Basic Anatomy - Tissues and Organs

In middle school science you'll learn about cells and cell structure. In the body, when you group together related cells they form what is known as tissues. The human body is made up of 4 primary tissues known as the epithelial tissue, the connective tissue, the muscle tissue and the nerve tissue. Now let’s see how each is important and how they work.

The Epithelial Tissue is the grouping of related cells that form a kind of lining over different parts of the human body. This lining helps to keep the different organs separated. It also helps to protect the organs. Examples of the epithelial tissue include the outer layer of skin, the lining inside of the mouth and the lining found in the stomach.

The Connective Tissue is the grouping of related cells that actually give the body support and structure as the connective tissue contains fibrous strands of protein collagen. Examples of connective tissues include the inner layers of the skin, tendons, cartilage, ligaments and bone and fat tissue. In addition, the blood is also a form of the connective tissue.

The Muscle Tissue is the grouping of related cells that contain proteins actin and myosin that slide past one another. This allows the body to be more flexible and it is found in virtually every muscle of the body.

The Nerve Tissue is the grouping of two related cells known as the neurons and glial cells. The nerve tissue actually has the ability to generate and conduct electrical signals in the body that send messages to the brain and down the spinal cord. These signals tell us to walk, sit, talk, breathe, sleep, eat, smile, cry, etc.

After the 4 primary tissues we next turn to the body’s organs. An organ is a structure that will contain at least two different types of tissues. Just as we have different tissue types, the body contains many different organs that all have a specialized function. These organs include the liver, the kidneys, the lungs, the heart, the pancreas, the stomach and the skin. Did you know that the skin is actually the largest of all the organs?

The skin has three layers to it. There is the epidermis which is the outermost layer, the dermis which is the connective tissue just below the epidermis and it contains blood vessels that nourish the skin and it contains nerve tissues that provide feelings in the skin, and then there is the subcutaneous layer which lies below the dermis. The subcutaneous layer is made up of mostly connective tissue called adipose tissue which is more commonly known as fat. It helps to cushion the skin and protect it from extremes in temperature.

Organ Functions

Each organ, besides the skin, has a specific function that it must perform. There are many organs but we will focus on the liver, the kidneys, the lungs, the heart, the pancreas and the stomach.

The liver’s main function is to produce bile by breaking down fats converted to glucose (sugars). It also filters harmful substances from the blood such as alcohol and it absorbs vitamins and minerals responsible for producing cholesterol.

The kidneys filter blood plasma by separating it from waste. It also regulates the body’s blood pressure. The kidneys’ main responsibility, in short, is to keep the blood clean.

The lungs of the body (in which there are two) help to provide the body with oxygen and they expel carbon dioxide which is bodily waste produced by cellular metabolism.

The heart pumps blood throughout the body. The circulation of the blood contains oxygen and food for the cells and other organs of the body.

The pancreas is part of the digestive system and it secretes enzymes needed to digest starch. It also secretes insulin which helps maintain the blood sugar level of the body.

The stomach is also part of the digestive system. It is where food is stored and broken down. The stomach acid and enzymes also help to kill bacteria and other infectious organisms that a person may have eaten. The stomach is coated with a mucus layer that keeps the stomach acids from leaking into the body as the stomach acid can damage other body organs.