Lecture Tuesday October 2: embryology face, eye and palate

A. Development of the Face

- Frontonasal prominence > forehead, bridge of nose, medial and lateral nasal prominences
- Medial nasal prominence > tip of nose and philtrum of lip
- Lateral nasal prominence > algae of nose
- Maxillary process > cheeks and lateral portion of upper lip
- Mandibular process > lower lip




Clinical correlation:
Cleft lip is the failure of the maxillary process and medial nasal process to fuse correctly. Can be unilateral or bilateral and involve the palate or not.








B. Development of the Eye

Early in the 4th week optic vesicles extend from the wall of the forebrain. As the vesicle reaches the surface ectoderm it flattens and invaginates to form the optic cup, which remains attached to the forebrain by the optic stalk (precursor of the optic nerve). Its presence induces the formation of the lens placode from the surface ectoderm.








The lens placode invaginates and (eventually) separates from the ectoderm to form the lens vesicle.




The primary optic vesicle becomes a double walled optic cup. With continued invagination the original lumen of the optic vesicle is reduced to a slit between the inner neural layer (future retina) and outer pigmented layer (future pigmented epithelium) of the optic cup.




Mesenchyme around the optic cup will contribute to the cornea and sclera and the extraocular muscles.

C. Development of the Palate

1. The medial nasal processes merge with the maxillary processes to form the upper lip and primary palate by the end of the sixth week.
2. The secondary palate develops as bilateral outgrowths from the maxillary processes, which grow vertically down the side of the tongue. Subsequently, the palatal shelves elevate to a horizontal position above the tongue, contact one another and fuse. Fusion of the palatal shelves ultimately divides the oronasal space into separate oral and nasal cavities.




Clinical Correlation:
Cleft palate- An orofacial cleft occurs when parts of the lip or palate do not completely fuse together during the first 3 months of pregnancy. A cleft lip may appear as a small notch in the edge of the lip only or extend into the nose. It may also extend into the gums.
A cleft palate may also vary in size, from a defect of the soft palate only to a complete cleft that extends through the hard palate. Because the lips and the palate develop separately, it is possible for a child to be born with a cleft lip only, cleft palate only, or both.




- Posted using BlogPress from my iPad

Lecture Monday October 1: Deep Face, Orbit, Nasal and Oral Cavities

A. Eye and Orbit
**See handout on clinical testing of eye muscles. This handout includes all of the information you will need on the muscles, movements and innervation (III, IV and VI)

B. Muscles of Mastication
- Temporalis (close mouth)
- Masseter (close mouth)
- Medial pterygoid (close mouth)
- Lateral pterygoid (opens mouth)
*All innervated by branches of V3

C. Major branches of V3 in the infratemporal fossa:
1. Deep temporal (motor to Temporalis)

2. Buccal (sensory to the inside of the cheek)

3. Auriculotemporal (sensory to the side of the head posterior to the ear, carries postganglionic parasympathetic fibers from otic ganglion to parotid)

4. Lingual (sensory to anterior 2/3 of the tongue, associated with chorda tympani branch of VII that carries taste from anterior 2/3 of tongue and parasympathetics to submandibular ganglion)

5. Inferior alveolar (sensory to mandibular teeth, ends as mental nerve)

D. Oropharynx
- palatoglossal arch anterior and continuous with uvula
- palatopharyngeal arch posterior
- palatine tonsil in between the two arches




E. Tongue
- Extrinsic muscles:
Genioglossus (primary muscle that protrudes the tongue)
Hyoglossus
Styloglossus
Palatoglossus
*All innervated by cranial nerve XII except palatoglossus (X)

F. Nasal Cavities and Sinuses
- Lateral wall structures: Superior, middle and inferior choncha.
- Lateral wall spaces: superior, middle and inferior meatus. Sphenoethmoidal recess.

Blood Supply via the sphenopalatine A. (continuation of maxillary A.) and branches of the facial artery.

Sensory Innervation via the Ophthalmic (V1) to the nasal vestibule and the Maxillary (V2) to the posterior nasal cavity and nasopharynx.

