Ch07 (A,B,C) Osteology

Skeletal System

Composed of bones, cartilages, joints, and ligaments; accounts for 20% of body mass.

Two Major Divisions of Skeleton

Axial skeleton and Appendicular skeleton.

Axial Skeleton

Consists of 80 bones divided into the Skull, Vertebral column, and Thoracic cage.

Functions of Axial Skeleton

Forms longitudinal axis of the body; supports the head, neck, and trunk; protects the brain, spinal cord, and thoracic organs.

Skull

The most complex bony structure in the body, formed by cranial bones and facial bones.

Cranial Bones (Cranium)

Enclose the brain in the cranial cavity and provide attachment sites for head and neck muscles.

Facial Bones

Form the framework of the face, contain cavities for special sense organs (sight, taste, smell), and secure the teeth.

Sutures

Joints where most skull bones are flat and firmly locked together (except for the mandible).

Cranial Vault (Calvaria)

Forms the superior, lateral, and posterior portion of the skull, as well as the forehead.

Cranial Base

Forms the inferior aspect of the skull; internally divided into the anterior, middle, and posterior fossae.

Cranial Bones (8 total)

Frontal (1), Parietal (2), Occipital (1), Temporal (2), Sphenoid (1), Ethmoid (1).

Coronal Suture

Articulation between the parietal bones and the frontal bone.

Sagittal Suture

Articulation between the right and left parietal bones.

Lambdoid Suture

Articulation between the parietal bones and the occipital bone.

Squamous (Squamosal) Sutures

Articulation between the parietal and temporal bones on each side of the skull.

Foramen Magnum

"Large hole" in the occipital bone through which the brain connects with the spinal cord.

Occipital Condyles

Paired structures flanking the foramen magnum that articulate with the 1st vertebra (Atlas).

External Acoustic Meatus

The external ear canal; located in the tympanic region of the temporal bone.

Carotid Canal

Passageway in the petrous region of the temporal bone for the internal carotid artery.

Sphenoid Bone

Complex, bat-shaped

Sella Turcica (in Sphenoid bone)

Prominence that includes the hypophyseal fossa, which encloses the pituitary gland.

Ethmoid Bone

The deepest skull bone; superior part formed by paired cribriform plates.

Crista Galli

Triangular process of the ethmoid bone that serves as the point of attachment for the brain’s dura mater covering.

Vertebral Column

A flexible curved structure containing 26 irregular bones (vertebrae) extending from the skull to the pelvis.

Five Vertebral Regions

Cervical (7 vertebrae), Thoracic (12 vertebrae), Lumbar (5 vertebrae), Sacrum (5 fused bones), and Coccyx (4 fused bones).

Cervical and Lumbar Curvatures

Concave posteriorly.

Thoracic and Sacral Curvatures

Convex posteriorly.

Anterior and Posterior Longitudinal Ligaments

Continuous bands that run down the front and back of the spine; support and prevent hyperextension or hyperflexion.

Intervertebral Discs

Cushionlike pads sandwiched between vertebrae that act as shock absorbers.

Nucleus Pulposus

Inner gelatinous nucleus of the intervertebral disc; gives the disc its elasticity and compressibility.

Anulus Fibrosus

Outer collar of the intervertebral disc composed of collagen and fibrocartilage.

Herniated (Prolapsed) Disc

Rupture of the anulus fibrosus resulting in protrusion of the nucleus pulposus, which can press on spinal cord or nerves.

Scoliosis

Abnormal lateral rotation of the spine, most often in the thoracic region.

Kyphosis (Hunchback)

Abnormal dorsal thoracic curvature.

Lordosis (Swayback)

Accentuated lumbar curvature.

Intervertebral Foramina

Lateral openings between vertebrae for the passage of spinal nerves.

Cervical Vertebrae (C3-C7 feature)

Have a large, triangular vertebral foramen and a

Vertebra Prominens

C7; its large spinous process can be felt through the skin and is used as a landmark.

Atlas (C1)

The first cervical vertebra; has

Appendicular Skeleton

Consists of the bones of the limbs and their girdles.

Pectoral Girdle (Shoulder Girdle)

Consists of the clavicles and scapulae; offers a great degree of mobility because the scapulae are not attached to the axial skeleton.

Clavicles (Collarbones)

S-shaped bone; Sternal end (medial) articulates with the sternum; Acromial end (lateral) articulates with the scapula.

Scapulae (Shoulder Blades)

Thin, triangular flat bones on the dorsal surface of the rib cage.

Glenoid Cavity/Fossa (Scapula)

Socket that forms the shoulder joint.

Acromion (Scapula)

Lateral projection that articulates with the clavicle to form the acromioclavicular joint.

Coracoid Process (Scapula)

Anterior projection that anchors the biceps muscle of the arm.

Bones of the Upper Limb

Humerus, Radius, Ulna, 8 Carpals, 5 Metacarpals, and 14 Phalanges (30 bones total).

Humerus

The only bone of the arm; largest and longest bone of the upper limb.

Surgical Neck (Humerus)

The most frequently fractured part of the humerus.

Deltoid Tuberosity (Humerus)

Midway down the shaft; site of deltoid muscle attachment.

Trochlea (Humerus)

Distal condyle that articulates with the ulna.

Capitulum (Humerus)

Distal ball-like condyle that articulates with the radius.

Forearm Bones

Ulna (medial) and Radius (lateral); connected by the interosseous membrane.

Ulna

Medial bone of the forearm; Olecranon and coronoid processes grip the trochlea of the humerus, forming the elbow hinge joint.

Radius

Lateral bone of the forearm; its head articulates with the capitulum of the humerus.

Distal Carpal Row (L to M)

Trapezium, Trapezoid, Capitate, and Hamate.

Metacarpus

Five metacarpal bones (I to V) that form the palm.

Phalanges (Digits/Fingers)

Digit I (Pollex/thumb) has two bones; Digits II to V have three bones (proximal, middle, distal phalanx).

Pelvic Girdle (Hip Girdle)

Formed by 2 hip bones (coxal bones/os coxae) and the sacrum.

Three Fused Coxal Bones

Ilium, Ischium, and Pubis.

Acetabulum

Deep socket formed by the fusion of the three coxal bones; receives the head of the femur.

Ilium

Superior region of the coxal bone; its auricular surface articulates with the sacrum.

Ischium

Posteroinferior part of the hip bone.

Pubis

Anterior portion of the hip bone; the two pubic bones join at the pubic symphysis joint.