Human Anatomy and Physiology: Organ Systems Review

Comprehensive vocabulary flashcards covering the anatomy and physiology of the cardiovascular, respiratory, lymphatic, digestive, nervous, endocrine, and urinary systems.

Pulmonary Circulation

The pathway of blood flow between the heart and lungs that oxygenates blood; it begins at the right ventricle and ends at the left atrium.

Systemic Circulation

The pathway of blood flow between the heart and the rest of the body that delivers oxygen to tissues; it begins at the left ventricle and ends at the right atrium.

Arteries

Blood vessels that carry blood away from the heart, characterized by thick walls, abundant smooth muscle and elastic tissue, smaller internal lumens, high internal pressure, and a lack of valves.

Veins

Blood vessels that carry blood toward the heart, characterized by thinner walls, less smooth muscle and elastic tissue, lower internal pressure, larger lumens, and valves to prevent backflow.

Heart Anatomy

The internal muscular pump of the cardiovascular system consisting of four chambers (right atrium, right ventricle, left atrium, left ventricle), separating septum, and valves (tricuspid, pulmonary, mitral, aortic).

Cardiac Conducting System

The specialized electrical pathway of the heart that coordinates contractions through the sequence: SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers.

Blood Plasma

The liquid extracellular component comprising approximately $55\%$ of whole blood, composed of approximately $90\text{--}92\%$ water.

Erythrocytes (Red Blood Cells)

Biconcave disc-shaped formed elements produced in red bone marrow that lack a nucleus and organelles, survive approximately $120\text{ days}$, and transport oxygen and carbon dioxide using hemoglobin.

Hemoglobin

An oxygen-binding protein inside erythrocytes consisting of four globin protein chains and four heme groups, each containing an $\text{Fe}^{2+}$ (iron) ion.

Platelets (Thrombocytes)

Small cell fragments derived from megakaryocytes in the bone marrow that play a critical role in hemostasis by forming plugs and initiating blood clotting.

Hemostasis

The physiological process of stopping bleeding following blood vessel injury, proceeding through platelet adhesion, platelet activation, platelet plug formation, and fibrin clot formation.

Conducting Zone

The portion of the respiratory tract that transports, warms, and humidifies air without participating in gas exchange; extends from the nose to the terminal bronchioles.

Respiratory Zone

The site within the respiratory system where gas exchange occurs, consisting of respiratory bronchioles, alveolar ducts, and alveoli.

Alveoli

Tiny, thin-walled air sacs in the lungs surrounded by pulmonary capillaries that facilitate gas exchange via diffusion across a short diffusion distance.

Pulmonary Ventilation

The mechanical process of moving air into and out of the lungs, comprising inspiration (inhalation) and expiration (exhalation).

Inspiration

The phase of ventilation during which the diaphragm contracts and flattens, external intercostal muscles contract, thoracic volume increases, pulmonary pressure decreases, and air flows into the lungs.

Expiration

The phase of ventilation during which the diaphragm relaxes upward, external intercostal muscles relax, thoracic volume decreases, pulmonary pressure increases, and air flows out of the lungs.

Lymph

A clear fluid collected from excess interstitial tissue fluid that contains lymphocytes, proteins, and fats, transported via lymphatic vessels back to the venous system.

Primary Lymphatic Organs

Sites where lymphocytes are produced and/or matured, specifically the red bone marrow and thymus.

Secondary Lymphatic Organs

Sites where mature immunocompetent cells encounter antigens and become activated, including lymph nodes, spleen, tonsils, and mucosa-associated lymphoid tissue (MALT).

Innate Immunity

Non-specific host defense mechanisms present from birth that provide an immediate response (minutes to hours) to pathogens without immunological memory.

Adaptive Immunity

Antigen-specific immune defense mediated by B cells and T cells that develops after antigen exposure, exhibits immunological memory, and mounts faster, stronger secondary responses.

