San Diego has on average 146 sunny days and 117 partly cloudy days a year. The average annual precipitation is less than 12 inches (300 mm), resulting in a borderline arid climate.
Skeletal muscle makes up the bulk of muscles in the body. See also skeletal muscle groups. A whole skeletal muscle is considered an organ of the muscular system. Each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue. Skeletal muscles vary considerably in size, shape, and arrangement of fibers.
An organ is a group of different kinds of tissues working together to perform a particular activity. The heart is an organ composed of muscle, nervous, connective, and epithelial tissues. An organ system is two or more organs working together to accomplish a particular task. The digestive system, for example, involves the coordinated activities of many organs, including the mouth, stomach, small and large intestines, pancreas, and liver.