Blood Composition and Functions

• Average total blood volume in an adult is about 5 to 6 liters.
• Formed elements constitute roughly 45% of the total blood volume.
• Plasma comprises about 55% of the total blood volume.

Formed Elements

• Red blood cells (RBCs) are a type of formed element.
• White blood cells (WBCs) are a type of formed element, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
• Platelets are a type of formed element.

Plasma Composition

• Plasma is about 91% water.
• Plasma is 7% proteins, including albumins, globulins, and fibrinogen.
• Elevated albumin levels may indicate dehydration.
• Globulins are larger and less soluble than albumin.
• Fibrinogen converts to fibrin during coagulation.

Blood Functions

• Transports oxygen to tissues and carbon dioxide to the lungs.
• Transports nutrients and waste products.
• Transports processed molecules.
• Transports regulatory hormones and enzymes.
• Regulates pH and osmosis.
• Maintains body temperature.
• Protects against foreign substances.
• Forms blood clots.

RBCs (Erythrocytes)

• Primary function involves transporting oxygen from the lungs to tissues.
• Primary function involves transporting carbon dioxide from tissue cells to the lungs.
• Normal range is 4–6 million/mm3.
• Produced in the bone marrow.
• Polycythemia is a high RBC count often seen in COPD patients due to chronic hypoxemia.
• Anemia is a low RBC count, potentially caused by blood loss, autoimmune diseases, or menstrual cycles.

Hematocrit

• Measures the percentage of RBCs in the blood volume after centrifugation.
• Normal range is 40–50%.
• Low hematocrit indicates anemia.
• High hematocrit indicates polycythemia.

Hemoglobin

• Transports oxygen from lungs to tissue cells.
• Transports carbon dioxide from tissue cells to the lungs.
• Carries 1.34 ml of oxygen per gram.
• Normal range is 12–16 g/100mL blood (g/dL).

Anemia

• Anemia is a deficiency of hemoglobin (Hb) in the blood.
• Nutritional deficiency (iron deficiency anemia) can lead to anemia.
• Hemorrhagic anemia results from trauma, ulcers, or excessive menstrual bleeding.
• Folate deficiency, common in pregnant women and alcoholics, can cause anemia.
• Pernicious anemia involves inadequate vitamin B12 intake, affecting folate synthesis.
• Hemolytic anemia involves excessive red blood cell rupture, due to drugs, snake venom, artificial heart valves, autoimmune disease, or hemolytic disease of the newborn.
• Aplastic anemia is caused by the bone marrow's inability to produce cells.
• Sickle-cell anemia causes cells to become rigid, blocking small blood vessels.

WBCs (Leukocytes)

• Protect the body against invading microorganisms.
• Classified as granulocytes or agranulocytes.
• Normal range is 5,000–10,000/mm3.
• Leukocytosis is an increased WBC count.
• Leukopenia is a decreased WBC count.

Granulocytes

• Neutrophils: 60% of WBCs; increased with bacterial infections, decreased with viral infections.
• Eosinophils: 2% of WBCs; increased in allergic reactions (asthma), produce yellow sputum.
• Basophils: 1% of WBCs; increased with allergies.

Agranulocytes

• Lymphocytes: 30% of WBCs; decreased with sepsis, SLE; increased in allergic reactions and autoimmune diseases.
• Monocytes: 3% of WBCs; associated with TB.

Neutrophils

• Under normal conditions, average about 60% of the total WBC count.
• Very mobile, active phagocytic cells.
• Cytoplasmic granules contain powerful lysosomes.

Eosinophils

• Normally, make up about 2% of circulating WBCs.
• Numerous in tissue lining respiratory and digestive tracts.
• Destroy protozoa and parasitic worms, release anti-inflammatory substances in antigen–antibody reactions.
• Elevated counts are commonly seen in asthmatic patients.

Basophils

• Account for 1% of total count.
• Cytoplasmic granules contain histamine and heparin.
• Histamine is an inflammatory substance causing vasodilation.
• Heparin inhibits blood clotting.
• Basophils increase in number in both allergic and inflammatory reactions.

Lymphocytes

• Second most numerous leukocytes in blood.
• Account for 30% of total WBC count.
• Most found in lymphoid tissues (lymph nodes).
• Play several important roles in immunity.

Monocytes

• Account for 3%.
• In tissue, differentiate into highly mobile macrophages.
• Phagocytize bacteria, dead cells, cell fragments, and viral-infected cells.
• Increase in number is associated with chronic infections (TB).

Platelets

• Also known as thrombocytes.
• Smallest of the formed elements in plasma.
• Normal count ranges from 150,000 to 400,000/mm3 of blood.
• Play an important role in preventing blood loss from traumatized areas.
• Form platelet plugs that seal holes in small blood vessels.

Anatomy of the Heart

• The heart wall has three layers: epicardium (outer), myocardium (middle), and endocardium (inner).
• The myocardium comprises the bulk of the heart and is composed of muscle tissue.
• The endocardium forms a thin continuous tissue with blood vessels.
• The heart has four chambers: right and left atria (upper) and right and left ventricles (lower).
• Ventricles move blood forward.

Relationship of Heart to Other Body Parts

• The heart's relation to the sternum, ribs, and diaphragm.
• The heart's relation to the thorax.
• The heart's relation to the lungs, great vessels.