B Lymphocytes (B cells)

Adaptive immune cells that provide antibody-mediated (humoral) immunity; upon activation, they differentiate into plasma cells that produce antibodies or memory B cells.

T Lymphocytes (T cells)

Adaptive immune cells responsible for cell-mediated immunity; include helper, cytotoxic, regulatory, and memory subtypes that coordinate immune responses and eliminate infected cells.

Peristalsis

Wave-like involuntary smooth muscle contractions of the alimentary tract that propel ingested food forward through the digestive system.

Lacteals

Specialized lymphatic capillaries located in the intestinal villi that absorb digested fats and lipid-soluble products.

Grey Matter

Nervous tissue composed primarily of neuronal cell bodies, dendrites, and unmyelinated axons that serves as the major site for central information processing.

White Matter

Nervous tissue composed primarily of myelinated axons, specialized for rapid transmission of nerve impulses between different regions.

Central Nervous System (CNS)

The primary processing and control division of the nervous system, consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The division of the nervous system consisting of all nervous tissue outside the brain and spinal cord, including cranial nerves, spinal nerves, ganglia, and sensory receptors.

Somatic Nervous System

The motor division of the peripheral nervous system that regulates voluntary contractions of skeletal muscles.

Autonomic Nervous System

The involuntary motor division of the PNS that regulates smooth muscle, cardiac muscle, and glands; subdivided into sympathetic, parasympathetic, and enteric divisions.

Anatomy of the Brain

The structural organization of the human brain, displaying the cerebral cortex lobes (frontal, limbic, parietal, occipital), corpus callosum, thalamus, hypothalamus, cerebellum, and brainstem.

Structure of a Neuron

The structural and functional unit of the nervous system, consisting of a cell body (soma), dendrites, axon hillock, axon, myelin sheath, nodes of Ranvier, and axon terminals with synaptic end bulbs.

Synaptic Transmission

The communication process across a neural synapse triggered by action potential arrival, voltage-gated $\text{Ca}^{2+}$ influx, synaptic vesicle exocytosis, and neurotransmitter binding to postsynaptic receptors.

Homeostasis

The body's physiological ability to maintain a relatively stable and constant internal environment despite fluctuating internal and external conditions.

Paracrine Signals

Locally active chemical messengers, such as histamine and prostaglandins, that diffuse through interstitial fluid to act on neighboring target cells.

Autocrine Signals

Chemical messengers that bind to receptors on and exert biological effects on the exact same cell that secreted them.

Anterior Pituitary

The glandular lobe of the pituitary gland controlled by hypothalamic hormones via portal blood vessels; synthesizes and secretes GH, TSH, ACTH, FSH, LH, and PRL.

Posterior Pituitary

The neural extension of the pituitary gland controlled directly by hypothalamic neurons; does not produce hormones but stores and releases oxytocin and ADH.

Nephron

The functional microscopic filtering unit of the kidney, anatomically subdivided into the renal corpuscle and the renal tubule.

Renal Corpuscle

The initial blood-filtering structure of the nephron, composed of a glomerulus (capillary knot) enveloped by a double-walled glomerular (Bowman's) capsule.

Renal Tubule

The tubular portion of the nephron through which filtrate flows, sequentially consisting of the proximal convoluted tubule (PCT), nephron loop (loop of Henle), and distal convoluted tubule (DCT).

Glomerular Filtration

The non-selective movement of water and small dissolved solutes from glomerular capillary blood into the glomerular capsule driven by blood pressure.

Tubular Reabsorption

The renal process whereby water and essential solutes are transported from the tubular fluid back into the peritubular capillary bloodstream.

Tubular Secretion

The renal process whereby waste products, hydrogen ions, and drugs are selectively transported from peritubular blood directly into the tubular lumen.

Micturition

The physiological process of emptying stored urine from the urinary bladder through the urethra to the outside of the body; also termed urination or voiding.