Anatomy: The Skeletal System

A set of vocabulary flashcards based on the lecture notes on the human skeletal system, covering bone classifications, tissue structures, development, joint types, and skeletal disorders.

Skeletal System

The structural framework of the body that provides support, protection, and movement, composed of $206$ bones.

Human Bone Count Breakdown

The average adult body contains $206$ bones: $29$ skull bones, $26$ vertebral bones, $1$ sternum with $24$ rib bones, $4$ pectoral girdle bones with $60$ upper limb bones, and $2$ pelvic girdle bones with $60$ lower limb bones.

Cartilage

A resilient, semi-rigid form of connective tissue that forms parts of the skeleton where flexibility is required; it is avascular and receives nutrients via diffusion.

Periosteum

A fibrous connective tissue sleeve that surrounds each skeletal bone element, except where articular cartilage occurs.

Perichondrium

A fibrous connective tissue covering that surrounds cartilage.

Long Bones

Tubular-shaped bones, such as the humerus in the arm or the femur in the thigh.

Short Bones

Cuboidal-shaped bones found only in the tarsus (ankle) and carpus (wrist).

Flat Bones

Bones that usually serve protective functions, such as the flat bones of the cranium that protect the brain, or the sternum.

Irregular Bones

Bones with various shapes other than long, short, or flat, such as bones of the face and vertebrae.

Sesamoid Bones

Bones that develop in certain tendons where they cross the ends of long bones in limbs to protect the tendons, such as the patella (knee cap).

Classification of Bones by Shape

Bones classified according to shape, including flat bone (sternum), irregular bone (vertebra), sesamoid bone (patella), sutural bone, long bone (femur), and short bones (cuneiforms).

Compact Bone

Bone tissue composed of tightly packed bone cells and bone matrix, found in the shaft of long bones and the surface of flat bones.

Cancellous Bone

Spongy bone tissue found at the ends of long bones, in the pelvis, and in the ribs.

Structure of a Long Bone

Anatomical organization of a long bone showing the epiphysis, metaphysis, diaphysis, medullary cavity, compact bone, spongy bone, periosteum, and cartilage.

Endosteum

A lining covering the inner surface of bones, trabeculae, and medullary cavity, composed of osteoblasts, osteoclasts, and bone marrow.

Epiphysis

The rounded end portion of a long bone.

Diaphysis

The shaft of a bone that ossifies from the primary ossification center and grows as the bone develops.

Metaphysis

The flared part of the diaphysis located nearest to the epiphysis.

Axial Skeleton

The central division of the skeletal system consisting of the bones of the head (cranium/skull), neck (hyoid bone and cervical vertebrae), and trunk (ribs, sternum, vertebrae, and sacrum).

Appendicular Skeleton

The division of the skeletal system consisting of the bones of the limbs, including those forming the pectoral (shoulder) and pelvic girdles.

Intramembranous Ossification

Membranous bone formation in which mesenchymal models form during the embryonic period and direct ossification of mesenchyme begins in the fetal period.

Endochondral Ossification

Cartilaginous bone formation in which cartilage models form from mesenchyme during the fetal period, and bone subsequently replaces most of the cartilage.

Joints

Unions or junctions between two or more bones or rigid parts of the skeleton.

Synovial Joints

Joints united by an articular capsule composed of an outer fibrous layer lined by a serous synovial membrane spanning and enclosing an articular cavity.

Types of Synovial Joints

Classification of synovial joints including pivot, hinge, saddle, condyloid, plane, and ball & socket joints.

Fibrous Joints

Joints that are united by fibrous tissue.

Syndesmosis

A type of fibrous joint that unites bones with a sheet of fibrous tissue, either a ligament or a fibrous membrane.

Synchondroses

Primary cartilaginous joints in which bones are united by hyaline cartilage, permitting slight bending during early life.

Symphyses

Secondary cartilaginous joints that are strong and slightly movable, united by fibrocartilage.

Osteoporosis

A reduction in the quantity of bone or atrophy of skeletal tissue resulting from a decrease in both organic and inorganic components during aging.

Callus Formation

The development of a newly-formed collar of callus around broken bone during the healing and remodeling response to a fracture.

Degenerative Joint Disease

Progressive wear and degenerative changes in synovial joints caused by heavy use over several years.

Avascular Necrosis

The death of bone tissue resulting from the loss of arterial supply to an epiphysis or other parts of a bone.