Human Anatomy: Skull and Nasal Cavity

Skull (Anterior View)

• Most prominent structures: Frontal bone, zygomatic bone, maxillae, mandible
• Most prominent openings: Orbits/eye sockets (cone-shaped fossae, provide protection for the eyes, attachment points for eye muscles), Nasal cavity (divided by nasal septum)
• Other openings: Superior and inferior orbital fissures, Optic foramen, Nasolacrimal canal

Nasal Cavity

• Divided into right and left halves by the nasal septum
• Nasal septum formed by two structures: Vomer bone, Perpendicular plate of the ethmoid bone
• Lateral wall of the nasal cavity contains three bony shelves called nasal conchae: Inferior nasal concha, Middle nasal concha, Superior nasal concha

Paranasal Sinuses

• Frontal, maxillary, ethmoidal, and sphenoidal sinuses

Mastoid Air Cells

• Small air-filled cavities within the mastoid process of the temporal bone.

Skull (Interior View of the Cranial Cavity)

• Floor of the cranial cavity can be divided into three cranial fossae: Anterior, middle, and posterior
• Bones forming the floor: Frontal, Ethmoid, Sphenoid (central region - sella turcica), Temporal, Occipital
• Foramina in the floor of the middle fossa: Foramen rotundum, Foramen ovale, Foramen spinosum, Jugular foramen
• Foramina at the posterior fossa: Foramen magnum

Frontal Bone

• Flat bone
• Makes up the forehead and upper portion of the eye sockets

Parietal Bones

• Pair of flat bones located on either side of the head behind the frontal bone

Temporal Bones

• Pair of irregular bones located under the parietal bones

Occipital Bone

• Flat bone at the back of the skull
• Contains the foramen magnum (opening connecting the spinal cord to the brain)

Sphenoid Bone

• Irregular bone located below the frontal bone

Ethmoid Bone

• Irregular bone located in front of the sphenoid bone
• Forms part of the nasal cavity

Viscerocranium/Facial Bones

• Maxilla: Jawbone, forms the upper jaw, contains the superior teeth
• Zygomatic bone: Cheekbone, anterior to the sphenoid bone; contributes to the zygomatic arch (formed by processes of temporal and zygomatic bones, bridge across the side of the face, provides attachment for mandible-moving muscles)
• Palatine: Roof of oral cavity, separates nasal cavity and nasopharynx from the mouth; aids in chewing and breathing simultaneously
  • Hard Palate: Forms the roof of the mouth and floor of the nasal cavity
  • Soft Palate: Made of connective tissue and muscles, extends posteriorly from the hard palate
• Nasal bones: Form the bridge of the nose
• Lacrimal bones: Form part of the medial walls of the orbits
• Inferior nasal conchae: Small, scroll-shaped bones within the nasal cavity
• Mandible: Forms the lower jaw, contains the inferior teeth, articulates with the temporal bone at the mandibular fossa
• Vomer: Forms the inferior half of the nasal septum

Skull (Lateral View)

• Parietal and temporal bones: Form a large portion of the side of the head, join at the squamous suture
• Parietal bone joins to the:
  • Frontal bone via the coronal suture
  • Occipital bone via the lambdoid suture
• Prominent features of the temporal bone:
  • External auditory canal
  • Mastoid process: Prominent projection behind the ear, attachment point for neck muscles involved in head rotation
  • Sphenoid bone: Resembles a butterfly, part of it can be seen anterior to the temporal bone
  • Zygomatic bone (cheekbone)
  • Zygomatic arch
  • Maxilla
  • Mandible

Lumbar Vertebrae

• Large, thick bodies
• Heavy rectangular transverse and spinous processes
• Superior articular facets face medially, inferior articular facets face laterally
• Adds strength, limits rotation

Sacrum and Coccyx

• Sacrum:
  • Alae: Superior lateral parts of fused transverse processes
  • Auricular surface: Articulates with pelvic bone
  • Median sacral crest: Partially fused spinous processes
  • Sacral hiatus: Site of anesthesia injection
  • Sacral foramina: Intervertebral foramina
  • Sacral promontory: Anterior edge of the body of the first vertebra, marks separation of the abdominal and pelvic cavities
• Coccyx: Tailbone, 3-5 semi-fused vertebrae

Thoracic Cage

• Functions: Protects vital organs, forms a semi-rigid chamber for respiration
• Parts:
  • Thoracic vertebrae
  • Ribs (12 pairs):
    • True ribs (superior seven): Attach directly to the sternum via costal cartilages
    • False ribs (inferior five): Ribs 8 to 10 are joined by common cartilage to the costal cartilage of rib 7 and then to the sternum.
    • Floating ribs (11 to 12): Do not attach to the sternum
  • Sternum

Sternum

• Manubrium: Articulates with the first rib and clavicle, contains the jugular notch (superiorly), joins the body at the sternal angle (where the second rib articulates)
• Body: Third through seventh ribs articulate, also called the gladiolus
• Xiphoid process: Inferior tip

Appendicular Skeleton

• Girdles: Pectoral, Pelvic
• Upper Limbs: Arm, Forearm, Wrist, Hand
• Lower Limbs: Thigh, Leg, Foot

Pectoral Girdle: Scapula and Clavicle

• Scapula:
  • Acromion process: Forms protective cover, attachment for clavicle, attachment for muscles

Pelvic Girdle: Hip Bones and Sacrum

• Hip bones and sacrum form a ring
• Pelvis: Pelvic girdle and coccyx
• Coxal bones: Right and Left
  • Ilium: Iliac crest, anterior/posterior superior iliac spines, greater sciatic notch, auricular surface, sacroiliac joint, iliac fossa
  • Ischium: Ischial tuberosity, lesser sciatic notch, ischial spine, ischial ramus
  • Pubis: Pubic crest, superior/inferior pubic rami, symphysis pubis (pubic symphysis)
• Acetabulum: Articulates with the head of the femur
• Obturator foramen
• Sacrum

Pelvis

• Pelvic brim: Separates the false (greater) pelvis (superior to the brim) from the true pelvis (inferior to the brim)
• Pelvic inlet: Opening superior to the true pelvis
• Pelvic outlet: Opening inferior to the true pelvis