Skeletal Structures in our Musculoskeletal System

Vocabulary practice flashcards covering bones, cells, classifications, structures, divisions, joints, and movements from the Skeletal System lecture.

Skeletal System

The organ system consisting of 206 bones bound together by ligaments to form joints, providing structural support, organ protection, movement, mineral storage, and hematopoiesis.

Haematopoiesis

The process of blood cell formation that takes place within the bone marrow of the skeletal system.

Osteoblasts

Bone-building cells that deposit new bone tissue by secreting calcium and phosphorus into spaces between membranes.

Osteoclasts

Bone-destroying cells that secrete enzymes to digest bone materials, breaking down bone tissue and releasing calcium and phosphate.

Osteocytes

Mature bone cells formed from osteoblasts that function to monitor and maintain bone tissues.

Calcitonin

A hormone produced by the thyroid gland that increases calcium uptake into bone, thereby decreasing blood calcium levels.

Parathyroid Hormone

A hormone produced by the parathyroid glands that decreases calcium uptake into bone, thereby increasing blood calcium levels.

Long Bones

Bones characterized by a central shaft (diaphysis) and extremities (epiphyses), such as the humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, phalanges, and clavicle.

Short Bones

Bones present in groups consisting of an outer layer of compact bone and an inner layer of cancellous bone enclosed by periosteum, such as the carpals of the wrist and tarsals of the ankle.

Flat Bones

Thin bones consisting of a single layer of cancellous tissue between two layers of compact bone tissue, including the cranium, ribs, sternum, scapula, and pelvis.

Irregular Bones

Bones of varying shapes consisting of compact and cancellous bone covered by periosteum, such as the vertebrae, facial bones, and hyoid bone.

Compact Bone

Dense and hard bone tissue forming the outer shell of bones; thin at the extremities and thick at the shaft of long bones.

Cancellous Bone

Spongy bone tissue located at the ends of long bones that contains red bone marrow and spaces that make the bone lightweight.

Diaphysis

The central portion or main shaft of a long bone.

Epiphysis

The extremity located at both distal and proximal ends of a long bone.

Periosteum

A tough, fibrous tissue containing blood vessels and nerves that covers, nourishes, and protects the bone.

Articular Cartilage

Cartilage covering the epiphysis that acts as a shock absorber between two bones forming a joint, allowing friction-free movement.

Medullary Cavity

The central canal running the length of a long bone shaft, containing red bone marrow during infancy and yellow bone marrow in adulthood.

Red Bone Marrow

Bone marrow found in cancellous bone and infant medullary cavities responsible for blood cell production.

Yellow Bone Marrow

Bone marrow located in the medullary cavity of adult long bones that functions as a fat storage site.

Axial Skeleton

The central vertical upright division of the skeleton comprising 80 bones, including the skull (cranium and face), middle ear ossicles, hyoid bone, vertebral column, and bony thorax.

Appendicular Skeleton

The skeletal division comprising 126 bones of the upper and lower appendages, including the shoulder girdle, arms, forearms, wrist, hands, pelvic girdle, legs, ankles, and feet.

Cranium

The cranial portion of the skull consisting of 8 bones: 1 frontal, 2 parietal, 2 temporal, 1 occipital, 1 ethmoid, and 1 sphenoid bone.

Facial Bones

The 14 bones comprising the facial structure: 2 nasal, 2 lacrimal, 2 inferior nasal conchae, 1 vomer, 2 palatine, 2 zygomatic, 2 maxillae, and 1 mandible.

Auditory Ossicles

The three small bones of the middle ear consisting of the malleus, incus, and stapes.

Hyoid Bone

A U-shaped bone located in the upper neck that anchors the tongue and functions in swallowing.

Vertebral Column

The spine structure extending from the skull to the pelvis consisting of 26 bones: cervical (C1-C7), thoracic (T1-T12), lumbar (L1-L5), sacrum, and coccyx.

Sternum

The breastbone located at the center of the thorax, consisting of three parts: manubrium, body, and xiphoid process.

Bony Thorax

The rib cage structure attached posteriorly to the thoracic vertebrae, consisting of 12 pairs of flat bones divided into true ribs (1-7), false ribs (8-10), and floating ribs (11-12).

Shoulder Girdle

The appendicular structure consisting of 2 clavicles and 2 scapulae that connects the upper limbs to the axial skeleton.

Pelvic Girdle

The structure consisting of three fused parts—the ilium, ischium, and pubis—that anchors the lower extremities to the axial skeleton.

Tendon

A cordlike connective tissue structure that attaches muscle to bone.

Ligament

A band of elastic fibers that stretches across joints to connect bone to bone.

Joint

The site where two bones meet, providing stability and mobility to the skeletal system.

Fibrous Joint

An immovable joint (synarthrosis) where bones are joined by fibrous connective tissue with no movement, such as skull sutures.

Cartilaginous Joint

A slightly movable joint (amphiarthrosis) where bones are separated by cartilage that compresses to allow limited movement, such as intervertebral joints.

Synovial Joint

A freely movable joint (diarthrosis) characterized by articular cartilage, a joint capsule, a synovial membrane, and lubricating synovial fluid.

Synovial Fluid

Fluid secreted by the synovial membrane that lubricates joint bones and reduces friction during movement.

Ball-and-Socket Joint

A synovial joint featuring a rounded bone head inside a concave socket, providing the widest range of movement including rotation, flexion, extension, abduction, and adduction (e.g., shoulder and hip).

Hinge Joint

A synovial joint that permits motion in a single forward-and-backward plane like a door hinge, executing flexion and extension (e.g., knee, elbow, fingers).

Pivot Joint

A synovial joint where one bone pivots around a ring or projection of another bone to allow rotation (e.g., radius/ulna forearm, atlas/axis neck).

Gliding Joint

A synovial joint with flat or slightly curved surfaces where one bone glides against another, allowing minimal movement (e.g., carpal joints, tarsal joints).

Condyloid Joint

A synovial joint where an oval condyle fits into an oval cavity, combining hinge and gliding motions (e.g., temporomandibular joint, wrist).

Flexion

A joint movement involving bending that reduces the angle between two bones and brings them closer together.

Extension

A joint movement involving straightening that increases the angle and distance between two bones.

Abduction

Joint movement that moves a limb or body structure away from the midline of the body.

Adduction

Joint movement that moves a limb or body structure towards the midline of the body.

Rotation

Movement of a bone around its own central axis, such as turning the head from side to side.

Circumduction

A composite circular movement of a arm or limb around a joint combining flexion, extension, abduction, and adduction.

Pronation

Joint movement of the radius and ulna that turns the palm of the hand from an upward-facing to a downward-facing position.

Supination

Joint movement of the radius and ulna that turns the palm of the hand from a downward-facing to an upward-facing position.

Inversion

Ankle joint movement that turns the sole of the foot medially towards the body.

Eversion

Ankle joint movement that turns the sole of the foot laterally away from the body.