The Ear

• The ear contains the vestibulocochlear organ and consists of three main parts: external, middle, and internal.
• It has two functions, balance and hearing.

• The tympanic membrane (eardrum) separates the external ear from the middle ear.
• The auditory tube joins the middle ear or tympanic cavity to the nasopharynx.

Histology

Histology is the study of tissues.

A tissue is a group of cells with similar structure and function plus the extracellular substances located between the cells.

There are four basic types of tissues:

- Epitheliums

- Connective tissue

- Muscle tissue

- Nervous tissue

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.

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

Hip

Constitutes the pelvic girdle
United with the vertebral column
Union of three parts that is marked by a cup shaped cavity (acetabulum) Ilium
•    Prominence of the hip
•    Superior border is the crest
•    Anterosuperior spine-projection at the anterior tip of the crest
•    Corresponding projections on the posterior part are the posterosuperior and posteroinferior iliac spines
•    Greater sciatic notch-located beneath the posterior part
•    Most is a smooth concavity (iliac fossa)
•    Posteriorly it is rough and articulates with the sacrum in the formation of the sacroiliac joint

Pubic bone

Anterior part of the innominate bone
Symphysis pubic-joining of the two pubic bones at the midline
Body and two rami 
•    Body forms one fifth of the acetabulum
•    Superior ramis extends from the body to the median plane: superior border forms the pubic crest
•    Inferior ramus extends downward and meets with the ischium
•    Pubic arch is formed by the inferior rami of both pubic hones

Ischium
    Forms the lower and back part of the innominate bone
    Body
•    Forms two fifths of the accrabulum
•    Ischial tuberosiry-supports the body in a sitting position
•    Ramus-passes upward to join the inferior ramus of rhe pubis; known as rhe obturator foramen

Pelvis

Fanned by the right and left hip bones, sacrum, and coccyx

Greater pelvis

o    Bounded by the ilia and lower lumbar vertebrae
o    Gives support to the abdominal viscera

Lesser pelvis

o    Brim of the pelvis corresponds to the sacral promontory
o    Inferior outlet is bounded by the tip of the coccyx, ischial tuberosities, and inferior rami of the pubic bones

Female pelvis

o    Shows adaptations related to functions as a birth canal Wide outlet
o    Angle of the pubic arch is obtuse

Male pelvis

o    Shows adaptations that contribute to power and speed
o    Heart-shaped outlet
o    Angle of the pubic arch is acute

Thigh

Femur-longest and strongest bone of the body
Proximal end has a rounded head that articulates with the acetabulum
Constricted portion-the neck
Greater and lesser trochanters
Slightly arched shaft; is concave posteriorly
o    Linea aspera-strengthened by this prominent ridge
o    Site of attachment for several muscles
Distal end has two condyles separated on the posterior side by the intercondyloid notch

Knee cap

Patella-sesamoid bone
Embedded in the tendon of the quadriceps muscle
Articulates with the femur

Leg

Tibia-medial bone
o    Proximal end has two condyles that articulate with the femur
o    Triangular shaft

    Anterior-shin
    Posterior-soleal line
    Distal-medial malleolus that articulates with the latus to form the ankle joint
Fibula-lateral bone
o    Articulates with the lateral condyle of the tibia but does not enter the knee joint
o    Distal end projects as the lateral malleolus

Ankle, foot, and toes

Adapted for supporting weight but similar in structure to the hand

Talus

o    Occupies the uppennost and central position in the tarsus
o    Distributes the body weight from the tibia above to the other tarsal bones
Calcaneus (heel)-Iocated beneath the talus
Navicular-located in front of the talus on the medial side; articulates with three cuneifonn bones distally
Cuboid-lies along the lateral border of the navicular bone

Metatarsals
o    First, second, and third p1etatarsals lie in front of the three cuneifonn bones
o    (2) Fourth and fifth metatarsals lie in front of the cuboid bone

Phalanges

o    Distal to the metatarsals
o    (2) Two in the great toe; three in each of the other four toes .

Longitudinal arches in the foot (2)

o    Lateral-fonned by the calcaneus, talus, cuboid, and fourth and fifth metatarsal bones
o    Medial-fonned by the calcaneus, talus, navicular, cuneifonn, and first, second, and third metatarsal bones

Transverse arches-formed by the tarsal and metatarsal bones

->The sides and base of the skull are formed partly by these bones.
->Each bone consists of four morphologically distinct parts that fuse during development (squamous, petromastoid, and tympanic parts and the styloid process).
->The flat squamous part is external to the lateral surface of the temporal lobe of the brain.
->The petromastoid part encloses the internal ear and mastoid cells and forms part of the base of the skull.
->The tympanic part contains the bony passage from the auricle (external ear), called the external acoustic meatus. The petromastoid part also forms a portion of the bony wall of the tympanic cavity (middle ear). The meatus and tympanic cavity are concerned with the transmission of sound waves.
->The slender, pointed styloid process of the temporal bone gives attachment to certain ligaments and muscles (e.g., the stylohyoid muscle that elevates the hyoid bone).
->The temporal bone articulates at sutures with the parietal, occipital, sphenoid, and zygomatic bones.
->The zygomatic process of the temporal bone unites with the temporal process of the zygomatic bone to form the zygomatic arch. The zygomatic arches form the widest part of the face.
->The head of the mandible articulates with the mandibular fossa on the inferior surface of the zygomatic process of the temporal bone.
->Anterior to the mandibular fossa is the articular tubercle.
->Because the zygomatic arches are the widest parts of the face and are such prominent facial features, they are commonly fractured and depressed. A fracture of the temporal process of the zygomatic bone would likely involve the lateral wall of the orbit and could injure the eye.