THE MUSCULOSKELETAL SYSTEM The musculoskeletal system generates movement, supports the body and protects the organs. It consists of the skeletal system and the muscular system. 1. THE SKELETAL SYSTEM The skeletal system is made up of bones, to which muscles are attached, as well as cartilage. This system protects organs such as the spinal cord and the brain, as well as supporting the body and generating movement. 1.1. BONES Bones are hard structures made up of a protein called collagen, as well as phosphorus and calcium salts. They consist of two types of bone tissue: compact and spongy. Some bones have projections called apophyses which are connected to tendons and ligaments. Types of bones: 1. Long bones: are elongated in shape. They are found in the limbs (f.ex. the femur). 2. Short bones: are small in size. The vertebrae and the wrist bones are examples of short bones. 3. Flat bones: are plate-like. Examples of flat bones are the bones of the skull. Long bones Short bones Flat bones Structure of a long bone: Red Bonne Marrow Epiphysis (spongy bone tissue). It contains the red bone marrow. Diaphysis (compact bone tissue) Endosteum: a layer of connective tissue that covers the internal cavity of the diaphysis. Periosteum: a layer of connective tissue that surrounds the bone. Bones have several functions: To provide a framework that supports the body to provide the structures to which muscles are attached to protect organs, such as the brain and spinal cord to contain the red bone marrow that forms blood cells to store calcium, which is released into the blood if required. 1.2. CARTILAGE Cartilage is softer than bone. It is formed of cartilaginous tissue. Cartilage is found in the front part of the nose, in the ears, between the vertebrae (intervertebral discs) and in the joints. Cartilage also forms the embryonic skeleton. JOINTS Joints are structures that connect two bones. There are three types of joint: immovable, slightly movable and movable. Classification depends on the movement the joint allows. (1) IMMOVABLE JOINTS Immovable joints are also known as sutures. They do not allow movement between the bones they connect. The bones of the skull are an example of bones that have immovable joints between them. (2) SLIGHTLY MOVABLE JOINTS They allow small movements between the bones they connect. This type of joint is found between the vertebrae in the spinal column. (3) MOVABLE JOINTS Movable joints allow a large range of movement between the bones. Joints of this type include the knee, shoulder and elbow. Movable joints usually consist of the following parts: Ligaments. These are groups of fibres that connect the bones in the joint. Cartilage. This is tissue that covers the bone surface and prevents friction between the bones. Ligaments Cartilage 2. THE MUSCULAR SYSTEM The muscular system consists of the skeletal muscles, the cardiac muscles and smooth muscles. The skeletal muscles are made up of striated muscle tissue which contains long cells with several muscle fibres. Skeletal muscles have the following structure: Muscle Muscle fibres Muscle fascicle s Bone Tendon A tendon is a strong structure made up of fibrous connective tissue that connects the muscle to the bone. They transmit the muscle contraction to the bone, generating movement. TYPES OF MUSCLE The human body has different types of skeletal muscle. These muscles allow movement and give support to different parts of the organism. 1. FUSIFORM Fusiform muscles are long and spindle-shaped. They are related to movement. Examples of fusiform muscles are the triceps and biceps in the arm. 2. FLAT: Flat muscles are square or fan-shaped. They cover organs. Examples include the pectoralis major in the chest, and the rectus abdominis found in the trunk. 3. CIRCULAR: Circular muscles are ring-shaped. They open or close ducts or cavities. Examples of circular muscles include the orbicularis oris (lips), and the orbicularis oculi (eye). MUSCLE CONTRACTION The striated muscle tissue that forms muscles contracts quickly and voluntarily. To do this, it requires calcium, energy and oxygen. Certain stimuli cause muscle fibres to shorten (contract). The muscles lengthen (relax) when the stimuli stop. This generates movement. To flex the forearm, the biceps contracts and the triceps relaxes. To extend the forearm, the triceps contracts and the biceps relaxes.
