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Chapter 32 Notes: The
Integumentary, Skeletal,
and Muscular Systems
The Integumentary System
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The integumentary system is the system of organs in
the body that covers and protects the body.
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The main organ of this system is the skin.
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Skin is composed of four different types of tissues.
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Those four different types of tissues are the epithelial
tissue, connective tissue, muscle tissue and the
nerve tissue.
Structure of the Skin
The Structure of the Skin
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The upper most layer of the skin is called the
epidermis.
The epidermis is a layer of cells about 10 to 30 cells
thick that is made up of 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.
In fact, a large portion of the dust in your house
consists of dead skin cells from the epidermis.
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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Cells that are found in the inner layer of the
epidermis called melanocytes contain a protective
pigment called melanin.
Melanin is a pigment that absorbs (UV) ultraviolet
radiation. The amount of melanin in a person’s skin
determines the color of the skin.
Skin color is primarily determined by genes, but it
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 tissue. The
function of this connective tissue is to prevent the skin
from tearing, and it makes the skin more elastic.
Within the dermis there is 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 also a layer of connective
tissue that stores fat and insulates the body.
Hair, fingernails and toenails are also part of the
integumentary system that are made of keratin.
Structure of the Skin
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Hair cells grow out of narrow cavities in the dermis
called hair follicles.
Most hair follicles 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 occurs.
Hair Follicles and Sebaceous Glands
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. Blood vessels can
also constrict and dilate to regulate body temp.
Vitamin production – skin responds to sunlight by
producing vitamin D. Vitamin D increases absorption
of calcium into the bloodstream for bone growth.
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 affected. When deep cuts occurs,
blood clots must 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.
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Melanoma is the deadliest form of skin cancer.
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1 person dies every hour from melanoma in the U.S.
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. Not striped or striated.
Cardiac muscle – involuntary muscle that controls the
heart. Less nuclei connected by gap junctions.
The main structural 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. Muscles striated and contain many nuclei.
Skeletal muscles are responsible for movement.
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 protein
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 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, more
strength, muscles fatigues easily, less mitochondria
available, less myoglobin which means less oxygen,
more lactic acid, lighter colored, increased number of
myofibrils, increased muscle size and diameter.
The Structure of the Skeletal System
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The human body has 206 bones.
The human skeleton is divided into two
different 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 tissue; 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 tube-like
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 blood cells, 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.
The process of bone formation from osteoblasts
is called ossification.
Osteoblasts are bone forming cells.
Osteoblasts are responsible for bone growth
and repair.
Cells that are responsible for breaking down
old, worn out 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 some vertebrae
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Sutures – immovable joints like the sutures that attach
all of the bones of the skull.
The bones connected at joints are held together by
tough bands of connective tissue called ligaments.
Functions of the Skeletal System
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Support – 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, liver).
Formation of blood cells – red bone marrow
produces blood cells and platelets.
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Reservoir – stores calcium and phosphorus.
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Movement – attachment point for muscles.