Chapter 19: Skin, Skeletal System, and Muscular System
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19.1 Human Body Organization Cells => Tissues => Organs
=> Organ systems => Organism
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Review parts of the cell: the basic unit of life
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Tissue: a group of cells that work together to perform a
specific function. There are 4 main types of tissue in the human
body: Epithelial tissue Connective tissue Muscle tissue Nervous
tissue
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Epithelial tissue Covers the outside of the body and lines
structures inside the body. Cells are closely packed to provide a
protective barrier for the body.
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Connective tissue Tendons, ligaments, bones, and blood. Holds
together other tissues. Cells are loosely packed.
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Muscle tissue Muscles around bones and in organs. Allows
movement.
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Nervous tissue Gathers and transmits information throughout the
body (senses and responds).
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Organ A group of tissues working together to perform a specific
function.
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Organ system A group of organs that work together to carry out
one or more body functions.
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Circulatory system Pumps blood through the body, brings
nutrients to cells, carries wastes away from cells.
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Skeletal system Supports the body and gives it shape.
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Muscular system Enables the body to move.
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Respiratory system Takes in oxygen from the air and gives off
carbon dioxide.
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Digestive system Takes in food and breaks it down into usable
energy.
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Urinary system Rids the body of liquid and dissolved wastes and
helps balance salts and water in the body.
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Nervous system Takes in and responds to information in the
environment.
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Endocrine system Helps regulate the bodys functions
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Immune system Helps the body fight disease.
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Reproductive system Allows the production of offspring.
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19.2 Skin
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Skin: also known as the integumentary system. Largest organ of
the body (2 square meters). Sense organ. Covers body and protects
it from injury. Regulates body temperature. Rids body of wastes.
Prevents water and blood loss. Protects body from disease.
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The skin is made of three layers: Epidermis: Outer layer.
Dermis: Middle layer. Subcutaneous tissue: Deepest layer.
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Epidermis: The outermost layer. Replaced every 28 days. Made of
cells called keratinocytes that produce keratin, a protein that
makes the skin tough. Hair, nails, feathers, claws, and horns are
also made of keratin. Keratinocytes protect deeper cells from
damage and drying out, and keep out microorganisms.
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The cells in the epidermis are in layers. Old keratinocytes
fill up with keratin and get pushed up by new keratinocytes, which
are produced by the innermost layer of the epidermis. As the cells
get pushed away, they are away from the blood supply and die. These
cells then flake off (and become dust, EWW!)
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Other cells in the epidermis: Melanocytes: Produce melanin.
Melanin: The chemical responsible for skin color. More melanin =
darker skin. Melanin is released when the skin is exposed to the
sun (causes a tan). Protects skin from sun damage. Langerhans
cells: Immune cells.
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Dermis: the thick middle layer of the skin. Contains many
different items: Nerve endings: Sense of touch. Blood vessels:
Control body temperature. Expand to release heat, contract to keep
heat. Sweat glands: Control body temperature. Sweat evaporates to
cool body off. Sweat also removes some wastes from the body.
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More items in the dermis: Connective tissue Collagen and
elastin fibers: Elasticity. Hair follicles Oil glands: Keep skin
smooth and waterproof and keep hair from getting brittle.
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Subcutaneous tissue The innermost layer of the skin. Contains
connective tissue and fat cells. Fat cells insulate the body and
conserve heat.
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Burns: First degree: Just the epidermis. Pain. Second degree:
Epidermis and dermis. Pain. Third degree: All three layers of skin.
No pain because the nerve endings are destroyed.
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Skin Cancer: Warning Signs: The ABCDEs of Melanoma Asymmetry If
you draw a line through this mole, the two halves will not match.
Border The borders of an early melanoma tend to be uneven. The
edges may be scalloped or notched. Color Having a variety of colors
is another warning signal. A number of different shades of brown,
tan or black could appear. A melanoma may also become red, blue or
some other color. Diameter Melanomas usually are larger in diameter
than the size of the eraser on your pencil (1/4 inch or 6 mm), but
they may sometimes be smaller when first detected. Evolving Any
change in size, shape, color, elevation, or another trait, or any
new symptom such as bleeding, itching or crusting points to danger.
http://www.skincancer.org/melanoma/Page-3.html
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Nails: Modified skin. Mostly keratin. Protect the soft tissue
at the tips of the fingers.
