Cardiovascular System: Blood Functions

• The cardiovascular system contributes to homeostasis.
• The system transports oxygen, carbon dioxide, nutrients, and hormones to and from body cells.
• It also regulates body pH and temperature.
• It provides protection against disease through phagocytosis and the production of antibodies.

Functions and Properties of Blood

• The cardiovascular system is composed of three interrelated components: blood, the heart, and blood vessels.
• Blood's functions include transportation (oxygen, CO2, hormones, waste products) , regulation (body temp, pH, hormones), and protection (platelets, WBCs).
• Blood is a liquid connective tissue consisting of cells surrounded by a liquid extracellular matrix.
• The extracellular matrix is called blood plasma which suspends various cells and cell fragments.
• Interstitial fluid is the fluid that bathes body cells and is constantly renewed by the blood.
• Blood is denser and thicker than water, with a temperature of 38°C (100.4°F) and a pH between 7.35-7.45
• Blood volume is 5-6L in males and 4-5L in females

Components of Blood

• Whole blood consists of 55% blood plasma and 45% formed elements.
• Blood plasma is 91.5% water, 7% proteins, and 1.5% other solutes.
• Water in blood plasma acts as a solvent and suspending medium, absorbing, transporting, and releasing heat.
• Plasma proteins are mostly produced by the liver and include albumins (54%), globulins (38%), fibrinogen (7%), and all others (1%).
• Albumins are the smallest and most numerous plasma proteins, responsible for colloid osmotic pressure, blood viscosity, transport.
• Globulins help maintain osmotic pressure and attack viruses and bacteria.
• Fibrinogen plays an essential role in blood clotting.
• Other solutes in blood plasma include electrolytes, nutrients, gases, regulatory substances, and waste products.
• Formed elements of blood include red blood cells (RBCs), white blood cells (WBCs), and platelets.
• Hematocrit refers to the percentage of total blood volume occupied by RBCs
• Normal hematocrit range for adult females is 38-46% (average = 42), and for adult males is 40–54% (average = 47).

Formation of Blood Cells

• Blood cells are formed from progenitor cells, precursor cells, formed elements of circulating blood, and tissue cells

Red Blood Cells

• Red blood cells (RBCs) or erythrocytes contain hemoglobin which gives whole blood its red color
• A healthy adult male has about 5.4 million red blood cells per microliter (µL) of blood, and a healthy adult female has about 4.8 million.
• Each RBC contains about 280 million hemoglobin molecules.
• A hemoglobin molecule consists of a protein called globin, composed of four polypeptide chains
• A heme is bound to each of the four chains.
• At the center of each heme ring is an iron ion (Fe2+) that can combine reversibly with one oxygen molecule, allowing each hemoglobin molecule to bind four oxygen molecules.
• Each oxygen molecule picked up from the lungs is bound to an iron ion.
• As blood flows through tissue capillaries, the iron-oxygen reaction reverses and hemoglobin releases oxygen.