Blood and Cardiovascular System: Study Guide for Anatomy & Physiology

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Blood: Composition and Function

Components of Blood

Blood is a specialized connective tissue composed of plasma and formed elements. It plays a vital role in transport, regulation, and protection within the body.

Plasma: The liquid matrix, making up about 55% of blood volume.
Formed Elements: Includes red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

Type of Tissue

Blood is classified as a connective tissue due to its origin from mesenchyme and the presence of a non-living matrix (plasma).

Cell Types

Erythrocytes (RBCs): Transport oxygen and carbon dioxide.
Leukocytes (WBCs): Defend against pathogens.
Platelets: Involved in blood clotting.

Definition of Hematocrit

Hematocrit: The percentage of blood volume occupied by red blood cells. Normal values: males ~47%, females ~42%.

pH and Approximate Volume in Humans

pH: Blood is slightly alkaline, with a normal pH range of 7.35–7.45.
Volume: Average adult blood volume is 5–6 liters in males, 4–5 liters in females.

Plasma

Major Components: Water (90%), plasma proteins (albumin, globulins, fibrinogen), nutrients, electrolytes, gases, hormones, and waste products.
Significance of Plasma Proteins & Albumin: Albumin maintains osmotic pressure and transports substances; globulins function in immunity; fibrinogen is essential for clotting.

Origin of White Blood Cells (WBCs)

WBCs originate from hematopoietic stem cells in the red bone marrow.

Red Blood Cells (RBCs): Shape & Size

Shape: Biconcave discs, increasing surface area for gas exchange.
Size: Approximately 7–8 μm in diameter.
Other Characteristics: Lack nuclei and most organelles; filled with hemoglobin.

Blood Viscosity

RBCs are the major contributors to blood viscosity, affecting flow and resistance.

Function of Erythrocytes

Transport oxygen from lungs to tissues and carbon dioxide from tissues to lungs.

Hemoglobin

A protein in RBCs that binds oxygen; each molecule can carry four oxygen molecules.
Normal values: males 13–18 g/dL, females 12–16 g/dL.

Hematopoiesis

The process of blood cell formation, occurring primarily in the red bone marrow.
Location: In adults, mainly in the axial skeleton, pelvic girdle, and proximal epiphyses of humerus and femur.

Stem Cells

All blood cells derive from hematopoietic stem cells (hemocytoblasts).

Erythropoiesis

The production of erythrocytes, regulated by erythropoietin (EPO).
Location: Red bone marrow.
When Released: EPO is released by the kidneys in response to hypoxia (low oxygen levels).

Balance Between RBC Production & Destruction

Maintained by hormonal controls (EPO) and adequate dietary nutrients (iron, vitamin B12, folic acid).
Too few RBCs leads to hypoxia; too many increases blood viscosity.

Testosterone & EPO

Testosterone enhances EPO production, contributing to higher RBC counts in males.

Dietary Requirements for Erythropoiesis

Iron, vitamin B12, and folic acid are essential for RBC production.

Life Span of RBC

Approximately 120 days; old RBCs are removed by macrophages in the spleen and liver.

Increased RBC Destruction

Can result from hemolytic anemia, autoimmune disorders, or mechanical damage.

Anemia

Definition: A condition in which the blood's oxygen-carrying capacity is too low.
Signs: Fatigue, pallor, shortness of breath.
Symptoms: Weakness, dizziness, rapid heartbeat.
Causes (3 categories): Blood loss, decreased RBC production, increased RBC destruction.

Types of Anemia

Hemorrhagic Anemia: Due to blood loss.
Iron Deficiency Anemia: Microcytic, hypochromic RBCs; seen in blood smear.
Pernicious Anemia: Due to vitamin B12 deficiency; large, pale RBCs.
Renal Anemia: Caused by lack of EPO in chronic kidney disease.
Aplastic Anemia: Failure of bone marrow to produce RBCs.
Hemolytic Anemia: Premature destruction of RBCs.

Leukocytes (WBCs)

Make up ~1% of blood volume.
Types: Granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).
Infection Response: Neutrophils increase in bacterial infections; eosinophils in parasitic infections; basophils in allergies.
Leukopoiesis: Production of WBCs in bone marrow.
Leukopenia: Abnormally low WBC count.
Leukemia: Cancer of WBCs, leading to overproduction of abnormal cells.

