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SBI3C Ms Mak: THE CIRCULATORY SYSTEM The circulatory system (CS) is the transport system of the body. - complex network of tissues and organs (see Fig 2 pg. 196) - 96 000 km of blood vessels in your body to sustain you 100 trillion cells It has 4 principal functions: - transportation of oxygen and carbon dioxide distribution of nutrients and transport of wastes maintenance of body temperature circulation of hormones Structure of Circulatory System It consists of 3 components - fluid in which materials are transported: blood - system of blood vessels or spaces throughout the body - pump: heart Cardiovascular system: heart + blood vessels Circulatory System has two major circuits: 1. Pulmonary circuit: carries blood between the heart and the lungs (to and from lungs): o pulmonary arteries: carry O2-poor blood to the lungs o pulmonary veins: carry O2-rich blood to the heart 1 of 4 SBI3C 2. Systemic circuit: caries blood between the heart and the rest of the body (to and from the body); includes 3 branches: o coronary: supplies blood to the muscle of the heart. o hepatic-portal: carries blood from the digestive tract to the liver. o renal: carries blood to & from the kidneys. Blood from the systemic system enters the right atrium. Blood from the pulmonary system enters the left atrium. HEART Function of Heart: - acts as a pump; made of cardiac muscle - right side: sends O2-poor blood to heart - left side: sends O2-rich blood to body - location: left of the middle of the chest cavity Structure - pericardium: covers and protects the heart - Heart is divided into 4 chambers: o atria (auricles): two upper, thin-walled o ventricles: two lower, thick-walled - right and left sides of the heart are separated by a wall called septum: o prevents mixing O2-poor blood (right side) with O2rich blood (left side). 2 of 4 SBI3C - 4 flaplike valves control the direction of the blood flow inside the heart. o two of these valves: atrioventricular or A-V valves: prevent blood from flowing from ventricles into the atria. o the other two valves: the semilunar valves (S-L valves): prevent blood from flowing from arteries into the ventricles. The Heart Rhythms, Sounds and Pressure Heart has 2 bundles of nerves that control its beating - Sinoatrial (SA) node: acts as a pacemaker and sets a rhythm of about 72 beats per minute. - Atrioventricular (AV) node: passes the nerve impulses to the ventricles ( causes them to contract in unison) 2 main periods: - Diastole: the period of relaxation (dilation); A-V valves are open; blood flows from the atria into the ventricles: o atria relaxed; ventricles contracted. - Systole: the period of contraction; blood is pushed out of the heart o atria contracted; ventricles relaxed. - The lubb-dubb sound: caused by closing of the A-V valves and the S-L valves: o lubb: when increasing pressure forces the 3 of 4 SBI3C right and left A-V valves shut (systole). o dubb: when decreasing pressure forces the right and left S-L valves shut (diastole). Blood Pressure - is a force of blood on the walls of the arteries. - measured by sphygmomanometer (mm Hg) o systolic blood pressure (contraction of ventricles); about 120 mm Hg o diastolic blood pressure (relaxation of ventricles); about 80 mm Hg - elastic connective tissue and muscular walls of the arteries help to maintain blood pressure 4 of 4