11+A-Cardiovascular+Physiology

Cardiovascular Physiology Overview

• Lecturer: Dr. R. Ahangari

• Institution: University of Central Florida, Orlando

• Textbook Reference: Human Physiology by Linda S. Constanzo

• Additional Reference: Medline Plus

Functions of the Circulatory System

1. Transportation

   • Carries respiratory gases

   • Transports metabolites and nutrients

2. Regulation

   • Hormonal regulation

   • Temperature control

3. Protection

   • Clotting mechanism protects against blood loss

   • Immune response through leukocytes against disease

• Blood Volume:

  • Males: 5-6 liters

  • Females: 4-5 liters

Blood Composition

• Definition: Specialized connective tissue with cellular and liquid components

• Blood Cells (formulated elements) and Plasma (fluid portion)

• Hematocrit: Volume percentage of red blood cells in blood

  • Males: 42-52%

  • Females: 37-47%

Blood Plasma Characteristics

• Description: Straw-colored, sticky fluid

• Composed of approximately 90% water containing:

  • Ions (e.g., Na+)

  • Nutrients

  • Hormones

  • Enzymes

  • Antibodies

  • Wastes

  • Proteins

• Main Plasma Proteins:

  • Albumin (60-80%): Regulates osmotic pressure, produced by the liver

  • Globulins: Transport lipids, function in immunity

  • Fibrinogen: Essential for blood clotting, also produced by the liver

• Formed Elements:

  • Erythrocytes (red blood cells)

  • Leukocytes (white blood cells)

  • Platelets (thrombocytes)

Erythrocytes (Red Blood Cells)

• Contain 280 million hemoglobin molecules (responsible for red color)

• Each hemoglobin molecule:

  • Consists of four protein chains (globins)

  • Bound to one heme (iron-containing)

• Production: Originates in the bone marrow

Production and Lifespan of RBCs

• Control Mechanism: Hormonal; stimulated by erythropoietin

  • Produced in the kidneys (90%) and liver

• Lifespan: Approximately 120 days; aged RBCs removed by the spleen

Leukocytes (White Blood Cells)

• Possess nuclei and mitochondria, capable of amoeboid movement

• Move through capillary pores (diapedesis or extravasation)

• Types:

  • Agranular Leukocytes: Lymphocytes, Monocytes

  • Granular Leukocytes: Eosinophils, Basophils, Neutrophils

Formed Elements Summary

Lymphocytes

• Comprise 20–45% of WBCs

• Key components of the immune system, dark purple-staining nuclei

• Two main classes:

  • T cells: Attack foreign cells directly

  • B cells: Develop into plasma cells that secrete antibodies

Monocytes

• Comprise 4-8% of WBCs

• Largest type, phagocytic, kidney-shaped nucleus

• Transform into macrophages in tissues

Platelets (Thrombocytes)

• Role: Essential for blood clotting

  • Release serotonin to constrict blood vessels and reduce bleeding

  • Secrete growth factors and act as autocrine regulators

Hematopoiesis

• Origin: Begins in yolk sac of the embryo, then moves to liver, and finally the bone marrow

• Types of Blood Cell Formation:

  • Erythropoiesis: Formation of erythrocytes

  • Leukopoiesis: Formation of leukocytes

• Occurs in myeloid and lymphoid tissues post-birth

  • Myeloid: Red bone marrow (in long bones, sternum, pelvis, vertebrae)

  • Lymphoid: Includes lymph nodes, spleen, tonsils, thymus

Stages of Blood Cell Differentiation

• Cell Types:

  • Originates from blood stem cells

  • Myeloid stem cells form all blood types except lymphocytes

  • Lymphoid stem cells form lymphocytes

Disorders of Erythrocytes

1. Polycythemia: Excess erythrocytes

2. Anemia: Low levels of erythrocytes or hemoglobin concentrations

   • Normocytic Anemia: Due to blood loss

   • Microcytic Anemia: Due to iron deficiency

   • Macrocytic Anemia: Due to Vitamin B12 or Folate deficiency

   • Sickle Cell Disease: Genetic condition causing sickle-shaped RBCs

Disorders of Leukocytes

• Leukemia: Blood cancer classified into lymphoblastic or myeloblastic forms

Disorders of Platelets

• Thrombocytopenia: Abnormally low platelet counts

Blood Vessel Anatomy

• Layers:

  • Tunica Intima: Simple squamous epithelium

  • Tunica Media: Smooth muscle

  • Tunica Externa: Connective tissue

• Lumen: Central space within vessels

Types of Blood Vessels

• Arteries: Carry blood away from heart

• Veins: Carry blood toward heart

• Capillaries: Site of exchange between blood and tissues

• Artery Types:

  1. Elastic Arteries: Large, high in elastin

  2. Muscular (Distributing) Arteries

  3. Arterioles: Smallest arteries

Capillary Structure and Function

• Description: Smallest blood vessels, diameter 8-10 µm

• RBCs pass through in single file

• Capillary Beds: Networks of capillaries in tissues with varying permeability

• Special Types:

  • Low Permeability Capillaries: Blood-brain barrier

  • Sinusoids: Wide and leaky, found in spleen and liver

Erythrocyte Lifecycle

• RBCs die after about 120 days, removed by the liver

• Kupffer cells (phagocytic) engulf and break down hemoglobin

• Product Breakdown:

  • Globin: Hydrolyzed into amino acids

  • Heme: Iron is stored in the liver, bilirubin is modified and secreted in bile