Chapter 32 Notes, The
Integumentary, Skeletal,
and Muscular Systems
The Integumentary System
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The integumentary system includes the organs
that cover and protect the body.
The main organ of the integumentary system is
the skin.
Skin consists of four types of tissues.
The four tissues are epithelial tissue, connective
tissue, muscle tissue and nerve tissue.
Structure of the Skin
The Structure of the Skin
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The upper layer of the skin is called epidermis.
The epidermis is a layer of cells about 10 to 30
cells thick called epithelial cells
The epidermis is about as thin as paper.
The cells of the epidermis contain a protein
substance called keratin, which waterproofs and
protects the cells and tissues below it.
The Epidermis
The Epidermis
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The very top layer of cells of the epidermis are
constantly being shed.
A large portion of the dust in your house is dead
skin cells.
An entire layer of skin cells can be lost each
month.
The inner layer of epidermis contains cells that
are continually dividing by mitosis.
The Epidermis
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Some of the cells of the inner layer of the
epidermis are called melanocytes. Melanocytes
contain a protective pigment called melanin.
Melanin is a pigment that absorbs ultraviolet
radiation. The amount of melanin a person has
is primarily determined by their genes.
The darker a person's skin is, the more melanin
they have in their epidermis.
Melanin can also be produced in response to
bright sunlight when a person gets a suntan.
Melanin
Structure of the Skin
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Below the epidermis is another layer of skin
called the dermis.
The dermis is about 15 – 40 times thicker than
the epidermis.
The dermis consists mostly of connective
tissues. The primary purpose of this connective
tissue is to prevent the skin from tearing and it
makes the skin more elastic.
Within the connective tissue there are also
nerves, muscles, glands, and hair follicles.
Structure of the Skin
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Below the dermis is the subcutaneous layer.
The subcutaneous layer is another layer of
connective tissue that stores fat as an energy
reservoir and it also insulates the body.
Hair, fingernails and toenails are also part of the
integumentary system.
Hair and nails contain keratin and develop from
epithelial cells.
Structure of the Skin
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Hair cells grow out of narrow cavities in the
dermis called hair follicles.
Hair follicles also usually have sebaceous
glands or oil glands associated with them.
Sebaceous glands lubricate the skin and hair.
When the sebaceous glands and hair follicles
get blocked, acne can occur.
Hair Follicle and Sebaceous Gland
Functions of the Integumentary System
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Temperature regulation – insulating fat, arrector
pili muscles, and sweat glands are just some of
the ways that skin can regulate body temp.
Vitamin production – skin responds to sunlight
by producing vitamin D. Vitamin D increases
absorption of calcium into the bloodstream and
it is essential for bone formation.
Protection – first line of defense against disease
and foreign substances. Prevents water loss.
Damage to the Skin
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Cuts and scrapes – in minor cuts and scrapes
only the epidermis is effected. When deep cuts
occur, blood clots form a scab and white blood
cells remove bacteria from the wound.
Burns – burns can be minor (first degree) and
redness and swelling may occur, or severe
(second and third degree) and blisters or loss of
skin function may occur.
Damage to the Skin
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Skin Cancer – too much exposure to the sun or
tanning beds is believed to cause skin cancer.
Skin cancer is the most common form of cancer
in the United States.
There are two types of skin cancer: melanoma
and nonmelanoma. Melanoma begins in the
melanocytes in the epidermis.
Melanoma is the deadliest form of skin cancer.
1 person dies every hour from melanoma in the
United States.
The Structure of the Skeletal System
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There are 206 bones in the human body
The human skeleton is divided into two different
skeletal divisions: the axial skeleton and the
appendicular skeleton.
The axial skeleton includes the skull, the
vertebral column, the ribs, and the sternum.
The appendicular skeleton includes the bones
of the shoulders, arms, hands, legs, and feet.
The Axial and Appendicular Skeleton
The Structure of Bone
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There are two types of bone structure: compact
bone and spongy bone.
Compact bone is dense and strong, and it
provides strength and protection.
The outer layer of all bones are composed of
compact bone.
Spongy bone is less dense, has many cavities
that contain bone marrow, and is usually found
in the center or the end of bones.
Compact and Spongy Bone
The Structure of Bone
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Running the length of compact bones are
tubelike structures called osteons.
Osteons contain blood vessels and nerves.
The blood vessels provide oxygen and nutrients
to living bone cells called osteocytes.
There are two types of bone marrow: red bone
marrow and yellow bone marrow.
Red and white blood cells and platelets are
produced in the red bone marrow.
Yellow bone marrow consists of stored fat.
Compact Bone Structure
Bone Formation and Maintenance
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During early fetal development, cartilage
develops into bone forming cells.
Osteoblasts are bone forming cells.
The process of bone formation from osteoblasts
is a process called ossification.
Osteoblasts are also responsible for bone
growth and repair.
Cells that are responsible for breaking down
old, worn down bones are called osteoclasts.
Joints and Ligaments
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Joints occur wherever two or more bones meet.
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Ball and socket – hips and shoulders
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Pivot – one example is the radius and ulna
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Hinge – elbows and knees
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Gliding – wrists, ankles, and vertebrae
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Sutures – immovable joints like the sutures that
attach all of the bones of the skull.
Separated bones are held together by tough
bands of connective tissue called ligaments.
Functions of the Skeletal System
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Support – the legs, pelvis and vertebral column
support the entire body.
Protection – Skull protects the brain, vertebrae
protects the spinal cord, rib cage protects the
vital organs (heart, lungs, and liver).
Formation of blood cells – red bone marrow
produces blood cells and platelets.
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Reservoir – storage of fat and nutrients.
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Movement – attachment point for muscles.
The Muscular System
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The human body has three different muscle
tissues: smooth, cardiac, and skeletal muscles.
Smooth muscle – involuntary (cannot be
consciously controlled) muscles that control
organs like the stomach and intestines
Cardiac muscle – involuntary muscle that
controls the heart.
The main difference between smooth and
cardiac muscle, is that cardiac muscle has
striations and smooth muscle does not.
The Muscular System
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Most muscles of the body are skeletal muscles.
Skeletal muscles – voluntary (can be
consciously controlled) muscles that are
attached to bones by tendons.
Skeletal muscles are responsible for all the
voluntary movement of the body.
Tendons – tough bands of connective tissue
that connect skeletal muscles to bones.
Skeletal muscles are striated like cardiac
muscles.
Muscle Types
Skeletal Muscle Structure and Function
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Most muscles are arranged in opposing, or
antagonistic pairs.
A good example of this is your biceps and
triceps. They work against each other.
Skeletal muscles are arranged into fibers.
Each fiber is arranged into smaller strands
called myofibrils.
Myofibrils are made up of small protien
filaments called myosin and actin.
Skeletal Muscle Structure and Function
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The myofibrils are arranged into different
sections called sarcomeres.
A sarcomere is the part of the muscle that
contracts.
The striations of skeletal and cardiac muscles
are the result of sarcomeres.
When a nerve impulse is sent to a muscle, the
actin filaments slide toward the myosin
filaments in the center of the sarcomere.
Skeletal Muscle Contraction
Are you a long distance runner or a sprinter?
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Believe it or not, this probably has more to do
with genetics than you may think.
Slow-twitch muscles – more endurance, resists
fatigue, more mitochondria, more myoglobin
which means more oxygen, darker colored.
Fast-twitch muscles – rapid burst of speed,
strength, and energy, muscles fatigue easily,
less mitochondria available, less myoglobin
which means less oxygen, lactic acid build up,
lighter colored, increased number of myofibrils,
increased muscle size and diameter.