Chapter 30.1 The Circulatory

Functions of the Circulatory System: supplies the trillion cells in your body with nutrients & oxygen transports hormones throughout your body and carries wastes away from cells repairs tissues and protects the body from infection removes carbon dioxide

Main Organs: 1. Blood - connective tissue made of cells and liquid. 55% is plasma / 45% mostly blood cells.

Kinds of blood cells: red blood cell - also called erythrocytes – carry oxygen from lungs to all tissues of the body. Each cell (there are 25 trillion in the average person) has hemoglobin - protein & iron that temporarily stores oxygen for delivery to cells. white blood cell - also called leukocytes, responsible for fighting infection and preventing cancer growth. Normally there are 4-11,000 in one drop of blood - but when sick they will increase. platelet - allows for blood clotting. They originate in bone marrow.

2. Heart - multi-chambered, muscular organ, responsible for overall flow of blood to tissues throughout the body.

3. Blood Vessels a. Capillaries - narrow microscopic vessels that carry blood between an artery and a vein, allowing for the exchange of substances between the blood and interstitial fluid.

c. Veins - vessels that return blood to the heart b. Arteries - vessels that carry blood away from the heart to other parts of the body. c. Veins - vessels that return blood to the heart

Why does blood sometimes look blue underneath the skin? Answer: Blood is always red. How dark a red depends on how much oxygen is inside it. The veins and such looks blue through our skin due to the absorption of light

Other facts: In one minute all the blood in your body will have circulated. Your body contains 5 liters of blood. Blood removes waste products from the tissues and delivers them to the organs of the excretory system. kidney removes nitrogenous wastes liver removes many toxic compounds from the blood.