Circulatory System

The Three Parts Heart –4 chambers –Made of cardiac muscle –Keeps oxygenated blood separate from oxygen poor blood Blood Vessels –Capillaries, Veins, Arteries –Most are surrounded by smooth muscle Blood –Red Blood Cells (RBC), White Blood Cells (WBC), Platelets

Blood Human Body contains 4 to 6 liters of blood (8% of total mass) 45% Solids (RBC, WBC & Platelets) 55% Plasma (90 – 92% water, dissolved nutrients, some proteins) What color is your blood? –Dark Red – Lacking oxygen –Bright Red – Full of oxygen

RBC Red Blood Cells –Job is to carry oxygen to cells and carbon dioxide away from the cells –Hemoglobin is the molecule within the cell that actually carries the oxygen & CO 2 –Hemoglobin is mostly made of IRON –RBC are saucer shaped, looks like a donut with skin on it –Fairly small and many of them –Made in the red bone marrow –Are around for about 120 days, then taken out by the liver and spleen

WBC White Blood Cells –Larger than red blood cells & a lot less of them –Include macrophages, B cells & T cells –Job is to fight off invaders such as bacteria, virus & fungus –Made in the bone marrow –Can move out of the blood vessels into the tissues & lymphatic system

Platelets –Clumps up to form clots –Helps stop bleeding –Just fragments of cells –Also formed in the bone marrow

Blood Vessels Carries blood around the body Three main types: –Arteries –Veins –Capillaries

Arteries Large vessels Carry blood away from the heart Mostly carries oxygen rich blood, except ONE –The exception is the Pulmonary Artery They have thick walls to handle all of the pressure produced by the heart All arteries branch off of the AORTA, the big U-Shaped vessel coming out of the heart. The first arteries off of the AORTA are the CORONARY arteries (they feed the heart) The second arteries that branch off are the CAROTID arteries (they feed the brain)

Veins Large vessels Carries oxygen poor blood toward the heart, except ONE –The pulmonary vein Thinner walls than the arteries Don’t have the direct pressure from the heart Have to fight the effects of gravity Use one way valves to keep the from flowing backwards

Capillaries Small & Thin Only one blood cell can fit through at a time One cell layer thick Allows for the exchange of oxygen & carbon dioxide & all nutrients and waste products

Heart Muscle is covered inside by a layer of smooth tissue called epithelium The heart has four chambers: 2 atrium & 2 Ventricles The atriums receive blood coming in The ventricles pump blood out Pacemaker for the heart is found in the right atrium