Human Physiology: Cardiovascular System, Blood Vessels, Blood Pressure, and Blood Composition

Comprehensive vocabulary review flashcards covering blood vessel mechanics, hemodynamics, microcirculation, Starling forces, baroreceptor reflexes, hematology, leukocytes, and hemostasis.

Flow Rule

The physical principle governing fluid movement through the vasculature, stating that blood flow ($F$) equals the pressure gradient ($\Delta P$) divided by resistance ($R$): $F = \frac{\Delta P}{R}$.

Bulk Flow

The movement of fluid from a region of higher pressure to a region of lower pressure down a pressure gradient.

Mean Arterial Pressure (MAP)

The average pressure of blood contained within the systemic arteries across a complete cardiac cycle, with an average resting value of $85\,\text{mm\,Hg}$.

Central Venous Pressure (CVP)

The pressure of blood within the vena cava near its entrance to the right atrium, which normally approximates $0\,\text{mm\,Hg}$.

Systemic Pressure Gradient

The driving force pushing blood through the systemic circulation, calculated as $\Delta P = \text{MAP} - \text{CVP} = 85\,\text{mm\,Hg} - 0\,\text{mm\,Hg} = 85\,\text{mm\,Hg}$.

Pulmonary Pressure Gradient

The driving force moving blood through the lungs, calculated as $\Delta P = P_{\text{pulmonary arteries}} - P_{\text{pulmonary veins}} = 15\,\text{mm\,Hg} - 0\,\text{mm\,Hg} = 15\,\text{mm\,Hg}$.

Total Peripheral Resistance (TPR)

The combined resistance to blood flow offered by all blood vessels throughout the systemic circuit.

Microcirculation

The network of microscopic vessels consisting of arterioles, capillaries, and venules where tissue exchange and resistance regulation occur.

Elastic Arteries

Large-diameter conducting arteries whose walls are rich in elastin and fibrous tissue, functioning as low-compliance pressure reservoirs that maintain blood flow during diastole.

Muscular Arteries

Branching arterial vessels less than $0.1\,\text{mm}$ in diameter that contain abundant smooth muscle to regulate vessel radius and regional blood flow.

Vascular Compliance

The measure of a vessel wall's ability to stretch in response to a change in internal fluid pressure, defined by the formula $\frac{\Delta V}{\Delta P}$.

Systolic Blood Pressure (SBP)

The maximum pressure exerted inside the aorta and systemic arteries during ventricular contraction and blood ejection.

Diastolic Blood Pressure (DBP)

The minimum pressure remaining inside the aorta and systemic arteries during ventricular relaxation, prevented from dropping to zero by the elastic recoil of arterial walls.

Pulse Pressure (PP)

The difference between systolic pressure and diastolic pressure, calculated as $\text{PP} = \text{SP} - \text{DP}$.

Korotkoff Sounds

Audible turbulent rushing sounds detected through a stethoscope when auscultating an artery that is partially compressed by a blood pressure cuff.

Continuous Capillaries

The most common class of capillaries, characterized by uninterrupted endothelial cells joined by narrow intercellular gaps permeable to small water-soluble solutes but impermeable to proteins.

Fenestrated Capillaries

Specialized exchange vessels perforated with endothelial pores (fenestrations) and wide intercellular gaps, facilitating rapid fluid movement in the kidneys, intestines, and endocrine glands.

Sinusoidal (Discontinuous) Capillaries

Highly permeable blood vessels possessing large intercellular gaps and an incomplete basement membrane that allow proteins and whole blood cells to enter and exit in the liver, spleen, and bone marrow.

Metarterioles

Intermediate structural bypass vessels with discontinuous rings of smooth muscle that link arterioles directly to venules, shunting blood past capillary networks when constricted.

Precapillary Sphincters

Rings of vascular smooth muscle situated at the origin of capillaries branching off arterioles that constrict or dilate exclusively in response to local metabolic signals.

Vasomotion

The periodic, alternating contraction and relaxation of precapillary sphincters and metarteriolar smooth muscle mediated by local tissue metabolic factors.

Transcytosis

The active transcellular transport process involving endocytosis and exocytosis used to transport large exchangeable proteins across capillary endothelial cells.

Capillary Hydrostatic Pressure ($P_{\text{CAP}}$)

The fluid pressure exerted by blood against the internal capillary wall, which drives fluid outward into the interstitium (filtration) with values ranging from $38\,\text{mm\,Hg}$ at the arteriole end to $16\,\text{mm\,Hg}$ at the venule end.

Interstitial Fluid Hydrostatic Pressure ($P_{\text{IF}}$)

The hydrostatic pressure exerted by free fluid in the interstitial space against the external capillary wall, opposing filtration (favoring absorption) with a normal value of approximately $1\,\text{mm\,Hg}$.

Capillary Osmotic Pressure ($\pi_{\text{CAP}}$)

The colloid osmotic (oncotic) pressure exerted by nonpermeable plasma proteins trapped in the bloodstream, drawing fluid back into the capillary lumen (absorption) at approximately $25\,\text{mm\,Hg}$.

Interstitial Fluid Osmotic Pressure ($\pi_{\text{IF}}$)

The colloid osmotic pressure exerted by scarce interstitial proteins that acts to pull fluid out of the capillary into the tissue space (filtration), typically $0\,\text{mm\,Hg}$.

Net Filtration Pressure (NFP)

The overall driving pressure across a capillary wall, calculated as $\text{NFP} = (P_{\text{CAP}} + \pi_{\text{IF}}) - (\pi_{\text{CAP}} + P_{\text{IF}})$, yielding net filtration at the arteriole end and net absorption at the venule end.

Edema

The abnormal accumulation of fluid within the interstitial space resulting from an imbalance where capillary filtration exceeds fluid absorption and lymphatic drainage.

