G. Anatomy

• Orbit


  • Pyramidal cavity with base in front and apex behind
  • Orbital margin formed by frontal, zygomatic, maxilla bones
  • Roof formed by orbital plate of frontal bone
  • Lateral wall formed by zygomatic and sphenoid bones
  • Floor formed by orbital plate of maxilla
  • Medial wall formed by maxilla, lacrimal, ethmoid, sphenoid bones

  
• Openings into orbital cavity


  • Orbital opening
  • Supraorbital notch (foramen)
  • Infraorbital groove and canal
  • Nasolacrimal canal
  • Inferior orbital fissure
  • Superior orbital fissure
  • Optic canal
• External nose


  • Elliptical nostrils separated by nasal septum
  • Lateral margin (ala nasi) rounded and mobile
  • Framework formed by nasal bones, frontal processes of maxillae, nasal part of frontal bone above, hyaline cartilage below

  
• Nasal cavity


  • Extends from nostrils to posterior nasal apertures (choanae)
  • Divided into right and left halves by nasal septum
  • Floor formed by palatine process of maxilla and horizontal plate of palatine bone
  • Roof formed by nasal and frontal bones anteriorly, cribriform plate of ethmoid in middle, body of sphenoid posteriorly
  • Lateral wall has superior, middle, and inferior nasal conchae with meatuses below
  • Medial wall formed by nasal septum

  
• Paranasal sinuses


  • Cavities in maxilla, frontal, sphenoid, ethmoid bones
  • Lined with mucoperiosteum and filled with air
  • Communicate with nasal cavity through small apertures

  
• Paranasal sinuses and their drainage sites

  • Maxillary sinus - Middle meatus through hiatus semilunaris
  • Frontal sinuses - Middle meatus via infundibulum
  • Sphenoidal sinuses - Sphenoethmoidal recess
  • Anterior ethmoid sinuses - Infundibulum and middle meatus
  • Middle ethmoid sinuses - Middle meatus on/above bulla ethmoidalis
  • Posterior ethmoid sinuses - Superior meatus
• Malleus


  • Largest ossicle with head, neck, long process/handle, anterior process, lateral process
  • Head articulates with incus
  • Handle attached to tympanic membrane
• Incus


  • Has body and two processes
  • Body articulates with malleus
  • Long process articulates with stapes
• Stapes


  • Has head, neck, two limbs, base
  • Head articulates with incus
  • Neck receives insertion of stapedius muscle
  • Limbs attached to oval base
  • Base attached to fenestra vestibuli by annular ligament

  
• Hyoid bone


  • U-shaped bone in neck between larynx and mandible
  • Has anterior body and two greater horns projecting posteriorly and superiorly
  • Two lesser horns where greater horns join body
  • Stylohyoid ligaments attach to lesser horns
  • Connects floor of oral cavity to pharynx and larynx

  
• Vertebral column


  A vertical series of approximately 33 small bones (known as vertebrae), which are separated by intervertebral discs

  
• Vertebral column


  • Can be divided into five different regions, each region characterized by a different vertebral structure
  • Has four main functions: Protection, Support, Axis, Movement

  
• Vertebrae


  Consist of a vertebral body, situated anteriorly, and a posterior vertebral arch

  
• Vertebral body


  The anterior part of the vertebrae, it is the weight-bearing component, and it's size increases as the vertebral column descends

  
• Vertebral arch


  The lateral and posterior parts of the vertebrae, with the vertebral body, the vertebral arch forms an enclosed hole called a vertebral foramen

  
• Thorax


  The part of the body between the neck and the abdomen
• Bony prominences of the vertebral arch


  • Pedicles
  • Lamina
  • Transverse processes
  • Articular processes
  • Spinous processes

  
• Cervical vertebrae


  • Have a bifid spinous process
  • Have two transverse foramina
  • Have a triangular shaped vertebral foramen

  
• Structure of the thoracic wall


  • Covered on the outside by skin and muscles attaching the shoulder girdle to the trunk
  • Lined with parietal pleura
  • Formed posteriorly by the thoracic part of the vertebral column
  • Formed anteriorly by the sternum and costal cartilages
  • Formed laterally by the ribs and intercostal spaces
  • Formed superiorly by the suprapleural membrane
  • Formed inferiorly by the diaphragm, which separates the thoracic cavity from the abdominal cavity

