->The two parietal bones (L. paries, wall) form large parts of the walls of the calvaria.
->On the outside of these smooth convex bones, there are slight elevations near the centre called parietal eminences.
->The middle of the lateral surfaces of the parietal bones is crossed by two curved lines, the superior and inferior temporal lines.
->The superior temporal line indicates an attachment of the temporal fascia; the inferior temporal line marks the superior limit of the temporalis muscle.
->The parietal bones articulate with each other in the median plane at the sagittal suture. The medial plane of the body passes through the sagittal suture.
->The inverted V-shaped suture between the parietal bones and the occipital bones is called the lambdoid suture because of its resemblance to the letter lambda in the Greek alphabet.
->The point where the parietal and occipital bones join is a useful reference point called the lambda. It can be felt as a depression in some people.
->In addition to articulation with each other and the frontal and occipital bones, the parietal bones articulate with the temporal bones and the greater wings of the sphenoid bone.
->In foetal and infant skulls, the bones of the calvaria are separated by dense connective tissue membranes at sutures.
->The large fibrous area where several sutures meet are called fonticuli or fontanelles.
->The softness of these bones and looseness of their connections at these sutures enable the calvaria to undergo changes of shape during birth called molding. Within a day or so after birth, the shape of the infant’s calvaria returns to normal.
->The loose construction of the new-born calvaria also allows the skull to enlarge and undergo remodelling during infancy and childhood.

->Relationships between the various bones are constantly changing during the active growth period.
->The increase in the size of the cranium is greatest during the first 2 years, the period of most rapid postnatal growth of the brain.
->The cranium normally increases in capacity until about 15 or 16 years of age; thereafter the cranium usually increases only slightly in size as its bones thicken for 3 to 4 years.

Genioglossus Muscle

• Origin: Mental spine of the mandible.
• Insertion: Dorsum of the tongue and hyoid bone.
• Nerve Supply: Hypoglossal nerve (CN XII).
• Arterial Supply: Sublingual and submental arteries.
• Action: Depresses and protrudes the tongue.

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

Blood Supply to the Head and Neck

• Most arteries in the anterior cervical triangle arise from the common carotid artery or one of the branches of the external carotid artery.
• Most veins in the anterior cervical triangle are tributaries of the large internal jugular vein.

The Common Carotid Arteries

• The right common carotid artery begins at the bifurcation of the brachiocephalic trunk, posterior to the right sternoclavicular joint.
• The left common carotid artery begins arises from the arch of the aorta and ascends into the neck, posterior to the left sternoclavicular joint.

• Each common carotid artery ascends into the neck within the carotid sheath to the level of the superior border of the thyroid cartilage.
• Here it terminates by dividing into the internal and external carotid arteries. 

The Internal Carotid Artery

• This is the direct continuation of the common carotid artery and it has no branches in the neck.
• It supplies structures inside the skull.
• The internal carotid arteries are two of the four main arteries that supply blood to the brain.

• Each artery arises from the common carotid at the level of the superior border of the thyroid cartilage.
• It then passes superiorly, almost in a vertical plane, to enter the carotid canal in the petrous part of the temporal bone.

• A plexus of sympathetic fibres accompany it.

• During its course through the neck, the internal carotid artery lies on the longus capitis muscle and the sympathetic trunk.
• The vagus nerve (CN X) lies posterolateral to it.

• The internal carotid artery enters the middle cranial fossa beside the dorsum sellae of the sphenoid bone.
• Within the cranial cavity, the internal carotid artery and its branches supply the hypophysis cerebri (pituitary gland), the orbit, and most of the supratentorial part of the brain. 

The External Carotid Arteries 

• This vessel begins at the bifurcation of the common carotid, at the level of the superior border of the thyroid cartilage.
• It supplies structures external to the skull.

• The external carotid artery runs posterosuperiorly to the region between the neck of the mandible and the lobule of the auricle.
• It terminates by dividing into two branches, the maxillary and superficial temporal arteries.
• The stems of most of the six branches of the external carotid artery are in the carotid triangle. 