Paranasal Sinuses:
- Frontal (drains to middle meatus via the infundibulum in hiatus semilunaris)
- Ethmoidal (anterior/middle drain to middle meatus; posterior drains to superior meatus)
- Maxillary (drains to middle meatus via hiatus semilunaris)
- Sphenoid (drains to sphenoethmoidal recess)




- Posted using BlogPress from my iPad

Lecture Tuesday September 25: head and neck embryology I

A. Pharyngeal Arches
Be able to identify the pharyngeal arches in a picture or drawing of an embryo and what things are derived from them.



Arch 1: muscles of mastication. malleus and incus of the ear. Innervation by V3

Arch 2: muscles of facial expression. stapes, styloid process and upper part of hyoid bone. Innervation by VII.

Arch 3: stylopharyngeus muscle. lower part of hyoid bone. Innervation by IX.

Arches 4 and 6: muscles of pharynx, larynx and upper esophagus. thyroid and cricoid cartilage. Innervation by X.

B. Pharyngeal Pouches
Be able to identify the pharyngeal pouches in a picture or drawing of an embryo and what things are derived from them.

1st pharyngeal pouch: the tympanic cavity and auditory tube. The endoderm of this pouch will fuse to the ectoderm of the 1st pharyngeal cleft to form the tympanic membrane.

2nd pharyngeal pouch: palatine tonsil.

3rd pharyngeal pouch: inferior parathyroid gland and thymus.

4th pharyngeal pouch: superior parathyroid and the parafollicular (C) cells of the thyroid.



C. Tongue

Develops from swellings on the inner surface of the pharyngeal arches. The pharyngeal arch of origin predicts the sensory innervation of the tongue
- anterior 2/3 from arch 1 = Cn V3
- posterior 1/3 from arch 3 = Cn IX
- root of tongue and epiglottis from arch 4 = Cn X





D. Thyroid
The thyroid gland develops in the ventral midline between the 1st and 2nd pharyngeal arches at the foramen cecum. It is connected to the developing surface of the tongue by the thyroglossal duct.

The thyroid migrates caudally while maintaining its thyroglossal duct connection to the tongue. Over time, the thyroglossal duct degenerates. Remnants of the duct might persist as thyroglossal cysts. These cysts are always in the ventral midline in the neck. In addition, ectopic thyroid tissue might be found anywhere along the developmental migratory path of the thyroid.






E. Ear
- Otic pit > otic vesicle > membranous labyrinth of inner ear.
- pharyngeal arches 1 and 2 > middle ear ossicles
- endodermal pouch 1 > auditory tube




- Posted using BlogPress from my iPad

Lecture Monday September 24: Anatomy of the Neck, Pharynx and Larynx

Cervical Spine
- Rotation occurs at C1 and C2
- Vertebral artery runs superiorly through the transverse processes to enter the foremen magnum.

Posterior Triangle of the Neck
SCM is anterior border and trapezius is the posterior border.
Anterior, middle and posterior scalene muscles in the floor. Brachial plexus present between anterior and middle.
Clinical problems:
1. Compression of brachial plexus with resulting nerve problems of the upper limb
2. Torticollis from tight/contracted SCM on one side

Cervical plexus (anterior rami of C1-C4)
Sensory nerves:
- transverse cervical (C2-C3)
- lesser occipital (C2)
- great auricular (C2-C3)
- supraclavicular (C3-C4)
Motor nerves:
- Ansa cervicalis (C1-C3)
- phrenic (C3-C5)



Muscles of the Anterior Triangle
2 Groups above and below the hyoid bone:
Suprahyoid - innervated by either Cranial nerve V or VII
Infrahyoid - innervated by nerves of the cervical plexus C1 or ansa cervicalis

External Carotid artery branches
1. Superior thyroid
2. Ascending pharyngeal
3. Lingual
4. Facial
5. Occipital
6. Maxillary
7. Superficial temporal


