--- title: Cells, bones and muscles — a lesson of Mova's school · trees and pragmatics description: «Cells, bones and muscles», a lesson of the biology course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: Your body is built of cells, tiny living units far too small to see, about 30 trillion of them, each doing its job like workers in a huge city. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/) / Cells, bones and muscles # Cells, bones and muscles Lesson 64 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](https://md.mova.elamur.ai/free/en/school-run/biology/64-cells-bones-and-muscles/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/0/) — Your body is built of cells, tiny living units far too small to see, about 30 trillion of them, each doing its job like workers in a huge city. - [1](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/1/) — Scrape your knee in the playground and watch it over a week: skin cells around the cut divide again and again and crawl across the wound under the scab until new skin covers it. - [2](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/2/) — Inside you stands a frame of 206 bones, and they are not dry and dead like a museum skeleton: living bone is wet, pinkish, full of blood vessels, and grows and mends itself. - [3](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/3/) — Bones cannot move on their own; muscles pull on them, always pulling and never pushing, so they work in pairs, one to bend a joint and one to straighten it. - [4](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/4/) — Some muscles obey you, like the ones you use for star jumps, and some work by themselves day and night, like your heart. - [5](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/5/) — Every living thing is made of cells; under a microscope, cheek cells look like flat shapes with a dark dot in the middle, the nucleus, which holds the cell's instructions. - [6](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/6/) — The human body has about 30 trillion cells of many kinds, such as skin, bone, muscle, nerve and blood cells. - [7](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/7/) — A cut heals because skin cells around it divide and make new cells that crawl across the wound, while a scab protects it from germs. - [8](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/8/) — An adult skeleton has 206 bones; a newborn baby has around 270 to 300, and some of them join together as the child grows. - [9](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/9/) — The smallest bone in the body is the stirrup bone in the middle ear, about 3 millimetres long, and the longest is the thigh bone, the femur. - [10](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/10/) — A smile is made by face muscles, mainly the zygomaticus muscles, which pull the corners of the mouth up and out; more than half of all your bones are in your hands and feet. - [11](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/11/) — Bones show white on an X-ray because the calcium in them stops X-rays more than soft muscle and skin, and a break shows as a dark line; bone cells slowly rebuild a break over several weeks, so a broken arm is kept still in a cast. - [12](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/12/) — Living bone is wet and full of blood vessels and nerves, and the soft marrow inside many bones makes millions of new blood cells every second. - [13](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/13/) — Joints are where bones meet; the knee and elbow are hinge joints that bend one way like a door, while the shoulder and hip are ball-and-socket joints that turn many ways. - [14](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/14/) — Smooth cartilage and a slippery fluid let the ends of bones glide in a joint. - [15](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/15/) — Muscles move bones by pulling, never pushing; the biceps on the front of the arm shortens to bend the elbow, and the triceps at the back pulls to straighten it. - [17](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/17/) — Sore muscles a day after hard exercise come from tiny tears in muscle fibres that the body repairs, making the muscle a little stronger; it is not caused by acid left in the muscle. - [18](https://md.mova.elamur.ai/free/en/corpora/school/biology/64-cells-bones-and-muscles/18/) — You are about 1 centimetre taller in the morning than at bedtime, because the soft discs between the bones of your spine are squashed during the day and fill up again at night; with no gravity squashing them, astronauts in space grow a few centimetres taller. - ← previous: [Microbes: bacteria and viruses, good and bad](https://md.mova.elamur.ai/free/en/corpora/school/biology/63-microbes-bacteria-and-viruses/) - next →: [The heart and blood](https://md.mova.elamur.ai/free/en/corpora/school/biology/65-the-heart-and-blood/) - ↑ back to [Biology](https://md.mova.elamur.ai/free/en/corpora/school/biology/)