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Anatomy

  •     Part of the axial skeleton; strong, flexible rod
        Supports the head
        Gives base to the ribs
        Encloses the spinal cord
        
    o    Vertebrae
        Consists of 34 bones composing the spinal column
    •    Cervical-7 bones
    •    Thoracic-12 bones
    •    Lumbar-5 bones
    •    Sacral- 5 bones.
    •    Coccygeal-4 to 5 bones

        In the adult the vertebrae of the sacral and coccygeal regions are united into two bones, the sacrum and me coccyx
        
    o    Curvatures-from a lateraI view there are four curves, alternately convex and concave ventrally
        Two convex curves are the cervical and lumbar
        Two concave curves are the thoracic and sacral

    o    Vertebra morphology

        Each vertebra differs in size and shape hut has similar components
        Body-central mass of bone
    •    Weight bearing
    •    Fonns anterior part of the vertebra
    •    Encloses the vertebral foramen
        Pedicles of the arch-two thick columns that extend backward from the body to meet with the laminae of the neural arch 

  •     Process (7)
    •    One spinous, two transverse, two superior articular, and two inferior articular
    o    Spinous process extends backward from the point of the union of thetwo laminae
    o    Transverse processes project laterally at either side from the junction of the lamina and the pedicle
    o    Articular processes arise near the junction of the pedicle and the lamina- superior processes project upward:inferior processes project downward
    •    Surfaces of the processes are smooth

    o    Inferior articular processes of the vertebra fit into the superior articular processes below
    o    Form true joints, but the contacts established serve to restrict movement

    Distinguishing features

    Cervical region- triangular shape

    •    All have foramina in the transverse process upper six transmit the vertebral artery
    •    Spinous processes are short
        o    C3 to C5 are bifurcated
        o    C7 is long-prominence felt at the back of the neck
    •    Have small bodies (except for C1 vertebra)
    •    C1 vertebra (atlas)
    o    No body
    o    Anterior and posterior arch and two lateral masses
    o    Superiorarticular processes articulate with the condyles of the occipital bone
    •    C2 vertebra (axis)-process on the upper surface of the body (dens) forms a pivot about which the axis rotates

    Thoracic region

    •    Presence of facets for articulation with the ribs (distinguishing feature)
    •    Processes are larger and heavier than those of the cervical region
    •    Spinous process is directed downward at a sharp angle
    •    Circular vertebral foramen

     Lumbar region
     
    •    Large and heavy bodies
    •    Four transverse lines separate the bodies of the vertebrae on the pelvic surface
    •    Triangular shape-fitted between the  halves of the pelvis
    •    Four pairs of dorsal sacral foramina communicate with four pairs of pelvic sacral foramina

    Sacral vertebrae 
    •    Five (sometimes six) vertebrae are fused in the adult to form the sacrum
    •    The sacrum articulates above with L5, laterally with the hip bones, and inferiorly with the coccyx.
    •    It has a roughly triangular appearance with a pelvic and dorsal surface, a lateral mass on each side, and a base and apex.
    •    An anesthetic for the spinal nerves may be injected extradurally through the sacral hiatus (caudal analgesia)
    •    The sacral canal (which contains the dura, cauda equina, and filum terminale) extends from the base to the sacral hiatus. 
    •    The apex of the sacrum may be fused with the coccyx.


    Coccygeal vertebrae

    •    Four to five modular pieces fused together
    •    Triangular shape with the base above and the apex below

    F Defects

    •    Lordosis-exaggerated lumbar concavity
    •    Scoliosis-lateral curvature of any region
    •    Kyphosis-exaggerated convexity in the thoracic region

 

  • The tongue is divided into halves by a medial fibrous lingual septum that lies deep to the medial groove.
  • In each half of the tongue there are four extrinsic and four intrinsic muscles.
  • The lingual muscles are all supplied by the hypoglossal nerve (CN XII).
  • The only exception is palatoglossus, which is supplied by the pharyngeal branch of the vagus nerve, via the pharyngeal plexus.

The Nasal Mucosa

  • Mucosa lines the entire nasal cavities except for the vestibule of the nose.
  • The nasal mucosa is firmly bound to the periosteum and perichondrium of the supporting structures of the nose.
  • It is continuous with the adjoining cavities to which the nasal cavity communicates (e.g., the nasopharynx and paranasal sinuses).
  • The inferior 2/3 of the nasal mucosa is called the respiratory area and air passing over this is warmed and moistened before it passes into the lungs.
  • The superior 1/3 is called the olfactory area.

The Olfactory Area of Nasal Mucosa

  • This area contains the peripheral organ of smell.
  • Sniffing draws air into this area
  • Olfactory receptor cells (from the olfactory nerve, CN I, are located in the mucosa of this area in the nose.

