Blood Composition and Function

• Blood consists of a liquid portion called plasma and blood cells

Composition of Blood: Plasma

• Plasma makes up 55% of blood
• Plasma is approximately 90% water
• Approximately 10% of plasma includes ions, proteins, nutrients, wastes and dissolved gases

Functions of Plasma

• Maintains blood pH
• Hormones act as long-distance signals
• Antibodies neutralize pathogens
• Clotting factors aid in blood clotting

Blood Cells: Red Blood Cells (RBCs)

• Main role is to carry oxygen and carbon dioxide
• RBCs are small with no mitochondria or nucleus
• RBCs have a biconcave shape for better gas exchange
• Hemoglobin in RBCs carries oxygen
• Some carbon dioxide binds to hemoglobin
• Other carbon dioxide is converted into bicarbonate for transport to lungs

Platelets

• Involved in blood clotting
• Platelets form a plug at a wound site
• Platelets release signals and activate fibrinogen to form fibrin threads
• Fibrin threads reinforce the clot

White Blood Cells (WBCs)

• Part of the immune system, neutralizing bacteria and viruses
• WBCs are larger than RBCs
• WBCs contain a nucleus and mitochondria
• Various WBCs specialize in engulfing pathogens or launching immune responses

Blood Cell Proportions

• Plasma makes up 55% of blood
• Red Blood Cells (RBCS) makes up 45% of blood
• Buffy coat (WBCs and platelets) makes up less than 1% of blood

Types of Blood Vessels: Arteries

• Arteries carry oxygenated blood away from the heart
• The exception is the pulmonary artery, which carries deoxygenated blood to the lungs
• Arteries have high pressure
• Elastic and muscular walls
• Arteries have a narrow lumen and pulse

Veins

• Veins return deoxygenated blood to the heart
• The exception is the pulmonary veins, which carry oxygenated blood from the lungs to the heart
• Veins have low pressure
• Veins have thin walls and a wide lumen
• They contain valves to prevent backflow

Capillaries

• Capillaries are tiny vessels with one-cell thick walls
• They link arteries to veins
• Allow exchange of materials (oxygen, nutrients, carbon dioxide) between blood and tissues
• Capillaries form dense networks around body cells for efficient diffusion

Special Blood Vessel: Hepatic Portal Vein

• Transports digested materials to the liver for detoxification

Function and Circulation

• The heart pumps blood throughout the body in a double circulatory system

Pulmonary Circuit

• Blood flows to and from the lungs for oxygenation

Systemic Circuit

• Oxygenated blood is pumped to the rest of the body

Blood Flow Sequence

• Superior and Inferior Vena Cava → Right Atrium
• Right Atrium → Right Ventricle
• Right Ventricle → Pulmonary Artery → Lungs
• Lungs → Pulmonary Vein → Left Atrium
• Left Atrium → Left Ventricle
• Left Ventricle → Aorta → Body

Heart Valves

• Pulmonary Valve: Located at the pulmonary artery
• Aortic Valve: Located at the aorta
• Tricuspid Valve: Right side of the heart
• Bicuspid (Mitral) Valve: Left side of the heart

Coronary Circulation

• Coronary Arteries: Supply oxygen and nutrients to the heart muscle
• Cardiac Veins: Remove waste products from the heart
• Heart Attack: Can occur if coronary arteries are blocked due to excess cholesterol

Heartbeat Sounds

• First Sound: Closing of the Bicuspid and Tricuspid valves
• Second Sound: Closing of the Aortic and Pulmonary valves

Cardiac Cycle

• Two main phases: Diastole (relaxation) and Systole (contraction)

Diastole

• Atria and ventricles relax
• Blood flows into the atria, and ventricles fill

Systole

• Atria contract, forcing blood into ventricles
• Ventricles contract, pumping blood to lungs (right ventricle) and body (left ventricle)

Blood Groups

• Type A: A antigens, Anti-B antibodies
• Type B: B antigens, Anti-A antibodies
• Type AB: Both A and B antigens, no antibodies (universal recipient)
• Type O: No antigens, both Anti-A and Anti-B antibodies (universal donor)