Anatomy and Physiology II: Blood, Heart, and Blood Vessels

Comprehensive practice flashcards reviewing blood components, heart anatomy and physiology, cardiac cycle, and vascular dynamics for Exam 1.

What are the relative volume percentages of plasma and formed elements in centrifuged whole blood?

Whole blood separates into plasma, which makes up approximately $55\%$ of total blood volume, and formed elements, which make up approximately $45\%$ (consisting of red blood cells and a buffy coat containing leukocytes and platelets).

What are the three primary functional categories of blood?

1. Transport (delivering oxygen, nutrients, hormones, and metabolic wastes). 2. Regulation (maintaining body temperature, normal pH, and fluid volume). 3. Protection (preventing blood loss via clotting and preventing infection via antibodies, complement proteins, and white blood cells).

What are the major plasma proteins and their respective contributions to total plasma protein weight?

Plasma proteins constitute $8\%$ of plasma weight: Albumin ($60\%$ of plasma proteins, main contributor to osmotic pressure), Globulins ($36\%$, transport proteins and antibodies), and Fibrinogen ($4\%$, forms fibrin threads of blood clot).

What is the structural composition of a hemoglobin molecule?

Hemoglobin consists of globin (four polypeptide chains: two alpha and two beta chains) and four non-protein heme groups, each containing an iron ion ($Fe^{2+}$) capable of binding one oxygen molecule.

From which stem cell do all formed elements of blood originate?

All formed elements arise from pluripotent hematopoietic stem cells (hemocytoblasts) located in red bone marrow.

What hormone controls erythropoiesis, and what stimulus triggers its secretion?

Erythropoietin (EPO), produced mainly by the kidneys (and liver to a smaller extent), controls erythropoiesis. Its secretion is stimulated by hypoxia (low blood oxygen levels).

What are the normal hematocrit values for adult males and females?

For males, normal hematocrit is $40\text{--}54\%$ (average $47\%$); for females, it is $38\text{--}46\%$ (average $42\%$).

What are reticulocytes, and what does a reticulocyte count indicate?

Reticulocytes are immature erythrocytes that constitute $1\text{--}2\%$ of all erythrocytes. The reticulocyte count indicates bone marrow activity and its response to EPO or stem cell health.

What is the specific genetic mutation that causes sickle-cell anemia?

A single amino acid substitution at position 6 in the beta globin chain of hemoglobin (146 amino acids total), forming mutated Hemoglobin S (HbS).

What is the normal lifespan of an erythrocyte, and how are its components recycled?

Erythrocytes function for $100\text{--}120\,\text{days}$. Macrophages in the spleen, liver, and bone marrow breakdown old RBCs: globin is broken down into amino acids; iron ($Fe^{2+}$) from heme is stored/recycled via transferrin; non-iron heme is converted to bilirubin, secreted into bile by the liver, and metabolized to stercobilin in the intestines.

What are the relative percentages of the five white blood cell types in a normal differential WBC count?

Neutrophils: $50\text{--}70\%$; Lymphocytes: $25\text{--}45\%$; Monocytes: $3\text{--}8\%$; Eosinophils: $2\text{--}4\%$; Basophils: $0.5\text{--}1\%$.

What are the anatomical and functional characteristics of neutrophils?

Neutrophils are granular leukocytes ($10\text{--}12\,\mu m$ diameter) with multilobed nuclei ($2\text{--}6$ lobes). They respond first to bacterial infection via chemotaxis, phagocytizing pathogens and releasing lysozyme, strong oxidants, and defensins.

What are the structural features and main functions of eosinophils and basophils?

Eosinophils have bilobed nuclei and red/orange granules; they kill parasitic worms and modulate allergic reactions/asthma. Basophils have bilobed/irregular nuclei and large purplish-black granules; they release histamine, heparin, and serotonin to mediate inflammation and allergic responses.

What are the characteristics and functions of lymphocytes and monocytes?

Lymphocytes have spherical/indented nuclei with pale blue cytoplasm; T cells target virus-infected/tumor cells and B cells produce antibodies. Monocytes have U- or kidney-shaped nuclei and foamy cytoplasm; they differentiate into wandering macrophages to phagocytize microbes and debris.

What are platelets, and how are they produced?

Platelets (thrombocytes) are anucleate, disc-shaped cytoplasmic fragments ($2\text{--}4\,\mu m$ diameter) shed from giant megakaryocytes in red bone marrow; they function in blood clotting with a lifespan of $5\text{--}10\,\text{days}$.