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Hair: Covers the entire body (except for palms, soles, and
lips) Mostly keratin. Protects eyes and nose from dust. Keeps body
warm. Insulates head. Goose bumps. Hair follicles: Tiny, saclike
structures in dermis from which hair grows.
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19.3 The Skeletal System
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There are 206 bones in the skeletal system. Gives the body
shape. Supports the body. Protects organs. Allows movement. Stores
nutrients. Produces blood cells.
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The skeleton is divided into two main sections: Axial skeleton:
Bones of the head, neck, and trunk (in green). Appendicular
skeleton: Bones of the limbs (in purple).
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Bones to know: Skull Hyoid Sternum Ribs Vertebrae Sacrum
Coccyx
A bones shape relates to its function: Long bones: In arms and
legs, for example. Short bones: In fingers and toes, for example.
Flat bones: In skull and pelvis, for example. Irregular bones: In
backbone and ears, for example.
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Composition of a bone: A bone is made of three layers:
Periosteum Compact bone Spongy bone (plus bone marrow in the middle
of long bones)
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Periosteum: Thin layer that covers the bone. Contains blood
vessels. Compact bone: Dense layer underneath the periosteum.
Contains blood vessels, nerve cells, osteocytes, and minerals
(calcium and phosphorous). Spongy bone: Strong but
lightweight.
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Bone marrow: Found in the cavity in the middle of long bones.
Red bone marrow: Produces red blood cells and some white blood
cells. Yellow bone marrow: Contains mostly fat cells, which store
energy.
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Bone growth and repair are allowed by two types of cells:
Osteoblasts: Produce bone. Osteoclasts: Break down bone.
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Bone tissue
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Formation of bone: Bones start out as cartilage in the fetus.
Cartilage: Soft, flexible connective tissue. The cartilage
gradually changes to bone through a process called ossification. At
birth, a person has over 300 bones. As we develop, some of these
bones fuse, so we end up with 208 bones.
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Joint: The place where two bones meet. There are three
classifications of joints: Immovable: Allow no movement. Example:
Bones in the skull. Slightly movable: Allow limited movement.
Example: Bones in the spine. Movable: Allow movement in one or more
directions. Example: Bones in the arms and legs.
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There are four kinds of movable joints:
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Ball and socket: Allows movement in many directions. Examples:
Hip and shoulder. Ball and socket joint
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Gliding: Allow bones to slide past each other. Examples: Wrist
and ankle.
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Hinge: Allow back and forth movement. Examples: Elbow, knee,
finger, and toe.
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Pivot: Allow bones to twist past each other. Example:
Forearm.
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Ligaments: Thick connective tissue that holds bones together at
joints. Tendons: Attach muscle to bone.
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19.4 The Muscular System There are more than 600 muscles in
your body! Muscles make up over 40% your body mass.
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Muscles to know: Sternocleidomastoid Deltoid Trapezius
Pectoralis major Biceps brachii Triceps brachii Rectus
abdominus
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Muscles to know: Sartorius Gastrocnemius Latissimus dorsi
Hamstring group Quadriceps group Gluteus maximus
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There are three types of muscle tissue:
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Skeletal muscle: Attach to bones. Long, thin cells with more
than one nucleus. Striated: Has alternating light and dark bands.
Pull on bones to allow voluntary movements.
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Smooth muscle: Found in internal organs. Tapered cells with one
nucleus. Not striated. Is involuntary not under conscious
control.
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Cardiac muscle: Found in the heart. Branched cells with
striations and only one nucleus. Involuntary.
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Skeletal muscle structure: Skeletal muscle fibers are grouped
into bundles. These bundles contain muscle cells, connective
tissue, nerves, and blood vessels.
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Actin and myosin: The proteins responsible for muscle
contraction. Gives the muscle cell its striated appearance.
Motor nerve: Connects muscle cells to brain. One motor nerve
can connect to many muscle cells.
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Muscles and movement: Tendon: Attaches muscle to bone. Skeletal
muscles PULL on bones only. In order to allow for a full range of
motion, skeletal muscles are usually found in pairs One muscle
moves the bone in one direction, and another moves it in the
opposite direction. When one contracts, the other relaxes, and vice
versa.