7 The Skeleton Part B

Orbits Bony cavities in which the eyes are firmly encased and cushioned by fatty tissue Formed by parts of seven bones – frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid

Orbits Figure 7.9b

Nasal Cavity Constructed of bone and hyaline cartilage Roof – formed by the cribriform plate of the ethmoid Lateral walls – formed by the superior and middle conchae of the ethmoid, the perpendicular plate of the palatine, and the inferior nasal conchae Floor – formed by palatine process of the maxillae and palatine bone

Nasal Cavity Figure 7.10a

Nasal Cavity Figure 7.10b

Paranasal Sinuses Mucosa-lined, air-filled sacs found in five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones Air enters the paranasal sinuses from the nasal cavity and mucus drains into the nasal cavity from the sinuses Lighten the skull and enhance the resonance of the voice

Paranasal Sinuses Figure 7.11

Hyoid Bone Not actually part of the skull, but lies just inferior to the mandible in the anterior neck Only bone of the body that does not articulate directly with another bone Attachment point for neck muscles that raise and lower the larynx during swallowing and speech

Vertebral Column Formed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure results Cervical vertebrae – 7 bones of the neck Thoracic vertebrae – 12 bones of the torso Lumbar vertebrae – 5 bones of the lower back Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones

Vertebral Column Figure 7.13

Vertebral Column: Curvatures Posteriorly concave curvatures – cervical and lumbar Posteriorly convex curvatures – thoracic and sacral Abnormal spine curvatures include scoliosis (abnormal lateral curve), kyphosis (hunchback), and lordosis (swayback)

Vertebral Column: Ligaments Anterior and posterior longitudinal ligaments – continuous bands down the front and back of the spine from the neck to the sacrum Short ligaments connect adjoining vertebrae together

Vertebral Column: Ligaments Figure 7.14a

Vertebral Column: Intervertebral Discs Cushionlike pad composed of two parts Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage

Vertebral Column: Intervertebral Discs Figure 7.14b

General Structure of Vertebrae Body or centrum – disc-shaped, weight-bearing region Vertebral arch – composed of pedicles and laminae that, along with the centrum, enclose the vertebral foramen Vertebral foramina – make up the vertebral canal through which the spinal cord passes

General Structure of Vertebrae Spinous processes project posteriorly, and transverse processes project laterally Superior and inferior articular processes – protrude superiorly and inferiorly from the pedicle-lamina junctions Intervertebral foramina – lateral openings formed from notched areas on the superior and inferior borders of adjacent pedicles

General Structure of Vertebrae Figure 7.15