Axial Skeleton

Skull: Major Bones and Foramina

The skull is a complex structure composed of cranial and facial bones, protecting the brain and supporting facial structures. Key features include foramina for nerves and blood vessels, and sutures joining the bones.

• Frontal Bone: Forms the forehead and superior part of the orbit.

• Parietal Bones: Paired bones forming the superior and lateral aspects of the cranium.

• Occipital Bone: Forms the posterior and base of the skull; contains the foramen magnum for the spinal cord.

• Temporal Bones: Paired bones at the sides and base of the skull, housing the structures of the ears.

• Sphenoid Bone: Forms part of the cranial floor and orbits; contains the sella turcica.

• Ethmoid Bone: Located between the orbits, forms part of the nasal cavity and septum.

• Facial Bones: Include the maxilla, zygomatic, nasal, lacrimal, vomer, palatine, and mandible.

• Key Foramina: Supraorbital foramen, infraorbital foramen, mental foramen, optic canal, jugular foramen, stylomastoid foramen, foramen magnum.

• Sutures: Coronal, sagittal, lambdoid, and squamous sutures connect cranial bones.

Mandible

The mandible is the lower jawbone, the only movable bone of the skull, and houses the lower teeth.

• Body: Horizontal portion bearing the teeth.

• Ramus: Vertical extension on each side.

• Angle: Junction of the body and ramus.

• Condyloid Process: Articulates with the temporal bone to form the temporomandibular joint.

• Coronoid Process: Attachment for temporalis muscle.

• Mental Foramen: Passage for nerves and vessels.

Vertebral Column

The vertebral column supports the body, protects the spinal cord, and provides attachment points for ribs and muscles. It consists of cervical, thoracic, lumbar, sacral, and coccygeal regions.

• Cervical Vertebrae (C1–C7): C1 (Atlas) supports the skull; C2 (Axis) allows rotation.

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

• Lumbar Vertebrae (L1–L5): Largest vertebrae, support most body weight.

• Sacrum: Five fused vertebrae forming the posterior pelvis.

• Coccyx: Four fused vertebrae forming the tailbone.

Appendicular Skeleton

Long Bones: Structure and Features

Long bones, such as the femur, humerus, and tibia, are characterized by a shaft (diaphysis) and two ends (epiphyses). They provide support and leverage for movement.

• Diaphysis: Shaft composed of compact bone.

• Epiphysis: Expanded ends containing spongy bone and red marrow.

• Metaphysis: Region between diaphysis and epiphysis, containing the growth plate in children.

• Articular Cartilage: Covers joint surfaces for smooth movement.

Tibia and Fibula

The tibia and fibula are the two bones of the lower leg. The tibia is the larger, weight-bearing bone, while the fibula provides lateral stability.

• Tibia: Medial and larger; features include the tibial tuberosity, medial and lateral condyles, and medial malleolus.

• Fibula: Lateral and slender; features include the head and lateral malleolus.

Foot: Tarsals, Metatarsals, and Phalanges

The foot consists of tarsal bones (ankle), metatarsals (midfoot), and phalanges (toes). The arrangement provides support, balance, and mobility.

• Tarsals: Seven bones including the calcaneus (heel), talus (ankle), navicular, cuboid, and three cuneiforms (medial, intermediate, lateral).

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

• Phalanges: Fourteen bones forming the toes.

Thoracic Cage

Sternum and Ribs

The thoracic cage protects vital organs and supports the shoulder girdle. It consists of the sternum, ribs, and thoracic vertebrae.

• Sternum: Flat bone with three parts: manubrium, body, and xiphoid process.

• Ribs: Twelve pairs; true ribs (1–7) attach directly to the sternum, false ribs (8–12) do not.

Summary Table: Major Bones and Features