Circulation and Cardiovascular System

5.2 Transport in Vertebrates

All vertebrate animals have a closed circulatory system, which is called a cardiovascular system.All vertebrate animals have a closed circulatory system, which is called a cardiovascular system. It consists of a heart in which the atria receive blood and the muscular ventricles pump blood through the blood vessels. It consists of a heart in which the atria receive blood and the muscular ventricles pump blood through the blood vessels.

There are three kinds of blood vessels: Arteries, which carry blood away from the heart Capillaries, which exchange materials with tissue fluid Veins, which return blood to the heart

There are three kinds of blood vessels: Arteries, which carry blood away from the heart Capillaries, which exchange materials with tissue fluid Veins, which return blood to the heart

5.3 Transport in Humans

The human heart lies within the pericardium, a thick, membranous sac that secretes a small quantity of lubricating liquid. The human heart lies within the pericardium, a thick, membranous sac that secretes a small quantity of lubricating liquid.

The inner surface of the heart is lined with endocardium, a membrane composed of connective tissue and endothelial tissue. The inner surface of the heart is lined with endocardium, a membrane composed of connective tissue and endothelial tissue.

Internally, the septum separates the heart into a right side and a left side. right side Left side

The heart has four chambers. The two upper thin walled called atria. The two lower chambers are thick walled called ventricles, which pump the blood.

The heart also has four valves, which direct the flow of blood and prevent its backward movement. The two valves that lie between the atria and the ventricles are called the atrioventricular valves.

The atrioventricular valve on the right side is called the tricuspid valve because it has three flaps, or cusps. The valve on the left side is called the bicuspid (or the mitral) because it has two flaps.

The remaining two valves are the semilunar valves, whose flaps resemble half moons, between the ventricles and their attached vessels.

The pulmonary semilunar valve lies between the right ventricle and the pulmonary trunk. The aortic semilunar valve lies between the left ventricle and the aorta.

Path of Blood Through the Heart

The superior vena cava and inferior vena cava carry blood to the right atrium.

The right atrium sends blood through an atrioventricular valve (the tricuspid valve) to the right Ventricle.

The right ventricle sends blood through the blood through the pulmonary semilunar valve into the pulmonary trunk into the pulmonary trunk and the two pulmonary arteries to the lungs. arteries to the lungs.

From the lungs, four pulmonary veins, which carry oxygen rich blood, which carry oxygen rich blood, enter the left atrium.

The left atrium sends blood through an through an atrioventricular valve (the bicuspid or mitral valve) (the bicuspid or mitral valve) to the left ventricle. to the left ventricle.

The left ventricle sends blood through the aortic semilunar valve into the aorta to the body

The normal average human heart beats are about 70 times per minute. The term systole refers to contraction of the heart chambers, and the word diastole refers to relaxation of these chambers. The term systole refers to contraction of the heart chambers, and the word diastole refers to relaxation of these chambers.

5.4 Blood, a Transport Medium

Functions of The blood

In humans, blood has two main portions: In humans, blood has two main portions: 1. The liquid portion, called plasma. Plasma contains many types of molecules, including nutrients, wastes, salts, and proteins. 2. The formed elements, which are of three types: red blood cells, or erythrocytes ; white blood cells, or leukocytes ; and platelets, or thrombocytes.

Red Blood Cells Red blood cells are small, biconcave disks. Red blood cells are small, biconcave disks. At maturity they lack a nucleus. At maturity they lack a nucleus. They contain the the respiratory pigment hemoglobin. Hemoglobin carries oxygen or carbon dioxide. If there is an insufficient number of red blood cells, or if the cells do not have enough hemoglobin, the individual suffers from anemia and has a tired, run down feeling. They contain the the respiratory pigment hemoglobin. Hemoglobin carries oxygen or carbon dioxide. If there is an insufficient number of red blood cells, or if the cells do not have enough hemoglobin, the individual suffers from anemia and has a tired, run down feeling.

Red Blood Cells Approximately there are 6 million red blood cells per cubic millimeter. Approximately there are 6 million red blood cells per cubic millimeter. They are manufactured continuously in the red bone marrow of the skull, the ribs, the vertebrae, and the ends of the long bones. They are manufactured continuously in the red bone marrow of the skull, the ribs, the vertebrae, and the ends of the long bones. There life span about 120 days. There life span about 120 days.

White blood cells differ from red blood cells in that they are usually larger, have a nucleus, and they lack hemoglobin. Defense against disease depends on the various types of white blood cells.

Neutrophils and monocytes are phagocytic and are very active during the inflammatory reaction. Neutrophils and monocytes are phagocytic and are very active during the inflammatory reaction. Lymphocytes are involved in the development of immunity to disease. Lymphocytes are involved in the development of immunity to disease. Eosinophils are important in allergic reactions and parasitic infections Eosinophils are important in allergic reactions and parasitic infections basophils contain the anticoagulant heparin. basophils contain the anticoagulant heparin.

Platelets Platelets (thrombocytes) result from fragmentation of certain large cells, called megakaryocytes, in the red bone marrow. Platelets (thrombocytes) result from fragmentation of certain large cells, called megakaryocytes, in the red bone marrow. The blood contains 150,000 – 300,000 per mm3. These formed elements are involved in blood clotting, or coagulation. The blood contains 150,000 – 300,000 per mm3. These formed elements are involved in blood clotting, or coagulation.