Chapter 24
Support and Movement of the Body
Section 1
HUMAN SKIN
Human Skin
• Your skin is one of your body’s major defenses.
• It is quite strong and helps keep us in and disease
causing organisms out.
• Outer layer = epidermis- which is made of dead
cells on top and living cells just underneath that
contain nerve endings.
• Inner layer= dermis-which is thicker and contains
blood vessels, nerve receptors, and hair follicles.
Sweat glands, oil glands, and wax glands are also
found here.
Human Skin Diagram
Structures of the Skin
• Hair Follicle = hair develops from cells in the hair
follicle. As the cells divide, hair grows. The part
of the hair deep inside the follicle is alive but the
part that is above the epidermis is composed of
closely packed dead cells.
• Oil glands= secrete oil to keep skin and hair soft,
flexible, and water resistant.
• Subcutaneous layer = not really part of the skin
but is just underneath the dermis and is made of
fat cells and fibers which cushion and insulate
your body.
Skin Color
• Melanin= dark pigment that causes much of the color
of human skin.
• Pink skin = less melanin and blood is showing through.
• Freckles= clumps of melanin
• Darker Races have a lot of melanin
• Carotene=yellowish pigment in skin
• Too much exposure to the sun’s UV rays will cause a
sunburn.
• Sunlight causes body to produce more melanin or
“tan”.
God designed your skin to protect you!
• Nerve receptors respond to cold, heat, touch, and pressure.
• Callus= thickened epidermis from over use. Helps protect the
delicate structures of the skin.
• Blisters= when skin is exposed to intense heat and or is rubbed
strongly before the epidermis has time to develop a callus. Blisters
protect the deeper layers of skin.
• Body temperature regulation= blood vessels and sweat glands work
together to maintain your body temperature.
• When you are very active: your blood vessels in the dermis open
wide to permit more blood to flow near the epidermis. This allows
heat to be released. At the same time sweat glands secrete
perspiration (sweat) through tiny pores on the surface of the
epidermis. Since sweat is mostly water, it evaporates quickly,
cooling the surface of your skin.
Section 2
The Skeletal System
You are born
with about 206
bones. Knee
caps develop as
you start to
crawl and walk.
Not all bones
are smooth and
solid. The
openings are
for the blood
vessels and
nerves. The
bumpy parts
are for tendons
and ligaments
to attach.
Functions of the Skeleton
• A. Framework for support and movement
• -without your skeleton you could not stand or sit upright,
your muscles would have no firm structures to move, and
your body would have no definite shape.
• B. Protection
• -skull protects your brain, your ribs protect your lungs and
heart, your vertebrae protect your spinal cord
• C. Storage of minerals
• -calcium and phosphorous that give bones strength
• D. Production of blood cells
• -red bone marrow produces about a billion new blood cells
every day
Bones
• Bones have different sizes and shapes.
• Most have hard coverings and sponge-like spaces
inside= spongybone. Marrow cavities and the
spaces in the spongy bone are filled with bone
marrow.
• The outer covering of bone =periosteum
• Ligaments=tough, flexible bands of connective
tissue that attach bones to other bones at joints.
• Tendons= bands of connective tissue that
connect muscles to bones.
Structure of Bones
• Two main types of tissue make up the skeleton= bone and cartilage.
• Bone= tissue consisting of living bone cells and non living material they
secrete. This nonliving substance made up of calcium, phosphorus, and
microscopic fibers forms circular layers around the tiny blood vessels in
bones. Each layer has blood vessels that provides nutrients to the layer of
bone cells near it making an osteon. Many osteons side by side make
hard, strong bone sections.
• Cartilage= tissue that is soft and more flexible than bone because its
nonliving material contains very little calcium and phosphorus. Blood
vessels never pass through cartilage. Nutrients are able to pass from the
surface into the soft material to the cartilage cells. Cartilage covers the
ends of bones in joints and makes up the end of your nose and outer ears.
• Cartilage plates= sometimes called growth plates are found near the ends
of long bones. As the cells divide and change to bone tissue, the bones
get longer. During high school, most of the cartilage plates turn to bone
and you stop growing.
Joints
•
•
•
•
•
•
•
•
•
Joint= place where two or more bones meet.
Hinge Joint= bends in only one direction
Example: knee and elbow
Gliding Joint=slide and twist
Example: back vertebrae
Ball-and-Socket Joint=free movements
Example: shoulder and hip
Pivot Joint=circular movement
Example: joint between the two bones near the elbow
when arm twists
• Fused Joint= allow no movement
• Example: skull
Section 3
The Muscular System
• Your body moves by contracting which involves becoming shorter
and thicker. This means your muscles pull but never push.
• Types of Muscles:
• Voluntary: ones you control at will
• Skeletal : voluntary muscles that move your skeleton. These have
patterns of light and dark bands called striations which appear
where different kinds of protein molecules meet.
• Striated Muscle: mostly skeletal muscle but can also be seen in the
heart muscle.
• Involuntary: muscle tissue that you can not control. (heart,
stomach, intestines, blood vessels)
• Smooth Muscles: most involuntary muscles because they do not
have striations.
• Heart Muscle: Both involuntary and striated
How Muscles Move
• Usually skeletal muscles work in pairs.
• Example: biceps and triceps
• Longest Muscle in your body=sartorius muscle
which attaches the upper part of the pelvic
bone, and extends across both the hip and the
knee joints, and attaches on the inner side of
the tibia near the knee joint.
• Some muscles are for your mouth and eyes
and tongue and do not involve joints.
Other Functions of Muscles
• Muscles also provide posture for your body.
Exp. – the muscles along your neck and back
When muscles contract they produce heat.
When you shiver=result of involuntary muscle
contractions that give off heat and raise the
body temperature.
How Muscles Work
• Muscles need a supply of energy. This comes in the
form of sugar(glucose) carried by the blood. Muscles
release the energy stored in sugar by breaking down
the sugar. The process that muscles use is called
aerobic cellular respiration. This requires oxygen. The
blood carries oxygen from the lungs to the muscles.
The muscles then use the oxygen to break down sugar,
the energy that is released is available to make the
muscle cells contract.
• Occasionally, when you are very active, your muscles
will break down sugar without oxygen which is called
anaerobic cellular respiration which causes lactic acid
to build up in the muscles. (Sore Muscles)
Human Muscle Diagram
The body has
about six
hundred
muscles that
move it. They
always pull
never push.
They work in
pairs that pull in
opposite
directions.