Human Anatomy: Exam 2 Comprehensive Vocabulary Review

Comprehensive practice flashcards defining essential terminology, anatomical structures, and physiological processes covering muscle tissue, skeletal muscles, blood, the heart, vasculature, and the lymphatic system.

Excitability

The ability of muscle tissue to respond to stimulation (react).

Contractility

The capacity of a muscle to contract (shorten) and generate pulling force.

Elasticity

The property of muscle tissue that enables it to recoil and return to its original shape and length after being stretched.

Extensibility

The ability of muscle tissue to stretch or extend beyond its resting length without damage.

Deep Fascia

A dense connective tissue layer that surrounds, binds together, and separates muscles, allowing them to glide smoothly relative to each other.

Endomysium

The delicate, innermost layer of connective tissue that wraps and electrically insulates each individual muscle fiber.

Perimysium

The connective tissue sheath that encircles bundles of muscle fibers, organizing them into discrete structures termed fascicles.

Epimysium

A continuous layer of dense irregular connective tissue that encloses the entire skeletal muscle exterior.

Sarcomere

The functional contractile unit of a skeletal muscle myofibril, demarcated from one Z disc to the next adjacent Z disc.

Z Disc

A transverse protein boundary marking the borders of a sarcomere and serving as the anchoring site for thin filaments.

A Band

The dark central striation of a sarcomere corresponding to the entire length of the thick filaments (myosin).

I Band

The light band on either side of the Z disc containing only thin filaments (actin); it narrows and disappears during muscle contraction.

H Zone

The pale, central region within the A band that contains thick filaments only and vanishes entirely upon complete muscle contraction.

M Line

A protein meshwork situated at the center of the H zone and A band that provides an anchoring attachment for thick filaments.

Neuromuscular Junction (NMJ)

The specialized synapse where a motor neuron meets a skeletal muscle fiber to deliver action potentials via acetylcholine (ACh).

Motor Unit

A functional entity consisting of a single motor neuron together with all the skeletal muscle fibers it innervates.

All-or-None Principle

The principle stating that an individual muscle fiber either contracts completely or does not contract at all once its threshold stimulus is reached.

Isometric Contraction

A muscle contraction where internal tension is less than or equal to resistance, leaving muscle length unchanged with zero joint movement produced.

Isotonic Contraction

A muscle contraction where tension exceeds resistance, causing the muscle to shorten or lengthen and resulting in movement.

Muscle Tone

The continuous, passive, low-level state of partial contraction maintained in resting skeletal muscles to support posture and stabilize joints.

Muscle Atrophy

A reduction in muscle size, tone, and power caused by inactivity, lack of neural stimulation, or disease.

Muscle Hypertrophy

An enlargement of total muscle size resulting from an increased diameter of existing muscle fibers due to exercise.

Type I Skeletal Muscle Fibers

Slow oxidative fibers characterized by slow contraction speed, high endurance, rich myoglobin content, and high resistance to fatigue.

Type IIx Skeletal Muscle Fibers

Fast glycolytic fibers specialized for rapid, powerful force generation via anaerobic metabolism that fatigue quickly.

Agonist (Prime Mover)

The principal muscle that contracts to produce a specified movement (such as the biceps brachii during arm flexion).

Antagonist

A muscle whose action directly opposes or resists that of an agonist (such as the triceps brachii opposing biceps flexion).

Synergist

A muscle that assists the prime mover by delivering additional pulling force or steadying the joint.

Fixator

A muscle that stabilizes the origin of the agonist by immobilizing a bone or joint.

Axial Muscles

Skeletal muscles that originate and insert entirely on the axial skeleton, functioning to control the head, vertebral column, chewing, breathing, and abdominal wall.

Appendicular Muscles

Skeletal muscles comprising approximately $40\%$ of total skeletal muscle mass that stabilize and produce movements in the limbs and pectoral and pelvic girdles.

Frontal Belly of Occipitofrontalis

The anterior muscular portion of the epicranius responsible for wrinkling the forehead skin and raising the eyebrows.

Platysma

A superficial, thin neck muscle that draws the lower lip inferiorly and tenses the skin covering the anterior neck.

