The Circulatory System

Transcription

1 The Circulatory System Single-celled organisms do not need a circulatory system. They are in direct contact with their environment, so transport of materials occurs by diffusion and osmosis. Larger organisms need a circulatory system, since their cells are not all in contact with their environment. The human circulatory system consists of the heart, blood vessels and the blood that flows through them. The Heart Your heart is the muscle that moves blood through your system. ***The heart contracts about 72_times per minute, pumping 70 ml of blood per contraction. Dividing the right and left sides of the heart is a septum. This prevents the mixing of oxygen- rich and oxygen- poor blood. The human heart has 4 chambers 2 atria (upper chambers) and 2 ventricles (lower chambers). Vena cava aorta Pulmonary artery valve Pulmonary vein valve Right atrium Left ventricle Left atrium valve Right ventricle Vena cava septum

2 The right side of the heart receives blood from the body and carries it to the lungs -- to replenish its oxygen level. In the lungs, CO2 diffuses out, oxygen diffuses in. This oxygen- rich blood then leaves from the left side of the heart and travels to the body. Blood Vessels There are 3 types of blood vessels: 1. Arteries 2. Veins 3. Capillaries Arteries: large vessels that carry blood AWAY from the heart. Have thick walls that can withstand the pressure from the heart s contractions. Veins: carry blood TOWARD the heart. Have thinner walls than arteries, and need the help of skeletal muscles to move blood to the heart. Veins contain valves to prevent blood from flowing backward. Capillaries: the smallest vessels only 1 cell thick! They are the only vessels that allow for transport of materials into and out of body tissues! Comes From Goes To Material Comes From Goes To Water Digestive tract All cells Nutrients Digestive tract All cells Oxygen Lungs All cells Waste ALL cells Excretory organs Hormones Endocrine glands Target cells Blood Pressure

3 When the heart contracts, it forces blood through the arteries at high pressure. When the heart relaxes, the pressure decreases a little. Systolic pressure is measured when the ventricles contract. Diastolic pressure is when the ventricles are relaxed. Normal, healthy blood pressure is 120/80. Diseases/Disorders Hypertension: (high _blood pressure ) causes the heart to work harder than necessary to pump blood to body. This can weaken the heart muscle and blood vessels and may increase the risk of heart attack or stroke. Atherosclerosis: fatty deposits build up on the inner walls of arteries. If an artery becomes completely blocked, it can cut off the blood supply to the heart. Without oxygen, heart cells will die -- if enough are affected and heart muscle is damaged, you have a heart attack. Stroke: Blood clots that form in the arteries can break free and travel throughout the body. If they get stuck in one of the vessels of the brain, any brain cells supplied by that vessel will die from lack of oxygen and brain function in that area will be lost. Depending on the affected area, strokes may cause paralysis, loss of speech or death. Blood The human body contains 4-6 liters of blood, about _8 % of body mass. 45% of blood is cells, the other 55% is a fluid called plasma.

4 Plasma is about 90% water and 10% gases, nutrients, enzymes, hormones, wastes and proteins. Blood Cells: red blood cells, white blood cells and platelets Red blood cells ( erythrocytes ) carry oxygen to body cells using hemoglobin. Once mature, red blood cells lose their nuclei -- and live for 120 days. Old red blood cells are broken down in the liver and spleen. White blood cells ( leukocytes ) do have nuclei and can live for months or years. There are several different types but they all fight infections or pathogens that invade the body. Platelets: help blood to clot when the body is injured.

5 The Respiratory System *** Remember cellular Respiration is NOT the same thing as breathing. The basic function performed by the human respiratory system is the exchange of oxygen and carbon dioxide between the blood, air and body tissues. trachea bronchi bronchioles alveoli diaphragm The Path of Air Your diaphragm pulls down, causing the lungs to expand. Air enters through mouth or nose to a tube at the back of the throat called the pharynx (carries both food and air ) Food goes to the esophagus -- air goes to the trachea. A flap of skin called the epiglottis prevents food from entering the lungs. From the trachea, air passes into two bronchi -- one to each lung. The bronchi divide into smaller bronchioles, and then finally into microscopic sacs called alveoli. Alveoli are surrounded by capillaries, which are the site of gas exchange!

6 CO2 C C C Remember: diffusion moves from high to low! CO2 is higher in the blood and moves to the lungs. O2 is higher in the lungs and moves to the blood. When the diaphragm relaxes, the lungs compress and force air out. Interactions: All systems of the body need oxygen and need to eliminate carbon dioxide. Your lungs are in direct contact with the environment, so they are protected by the immune system.

7 Disorders: Emphysema: lungs and alveoli lose elasticity so they can t exchange and exchange as much O2/CO2. Asthma: bronchi spasm or inflame ( swell ) so that air cannot enter lungs What s in Tobacco Smoke? Nicotine is a stimulant that increases blood pressure and heart rate. Carbon monoxide is a poisonous gas that blocks the ability of hemoglobin to carry oxygen. Tar has a number of known carcinogens (cause cancer ) Normal, healthy lungs have cilia -- little hairs that sweep out foreign particles. When inhaled, cigarette smoke paralyzes the cilia in the lungs causing the inhaled particles to stick to the walls of your respiratory tract or enter the lungs. This will cause the lining of the respiratory tract to swell and reduce the air entering the alveoli. Smoking can cause: 1. Chronic bronchitis : bronchi become swollen and clogged with mucus. 2. Emphysema: loss of elasticity makes breathing difficult 3. Lung cancer : uncontrolled mitosis of cells in the lungs. Lung cancer can spread rapidly if cancer cells enter the capillaries surrounding the alveoli -- can travel to anywhere in the body