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

Comprehensive vocabulary flashcards reviewing the anatomical structures and physiological functions of the axial and appendicular skeletons, articulations, muscular system, heart, systemic and pulmonary blood vessels, lymphatic system, and respiratory tract.

Calvaria

The skullcap or domelike superior portion of the cranium (cranial vault), comprising the superior portions of the frontal, parietal, and occipital bones.

Sphenoid Bone

The keystone bone of the cranium that articulates with almost all other cranial bones; it forms the base of the cranium, contributes to the middle cranial fossa and orbits, and contains the sella turcica, pterygoid processes, and optic canals.

Crista Galli

A prominent vertical process of the ethmoid bone sitting atop the cribriform plate that serves as the attachment point for the falx cerebri, a dural membrane fold.

Hyoid Bone

A U-shaped bone in the anterior cervical neck inferior to the mandible that does not articulate directly with any other bone; it is tethered by stylohyoid ligaments to the styloid processes of the temporal bones and acts as a movable base for the tongue.

Auditory Ossicles

Three tiny bones located in the middle ear cavity—the malleus (hammer), incus (anvil), and stapes (stirrup)—that transmit sound vibrations from the tympanic membrane to the oval window.

Permanent Teeth

The adult set of 32 teeth consisting of 8 incisors, 4 canines, 8 premolars, and 12 molars (expressed by the dental formula $2I, 1C, 2P, 3M \times 2$), which replace childhood deciduous milk teeth.

Intervertebral Disc

A cushion-like pad between adjacent vertebrae functioning as a shock absorber; composed of an inner gelatinous sphere (the nucleus pulposus) surrounded by an outer collar of about 12 concentric rings of collagen and fibrocartilage (the anulus fibrosus).

Atlas (C1)

The first cervical vertebra, which lacks a body and a spinous process; consists of anterior and posterior arches and lateral masses that articulate with the occipital condyles of the skull to allow nodding the head 'yes'.

Dens (Odontoid Process)

A tooth-like projection arising superiorly from the body of the axis (C2) into the anterior arch of the atlas (C1), acting as a pivot for lateral rotation of the skull ('no' movement).

Sternal Angle

A prominent horizontal ridge on the anterior surface of the sternum where the manubrium meets the body; acts as a fibrocartilage hinge allowing the sternum to swing during inhalation, lying at the level of the T4–T5 intervertebral disc and the second costal cartilage.

Floating Ribs

Rib pairs 11 and 12, which are false ribs that have no anterior attachment to the sternum; their costal cartilages lie embedded in the muscular tissue of the lateral body wall.

Pectoral Girdle

The shoulder girdle, composed of a clavicle anteriorly and a scapula posteriorly; it attaches the upper limb to the axial skeleton exclusively at the sternoclavicular joint, providing exceptional mobility at the expense of stability.

Glenoid Cavity

A shallow, pear-shaped fossa on the lateral angle of the scapula that articulates with the head of the humerus to form the glenohumeral (shoulder) joint.

Acetabulum

A deep, cup-shaped hemispherical socket located on the lateral aspect of the pelvic girdle at the junction of the ilium, ischium, and pubis; articulates with the spherical head of the femur.

Carpal Bones

The eight short wrist bones arranged in two transverse rows: a proximal row (scaphoid, lunate, triquetrum, pisiform) and a distal row (trapezium, trapezoid, capitate, hamate).

Talus

The second largest tarsal bone, situated proximally in the tarsus; its pulley-shaped trochlea articulates with the tibia and fibula to transmit body weight onto the calcaneus and the rest of the foot.

Hallux

The great toe (digit I) of the foot, which contains only two phalanges (proximal and distal), unlike the other digits which contain three.

Synarthrosis

A functional classification designating an immovable joint; largely restricted to the axial skeleton, such as sutures in the skull.

Syndesmosis

A structural fibrous joint in which articulating bones are united exclusively by ligaments or fibrous bands of collagen fibers, varying from completely immobile to slightly mobile (e.g., inferior tibiofibular joint).

Synovial Membrane

The inner layer of an articular capsule, made of loose connective tissue, that lines all internal surfaces of a synovial joint cavity not covered by hyaline cartilage and secretes lubricating synovial fluid.

Bursa

A flattened, closed fibrous sac lined by a synovial membrane and filled with synovial fluid; functions like a ball bearing to reduce friction where ligaments, muscles, skin, tendons, or bones rub against each other.

Articular Disc (Meniscus)

A pad of fibrocartilage extending inward from the joint capsule to separate the synovial cavity into subcompartments, evening the compressive load and improving bone fit (e.g., in the TMJ, sternoclavicular, and knee joints).

Circumduction

A movement combining flexion, abduction, extension, and adduction in sequence so that the distal end of a limb or digit moves in a circle while the proximal attachment describes the apex of a cone.

Dorsiflexion

Lifting the foot at the ankle so that its superior (dorsal) surface approaches the anterior shin, as occurs when standing or walking on the heels.