Nerves to the Respiratory Area of Nasal Mucosa

  • The inferior 2/3 of the nasal mucosa are supplied chiefly by the trigeminal nerve (CN V).
  • The mucous membrane of the nasal septum is supplied chiefly by the nasopalatine nerve, a branch of the maxillary nerve (CN V2).
  • Its anterior portion is supplied by the anterior ethmoidal nerve (a branch of the nasociliary nerve) which is derived from the ophthalmic nerve (CN V1).
  • The lateral walls of the nasal cavity are supplied by branches of the maxillary nerve (CN V2); the greater palatine nerve, and the anterior ethmoidal nerve.

Arteries of the Nasal Mucosa

  • The blood supply of the mucosa of the nasal septum is derived mainly from the maxillary artery.
  • The sphenopalatine artery, a branch of the maxillary, supplies most of the blood of the nasal mucosa.
  • It enters by the sphenopalatine foramen and sends branches to the posterior regions of the lateral wall and to the nasal septum.
  • The greater palatine artery, also a branch of the maxillary, passes through the incisive foramen to supply the nasal septum.
  • The anterior and posterior ethmoidal arteries, branches of the ophthalmic artery, supply the anterosuperior part of the mucosa of the lateral wall of the nasal cavity and nasal septum.
  • Three branches of the facial artery (superior labial, ascending palatine, and lateral nasal) also supply the anterior parts of the nasal mucosa.

Veins of the Nasal Mucosa

  • The veins of the nasal mucosa form a venous network of plexus in the connective tissue of the nasal mucosa.
  • Some of the veins open into the sphenopalatine vein and drain to the pterygoid plexus.
  • Others join the facial and infraorbital veins.
  • Some empty into the ophthalmic veins and drain into the cavernous sinus.

Digastric Muscle

  • Origin:
    • Anterior Belly: Digastric fossa of the mandible.
    • Posterior Belly: Mastoid notch of the temporal bone.
  • Insertion: Intermediate tendon attached to the body of the hyoid bone.
  • Nerve Supply:
    • Anterior Belly: Nerve to mylohyoid (branch of the trigeminal nerve, CN V3).
    • Posterior Belly: Facial nerve (CN VII).
  • Arterial Supply:
    • Anterior Belly: Branch of the submental artery.
    • Posterior Belly: Muscular branch of the posterior auricular artery and occipital artery.
  • Action: Raises the hyoid bone and base of the tongue, steadies the hyoid bone, and opens the mouth by lowering the mandible.

The Oral Cavity

  • The oral cavity (mouth) consists of two parts: the vestibule and the mouth proper.
  • The vestibule is the slit-like spaced between the cheeks and the lips and the teeth and gingivae.
  • It is the entrance of the digestive tract and is also used for breathing.
  • The vestibule communicates with the exterior through the orifice of the mouth.
  • The oral cavity is bounded:
  • Externally: by the cheeks and lips.
  • Roof of oral cavity: formed by the palate.
  • Posteriorly: the oral cavity communicates with the oropharynx.

Muscle

 

Emotion

 

Epicranius

 

Surprise

 

Orbicularisoculi

 

Squinting

 

Orbicularisoris

Pouting

Nasalis

 

Smelling

 

Zygomaticus

 

Smiling

 

Buccinator

 

Chewing

 

Mentalis

 

Doubt

 

Triangularis

 

Sadness

 

Platysma

 

Sadness

 

Masseter

 

Chewing

 

Temporalis

 

Sternness

 

Pterygoid

 

Conternation

 

Genioglossus and Styloglossus

 

Swallowing, Speaking, Chewing

 
 

Muscles Moving the Auditory Ossicles

The Tensor Tympani Muscle

  • This muscle is about 2 cm long.
  • Origin: superior surface of the cartilaginous part of the auditory tube, the greater wing of the sphenoid bone, and the petrous part of the temporal bone.
  • Insertion: handle of the malleus.
  • Innervation: mandibular nerve (CN V3) through the nerve to medial pterygoid.
  • The tensor tympani muscle pulls the handle of the malleus medially, tensing the tympanic membrane, and reducing the amplitude of its oscillations.
  • This tends to prevent damage to the internal ear when one is exposed to load sounds.

 

The Stapedius Muscle

  • This tiny muscle is in the pyramidal eminence or the pyramid.
  • Origin: pyramidal eminence on the posterior wall of the tympanic cavity. Its tendon enters the tympanic cavity by traversing a pinpoint foramen in the apex of the pyramid.
  • Insertion: neck of the stapes.
  • Innervation: nerve to the stapedius muscle, which arises from the facial nerve (CN VII).
  • The stapedius muscle pulls the stapes posteriorly and tilts its base in the fenestra vestibuli or oval window, thereby tightening the anular ligament and reducing the oscillatory range.
  • It also prevents excessive movement of the stapes.
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