General Anatomy: Directions, Tissues, Bones, Joints, and Muscles

Vocabulary practice flashcards covering basic anatomical terminology, directional terms, body planes and axes, movements, primary tissue types, bone structures, ossification, joint classifications, and muscle tissue physiology.

Proximal

Situated closer to the trunk or point of origin near the center of the body.

Distal

Situated farther away from the trunk or point of origin, away from the center of the body.

Medial

Positioned toward the midline or center plane of the body.

Lateral

Positioned toward the outer side or away from the midline of the body.

Sagittal Plane

An anatomical plane that divides the body vertically into right and left portions.

Frontal Plane (Coronal Plane)

An anatomical plane that divides the body into front (anterior/ventral) and back (posterior/dorsal) sections.

Transverse Plane (Horizontal Plane)

An anatomical plane that divides the body horizontally into upper (superior) and lower (inferior) sections.

Extension

A movement that increases the angle between body parts, straightening a limb.

Flexion

A movement that decreases the angle between body parts, bending a limb.

Anteversion

Movement of an extremity forward (ventrally) within the sagittal plane.

Retroversion

Movement of an extremity backward (dorsally) within the sagittal plane.

Abduction

Movement of a limb away from the midline of the body within the frontal plane.

Adduction

Movement of a limb toward the midline of the body within the frontal plane.

Pronation

Inward rotation of the forearm or foot.

Supination

Outward rotation of the forearm or foot.

Epithelial Tissue

A primary tissue type characterized by high cell density and minimal extracellular matrix, specialized for coverage, protection, and secretion.

Connective and Supportive Tissue

A primary tissue type composed of few cells separated by abundant extracellular matrix, providing structural support, connection, and padding.

Loose Collagenous Connective Tissue

The most widespread connective tissue in the body, forming the structural framework (interstitium) of organs, organ walls, and protective sheaths around neurovascular bundles.

Dense Collagenous Connective Tissue

A tough connective tissue dominated by Type I collagen fibers, providing high tensile strength in mechanically stressed structures such as tendons, ligaments, and fasciae.

White Adipose Tissue

Fat tissue composed of large adipocytes containing a single large lipid droplet that pushes the nucleus to the cell border (signet-ring appearance); functions as structural padding, energy storage, thermal insulation, and estrogen synthesis via aromatase.

Osteogenesis Imperfecta

A genetic disorder caused by mutations leading to defective synthesis of Type I collagen, making bones extremely brittle and susceptible to fractures under minimal stress.

Scurvy

A nutritional deficiency of Vitamin C (ascorbic acid) that impairs collagen synthesis by preventing proline and lysine hydroxylation, leading to breakdown of the periodontal ligament and loss of teeth.

Tendon (Tendo)

An active connective tissue structure connecting muscle to bone that transmits muscular force to the skeletal system.

Ligament (Ligamentum)

A passive connective tissue structure made of dense collagenous fibers that connects bone to bone across joints.

Bursa (Bursa Synovialis)

A fluid-filled cushion lined with synovial membrane, located between bony prominences and tendons or muscles to reduce friction and cushion compression loads.

Tendon Sheath (Vagina Tendinis)

A tubular, double-layered connective tissue wrapping surrounding long tendons to provide a low-friction guide for smooth movement.

Fascia

An outer sheath of dense collagenous connective tissue that wraps around individual muscles or muscle groups to separate them and facilitate movement.

Hyaline Cartilage

An avascular, pressure-elastic cartilage consisting of $80\%$ water and $20\%$ macromolecules ($60\%$ Type II collagen and $30\%$ proteoglycans like aggrecan), serving as articular surfaces and growth zones.

Chondron

The basic functional histological unit of cartilage, consisting of chondrocytes and their surrounding pericellular extracellular matrix.

Fibrocartilage

A dense, fiber-rich cartilage containing visible collagen fibers that provides both high tensile strength and pressure resistance, found in intervertebral discs, menisci, and the pubic symphysis.