Cruciate Ligaments

Two intracapsular knee ligaments (the Anterior Cruciate Ligament and Posterior Cruciate Ligament) that cross each other in the intercondylar area to prevent anterior and posterior displacement of the tibia relative to the femur.

Perimysium

A layer of fibrous connective tissue that surrounds each fascicle, which is a discrete bundle of muscle fibers within a skeletal muscle organ.

Sarcomere

The fundamental microscopic contractile unit of a muscle fiber, extending from one Z disc to the next, composed of ordered thick (myosin) and thin (actin) myofilaments.

Titin

A giant, spring-like elastic protein in sarcomeres extending from the Z disc to the thick filament and M line; it keeps thick filaments centered in the A band and refolds to restore resting length after stretching.

Triad

A complex within a skeletal muscle fiber formed by a central transverse (T) tubule invagination flanked on both sides by terminal cisterns of the sarcoplasmic reticulum at each A-I junction.

Sliding Filament Mechanism

The concentric contraction model in which myosin heads of thick filaments latch onto thin filaments and pull them toward the center of the sarcomere, causing the I bands to shorten while individual filament lengths remain unchanged.

Motor Unit

A single motor neuron along with all the individual skeletal muscle fibers that it innervates, which all contract concurrently when the neuron fires.

Neuromuscular Junction

The motor end plate where a motor neuron's terminal bouton meets a skeletal muscle fiber across a microscopic synaptic cleft, releasing acetylcholine to initiate an action potential.

Prime Mover (Agonist)

A muscle that bears the principal responsibility for causing a specific motion or movement across a joint.

Epicardium

The visceral layer of the serous pericardium forming the outermost tissue layer of the heart wall, frequently infiltrated with adipose tissue.

Crista Terminalis

A prominent internal C-shaped muscular ridge in the right atrium that demarcates the smooth-walled posterior section from the pectinate-muscled anterior region.

Trabeculae Carneae

Irregular, cross-crossing muscular ridges that line the internal myocardial walls of the right and left ventricles.

Cardiac Skeleton

A dense connective tissue structure that encircles the four heart valves, anchoring valve cusps, preventing dilation, anchoring myocardium, and electrically insulating the atria from the ventricles.

Sinoatrial (SA) Node

The crescent-shaped mass of specialized myocardial pacemaker cells located in the wall of the right atrium that spontaneously generates impulses to set the rhythm of the heartbeat.

Coronary Sinus

A wide venous channel running in the posterior coronary sulcus that receives deoxygenated blood from the great, middle, and small cardiac veins and empties directly into the right atrium.

Tunica Media

The middle layer of a blood vessel wall, composed predominantly of circularly arranged smooth muscle cells, elastin, and collagen fibers; regulates vessel diameter through vasoconstriction and vasodilation.

Precapillary Sphincter

A ring of smooth muscle encircling the root of each true capillary as it branches from a metarteriole, acting as a valve to regulate blood flow into the capillary bed according to tissue metabolic needs.

Celiac Trunk

A large, unpaired branch arising from the abdominal aorta directly below the diaphragm that splits into the left gastric, splenic, and common hepatic arteries to supply the foregut organs.

Hepatic Portal System

A specialized venous network that collects nutrient-rich, deoxygenated blood from the stomach, intestines, and spleen via the hepatic portal vein and routes it through liver sinusoids before it reaches the inferior vena cava.

Thoracic Duct

The largest lymphatic vessel of the body, which ascends from the cisterna chyli in the abdomen to drain lymph from the lower body, left thorax, left upper limb, and left head and neck into the junction of the left internal jugular and left subclavian veins.

Respiratory Mucosa

Pseudostratified ciliated columnar epithelium with goblet cells lining the nasal cavity, paranasal sinuses, nasopharynx, and trachea; secretes mucus to trap airborne debris and uses cilia to propel it toward the pharynx.

Epiglottis

A flexible, leaf-shaped flap of elastic cartilage attached to the thyroid cartilage of the larynx; during swallowing, it covers the laryngeal inlet to steer food into the esophagus.

Carina

An internal, highly sensitive cartilage ridge situated at the base of the trachea where it bifurcates into the left and right primary (main) bronchi; triggers a vigorous cough reflex when stimulated.

Type II Alveolar Cells

Cuboidal epithelial cells dispersed throughout the alveolar walls that synthesize and secrete pulmonary surfactant, a detergent-like mixture of lipids and proteins that decreases alveolar surface tension to prevent collapse.

Parietal Pleura

The outer serous membrane layer lining the internal surface of the thoracic wall, mediastinal enclosure, and superior diaphragm, which forms the outer boundary of the pleural cavity.

Pulmonary Ventilation

The mechanical process of breathing, consisting of inspiration and expiration, whereby cyclical volume and pressure changes in the thoracic cavity move atmospheric air into and out of the pulmonary alveoli.