Key Concepts of Blood Composition and Function

3 main components of blood

Plasma, erythrocytes (RBCs), and the buffy coat (leukocytes and platelets)

Hematocrit

The percentage of total blood volume occupied by red blood cells

Normal hematocrit range for adult males

47 ± 5%

Normal hematocrit range for adult females

42 ± 5%

Plasma protein that retains water in blood vessels

Albumin

Cause of proteinemia

Deficiency in the liver

Kwashiorkor in children

Develop edema and ascites due to protein deficiency

Major intracellular protein in erythrocytes

Hemoglobin (Hb)

Molecules of Hb in each RBC

About 250 million

Hemoglobin binding oxygen and carbon dioxide

False

Hemoglobin binds oxygen best in its ___ form

Relaxed

Hemoglobin binds CO₂ best in its ___ form

Taut

Trigger for erythropoietin (EPO) release

Decreased oxygen delivery (hypoxia)

Location of erythropoiesis

Red bone marrow

Lifespan of an RBC

~120 days

Primary organ for RBC destruction

The spleen (and also the liver)

Anemia

A condition where oxygen-carrying capacity of the blood is reduced

Mutation causing sickle-cell anemia

Mutation in the β-globin chain of hemoglobin

Thalassemia

Involves a failure to produce functional α or β hemoglobin chains

Anemia in chronic kidney disease

Due to decreased EPO production

Diffusion limit of O₂ before hypoxia

~100 µm

Angiogenesis

The formation of new blood vessels from existing vasculature

Two circuits of the cardiovascular system

Pulmonary and systemic circulation

Arrangement of systemic circulation

Parallel; to allow independent flow control to each organ

Left ventricular failure result

Pulmonary edema

Poiseuille's Law formula

Flow ∝ (ΔP × r⁴) / (η × l)

Variable with largest effect on blood flow in Poiseuille's Law

Radius (r)

Rapid alteration of vessel radius

Via vascular smooth muscle contraction or relaxation

Effect of adding vessels in parallel on total resistance

Decreases total resistance

Compliance formula

ΔVolume / ΔPressure

More compliant: Veins or arteries?

Veins

Effect of age on compliance

It decreases

Laplace's Law

Wall stress = (P × r) / wall thickness

Aneurysms and rupture

Increased radius → increased wall stress

Velocity in capillaries vs arteries

Higher in arteries; total cross-sectional area is lower

Blood velocity in smaller vessels

False

Vascular resistance

Define vascular resistance.

Opposition to blood flow

Opposition to blood flow due to friction in the vessel

Factors that increase blood viscosity

Increased hematocrit and decreased velocity

Effect of increased hematocrit on flow

Increases viscosity, which decreases flow

Layers of a blood vessel wall

Endothelium → Tunica media → Adventitia

Nervous system innervating vascular smooth muscle

Sympathetic nervous system (SNS)

Pressure change from arteries to veins

It decreases

Skeletal muscle pump function

Helps overcome gravity-driven venous pooling

Capillaries ideal for exchange

Thin walls, slow flow, and high surface area

Conductance

The ease of flow, inverse of resistance (1/R)

Low flow velocity effects in small vessels

RBC 'stickiness' and increased viscosity

Function of fibrinogen and clotting factors

Facilitate coagulation and stop bleeding

Plasma protein group including antibodies

Globulins

Buffy coat composition

White blood cells and platelets

Cardiovascular system and body temperature

By redistributing heat via blood flow

Blood classification

True: Blood is classified as a connective tissue

Formation of new arteries

Arteriogenesis

Edematous fluid accumulation in Kwashiorkor

Low albumin → decreased oncotic pressure → fluid leaves vascular compartment → edema

RBCs lack of nuclei and mitochondria

To maximize volume for hemoglobin and ensure anaerobic metabolism so they don't consume transported O₂

Effect of polycythemia on blood flow

Increased RBC count → higher viscosity → increased resistance → reduced flow unless ΔP increases

Impact of stiff arteries on pressure

Decreased arterial compliance → systolic pressure rises, pulse pressure widens

Benefit of angiogenesis after leg injury

New capillaries improve perfusion and deliver nutrients/oxygen to healing tissue

Systemic circulation organization

Parallel keeps others unaffected, so an increase in one resistance doesn't change others' flows significantly

Gravity's effect on venous return when standing

Venous pooling in legs → skeletal muscle pump and venous valves → aid return; also ↑ sympathetic tone causing venoconstriction

Effects of anemia and low hematocrit on viscosity and flow

Low hematocrit → decreased viscosity → easier flow but fewer RBCs → reduced O₂ delivery; EPO may rise