Blood Composition & Cardiovascular Physiology

Vocabulary flashcards covering chapters 17, 18, and 19 on blood composition, heart anatomy, cardiac dynamics, vascular resistance, and capillary fluid dynamics.

Vasodilation

An increase in blood vessel diameter that causes total peripheral vascular resistance ($PR$) to decrease according to $R \propto \frac{1}{r^4}$.

Blood Viscosity

The stickiness or internal friction of blood, elevated in conditions such as polycythemia, which causes resistance to blood flow to increase.

Erythropoietin (EPO)

A hormone secreted by the kidneys in response to renal tissue hypoxia that stimulates red bone marrow to increase red blood cell production and hematocrit.

Frank-Starling Law of the Heart

The principle that increasing end-diastolic volume ($EDV$) stretches ventricular cardiac muscle fibers (preload), thereby increasing myocardial contraction force and stroke volume ($SV$).

End-Systolic Volume (ESV)

The volume of blood remaining in a ventricle at the end of contraction (systole), which increases when facing elevated arterial blood pressure (afterload).

Blood Colloid Osmotic Pressure (OPc)

The inward osmotic force generated primarily by non-diffusible plasma proteins (chiefly albumin) that pulls fluid into capillaries from the interstitial space.

Angiotensin II

A potent systemic vasoconstrictor released in response to low renal blood pressure that increases systemic arteriolar constriction and raises blood pressure.

Atrial Natriuretic Peptide (ANP)

A hormone secreted by atrial cardiac cells that causes kidney excretion of sodium ($Na^+$) and water, reducing blood volume and blood pressure.

Hypercapnia

An elevation in arterial $CO_2$ levels detected by central and peripheral chemoreceptors that stimulates an increase in cardiac output ($CO$).

Skeletal Muscle Pump

The rhythmic contraction of skeletal muscles (such as calf muscles) that compresses deep veins, driving venous return toward the heart.

Bilirubin

A waste pigment produced by macrophages in the spleen during the breakdown of heme from destroyed or fragile red blood cells.

Reticulocyte

A young erythrocyte whose elevated count in circulating blood indicates an increased rate of red blood cell production in red bone marrow.

Vascular Spasm

The immediate constriction of vascular smooth muscle following blood vessel injury, acting as the first phase of hemostasis to reduce blood loss.

Albumin

The most abundant plasma protein produced by the liver, accounting for roughly $60\%$ of plasma protein, which acts as the primary contributor to blood colloid osmotic pressure.

Erythrocyte

An anucleate red blood cell with an average lifespan of $120\,days$, comprising the densest bottom layer ($\sim 45\%$) of centrifuged blood.

Hemoglobin (HbA)

The adult respiratory pigment consisting of $2\,\text{alpha}$ and $2\,\text{beta}$ globin chains, each bound to an iron-containing heme group that transports oxygen.

Neutrophil

The most abundant granular leukocyte ($50\%-70\%$ of white blood cells) that acts as a primary phagocyte during acute bacterial infections.

Eosinophil

A granular leukocyte featuring a bilobed nucleus and red-staining cytoplasmic granules, specialized for digesting parasitic worms and modulating allergic reactions.

Megakaryocyte

A large, multinucleated cell located in red bone marrow that pinches off cellular fragments to form platelets.

Hemostasis

The three-step process that stops bleeding following blood vessel injury, progressing sequentially through vascular spasm, platelet plug formation, and coagulation.

Tissue Factor (TF / Factor III)

A clotting factor released by damaged extravascular tissues that rapidly initiates the extrinsic coagulation pathway.

Fibrinogen

A soluble plasma protein converted by thrombin into an insoluble fibrin mesh during Phase 3 of blood coagulation.

Type O Negative Blood

A blood type characterized by red blood cells lacking both A and B agglutinogens (antigens) and plasma containing both anti-A and anti-B antibodies (agglutinins).

Epicardium

The outermost layer of the heart wall, which is structurally synonymous with the visceral layer of the serous pericardium.

Chordae Tendineae and Papillary Muscles

Structures within the ventricles that tighten during ventricular systole to prevent the atrioventricular (AV) valve cusps from everting into the atria.

Intrinsic Cardiac Conduction System

The electrical pathway controlling heart contraction, following the sequence: SA node $\rightarrow$ AV node $\rightarrow$ AV bundle (Bundle of His) $\rightarrow$ Right and Left Bundle Branches $\rightarrow$ Subendocardial conducting network (Purkinje fibers).

Atrioventricular (AV) Node Delay

A physiological delay of roughly $0.1\,seconds$ in electrical transmission that allows the atria to complete contraction and fill the ventricles before ventricular systole begins.

QRS Complex

The deflection wave on a standard electrocardiogram (ECG) tracing that represents rapid ventricular depolarization.

Stroke Volume (SV)

The volume of blood pumped out by a ventricle with each beat, mathematically defined by the equation $\text{SV} = \text{EDV} - \text{ESV}$.

First Heart Sound (S1 / 'lub')

The audible heart sound produced by the closure of the atrioventricular (AV) valves at the onset of ventricular systole.

Tunics of Systemic Blood Vessels

The three concentric tissue layers forming blood vessel walls, arranged from innermost to outermost as: Tunica intima, Tunica media, and Tunica externa.

Arterioles

Small blood vessels possessing the largest proportion of smooth muscle relative to diameter, functioning as the primary determinant of peripheral vascular resistance.

Poiseuille's Law

A physiological principle stating that vascular resistance ($R$) is inversely proportional to the fourth power of the blood vessel radius ($r$), represented as $R \propto \frac{1}{r^4}$.

Mean Arterial Pressure (MAP)

The calculated average pressure driving blood through systemic arteries, determined by the formula $\text{MAP} = \text{Diastolic BP} + \frac{1}{3}(\text{Pulse Pressure})$.

Capillary Hydrostatic Pressure (HPc)

The outward force generated by blood pressure within capillaries that pushes fluid out across endothelial walls into the interstitial space (filtration).

Hypovolemic Shock

A form of circulatory shock caused by acute, severe blood or plasma loss (e.g., hemorrhage, severe vomiting, or diarrhea), leading to reduced venous return and cardiac output.