Section 34-1

Section 34-1 The Circulatory System Bio 30 NWRC

Functions of the circulatory system • The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries.

Blood Vessels • Arteries • Arteries are muscular blood vessels that carry blood away from the heart All arteries, (with the exception of the pulmonary and umbilical arteries), carry oxygenated blood.

Capillaries • Branch throughout the body • Microscopic blood vessels -capillaries are very thin and fragile. The capillaries are actually only one epithelial cell thick. They are so thin that blood cells can only pass through them in single file

Capillaries • The exchange of oxygen and carbon dioxide takes place through the thin capillary wall. The red blood cells inside the capillary release their oxygen which passes through the wall and into the surrounding tissue. The tissue releases its waste products, like carbon dioxide, which passes through the wall and into the red blood cells.

Veins • In the circulatory system, a vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry lowoxygen blood from the tissues back to the heart

The Heart- watch video • Muscular organ about as large as your fist • The heart is the key organ in the circulatory system. As a hollow, muscular pump, its main function is to propel blood throughout the body. It usually beats from 60 to 100 times per minute

The Heart is divided into 4 chambers Right Atrium

Left Atrium

Right Ventricle

Left Ventricle

The Heart is divided into 4 chambers Right Atrium

Left Atrium

The Atria -The right atrium receives de-oxygenated blood from the body through the superior vena cava (head and upper body) and inferior vena cava (legs and lower torso). The left atrium receives oxygenated blood from the lungs through the pulmonary vein. As the contraction triggered by the sinoatrial node progresses through the atria, the blood passes through the mitral valve into the left ventricle.

The Heart is divided into 4 chambers The right ventricle is one of four chambers (two atria and two ventricles) in the human heart. It receives de-oxygenated blood from the right atrium via the tricuspid valve, and pumps it into the pulmonary artery via the pulmonary valve.

Right Ventricle

Left Ventricle

Left ventricle: The left lower chamber of the heart that receives blood from the left atrium and pumps it out under high pressure through the aorta to the body.

The chambers • Right Atrium • Left atrium • Left ventricle • Right ventricle

Blood flow through the Heart • Deoxygenated blood returns to the heart • Superior Vena cava • Inferior Vena cava

Blood flow through the Heart • Deoxygenated Blood collects in the right atrium

Blood flow through the Heart • Blood passes into the right ventricle through the tricuspid valve • The ventricle is a powerful pump which pushes the deoxygenated blood out to the lungs

Blood flow through the Heart • Blood passes into the pulmonary artery

Blood flow through the Heart • Oxygenated blood returns to the heart from the lungs • Pulmonary veins return oxygenated blood from the lungs to the heart

Blood flow through the Heart • Oxygenated blood collects in the left atrium

Blood flow through the Heart • Oxygenated blood passes into the left ventricle • Again the left ventricle is a powerful pump which must squeeze the blood out into the body

Blood flow through the Heart • Blood passes into the aorta and out to body

The Human Heart • Link to web site – watch the animations and interactive lessons

Valves of the heart •

The valves of the heart are located within the chambers of the heart and are critical to the proper flow of blood through the heart. All of the valves, when functioning normally, act as one-way valves, allowing blood to flow either from one chamber to another, or allowing blood to flow out of the heart, in only one direction. The valves control the flow of blood through the heart by opening and closing during the contractions of the heart.

The “Pacemaker” •

Acting as the heart's natural pacemaker, the SA node "fires" at regular intervals to cause the heart of beat with a rhythm of about 60 to 70 beats per minute for a healthy, resting heart. The electrical impulse from the SA node triggers a sequence of electrical events in the heart to control the orderly sequence of muscle contractions that pump the blood out of the heart.

The “Pacemaker” • The sinus rhythm

normally controls both atrial and ventricular rhythm. Action potentials generated by the SA node spread throughout the atria, depolarizing this tissue and causing atrial contraction. The impulse then travels into the ventricles via the atrioventricular node (AV node). This causes the ventricles to contract – the 2 step process makes a complete heartbeat

Pulse • a person's pulse is the throbbing of their arteries as an effect of the heartbeat. It can be felt in any place that allows for an artery to be compressed against a bone, such as at the neck at the wrist ,behind the knee, and on the inside of the elbow , or near the ankle joint

Blood Pressure • Blood pressure is the pressure of the blood against the walls of the arteries. • Blood pressure results from two forces. One is created by the heart as it pumps blood into the arteries and through the circulatory system. The other is the force of the arteries as they resist the blood flow.

Blood Pressure • The higher (systolic) number represents the pressure while the heart contracts to pump blood to the body. • The lower (diastolic) number represents the pressure when the heart relaxes between beats. • The systolic pressure is always stated first. Normal is 120/80 although that is variable with different sources

Blood Components • Blood plasma is the liquid component of blood, in which the blood cells are suspended. It makes up about 55% of total blood volume.

Blood Components • Red Blood Cells. A single drop of blood contains millions of red blood cells which are constantly traveling through your body delivering oxygen and removing waste.

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Blood Components Red blood cells are red only because they contain a protein chemical called hemoglobin which is bright red in colour. Hemoglobin contains the element Iron, making it an excellent vehicle for transporting oxygen and carbon dioxide. As blood passes through the lungs, oxygen molecules attach to the hemoglobin. As the blood passes through the body's tissue, the hemoglobin releases the oxygen to the cells. The empty hemoglobin molecules then bond with the tissue's carbon dioxide or other waste gases, transporting it away.

Blood Components

• Platelets :Platelets are irregularly-shaped, colourless cell fragments that are present in blood. Their sticky surface lets them, along with other substances, form clots to stop bleeding. The platelets release a chemical called FIBRIN which weaves a network of fibres across a cut and enables healing

Blood Components

• White Blood Cells • White blood cells or leukocytes are cells of the immune system defending the body against both infectious disease and foreign materials.

Blood Types • See Table 34-1 on page 998 • As you know there are 4 possible blood types: A B O or AB • There are several possible markers on your blood cells if you have type A you have A markers, B you have B markers • And if you have AB you have both and neither if you have type O blood

Blood Types • The plasma (liquid part of the blood) has proteins called ANTIBODIES which attack foreign markers and cause the blood to clump. • TYPE A blood has anti-B proteins • TYPE B blood has anti-A proteins • TYPE AB blood has no anti -proteins • TYPE O blood has both anti- A and anti-B proteins

Blood Types • People with blood group 0 are called "universal donors" (they can safely give blood to anyone because their blood has no markers) and people with blood group AB are called "universal receivers." (they can receive blood from anyone because they have no antibodies)

Blood Types • RH factor Many people also have a Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-.

Blood Types

• A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.

Assessment • 1. The main function of the circulatory system is to supply your body cells with O2 and nutrients and also to remove wastes including CO2

Assessment • 2.

Assessment • 3. Arteries have a thicker wall than veins have – veins have valves and arteries do not

Assessment • 3. For every 100 white blood cells there would be about 50-100,000 red blood cells