Arterial Baroreceptors

Specialized sensory stretch mechanoreceptors located within the carotid sinuses and the aortic arch that detect changes in blood pressure by altering their action potential firing rate.

Baroreceptor Reflex

A primary neural negative feedback mechanism centered in the brainstem that rapidly counteracts deviations in mean arterial pressure by adjusting autonomic output to the heart and systemic blood vessels.

Cardiovascular Control Center

A regulatory neural center situated in the medulla oblongata that integrates afferent inputs from baroreceptors, chemoreceptors, and proprioceptors to adjust cardiac output and vascular resistance.

Vasopressin

A posterior pituitary peptide hormone that raises mean arterial pressure during hypovolemia by promoting arteriolar vasoconstriction and increasing renal tubular water reabsorption.

Angiotensin II

A potent vasoconstrictor peptide that elevates mean arterial pressure by stimulating arteriolar smooth muscle contraction, triggering thirst, and stimulating adrenal aldosterone secretion.

Venomotor Tone

The state of contraction in the smooth muscle of veins, which when increased by sympathetic stimulation decreases venous compliance and raises venous return to the heart.

Respiratory Sinus Arrhythmia

A rhythmic alteration in resting heart rate synchronized with breathing, marked by an increased heart rate during inspiration (sympathetic dominance) and a decreased heart rate during expiration (parasympathetic dominance).

Hematocrit

The fraction of whole blood volume occupied by erythrocytes, determined following centrifugation and normally averaging $42\text{--}52\%$ in men and $37\text{--}47\%$ in women.

Buffy Coat

The thin intermediate layer formed upon centrifugation of whole blood containing leukocytes and platelets, comprising less than $1\%$ of total blood volume.

Albumin

The most abundant plasma protein, accounting for $60\%$ of all plasma proteins, synthesized in the liver and functioning as the primary determinant of plasma oncotic pressure.

Globulins

A group of plasma proteins representing $36\%$ of total blood proteins, functioning in lipid and hormone transport, blood clotting, and adaptive immune defense.

Fibrinogen

A soluble plasma protein synthesized by the liver that is enzymatically converted to insoluble fibrin during the final common pathway of blood clotting.

Serum

The liquid fraction of blood plasma that remains after whole blood has clotted and the clotting factors have been removed.

Hemoglobin

The primary oxygen-transporting protein in erythrocytes, composed of four globin polypeptide subunits (two $\alpha$ and two $\beta$ chains) and four iron-containing heme groups.

Carbonic Anhydrase

An enzyme present inside erythrocytes that catalyzes the reversible hydration reaction: $\text{CO}_2 + \text{H}_2\text{O} \rightleftharpoons \text{H}_2\text{CO}_3 \rightleftharpoons \text{H}^+ + \text{HCO}_3^-$.

Erythropoiesis

The process of red blood cell production occurring in red bone marrow, stimulated by erythropoietin (EPO) secreted by the kidneys under hypoxic conditions.

Transferrin

The circulating plasma transport protein that binds ferric iron ($\text{T-iron}$) to transport it from the digestive tract and liver to the bone marrow.

Ferritin

The intracellular iron-storage protein complex ($\text{F-iron}$) found predominantly in the liver, spleen, and small intestine.

Pernicious Anemia

A megaloblastic anemia characterized by defective erythrocyte proliferation and macrocytic cells caused by a deficiency in intrinsic factor required for vitamin $\text{B}_{12}$ absorption.

Sickle Cell Anemia

A genetic hemolytic anemia caused by abnormal hemoglobin polymerization that deforms erythrocytes into rigid, sickle-shaped cells prone to rupture and vascular occlusion.

Neutrophil

The most abundant type of circulating white blood cell ($50\text{--}80\%$), distinguished by a multilobed nucleus and granules that phagocytoses foreign bacteria and debris.

Eosinophil

A granular leukocyte ($1\text{--}4\%$ of leukocytes) with a bilobed nucleus and bright red-staining granules containing cytotoxic enzymes designed to kill parasitic invaders.

Basophil

A circulating granulocyte ($<1\%$ of leukocytes) containing dark blue-staining granules filled with histamine and heparin that mediate inflammatory and allergic responses.

Monocyte

An agranulocyte ($5\%$ of leukocytes) with a large kidney-shaped nucleus that migrates from the bloodstream into peripheral tissues to differentiate into a phagocytic macrophage.

Lymphocyte

An agranular leukocyte with a round nucleus and scant cytoplasm comprising $30\%$ of leukocytes, functioning in acquired and targeted immunity (B cells, T cells, and natural killer cells).

Hemostasis

The physiological mechanism that arrests bleeding from an injured blood vessel, consisting of vascular spasm, platelet plug formation, and blood coagulation.

von Willebrand Factor (vWf)

A plasma protein that binds to exposed subendothelial collagen fibers at the site of vascular injury, anchoring platelets to initiate platelet plug formation.

Thromboxane A2 (TXA2)

An eicosanoid synthesized and released by activated platelets that promotes further platelet aggregation and vasoconstriction through positive feedback.

Prostacyclin (PGI2)

An eicosanoid produced by healthy endothelial cells that prevents platelet aggregation and maintains patency in uninjured vascular segments.

Factor Xa

The activated enzymatic coagulation factor at the intersection of the intrinsic and extrinsic pathways that, with factor V, $\text{Ca}^{2+}$, and PF3, converts prothrombin to thrombin.

Tissue Plasminogen Activator (tPA)

A fibrinolytic enzyme secreted by endothelial cells that converts inactive plasminogen to active plasmin to enzymatically degrade and dissolve fibrin clots.

Hemophilia

A genetic bleeding disorder caused by an inherited deficiency of a specific clotting factor, most commonly coagulation factor VIII.