Hypoglossal Nerve
Motor to the muscles of the tongue

Vagus Nerve in the Neck (remember pharynx, larynx and palate)
1. Recurrent laryngeal nerve
Motor to muscles of the larynx and sensory to the mucosa of the larynx below the vocal folds

2. Superior laryngeal nerve
- internal laryngeal branch is sensory to the mucosa of the larynx above the vocal folds
- external laryngeal branch is motor to the cricothyroid muscle



- Posted using BlogPress from my iPad

Lecture Wednesday September 19: histology of the ear

Basic Ear Anatomy



- Relationship of middle ear ossicles to the inner ear
Sound waves vibrate the tympanic membrane > vibrates the oval window > fluid wave through the cochlea > wave exits (dampened) at the round window



Histology of the Cochlea
Components:
A. 3 ducts: scala vestibuli, scala tympani, and cochlear duct
B. 3 membranes: vestibular, basilar and tectorial
C. Hair cells in the organ of corti
D. Spiral ganglion (CN VIII)


Displacement of perilymph in the scala vestibuli will bend the vestibular membrane > displaces the endolymph in the cochlear duct > bends the basilar membrane.
Movement of the basilar membrane to which the hair cells are attached cause bending of the hair cell processes embedded in the tectorial membrane > depolarization of the hair cells > depolarization of CN VIII at spiral ganglion.


- Posted using BlogPress from my iPad

Lecture Wednesday September 19: histology of the eye

Recognize the basic anatomy of the eye



1. Cornea
3 main layers from outside in: corneal epithelium, stroma, corneal endothelium



2. Sclera
Irregular connective tissue

3. Choroid
Vascularized connective tissue
Anteriorly forms:
- Ciliary Body (ciliary process produces aqueous humor, and ciliary muscle that functions to change the shape of the lens).
- Iris contains constrictor papillae muscle (parasympathetic CN III) and dilator pupillae muscle (sympathetic)
- scleral venous sinus (canal of Schlemm) for drainage of aqueous humor produced by the ciliary body



4. Retina and Pigmented Epithelium

Pigment epithelium important for recycling products of the rods and cones

Layers of the retina


1. Outer nuclear layer = Rods and Cones that depolarize in response to light stimulation
2. Outer plexiform layer = processes of rods and cones that synapse on the cells of the inner nuclear layer
3. Inner nuclear layer = several types of neurons that process the information from the rods and cones
4. Inner plexiform layer = processes of neurons from the inner nuclear layer that synapse on the ganglion cells.
5. Ganglion cell layer = neurons whose axons give rise to the optic nerve.
6. Nerve fiber layer = axons of the ganglion cells

Clinical correlations
1. Cataract - clouding of the lens
2. Glaucoma - Increased ocular pressure due to blockage of aqueous humor drainage through the scleral venous sinus (canal of schlemm)
3. Papilledema- bulging of the optic disc due to increased intracranial pressure.


- Posted using BlogPress from my iPad

Lecture Tuesday September 18: cranial cavity and superficial face

Characterizing Types of Hematomas
1. Epidural
-between skull and dura
- arterial bleed (usually middle meningeal)
- shaped like a biconvex lens in a CT scan




2. Subdural
- between the dura and arachnoid
- venous bleed (bridging veins that cross the Subdural space)
- crescent shaped in a CT scan




3. Subarachnoid
- bleeding into subarachnoid space
- usually from a ruptured arterial aneurysm
- diffuse blood in the subarachnoid space within the brain parenchyma. Blood in the CSF




Innervation of the Parotid Gland

1. Parasympathetic
- Preganglionic fibers (lesser petrosal nerve) synapse in the Otic Ganglion
- Postganglionic fibers run with the auriculotemporal branch of V3 to the parotid gland
- cause secretion from the gland

2. Sympathetic
- Preganglionic fibers from T1-T3 spinal cord synapse in the superior cervical ganglion.
- Postganglionic fibers follow blood vessels to parotid.
- regulate blood flow (some controversy about secretion, may contribute at some minor level).



- Posted using BlogPress from my iPad