Levator Palpebrae Superioris Muscles

• This is a thin, triangular muscle that elevates the upper eyelid.
• It is continuously active except during sleeping and when the eye is closing.

• Origin: roof of orbit, anterior to the optic canal.
• Insertion: this muscle fans out into a wide aponeurosis that inserts into the skin of the upper eyelid. The inferior part of the aponeurosis contains some smooth muscle fibres that insert into the tarsal plate.
• Innervation: the superior fibres are innervated by the oculomotor nerve (CN III), and the smooth muscle component is innervated by fibres of the cervical sympathetic trunk and the internal carotid plexus.

Illnesses involving the Levator Palpebrae Superioris

• In third nerve palsy, the upper eyelid droops (ptosis) and cannot be raised voluntarily.
• This results from damage to the oculomotor nerve (CN III), which supplies this muscle.

• If the cervical sympathetic trunk is interrupted, the smooth muscle component of the levator palpebrae superioris is paralysed and also causes ptosis.
• This is part of Horner's syndrome.

The Rectus Muscles

• There are four rectus muscles (L. rectus, straight), superior, inferior, medial and lateral.

• These arise from a tough tendinous cuff, called the common tendinous ring, which surrounds the optic canal and the junction of the superior and inferior orbital fissures.
• From their common origin, these muscles run anteriorly, close to the walls of the orbit, and attach to the eyeball just posterior to the sclerocorneal junction.

• The medial and lateral rectus muscles attach to the medial and lateral sides of the eyeball respectively, on the horizontal axis.
• However, the superior rectus attaches to the anterosuperior aspect of the medial side of the eyeball while the inferior rectus attaches to the anteroinferior aspect of the medial side of the eye.

The Oblique Muscles

The Superior Oblique Muscle

• This muscle arises from the body of the sphenoid bone, superomedial to the common tendinous ring.
• It passes anteriorly, superior and medial to the superior and medial rectus muscles.
• It ends as a round tendon that runs through a pulley-like loop called the trochlea (L. pulley).
• After passing though the trochlea, the tendon of the superior oblique turns posterolaterally and inserts into the sclera at the posterosuperior aspect of the lateral side of the eyeball.

The Inferior Oblique Muscle

• This muscle arises from the maxilla in the floor of the orbit.
• It passes laterally and posteriorly, inferior to the inferior rectus muscle.
• It inserts into the sclera at the posteroinferior aspect of the lateral side of the eyeball.

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

The Laryngopharynx

• The laryngeal part of the pharynx lies posterior to the larynx.
• It extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it narrows to become continuous with the oesophagus.

• Posteriorly, the laryngopharynx is related to the bodies of C4 to C6 vertebrae.

• Its posterior and lateral walls are formed by the middle and inferior constrictor muscles, with the palatopharyngeus and stylopharyngeus internally.

• The laryngopharynx communicates with the larynx through the aditus or inlet of the larynx.
• The piriform recess is a small, pear-shaped depression of the laryngopharyngeal cavity on each side of the inlet of the larynx.

Innervation of the Skin

• Innervation of the skin is mainly through the three branches of the trigeminal nerve (CN V).
• Some skin over the angle of the mandible and anterior and posterior of the auricle is supplied by the great auricular nerve from the cervical plexus.
• Some cutaneous branches of the auricular branch of the facial nerve also supplies skin on both sides of the auricle.

• The trigeminal nerve is the general sensory nerve to the head, particularly the face, and is the motor nerve to the muscles of mastication.

The Ophthalmic Nerve

• This is the superior division of the trigeminal nerve, the smallest of the three branches and is wholly sensory.
• The ophthalmic nerve divides into three branches: the nasociliary, frontal and lacrimal just before entering the orbit through the superior orbital fissure.

• The nasociliary nerve supplies the tip of the nose through the external nasal branch of the anterior ethmoidal nerve.

• The frontal nerve is the direct continuation of CN V¹ and divides into two branches, the supraorbital and supratrochlear.
• The supratrochlear nerve supplies the middle part of the forehead.
• The supraorbital nerve supplies the lateral part and the front of the scalp.

• The lacrimal nerve, the smallest of the main ophthalmic branches, emerges over the superolateral orbital margin to supply the lacrimal gland and the lateral part of the upper eyelid.

The Maxillary Nerve

• This is the intermediate division of the trigeminal nerve.
• It has three cutaneous branches.

• The infraorbital nerve is the largest terminal branch of the maxillary nerve.
• It passes through the infraorbital foramen and breaks up into branches that supplies the skin on the lateral aspect of the nose, upper lip and lower eyelid.

• The zygomaticofacial nerve, a small branch of the maxillary, emerges from the zygomatic bone from a foramen with the same name.
• It supplies the skin over the zygomatic bone.

• The zygomaticotemporal nerve emerges from the zygomatic bone from foramen of the same name.
• It supplies the skin over the temporal region.

The Mandibular Nerve

• This is the inferior division of the trigeminal nerve.
• Of the three division of the trigeminal nerve, CN V³ is the only one that carries motor fibres (to the muscles of mastication).
• The main sensory branches of the mandibular nerve are the buccal, auriculotemporal, inferior alveolar and lingual nerves.

• The buccal nerve is a small branch of the mandibular that emerges from deep to the ramus of the mandible.
• It supplies the skin of the cheek over the buccinator muscle, the mucous membrane lining the cheek, and the buccal surface of the gingiva.

• The auriculotemporal nerve passes medially to the neck of the mandible and then turns superiorly, posterior to its head and anterior to the auricle. It then crosses over the root of the zygomatic process of the temporal bone, deep to the superficial temporal artery.

• It supplies the auricle, external acoustic meatus, tympanic membrane, and the skin in the temporal region.

• The inferior alveolar nerve is the large terminal branch of the posterior division of the mandibular nerve (the lingual nerve is the other terminal branch).
• It enters the mandible through the mandibular foramen to the mandibular canal. In the canal, it gives branches to the mandibular teeth.
• Opposite the mental foramen, this nerve divides into the mental nerve and the incisive nerve.
• The incisive nerve supplies the incisor teeth, the adjacent gingiva and the mucosa of the lower lip.
• The mental nerve emerges from the mental foramen and supplies the skin of the chin and the skin and mucous membrane of the lower lip and gingiva.

• The lingual nerve is the smaller terminal branch of the mandibular nerve.
• It supplies the general sensory fibres to the anterior two-thirds of the tongue, the floor of the mouth and the gingivae of the mandibular teeth.

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

• Suspended by ligaments from the styloid process