Walls of the Tympanic Cavity or Middle Ear

• This cavity is shaped like a narrow six-sided box that has convex medial and lateral walls.
• It has the shape of the biconcave lens in cross-section (like a red blood cell).

The Roof or Tegmental Wall

• This is formed by a thin plate of bone, called the tegmen tympani (L. tegmen, roof).
• It separates the tympanic cavity from the dura on the floor of middle cranial fossa.
• The tegmen tympani also covers the aditus ad antrum.

The Floor or Jugular Wall

• This wall is thicker than the roof.
• It separates the tympanic cavity from the superior bulb of the internal jugular vein. The internal jugular vein and the internal carotid artery diverge at the floor of the tympanic cavity.

• The tympanic nerve, a branch of the glossopharyngeal nerve (CN IX), passes through an aperture in the floor of the tympanic cavity and its branches form the tympanic plexus.

The Lateral or Membranous Wall

• This is formed almost entirely by the tympanic membrane.
• Superiorly it is formed by the lateral bony wall of the epitympanic recess.
• The handle of the malleus is incorporated in the tympanic membrane, and its head extends into the epitympanic recess.

The Medial or Labyrinthine Wall

• This separates the middle ear from the membranous labyrinth (semicircular ducts and cochlear duct) encased in the bony labyrinth.
• The medial wall of the tympanic cavity exhibits several important features.

• Centrally, opposite the tympanic membrane, there is a rounded promontory (L. eminence) formed by the first turn of the cochlea.
• The tympanic plexus of nerves, lying on the promontory, is formed by fibres of the facial and glossopharyngeal nerves.

• The medial wall of the tympanic cavity also has two small apertures or windows.

• The fenestra vestibuli (oval window) is closed by the base of the stapes, which is bound to its margins by an annular ligament.
• Through this window, vibrations of the stapes are transmitted to the perilymph window within the bony labyrinth of the inner ear.

• The fenestra cochleae (round window) is inferior to the fenestra vestibuli.
• This is closed by a second tympanic membrane.

The Posterior or Mastoid Wall

• This wall has several openings in it.
• In its superior part is the aditus ad antrum (mastoid antrum), which leads posteriorly from the epitympanic recess to the mastoid cells.

• Inferiorly is a pinpoint aperture on the apex of a tiny, hollow projection of bone, called the pyramidal eminence (pyramid).
• This eminence contains the stapedius muscle.
• Its aperture transmits the tendon of the stapedius, which enters the tympanic cavity and inserts into the stapes.

• Lateral to the pyramid, there is an aperture through which the chorda tympani nerve, a branch of the facial nerve (CN VII), enters the tympanic cavity.

The Anterior Wall or Carotid Wall

• This wall is a narrow as the medial and lateral walls converge anteriorly.
• There are two openings in the anterior wall.

• The superior opening communicates with a canal occupied by the tensor tympani muscle.
• Its tendon inserts into the handle of the malleus and keeps the tympanic membrane tense.

• Inferiorly, the tympanic cavity communicates with the nasopharynx through the auditory tube.

->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.

The Auditory Ossicles

The Malleus

• Its superior part, the head, lies in the epitympanic recess.
• The head articulates with the incus.

• The neck, lies against the flaccid part of the tympanic membrane.
• The chorda tympani nerve crosses the medial surface of the neck of the malleus.

• The handle of the malleus (L. hammer) is embedded in the tympanic membrane and moves with it.
• The tendon of the tensor tympani muscle inserts into the handle.

The Incus

• Its large body lies in the epitympanic recess where it articulates with the head of the malleus.
• The long process of the incus (L. an anvil) articulates with the stapes.
• The short process is connected by a ligament to the posterior wall of the tympanic cavity.

The Stapes

• The base (footplate) of the stapes (L. a stirrup), the smallest ossicle, fits into the fenestra vestibuli or oval window on the medial wall of the tympanic cavity.

Functions of the Auditory Ossicles

• The auditory ossicles increase the force but decrease the amplitude of the vibrations transmitted from the tympanic membrane.

The Lips

• These are mobile muscular folds that surround the mouth, the entrance of the oral cavity.

• The lips (L. labia) are covered externally by skin and internally by mucous membrane.
• In between these are layers of muscles, especially the orbicularis oris muscle.

• The upper and lower lips are attached to the gingivae in the median plane by raised folds of mucous membrane, called the labial frenula.

Sensory Nerves of the Lips

• The sensory nerves of the upper and lower lips are from the infraorbital and mental nerves, which are branches of the maxillary (CN V²) and mandibular (CN V³) nerves.

Appendicular Skeleton
Upper extremity
•    Shoulder-clavicle and scapula

Clavicle
    Articulates with the manubrium at the sternal end
    Articulates with the scapula at the lateral end
    Slender S-shaped bone that extends horizontally across the upper part of the thorax
    
Scapula

    Triangular bone with the base upward and the apex downward
    Lateral aspect contains the glenoid cavity that articulates with the head of the humerus
    Spine extends across the upper part of the posterior surface; expands laterally and
    forms the acromion (forms point of shoulder) 
    Coracoid process projects anteriorly from the upper part of the neck of the scapula
    
Arm (humerus)

Consists of a shaft (diaphysis) and two ends (epiphyses)
Proximal end has a head that articulates with the glenoid fossa of the scapula
Greater and lesser tubercles lie below the head

Intertubercular groove is located between them; long tendon of the biceps attaches here
Surgical neck is located below the tubercles

    o    Radial groove runs obliquely on the posterior surface; radial nerve is located here

    o    Deltoid muscles attaches in a V-shaped area in the middle of the shaft. called the deltoid tuberosity
    
Distal end has two projections. the medial and lateral epicondyles
Capitulum-articulates with the radius
Trochlea-articulates with the ulqa

Forearm

Radius
Lateral bone of the forearm
Radial tuberosity is located below the head on the medial side
Distal end is broad for articulation with the wrist: has a styloid process on its lateral side

Ulna

    Medial side of the forearm
    Conspicuous part of the elbow joint (olecranon)
    Curved surface that articulates with the trochlea of the humerus is the trochlearnotch
    Lateral ide is concave (radial notch); articulates with the head of the radius Distal end contains the styloid process 
    Distal end contains the styloid process

Hand

Carpal bones (8)
    Aranged in two rows of four
    Scaphoid. lunate. triquetral. and pisiform  proximal row); trapezium. trapezoid.
    capitate. and hamate (distal row)
    
Metacarpal bones (5)
    Framework of the hand
    Numbered 1 to 5 beginning on the lateral side
    
Phalanges (14)
    Fingers
     Three phalanges in each finger; two phalanges in the thumb

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.