Biology II - Integrative Act

UNIVERSIDAD AUTÓNOMA DE NUEVO LEÓN

Group 220

Preparatoria no. 9

Biology II

INTEGRATIVE ACTIVITY ANATOMY

SKELETAL SYSTEM The skeletal system includes all of the bones and joints in the body. Each bone is a complex living organ that is made up of many cells, protein fibers, and minerals. The skeleton acts as a scaffold by providing support and protection for the soft tissues that make up the rest of the body. The skeletal system also provides attachment points for muscles to allow movements at the joints. New blood cells are produced by the red bone marrow inside of our bones.

• • •

The skeletal system in an adult body is made up of 206 individual bones. These bones are arranged into two major divisions: the axial skeleton and the appendicular skeleton. The axial skeleton runs along the body’s midline axis and is made up of 80 bones in the following regions: Skull • Ribs Hyoid • Sternum Auditory ossicles

•

Vertebral column The appendicular skeleton is made up of 126 bones in the folowing regions:

• • •

Upper limbs Lower limbs Pelvic girdle

•

Pectoral (shoulder) girdle

From our head to our toes, our bones provide support for our bodies and help form our shape. The skull protects the brain and forms the shape of our face.

The spinal cord, a pathway for messages between the brain and the body, is protected by the backbone, or spinal column. The ribs form a cage that shelters the heart, lungs, liver, and spleen, and the pelvis

helps protect the bladder, intestines, and in girls, the reproductive organs.

Although they're very light, bones are strong enough to support our entire weight.

Bone consists of four types of cells: osteoblasts, osteoclasts, osteocytes, and osteoprogenitor (or osteogenic) cells.

Joints are where two bones meet.

They make the skeleton flexible — without them, movement would be impossible.

Muscles are also necessary for movement: They're the masses of tough, elastic tissue that pull our bones when we move.

Skeletal muscles are sheathed by a tough layer of connective tissue called the epimysium. The epimysium anchors muscle tissue to tendons at each end, where the epimysium becomes thicker and collagenous. It also protects muscles from friction against other muscles and bones.

A skeletal muscle fiber is surrounded by a plasma membrane called the sarcolemma, which contains

sarcoplasm, the cytoplasm of muscle cells. A muscle fiber is composed of many fibrils, which give the cell its striated appearance.

Simplified schema of basic nervous system function. Signals are picked up by sensory receptors and sent to the spinal cord and brain via the afferent leg of the peripheral nervous system, whereupon processing occurs that results in signals sent back to the spinal cord and then out to motor neurons via the efferent leg.

The 3 types of muscle tissue are cardiac, smooth, and skeletal. Cardiac muscle cells are located in the walls of the heart, appear striated, and are under involuntary control.

Smooth muscle fibers are located in walls of hollow visceral organs, except the heart, appear spindle-shaped, and are also under involuntary control. Skeletal muscle fibers occur in muscles which are attached to the skeleton. They are striated in appearance and are under voluntary control.

Together, our bones, muscles, and joints — along with tendons, ligaments, and cartilage — form our musculoskeletal system and enable us to do everyday physical activities.

MUSCULAR SYSTEM The muscular system is responsible for the movement of the human body.

Attached to the bones of the skeletal system are about 700 named muscles that make up roughly half of a person’s body weight. Each of these muscles is a discrete organ constructed of skeletal muscle tissue, blood vessels, tendons, and nerves. Muscle tissue is also found inside of the heart, digestive organs, and blood vessels.

MUSCLE CONTRACTION

Muscle contraction is the activation of tension-generating sites within muscle fibers. In physiology, muscle contraction does not necessarily

mean muscle shortening because muscle tension can be produced without changes in muscle length such as holding a heavy book or a dumbbell at the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.

INTEGUMENTARY SYSTEM

The integumentary system is an organ system consisting of the skin, hair, nails, and exocrine glands. The skin is only a few millimeters thick yet is by far the largest organ in the body. The average person’s skin weighs 10 pounds and has a surface area of almost 20 square feet. Skin forms the body’s outer covering and forms a barrier to protect the body from chemicals, disease, UV light, and physical damage. Hair and nails extend from the skin to reinforce the skin and protect it from environmental damage. The exocrine glands of the integumentary system produce sweat, oil, and wax to cool, protect, and moisturize the skin’s surface.

THE SKIN The skin is by far the largest organ of the human body, weighing about 10 pounds (4.5 kg) and measuring about 20 square feet (2 square meters) in surface area. It forms the outer covering for the entire body and protects the internal tissues from the external environment.

The skin consists of two distinct layers: the epidermis and the dermis.

THE HAIR Hair is present on all skin surfaces except the palms, soles, lips, nipples, and various parts of the external reproductive organs; however, it is not always well developed. For example, it is very fine on the forehead and the inside surface of the arm. Each hair develops from a group of epidermal cells at the base of a tube-like depression called a hair follicle. This follicle extends from the surface into the dermis and may pass into the subcutaneous layer.

The cells at its base receive nourishment from dermal blood vessels that occur in a projection of connective tissue, called the derma papilla, at the base of the follicle. As these epidermal cells divide and grow, older cells are pushed toward the surface. The cells that move upward and away from the nutrient

supply then die. Their remains constitute the shaft of a developing hair. In other words, a hair is composed of dead epidermal cells.

THE FINGERNAILS The fingernails are a sort of envelope composed of keratin, a tough protein, which cover the top of the terminal phalanges of a person's fingers.

Nails are similar to the claws that can be found in other animals. Each nail is made up of a nail plate—this is the top of the nail. It is also made up of the nail matrix, a thin layer of tissue upon which the nail plate rests and the site of the cells that eventually become the nail plate. Each nail also has a nail bed—a layer of skin that connects the nail matrix to the hand.

And lastly, each nail has the grooves that surround the nail matrix.

COMMON SKIN DISORDERS Skin disorders vary greatly in symptoms and severity. They can be temporary or permanent, and may be painless or painful. Some have situational causes, while others may be genetic. Some skin conditions are minor, and others can be life-threatening.

Protecting your skin from the sun is important for not only your appearance, but your health. It’s too important to skip.

Skin Cancer One of the most obvious risks of sun exposure is skin cancer. When you’re exposed to the sun, UVA

and UVB rays reach your skin, damaging your skin cells. Some of the damage repairs itself, but some doesn’t. After several years of this type of damage, skin cancer can be a dangerous result.

Wrinkles and Sunspots While cancer builds up invisibly, UVA rays can make visible changes to your skin and appearance if you don’t protect your skin from their reach. Wrinkles, moles, sunspots, and more can be an unhappy consequence. While many people simply accept the inevitability of wrinkles, it’s important to know that sun exposure actually accounts for 85% of aging. You can protect yourself from many of the effects of

visible aging by keeping your skin safe from the sun.

Protect All the Time Because UVA rays can pass through glass, it’s important to wear sunscreen whenever you’ll be exposed to rays from the sun — whether you’re indoors or outdoors.

Sitting next to a window, or driving in a car, can even bring harmful rays your way. It makes sense to just add sunscreen to a part of your daily morning routine.

Cloudy days don’t protect against the harmful rays of the sun either.

While UVB rays may be blocked somewhat by clouds, UVA rays are capable of penetrating through the clouds straight to you.

Time Isn’t Always on Your Side The tricky thing about sun damage is you don’t see it happening. You see tans and sunburns, but you don’t see permanent sun damage until far later in life. This can make it hard to remain motivated to keep your skin protected, but it’s crucial that you learn to apply sunscreen regularly now to protect yourself in the future.