Unit 7:The Human Body!

Chapter 19: Skin, Skeletal System, and Muscular System

19.1 Human Body Organization

• Cells => Tissues => Organs => Organ systems => Organism

Review parts of the cell: the basic unit of life

Tissue: a group of cells that work together to perform a specific function.

• There are 4 main types of tissue in the human body:– Epithelial tissue– Connective tissue– Muscle tissue– Nervous tissue

Epithelial tissue

• Covers the outside of the body and lines structures inside the body.

• Cells are closely packed to provide a protective barrier for the body.

Connective tissue

• Tendons, ligaments, bones, and blood.• Holds together other tissues.• Cells are loosely packed.

Muscle tissue

• Muscles around bones and in organs.• Allows movement.

Nervous tissue

• Gathers and transmits information throughout the body (senses and responds).

Organ

• A group of tissues working together to perform a specific function.

Organ system

• A group of organs that work together to carry out one or more body functions.

Circulatory system

• Pumps blood through the body, brings nutrients to cells, carries wastes away from cells.

Skeletal system

• Supports the body and gives it shape.

Muscular system

• Enables the body to move.

Respiratory system

• Takes in oxygen from the air and gives off carbon dioxide.

Digestive system

• Takes in food and breaks it down into usable energy.

Urinary system

• Rids the body of liquid and dissolved wastes and helps balance salts and water in the body.

Nervous system

• Takes in and responds to information in the environment.

Endocrine system

• Helps regulate the body’s functions

Immune system

• Helps the body fight disease.

Reproductive system

• Allows the production of offspring.

19.2 Skin

Skin: also known as the integumentary system.

• Largest organ of the body (2 square meters).• Sense organ.• Covers body and protects it from injury.• Regulates body temperature.• Rids body of wastes.• Prevents water and blood loss.• Protects body from disease.

The skin is made of three layers:

• Epidermis: Outer layer.

• Dermis: Middle layer.

• Subcutaneous tissue: Deepest layer.

Epidermis:

• The outermost layer. Replaced every 28 days.• Made of cells called keratinocytes that produce

keratin, a protein that makes the skin tough.– Hair, nails, feathers, claws, and horns are also

made of keratin.• Keratinocytes protect deeper cells from

damage and drying out, and keep out microorganisms.

The cells in the epidermis are in layers.

• Old keratinocytes fill up with keratin and get pushed up by new keratinocytes, which are produced by the innermost layer of the epidermis.

• As the cells get pushed away, they are away from the blood supply and die.

• These cells then flake off (and become dust, EWW!)

Other cells in the epidermis:

• Melanocytes: Produce melanin.– Melanin: The chemical responsible for skin color.– More melanin = darker skin.– Melanin is released when the skin is exposed to

the sun (causes a tan). Protects skin from sun damage.

• Langerhan’s cells: Immune cells.

Dermis: the thick middle layer of the skin.

• Contains many different items:– Nerve endings: Sense of touch.– Blood vessels: Control body temperature.• Expand to release heat, contract to keep heat.

– Sweat glands: Control body temperature.• Sweat evaporates to cool body off. • Sweat also removes some wastes from the body.

More items in the dermis:

– Connective tissue– Collagen and elastin fibers: Elasticity.– Hair follicles– Oil glands: Keep skin smooth and waterproof and

keep hair from getting brittle.

Subcutaneous tissue

• The innermost layer of the skin.• Contains connective tissue and fat cells.• Fat cells insulate the body and conserve heat.

Burns:

• First degree: Just the epidermis. Pain.• Second degree: Epidermis and dermis. Pain.• Third degree: All three layers of skin. No pain

because the nerve endings are destroyed.

Skin Cancer: Warning Signs: The ABCDEs of Melanoma

• AsymmetryIf you draw a line through this mole, the two halves will not match.

• BorderThe borders of an early melanoma tend to be uneven. The edges may be scalloped or notched.

• ColorHaving a variety of colors is another warning signal. A number of different shades of brown, tan or black could appear. A melanoma may also become red, blue or some other color.

• DiameterMelanomas usually are larger in diameter than the size of the eraser on your pencil (1/4 inch or 6 mm), but they may sometimes be smaller when first detected.

• EvolvingAny change — in size, shape, color, elevation, or another trait, or any new symptom such as bleeding, itching or crusting — points to danger.

http://www.skincancer.org/melanoma/Page-3.html

Nails:

• Modified skin.• Mostly keratin.• Protect the soft tissue at the tips of the

fingers.