Elastic Cartilage

A flexible cartilage rich in elastic fibers that easily bends and rebounds into shape, found in the auricle of the ear, epiglottis, and bronchi.

Diaphysis

The central shaft of a long bone, primarily constructed of thick compact bone surrounding the marrow cavity.

Epiphysis

The expanded articular end of a long bone, containing internal spongy bone filled with red bone marrow.

Periosteum

A two-layered connective tissue membrane covering the outer surface of bone, supplying blood vessels, nerves, and osteoblasts required for bone nourishment and repair.

Substantia Spongiosa (Trabecular Bone)

A porous internal meshwork of thin bone trabeculae oriented along primary lines of mechanical force (trajectorial alignment).

Substantia Compacta (Cortical Bone)

The dense, rigid outer shell of bone made of tightly packed structural units called osteons.

Osteon (Haversian System)

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

Osteoblast

A bone-forming cell responsible for synthesizing and secreting organic bone matrix (osteoid).

Osteoclast

A large, multinucleated cell that resorbs bone matrix by secreting $H^+$ ions and $Cl^-$ (creating an acidic environment at $\text{pH } 4.5$) and lysosomal enzymes.

Desmal Ossification

Direct intramembranous bone development, where bone tissue forms directly through calcium deposition into a mesenchymal precursor plate.

Enchondral Ossification

Indirect bone formation, where a embryonic hyaline cartilage model is gradually mineralized and replaced by bone tissue.

Diarthrosis (True Joint)

A freely movable joint characterized by a joint cavity (Gelenkspalt) separating articular surfaces covered in cartilage, enclosed by a joint capsule containing synovial fluid.

Synarthrosis (False Joint)

A continuous, immovable or slightly movable bone junction lacking a joint cavity, where bones are joined directly by connective tissue, cartilage, or bone.

Syndesmosis

A fibrous synarthrosis where opposing bones are connected by dense connective tissue ligaments or membranes (e.g., interosseous membrane).

Synchondrosis

A cartilaginous synarthrosis where bones are connected by hyaline cartilage or fibrocartilage (e.g., pubic symphysis, costal cartilage).

Synostosis

A bony joint formed when separate bones fuse completely into a single bone via ossification (e.g., fused sacral vertebrae).

Hinge Joint (Scharniergelenk)

A uniaxial diarthrosis that permits motion in a single axis, allowing flexion and extension movements (e.g., elbow joint).

Pivot Joint (Radgelenk / Zapfengelenk)

A uniaxial diarthrosis that permits rotation around a single longitudinal axis (e.g., proximal radioulnar joint).

Saddle Joint (Sattelgelenk)

A biaxial diarthrosis with complementary concave and convex surfaces that allows movement along two axes (e.g., carpometacarpal joint of the thumb).

Ball-and-Socket Joint (Kugelgelenk)

A multiaxial diarthrosis with a rounded bone head fitting into a cuplike cavity, allowing movement across three axes (e.g., shoulder joint).

Skeletal Muscle

Striated, voluntary muscle tissue composed of long multinucleated fibers with peripheral nuclei, organized into functional units called sarcomeres with T-tubules forming triads.

Cardiac Muscle

Striated, involuntary muscle tissue consisting of branched cells connected by intercalated discs with gap junctions, containing central nuclei and T-tubules forming dyads.

Smooth Muscle

Non-striated, involuntary muscle tissue composed of spindle-shaped cells with a single central nucleus and caveolae, located in blood vessels and internal organ walls.

Red Postural Muscle (Rote Haltemuskulatur)

Skeletal muscle dominated by slow-twitch (Type I) fibers rich in mitochondria and myoglobin, adapted for continuous endurance via aerobic metabolism and prone to contracture if unused.

White Phasic Muscle (Weiße Bewegungsmuskulatur)

Skeletal muscle dominated by fast-twitch (Type II) fibers rich in glycogen, adapted for rapid, powerful contractions via anaerobic metabolism and prone to atrophy if unused.