Bones and Structures of the Human Axial and Appendicular Skeleton

Bones of the Skull

Lateral View of the Skull

The lateral view of the skull provides a clear visualization of the major bones that form the cranium and facial skeleton. These bones protect the brain and support the structures of the face.

• Parietal Bone: Forms the superior and lateral aspects of the cranium.

• Frontal Bone: Located at the forehead, contributes to the anterior cranium.

• Temporal Bone: Situated at the sides and base of the skull, houses structures of the ear.

• Occipital Bone: Forms the posterior and base of the cranium.

• Sphenoid Bone: Butterfly-shaped bone at the base of the skull, visible laterally.

• Zygomatic Bone: Cheekbone, articulates with the temporal bone to form the zygomatic arch.

• Maxilla: Upper jaw bone, supports the upper teeth.

• Mandible: Lower jaw bone, the only movable bone of the skull.

Example: The temporal bone contains the external auditory meatus, which is the opening for the ear canal.

Sutures of the Skull

Major Cranial Sutures

Sutures are immovable joints that connect the bones of the skull. They are important anatomical landmarks and play a role in skull growth during development.

• Coronal Suture: Separates the frontal bone from the parietal bones.

• Sagittal Suture: Divides the two parietal bones along the midline.

• Lambdoid Suture: Separates the occipital bone from the parietal bones.

• Squamous Suture: Connects the parietal and temporal bones.

Example: The sagittal suture is often used as a reference point in neurosurgery.

Structures of the Skull

Anterior, Lateral, Inferior, and Superior/Interior Views

Different views of the skull reveal various anatomical features and foramina (openings) that allow passage of nerves and blood vessels.

• Anterior View: Shows the frontal bone, nasal bones, maxilla, and orbits (eye sockets).

• Lateral View: Highlights the zygomatic arch, temporal fossa, and mastoid process.

• Inferior View: Reveals the foramen magnum (opening for the spinal cord), occipital condyles, and palatine bones.

• Superior/Interior View: Displays the cranial cavity, including the frontal, parietal, and occipital bones.

Example: The foramen magnum is a large opening in the occipital bone through which the spinal cord passes.

Mandible

Lateral View of the Mandible

The mandible is the largest and strongest bone of the face. It forms the lower jaw and is the only movable bone of the skull.

• Body: Horizontal portion that holds the lower teeth.

• Ramus: Vertical extension on each side.

• Condylar Process: Articulates with the temporal bone to form the temporomandibular joint (TMJ).

• Coronoid Process: Attachment site for the temporalis muscle.

Example: The TMJ allows for movements such as chewing and speaking.

Vertebrae

Structure and Function

The vertebral column consists of individual vertebrae that protect the spinal cord and provide structural support.

• Cervical Vertebrae (C1-C7): Support the head and allow for its movement.

• Thoracic Vertebrae (T1-T12): Articulate with the ribs.

• Lumbar Vertebrae (L1-L5): Support the lower back.

• Sacrum: Five fused vertebrae forming the posterior pelvic wall.

• Coccyx: Four fused vertebrae forming the tailbone.

Example: The atlas (C1) and axis (C2) allow for rotation of the head.

Ribs and Sternum

Thoracic Cage

The ribs and sternum form the thoracic cage, which protects the heart and lungs and supports breathing.

• True Ribs (1-7): Attach directly to the sternum via costal cartilages.

• False Ribs (8-12): Attach indirectly or not at all to the sternum.

• Floating Ribs (11-12): Do not attach to the sternum.

• Sternum: Consists of the manubrium, body, and xiphoid process.

Example: The sternum is a common site for bone marrow biopsies.

Sacrum

Posterior and Lateral View

The sacrum is a triangular bone at the base of the spine, formed by the fusion of five sacral vertebrae.

• Ala: Wing-like projections on each side.

• Median Sacral Crest: Fused spinous processes.

• Sacral Foramina: Openings for sacral nerves.

Example: The sacrum articulates with the ilium to form the sacroiliac joint.

Clavicle and Scapula

Shoulder Girdle

The clavicle and scapula form the pectoral (shoulder) girdle, which connects the upper limb to the trunk.

• Clavicle: S-shaped bone that acts as a strut between the sternum and scapula.

• Scapula: Flat, triangular bone with features such as the spine, acromion, and glenoid cavity.

Example: The glenoid cavity of the scapula articulates with the head of the humerus to form the shoulder joint.

Humerus

Anterior and Posterior View

The humerus is the long bone of the upper arm, articulating with the scapula at the shoulder and the radius and ulna at the elbow.

• Head: Articulates with the glenoid cavity.

• Greater and Lesser Tubercles: Sites for muscle attachment.

• Deltoid Tuberosity: Attachment for the deltoid muscle.

• Olecranon Fossa: Receives the olecranon of the ulna during elbow extension.

Example: Fractures of the surgical neck of the humerus are common in elderly individuals.

Ulna and Radius

Forearm Bones

The ulna and radius are the two long bones of the forearm, allowing for movements such as pronation and supination.

• Ulna: Medial bone of the forearm, forms the elbow joint with the humerus.

• Radius: Lateral bone, rotates around the ulna during forearm movement.

Example: The radial tuberosity is the attachment site for the biceps brachii muscle.

Coxal Bone

Anterior and Posterior View

The coxal bone (hip bone) is formed by the fusion of three bones: ilium, ischium, and pubis. It forms the pelvic girdle.

• Ilium: Superior, flared portion.

• Ischium: Inferior, posterior portion.

• Pubis: Anterior portion.

• Acetabulum: Socket for the head of the femur.

Example: The pelvic girdle supports the weight of the upper body when sitting and standing.

Tibia and Fibula

Anterior View

The tibia and fibula are the two long bones of the lower leg, supporting body weight and allowing for movement.

• Tibia: Medial, larger bone, bears most of the weight.

• Fibula: Lateral, thinner bone, provides muscle attachment.

Example: The medial malleolus of the tibia forms the inner ankle.

Bones of the Foot

Superior View

The foot consists of multiple bones that provide support, balance, and mobility.

• Tarsals: Seven bones forming the ankle and heel (e.g., calcaneus, talus).

• Metatarsals: Five long bones forming the arch of the foot.

• Phalanges: Fourteen bones forming the toes.

Example: The calcaneus is the largest tarsal bone and forms the heel.

Additional info: Some anatomical terms and bone features were inferred based on standard anatomical knowledge, as the original notes and images were fragmentary and lacked detailed labeling.