Extrinsic Eye Muscles

A group of six extraocular muscles (superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique) that originate in the orbit and control eye movement.

Muscles of Mastication

Muscles that act across the temporomandibular joint to move the mandible during chewing, primarily comprising the masseter and temporalis.

Pharyngeal Constrictors

Circular muscles forming the wall of the pharynx (superior, middle, inferior) that initiate swallowing by forcing food boluses down into the esophagus.

Diaphragm

The internally placed, dome-shaped partition between the thoracic and abdominal cavities whose contraction increases thoracic dimensions during inhalation.

External Intercostals

Muscles running between adjacent ribs that contract to elevate the ribs and assist inhalation.

Internal Intercostals

Muscles positioned deep to the external intercostals whose contraction depresses the ribs during forced exhalation.

Quadriceps Femoris

The anterior thigh muscle group composed of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, which extends the leg at the knee via the patellar ligament.

Hamstrings

The posterior thigh muscle group consisting of the biceps femoris, semitendinosus, and semimembranosus, which acts primarily to flex the leg.

Hematocrit

The clinical percentage of total whole blood volume occupied by erythrocytes (red blood cells).

Blood Plasma

The liquid extracellular matrix constituting approximately $55\%$ of whole blood, containing $92\%$ water, $7\%$ plasma proteins, and $1\%$ dissolved solutes.

Serum

The residual liquid of blood plasma remaining after the removal of clotting factors and fibrinogen.

Albumin

The most abundant plasma protein ($58\%$ of plasma proteins), which maintains osmotic pressure in the blood and transports lipophilic substances.

Fibrinogen

A major plasma protein ($4\%$ of total plasma protein) converted into insoluble fibrin strands during coagulation to form blood clots.

Hemoglobin

A red, iron-bearing protein inside erythrocytes comprising four globin chains ($\alpha_1, \alpha_2, \beta_1, \beta_2$), each containing a heme group that reversibly binds oxygen.

Transferrin

A circulating blood plasma protein that transports iron ions ($Fe$) released during erythrocyte degradation back to the liver and bone marrow.

Ferritin

A primary cellular storage protein that sequesters excess iron ions in the liver.

Bilirubin

A yellowish breakdown product of biliverdin (derived from heme) that is carried to the liver and secreted into bile.

Type AB Blood

The ABO blood phenotype featuring both A and B surface antigens on erythrocytes and lacking both anti-A and anti-B antibodies in plasma.

Type O Blood

The ABO blood phenotype where red blood cells display neither A nor B antigens, and plasma carries both anti-A and anti-B antibodies.

Agglutination

The cross-linking and clumping of red blood cells caused by matching antibodies binding to specific erythrocyte surface antigens during an incompatible transfusion.

Monocytes

Large agranular leukocytes ($3\text{--}8\%$ of total WBCs) containing kidney-shaped nuclei that differentiate into phagocytic macrophages upon leaving the bloodstream.

Thrombocytes

Enucleated, membrane-enclosed cytoplasmic fragments ($2\,\mu\text{m}$ in diameter) derived from megakaryocytes that circulate for $10\text{--}12$ days and participate in hemostasis.

Pulmonary Circuit

The cardiovascular circuit carrying deoxygenated blood from the right ventricle to the lungs for gas exchange and returning oxygenated blood to the left atrium.

Systemic Circuit

The cardiovascular circuit transporting oxygenated blood from the left ventricle through the aorta to all peripheral tissues and returning deoxygenated blood to the right atrium.

Epicardium

The visceral layer of the serous pericardium forming the outermost wall of the heart, composed of simple squamous epithelium overlying areolar connective tissue and fat.

Myocardium

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

Endocardium

The delicate internal endothelial lining covering the heart chambers and cardiac valves.

Intercalated Discs

Intercellular connections uniting adjacent cardiac muscle cells, consisting of desmosomes to distribute mechanical stress and gap junctions to conduct electrical impulses.

Tricuspid Valve

The three-cusp right atrioventricular valve that prevents regurgitation of blood into the right atrium during right ventricular systole.

