Astronomical unit usually refers to that unit which represents the mean distance starting from the center of the earth to the center of the sun. The distance from the sun to all the planets and other astronomical bodies are represented in the astronomical unit. It is denoted by AU. This unit is mainly used by the Planetary scientists and the Astronomers, as it is helpful in understanding the relative distance between two objects in the solar system.
Areas where the air is warmed often have lower pressure because the warm air rises. These areas are called low pressure systems. Places where the air pressure is high, are called high pressure systems. A low pressure system has lower pressure at its center than the areas around it.
The periosteum is a dense fibrous membrane that covers the surfaces of bones.
The periosteum consists of two layers-
1. Outer fibrous layer
2. Inner cellular layer
It is mainly composed of dense irregular connective tissue along with a layer of simple squamous epithelium.
The function of periosteum is to cover the surface of all the bones except those surfaces that are covered with cartilage such as joints and tendons and ligaments.
