The heart and blood Lesson 65 of the biology course of Mova's primary school: 18 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: the lesson at school .
0 Put your hand flat on your chest and you feel it: thump, thump, your heart, a muscle about the size of your fist that never stops working from before you are born. 1 Each beat squeezes blood out through tubes called arteries to every part of you, then the blood comes back through veins, round and round in a loop, carrying oxygen and food and taking waste away. 2 Through a doctor's stethoscope the beat sounds like «lub-dub»: that is not the muscle squeezing but little doors, the valves, snapping shut so the blood can only go one way. 3 Blood is always red, bright red with oxygen and dark red without, even though veins look blue through your skin. 4 The heart grows stronger with exercise like any muscle, and it looks nothing like the heart on a Valentine's card. 5 The heart is a muscle about the size of your fist, in the middle of the chest tipped a little to the left, and it beats about 100,000 times a day. 6 The lub-dub sound is the heart's valves snapping shut: «lub» when the valves between the upper and lower chambers close, «dub» when the valves at the exits close. 7 The pulse is the stretch of an artery each time the heart pumps; you can feel it on the wrist or neck, and it gets faster when you run, because working muscles need more oxygen; a fright makes it faster too, as the body gets ready to run. 8 Blood is a yellowish liquid called plasma carrying red cells, white cells and platelets; a drop the size of a pinhead holds about 5 million red blood cells. 9 Red blood cells carry oxygen using iron-rich haemoglobin, white cells fight germs, and platelets help stop bleeding. 10 Blood is always red: bright red with oxygen and darker red after giving it away; veins only look blue because of how light passes through skin. 11 The heart pumps blood out through arteries, into tiny capillaries and back through veins; its right side pumps blood to the lungs and its left side pumps it to the rest of the body. 12 In 1628 William Harvey showed that the same blood goes round and round the body, when many people still believed blood was made fresh in the liver and used up; but the heart pumps more blood in an hour than food could ever make. 13 When you cut yourself, platelets stick together at the cut and threads of a protein called fibrin form a net that traps blood cells into a clot, which dries into a scab. 14 An adult has about 5 litres of blood, and healthy adults can give about half a litre at a blood donation to help people after accidents, operations and some illnesses. 15 A giraffe's heart weighs about 11 kg and pumps at about twice the pressure of ours to push blood some 2 metres up its neck to the brain, and special blood vessels in its neck stop it fainting when it lifts its head after drinking. 16 The heart gets stronger with exercise and then pumps more blood with each beat, so fit people often have a slower heartbeat at rest. 17 A real heart is shaped more like a rounded cone with big tubes coming out of the top; the Valentine heart is only a drawing. ← previous Cells, bones and musclesnext → Lungs and breathing↑ back to Biology This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/biology/65-the-heart-and-blood/