Muscular System, and
Skeletal System Structures
Skeletal System Functions:
Provides framework for body
Protect internal organs including
the heart, lung, and brain.
Produces blood cells.
Storehouse for minerals, including
calcium and phosphorus.
206 bones in a human
– Axial skeleton—skull,
vertebral column, ribs, and
– Appendicular Skeleton—
arms, legs, shoulders,
pelvic girdle (hip)
Bone Structure—pg 851
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.
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
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
– Skeletal muscle
– Smooth muscle
– Cardiac muscle
– 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
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
Skeletal Muscle Contraction
When a muscle contracts, the bones are pulled by
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
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
The number of fibers in a muscle is
fixed before we are born.
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
The inner living layer contains melanin a
cell pigment that colors the skin and
protects the cells from damage by solar
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
– When small injuries occur to the epidermis, such as a scrape,
epidermal cells divide by mitosis and fill in the gap left by the
– 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.
– 1st degree—redness and mild pain and involve the death of
– 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.
– 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
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.