The Superior Thyroid Artery

• This is the most inferior of the 3 anterior branches of the external carotid.
• It arises close to the origin of the vessel, just inferior to the greater horn of the hyoid.
• The superior thyroid artery runs anteroinferiorly, deep to the infrahyoid muscles and gives off the superior laryngeal artery. This artery pierces the thyrohyoid membrane in company with the internal laryngeal nerve and supplies the larynx.

The Lingual Artery

• This arises from the external carotid artery as it lies on the middle constrictor muscle of the pharynx.
• It arches superoanteriorly, about 5 mm superior to the tip of the greater horn of the hyoid bone, and then passes deep to the hypoglossal nerve, the stylohyoid muscle, and the posterior belly of digastric muscle.

• It disappears deep to the hyoglossus muscle.
• At the anterior border of this muscle, it turns superiorly and ends by becoming the deep lingual artery.

The Facial Artery

• This arises from the carotid artery either, in common with the lingual artery, or immediately superior to it.
• In the neck the facial artery gives off its important tonsillar branch and branches to the palate and submandibular gland.
• The facial artery then passes superiorly under the cover of the digastric and stylohyoid muscles and the angle of the mandible.

• It loops anteriorly and enters a deep groove in the submandibular gland.

• The facial artery hooks around the inferior border of the mandible and enters the face. Here the pulsation of this artery can be felt (anterior to the masseter muscle).

The Ascending Pharyngeal Artery

• This is the 1^st or 2^nd branch of the external carotid artery.
• This small vessel ascends on the pharynx, deep to the internal carotid artery.
• It sends branches to the pharynx, prevertebral muscles, middle ear and meninges.

The Occipital Artery

• This arises from the posterior surface of the external carotid near the level of the facial artery.
• It passes posteriorly along the inferior border of the posterior belly of digastric.
• It ends in the posterior part of the scalp.
• During its course, it is superficial to the internal carotid artery and three cranial nerves (CN IX, CN X and CN XI).

The Posterior Auricular Artery

• This is a small posterior branch of the external carotid artery.
• It arises from it at the superior border of the posterior belly of the digastric muscle.
• It ascends posteriorly to the external acoustic meatus and supplies adjacent muscles, the parotid gland, the facial nerve, structures in the temporal bone, the auricle, and the scalp. 

The Internal Jugular Vein

• This is usually the largest vein in the neck.
• The internal jugular vein drains blood from the brain and superficial parts of the face and neck.
• Its course corresponds to a line drawn from a point immediately inferior to the external acoustic meatus to the medial end of the clavicle.

• This large vein commences at the jugular foramen in the posterior cranial fossa, as the direct continuation of the sigmoid sinus.

• The dilation at its origin is called the superior bulb of the internal jugular vein.
• From here it runs inferiorly through the neck in the carotid sheath.

• The internal jugular vein leaves the anterior triangle of the neck by passing deep to the SCM muscle.
• Posterior to the sternal end of the clavicle, it unites with the subclavian vein to form the brachiocephalic vein.
• Near its termination is the inferior bulb of the jugular vein contains a bicuspid valve similar to that of the subclavian vein.

• The deep cervical lymph nodes lie along the course of the internal jugular vein, mostly lateral and posterior.

Tributaries of the Internal Jugular Vein

• This large vein is joined at its origin by the: inferior petrosal sinus, the facial, lingual, pharyngeal, superior and middle thyroid veins, and often the occipital vein.

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 Sublingual Glands

• These are the smallest of the three paired salivary glands and the most deeply situated.
• They are almond-shaped and lie in the floor of the mouth between the mandible and the genioglossus muscle.
• The paired glands unite to form a horseshoe-shaped glandular mass around the lingual frenulum.

• Numerous small ducts (10 to 12) open into the floor of the mouth.
• Sometimes one of the ducts opens into the submandibular duct.

• The nerves the accompany the submandibular and sublingual glands are derived from the lingual and chorda tympani nerves and from the sympathetic nerves.
• The parasympathetic secretomotor fibres are from the submandibular ganglion.