Body Organs

Together with the brain, the spinal cord constitutes an important part of the central nervous system. It conducts impulses between the brain and the rest of the body and is a center for reflex activity. The spinal cord is present in the vertebral column of all vertebrate animals, running from the brain stem to the tail. The spinal cord consists of a tube about 1 cm thick with a small central canal. Cerebrospinal fluid flow through this canal and around the spinal cord. The cord is encased in three membranes called meninges; the pia mater, the arachnoid, and the dura mater. In cross section, the spinal cord has centrally positioned butterfly shaped gray matter, consisting of unmyelinated cell bodies of nerve cell (neurons), surrounded by the myellinated axonal fibers, or white matter. A cell body contains the nucleus of the nerve cell, and it sends out a single axon and numerous fibrous extensions known as dendrites. In the spinal cord, dendrites receive stimuli from the axons of ot

Breast, in human females, are two glandular organs that secret milk for feeding newborn infants. Such gland are present in all mammals and are known in general as mammaries. Physiologycally, they are highly modified sweet glands. No other animals posses such glands, and no related precedents exist in other classes of vertebrates. Rudimentary breasts are present in both human sexes at birth. No further development takes place in males during normal growth, but full development occurs in females in the early childbearing period. A projection called a nipple is found at the tip of each breast in both men and women. It is surrounded by a pigmented areas, the areola, that enlarges and deepens in color on pregnancy. Structure The female human breast consists mainly of a round mass of glandular tissue comprising about 15-20 lobes, each having a duct leading to an opening on the nipple, the duct system and glandular tissue fully develop with pregnancy. The amount of fat sheathing the glan