Skeletal System
Muscular System
Integumentary System

By Harli Henderson, Sandy Henderson, Yujeena Khadka, and Adhithi Baskar


Skeletal System

The functions of the skeletal system are to support the body, protect internal organs, provide for movement, store mineral reserves, and provide a site for blood cell formation.

Muscular System

The function of the muscular system is to help the body with voluntary and involuntary movement.

Integumentary System

The functions of the integumentary system are to serve as a barrier against infection and injury, help regulate body temperature, remove waste products of the body, and provide protection from U.V. radiation from the sun. This system includes hair, skin, and nails.

Axial vs. Appendicular

The axial skeleton supports the central axis of the body, such as the skull, vertebral column, the rib cage, and the sternum.

The appendicular skeleton consists of the arms, legs, pelvis, and shoulder area.

In the diagram below, the axial skeleton is represented by blue, and the apendicular skeleton is represented by yellow.

How do Bones Develop?

Bones begin to develop before birth. When bones are first formed they are made of flexible cartilage and after a few weeks the process of ossification begins. This is when hard deposits of calcium, phosphate, and stretchy collagen replace the cartilage which forms bones.

Bone Cells

Osteoblasts- A bone cell located on the surface of the bone. This bone cell holds everything together and forms a new tissue. They also secrete a bone matrix composed of mineral salt and collagen.

Osteocytes- A bone cell that is mature and trapped in their own matrix, deeper in the compact bone. Osteocytes are responsible for keeping the bone in shape and together. For example, if you break a home, osteocytes will work together to try to heal it.

Osteoclasts- This bone cell is a white blood cell that breaks down the matrix, and is regulated by hormones. It is responsible for bone remodeling, healing, and releasing calcium into the blood.

Muscle Tissue

Skeletal muscle- Skeletal muscles are responsible for voluntary movements such as running, writing, and typing. Skeletal muscles are usually attached to a bone and consists of blood vessels, muscle fibers, connective tissues, and nerves.

Smooth muscle- Unlike skeletal muscles, smooth muscles are responsible for involuntary movements. Smooth muscles are found in the walls of hollow structures such as the stomach, intestines, and arteries

Cardiac muscle- Cardiac muscles are ONLY found in the heart. Cardiac muscles contract to squeeze blood out of your heart, and relax to fill your heart with blood.  

Muscle Contraction

During muscle contraction, the thin filaments slide past the thick filaments, shortening the sarcomere. A sarcomere is the basic unit of muscle. The thick and thin filaments do the actual work of the muscle. The thick filament is made up of a protein called myosin. At the molecular level, a thick filament is shaft of myosin molecules arranged in a cylinder. The thin filament is made up of another protein called actin. The thin filament looks like two strands of pearls twisted around each other.


Muscles attach to bones by strong fibrous connective tissue. It can be directly through muscle fascicles or indirectly through tendons.


Purpose of Skin

Skin serves so many purposes. It protects your inner organs from harmful elements, keeps you warm and cool, protects against infections, transforms sunlight into vitamin D, and much more. Two of the many cells in the layers of the skin, keratin and melanin are composed of proteins called keratinocytes and melanocytes.

Dermis and Epidermis

The dermis is the middle layer of the skin and is held together by a protein called collagen. This layer keeps the epidermis healthy and growing. This layer lies right below the epidermis and contains nerve endings, blood vessels, oil glands, and sweat glands.        

The epidermis is the top layer of the skin. It's primary function is to provide protection to the surfaces it is covering.         

The dermis is connective tissue while the epidermis is epithelial tissue.                              


Muscular System: Duchenne Muscular Dystrophy

  • Duchenne Muscular Dystrophy is genetically inherited from parent to kid. It is found on the short hand of the X- chromosome and it is a recessive gene. This disease primarily effects boys at younger ages.
  • Symptoms- Weakening muscles, drooping eyelids, curved spine, and difficulty walking and maintaining balance
  • This disease effects the calcium level in your body. The organs this disease can affect are the muscles, heart, skin, and eyes.
  • There are a few systems this disease can affect, and those are the nervous system, respiratory system, and circulatory. The muscles consist of nerve cells, and the damaging muscle can in turn damage those cells. For the respiratory system and circulatory system, if the disease starts to damage the heart or lung muscles, that could damage those muscles.
  • This disease doesn't typically affect a certain ethnicity, but it does somewhat affect a certain age group. It typically affects younger males.
  • There is no way to prevent muscular dystrophy, as it is a genetically inherited disease. There is also no cure for this disease. To treat it, patients go through therapy such as limb stretching. Dystrophy can also be treated with medications to lessen the pain. The only new advances in treatment for this disease is a powerful medication. However this medicine is controversial and very risky to take.

In the picture above, to the left are what the muscles look like without Muscular Dystrophy and to the right is what the muscles look like with Muscular Dystrophy.

Integumentary System: Melanoma

  • This disease is not genetically inherited, it is caused by ultraviolet radiation from sun rays or tanning beds causing unrepaired DNA damage to skin cells which trigger genetic defects that eventually lead to malignant tumors.
  • Symptoms- A change in an existing mole and development of a new pigmented or unusual looking growth on your skin
  • When melanoma forms, it effects pigmentation of the skin and the protection against UV radiation. This disease can effect the eye, lymph nodes, liver, lungs, and the brain.
  • The many systems that this disease can affect are the lymphatic system, digestive system, respiratory system, and the nervous system.
  • This disease does not affect a certain age group or ethnicity. To not contract this disease, you need to take care of your skin.
  • To avoid getting Melanoma, avoid tanning and UV tanning booths, and use broad spectrum sunscreen. This disease can be cured with surgery, radiation therapy, chemotherapy, and biological therapy. A new type of treatment is mixing an immune therapy, ipilimumab, with another, GM-CSFhelped patients with advanced melanoma live longer than those who got just ipilimumab alone.


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