A phagocytic white blood cell.

The internal section of an organ, or the medulla oblongata of the mammalian hindbrain. This would be the part of the brain stem closest to the spinal cord, and controls functions such as breathing and heartbeat.

A process of cell division in which two successive nuclear divisions produce four haploid gametes from one diploid germ cell.

Alleles segregate during meiosis.

Alleles of unlinked genes independently sort during meiosis.

The three membranes covering the brain and spinal cord: dura mater, arachnoid, and pia mater

The cyclic, physiologic discharge through the vagina of blood and muscosal tissues from the nonpregnant uterus; it is under hormonal control and normally recurs usually at approximately four-week intervals, except during pregnancy and lactation, throughout the reproductive period (puberty through menopause).

The middle of the three primary germ layers of the embryo, lying between the ectoderm and endoderm; from it are derived the connective tissue, bone, cartilage, muscle, blood and blood vessels, lymphatics, lymphoid organs, notochord, pleura, pericardium, peritoneum, kidneys, and gonads.

RNA, synthesized from a DNA template during transcription, that mediates the transfer of genetic information from the cell nucleus to ribosomes in the cytoplasm, where it serves as a template for protein synthesis. Also called messenger RNA.

The complex of physical and chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.

A change in the form and often habits of an animal during normal development after the embryonic stage. Metamorphosis includes, in insects, the transformation of a maggot into an adult fly and a caterpillar into a butterfly and, in amphibians, the changing of a tadpole into a frog.

The second stage of cell division (mitosis or meiosis), in which the chromosomes, each consisting of two chromatids, are arranged in the equatorial plane of the spindle prior to separation.