Pericardium

• The pericardium is a double-walled sac enclosing the heart.
• The fibrous pericardium is a tough, loose-fitting, and inelastic sac surrounding the heart.
• The serous pericardium consists of two layers: parietal (lining the fibrous pericardium) and visceral (covering the heart and great vessels).
• Pericarditis is inflammation of the pericardium.

Pericardial Fluid

• A thin layer of fluid separating the parietal and visceral pericardium.
• Helps minimize friction during contraction and expansion.

Atrioventricular Valves (AV Valves)

• Tricuspid and Mitral (Bicuspid)
• Lie between atria and ventricles.
• The tricuspid valve is at the right atrium exit.
• The mitral valve is at the left atrium exit.
• Ventricular contraction forces valves closed, preventing backflow of blood into the atria.
• Lower ends of valves anchor to ventricular papillary muscles by chordae tendineae.
• Papillary contraction during systole pulls on chordae, preventing valve reversing into atria.
• Pericardial effusion: abnormal amount of accumulated fluid between layers.

Semilunar Valves

• Consist of three half-moon–shaped cusps.
• Separate ventricles from their arterial outflow tracts, pulmonary artery and aorta.
• Situated at ventricle exits to outflow tracks (arterial trunks).
• The pulmonary valve lies between the right ventricle and the pulmonary artery.
• The aortic valve lies between the left ventricle and the aorta.
• During Systole (cardiac contraction): valves open, allowing ventricular ejection into arteries (pulmonary artery and aorta).
• During Diastole: valves close, preventing back flow of blood into ventricles.
• Regurgitation: backflow of blood through an incompetent or damaged valve.
• Stenosis: pathologic narrowing or constriction of a valve outlet, causing increased pressure in the proximal chamber and vessels.
• Mitral Stenosis: narrowing of the mitral valve.

Coronary Circulation

• Two main coronary arteries arise from the root of the aorta: left coronary artery and right coronary artery.
• Coronary artery pressure becomes higher than aortic pressure during systole.
• Blood flow through the coronary arteries occurs during diastole.
• Partial obstruction can lead to tissue ischemia (decreased oxygen supply), causing angina.
• Tissue death is infarction and is called Myocardial Infarction (MI).

Problems With Coronary Blood Flow

• Myocardial ischemia is a partial obstruction of the coronary artery, decreasing oxygen supply to tissue (angina pectoris).
• Myocardial infarction (MI) is a complete obstruction of the coronary artery, causing death of heart tissue.

Myocardial Infarction

• Most common cause is thrombus formation (blood clot) that blocks the coronary artery.
• Myocardial infarction (heart attack) is caused by a prolonged lack of blood flow and oxygen delivery to part of the cardiac muscle.

Myocardial Infarction Interventions

• Cardiac catheterization is a diagnostic and treatment intervention.
• Angioplasty, including balloon angioplasty, is a treatment intervention.
• Stents (metal mesh tubes) can be used.
• Coronary bypass uses healthy blood vessels from other body parts to bypass obstructions.

Properties of Heart Muscle

• Contractility: contraction in response to an electrical impulse (primary function of the myocardium).

Vascular System

• There are two circulations in the one body.
• Composed of two major subdivisions: systemic vasculature and pulmonary vasculature.
• Systemic vasculature begins with the aorta on the left ventricle and ends in the right atrium.
• Pulmonary vasculature begins with the pulmonary trunk out of the right ventricle and ends in the left atrium.
• Systemic venous blood returns to the right atrium via the superior vena cava (SVC) and the inferior vena cava (IVC).
• SVC drains the upper extremities and head.
• IVC drains the lower body.
• Blood flows through the tricuspid valve into the right ventricle.

Vascular Resistance

• The sum of all opposing forces to blood flow through systemic circulation is systemic vascular resistance (SVR).
• SVR = (MAP – RAP)/CO where MAP = mean aortic pressure, RAP = right atrial pressure or CVP, and CO = cardiac output.

Pulmonary Vascular Resistance (PVR)

• PVR is the sum of all opposing forces to blood flow through pulmonary circulation.
• PVR = (MPAP – LAP)/CO where MPAP = mean pulmonary artery pressure, LAP = left atrial pressure or wedge pressure, and CO = cardiac output.

Cardiac Output (CO)

• Cardiac output is the amount of blood discharged from the left or right ventricle per minute.
• Stroke volume is the amount of blood ejected by the left ventricle at each heartbeat.
• Calculated by multiplying stroke volume (SV) by heart rate (HR).

Cardiac Output and Blood Pressure

• Cardiac output directly influences blood pressure.
• When either SV or HR increases, blood pressure increases.
• When either SV or HR decreases, blood pressure decreases.

Determinants of Blood Pressure

• The first priority of the cardiovascular system is to keep perfusion pressures to tissues and organs normal, even under changing conditions.
• MAP = ((Diastolic x 2) + Systolic) / 3.
• MAP is regulated by changing the volume of blood circulating, the capacity of the vascular system, or both.
• Normal MAP is around 80-100 mmHg.
• A MAP below 60 mmHg severely compromises perfusion to the brain and kidneys, leading to organ failure.