Blood Composition and Functions

Functions of Blood

• Transports oxygen, carbon dioxide, nutrients, heat, hormones, and waste products
• Involved in regulation of pH balance, water control, and heat balance
• Offers protection through immune reactions and blood clots

Red Blood Cells (Erythrocytes)

• Each hemoglobin molecule can carry up to four oxygen molecules

White Blood Cells

• Basophils secrete histamine and heparin
• Eosinophils combat parasitic infections and perform phagocytosis of allergens and inflammatory chemicals
• Neutrophils phagocytize bacteria and increase during bacterial infections, making up 60-70% of WBCs
• Monocytes increase during viral infections and chronic diseases
• Lymphocytes are immunity/defense cells, contain memory cells, and increase with diverse infections and immune responses

Platelets

• Platelets facilitate blood clotting

Blood Sample Collection

• Blood samples can be obtained to check for disease or drug use
• Venipuncture involves taking blood at the elbow, specifically from the median cubital vein
• Fingersticks are used for blood typing

Blood Testing

• Hematocrit measures the percentage of red blood cells in the blood and is used to diagnose anemia
• People at high altitudes have higher hematocrit levels
• Differential WBC count measures the number of each type of WBC in a sample of 100 and detects bacterial infections, radiation exposure, and drug use
• Complete Blood Count (CBC) is a common screening test for anemia, infections, hematocrit, WBC count, and platelet count

Blood Smears

• Blood smears of normal blood, mononucleosis, leukemia, and sickle cell anemia can be reviewed.

Mechanisms to Reduce Blood Loss

• Vascular spasm involves the contraction of smooth muscle in the blood vessel wall
• Platelet plug formation occurs
• Clot formation involves a gel composed of insoluble protein fibers that trap blood's formed elements

Blood Typing

• Blood types are identified by how the blood coagulates

Anemia

• Anemia reduces the oxygen carrying capacity of blood

Heart Disease Prevention

• Heart disease can be prevented by adopting a heart-healthy lifestyle and diet
• Heart-healthy lifestyle choices include a diet low in saturated fats, high in fruits, vegetables, and fiber, increased intake of good oils, and reduced sugar and salt intake
• Regular exercise is also crucial, as well as reduced stress and good sleep

Heart Layers

• The pericardium surrounds the heart, holds it in place, and contains fluid to reduce friction
• The myocardium is the muscular layer composed of involuntary, striated cardiac muscle with gap junctions and intercalated discs. The left ventricle is larger because it pumps blood to the entire body
• The endocardium is continuous with the epithelial lining of large blood vessels and heart valves

Arteries

• Arteries carry blood away from the heart and are typically oxygenated, with the exception of the pulmonary artery, which carries deoxygenated blood to the lungs

Veins

• Veins carry blood to the heart and are typically deoxygenated, with the exception of the pulmonary vein, which carries oxygenated blood from the lungs to the left atrium

Valves

• Valves prevent blood backflow

Blood Flow Through the Heart

• Blood enters the right atrium, passes through the tricuspid valve to the right ventricle, then through the pulmonary valve to the pulmonary arteries, the lungs (for gas exchange), the pulmonary veins, the left atrium, the bicuspid (mitral) valve, the left ventricle, the aortic valve
• Then, blood flows out to the body via the aorta (arteries, arterioles, capillaries [for gas exchange], venules, veins), then to the superior/inferior vena cava

Coronary Arteries

• Coronary arteries supply the heart with oxygen and nutrients
• Blockage of these arteries leads to myocardial infarction (heart attack)

Conduction System of the Heart

• The conduction system includes the SA node (pacemaker), AV node, AV bundle, left and right bundle branches, and Purkinje fibers

EKG (Electrocardiogram)

• An EKG records the electrical activity of the heart
• P wave indicates atrial depolarization (contraction/systole)
• QRS complex indicates atrial repolarization (relaxation/diastole) and ventricle depolarization
• S-T segment represents ventricle contraction
• T wave indicates ventricle relaxation
• A missing/inverted P wave indicates SA node damage and the AV node taking over as pacemaker
• An enlarged Q wave indicates myocardial infarction
• Ventricular fibrillation is when the heart quivers and doesn't effectively pump blood; defibrillation is the treatment

Medical Applications Related to the Heart

• Atherosclerosis is the narrowing of arteries
• Varicose veins are abnormal, dilated blood vessels caused by weakened vessel walls
• Heart attack (Myocardial Infarction) occurs when blood supply to a portion of the heart is cut off

Blood Vessels

• Vasoconstriction decreases blood flow
• Vasodilation increases blood flow
• Blood flows from arteries to arterioles to capillaries for gas exchange, then to venules and veins
• Capillaries are where gas exchange occurs
• Tissues with high metabolic requirements have many capillaries

Blood Pressure

• Blood pressure is the pressure in arteries generated by the left ventricle during systole and the pressure remaining when the ventricle is in diastole, and is highest in the arteries
• Systolic blood pressure is measured during left ventricle contraction and is the top number
• Diastolic blood pressure is measured when the left ventricle relaxes and is the bottom number
• Normal blood pressure is 110/70, and hypertension is anything over 140/90

Cardiovascular System Lab Key Points

• Determine a person's blood type.
• Identify microscope slides of blood affected by mononucleosis, sickle cell anemia, and leukemia
• Understand what an EKG is and how abnormal EKGs indicate specific heart conditions, such as a heart attack
• Differentiate between normal and abnormal heart sounds, where abnormal heart sounds often indicate a defective valve