Anatomy and Physiology: Skeletal System, Joints, and Muscular Mechanics

Comprehensive vocabulary flashcards covering skeletal anatomy, bone tissue, joint classifications, stability, muscle mechanics, and kinetic chains.

Axial Skeleton

The skeletal division consisting of approximately 80 bones (skull, vertebral column, ribs, and sternum) that forms the longitudinal axis and protects the brain, spinal cord, and thoracic organs.

Appendicular Skeleton

The skeletal division comprising the bones of the upper and lower limbs and their girdles, attached to the axial skeleton to enable movement and manipulation.

Compact (Cortical) Bone

Dense bone tissue forming the outer shell of all bones that provides protection and strength for weight-bearing.

Spongy (Cancellous) Bone

Highly porous, vascularised bone tissue containing a lattice-like trabecular matrix that keeps skeletal weight down while resisting mechanical forces.

Long Bones

Tubular-shaped bones, such as the humerus and femur.

Short Bones

Roughly cuboidal-shaped bones, such as the carpals and tarsals.

Flat Bones

Bones formed by two plates of compact bone separated by spongy bone, such as skull bones.

Irregular Bones

Bones with complex or unusual shapes, such as vertebrae and facial bones.

Diaphysis

The shaft of a long bone, composed of thick compact bone surrounding a medullary cavity that contains bone marrow.

Epiphysis

The broader end of a long bone filled with spongy bone, covered with articular cartilage, that transfers weight to the diaphysis.

Epiphyseal Growth Plate

A layer of hyaline cartilage between the diaphysis and epiphysis where lengthwise bone growth occurs.

Metaphysis

The portion of the diaphysis closest to the epiphysis, adjacent to the epiphyseal growth plate.

Articular Surface

A smooth area on a bone covered in hyaline cartilage where it forms a joint with another bone.

Protrusions

Bony landmarks that stick out (such as tubercles, tuberosities, spines, and processes) and serve as attachment sites for tendons and ligaments.

Depressions / Holes

Bony landmarks (such as foramina, grooves, notches, and fossae) that provide space for nerves or blood vessels to pass through or alongside bone.

Endochondral Ossification

Bone development process in which bone forms from a hyaline cartilage model; occurs in long bones, short bones, and most irregular bones.

Intramembranous Ossification

Bone development process in which bone develops directly within a fibrous membrane without a cartilage stage; occurs in flat skull bones, the mandible, and clavicles.

Anterior Fontanelle

The unossified membrane remnant ("soft spot") on a newborn skull formed during intramembranous ossification.

Appositional Growth

Bone growth in width accomplished by adding new osteons and circumferential lamellae to the outer periphery of cortical bone.

Wolff's Law

The principle stating that bone adapts to the mechanical loads placed upon it, building denser matrix where loaded and resorbing matrix where un-loaded.

Osteoblast

A matrix-synthesising bone cell responsible for bone formation by laying down collagenous matrix and depositing minerals like calcium.

Osteoclast

A bone-resorbing cell responsible for breaking down bone tissue.

Osteoporosis

A bone disease characterised by reduced bone mass where the rate of bone resorption exceeds bone formation, leading to thinner cortical bone and more porous cancellous bone.

Bone Mineral Density (BMD)

A measure of bone density representing the amount of calcium and other mineral content present in bone tissue.

Fibrous Joints

Joints where bones are connected by fibrous connective tissue without a joint cavity; functionally classified mostly as synarthroses (immovable).

Cartilaginous Joints

Joints where bones are joined by cartilage without a joint cavity; functionally classified mostly as amphiarthroses (slightly movable).

Synovial Joints

Freely movable joints (diarthroses) containing a fluid-filled joint cavity, enclosed by a capsule with a synovial membrane, and lined with articular cartilage.

Synarthrosis

A functional classification for immovable joints, such as skull sutures.

Amphiarthrosis

A functional classification for slightly movable joints, such as the pubic symphysis or intervertebral discs.

Diarthrosis

A functional classification for freely movable joints, encompassing all synovial joints.

