Skeletal Anatomy & Bone Structures

Diaphysis

Long Bone Shaft: Main central shaft or midportion of a long bone.

Epiphysis

Long Bone Ends: Rounded end of a long bone located beyond the epiphyseal plate.

Metaphysis

Long Bone Growth Zone: Flared region between the diaphysis and epiphyseal plate (meta- = between).

Epiphyseal Plate

Long Bone Growth Area: Cartilaginous plate at the ends of long bones where lengthwise growth occurs.

Articular Cartilage

Long Bone Joint Surface: Smooth layer capping the epiphysis that cushions joints and enables frictionless movement.

Compact Bone

Long Bone Outer Layer: Hard, dense bone tissue containing haversian canals for blood vessels and nerves.

Cancellous Bone

Long Bone Inner Layer: Porous, spongy bone structured in a latticework of bony fibers called trabeculae.

Periosteum

Long Bone Membrane: Fibrous, vascular membrane covering outer bone surfaces; rich in nerves and blood supply.

Medullary Cavity

Long Bone Shaft Core: Central hollow space within long bone shafts containing yellow bone marrow.

Frontal

Cranial Bone: Anterior skull bone forming the forehead and roof of eye orbits.

Parietal

Cranial Bone: Superior lateral skull bones forming the top and sides of the head.

Temporal

Cranial Bone: Inferior lateral skull bones housing the mastoid process, styloid process, and TMJ.

Occipital

Cranial Bone: Posterior base of skull containing the foramen magnum for spinal cord passage.

Sphenoid

Cranial Bone: Bat-shaped bone anchoring the skull base; houses the sella turcica for the pituitary gland.

Ethmoid

Cranial Bone: Delicate skull bone supporting the nasal cavity and eye orbits.

Nasal

Facial Bone: Bones forming the bridge of the nose.

Lacrimal

Facial Bone: Bones at the inner corner of the eyes (lacrim/o = tear).

Maxillary

Facial Bone: Upper jawbones forming the hard palate and floor of the nose.

Mandible

Facial Bone: Lower jawbone; the only movable facial bone.

Zygomatic

Facial Bone: Bones forming the cheekbones.

Vomer

Facial Bone: Bone forming the inferior portion of the nasal septum.

Sutures

Skull Structure: Immovable fibrous joint lines joining cranial bones together.

Fontanelles

Skull Structure: Soft, unossified spots between cranial bones in an infant's skull.

Sinuses

Skull Structure: Air cavities within facial and cranial bones that lighten the skull and warm incoming air.

Cervical (C1–C7)

Vertebral Spine: 7 neck vertebrae.

Thoracic (T1–T12)

Vertebral Spine: 12 chest vertebrae that articulate with the 12 pairs of ribs.

Lumbar (L1–L5)

Vertebral Spine: 5 strong, lower back vertebrae.

Sacrum

Vertebral Spine: 5 fused sacral vertebrae forming a single triangular bone base.

Coccyx

Vertebral Spine: 4 fused small tailbone segments.

Intervertebral Discs

Vertebral Spine: Fibrocartilaginous pads between vertebrae that absorb shock and allow spine movement.

Clavicle

Thorax / Shoulder: Collarbone connecting sternum to scapula.

Scapula

Thorax / Shoulder: Shoulder blade containing the acromion process.

Sternum

Thorax / Chest: Breastbone consisting of manubrium, body, and xiphoid process.

Ribs

Thorax / Chest: 12 pairs of rib bones (true 1–7, false 8–10, floating 11–12).

Humerus

Arm & Hand: Upper arm bone.

Ulna

Arm & Hand: Medial forearm bone featuring the olecranon (elbow).

Radius

Arm & Hand: Lateral forearm bone located on the thumb side.

Carpals

Arm & Hand: Wrist bones.

Metacarpals

Arm & Hand: Hand bones between wrist and fingers.

Phalanges (Hand)

Arm & Hand: Finger bones.

Ilium

Pelvic Girdle: Upper, flared portion of the pelvis.

Ischium

Pelvic Girdle: Posterior, lower portion of the pelvic bone.

Pubis

Pelvic Girdle: Anterior portion of the pelvis joined at the pubic symphysis.

Acetabulum

Pelvic Girdle: Deep socket in the hip joint receiving the head of the femur.

Femur

Leg & Foot: Thigh bone; longest and strongest bone in the body.

Patella

Leg & Foot: Kneecap; sesamoid bone protecting the knee joint.

Tibia

Leg & Foot: Shinbone; larger medial lower leg bone with medial malleolus.

Fibula

Leg & Foot: Smaller lateral lower leg bone with lateral malleolus.

Talus

Leg & Foot: Ankle bone articulating with the tibia and fibula.

Tarsals

Leg & Foot: Hindfoot and midfoot bones, including the calcaneus (heel).

Metatarsals

Leg & Foot: Foot bones between ankle and toes.

Phalanges (Foot)

Leg & Foot: Toe bones.