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KS4 Biology B3a / Side 1 Human Skeleton The skeleton has a number of functions: 1. 2. 3. 4. It keeps the shape of the animal It protects vital organs such as the brain, heart, lungs and spinal cord It supports the animal’s weight It provides a framework for the attachment of muscles for movement Using the Internet, CD-Rom’s and books, try to find out: 1. How many bones are in the human body 2. The names of the longest and shortest bones You should be familiar with some of the main bones found in the human skeleton. Label the following diagram using your textbooks. P236 Applin P214 Nelson Sha Tin College Science Department - June 17 KS4 Biology B3b / Side 1 The skeleton is made up of mainly two types of tissue, bone and cartilage. Bone is covered at joints by cartilage. 1. Bone is both hard and flexible o some extent. Bone cells are specially arranged in cylindrical layers. This makes the bone hard. Bone cells are living and they secrete calcium phosphate, which is a mineral that gives the bone hardness. Bone cells are attached to a network of fibres and this gives the bone a degree of flexibility. 2. Cartilage is a rubbery protein secreted by special cartilage cells. It cushions the ends of bones at special areas called joints. It has a smooth, shiny surface. Each type of tissue has its own specific properties. A property describes the physical appearance and chemical nature of the material. Make a copy of the table below and complete using the following statements. Rubbery protein; structural fiber arrangement; smooth; hard minerals (calcium phosphate); shock absorber; structural support; protection of organs Types of Tissue Property Job/Function Bone Cartilage Sha Tin College Science Department - June 17 KS4 Biology B3c / Side 1 Joints One of the main roles of the skeleton is movement. This happens at areas where the bones are linked together. These areas are called joints. Different joints in your body allow you to carry out different types of movement. These moveable joints are called synovial joints and are specially designed to enable easy movement. Examples of synovial joints are: Complete the following table using your textbook as a reference Type of joint Type of movement possible Examples Ball and socket Hinge Sha Tin College Science Department - June 17 KS4 Biology B3c / Side 2 Synovial Joints have special features that allow them to move easily. Using the following words, label the human elbow joint and answer the questions. Synovial fluid, cartilage, humerus, radius, synovial membrane, ligament, ulna What job does each of these do: 1. Synovial membrane 2. Synovial fluid 3. Cartilage covering the ends of the bones Sha Tin College Science Department - June 17 KS4 Biology B3d / Side 1 Connective Tissue There are two kinds of connective tissue that help movement of bones and muscles. 1. Ligaments 2. Tendons Copy and complete the following table Type of tissue Property What it connects Function Inelastic Bone-to-bone Structure and movement of the forearm Muscles move bones. A muscle works by pulling on a bone. To do this the muscle has to contract. Muscles only shorten in length. They do not lengthen. Using your textbook, answer the following questions Q1. What attaches muscles to bone? Q2. Why is this design important? Sha Tin College Science Department - June 17 KS4 Biology B3d / Side 2 The diagrams below show the muscles and bones of a person’s arm in two different positions. Muscles work by contracting. Muscles of ten work in antagonistic pairs. This means when one contracts the other relaxes. Label the following diagrams. Diagram 1 – Arm Extended Diagram 2 – Arm Flexed Sha Tin College Science Department - June 17 KS4 Biology B3d / Side 3 Answer the following questions: 1. What type of joint is shown? 2. Which muscle in diagram 1 contracts to lower the arm? 3. Which muscle in diagram 2 contracts to raise the arm? 4. Why are these muscles known as antagonistic pairs? 5. What role is played by the bones of the skeleton in movements of the arm? Complete the following paragraph using the words provided below. You can use these words once or more than once. Contracts, antagonistic, tendons, levers, ulna, push, biceps, arm, raised, extend, synovial, opposing, pull, elbow, muscles, triceps, forearm, extends Muscle can only they cannot . As a consequence, two muscles are required to operate ( both flex and These are called the biceps and the arranged to have pair. The ) muscles, and the they lies on the front of the humerus and is attached by the forearm is . When it and the is flexed. When the contracts, it pulls the forearm down and elbow. The bones of the arm act like Sha Tin College are actions. They are called an to the shoulder and by elbow. the which are moved pulling on tendons. Science Department - June 17 KS4 Biology B3e / Side 1 Dissection of a Pig’s trotter This dissection will allow you to see a joint in action. Over the top of the joint there are four white tough tendons. Make sure that you can see these. Ask your teacher! 