Eye 

At week 4, two depressions are evident on each of the forebrain hemispheres.  As the anterior neural fold closes, the optic pits elongate to form the optic vesicles.  The optic vesicles remain connected to the forebrain by optic stalks. 
The invagination of the optic vesicles forms a bilayered optic cup.  The bilayered cup becomes the dual layered retina (neural and pigmented layer)
Surface ectoderm forms the lens placode, which invaginates with the optic cup.
The optic stalk is deficient ventrally to contain choroids fissure to allow blood vessels into the eye (hyaloid artery).  The artery feeds the growing lens, but will its distal portion will eventually degenerate such that the adult lens receives no hyaloid vasculature.
At the 7th week, the choroids fissure closes and walls fuse as the retinal nerve get bigger.
The anterior rim of the optic vesicles forms the retina and iris.  The iris is an outgrowth of the distal edge of the retina.
Optic vesicles induces/maintains the development of the lens vesicle, which forms the definitive lens.  Following separation of the lens vesicle from the surface ectoderm, the cornea develops in the anterior 1/5th of the eye.
The lens and retina are surrounded by mesenchyme which forms a tough connective tissue, the sclera, that is continuous with the dura mater around the optic nerve.  
Iridopupillary membrane forms to separate the anterior and posterior chambers of the eye.  The membrane breaks down to allow for the pupil
Mesenchyme surrounding the forming eye forms musculature (ciliary muscles and pupillary muscles – from somitomeres 1 and 2; innervated by CN III), supportive connective tissue elements and vasculature.

Eyelids

Formed by an outgrowth of ectoderm that is fused at its midline in the 2nd trimester, but later reopen.

Muscles of the larynx

Extrinsic muscles
    suprahyoid: raise larynx, depress mandible for swallowing
    infrahyoid: lower larynx for swallowing
    both stabilize hyoid for tongue movements

Intrinsic muscles

    all innervated by recurrent laryngeal nerve except cricothyroid: external laryngeal nerve
    adductors of vocal folds: bring folds together at midline

    Transverse and oblique arytenoids: pull arytenoids together
    Lateral cricoartenoids: spin and slide arytenoids up
    only one abductor of vocal folds
    
    Posterior cricoarytenoids—down and up
    adjustors of shape and tension of vocal folds

    Cricothyroid muscle
    
o    superficial to lateral cricoarytenoid
o    tenses vocal folds by tilting thyroid cartilage forward and sliding forward

    Thyroartenoid and vocalis muscles
    
o    vocalis: sometimes treated as medial most fibers of thyroartenoid muscle
o    different fiber directions
    
    lateral: adduct
    medial: change shape of folds
    control voice by bring bringing together different parts of folds

o    as move from epithelium to vocalis muscle, fold becomes stiffer
o    near connections, vocal folds are stiffer
o    vocal fold: complex, multilayered vibrator

The External Ear

• The auricle (L. auris, ear) is the visible, shell-like part of the external ear.
• It consists of a single elastic cartilage that is covered on both surfaces with thin, hairy skin.
• The external ear contains hairs, sweat glands, and sebaceous glands.
• The cartilage is irregularly ridged and hollowed, which gives the auricle its shell-like form.
• It also shapes the orifice of the external acoustic meatus.

The Ear Lobule

• The ear lobule (earlobe) consists of fibrous tissue, fat and blood vessels that are covered with skin.
• The arteries are derived mainly from the posterior auricular artery and the superficial temporal artery.
• The skin of the auricle is supplied by the great auricular and auriculotemporal nerves.

• The great auricular nerve supplies the superior surface and the lateral surface inferior to the external acoustic meatus with nerve fibres from C2.
• The auriculotemporal nerve supplies the skin of the auricle superior to the external acoustic meatus.

The External Acoustic Meatus

• This passage extends from the concha (L. shell) of the auricle to the tympanic membrane (L. tympanum, tambourine). It is about 2.5 cm long in adults.
• The lateral 1/3 of the S-shaped canal is cartilaginous, whereas its medial 2/3 is bony.

• The lateral third of the meatus is lined with the skin of the auricle and contains hair follicles, sebaceous glands, and ceruminous glands.
• The latter glands produce cerumen (L. cera, wax).

• The medial two-thirds of the meatus is lined with very thin skin that is continuous with the external layer of the tympanic membrane.

• The lateral end of the meatus is the widest part. It has the diameter about that of a pencil.
• The meatus becomes narrow at its medial end, about 4 mm from the tympanic membrane.
• The constricted bony part is called the isthmus.

• Innervation of the external acoustic meatus is derived from three cranial nerves:

1. The auricular branch of the auriculotemporal nerve (derived from the mandibular, CN V³).
2. The facial nerve (CN VII) by the branches from the tympanic plexus.
3. The auricular branch of the vagus nerve (CN X).

The Tympanic Membrane

• This is a thin, semi-transparent, oval membrane at the medial end of the external acoustic meatus.
• It forms a partition between the external and middle ears.
• The tympanic membrane is a thin fibrous membrane, that is covered with very thin skin externally and mucous membrane internally.

• The tympanic membrane shows a concavity toward the meatus with a central depression, the umbo, which is formed by the end of the handle of the malleus.
• From the umbo, a bright area referred to as the cone of light, radiates anteroinferiorly.

• The external surface of the tympanic membrane is supplied by the auriculotemporal nerve.
• Some innervation is supplied by a small auricular branch of the vagus nerve (CN X); this nerve may also contain some glossopharyngeal and facial nerve fibres.

The Muscles of Facial Expression

• These lie in the subcutaneous tissue and are attached to the skin of the face.
• They enable us to move our skin and change our facial expression. They produce their effects by pulling on the skin but do not move the facial skeleton.
• These muscles surround the facial orifices and act as sphincters and dilators.
• All facial muscles receive their innervation from the branches of the facial nerve (CN VII)-temporal, zygomatic, buccal, marginal mandibular, cervical.

Muscles Around the Nose

The Nasalis Muscle

• This muscle consists of a transverse (compressor naris) and alar (dilator naris) parts.
• It is supplied by the buccal branch of the facial nerve.