptures at the 7th/8th week to form the posterior nares.
Embryology of the nose

Failure of the bucconasal membrane to rupture during the 7th/8th week of gestation will result in which abnormality?
Choanal atresia
Embryology of the nose

How are the anterior nares formed?
Anteriorly, the maxillary process fuses with the lateral and medial nasal processes to form the anterior nares.

The fusion between the maxillary process and the lateral nasal process also creates the nasolacrimal groove, which will formthe nasolacrimal duct.
Embryology of the nose

What is the precursor to the nasal septum?
Frontonasal process (mesoderm).

Posteriorly, the septum lies directly over the oral cavity until the 9th week, when the palatal shelves of the maxilla grow medially to fuse with each other and with the septum to form the secondary palate.
Embryology of the nose/palate

When are the hard & soft palates formed?
Hard palate - 8th/9th week

Soft palate/uvula - 11th/12th week
Embryology of the nose

What may result in aresia or setnosis of the anterior nares?
From the 8th week to the 24th week, the nostrils are occupied by an epithelial plug. Failure to resorb this epithelium results in atresia or stenosis of the anterior nares.
Embryology of the nose

In what order do the concha develop?
Inferior --> Middle --> Superior
The entire respiratory system is an outgrowth of the _________________
primitive pharynx
Summerize the embryology of the larynx
The laryngotracheal opening is the primitive laryngeal aditus and lies between the 4th & 5th arches. The sagittal slit opening is altered to become a T-shaped opening by the growth of three tissue masses.

The first is the hypobranchial eminence, which appears during the 3rd week. This mesodermal structure gives rise to the furcula, which later develops into the epiglottis. The second & third growths are two arytenoid masses, which appear during the 5th week. Later, each arytenoid swelling shows two additional swellings that eventually mature into the cuneiform and corniculate cartilages.
At which week gestation are the true and false cords formed?
Between 8th & 10th weeks
Failure of the "interarytenoid notch" to obliterate during development will cause what?
Two arytenoid masses are separated by an "interarytenoid notch", which later becomes obliterated. Results in a posterior cleft up to the cricoid cartilage, and opening into the esophagus. This is a culprit of severe aspiration in the newborn.
At which cervical vertebrae is the infant larynx situated? Adult larynx?
Infant - between 2nd & 3rd cervical vertebrae

Adult - 5th cervical vertebra
Development of the paranasal sinuses

The maxillary sinuses arise as a prolongation of what?

When does it pneumatize?

When does it reach stable size?
ethmoid infundibulum

at birth

18 yrs
Development of the paranasal sinuses

The frontal sinuses arise from what?

When does it pneumatize?

When does it reach full size?
From the upper anterior area of the middle meatus

after 1 yr

20 yrs
Development of the paranasal sinuses

The sphenoid sinuses arise from what?

When does it pneumatize?

When does it reach fullsize?
From the epithelial outgrowth of the upper posterior region of the nasal cavity in close relation with the sphenoid bone

during childhood

15 yrs
Development of the paranasal sinuses

The ethmoid sinuses arise from what?

When does it pneumatize?

When does it reach fullsize?
From the evagination of the nasal mucosa into the lateral ethmoid mass

7yrs

12yrs
Ossification of laryngeal skeleton.

When does ossification start for the following structures:

Hyoid -->
Thyroid -->
Cricoid -->
Arytenoids -->
Hyoid --> starts at birth, completed by 2yrs

Thyroid --> starts at 20-23 yrs (superior margin never ossified; extends posteriorly at each ala)

Cricoid --> starts at 25-30 yrs (incomplete; starts at inferior margin)

Arytenoids --> starts at 25-30 yrs
Embryology of the Ear

Which arches & hillocks for the auricle?
First & second arches form the six hillocks of His:

First arch (first 3 hillocks)
1) Tragus
2) Helical crus
3) Helix

Second arch (second 3 hillocks)
4) Antihelix
5) Antitragus
6) Lobule
Embryology of the Ear

Which week of gestation is the TM formed?
28th wk
Embryology of the Ear

Which week of gestation is the ossification of the inner ear complete?
23rd week
Embryology of the Ear

At age of life is the auricale and ear canal adult size?
9 yrs
Describe the four grades of microtia

Grade I
Grade II
Grade III
Grade IV
Grade I - slight deformity of pinna (EAC normal - atretic, ossicles - deformed or fixed, abnormal course of facial nerve)
Grade II - deformed cartilage framework of pinna (atresia, absent tympanic bone, small middle ear space, deformed ossicles, facial nerve anterior and lateral)
Grade III- soft tissue remnant of pinna (middle and inner ear deformities)
Grade IV - anotia (severe inner ear deformities: Shibe- collapse of cochlear duct, deformed organ of Cort; Michelle - absent inner ear)
Embryology of the Ear

What is the etiology of preauricular pits and sinuses?
Failure of complete closure of 1st & 2nd branchial arch hillock
- Incidence higher in blacks

Tx - observe unless infected
Which structures are formed from the Meckel's cartilage?

How about Reichert cartilage?
Mecke's cartilage (first branchial arch) - head & neck of the malleus, body & short process of incus; mandible,

Reichert cartilage (second branchial arch) - manubrium of malleus, long process of incus, stapes arch;