Cardiovascular System: Heart and Blood Vessels

Cardiovascular System: Heart and Blood Vessels

• The cardiovascular system consists of the heart, which pumps blood, and blood vessels that transport blood to and from the tissues.
• The system has three main functions: transport, protection, and regulation.

Functions of the Cardiovascular System

• Transport: transports oxygen to the cells of the body, removes carbon dioxide and other waste products of metabolism, and transports nutrients from the digestive system and hormones from the endocrine system to the cells of the body.
• Protection: transports the cells of the immune system to help protect the body from infection.
• Regulation: participates in the homeostasis of a variety of the body's conditions, including temperature, pH balance, and water and electrolyte levels.

The Types of Blood Vessels

• The cardiovascular system consists of three types of blood vessels: arteries, veins, and capillaries.

The Arteries

• Arteries are blood vessels that transport blood away from the heart.
• The structure of an artery is well suited for the transport of blood leaving the heart under pressure.
• The arterial wall has three layers: endothelium, a middle layer of smooth muscle, and elastic tissue.
• The strong walls of an artery give it support when blood enters under pressure; the elastic tissue allows an artery to expand to absorb the pressure.

Arterioles

• Arterioles are small arteries that are barely visible to the naked eye.
• The middle layer of arterioles has some elastic tissue, but it is composed mostly of smooth muscle.

Blood Flow in Veins

• Blood pressure plays only a small role in returning venous blood to the heart, called venous return.
• Venous return is dependent on three additional factors: the skeletal muscle pump, the respiratory pump, and valves in veins.

Disorders of the Blood Vessels

• Hypertension: occurs when blood moves through the arteries at a higher pressure than normal, with a systolic blood pressure of 130 or greater or a diastolic blood pressure of 80 or greater.
• Atherosclerosis: a condition where the arteries become narrowed or blocked due to the buildup of plaque.
• Aneurysm: a condition where a blood vessel bursts or ruptures.

Functions of Blood

• Transport: oxygen, nutrients, carbon dioxide, and other waste products of metabolism.
• Defense: white blood cells produce and secrete antibodies to fight infection.
• Regulation: blood plays an important role in regulating the body's homeostasis, including temperature, pH balance, and water and electrolyte levels.

Composition of Blood

• Blood is a form of liquid connective tissue.
• Cell fragments are suspended in a liquid called plasma.
• The formed elements are red blood cells, white blood cells, and platelets.

Disorders Involving Red Blood Cells

• Anemia: a condition where there is an insufficient number of red blood cells or the cells do not have enough hemoglobin.
• Iron-deficiency anemia: the most common form of anemia.
• Hemolytic anemia: a condition where the rate of red blood cell destruction increases.
• Sickle-cell disease: a hereditary condition where the individual has sickle-shaped red blood cells.

White Blood Cells and Defense Against Disease

• White blood cells (leukocytes) differ from red blood cells in that they are usually larger, have a nucleus, lack hemoglobin, and are translucent unless stained.
• White blood cells fight infection and are an important part of the immune system.
• White blood cells fight infection in various ways, including phagocytosis and producing antibodies.

Types of White Blood Cells

• Granular leukocytes: include neutrophils, eosinophils, and basophils.
• Agranular leukocytes: include lymphocytes and monocytes.

Platelets and Blood Clotting

• Platelets (thrombocytes) result from the fragmentation of large cells, called megakaryocytes, in the red bone marrow.
• Platelets are involved in the process of blood clotting, or coagulation.
• Blood clotting helps the body maintain homeostasis in the cardiovascular system by ensuring that the plasma and formed elements remain within the blood vessels.

Disorders Related to Blood Clotting

• Thrombocytopenia: a condition where there is a low platelet count due to either low platelet production in bone marrow or an increased breakdown of platelets outside the marrow.
• Hemophilia: an inherited clotting disorder that causes a deficiency in a clotting factor.