The Circulatory System /biology/the-human- body/circulatory-system/

The Circulatory System A System of interconnected, one-way roads – From superhighways to back alleys – Allows the transport of materials from one place to another Hormones Oxygen Cellular Wastes Nutrients – Heart, Blood vessels, and Blood

The Heart Consists mainly of cardiac muscle that pumps blood throughout the system 4 Chambers – 2 upper Atria – 2 lower ventricles Valves keep the blood flow going in only 1 direction ?v=hCp4hVC2fnM

Heartbeat Cardiac muscle contracts without stimulation by the nervous system – Specialized cardiac muscle cells send out electrical impulses that stimulate the contractions – Normally this all happens in perfect synchronization – topics/topics/hhw/electrical.html topics/topics/hhw/electrical.html

Blood Vessels Arteries – carry blood away from the heart – Thick walls that can withstand the pressure of the blood being pumped – Generally carry oxygen-rich blood – Largest is the aorta which receives blood directly from the heart Veins – carry blood toward the heart – Lower pressure so the veins have valves that prevent backflow of deoxygenated blood – Larges is the inferior vena cava

Blood Vessels Capillaries – Smallest of all the blood vessels – Connect very small arteries and veins – Exchange gases and other substances between cells and the blood – Very thin-walled

Blood Vessels and Homeostasis Can either constrict (narrow) or dilate (get bigger) – These processes are signaled by the autonomic nervous system or the endocrine system – This process controls the amount of blood flowing to different organs

Blood Vessels and Blood Pressure Highest in the arteries and lowest is the veins – When they take your blood pressure they are measuring the pressure in the arteries High blood pressure = Hypertension Can be controlled with diet, exercise and medication pressure/introduction html pressure/introduction html

Pulmonary Circulation

Systemic Circulation

Cardiovascular Disease Atherosclerosis – Build up of plaque on the insides of arteries Debris, cholesterol, and other substances – High fat diet and smoking – Arteries narrow and blood flow is restricted h7ZesKs

Coronary Heart Disease A heart attack occurs when the blood supply to a part of the heart muscle is blocked or shut off Leading cause of death in adults in the US Risks – smoking, lack of exercise, high-fat diet Healthy life style choices reduce risk Video: Heart Attack

Blood A fluid connective tissue Fluid part is called plasma – Contains many dissolved substances and blood cells Red blood cells White blood cells Platelets – s/ws/education/demo-los/blood- rlo/whatisblood.swf s/ws/education/demo-los/blood- rlo/whatisblood.swf

Blood Red blood cells carry oxygen and contain hemoglobin a protein rich in iron that binds with oxygen White blood cells are generally larger than red blood cells, but fewer in number – Part of the body’s defense system Platelets – cell fragments involved in blood clotting – release clotting chemicals at the site of a wound

Blood Type ABO blood groups Rhesus blood type Very important when we look at blood transfusions