Bones and Cartilage

• Long bones consist of two parts referred to as the head (epiphysis) and shaft (diaphysis).
• The shaft's center contains a hollow marrow cavity which is lined by the endosteum, a thin, soft membrane.
• Yellow bone marrow fills the marrow cavity along with fat cells and white blood cells.
• The periosteum, a durable membrane, surrounds the long bone; the heads are lined with articular/hyaline cartilage.
• Spongy bone tissue in the head contains red bone marrow.
• The red bone marrow produces both red and white blood cells.

Cartilage

• Described as a tough, flexible, semitransparent connective tissue.
• The three types of cartilage are known as: hyaline cartilage, white-fibro cartilage, and yellow elastic cartilage.
• Cartilage cells (chondrocytes) are found in lacunae, fluid-filled spaces.
• Cartilage matrix consists mostly of tissue fluid that has a jelly-like substance.
• Discs of cartilaginous tissue are found between the vertebrae, which act as shock absorbers.
• Articular cartilage in joints lessens friction between bones and creates bendable structures.

Bone

• There are two kinds of bone tissue, compact and spongy.
• Compact bone is hard and dense, forming the surface of the bone and the shaft which provides structure and support.
• Spongy bone is softer and lighter, forming the bone heads as well as containing red bone marrow.

Tendons

• Composed of white fibrous connective tissue, made of many unstretchable fibers making the tendon unstretchable.
• Inelasticity of the tendon enables the relaxation and contraction of muscle to be transmitted to the bone resulting in movement.
• Tendons connect muscle to bone.

Ligaments

• Connects bone to bone at the joints.
• Ligaments are composed of yellow, elastic connective tissue containing many elastic fibers, making the ligament flexible.
• The elasticity allows it to stretch to allow for a wide range of movement at the joint.

Joints

• A joint is defined as a place where two or more bones which are joined by ligaments meet.
• The three classes of joints include: Fixed/immovable, Partially/semi-movable, Freely movable/synovial joints.
• Sutures of the skull are an example of fixed/immovable joints.
• The joint between vertebrae are partially/semi-movable joints.
• The ball and socket joints are freely movable/synovial joints.

Synovial Joints

• Hyaline cartilage covers the bone end at the joint to reduce friction; bones held together by ligaments.
• The entire joint is enclosed by a sac called the joint capsule, which is made from a ligament.
• The joint capsule is lined by the synovial membrane, which functions to secrete synovial fluid.
• Synovial fluid prevents friction.

Skeletal Muscle

• Attached to bone through the use of tendons.
• Skeletal muscles are striated and contain light and dark bands.
• Responsible for voluntary actions and usually arranged in pairs that work in opposition of each other.
• When one muscle contracts, the other relaxes, resulting in movement. This is called antagonistic muscles.
• Bicep is found in the front of the arm with the triceps at the back of the arm are examples of antagonistic muscles.
• When the bicep contracts and the triceps relax, the arm raises.
• When the bicep relaxes and the triceps contracts, the arm lowers.

Striated Muscle Structure

• Each muscle is enclosed in a connective tissue called the epimysium, the outer membrane of the bundles of muscle fibers.
• Each bundle of muscle fiber (fascicle) is enclosed by the perimysium.
• The muscle fiber is elongated, cylindrical muscle cell that is surrounded by a membrane called the sarcolemma.
• Each fiber consists of sarcoplasm, many nuclei, mitochondria and thousands of myofibrils.

Myofibril Structure

• Each myofibril is composed of protein filaments called myosin and actin
• Myosin are dark A-bands comprised of thick filaments.
• Actin are light I-bands comprised of thin filaments.
• The protein composition gives skeletal muscles their striated appearance.
• The functional unit of muscle is the sarcomere.

Muscle Contraction

• Nerves transmit messages to the muscle fiber to contract or relax.
• During contraction actin filaments slide inward past the myosin filaments.
• Sliding of actin filaments leads to greater overlap and the shortening of the myofibril, causing entire muscle to contract.

Movement

• Bones have joints enabling various parts of the skeleton to move separately.
• Ligaments hold bones together at joints, ensuring structural integrity and collaborative function.
• Skeletal muscles are attached to bones by way of tendons, which do not stretch.
• The tension created generates a muscle contraction, which passes to in the bone to move.

Skeleton Injuries

• Stretching or tearing of ligaments caused by twisting or stretching in a joint results in a sprain.
• Sprains cause bruising, swelling, pain and limited range of motion.
• Strains are classified as muscles or tendons that have been overstretched or torn. Strains cause pain, weakness, and muscle spasms.
• Cramps develop when a muscle contracts suddenly and painfully.
• Cramps can be caused by imbalances of minerals, dehydration, poor blood circulation, medication or body positioning during sleep.
• Dislocations occur when a ligament is exposed to a sudden impact and the bones at the joint are separated, consequently causing a lot of pain and even nerve damage.
• A fracture is defined as a break in the bone, typically resulting from high-impact forces.
• Casts are often used to immobilize bone and allow healing of fractures.

Rickets

• Disease that affects those whom are children; Inability to absorb calcium.
• Rickets may be caused by malnutrition, lack of sunlight, or inability to absorb Vitamin D.
• Rickets symptoms may include skeletal deformities, stunted growth and/or dental problems.
• Exposure to sunlight and foods rich in Vitamin D can treat rickets.

Osteomalacia

• Adult form of rickets that occurs for adults.
• Caused by defect in the bone-building process.
• Bone pain, muscle weakness and bone fractures are symptoms of osteomalacia.

Osteoporosis

• Primarily affects elderly individuals with a strong correlation in menopausal women.
• Osteoporosis is caused by decrease in overall bone density.
• Weak and porous bones with an increased likelihood of fractures are symptoms of osteoporosis.

Arthritis

• Affects the joints in the human body.
• Cartilage wears away in osteoarthritis.
• Synovial membrane inflammation in rheumatoid arthritis.
• Build-up of uric acid in the blood in gout
• Some symptoms of arthritis include pain, swelling, and stiff joints.

Explore the structure of long bones, including the epiphysis, diaphysis, and marrow cavity. Learn about different types of cartilage such as hyaline, white-fibro, and yellow elastic cartilage. Understand the function of cartilage cells and matrix.