Hair:

• Covers the entire body (except for palms, soles, and lips)

• Mostly keratin.• Protects eyes and nose from dust.• Keeps body warm. Insulates head. Goose

bumps.• Hair follicles: Tiny, saclike structures in dermis

from which hair grows.

19.3 The Skeletal System

There are 206 bones in the skeletal system.

• Gives the body shape.• Supports the body.• Protects organs.• Allows movement.• Stores nutrients.• Produces blood cells.

The skeleton is divided into two main sections:

• Axial skeleton: Bones of the head, neck, and trunk (in green).

• Appendicular skeleton: Bones of the limbs (in purple).

Bones to know:

• Skull• Hyoid• Sternum• Ribs• Vertebrae• Sacrum• Coccyx

Bones to know:

• Clavicle• Scapula• Humerus• Radius• Ulna• Carpal bones• Metacarpal bones• Phalanges

Bones to know:

• Pelvic girdle• Femur• Patella• Tibia• Fibula• Tarsal bones• Metatarsal bones• Phalanges

A bone’s shape relates to its function:

• Long bones: In arms and legs, for example.• Short bones: In fingers and toes, for example.• Flat bones: In skull and pelvis, for example.• Irregular bones: In backbone and ears, for

example.

Composition of a bone:

• A bone is made of three layers:– Periosteum– Compact bone– Spongy bone– (plus bone marrow in

the middle of long bones)

• Periosteum: Thin layer that covers the bone. Contains blood vessels.

• Compact bone: Dense layer underneath the periosteum. Contains blood vessels, nerve cells, osteocytes, and minerals (calcium and phosphorous).

• Spongy bone: Strong but lightweight.

• Bone marrow: Found in the cavity in the middle of long bones.– Red bone marrow: Produces red blood cells and

some white blood cells.– Yellow bone marrow: Contains mostly fat cells,

which store energy.

Bone growth and repair are allowed by two types of cells:

• Osteoblasts: Produce bone.

• Osteoclasts: Break down bone.

Bone tissue

Formation of bone:

• Bones start out as cartilage in the fetus.– Cartilage: Soft, flexible connective tissue.

• The cartilage gradually changes to bone through a process called ossification.

• At birth, a person has over 300 bones.• As we develop, some of these bones fuse, so

we end up with 208 bones.

Joint:

• The place where two bones meet.• There are three classifications of joints:– Immovable: Allow no movement.• Example: Bones in the skull.

– Slightly movable: Allow limited movement.• Example: Bones in the spine.

– Movable: Allow movement in one or more directions.• Example: Bones in the arms and legs.

There are four kinds of movable joints:

• Ball and socket: Allows movement in many directions.– Examples: Hip and shoulder.

Ball and socket joint

• Gliding: Allow bones to slide past each other.– Examples: Wrist and ankle.

• Hinge: Allow back and forth movement.– Examples: Elbow, knee, finger, and toe.

• Pivot: Allow bones to twist past each other.– Example: Forearm.

• Ligaments: Thick connective tissue that holds bones together at joints.

• Tendons: Attach muscle to bone.

19.4 The Muscular System

• There are more than 600 muscles in your body!

• Muscles make up over 40% your body mass.

Muscles to know:

• Sternocleidomastoid• Deltoid• Trapezius• Pectoralis major• Biceps brachii• Triceps brachii• Rectus abdominus

Muscles to know:

• Sartorius• Gastrocnemius• Latissimus dorsi• Hamstring group• Quadriceps group• Gluteus maximus

There are three types of muscle

tissue:

Skeletal muscle:

• Attach to bones.• Long, thin cells with

more than one nucleus.• Striated: Has

alternating light and dark bands.

• Pull on bones to allow voluntary movements.

Smooth muscle:

• Found in internal organs.

• Tapered cells with one nucleus. Not striated.

• Is involuntary – not under conscious control.

Cardiac muscle:

• Found in the heart.• Branched cells with

striations and only one nucleus.

• Involuntary.

Skeletal muscle structure:• Skeletal muscle fibers are grouped into bundles.

These bundles contain muscle cells, connective tissue, nerves, and blood vessels.

Actin and myosin:

• The proteins responsible for muscle contraction.

• Gives the muscle cell its striated appearance.

Muscle cell contraction:

• http://www.youtube.com/watch?v=gJ309LfHQ3M

Motor nerve:

• Connects muscle cells to brain.

• One motor nerve can connect to many muscle cells.

Muscles and movement:

• Tendon: Attaches muscle to bone.• Skeletal muscles PULL on bones only.– In order to allow for a full range of motion,

skeletal muscles are usually found in pairs• One muscle moves the bone in one direction, and

another moves it in the opposite direction.• When one contracts, the other relaxes, and vice versa.