The Skeletal System L.I- Understand the important structure and functions of the Skeletal System, and how it allows the body to move. S.C- Students will: - Discuss how each function that benefits the human body - Label bones correctly - Understand the importance of connective tissue in movement - Distinguish between Anatomical positions on the body - Identify the names of anatomical movements when they are performed Skeletal System The skeletal system is made up of 206 bones and encompasses all of the bones, every joint and corresponding ligaments. The 5 main functions include: 1. Body movement (the most important function to understand in physical education)bones are connected to muscles to contract and allow movement to occur 2. Framework- The skeleton provides a solid framework for the body and helps battle the forces of gravity. Everyone has a solid skeleton, but the differences in people’s posture indicate the interdependence of the skeletal and muscular systems in maintaining correct posture. 3. Protection- The strong protective skeletal layer provides protection for many vital body organs. This is particularly evident when the rib cage or skull is examined, naturally enclosing shell effectively protects the heart and lungs from all but the most traumatic of injuries. 4. Mineral storage- Bone tissue efficiently stores a number of minerals that are important for health. Calcium, phosphorus, sodium and potassium all contribute to the health and maintenance of bone tissue as well as carrying out other roles in the body. Calcium also assists with muscular activity. 5. Production of red blood cells- Essential production of new red blood cells occurs within the cavity of long bones. Production levels are high during growth years, diminishing as age increases and the need for high rates of red blood cells decreases. Such cells are essential for oxygen transportation throughout the body. Major bones in the Skeletal System Types of bones There are five types of bones in the human body, distinguished by their shape. 1. Short bones (figure 2.5a) are roughly cubical, with the same width and length; for example, the carpals of the wrist and the tarsals of the foot. 2. Long bones (figure 2.5b) are longer than they are wide, and they have a hollow shaft containing marrow (figure 2.3); for example, femur, phalanges and humerus. 3. Sesamoid bones (figure 2.5c) are small bones developed in tendons around some joints; for example, the patella at the knee joint. 4. Flat bones (figure 2.5d) provide flat areas for muscle attachment and usually enclose cavities for protecting organs; for example, scapula, ribs, sternum and skull. 5. Irregular bones (figure 2.5e) have no regular shape characteristics; for example, vertebrae and bones of the face. Vertebral Column The vertebral column (also called the spine) provides the central structure for the maintenance of good posture. If a person maintains the correct levels of strength and flexibility in all the muscle groups that connect with the vertebral column, then they are likely to avoid postural problems. The vertebral column has some special features: 1. Each vertebra has a hollow centre through which travels the spinal cord that controls most conscious movement within the body. In this way the cord is protected (image). 2. The vertebrae increase in size as they descend from the cervical to the lumbar region (image). This helps them support the weight of the body. 3. Movement between two vertebrae is very limited. But the range of movement of the vertebral column as a whole is great, allowing bending and twisting. 4. Intervertebral discs separate each of the vertebrae in the cervical, thoracic and lumbar regions. They absorb shock caused by movement and allow the vertebral column to bend and twist. Joint Classification The skeleton has three major joint types. These joints are classified by how the bones are joined together and by the movement that each joint permits. 1. Fibrous (immoveable) joints offer no movement. Examples include the skull, pelvis, sacrum and sternum. 2. Cartilaginous (slightly moveable) joints are joined by cartilage and allow small movements. Examples include the vertebrae and where the ribs join the sternum. 3. Synovial (freely moveable) joints offer a full range of movement and move freely in at least one direction. Examples include the knee or shoulder. Connective Tissue Cartilage Ligaments Cartilage is a smooth, slightly elastic tissue found in various forms within the body: Ligaments cross over joints, joining bone to bone. Their slight elasticity allows small movement from the bones of the joint. hyaline cartilage coats the ends of the bones in synovial joints The main function of ligaments is to provide stability at the joint, preventing dislocation. discs of cartilage separate the vertebrae of the spine (figure 2.8) the ribs attach to the sternum via cartilage the hard part of the ear and the tip of the nose are also cartilage. If ligaments are seriously damaged in an accident, they may not be able to repair themselves and may require surgery. Tendons Tendons are inelastic and very strong, allowing movement by helping muscles pull through the joint and on the bones. The biceps muscle is an example of a muscle that works through two joints. It has two tendinous origins at the scapula (allowing the humerus to flex away from the body), and the tendinous insertion into the radius in the forearm allows the forearm to flex upwards towards the humerus. Anatomical positions and terms of reference Term Definition Example Superior Towards the head or upper part of the body The cranium is superior to the sternum. Inferior Towards the feet or lower part of the body The tarsals are inferior to the femur. Anterior Towards the front of the body The patella is on the anterior side of the body. Posterior Towards the back of the body The scapula is posterior to the sternum. Medial Towards the midline of the body The sternum is medial to the rib cage. Lateral Towards the outer side of the body The fibula is lateral to