Skeletal, Muscular & Integumentary Systems

• The skeleton provides an anchor for the muscles that move the body.

• There are 206 bones in a human adult as a newborn infant we start out with about 300.

Axial skeleton supports the central axis of the body; skull, vertebral column, and rib cage Appendicular skeleton bones of arms and legs

What do you think is a better model of a bone, a stick of chalk or a sponge?

The chalk may look more like a bone but the sponge shows what the structure actually looks like inside

What passes through the tubes and spaces inside bone?

Blood vessels and nerves PERIOSTEUM-Bone is surrounded by a tough layer of connective tissueHaversian canals-Network of tubes that contain blood vessels and nerves.

Bone marrowCavities that contain a soft tissue

There are two types of bone marrow:

yellow and red

• Yellow marrow is made up primarily of fat cells.

• Red marrow produces red blood cells, some kinds of white blood cells, and cell fragments called platelets.

Cartilage -Cells are scattered in a network of protein fibers—tough collagen and flexible elastin.

• Cartilage does not contain blood vessels.

• Cartilage cells must rely on nutrients from the tiny blood vessels in surrounding tissues.

• Cartilage is dense and fibrous, it can support weight, despite its extreme flexibility

Ossification -Cartilage is replaced by bone during the process of bone formation

• Osteoblasts create bone.• Osteocytes maintain the cellular activities of bone.• Osteoclasts break down bone

Force must be placed on bone for ossification to occur, because it is force that stimulates the osteoblasts to secrete the minerals that replace cartilage

Fracture - Breaking a bone

What effect do you think an exercise such as walking would have on the bones of the legs?

• It would stimulate ossification, so the bones would contain more minerals and be stronger.

What do you think might happen to the bones that are not exposed to force, such as the bones of astronauts in zero gravity?

– The bones would lose minerals because of lack of force exerted on them, so they become weaker

• Bone formation occurs in babies and children• Seven months before birth cartilage is gradually

replaced by bone• When a person grows, the growth plates are

lengthening in the long bones• When you stop growing, those growth plates are

then filled in with bone• Adults do retain some cartilage– Tip of nose, ears, where ribs attach to the

sternum

• Bone formation also occurs when a bone is broken

• Osteoclasts remove damaged bone tissue• Osteoblasts produce new bone tissue• The repair of a broken bone can take months

because the process is slow and gradual

Depending on its type of movement, a joint is classified as immovable, slightly movable, or freely movable

Immovable Joints• Where the bones in the skull meet

Slightly Movable Joints• The joints between the two bones of the lower leg and the joints between

adjacent vertebrae are examples of slightly movable joints.

Freely Movable Joints• Ball-and-socket joints permit circular movement—the widest range of

movement• Hinge joints permit back-and-forth motion, like the opening and closing of a

door• Pivot joints allow one bone to rotate around another• Saddle joints permit one bone to slide in two directions

Structure of joints

•Ends of bones are covered with a smooth layer of cartilage

•Joints are surrounded by a fibrous joint capsule that helps hold bones together

• Tendons attach muscles to bones.

• When muscles contract, tendons pull on bones to cause movement.

• LIGAMENTS – strip of tough connective tissue that hold bones together

• Synovial fluid – lubricates the ends so bones can slide past each other smoothly

Opposing Muscles in the Arms

Skeletal and Muscular Systems

What are the three types of muscle?

Skeletal Muscle• Skeletal muscles are usually attached to bones• Skeletal muscles are responsible for such voluntary

movements as typing on a computer keyboard, dancing, or winking an eye

• When viewed under a microscope at high magnification, skeletal muscle appears to have alternating light and dark bands or stripes called striations. For this reason, skeletal muscle is sometimes called striated muscle

• Most skeletal muscles are controlled by the central nervous system.

Smooth Muscles • Smooth muscles are usually not under voluntary

control

• A smooth muscle cell is spindle-shaped, has one nucleus, and is not striated

• Smooth muscles are found in hollow structures such as the stomach, blood vessels, and the small and large intestines

• Smooth muscles move food through your digestive tract, control the way blood flows through your circulatory system, and decrease the size of the pupils of your eyes in bright light.

Cardiac Muscle

• Cardiac muscle is found in just one place in the body—the heart

• The prefix cardio- comes from a Greek word meaning “heart.”

• Cardiac muscle is striated like skeletal muscle, although its cells are smaller.

• Cardiac muscle cells usually have one nucleus, but they may have two.

• Cardiac muscle is similar to smooth muscle because it is usually not under the direct control of the central nervous system

Muscle Contraction

• A muscle contracts when the thin filaments in the muscle fiber slide over the thick filaments

• The energy for muscle contraction is supplied by ATP

Neuromuscular junction • The point of contact between a motor neuron and a

skeletal muscle cell

How do body builders get muscles that increase in size?

• Muscles that are exercised regularly stay firm and increase in size by adding more material to the inside of the muscle cells

Integumentary System

• Skin is the largest organ of the human body.

• Skin makes up about 7% of your total body weight.

• The skin, hair, and nails form the integumentary system.

Integumentary System• The integumentary system does the following:

–protects the body from injury and UV radiation

–defends against disease

–helps regulate body temperature

–prevents the body from drying out

Integumentary SystemWaterproofing• The epidermis is the outermost layer of skin.

• It is made of flattened, dead cells composed of a protein called keratin.

– Keratin is also found in nails and hair.– Keratin makes the skin tough and waterproof.

– Without the protection of keratin and oil, our bodies would lose water through evaporation or absorb water from the environment.

Integumentary SystemDisease Prevention• The epidermis forms a tight barrier that keeps

bacteria out and protects the body from disease.

• Damage to large areas of skin allows bacteria to enter the body freely.

• This lack of protection is one reason why severe burns are so dangerous.

Integumentary SystemUV Prevention• The lower layers of the epidermis contain

cells that make melanin, a pigment that absorbs UV light.

• This absorption prevents DNA damage, which can cause skin cancer.

Integumentary System

Temperature Regulation• A network of blood vessels and nerves in the

dermis help regulate body temperatures.

• Sweat glands also help remove excess body heat through the evaporation of sweat.HOMEOSTASI

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