Circulation and Heart Structures Unit D – Human Systems

Circulatory Systems in your Body There are two circulatory systems in your body: 1. Pulmonary circulatory system 2. Systemic circulatory system

1. Pulmonary Circulatory System Blood vessels that circulate blood between the heart and the lungs. Carries deoxygenated blood to the lungs and brings oxygenated blood back to the heart.

2. Systemic Circulatory System Blood vessels that carry blood between your heart and all other parts of the body. Pumps oxygenated blood to all body tissues and returns deoxygenated blood back to the heart. Watch this:

Basic Heart Anatomy The heart is made up of two halves, the left and the right. Each side of the heart is comprised of two chambers. Upper chambers are called atria, lower chambers are called ventricles.

Starting with deoxygenated blood coming from the vena cava Deoxygenated blood from your head and upper body enters the right atrium of your heart from the superior vena cava. Deoxygenated blood from the lower regions of your body enters the right atrium of your heart from the inferior vena cava.

Events occurring in the right atrium Blood collects in the right atrium until the pressure inside forces a set of valves called the right atrioventricular (AV)/tricuspid valves open. Valves make sure that blood only travels in one direction. Blood now enters the right ventricle, where it pools until the pressure inside increases, forcing the semilunar valves open.

Blood flow to the lungs Semilunar valves separate the ventricles from the arteries. Deoxygenated blood now flows through the left and right pulmonary arteries to the lungs. In the lungs, carbon dioxide will be released, and oxygen will combine with hemoglobin.

Blood flow back to the heart Oxygenated blood returns to the heart via the left and right pulmonary veins, where they will empty into the left atrium of the heart. Blood will pool in the left atrium of the heart, until the pressure builds up, forcing the left AV (bicuspid) valves to open.

Blood flow to the body Blood passes through the left AV valves into the left ventricle. Again, blood collects until sufficient pressure builds up. Blood passes through the left semilunar valves into the aorta, the largest artery in your body. The aorta branches off into smaller arteries, taking blood to all parts of your body.

Heart Muscle Made of myogenic muscle. Myogenic muscle has the ability to contract without stimulation from the nervous system…it can beat by itself. For a short time, your heart will continue to beat, even if it is removed from the body. Watch this: NR=1

Heart Rate and Contractions Set by the sinoatrial (SA) node, a bundle of nerves known as the “pacemaker” of the heart. Heart rate is typically set at about 70 beats per minute. SA node sends nerve impulses to another bundle of nerves called the atrioventricular (AV) node. Watch this: &NR=1

This nervous impulse causes the atria of the heart to contract, pushing blood into ventricles. The signal is then continued to the end of the ventricles causing them to contract, pushing the blood into the arteries.

Diastole Relaxation of heart muscle, when the atria of the heart are filling with blood. Increased blood volume and muscle contraction increase blood pressure, forcing the AV valves open. Blood rushes into the ventricles of the heart, causing the AV valves to shut. This causes the heavy “LUBB” sound.

Systole Very quickly, increase blood volume and muscle contractions increase pressure in the ventricles. This forces semilunar valves open, letting blood rush into arteries. Semilunar valves close, causing the lighter “DUBB” sound.

Heart Murmur Occurs when heart valves do not close properly. Can be diagnosed by hearing a gurgling sound when listening with a stethoscope. This means that blood can flow backwards, not in the direction it is intended to. Decreases oxygen delivery to body tissues.

Student Tasks for Lesson Label Heart Structures diagram given to you by your teacher and colour parts of heart accordingly: red for parts carrying oxygenated blood, blue for parts carring deoxygenated blood. Complete #1-3, 7 on page 327.