  
• Cervical vertebrae C1 and C2


  • Are specialized to allow for the movement of the head

  
• Sternum


  A flat bone in the midline of the anterior chest wall, divided into three parts: manubrium sterni, body of the sternum, and xiphoid process

  
• Cervical vertebrae C7


  • Have a much longer spinous process, which does not bifurcate
• Manubrium


  • The upper part of the sternum, articulating with the body of the sternum at the manubriosternal joint, and also articulating with the clavicles and with the first costal cartilage and the upper part of the second costal cartilages on each side, lying opposite the third and fourth thoracic vertebrae

  
• Thoracic vertebrae


  • Have two "demi facets" on each side of the vertebral body which articulate with the head of the respective rib, and the rib inferior to it
  • Have a costal facet on the transverse processes for articulation with the respective "tubercle of the rib"
  • Have spinous processes that are slanted inferiorly and anteriorly
  • Have a circular vertebral foramen

  
• Body of the sternum


  • Articulates above with the manubrium at the manubriosternal joint and below with the xiphoid process at the xiphisternal joint, articulating on each side with the 2nd to the 7th costal cartilages

  
• Lumbar vertebrae


  • Have very large vertebral bodies, which are kidney-shaped
  • Lack transverse foramina, costal facets, or bifid spinous processes
  • Have a triangular shaped vertebral foramen

  
• Xiphoid process


  • A thin plate of cartilage that becomes ossified at its proximal end during adult life, with no ribs or costal cartilages attached to it
• Sacrum


  A collection of five fused vertebrae, described as an upside down triangle, with the apex pointing inferiorly

  
• Sternal angle (angle of Louis)


  Formed by the articulation of the manubrium with the body of the sternum, recognized by a transverse ridge on the anterior aspect of the sternum at the level of the second costal cartilage, the point from which all costal cartilages and ribs are counted, lying opposite the intervertebral disc between the 4th and 5th thoracic vertebrae

  
• Coccyx


  A small bone, which articulates with the apex of the sacrum, it is recognized by it's lack of vertebral arches

  
• Xiphisternal joint


  Lies opposite the body of the 9th thoracic vertebra

  
• The coccyx is formed of either three, four or five rudimentary vertebrae

  
• Types of ribs


  • True ribs (upper 7 pairs attached anteriorly to the sternum by their costal cartilages)
  • False ribs (8th, 9th, and 10th pairs attached anteriorly to each other and to the 7th rib by their costal cartilages and small synovial joints)
  • Floating ribs (11th and 12th pairs with no anterior attachment)

  
• Curvatures of the vertebral column

  • There are four natural curves: cervical, thoracic, lumbar, and sacral curvatures
  • The thoracic and sacral curvatures are concave anteriorly (primary curvatures)
  • The cervical and lumbar curvatures are secondary curves developing after birth
• Spinal canal


  Follows the different curves of the column, it is large and triangular in the cervical and lumbar regions, and small and rounded in the thoracic region

  
• Typical rib


  • A long, twisted, flat bone with a rounded, smooth superior border and a sharp, thin inferior border, the inferior border overhanging and forming the costal groove which accommodates the intercostal vessels and nerve, the anterior end attached to the corresponding costal cartilage
  • Has a head, neck, tubercle, shaft, and angle
  • The head has two facets for articulation with the corresponding vertebral body and that of the vertebra immediately above
  • The neck is a constricted portion between the head and the tubercle
  • The tubercle is a prominence on the outer surface at the junction of the neck and shaft
  • The neck has a facet for articulation with the transverse process of the corresponding vertebra
  • The shaft is thin, flattened, and twisted on its long axis, with the costal groove on the inferior border
  • The angle is where the shaft bends sharply forward

  
• Conus medullaris


  The tapered, lower end of the spinal cord, occurring near L1 and L2, occasionally lower

  
• First rib


  • Small and flattened from above downward, with the scalenus anterior muscle attached to its upper surface and inner border, the subclavian vein crossing the rib anteriorly to the muscle attachment, and the subclavian artery and lower trunk of the brachial plexus crossing the rib posteriorly to the muscle attachment
• Cervical rib


  A rib arising from the anterior tubercle of the transverse process of the 7th cervical vertebra, occurring in about 0.5% of humans, which can cause pressure on the lower trunk of the brachial plexus and the subclavian artery
• Cauda equina


  A bundle of spinal nerves and spinal nerve, the first through fifth sacral nerve pairs and the coccygeal nerve, all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord