Blood: the fluid of lifeIn multicellular organisms the medium is called axtracellular fluid. It contains interstitial fluid, a liquid found in the spaces between cells.Blood is a viscuos fluid with a salty taste which flows inside the vessels of the circulatory system.
Composition of bloodBlood is made up of blood cells suspended in a liquid called blood plasma;Blood plasma: it’s a substance made up of water containig dissolved molecues like minerals, nutrients, waste products, proteins and hormones.
Functions of bloodTransports nutrients and oxygen to all cellsCollects waste products released during cell metabolism.Transports hormones around the bodyHelps to regulate temperatureProtects the body from infectionsThe body uses a lot of mechanisms to prevent blood loss when a blood vessel is brokenThe membranes of red blood cells contain proteins that are responsible for differences in the blood type of different people
Blood vesselsBlood flows around the body in three types of blood vessel:Arteries: They carry the blood away from the heart.Capillaries: Are blood vessels which branch out from the arterioles and are found in every body tissueVeins: Take the blood back to the heart and are formed by capillaries grouped together.
HeartHollow organ made of thick muscle tissue (myocardium) that pumps the blood to make it move around the circulatory system with the function of supply to the cells nutrients and oxygen. http://videos.howstuffw orks.com/health/heart- videos-playlist.htm
Heart’s activityHeart collects blood from the veins, pumps it out into the arteries. The pumping movement (heartbeat) occurs continuously and pushes blood:
Circulation through the blood vesselsVentricular systole pumps the bood to the major arteries, (elastic).So they can:- Dilate when they receive blood, lowering blood pressure.- Contract back to the normal diameter, pushing the blood forwards.
Then it travells to the smaller vessels and the capillaries.- The blood pressure is higher during syshole than turning diastole, so blood pressure alternates between maximun and minimun. When blood reaches the capillaries (flows slowly) pressure is lower and facilities the exchanges.- The blood flows to the venules and veins and returns to the heart.
A double circuitPulmonary circulationThe circuit of the blood has two parts:- Pulmonary circulation: blood starts in the right ventricle and splits into arteries which each lead to a lung. The capillaries surrounds the alveoli; (here gas exchange takes place) they turn into venules, which join to veins which lead to the left atrium. The blood flows to the left ventricle, where systemic circulation begins.
Systemic circulation- Systemic circulation: blood flows along the aorta and splits into arteries, arterioles and then into capillaries. These lead to all body (but no to lungs). Blood provides cell which everything they need, and takes away waste products. Then returns to the right ventricle where pulmonary circulation starts again.