12. Blood I - MH - A&P I Sp2025

Course: BIO 111C - Fundamentals in Anatomy & Physiology IInstructor: Dr. Michael Ha, M.D.Institution: University of District of Columbia

Topics Covered: Contraction Cycle, Whole Muscles, Smooth and Cardiac Muscle, Circulatory System Structure

Main Components:
- Heart: Central organ in circulation responsible for pumping blood.
- Blood Vessels: System of tubes (arteries, veins, capillaries) transporting blood.
- Blood: Fluid that carries nutrients, oxygen, and waste products.
Functions:
- Transportation:
  - Delivers oxygen and nutrients to cells throughout the body.
  - Removes metabolic waste products such as carbon dioxide, urea, and toxins.
- Regulation:
  - Regulates body temperature by directing blood flow to the skin or internal organs to disperse heat.
  - Distributes hormones released from various endocrine glands throughout the body.
  - Maintains pH balance of the body fluids by buffering acids and bases in the blood.
- Protection:
  - Supports immune responses through the action of white blood cells and antibodies present in the blood.
  - Initiates clotting processes to prevent excessive blood loss from injuries.

Location:
- Located in the mediastinum, between the lungs, tilted towards the left side of the thoracic cavity.
Structure:
- Four-chambered organ consisting of:
  - Epicardium: The outer layer comprised of visceral pericardium.
  - Myocardium: The thick muscular middle layer which contracts to pump blood.
  - Endocardium: The smooth inner lining that allows for easy blood flow and prevents turbulence.
Function:
- Generates sufficient pressure for pulmonary (to the lungs) and systemic (to the body) circulation, ensuring all tissues receive adequate blood supply and nutrients.

Categories:
- Arteries: Carry oxygenated blood away from the heart, except for pulmonary arteries which carry deoxygenated blood to the lungs.
- Arterioles: Smaller branches of arteries that lead to capillary networks.
- Capillaries: Microscopic vessels where exchange of gases (O2, CO2), nutrients, and waste occurs between blood and tissues.
- Venules: Collect deoxygenated blood from capillaries and transport it to veins.
- Veins: Return deoxygenated blood back to the heart, except for pulmonary veins which carry oxygenated blood from the lungs.
Layers of Blood Vessels:
- Tunica Intima: Innermost layer composed of a thin layer of endothelial cells that provides a smooth surface for blood to flow.
- Tunica Media: Middle layer consisting of smooth muscle and elastic fibers; responsible for regulating blood vessel diameter through vasoconstriction and vasodilation.
- Tunica Adventitia: Outermost layer providing structural support and protection to the vessel wall.
Valves:
- Present in veins to prevent backflow of blood, ensuring unidirectional flow towards the heart, especially in the limbs.

Types of Components:
- Formed Elements (45%): Cellular components of blood, including:
  - Erythrocytes: Red blood cells that transport oxygen via hemoglobin.
  - Leukocytes: White blood cells that are part of the immune system.
  - Platelets: Cell fragments crucial for blood clotting.
- Plasma (55%): Liquid component that serves as the medium for transporting cells and proteins, comprising 90% water.
Hematocrit Levels:
- Male: Approximately 47% ± 5%.
- Female: Approximately 42% ± 5%.
Physical Characteristics:
- Blood is sticky and has an opaque red color due to the presence of erythrocytes; pH ranges from 7.35 to 7.45; temperature is around 38°C (normal body temperature).

Appearance: Clear, straw-colored liquid that constitutes the fluid part of blood.
Components:
- Plasma Proteins: Key proteins include:
  - Albumins: Maintain osmotic pressure and transport substances.
  - Globulins: Function in immune response and transport.
  - Fibrinogen: Essential for blood clotting.
- Regulatory Substances: Hormones, enzymes, and other signaling molecules that regulate various physiological processes.
- Nutrients: Essential molecules like glucose, amino acids, and lipids required for cellular metabolism.
- Gases: Oxygen and carbon dioxide, vital for cellular respiration.
- Electrolytes: Ions such as sodium, potassium, calcium, bicarbonate, etc., that help in maintaining fluid balance and cellular functions.

Types:
- Erythrocytes: Primary function is to transport oxygen from lungs to all body cells.
- Leukocytes: Involved in the immune response to fight infection and disease.
- Platelets: Play a significant role in the clotting process to prevent bleeding.
Leukocyte Classes:
- Agranulocytes:
  - Monocytes: Differentiate into macrophages for phagocytic activity.
  - Lymphocytes: Subtypes include T-cells (cell-mediated immunity) and B-cells (humoral immunity).
- Granulocytes:
  - Neutrophils: First responders to infection.
  - Eosinophils: Combat parasitic infections and mediate allergic responses.
  - Basophils: Release histamine and play a role in inflammatory responses.
Leukopoiesis: The production of white blood cells occurs in the red bone marrow, where hematopoietic stem cells develop into various types of leukocytes based on body needs.

Normal Range: 150,000-400,000/mm³, which is crucial for effective hemostasis.
Function:
- Participate actively in hemostasis by forming a temporary plug at injury sites and releasing clotting factors to promote coagulation.
Production:
- Derived from megakaryocytes in bone marrow; have a short lifespan of 5-10 days before being replaced.

Stages of Hemostasis:
- Vascular Spasm: Initial response where blood vessels constrict to reduce blood loss.
- Platelet Plug Formation: Platelets adhere to exposed collagen fibers at injury sites and aggregate to form a temporary plug.
- Coagulation: Involves activation of intrinsic and extrinsic clotting pathways leading to the conversion of fibrinogen to fibrin, which stabilizes the platelet plug and seals the vessel effectively.