Comprehensive Anatomy and Physiology Review: Skeletal, Articular, Respiratory, Muscular, Cardiovascular, and Lymphatic Systems

A comprehensive vocabulary review of core anatomical structures, physiological processes, and pathological states across the skeletal, articular, respiratory, muscular, cardiovascular, and lymphatic systems.

Axial skeleton

The skeletal division consisting of $80$ bones forming the central axis of the body, including the skull, vertebral column, and thoracic cage.

Appendicular skeleton

The skeletal division consisting of $126$ bones comprising the upper and lower limbs and their supporting girdles.

Epiphysis

An expanded end of a long bone, categorized as proximal when closer to the trunk or distal when farther from the trunk.

Diaphysis

The shaft or long central tubular portion of a long bone.

Epiphyseal plate

A plate of hyaline cartilage located within the metaphysis responsible for the lengthwise growth of a long bone.

Articular cartilage

Hyaline cartilage covering the articular surfaces of epiphyses that reduces friction and absorbs shock within joints.

Osteon (Haversian system)

The basic structural and functional unit of compact bone, consisting of concentric lamellae arranged around a central canal.

Canaliculi

Tiny micro-channels connecting adjacent lacunae that facilitate transport of nutrients, metabolic wastes, and cellular communication between osteocytes.

Intramembranous ossification

The developmental process wherein bone forms directly within sheetlike layers of embryonic connective tissue, giving rise to broad, flat bones such as most skull bones.

Endochondral ossification

The developmental process wherein bone tissue forms by progressively replacing a pre-existing hyaline cartilage model.

Osteoblasts

Bone-building cells that synthesize and deposit new organic bone matrix.

Osteoclasts

Large multinucleated cells that resorb, dissolve, and break down bone matrix.

Bone resorption

The breakdown and enzymatic removal of bone tissue, carried out primarily by osteoclasts and stimulated by parathyroid hormone (PTH).

Bone deposition

The continuous formation and mineralization of new bone tissue, performed primarily by osteoblasts and promoted by calcitonin.

Parathyroid hormone (PTH)

A peptide hormone secreted by the parathyroid glands that elevates blood calcium levels by stimulating osteoclast-mediated bone resorption.

Calcitonin

A hormone secreted by the thyroid gland that helps lower blood calcium levels and is associated with reduced bone resorption.

Rickets

A pediatric metabolic bone disorder characterized by defective mineralization of growing bones, classically caused by vitamin D deficiency.

Osteomalacia

A metabolic condition characterized by inadequate mineralization of adult bone matrix, resulting in softened and structurally weakened bones.

Osteopenia

A clinical state characterized by lower than normal bone mineral density that does not yet meet the diagnostic threshold for osteoporosis.

Osteoporosis

A skeletal disorder characterized by marked loss of bone mass and architectural deterioration, making bones susceptible to fragility fractures.

Syndesmosis

A fibrous amphiarthrotic joint in which bones are bound together by a sheet or bundle of dense connective tissue, such as the interosseous membrane between the tibia and fibula.

Gomphosis

A specialized fibrous joint where a cone-shaped bony peg fits into a socket, anchoring each tooth via the periodontal ligament.

Synchondrosis

A cartilaginous joint in which bones are united by a band of hyaline cartilage, exemplified by the epiphyseal plate and the first costosternal joint.

Symphysis

A cartilaginous joint in which opposing bone ends are capped with hyaline cartilage and joined by a broad, resilient pad of fibrocartilage, such as the pubic symphysis.

Meniscus

A crescent-shaped fibrocartilage pad located within certain synovial joints (such as the knee) that cushions, distributes compressive loads, and deepens the articular surface.

Bursa

A fluid-filled fibrous sac lined with synovial membrane that cushions and minimizes frictional wear between tendons, ligaments, and bones.

Colles' fracture

A fracture of the distal radius at the wrist, characteristically caused by a fall onto an outstretched hand.

Greenstick fracture

An incomplete fracture in which the bone bends and breaks only on one cortical surface, occurring frequently in children due to increased skeletal flexibility.

Comminuted fracture

A fracture pattern where the affected bone is shattered or splintered into three or more distinct fragments, typically caused by high-energy trauma.

Fibrocartilaginous callus

A temporary reparative bridge of collagen fibers and fibrocartilage produced by fibroblasts and chondroblasts during the second stage of bone healing.

Bony callus

A rigid mass of newly formed woven bone synthesized by osteoblasts that replaces the soft fibrocartilaginous callus starting around $3$ weeks post-injury.

Mucosa

A mucus-producing, moist epithelial membrane lining passages that open to the exterior, functioning to entrap inhaled foreign particles.

Epiglottis

A spoon-shaped flap of elastic cartilage positioned at the superior entrance of the larynx that folds during swallowing to shield the airway and route food into the esophagus.

Respiratory membrane

The ultra-thin air-blood barrier separating alveolar air from capillary blood, across which $O_2$ and $CO_2$ rapidly diffuse.

Surfactant

A lipid-protein secretion lining the gas-exposed luminal surface of alveoli that lowers surface tension to prevent alveolar collapse during exhalation.

