Introduction to the Skeletal System

Comprehensive vocabulary flashcards covering the structure of bone tissue, bone development, axial and appendicular skeletal divisions, and joint classifications from the skeletal system lecture notes.

Functions of Bones

The five essential bodily functions provided by the human skeleton: support, protection, movement, mineral storage, and the formation of blood cells.

Compact Bone

A dense type of bone tissue consisting of closely packed osteons (haversian systems) tightly packed together to form what appears to be a solid mass.

Spongy (Cancellous) Bone

A lighter, less dense bone tissue consisting of plates and bars called trabeculae adjacent to small, irregular cavities that contain red bone marrow.

Osteogenesis

The process of bone formation involving three types of cells: osteoblasts, osteocytes, and osteoclasts.

Osteoblasts

Bone-forming cells that participate in bone formation and homeostasis.

Osteoclasts

Cells that resorb or break down bone tissue; their equilibrium with osteoblasts maintains bone tissue.

Osteocytes

Mature bone cells located in spaces called lacunae between the concentric rings of matrix.

Intramembranous Ossification

The process of bone formation in which connective tissue membranes are replaced by bone, occurring in the flat bones of the skull.

Endochondral Ossification

The process of bone formation where bone tissue replaces hyaline cartilage models, forming most bones in the body.

Epiphyseal Plate

The growth zone located between the diaphysis and the epiphysis where bones grow in length until it completely ossifies.

Diaphysis

The central shaft of a long bone.

Epiphysis

The expanded structure located at each end of the diaphysis of a long bone.

Osteon (Haversian System)

The structural unit of compact bone, consisting of an osteonic (haversian) canal surrounded by concentric lamellae, lacunae containing osteocytes, and radiating canaliculi.

Osteonic (Haversian) Canal

The central canal of an osteon containing blood vessels that run parallel to the long axis of the bone.

Lamellae

Concentric rings of hard matrix that surround the osteonic canal in compact bone.

Lacunae

Small spaces situated between the rings of matrix (lamellae) that contain osteocytes.

Canaliculi

Small channels radiating from the lacunae that provide passageways through the hard matrix to the osteonic canal in compact bone, or to adjacent cavities in spongy bone.

Perforating Canals

Canals (also called Volkmann's canals) that allow osteonic blood vessels to interconnect with vessels on the surface of the bone.

Trabeculae

Plates and bars of bone in spongy bone organized along lines of stress to provide maximum structural strength, capable of realigning if the direction of stress changes.

Axial Skeleton

A skeletal division consisting of $80$ bones, encompassing the skull ($22$ bones), vertebral column ($26$ bones), and thoracic cage ($25$ bones).

Appendicular Skeleton

A skeletal division consisting of $126$ bones, comprising the pectoral girdles, upper extremities, pelvic girdle, and lower extremities.

Cranial Bones

The $8$ bones enclosing the brain: parietal ($2$), temporal ($2$), frontal ($1$), occipital ($1$), ethmoid ($1$), and sphenoid ($1$).

Facial Bones

The $14$ anterior skull bones: maxilla ($2$), zygomatic ($2$), mandible ($1$), nasal ($2$), platine ($2$), inferior nasal concha ($2$), lacrimal ($2$), and vomer ($1$).

Vertebral Column

The column of vertebrae consisting of $7$ cervical vertebrae, $12$ thoracic vertebrae, $5$ lumbar vertebrae, $1$ sacrum, and $1$ coccyx.

Thoracic Cage

The skeletal enclosure of the chest formed by the sternum ($1$) and ribs ($24$).

Pectoral Girdles

Bilateral skeletal structures that attach the upper extremities to the axial skeleton, each consisting of a clavicle ($2$ total) and a scapula ($2$ total).

Bones of the Upper Extremity

The bones of the arms and hands: humerus ($2$), radius ($2$), ulna ($2$), carpals ($16$), metacarpals ($10$), and phalanges ($28$).

Pelvic Girdle

A structure composed of $2$ coxal, innominate, or hip bones, each featuring the ilium, iliac crest, ischium, acetabulum (asetabulum), and pubis.

Bones of the Lower Extremity

The bones of the legs and feet: femur ($2$), tibia ($2$), fibula ($2$), patella ($2$), tarsals ($14$), metatarsals ($10$), and phalanges ($28$).

Articulation (Joint)

A junction where two bones come together, categorized by mobility into immovable, slightly movable, and freely movable types.

Synarthroses

Immovable joints (singular: synarthrosis) in which bones are in very close contact separated only by a thin layer of fibrous connective tissue, such as sutures in the skull.

Amphiarthroses

Slightly movable joints (singular: amphiarthrosis) connected by hyaline cartilage or fibrocartilage, such as costal cartilages, the symphysis pubis, and intervertebral disks.

Diarthroses (Synovial Joints)

Freely movable joints (singular: diarthrosis) containing bone ends capped with articular cartilage, a joint cavity, and an outer fibrous capsule lined by a synovial membrane.

Synovial Membrane

The inner layer of the dense fibrous joint capsule in diarthroses that secretes synovial fluid into the joint cavity for lubrication.

Articular Cartilage

The hyaline cartilage covering the opposing bone surfaces within a diarthrodial (synovial) joint cavity.