The Paranasal Sinuses

• These sinuses are air-filled extensions of the respiratory part of the nasal cavity.
• They are in the following bones, frontal, ethmoid, sphenoid and the maxilla.

The Frontal Sinuses

• These are located between the outer and inner tables of the frontal bone, posterior to the superciliary arches.

The Ethmoidal Sinuses

• These comprise of several small cavities, called ethmoidal air cells, within the ethmoidal labyrinth (G. labyrinthos, a maze) of the lateral mass of the ethmoid bone.

The Sphenoidal Sinuses

• These occupy a variable amount in the body of the sphenoid bone and may extend into the wings.

The Maxillary Sinuses

• These are the largest pair of paranasal sinuses.
• They are pyramidal-shaped cavities that may occupy the entire bodies of the maxillae.

Nerves of the Face

Innervation of the Muscles of Facial Expression

The Facial Nerve (CN VII)

• The seventh cranial nerve supplies the superficial muscle of the neck (platysma), the muscles of facial expression, the auricular muscles and the scalp muscles.
• CN VII is the sole motor supply to the muscles of facial expression.

• The facial nerve emerges from the skull though the stylomastoid foramen.
• Almost immediately, it enters the parotid gland. It runs superficially in this gland before giving rise to its five terminal branches: temporal, zygomatic, buccal, marginal mandibular, and cervical.
• These nerve emerge from the superior, anterior and inferior margins of the gland and spread out like the abducted digits of the hand to supply the muscles of facial expression.

• The temporal branches of CN VII cross the zygomatic arch to supply all the superficial facial muscles superior to it, including the orbital and forehead muscles.

• The zygomatic branch of CN VII passes transversely over the zygomatic bone to supply the muscles in the zygomatic, orbital and infraorbital regions.

• The buccal branches of CN VII pass horizontally, external to the masseter muscle, to supply the buccinator and the muscles of the upper lip.

• The marginal mandibular branch of CN VII supplies the muscles of the lower lip and chin.

• The cervical branch of CN VII supplies the platysma and the superficial muscles of the neck.

The Layers of the Pharyngeal Wall

• The pharyngeal wall is composed of 5 layers. From internal to external, they are as follows.

• Mucous membrane: this lines the pharynx and is continuous with all chambers with which it communicates.

• Submucosa

• Pharyngobasilar fascia: this is a fibrous layer that is attached to the skull.

• Muscular layer: this is composed of inner longitudinal and outer circular parts.

• Buccopharyngeal fascia: this is a loose connective tissue layer.
• This fascia is continuous with the fascia covering the buccinator and pharyngeal muscle.
• It contains the pharyngeal plexus of nerves and veins.

EPITHELIUMS

Epithelial Tissue Epithelial tissue covers surfaces, usually has a basement membrane, has little extracellular material, and has no blood vessels. A basement membrane attaches the epithelial cells to underlying tissues. Most epithelia have a free surface, which is not in contact with other cells. Epithelia are classified according to the number of cell layers and the shape of the cells.

• Epitheliums contain no blood vessels.  There is normally an underlying layer of connective tissue
• Almost all epitheliums lie on a basement membrane.The basement membrane consists of  a basal lamina and  reticular lamina. The reticular lamina is connected to the basal lamina by anchoring fibrils. The reticular lamina may be absent in which case the basement membrane consist only of a basal lamina. The basal lamina consists of a   - lamina densa in the middle (physical barrier) with a lamina lucida on both sides (+charge barrier),The basement membrane is absent in ependymal cells.The basement membrane is not continuous in sinusoidal capillaries.

• Epitheliums always line or cover something
• Epithelial cells lie close together with little intercellular space
• Epithelial cells are strongly connected to one another especially those epitheliums that are subjected to mechanical forces.  

Functions of Epithelium:

→ Simple epithelium involved with diffusion, filtration, secretion, or absorption

→ Stratified epithelium protects from abrasion

→ Squamous cells function in diffusion or filtration

• U-shaped bone
• Body
• Greater horn
• Lesser horn

• Suspended by ligaments from the styloid process