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

Cell Type

Description

Normal Count (cells/mm³)

Lifespan

Main Functions

Basophils

Bilobed nucleus; many large granules

20-50

Days (a few hours)

Release histamine for inflammation

Lymphocytes

Spherical nucleus, pale blue cytoplasm

1500-3000

Hours to years

Immune response (T cells & B cells)

Monocytes

Kidney-shaped nucleus, gray-blue cytoplasm

100-700

Months

Phagocytosis; develop into macrophages

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