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Lecture 1: Body Organization Review
Teacher Notes

Organization of Our Body
We know that our bodies are organized on several levels. The most basic of these is at the level of the cell. The cell is a membrane covered structure that contains all of the materials necessary for life. At the cellular level we can see many of the same basic functions that our body does. The nucleus acts like the brain controlling the cell. The mitochondria is the power plant providing the energy for the cell. The cell membrane controls what enters or leaves the cell, protecting the cell much like the skin protects our body. The endoplasmic reticulum provides the system to move things through the cell like the cardiovascular system moves things through the body.
All of these body systems or cellular components work together to maintain a stable internal environment known as homeostasis. If homeostasis is disrupted, cells suffer and sometimes die. In the same way, if enough cells die off or enough body systems fail, we die.
Four Types of Tissue
Making sure your internal environment remains stable enough to support healthy cells is not an easy task. Many different jobs must be done to maintain homeostasis. Fortunately, not every cell has to do all of those jobs because the cells are organized into different departments or teams. Just as each member of a business has a specific role to keep the business running, each cell has a specific job in maintaining homeostasis. A group of cells working together forms a tissue. Your body contains four main types of tissue- epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
Epithelial Tissue- It is the job of the epithelial tissue to cover and protect the underlying tissues. They stick together closely with very little substance between them. Epithelial cells are often arranged in broad sheets or tube-like structures. Epithelium is commonly found on the surfaces of the body and organs, and the lining of body cavities, tubes, and ducts. This means that epithelial tissues characteristically have a free surface in contact with the environment.

Connective Tissue- As the name implies, connective tissue serves a "connecting" function. It supports, joins, protects, insulates, nourishes and cushions organs, and binds to other tissues. Its keeps organs from falling apart. Unlike epithelial tissue, connective tissue typically has cells scattered throughout an extra cellular matrix. What connective tissue made up of cells, cell parts and plasma did we study in the last unit?

BLOOD

Nervous Tissue- Nervous tissue is responsible for sensing "stimuli" and transmitting electrical "signals" to and from different parts of the body. It is found in the brain, nerves, and sense organs.

Muscle Tissue- Muscle tissue is made of "excitable" cells that are capable of contraction. Of all of the tissues discussed, muscle tissue is the most abundant tissue in most animals.

Tissues Form Organs
Two or more tissues working together form an organ. One type of tissue alone cannot do all the things that several types of tissue together can do. For example, your stomach uses several different tissues to carry out digestion. The stomach has epithelial tissue that line the inside of the stomach. It has layers of muscle tissue that crush and grind stomach contents. It two connective tissues, blood and collagen in the wall of the stomach that supply the stomach with oxygen and hold it together. The production of stomach acid and the contraction of the muscles are controlled by nervous tissue in the stomach. Also nervous tissue in the stomach sends signals to the brain that the stomach is full- "Stop eating, okay".
Skin is another organ. Note the different types tissues present in it. The epidermis is epithelial tissue. There is also connective tissue and nervous tissue present.

Organs Form Systems
The stomach does must to help you digest the food, but it doesn't do it all. It works together with other organs, such as the small and large intestines, to digest your food. Organs working together make up an organ system. The failure of any part of an organ system affects the entire organ system. Your body has 11 major organ systems.
System Some of the Organs Role
Integumentary System Skin, hair and nails Protects the underlying tissues.
Muscular System Skeletal Muscles Moves your bones.
Skeletal System Bones Provides a frame to support and protect body parts.
Cardiovascular System Heart and blood vessels Pumps blood to the body.
Nervous System Brain, nerves, spinal cord Sends and receives electrical messages throughout the body.
Lymphatic System Lymph vessels, lymph nodes, spleen, thymus, Returns leaked fluids to blood vessels. It also helps you get rid of germs that can harm you.
Digestive System Stomach, mouth, esophagus, intestines, anus Breaks down the food you eat into the nutrients that can be absorbed by the body.
Endocrine System Glands including the ovaries or testes Regulate body functions by sending out chemical messengers.
Respiratory System Mouth, nose, bronchi, trachea, pharynx, larynx, alveoli, lungs Absorb oxygen and release carbon dioxide.
Urinary System Bladder, kidneys Removes waste from the blood and regulates the body's fluids.
Reproductive System Male Testes Produces and delivers sperm.
Reproductive System Female
Ovaries, uterus Produces the eggs and nourishes and protects the unborn baby.