Bicuspid (Mitral) Valve

The two-cusp left atrioventricular valve regulating blood transit from the left atrium into the left ventricle.

Pulmonary Semilunar Valve

The valve consisting of three pocket-like semilunar cusps guarding the entrance into the pulmonary trunk from the right ventricle.

Aortic Semilunar Valve

The valve located at the base of the aorta that prevents backflow of blood into the left ventricle during ventricular diastole.

Systole

The contraction phase of a heart chamber (atrial or ventricular) during which blood is forced into another chamber or a great vessel.

Diastole

The relaxation phase of the cardiac cycle during which a chamber relaxes and fills with blood.

Sinoatrial (SA) Node

The specialized cardiac tissue in the posterior wall of the right atrium that acts as the primary pacemaker of the heart, initiating autorhythmic impulses.

Atrioventricular (AV) Node

A cluster of specialized cells in the floor of the right atrium that briefly delays the electrical impulse before passing it to the ventricles.

Atrioventricular Bundle (Bundle of His)

A bundle of specialized cardiac fibers conducting electrical impulses from the AV node into the interventricular septum, splitting into right and left bundle branches.

Purkinje Fibers

Specialized, fast-conducting muscle fibers extending through the ventricular walls that distribute cardiac impulses throughout the ventricular myocardium.

Coronary Sinus

A large venous vessel on the posterior surface of the heart that collects venous blood from cardiac veins and empties directly into the right atrium.

Tunica Intima

The innermost tunic of a blood vessel wall, composed of a simple squamous endothelial lining supported by a subendothelial connective tissue layer.

Tunica Media

The middle tunic of a blood vessel wall, predominantly composed of circular smooth muscle fibers and elastic laminae that govern vasoconstriction and vasodilation.

Tunica Externa

The outer connective tissue sheath of a blood vessel that stabilizes the vessel and anchors it to neighboring anatomical structures.

Elastic Arteries

The largest conducting arteries (such as the aorta) characterized by abundant elastic fibers across all tunics, allowing them to stretch during ventricular systole and recoil during diastole.

Metarteriole

A vascular branch issuing from an arteriole that feeds into a capillary bed, lined at each capillary entrance by precapillary sphincters.

Skeletal Muscle Pump

A physiological mechanism where the cyclic contraction of skeletal muscles compresses deep veins, driving venous blood upward toward the heart through one-way valves.

Circle of Willis

An arterial anastomosis surrounding the sella turcica that equalizes blood pressure in the brain and provides collateral circulation pathways.

Hepatic Portal System

A specialized venous circulation system that directs nutrient-rich, deoxygenated blood draining from digestive organs through the hepatic portal vein into the liver for metabolic processing.

Celiac Trunk

An unpaired anterior branch from the descending abdominal aorta that splits to supply the stomach, liver, gallbladder, and spleen.

Lacteals

Specialized lymphatic capillaries located in the villi of the small intestine that absorb dietary fats and fat-soluble vitamins.

Chyle

The milky fluid collected by lacteals within the small intestine consisting of lymph mixed with absorbed dietary emulsified fats.

Cisterna Chyli

A dilated saclike structure at the inferior base of the thoracic duct that receives lymph from lumbar trunks and the intestinal trunk.

Thoracic Duct

The major lymphatic trunk draining lymph from the left side of the head and neck, left upper limb, left thorax, and the entire body inferior to the diaphragm into the left subclavian vein.

Right Lymphatic Duct

The short lymphatic duct that empties lymph from the right upper quadrant of the body into the junction of the right internal jugular and right subclavian veins.

Lymph Nodes

Small, encapsulated, bean-shaped secondary lymphatic organs located along lymphatic channels that filter foreign particles and house lymphocytes and macrophages.

Spleen

The largest secondary lymphatic organ in the body, serving to filter whole blood, phagocytize aged red blood cells, and coordinate immune responses.

Thymus

A bilobed primary lymphatic organ in the superior mediastinum where pre-T-lymphocytes mature into immunocompetent T-lymphocytes.

Tonsils

Non-encapsulated lymphoid aggregations (palatine, pharyngeal, and lingual) arranged in a ring around the pharynx that protect against pathogens entering through the mouth and nose.