the tibia. Proximal Closer to the trunk of the body The femur is proximal to the patella. Distal Further away from the The phalanges are distal to the trunk of the body humerus. Superficial Towards the surface of the body The rib cage is superficial to the heart. Deep Towards the inner part of the body The liver is deep to the skin. Prone Face down Lying on the stomach Supine Face up Lying on the back Anatomical Movements Anatomical movement Definition Example Flexion Decrease in the angle of the joint Bending the elbow or knee Extension Increase in the angle of the joint Straightening the elbow or knee Abduction Movement of a body part away from the midline of the body Lifting arm out to side (out phase of star jump) Adduction Movement of a body part back towards the Returning arm into body or towards midline of the body midline of the body Circumduction Movement of the end of the bone in a circular motion Movement of a body part around a central axis Rotation of the hand so that the thumb moves in towards the body Drawing a circle in the air with straight arm Turning head from side to side Supination Rotation of the hand so that the thumb moves away from the body Palm facing up Eversion Movement of the sole of the foot away from Twisting ankle out the midline Inversion Movement of the sole of the foot towards the midline Dorsi flexion Decrease in the angle of the joint between Raising toes upwards the foot and lower leg Plantar flexion Increase in the angle of the joint between the foot and the lower leg Pointing toes to the ground Elevation Movement of the shoulders towards the head Movement of the shoulders away from the head Shrugging shoulders Rotation Pronation Depression Palm facing down Twisting ankle in Returning shoulders to normal position Muscular system L.I- Understand the important structure and functions of the Muscular System, and how it allows the body to move with the help of the Skeletal system. S.C- Students will: - Discuss important features of muscles - Label muscles correctly - Differentiate between the 2 kinds of muscles the body has - Distinguish between muscle fibre types 1, 2A and 2B - Identify the importance of muscles when generating force Features of muscles Most muscles have certain common features: Nervous control — nerve stimuli control muscle action. Contractility — muscles contract and become thicker. Extensibility — muscles have the capacity to stretch when a force is applied. Elasticity — muscles can return to their original size and shape once stretched. Atrophy — muscles can decrease in size (waste) as a result of injury, illness or lack of exercise. Hypertrophy — muscles can increase in size (growth) with an increase in activity. Types of muscle Muscles can be classified into three main groups: 1. Smooth- mainly in walls of organs (digestive tract) Smooth muscle 2. Cardiac- only found in the heart to push blood into arteries all of the body 3. Skeletal- allow movement to occur and are attached to bones Cardiac Muscle Skeletal Muscle Major Skeletal Muscles Muscle fibre types Type 1 Type 2A and 2B “2A- Fast-twitch Oxidative” contain an large amount of myoglobin, and large numbers of mitochondria and blood capillaries pinkish in colour and have a very high capacity for generating ATP by oxidative metabolic processes “slow-twitch Oxidative” split ATP at a very rapid rate, have a fast contraction velocity contain large amounts of myoglobin, and large numbers of mitochondria and blood capillaries are relatively resistant to fatigue red, split ATP (adenosine triphosphate, the basic source of energy for muscle cell metabolism and movement) at a slow rate and have a slow contraction velocity are very resistant to fatigue, and have a high capacity to generate ATP by oxidative metabolic processes are suited to low-intensity, longer duration, aerobic work are classed as partially aerobic and are suited to events that require both aerobic and anaerobic elements. “2B- Fast-twitch Glycolytic” contain a low myoglobin content, relatively few mitochondria and blood capillaries, and large amounts of glycogen white and are geared to generate ATP by anaerobic metabolic processes 50fatigue easily split ATP at a fast rate, and have a fast contraction velocity suited to high-intensity, short-duration, anaerobic work. Muscle fibre types Type 1 Type 2A and 2B Characterisatic Slow-twitch Fast-twitch oxidative Fast-twitch glycolytic Also known as Type 1 Type 2A Type 2B Colour Used for Red Aerobic Pinkish Anaerobic (long-term) White Anaerobic (short-term) Fibre size Motor neuron size Small Small Medium Large Large Very large Resistance to fatigue High Medium Low Force production Low Medium High Speed of contraction Slow Fast Very fast Hypertrophy potential Low High High Mitochondrial density High High Low Capillary density High High Low Myoglobin content High High Low Oxidative capacity High Medium Low Glycolytic capacity Low High High Major fuel Triglycerides Creatine phosphate/glycogen Creatine phosphate/glycogen Muscle action Skeletal muscles create movement by pulling on the bones to which they are attached. They have a more rigid attachment to a bone at one end, and they are attached across a joint to another bone that is usually more moveable. 1. Origin 2. Insertion 3. Contraction Force production The development of muscle force is dependent on a number of factors: number and type of motor units activated size of the muscle initial length of muscle that is being activated angle of the joint the muscle’s speed of action. More force can be generated with more motor units activated. Fast-twitch (FT) motor units produce more force due to each FT motor unit having a larger cell body and more axons and innervates from 300 to 800 muscle fibres. Conversely, a slow-twitch motor unit has a small cell body and innervates from 10 to 180 muscle fibres. Large muscles have more muscle fibres so can produce more force than smaller muscles. For a strong muscular contraction, there must be a strong enough nerve impulse to innervate (stimulate) the muscle fibres.
