Skeletal System(Bones), Muscular System (Muscles), and Integumentary System (Skin)

Organization and Homeostasis Homeostasis is the body’s way of maintaining proper balance; the body regulates temperature, energy, oxygen levels through homeostasis.

Levels of Organization Each part of an organism has a specific job to do, and all the different parts work together. The different parts function smoothly due partly to the way in which the bodies of organisms are organized. The levels of organization in complex organisms, including most plants and animals, consist of cells, tissues, organs, and organ systems. The smallest unit of organization is the cell, and the largest is the organism.

Cells: Structures and Function A cell is the basic unit of structure and function in a living thing. An organism’s structure is its body plan, or the way its parts are arranged. The function of a part of an organism is its job, or the process it carries out. Cells carry on the processes that keep organisms alive. They also get rid of waste products, grow and reproduce.

Cell Structure Structure: The cell membrane forms the outside boundary of the cell. The nucleus is the control center that directs the cell’s activities and contains information that determines the cell’s characteristics. The area between the cell membrane and the nucleus is the cytoplasm. Cytoplasm contains a clear, jellylike substance in which many important cell structures, called organelles are found.

Tissues Tissue is the next largest unit of organization in complex organisms. A tissue is a group of similar cells that perform the same function. An animal’s body contains four basic types of tissue: muscle tissue, nerve tissue, connective tissue, and epithelial tissue.

Muscle Tissue Muscle tissue can contract, or shorten. By doing this, muscle tissue functions to make parts of the body move.

Nerve Tissue Nerve tissue directs and controls muscle tissue. It carries messages back and forth between the brain and every other part of the body. The brain is made up mostly of nerve tissue.

Connective Tissue Provides support for the body and connects all its parts. Bone is one type of connective tissue. Fat is also a connective tissue.

Epithelial Tissue Covers the surfaces of the body, inside and out. Some epithelial tissue protects delicate structures that lie beneath it (i.e. the skin). Other epithelial tissue absorbs or releases substances (i.e. the lining of the digestive system).

Organ and Organ Systems An organ is a structure that is composed of different kinds of tissue (i.e. stomach, heart, brain, bones, lungs) Like tissue, an organ has a specific function. Each organ in the body is part of an organ system, a group of organs that work together to perform a major function.

Skeletal System Major Role: The main role of the skeletal system is to provide support for the body, to protect delicate internal organs and to provide attachment sites for the organs. Major Organs: Bones, cartilage, tendons and ligaments.

Muscular System Major Role: The main role of the muscular system is to provide movement.  Muscles work in pairs to move limbs and provide the organism with mobility.  Muscles also control the movement of materials through some organs, such as the stomach and intestine, and the heart and circulatory system.  Major Organs: Skeletal muscles and smooth muscles throughout the body.

Circulatory System Major Role: The main role of the circulatory system is to transport nutrients, gases (such as oxygen and CO2), hormones and wastes through the body. Major Organs: Heart, blood vessels and blood.  

Nervous System Major Role: The main role of the nervous system is to relay electrical signals through the body.  The nervous system directs behavior and movement and, along with the endocrine system, controls physiological processes such as digestion, circulation, etc.  Major Organs: Brain, spinal cord and peripheral nerves.

Respiratory System Major Role: The main role of the respiratory system is to provide gas exchange between the blood and the environment.  Primarily, oxygen is absorbed from the atmosphere into the body and carbon dioxide is expelled from the body. Major Organs: Nose, trachea and lungs.

Digestive System Major Role: The main role of the digestive system is to breakdown and absorb nutrients that are necessary for growth and maintenance. Major Organs: Mouth, esophagus, stomach, small and large intestines

Excretory System Major Role: The main role of the excretory system is to filter out cellular wastes, toxins and excess water or nutrients from the circulatory system.  Major Organs: Kidneys, ureters, bladder and urethra.

Endocrine System Major Role: The main role of the endocrine system is to relay chemical messages through the body.  In conjunction with the nervous system, these chemical messages help control physiological processes such as nutrient absorption, growth, etc. Major Organs: Many glands exist in the body that secrete endocrine hormones.  Among these are the hypothalamus, pituitary, thyroid, pancreas and adrenal glands.