Suture

A subtype of fibrous joint where interlocking bones are held together by short fibrous tissue, classified functionally as a synarthrosis.

Syndesmosis

A subtype of fibrous joint where bones are connected by a fibrous ligament or interosseous membrane, classified functionally as an amphiarthrosis.

Gomphosis

A peg-in-socket fibrous joint subtype where a tooth is anchored into its socket by a periodontal ligament.

Synchondrosis

A primary cartilaginous joint in which bones are joined by hyaline cartilage, such as epiphyseal growth plates or the 1st rib and sternum junction.

Symphysis

A secondary cartilaginous joint where bones are joined by fibrocartilage, such as the pubic symphysis and intervertebral discs.

Hinge Joint

A uniaxial synovial joint operating in 1 plane (sagittal) allowing flexion and extension only, such as the elbow or ankle.

Pivot Joint

A uniaxial synovial joint operating in 1 plane (transverse) allowing rotation, such as the radioulnar joint.

Ball & Socket Joint

A multiaxial synovial joint operating in 3 planes (sagittal, coronal, transverse) allowing flexion, extension, abduction, adduction, and rotation, such as the hip joint.

Condyloid Joint

A biaxial synovial joint operating in 2 planes (sagittal and coronal) allowing flexion, extension, abduction, and adduction, such as the metacarpophalangeal or wrist joints.

Saddle Joint

A biaxial synovial joint operating in 2 planes that permits flexion, extension, abduction, adduction, and opposition, exemplified by the 1st carpometacarpal (thumb) joint.

Gliding Joint

A nonaxial synovial joint that allows sliding movements between bone surfaces without rotation around an axis, such as intercarpal joints.

Joint Congruency

The degree to which articulating bone surfaces fit together; high congruency increases stability but restricts range of motion, whereas low congruency increases mobility at the expense of stability.

Ligament

A connective tissue band connecting bone to bone that passively resists excessive movements that would stretch it.

Tendon

A connective tissue structure connecting muscle to bone that transmits muscle contraction force to move or stabilise a joint.

Compartment Rule

The anatomical organization where muscles with a common function at a joint are grouped together, sharing the same nerve and blood supply, and delimited by connective tissue septa.

Active Tension

Tension generated within a muscle while it actively contracts.

Passive Tension

Tension generated by the stretching of connective tissue within a lengthening muscle.

Muscle Tone

Baseline reflexive low-level muscular contraction driven by nervous innervation that maintains postural readiness.

Circular Muscle

A muscle fibre arrangement forming concentric rings around an opening, functioning to close or control openings (e.g., orbicularis oris).

Convergent Muscle

A muscle with a broad origin converging into a single central tendon, providing versatile pull directions (e.g., pectoralis major).

Parallel Muscle

A strap-like muscle with fascicles running parallel to its long axis, offering a large range of motion with less force (e.g., sartorius).

Fusiform Muscle

A spindle-shaped muscle with parallel fibres, a widened central belly, and tapered ends, producing more force than parallel muscles while maintaining range of motion (e.g., biceps brachii).

Pennate Muscle

A muscle arrangement with short fibres running obliquely into a central tendon, maximizing force output at the expense of shortening range (unipennate, bipennate, multipennate).

Open-Chain Movement

A kinetic chain movement in which the distal segment of the limb is free to move through space while the proximal segment remains fixed (e.g., leg extension machine).

Closed-Chain Movement

A kinetic chain movement in which the distal segment of the limb is planted or fixed against a surface, causing proximal segments to move (e.g., squat).

Prime Mover (Agonist)

The main muscle responsible for producing a given movement, contracting concentrically.

Antagonist

A muscle that opposes the movement of the prime mover, lengthening or contracting eccentrically to control and smooth out the motion.

Fixator

A muscle that contracts isometrically to fix or stabilise a joint or bone, establishing a firm base for the prime mover.

Synergist

A muscle that assists the prime mover by adding force or stabilizing surrounding joints during a movement.