Tidal volume (TV)

The volume of air inspired or expired during a single resting, quiet respiratory cycle, averaging approximately $500\,mL$.

Residual volume (RV)

The volume of air permanently remaining within the lungs following a maximal forced expiration, averaging approximately $1{,}200\,mL$.

Emphysema

A chronic pulmonary disease marked by irreversible destruction of alveolar septa, airspace enlargement, loss of elastic recoil, and air trapping.

Chronic bronchitis

An obstructive pulmonary disorder characterized by chronic inflammation of the lower respiratory mucosa, goblet cell hyperplasia, and excessive mucus pooling.

Epimysium

The outermost dense connective tissue sheath enclosing an entire skeletal muscle organ.

Perimysium

The connective tissue partition that bundles individual skeletal muscle fibers together into a fascicle.

Endomysium

The delicate connective tissue layer that envelopes each individual skeletal muscle fiber (muscle cell).

Sarcomere

The structural and functional contractile unit of a myofibril, defined as the repeating segment bounded between two successive Z discs.

Sarcoplasmic reticulum (SR)

A modified smooth endoplasmic reticulum forming a network around myofibrils that stores and releases calcium ions ($Ca^{2+}$) to regulate contraction.

Transverse (T) tubule

A deep, invaginated tubular extension of the sarcolemma that conducts electrical action potentials into the interior of a muscle fiber.

Neuromuscular junction (NMJ)

The specialized synapse where the axon terminal of a somatic motor neuron meets the motor end plate of a skeletal muscle fiber.

Motor unit

A functional neuromuscular entity consisting of a single somatic motor neuron and all the skeletal muscle fibers it innervates.

Creatine phosphate

A high-energy phosphagen stored in skeletal muscle that rapidly donates a phosphate group to ADP, regenerating ATP during initial short bursts of contraction.

Excess post-exercise oxygen consumption (EPOC)

The elevated rate of oxygen uptake following exercise that covers the oxygen debt and fuels systemic physiological recovery processes.

Isotonic contraction

A muscular contraction where tension remains constant while muscle length changes to generate mechanical movement, subdivided into concentric and eccentric actions.

Isometric contraction

A muscular contraction where internal tension develops and matches resistance without changing overall muscle length or moving a joint.

Pericardium

The double-walled fibroserous sac enclosing the heart, consisting of an outer fibrous pericardium and an inner serous pericardium.

Myocardium

The thick middle layer of the heart wall composed of specialized cardiac muscle tissue responsible for myocardial pumping action.

Endocardium

The glistening inner endothelial lining covering the heart chambers, myocardial trabeculae, and heart valves.

Fossa ovalis

An oval depression on the right atrial interatrial septum representing the closed fibrous remnant of the fetal foramen ovale.

Chordae tendineae

Fibrous, tendon-like cords anchoring the free margins of atrioventricular valve cusps to the ventricular papillary muscles.

Papillary muscles

Conical muscular projections arising from the ventricular myocardium that contract during systole to prevent eversion of the AV valves.

Systemic circulation

The circulatory division in which the left ventricle ejects oxygen-rich blood into the aorta to supply body tissues, returning deoxygenated blood to the right atrium.

Pulmonary circulation

The circulatory division in which the right ventricle ejects deoxygenated blood through the pulmonary trunk to the lungs, returning oxygenated blood to the left atrium.

Sinoatrial (SA) node

The primary physiological pacemaker of the cardiac conduction system, located in the superior right atrial wall, that spontaneously initiates action potentials.

P wave

The ECG deflection representing the wave of electrical depolarization spreading across both atria from the sinoatrial node.

QRS complex

The prominent ECG waveform representing rapid electrical depolarization of both ventricles prior to ventricular systole.

T wave

The ECG wave representing ventricular repolarization occurring immediately before ventricular diastole.

Stroke volume (SV)

The quantity of blood ejected from a ventricle during a single ventricular systolic contraction, determined by the formula $\text{SV} = \text{EDV} - \text{ESV}$.

Cardiac output (CO)

The total volume of blood pumped from a single ventricle into the systemic or pulmonary arterial system per minute, determined by $\text{CO} = \text{SV} \times \text{HR}$.

Thoracic duct

The principal lymphatic trunk that collects lymph from the entire left half of the body, the right side below the ribs, and the right lower extremity, emptying into the venous system at the left internal jugular and subclavian vein junction.

Primary lymphatic organs

The specialized anatomical sites where lymphocytes originate and achieve immunocompetence, namely red bone marrow and the thymus.

Secondary lymphatic organs

Sites where immunocompetent lymphocytes reside, encounter antigens, and execute immune responses, including lymph nodes, the spleen, and lymphatic nodules.

Thymus

A bilobed primary lymphatic organ in the superior mediastinum behind the manubrium where immature pre-T cells undergo differentiation and maturation.

White pulp

The splenic parenchymal tissue consisting of perivascular lymphoid aggregates that monitor systemic blood for pathogens and mount adaptive immune defenses.

Red pulp

The vascular splenic parenchymal tissue comprising venous sinuses and splenic cords, functioning to filter foreign matter, remove senescent erythrocytes, and store platelets.