Unit 1: Human Systems The Circulatory System
nourish all cells with oxygen, glucose, amino acids and other nutrients and carry away carbon dioxide, urea and other wastes Purposes
Transport chemical messengers called hormones e.g. testosterone
Helps the immune system battle foreign invaders like bacteria and viruses
Lung Loop: From the heart to the lungs and back Picks up O 2 ; dumps CO 2 Body Loop: From the lungs to the whole body and back Picks up CO 2 ; dumps O 2
The Heart
Your heart is about the size of your fist Located in the centre of your chest right behind the sternum bone
Composed of two parallel pumps Separated by the septum (blood from either side never mixes) The right side pumps blood to the lungs The left side pumps blood to the body. septum
Because the left ventricle pumps to the whole body, it has a much more muscular wall.
Each pump is composed of two chambers An atrium (#4, #7) (welcomes blood to the heart) A ventricle (6 & 5) (pumps blood out of the heart
Valves connect the atria to the ventricles Valves allow blood to flow down only (from atrium to ventricle) The AV valves are supported by strings of tissue called chordae tendinae
Artificial Valves
Blood Flow Through Heart Oxygen-poor blood flows from body to heart in vena cava (8) Blood enters right atrium (7)
Blood Flow Through Heart Atrium (7) contracts and blood flows to right ventricle (6) Valves close
Blood Flow Through Heart Ventricle contracts and blood flows to pulmonary arteries (2) Valves close Blood flows to lungs to release CO 2 & pick up O 2
Blood Flow Through Heart O 2 rich blood flows from lungs through the pulmonary veins (3) to Left atrium (4)
Blood Flow Through Heart Blood flows through the left atrium to the left ventricle (5) when left atrium contracts
Blood Flow Through Heart The left ventricle contracts and blood flows to all parts of the body through the aorta (1) Aorta is the largest artery in body
Heart Beat & Blood Pressure The heart is made up mostly of muscle cells that contract on their own and in unison ( myogenic tissue ) Specialized nerve tissue helps to coordinate the muscle contractions
Electrocardiograms (ECG or EKG) are machines used to monitor the heart
When the ventricles are contracting randomly and ineffectively (like a spasm), it s called ventricular fibrillation. An electric shock from a defibrillator can jolt the heartbeat back into rhythm.
The heart beat has two phases 1) Diastolic: the ventricles are relaxing 2) Systolic: the ventricles are contracting
The force per unit area that blood exerts on the walls of blood vessels Blood pressure is often measured in millimeters of mercury (mm Hg) and is given as systolic over diastolic pressure. For example:
Blood pressure is measured using a sphygmomanometer
An inflatable cuff is placed around the upper arm. Inflate to about a pressure of about 145-160 mm Hg. The flow of blood in the major artery in the arm at this point will be blocked. A stethoscope is used to listen for the sound of the blood in the artery. As the pressure in the cuff is slowly reduced, blood forcing its way through artery will be heard. This FIRST SOUND heard (faint tapping or thumping) is pressure recorded as the systolic value.
When the sound is no longer heard, the pressure value is recorded. This pressure is the diastolic pressure. The sound disappears because the blood no longer has to force its way past an blocked artery.
Normal range for blood pressure: 90 to 135 systolic 50 to 90 diastolic 120/80 is the textbook normal pressure Hypertension is chronic abnormally high pressure above 140/90
Blood Vessels Artery: carries blood away from heart under high pressure Arteries have muscle tissue and elastic fibres Arteriole: small artery that connects an artery to a capillary
Capillaries Capillary bed is a network of capillaries in a particular part of the body Vast networks of thin blood vessels Blood cells move in single file
W = spaces between tissue cells, allows diffusion of material At X, blood high in & At Y, blood high in & Z = cells
Veins Venules connect capillaries to veins Veins carry blood to heart under low pressure Veins have one-way valves to prevent backflow of blood Contractions of muscles also helps move blood up veins in legs back to heart
Wastes & CO 2 diffuse to blood from tissue muscle tissue valve Connective tissue Nutrients & O 2 diffuse from blood to tissue Elastic muscle tissue Elastic connective tissue venule arteriole wide opening surrounded by thin tissue Narrow opening surrounded by thick tissue
Blood Flow in Veins Muscle is relaxed blood is at rest Valve is closed
Blood Flow in Veins Muscle contracts Vein is compressed, the pressure opens the top valve and the blood moves up
Blood Pressure in Vessels
Varicose Veins Varicose veins are visible, protruding veins that appear just under the skin. Varicose veins result from blood pooling in vein due to valves not working properly
Heart Disease Some of the risk factors for heart disease include smoking, high blood pressure, high cholesterol, stress, diabetes, and obesity. Family history can be a factor as well (congenital heart disease)
Coronary arteries supplies the heart with blood, nutrients & oxygen
Atherosclerosis: process in which deposits of fatty substances, cholesterol, cellular waste products, calcium and other substances build up in the inner lining of an artery
Plaque It usually affects large and medium-sized arteries. Some hardening of arteries often occurs when people grow older.
Plaques can grow large enough to significantly reduce the blood flow through an artery. most of the damage occurs when they become fragile and rupture. Plaques that rupture cause blood clots to form that can block blood flow or break off and travel to another part of the body.
Heart Attacks Blockage of the coronary arteries by plaque may cause a heart attack (myocardial infarction) or a fatal rhythm disturbance (sudden cardiac arrest). Blockage of a cerebral blood vessel can cause a stroke
Coronary Bypass Surgery Arteries or veins from elsewhere in the patient's body are grafted to the coronary arteries to bypass narrowings and improve the blood supply to the coronary circulation supplying the myocardium (heart muscle)
Aneurysm An aneurysm is a weak point in a blood vessel wall, most commonly in an artery. Blood pressure tends to push the weakened section of an arterial wall outward, forming a balloon-like projection
Strokes A stroke is an interruption of the blood supply to any part of the brain
Strokes A clot may break off from another place in the brain, or other part of the body, and travel up to the brain to block a smaller artery. This is called an embolism.
Angina Pectoris Angina (sometimes called angina pectoris) occurs when your heart doesn't get as much blood and oxygen as it needs due to a blockage of one or more of the heart's arteries (coronary arteries).
This blockage causes pain in the chest. People who have angina describe the pain as a squeezing, suffocating or burning feeling.