Circulatory System Vessels, Blood & Lymph

Blood Vessels Three types Artery, Veins and capillaries Arteries: Function: carry blood away from heart Thick walls 3 layers: Innermost: smooth epithelial cells Middle: mostly muscle Outermost: flexible connective tissue Pulse: the alternating expansion and relaxation of the artery wall

Veins and Capillaries Vein: Capillary: Function: carries blood to the heart Similar to artery, but walls thinner Closer to the surface of the skin No pulse Has valves to prevent blood backflow Skeletal muscles pump the blood out of the extremities Capillary: Function- materials are exchanged between blood and other cells (oxygen and carbon dioxide) One cell thick

Direction of Blood Flow (review) 1. Heart (pumps blood out and receives blood back) 2. Arteries Right ventricle: blood goes to lungs Left ventricle: blood goes to body 3. Capillaries : Exchange of materials (oxygen & carbon dioxide) 4. Veins: Blood returns to heart.

Blood Components Four types: RBCs, WBCs, platelets & plasma

Blood Components

Red Blood Cells Carry oxygen from lungs to body cells Mostly made of hemoglobin Iron containing molecule that chemically binds oxygen to molecules (iron is red) Produced in bone marrow Has no nuclei Pinched disk shaped

White Blood Cells Body’s disease fighters Larger than red blood cells Have a nucleus For every one WBC: 500-1000 RBC

White Blood Cells Chasing Bacteria

Platelets Cell fragments Helps to form blood clots How a Clot forms: 1. Platelets collect and stick to any site where blood vessels are cut 2. Platelets release a chemical that causes production of the chemical fibrin 3. Fibrin weaves a net of fibers across the wound 4. The net trap blood cells and the clot is formed

Blood Clot Animation

Plasma Liquid part of blood Mostly water Contains dissolved materials: Fats, minerals, proteins, vitamins and glucose Protein gives plasma a yellowish color

Blood Types Four types Percent of Population 40% 11% 4% 45%

Blood & Lymph System Fluid leaks out of the blood into surrounding tissues as it circulates The fluid is called lymph The lymphatic system is a network of vein-like vessels that return the lymph to the blood stream They empty into the veins