What are the three steps of hemostasis?

1. Vascular spasm (smooth muscle constriction). 2. Platelet plug formation (platelets adhere to exposed collagen and release aggregating chemicals). 3. Coagulation (blood clotting resulting in a fibrin mesh).

How do the intrinsic and extrinsic pathways of coagulation differ in Phase 1?

The intrinsic pathway is slower, triggered by negatively charged surfaces (such as collagen or glass), and all clotting factors are present in blood. The extrinsic pathway is faster, triggered by Tissue Factor (TF / Factor III) exposed outside blood, and bypasses several steps.

What components make up the prothrombin activator complex?

Prothrombin activator consists of activated Factor $X_a$, Factor $V_a$, Calcium ions ($Ca^{2+}$), and a phospholipid surface.

What events occur in Phase 2 and Phase 3 of blood coagulation?

Phase 2: Prothrombin activator catalyzes the conversion of prothrombin to active thrombin. Phase 3: Active thrombin with $Ca^{2+}$ converts soluble fibrinogen into insoluble fibrin strands, which Factor $XIII_a$ cross-links into a fibrin mesh.

What enzyme dissolves blood clots during fibrinolysis, and how is it activated?

Plasmin dissolves blood clots by digesting fibrin. It is formed from plasminogen, which is activated by tissue plasminogen activator (tPA), activated Factor XII, or thrombin.

What are the structural layers of the pericardium?

The fibrous pericardium is the tough, inelastic outer connective tissue sac attached to the diaphragm. The serous pericardium consists of an outer parietal layer (lining fibrous pericardium) and an inner visceral layer (epicardium, adhering to myocardium), separated by the serous fluid-filled pericardial cavity.

What are the three distinct layers of the heart wall?

1. Epicardium (visceral layer of serous pericardium, outer smooth thin layer). 2. Myocardium (middle layer composed of cardiac muscle). 3. Endocardium (innermost endothelium and connective tissue lining chambers and valves).

What specialized cell junctions are found within the intercalated discs of cardiac muscle?

Gap junctions, which allow action potentials to pass directly from fiber to fiber, and desmosomes, which anchor cells together to prevent separation during contraction.

What is the complete pathway of blood flow through the heart and lungs?

Venae cavae / Coronary sinus -> Right Atrium -> Tricuspid Valve -> Right Ventricle -> Pulmonary Semilunar Valve -> Pulmonary Trunk / Arteries -> Lungs -> Pulmonary Veins -> Left Atrium -> Bicuspid (Mitral) Valve -> Left Ventricle -> Aortic Semilunar Valve -> Aorta -> Systemic circulation.

How do papillary muscles and chordae tendineae prevent AV valve backflow?

Chordae tendineae anchor AV valve cusps to papillary muscles. When ventricles contract, papillary muscles also contract, pulling chordae tendineae taut to prevent valve cusps from opening backward into the atria.

What are the components and impulse pathway of the intrinsic cardiac conduction system?

Sinoatrial (SA) node -> Atrioventricular (AV) node -> Atrioventricular (AV) bundle (Bundle of His) -> Right and Left bundle branches -> Purkinje fibers.

What ionic events cause the action potential phases in cardiac pacemaker cells?

1. Pacemaker potential: slow depolarization due to opening of slow $Na^+$ channels and closing of $K^+$ channels. 2. Depolarization: influx of $Ca^{2+}$ through voltage-gated $Ca^{2+}$ channels at threshold ($-40\,mV$). 3. Repolarization: $Ca^{2+}$ channels inactivate and voltage-gated $K^+$ channels open, causing $K^+$ efflux.

What cardiac electrical events are represented by the P wave, QRS complex, and T wave on an ECG?

P wave: atrial depolarization. QRS complex: ventricular depolarization (masks atrial repolarization). T wave: ventricular repolarization.

What is the formula for Cardiac Output (CO), and what is a typical resting value?

$CO = HR \times SV$. For a heart rate of $70\,\text{beats/min}$ and stroke volume of $70\,mL/\text{beat}$, $CO = 4900\,mL/\text{min} = 4.9\,L/\text{min}$.

What three main factors regulate stroke volume (SV)?

1. Preload (degree of stretch of cardiac muscle before contraction; Frank-Starling law). 2. Contractility (contractile strength at a given muscle length). 3. Afterload (arterial pressure that ventricles must overcome to eject blood).

