Skeletal System, Muscular System, and Integumentary System Chapter 37 Skeletal System Structures Bones Tendons Ligaments Cartilage Skeletal System Functions: Provides framework for body tissues. Protect internal organs including the heart, lung, and brain. Efficient movement. Produces blood cells. Storehouse for minerals, including calcium and phosphorus. Skeletal System 206 bones in a human body Two parts – Axial skeleton—skull, vertebral column, ribs, and sternum – Appendicular Skeleton— arms, legs, shoulders, pelvic girdle (hip) Bone Structure—pg 851 Osteoblast—bone cell Compact Bone—layer of hard bone surrounding every bone Spongy Bone—less dense bone filled with holes and spaces Bone Marrow—fills the center cavity of a bone. Produces blood cells. Found in long bones of the arms and legs. Joints pg 854 Joints—where two bones meet. – Ball and socket joint—shoulder and hip – Pivot joint—top of spine (turning of head) – Hinge joint—Elbows, knuckles of fingers and toes – Gliding joint—wrists and ankles – Saddle joint—base of thumbs Arthritis—joint disease caused by inflammation of the joints Ligaments—tough connective tissue that connects bone to bone. Tendons—tough connective tissue that connects muscle to bone. Bone Growth Bones grow in both length and diameter. Growth in length occurs at the ends of the bones and growth in diameter occurs on the outer surface of the bone. By the age of 20, 98% of the growth of the skeleton is complete. Homeostasis, Aging, and the Skeletal System Remodel themselves—some cells deposit calcium while other remove it. This remodeling of the skeleton occurs as you age, gain or lose weight, or change your level of activity. This process keeps the bones from becoming thick and heavy. Bone cells are involved in the process of repair when a bone is broken. The composition of bone changes as a person ages. Bones tend to become more brittle as their composition changes with age. Osteoporosis is most common in older women because they produce lesser amounts of a hormone that aids in bone formation. Muscular System Structure and Function: Structure: – Skeletal muscle – Smooth muscle – Cardiac muscle Function: – Locomotion – Circulate blood – Move food through the digestive system Three Types of Muscles Smooth Muscle—found in internal organs and blood vessels. The most common function of smooth muscle is to squeeze, exerting pressure on the space inside the tube or organ it surrounds (ex digestive tract and reproductive tract). These contractions are not under conscious control, so smooth muscle is an example of an involuntary muscle. Cardiac Muscle—is found only in the heart, and is adapted to conduct the electrical impulses necessary for rhythmic contraction. Example of an involuntary muscle. Skeletal Muscle—is the type of muscle that is attached to bone and moves the skeleton. Makes up the largest mass of muscle in the body. A muscle that contracts under conscious control is called voluntary muscle. Skeletal Muscle Contraction pg 858-859 When a muscle contracts, the bones are pulled by tendons. Each cylindrical muscle fiber is made up of smaller fibers called myofibrils. Myofibrils are composed of even smaller protein filaments. Filaments can be either thick or thin. The thick filaments are made of the protein myosin, and the thin filaments are made of the protein actin. The arrangement of myosin and actin gives skeletal muscle its striated appearance. Each section of a myofibril is called a sarcomere and is the functional unit of muscle. Sliding filament theory—states that the actin filaments within the sarcomere slide toward one another during contraction. The myosin filaments do not move. Muscle Strength and Exercise Muscle strength depends on the thickness of fibers and many of them contract at one time. Regular exercise stresses muscle fibers slightly, and to compensate for this added workload, the fibers increase in size. The number of fibers in a muscle is fixed before we are born. Integumentary System Skin—largest organ Hair Nails Sweat glands Oil glands Integumentary System Structure and Function of the Skin Epidermis—the outer layer of skin composed of both dead and living cells The outer dead epidermal cells contain a protein called keratin that helps water proof and protect the living cell layers underneath. The inner living layer contains melanin a cell pigment that colors the skin and protects the cells from damage by solar radiation. Fingerprints Scalp Slide Integumentary System Structure and Function of the Skin Dermis—the inner, thicker layer of skin Contains: blood vessels, nerves, nerve endings, sweat glands, and oil glands. Fat deposits that lie underneath the dermis in the subcutaneous layer cushion the body, insulate and help the body retain heat, and store food for long periods of time. Hair grows out of narrow cavities in the dermis called hair follicles. As hair follicles develop, they are supplied with blood vessels and nerves and become attached to muscle tissue. Skin Helping Maintain Homeostasis regulate body temperature – hot blood vessels dilate heat released – cold blood vessels constrict heat conserved Glands in the dermis produce sweat in response to increases in body temperature. As sweat evaporates, the body cools. Protective layer to underlying tissues--Skin protects the body from physical and chemical damage and from the invasion of microbes. Sense organ—nerves cells in the dermis receive stimuli from the environment and relay information about pressure, pain, and temperature. Skin Injury and Restoration of Homeostasis Cuts – When small injuries occur to the epidermis, such as a scrape, epidermal cells divide by mitosis and fill in the gap left by the abrasion. – Larger cuts—blood flows out of the wound until a clot forms, scab forms, skin cells beneath the scab begin to multiply and fill in the gap. Burns – 1st degree—redness and mild pain and involve the death of epidermal cells. – 2nd degree—involves damage to skin cells of the dermis and can result in blistering and scarring. – 3rd degree—destroy the epidermis and dermis, skin function is lost and re-growth of the skin is slow with much scarring. Aging – increase in wrinkles and sagging. Wrinkles appear because the skin becomes less elastic with age. The oil glands produce less oil and the skin becomes drier. Super Human Facts The skeleton of an average 160 pound body weighs about 29 pounds. The skin is your largest organ. Weighing about 6 pounds. The average adult stands 0.4 inch taller in the morning than in the evening, because the cartilage in the spine compresses during the day. The strongest bone in the body is the thigh bone. The average person sheds about 1 and a half pounds of skin each year. There are 22 bones in the adult human skull. There are 230 joints in the human body. No one truly has double joints. Man has tiny bones once meant for a tail and unworkable muscles once meant to move his ears. The bones in the human body are comprised of 22 percent water. There are approximately 250,000 sweat glands in your feet, and they sweat as much as 8 ounces of moisture per day The average square inch of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes (pigment cells), and more than a thousand nerve endings. There are about 2 million sweat glands in the average human body. The average adult loses 540 calories with every liter of sweat. Men sweat about 40 percent more than women.
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