Unit 3.11 Tissues and Organs PDF

Unit 3.11 Tissues and organs Objective Understand that cells work together to form tissues, organs, and whole organisms Cells working together Most of your body is made of muscle, nerves, fat, bone, and blood tissues, which means a collection of similar cells. The cells in each tissue...

Unit 3.11 Tissues and organs Objective Understand that cells work together to form tissues, organs, and whole organisms Cells working together Most of your body is made of muscle, nerves, fat, bone, and blood tissues, which means a collection of similar cells. The cells in each tissue are specialized & different functions. Males have more muscle than females, and less fat. Can change the amount of each tissue in your body by diet and exercise. Eating less makes fat cells smaller, and exercise can make muscle cells bigger. Teams of tissues in Skin Tissues group together to form organs. skin is the biggest organ. Its different tissues help it to protect the rest of your body. 1) Tough surface cells keep micro-organisms out, 2) Nerves let you sense things you should move away from – high or low temperatures, pressure, or pain. 3) Hairs and fat keep you warm, 4) Sweat-producing tissues cool you down 5) Connective tissues hold the rest together, and 6) Blood tissues bring nutrients and oxygen to keep all the other cells alive. The tissues in your heart As an organ like the heart develops, each type of cell moves into the right position and starts doing its job. Scientists want to learn how this happens so they can mimic the process and grow complicated organs like hearts. Stem cells Every cell is formed from existing cells that divide. When your body started to grow, your cells were all the same. They were all stem cells. Stem cells divided, they produced every specialised cell in your body. As your body developed, stem cells differentiated, (turning into the right specialised cells for each tissue) Their development was controlled by clues from their surroundings. These included chemical signals called growth factors made by other cells. How did these growth factors make the cells change? Every cell in your body has a copy of the same set of genes. A muscle cell is different from a nerve cell because they have different genes turned on by the growth factors. Instructions from different genes make cells change their contents and their behaviour. Replacing your cells Your red blood cells only last a few months. They can’t divide to make new ones. New red blood cells are made by stem cells in your bone marrow. Scientists are confident that they will learn to control stem cells. Then they will be able to use them to replace any damaged tissue. Recap Organs have tissues that suit their functions. Each tissue is made of a different type of cell.  Questions 1. Arrange these body parts in order of size: tissue, organ system, cell, and organ. 2. How can you tell whether something is a tissue or an organ? 3. Look at the tissues in skin. Suggest one type of tissue you would expect to find in every other organ. 4. Look at the tissues in the heart. a Name the two tissues that make the heart beat. b Name two other tissues inside the heart. c Name the tissue that protects the heart muscle. 5. Plants have different tissues too. Look at the root on page 45. How many different tissues can you see in it? What functions do the xylem and phloem tissues have? 6. Imagine you could see inside your arm. List all the tissues you would expect to find. Describe how their cells are specialised to suit their roles.