INTERNATIONAL UNIVERSITY

Functions and Major Components of the Circulatory System

Dr . Sam Nang

• An efficient circulatory system is necessary for maintaining the life of complex multicellular organisms.

• Objective 1 Describe the functions of the circulatory system.

• Objective 2 Describe the major components of the circulatory system.

• The blood contained within vessels serves this transportation function.

• An estimated 60,000 miles of vessels throughout the body of an adult ensure that continued sustenance reaches each of the trillions of living cells.

• However, the blood can also transport disease causing viruses, bacteria, and their toxins.

• As a safeguard, the circulatory system has defense mechanisms the white blood cells and lymphatic system.

• In order to perform its various functions, the circulatory system works together with the respiratory, urinary, digestive, endocrine, and integumentary systems in maintaining homeostasis

Functions of the Circulatory System

• The many functions of the circulatory system can be grouped into two broad areas:

transportation and protection.

• 1.Transportation a. Respiratory b. Nutritive c. Excretory d. Regulatory

• 2. Protection

1.Transportation• 1.Transportation. All of the

substances involved in cellular metabolism are transported by the circulatory system.

• These substances can be categorized as follows: a. Respiratory

b. Nutritive c. Excretory d. Regulatory

Respiratory• Red blood cells called erythrocytes

transport oxygen to the tissue cells.

• In the lungs, oxygen from the inhaled air attaches to hemoglobin molecules within the erythrocytes and is transported to the cells for aerobic respiration.

• Carbon dioxide produced by cellular respiration is carried by the blood to the lungs for elimination in the exhaled air.

Nutritive• The digestive system is responsible

for the mechanical and chemical breakdown of food to forms that can be absorbed through the intestinal wall into the blood and lymph vessels.

• The blood then carries these absorbed product; of digestion through the liver to the cells of the body.

Excretory

• Metabolic wastes, excess water and ions, as well as other molecules in plasma (the fluid portion of blood), are filtered through the capillaries of the kidneys into kidney tubules and excreted in urine.

Regulatory

• The blood carries hormones and other regulatory molecules from their site of origin to distant target tissues.

2. Protection The circulatory system protects

against injury and foreign microbes or toxins introduced into the body.

• The clotting mechanism protects against blood loss when vessels are damaged, and white blood cells called leukocytes render the body immune to many disease causing agents.

• Leukocytes may also protect the body through phagocytosis

Major Components of the Circulatory System

The circulatory system is frequently divided into :

• the cardiovascular system, which consists of the heart, blood vessels, and blood, and

• the lymphatic system, which consists of lymphatic vessels and lymphoid tissues within the spleen, thymus, tonsils, and lymph nodes.

Major Components of the Circulatory System

• The heart is a four chambered double pump. Its pumping action creates the pressure needed to push blood in the vessels to the lung; and body cells.

• At rest, the heart of an adult pumps about 5 liters of blood per minute.

• It takes only about a minute for blood to be circulated to the most distal extremity and back to the heart.

Major Components of the Circulatory System

• Blood vessels form a tubular network that permits blood to flow from the heart to all living cells of the body and then back to the heart.

• Arteries carry blood away from the heart, while veins return blood to the heart. Arteries and veins are continuous with each other through smaller blood vessels.

Major Components of the Circulatory System

• Arteries branch extensively to form a network of progressively smaller vessels. Those that are microscopic are called arterioles.

• Conversely, microscopic-sized veins called venules deliver blood to progressively larger vessels that empty into the large veins.

Major Components of the Circulatory System

• Blood passes from the arterial to the venous system in capillaries, which are the thinnest and most numerous blood vessels.

• All exchanges of fluid, nutrients, and wastes between the blood and tissue cells occur across the walls of capillaries.

Major Components of the Circulatory System

• Fluid derived from plasma passes out of capillary walls into the surrounding tissues, where it is called interstitial fluid or tissue fluid.

• Some of this fluid returns directly to capillaries and some enters into lymphatic vessels located in the connective tissues around the blood vessels.

Major Components of the Circulatory System

• Fluid in lymphatic vessels is called lymph. This fluid is returned to the venous blood at particular sites.

• Lymph nodes, positioned along the way, cleanse the lymph prior to its return to the venous blood.

THE END