SESSION 9: SUPPORT SYSTEMS IN ANIMALS 2 KEY CONCEPTS: Structure & function of bone, cartilage, tendons, ligaments Joints fixed, partly movable, synovial Role of bones, joints, ligaments, tendons, muscle in locomotion Muscle antagonistic, myofibrils & contraction Diseases affecting skeleton rickets, osteoporosis, arthritis X-PLANATION: Bone Tissue: Connective tissue rigid matrix Function support & protection Suitability Matrix and osteocytes arranged in concentric rings around the Haversion Canal strength Matrix has white and elastic fibres strength & flexibility Canaliculi allows for communication between the osteocytes in the hard matrix so they can receive nourishment etc. Cartilage: Hyaline strong & rubbery matrix reduces friction at joints White fibrous extremely tough with collagenous fibres to provide padding and act as a shock absorber Yellow elastic elastic fibres provide flexibility in the ears (pinna) and epiglottis Brought to you by Page 1
Tendons : Are connective tissue responsible for attaching skeletal muscle to bone Ligaments : Are tough fibrous connective tissue that attaches one bone to another Brought to you by Page 2
Joints (articulations): Where parts of skeleton meet Allows varying amounts of mobility Classified by structure or function There are three types of joints classified by the amount of movement they allow: Immovable sutures in cranium slightly movable discs between vertebrae freely movable synovial joints Synovial Joints: The joint capsule is an outer sleeve that protects and holds the knee together. The synovial membrane: Lines the capsule and secretes synovial fluid a liquid which lubricates the joint, allowing it to move freely. Hyaline cartilage lines the ends of the bones reducing friction there A typical synovial joint: In ball and socket joints, the rounded end of one bone fits inside a cup-shaped ending on another bone Ball and socket joints allow movement in all directions and also rotation. The most mobile joints in the body are ball and socket joints. Brought to you by Page 3
Examples: Shoulders and hips. Pivot joints have a ring of bone that fits over a bone protrusion, around which it can rotate. These joints only allow rotation. Examples: The joint between the atlas and axis in the neck which allows you to shake your head. Atlas Axis Brought to you by Page 4
Hinge joints as their name suggests only allow forwards and backwards movement. Examples: The knee and elbow. Gliding joints have two flat faces of bone that slide over one another. They allow a tiny bit of movement in all directions. Brought to you by Page 5
Structure of Skeletal Muscle: Brought to you by Page 6
Muscle Contraction: Each muscle fibre consists of smaller units called myofibrils, which consist of protein filaments, myosin and actin During contraction, the actin filaments slide between the myosin filaments The sarcomeres therefore become shorter Each muscle fibre is made up of many sarcomeres So when they all shorten together, the whole muscle fibre contracts Types of Body Movement: Flexion: Bringing two parts of a limb together - bending at the joint. Extension: Moving two parts of a limb away from each other - straightening at the joint. Abduction: Moving limbs away from the centre of the body. Adduction: Moving limbs towards the centre of the body. Circumduction: The movement of a limb around a joint. How muscles work: Muscles can only pull. To make a joint move in two directions, you need two muscles that can pull in opposite directions. Antagonistic muscles are pairs of muscles that work against each other. One muscle contracts (agonist, or prime mover) while the other one relaxes (antagonist) and vice versa. The origin is where the muscle joins the fixed bone. The insertion is where it joins the moving bone. On contraction, the insertion moves towards the origin. Brought to you by Page 7
Diseases Affecting the Skeletal System: Fracture is a break of the bone Simple or Complex fracture Regrowth of bone: Spongy bone forms in first few days Blood vessels regrow and spongy bone hardens Full healing takes 1-2 months Rickets in Children: Disease of children due to a lack of vitamin D. Calcium is not deposited in bones. Bones become soft. Brought to you by Page 8
Bowing of the bones, and other deformities occur: Osteomalacia in Adults: Rickets of adults. Due to a lack of vitamin D. Calcium is not deposited in the bones. Bones become brittle. Osteoporosis: Bone reabsorption is greater than bone deposition. Decline in bone density Due to any of the following: Lack of oestrogen in women. Lack of exercise to stress the bones. Inadequate intake of calcium and phosphorus. Abnormalities of vitamin D metabolism. Loss of muscle mass. Brought to you by Page 9
How much calcium do I need? Children and teenagers between the ages of 9 and 18 should aim for 1,300 mg per day. Each 8-oz glass of milk and each cup of yogurt has about 300 mg of calcium. Adults 19 to 50 years of age should aim for 1,000 mg per day. Adults 50+ need 1,200 mg per day. Osteoarthritis: chronic inflammation of articular cartilage can be normal age-dependent change can also be pathology due to: Age-related changes decrease blood supply trauma Brought to you by Page 10
Gout: Gout is a disease that results from an overload of uric acid in the body. This overload of uric acid leads to the formation of tiny crystals of urate that deposit in tissues of the body, especially the joints. When crystals form in the joints it causes recurring attacks of joint inflammation (arthritis). Chronic gout can also lead to deposits of hard lumps of uric acid in and around the joints and may cause joint destruction, decreased kidney function, and kidney stones. Brought to you by Page 11
X-AMPLE QUESTIONS: Questions 1: Study the diagram of a synovial joint and answer the questions: 1.1 Provide labels for A and B. 1.2 Write the letter of two labels that reduce friction at the joint. 1.3 What is the purpose of ligaments at the joint? Question 2: Study the diagram and answer the questions: Brought to you by Page 12
2.1 Draw a table to indicate the different joints illustrated above and the degree of movement offered by each. Question 3: Classify the following as immovable, slightly movable or freely movable joints. a) b) c) Question 4: Explain how skeletal muscle contracts. Question 5: Discuss the role of bones, muscles and tendons in movement. Brought to you by Page 13