1. Hold the trotter and waggle the toes from left to right. 2. Now bend the toes downwards. You should see a second joint further down, away from the toe. ( Like a knuckle ) 3. Using scissors cut down the length in-between the toes and the second big joint on the front surface of the trotter. Ask if you are not sure! 4. Then cut across this area at right angles to the first cut 5. You should have a cross shape cut 6. Peel back the skin and remove any hair. Cut this piece of skin off 7. You should be able to see the tendons. Sha Tin College Science Department - June 17 KS4 Biology B3e / Side 2 1. Bend the toes down and expose the knuckle. 2. Cut across the knuckle. You will cut through the tendons. 3. Underneath the tendons, close to the bone, you will find a membrane, which is loose. Behind this is fluid. 4. When you cut through the membrane the fluid should trickle out. This is synovial fluid. 5. Cut towards the tow now and you should expose the shiny white surface on the lower part of the joint. Sha Tin College Science Department - June 17 KS4 Biology B3e / Side 3 6. Now cut sideways. You should cut through the joint capsule and ligaments. Don’t worry if you are not sure. Ask your teacher and compare group samples. 7. When the joint is exposed feel the cartilage and press your scissors into the cartilage. 8. Slice a piece of cartilage off and you should see pinkish bone underneath. 9. If time discuss the differences in texture between, muscle, bone, cartilage, tendons and membranes. Think how these differences may be related to their functions. Answer the following questions: 1. Describe what cartilage is like? 2. Why is it necessary to have cartilage in joints? 3. What would happen if two bones rubbed together? 4. What does synovial fluid do? 5. Why are tendons tough and not elastic? 6. What happens when a joint swells up? Sha Tin College Science Department - June 17 KS4 Biology B3f / Side 1 Practical – Using a model arm to investigate the action of the biceps muscle It would be easier to raise the arm if the biceps muscle was attached to the wrist since the further away from the joint, the smaller the force is required to lift the arm. Muscles compensate by being very strong and able to exert large forces over small distances. 1. Copy the title and results table. 2. Hang a 100g weight on the hook at the end of the ‘forearm’ of the model. 3. Attach a spring balance to hook 1. Pull upwards with the spring balance, parallel to the humerus until the forearm is exactly horizontal. Take the reading on the spring balance and fill it on the results table. 4. Repeat with the balance pulling on hooks 2, 3 and 4. 5. Repeat using a different weight. Results table Remember 10N=1Kg Weight in Newtons (N) 1 1 1 1 Sha Tin College Hook Number Distance from elbow (cm) Force exerted by spring balance (N) 1 2 3 4 1 2 3 4 Science Department - June 17 KS4 Biology B3g / Side 1 Supplementary Questions 1. What does the spring balance represent? 2. At which position was the force needed to lift the weight greatest? 3. Which position most closely represents the actual position of the biceps to the radius? 4. Striated muscles are able to exert considerable forces but they cannot shorten by a very large amount. Can you suggest why the biceps is attached in this position? The forces acting on a forearm when lifting a weight can be shown diagrammatically like this: When the arm is horizontal and not moving W x D1 = F x D2 5. What does W stand for? 6. What does F stand for? 7. Use your equation to explain your answer to question 2. 8. Where are the following muscles found in the human body? (a) Voluntary muscle (b) Involuntary muscle (c) Cardiac muscle 9. What are the main differences between these 3 muscles? Sha Tin College Science Department - June 17 KS4 Biology B3h / Side 1 Core questions 1. Cartilage in a synovial joint serves to: (a) Give the body its shape (b) Protect the muscles at the joint (c) Reduce fiction (d) Allow for extra movement 2. The structures which attach muscle to bones are called: (a) Tendons (b) Nerves (c) Ligaments (d) Cartilages 3. When the arm is flexed: (a) The biceps relaxes and the triceps expand (b) The biceps expands and the triceps relax (c) The biceps expands and the triceps contracts (d) The biceps contracts and the triceps relaxes Short answer questions 1. The diagram below shows the elbow joint. 1. Name the parts labeled A to G 2. What is a joint? 3. State two features of a joint which help to reduce friction 4. What do we mean antagonistic muscles? by the term 5. Name and explain how antagonistic muscles can cause the arm to bend at the elbow Sha Tin College Science Department - June 17