Chapter 7: Skeletal System Vocabulary

Comprehensive vocabulary flashcards for Chapter 7 Skeletal System, covering bone anatomy, microscopic structures, ossification, skeletal landmarks, skeletal divisions, joint types, and movements.

Bone Functions

The four major functions of the skeletal system: support and protection, body movement, blood cell formation, and storage of inorganic salts and fats.

Classification of Bones

Bones categorized by shape into four main types: long bones, short bones, flat bones, and irregular bones.

Long Bone

A type of bone with an elongated shaft and expanded ends, such as the humerus of the arm or the femur of the leg.

Diaphysis

The shaft of a long bone surrounding the medullary cavity, composed primarily of compact bone.

Epiphysis

The expanded portion at each end of a long bone that articulates with another bone and is composed largely of spongy bone.

Periosteum

A tough, vascular membrane of dense connective tissue covering the exterior of a bone, except for the articular cartilage at the ends.

Endosteum

A thin membrane containing bone-forming cells that lines the medullary cavity inside a long bone.

Compact Bone

Dense bone tissue consisting of tightly packed osteons that forms the outer cylinder of long bone shafts and protective layer of bones.

Spongy Bone

Cancellous bone tissue consisting of branching bony plates called trabeculae, with spaces containing red bone marrow.

Osteon

The structural unit of compact bone, consisting of concentric lamellae surrounding a central canal containing blood vessels and nerves.

Central Canal

A longitudinal canal in the center of an osteon containing blood vessels and nerve fibers; also known as a Haversian canal.

Perforating Canal

A transverse canal in compact bone that connects central canals and houses blood vessels and nerves; also known as a Volkmann's canal.

Osteoblasts

Bone-forming cells that deposit collagen fibers and inorganic matrix during bone development and repair.

Osteocytes

Mature bone cells residing inside small chambers called lacunae within the calcified bone matrix.

Osteoclasts

Large, multinucleated cells that break down calcified bone matrix and release stored calcium ions into the blood.

Intramembranous Development

The formation of bone directly within sheetlike layers of primitive connective tissue, forming broad flat bones like those of the skull.

Endochondral Development

The process of bone formation where a hyaline cartilage model is gradually replaced by bony tissue.

Epiphyseal Plate

A band of hyaline cartilage remaining between the primary and secondary ossification centers in growing long bones that allows growth in length.

Parathyroid Hormone (PTH)

Hormone secreted by the parathyroid glands in response to decreased blood $Ca^{2+}$ that stimulates osteoclasts to break down bone and release calcium into the blood.

Calcitonin

Hormone secreted by the thyroid gland in response to increased blood $Ca^{2+}$ that inhibits osteoclasts to reduce blood calcium levels.

Axial Skeleton

The division of the skeleton consisting of the skull, middle ear bones, hyoid bone, vertebral column, and thoracic cage ($80$ bones in total).

Appendicular Skeleton

The division of the skeleton consisting of the pectoral girdle, upper limbs, pelvic girdle, and lower limbs ($126$ bones in total).

Condyle

A rounded process on a bone that usually articulates with another bone.

Crest

A narrow, ridgelike projection on a bone, such as the iliac crest.

Epicondyle

A projection situated above a condyle on a bone.

Facet

A small, nearly flat articular surface on a bone.

Fontanel

A soft spot in the skull of an infant where fibrous membranes cover the space between un-fused cranial bones.

Foramen

An opening through a bone that usually serves as a passageway for blood vessels, nerves, or ligaments.

Fossa

A relatively deep pit or depression in a bone.

Fovea

A tiny pit or depression in a bone, such as the fovea capitis of the femur.

Head

An enlargement on the end of a bone, such as the head of the humerus.

Meatus

A tubelike passageway within a bone, such as the external acoustic meatus.

Process

A prominent projection on a bone.

Sinus

A cavity or hollow space within a bone.

Spine

A thornlike projection on a bone, such as the spine of the scapula.

Sulcus

A furrow or groove on a bone, such as the intertubercular sulcus.

Suture

An immovable, interlocking line of union between bones, such as those in the skull.

Trochanter

A relatively large process on a bone, such as the greater trochanter of the femur.

Tubercle

A small, knoblike process on a bone.

Tuberosity

A knoblike process usually larger than a tubercle on a bone.

Paranasal Sinuses

Air-filled cavities within the frontal, ethmoid, sphenoid, and maxilla bones that open into the nasal cavity.

Atlas

The first cervical vertebra ($C1$) that supports the head and articulates with the occipital condyles.

Axis

The second cervical vertebra ($C2$) that features the toothlike dens (odontoid process) around which the atlas pivots.

True Ribs

The first $7$ pairs of ribs (vertebrosternal ribs) that join the sternum directly by their costal cartilages.

False Ribs

Rib pairs $8$–$12$ whose costal cartilages do not attach directly to the sternum.

Floating Ribs

Rib pairs $11$ and $12$ (vertebral ribs) that have no anterior attachment to the sternum or costal cartilage.

Synovial Joint

A freely movable joint containing a joint cavity filled with synovial fluid and enclosed by a joint capsule.

Ball-and-Socket Joint

A type of synovial joint with a globular head fitting into a cup-shaped cavity, allowing multiaxial movement in all planes and rotation.

Condyloid Joint

A biaxial synovial joint consisting of an ovoid condyle fitting into an elliptical cavity, permitting a variety of movements except rotation.

Plane Joint

A nonaxial synovial joint with flat or slightly curved articulating surfaces allowing sliding and back-and-forth motion.

Hinge Joint

A uniaxial synovial joint where a convex surface fits into a concave surface, permitting movement in one plane.

Pivot Joint

A uniaxial synovial joint where a cylindrical surface rotates within a ring formed of bone and ligamentous tissue.

Saddle Joint

A biaxial synovial joint formed where articulating surfaces have both concave and convex regions, permitting movement in two planes.

Meniscus

A fibrocartilage pad situated between the articulating surfaces of bones in a synovial joint, such as the knee.

Bursa

A fluid-filled sac lined with synovial membrane that cushions movements between tendons, muscles, and bones near joints.

Flexion

Bending parts at a joint so that the angle between them decreases and the parts come closer together.

Extension

Moving parts at a joint so that the angle between them increases and the parts move farther apart.

Abduction

Moving a body part away from the midline of the body.

Adduction

Moving a body part toward the midline of the body.

Dorsiflexion

Ankle movement that brings the foot closer to the shin.

Plantar Flexion

Ankle movement that moves the foot farther from the shin, pointing the toes downward.

Pronation

Rotation of the forearm so that the palm faces backward or downward.

Supination

Rotation of the forearm so that the palm faces forward or upward.