Introduction to the Body
Body Structure
Before you're able to move on and concentrate on the body systems and their functions, you need a general understanding of the body as a whole together with it's basic structures and arrangement.
The Cell
The cell is one of the most basic units of life. The cell is the smallest unit of life in our bodies. In the body, there are brain cells, skin cells, liver cells, stomach cells, and the list goes on. All of these cells have unique functions. And all have some recognisable similarities.
- Plasma Membrane:The cytoplasm of cells is bounded by a membrane referred to as the cell membrane or plasma membrane. Besides giving a cell shape and strength, the cell membrane is differentially permeable, allowing some materials to pass through while preventing others from doing so. With regard to molecules, the cell membrane is very permeable to water, oxygen, amino acids, and sugars, but relatively impermeable to large molecules such as proteins.
- Cytoplasm: Cytoplasm is the watery environment inside the cell. This extra cellular fluid consists of all of a cell's internal contents, and is mostly made of water.
- Nucleus: At the centre of the cell is the cell nucleus. The cell nucleus contains the cell's DNA, the genetic code which determine cellular structure and function.
- Other Intracellular Structures: In addition to the nucleus, there are many organelles inside of the cell - small structures that help carry out the day-to-day operations of the cell. For example, Ribosomes participate in protein production and Mitochondria referred to as the "power plant" of the cell because many of the reactions that produce energy take place in mitochondria
- 1. Nucleolus
- 2. Nucleus
- 3. Ribosome
- 4. Vesicle
- 5. Rough endoplasmic reticulum
- 6. Golgi apparatus (or "Golgi body")
- 7. Cytoskeleton
- 8. Smooth endoplasmic reticulum
- 9. Mitochondrion
- 10. Vacuole
- 11. Cytosol
- 12. Lysosome
- 13. Centriole
Complex Cell Structure
Cells need three main substances to allow them to function correctly:
- Oxygen: Most chemical activity within the body requires the presence of oxygen.
- Nutrition: Is required in the form of carbohydrates, fats and protein to produce energy and to build and repair cells
- Water: Water is the main substance for all chemical activity within the body
Tissues
Cells group together in the body to form tissues - a collection of similar cells that group together to perform a specialized function. There are 4 primary tissue types.
- Epithelial: Form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands. They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception. Epithelial cells may be squamous, cuboidal, or columnar in shape and may be arranged in single or multiple layers.
- Connective: tissues bind structures together, form a framework and support for organs and the body as a whole, store fat, transport substances, protect against disease, and help repair tissue damage.
- Nervous: tissue is found in the brain, spinal cord, and nerves. It is responsible for coordinating and controlling many body activities.
- Muscle: tissue is composed of cells that have the special
ability to shorten or contract in order to produce movement
of the body parts.
Muscle tissue can be categorized into
skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue.
Organs
Organs are the next level of organisation in the body. Organs are more complex units than tissues. An organ is a structure of several different types of tissues so arranged that together they can perform a special function. There are many different organs in the body: the liver, kidneys, heart, even your skin is an organ.
System
A system is an organisation of two or more organs that arranged together they can perform complex functions for the body. There are 10 major organ systems in the human body. The following are the systems that we'll cover on this site:
- Skeletal
- Muscular
- Nervous
- Cardiovascular
- Respiratory
- Digestive
Those not covered are:
- Excretory
- Endocrine
- Reproductive
- Lymphatic/Immune