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Skeletal and Muscular Systems Mr. Fox’s 7th Grade Science Class. The Skeletal System • A human adult has 206 bones. When you are born, you have between 275 and 305 bones in your body. • Each bone shares the function of the system. Functions • 1. provide shape and support • 2. enables you to move • 3. protection of internal organs • 4. produce blood cells • 5. stores materials for body functions Remember!! • Bone is living material • It contains blood vessels and nerves, just like other parts of your body. Parts of the bone • Bone Marrow – soft tissue in the center cavity of the skeletal system. • Cartilage – flexible, elastic, connective tissue found in the joints • Cushions the joints, and keeps bones from rubbing together. Developing Bone • Ossification – the process of forming bones. • Osteoblasts form the bones • Osteocystes maintain the cellular activity of the bone. • Osteoclasts break down bones. Types of Joints • 1. Immovable Joint (Fixed Joint) – allow little if any movement. Joints in your skull, ribs. Types of Joints • Ball and Socket - allows the greatest range of motion. Nearly 360 degrees. • Shoulder and Hip Joints. Types of Joints • Hinge Joint – Like a door hinge, forward and backward movement. • Knee and Elbow Types of Joints • Pivot (radial) Joint – allows one bone to rotate around the other. • Lower arm, Lower leg Types of Joints • Sliding Joint – allows one or more bones to slide over another. • Wrist, Ankle Bone Problems • Dislocation – when a bone moves out of place. Usually very painful, but easily fixed. Bone Problems • Break/Fracture – when bones break in places they shouldn’t. • Always heal back larger so they are stronger. Bone Problems • Osteoporosis – When bones start losing their density, from a lack of calcium. • Happens more in woman • Arthritis – A generic term describing the inflammation of the joints. Pain, stiffness, swelling of the joints. Muscles • It takes 42 muscles to frown, only 16 to smile. Smile more and save energy. • Your body has over 600 muscles, nearly 3 times as many as its bones. Muscle Action • Two types of muscle action: • Involuntary – muscles you cannot control, heartbeat, breathing, digestion • Voluntary - muscles you control, smiling moving Types of Muscles • Skeletal Muscles - muscles that are attached to your bones, provide the force needed to move. • Striated fibers that tire quickly. • Work in pairs to move bones, can only pull or contract. Skeletal Muscle Types of Skeletal Muscle • Ligament – skeletal muscles that hold bones together at joints. • Tendons – skeletal muscles that connect muscle to bone. • Regular Muscle – Muscles that do most of the work in moving the bones. Types of Muscle • Smooth Muscle – often line the interior of body organs, stomach, intestines, not striated, are involuntary, do not tire easily. Types of Muscle • Cardiac Muscle – Heart muscle, striated but involuntary, does not tire! Muscle at work • Muscles can only contract, not extend. • Must work in pairs. • One muscle contracts the other muscle in the pair returns to its original state. How on the muscle level • A muscle contracts when ATP causes thin filaments (actin) in muscles fibers to slide over thick filaments (myosin). myosin actin actin myosin Skin!!! The Skin • Everyone… your epidermis is showing! • The skin is the largest organ in the body! And the most visible. Functions of the skin • Major functions of the skin: • Reduces water loss • Protection from injury and infection • Regulates body temp. • Eliminates waste • Sense the environment • Produces vitamin D from sunlight Structure of the Skin • Epidermis – top layers of skin, no blood vessels or nerves, surface cells are dead, skin pigment (melanin) is found in the lower epidermis • Dermis – lower layers of skin, contains blood vessels, nerves, sweat glands, hair follicles, oil glands, and hair. Skin Diseases • Eczema – a disease of reoccurring skin rashes and dryness. (very common not deadly) • Acne – (PIMPLES!!!!!) More or less the changed of the hair follicles and sebaceous glands cause it. • Tinea pedis – Athlete’s Foot. Is typically caused by mold! Up to 15% of the U.S. population may have tinea pedis. Cancer • Skin cancer – one of the many forms of cancer, this one caused from over exposure to UV light, and many other things. Homework • Finish the chapter one review. Get ready for a bone and muscle test next week. • Laury is awesome