The Human Body
More Lessons for Biology
A series of free High School Biology Video Lessons.
Tissues and Organs
Tissues and organs are the basic structural units of our bodies. Tissues are collections of cells which serve the same function while organs are collections of tissues. Organ systems are composed of groups of organs with the same purpose and function. The types of tissues include epithelial, connective, nervous and muscle.
The relationships between tissues, organs, organ systems.
The digestive system controls the chemical and mechanical breaking down of food into molecules that can be used throughout the body. It includes organs such as the esophagus, stomach, and small and large intestines. There are two stages to the digestive system: mechanical and chemical. Mechanical digestion involves the physical breakdown of food while chemical digestion uses enzymes to break the chemical bonds holding polymers together.
Understanding the functions of the digestive system.
The muscular system includes all the muscles in an organism's body and allows organisms to move. A lot of the muscles in the muscular system of vertebrates are controlled by the nervous system. There are three types of muscle tissue. Skeletal (also known as striated) muscle provides body movement. Smooth muscles control automatic functions like breathing. Cardiac muscles make up the heart and allow it to pump blood through the circulatory system.
Understanding the functions of the muscle system.
The integumentary system is comprised of skin, hair, scales, feathers and nails. The integumentary system protects the body from physical damage and it is the largest organ system, mostly due to the volume of skin. Skin is composed of several layers. In skin, the top layer of skin is called the epidermis, the middle layer is called the dermis and the bottom layer is called the subcutaneous layer.
Understanding the functions of the integumentary system.
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