Platelets

Cell fragments essential for blood clotting (hemostasis).

Blood Groups

Classified by presence of antigens (A, B, AB, O) and Rh factor on RBC membranes.

Cardiovascular System: Heart Structure and Function

Structure of the Heart

Four-chambered organ: two atria (upper chambers) and two ventricles (lower chambers).

Chambers

Right Atrium: Receives deoxygenated blood from the body.
Right Ventricle: Pumps blood to the lungs.
Left Atrium: Receives oxygenated blood from the lungs.
Left Ventricle: Pumps blood to the body.

Vessels

Major vessels include the aorta, pulmonary arteries and veins, superior and inferior vena cava.

Pericardium

Fibrous Pericardium: Outermost, tough connective tissue layer.
Parietal Pericardium: Lines the internal surface of the fibrous pericardium.
Visceral Pericardium (Epicardium): Covers the heart surface.
Pericarditis: Inflammation of the pericardium.

Heart Wall Layers

Epicardium: Outer layer (visceral pericardium).
Myocardium: Middle, muscular layer responsible for contraction.
Endocardium: Inner endothelial lining.

Septum and Valves

Interatrial Septum: Separates the atria; contains the fossa ovalis (remnant of fetal foramen ovale).
Interventricular Septum: Separates the ventricles.
Valves: Ensure unidirectional blood flow.
Atrioventricular (AV) Valves: Tricuspid (right), bicuspid/mitral (left); prevent backflow into atria.
Semilunar Valves: Pulmonary (right), aortic (left); prevent backflow into ventricles.
Chordae Tendineae: Tendinous cords anchoring AV valves to papillary muscles.
Papillary Muscles: Contract to prevent valve prolapse.

Table: Heart Valves

Valve	Location	Purpose
Tricuspid (AV)	Between right atrium & ventricle	Prevents backflow to right atrium
Bicuspid/Mitral (AV)	Between left atrium & ventricle	Prevents backflow to left atrium
Pulmonary (Semilunar)	Between right ventricle & pulmonary artery	Prevents backflow to right ventricle
Aortic (Semilunar)	Between left ventricle & aorta	Prevents backflow to left ventricle

Homeostatic Imbalances: Valve stenosis (narrowing), incompetence (leakage).

Cardiac Physiology

Circulation Pathways

Systemic Circulation: Delivers oxygenated blood to tissues, returns deoxygenated blood to heart.
Pulmonary Circulation: Carries deoxygenated blood to lungs for oxygenation.

Cardiac Muscle

Automaticity: Cardiac muscle cells can depolarize and contract without neural input.
Similarities/Differences with Skeletal Muscle: Both striated; cardiac muscle is branched, has intercalated discs, and is involuntary.
Anaerobic/Aerobic Respiration: Cardiac muscle relies primarily on aerobic metabolism for ATP.

Intrinsic Conduction Pathway

Coordinates heart contraction via specialized pacemaker cells.
Locations: SA node (right atrium), AV node, AV bundle, bundle branches, Purkinje fibers.
Features of Steps: SA node initiates impulse → AV node → AV bundle → bundle branches → Purkinje fibers.

Arrhythmias

Abnormal heart rhythms; can be tachycardia (fast) or bradycardia (slow).

Extrinsic Innervation

Autonomic nervous system (ANS) modulates heart rate and force.

Cardiac Cycle

Sequence of events in one heartbeat: atrial systole, ventricular systole, diastole.
Systole: Contraction phase.
Diastole: Relaxation phase.
S1 & S2: Heart sounds due to valve closure (S1: AV valves, S2: semilunar valves).

Venous Return & Contractile Force

Increased venous return stretches cardiac muscle, increasing contractile force (Frank-Starling law).
Excessive stretch can impair contraction and lead to heart failure.

Cardiac Output

Volume of blood pumped by each ventricle per minute.
Formula:

Congestive Heart Failure (CHF)

Definition: The heart's inability to pump sufficient blood to meet the body's needs.
Contributing Factors: Coronary artery disease, hypertension, myocardial infarction, valve disorders.

Right vs. Left Heart Failure

Right-sided failure: Causes peripheral edema.
Left-sided failure: Causes pulmonary congestion/edema.

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