What are the three tunics of a typical blood vessel wall?

1. Tunica intima / interna (innermost endothelium, subendothelial layer, internal elastic membrane). 2. Tunica media (middle layer of smooth muscle and elastic fibers). 3. Tunica externa / adventitia (outer collagen fiber layer with vasa vasorum).

What is the Windkessel effect in elastic arteries?

The expansion of large elastic arteries (like the aorta) during ventricular systole to absorb kinetic energy and pressure, followed by elastic recoil during diastole to maintain continuous blood flow.

How do continuous, fenestrated, and sinusoid capillaries differ structurally?

Continuous capillaries have tight junctions and narrow intercellular clefts. Fenestrated capillaries have endothelial pores ('fenestrations') for high fluid permeability (e.g., kidneys). Sinusoid capillaries have large intercellular gaps, incomplete basement membranes, and wide irregular lumens allowing whole cells to pass (e.g., liver, bone marrow).

Why are systemic veins designated as capacitance vessels or blood reservoirs?

Veins have thin walls and high compliance, enabling them to hold about $60\%$ of total blood volume at rest.

How does changing vessel radius affect vascular resistance?

Vascular resistance ($R$) is inversely proportional to the fourth power of vessel radius ($R \propto \frac{1}{r^4}$). Halving vessel radius increases resistance by $16\times$.

What are the mathematical formulas for Pulse Pressure and Mean Arterial Pressure (MAP)?

Pulse Pressure = $\text{Systolic Pressure} - \text{Diastolic Pressure}$. Mean Arterial Pressure (MAP) = $\text{Diastolic Pressure} + \frac{\text{Pulse Pressure}}{3}$.

How is Net Filtration Pressure (NFP) calculated at the arteriolar end of a capillary?

At the arteriolar end, $HP_c = 35\,mm\,Hg$, $OP_c = 26\,mm\,Hg$, $HP_{if} = 0\,mm\,Hg$, and $OP_{if} = 1\,mm\,Hg$. $NFP = (HP_c + OP_{if}) - (HP_{if} + OP_c) = (35 + 1) - (0 + 26) = +10\,mm\,Hg$, driving fluid out into interstitial space (net filtration).

How is Net Filtration Pressure (NFP) calculated at the venous end of a capillary?

At the venous end, $HP_c = 17\,mm\,Hg$, $OP_c = 26\,mm\,Hg$, $HP_{if} = 0\,mm\,Hg$, and $OP_{if} = 1\,mm\,Hg$. $NFP = (HP_c + OP_{if}) - (HP_{if} + OP_c) = (17 + 1) - (0 + 26) = -8\,mm\,Hg$, pulling fluid back into the capillary (net reabsorption).

Which hormone acts to decrease blood pressure, and by what mechanism?

Atrial Natriuretic Peptide (ANP), released by heart atria, decreases blood pressure by promoting renal excretion of salt and water (reducing blood volume) and promoting vasodilation.

How does the baroreceptor reflex respond to an increase in blood pressure above normal range?

High BP stimulates baroreceptors in carotid sinuses and aortic arch, which signal the medulla to inhibit the cardioacceleratory and vasomotor centers and stimulate the cardioinhibitory center, causing decreased heart rate, decreased contractility, and vasodilation to lower BP.

What is the structural pathway of blood flow in the Hepatic Portal System?

Digestive organ capillary beds -> Hepatic portal vein -> Liver sinusoids (capillary bed) -> Hepatic vein -> Inferior vena cava.

What are the three main types of circulatory shock?

1. Hypovolemic Shock (acute blood or fluid loss). 2. Vascular Shock (extreme vasodilation / loss of vasomotor tone from anaphylaxis or sepsis). 3. Cardiogenic Shock (heart failure resulting in failure to maintain CO).

How does oxygen availability affect blood vessel diameter in pulmonary vs systemic circulation?

In pulmonary vessels, high $O_2$ causes vasodilation and low $O_2$ causes vasoconstriction. In systemic vessels (such as skeletal muscle), low $O_2$ causes vasodilation and high $O_2$ causes vasoconstriction.

What physical events cause the first ($S_1$) and second ($S_2$) heart sounds?

The first sound ($S_1$, 'lub') is caused by closure of the atrioventricular (AV) valves at the onset of ventricular systole. The second sound ($S_2$, 'dub') is caused by closure of the semilunar (SL) valves at the onset of ventricular diastole.