Tag: pineal gland and thymus

The thymus gland, located behind our sternum and between our lungs, is only active until puberty.

Central tolerance is the tolerance established by deleting autoreactive lymphocyte clones before they develop into fully grown immunocompetent cells. It occurs primarily in the thymus.

B cells develop in the bone marrow but achieve maturity in peripheral lymphoid organs. Developmental stages are defined by the successful expression of heavy-chain and light-chain immunoglobulin genes. B cells provide humoral immunity against extracellular pathogens through antibody production. Antibodies neutralize pathogens and toxins, facilitate opsonization, and activate complement. The B-cell receptor or BCR is composed of immunoglobulin molecules that form a type 1 transmembrane receptor protein usually located on the outer surface of a lymphocyte type known as B cells. 

The pineal gland is a small endocrine gland in the vertebrate brain. It produces melatonin, a serotonin derived hormone, that affects the modulation of sleep patterns in both seasonal and circadian rhythms.

The diencephalon is the region of the embryonic vertebrate neural tube that gives rise to posterior forebrain structures including the thalamus, hypothalamus, posterior portion of the pituitary gland, and pineal gland. The pineal gland arises as a dorsal outgrowth of the caudal portion of the diencephalon. In the adult animal, it lies in the midline of the roof of the third ventricle. 

Serotonin is the hormone that contributes the feeling of well being and happiness in animals including humans. It is basically derived from tryptophan and is located in the gastrointestinal tract (GI tract), blood platelets and central nervous system. 90% of the total serotonin is primarily located in GI tract in Enterochromaffin cells and used for regulation of intestinal movements. Hence, answer D is correct.

Pinealocytes are the main cells contained in the pineal gland, located behind the third ventricle and between the two hemispheres of the brain. The primary function of the pinealocytes is the secretion of the hormone melatonin, important in the regulation of circadian rhythms.

The pineal gland or epiphysis synthesizes and secretes melatonin hormone, that communicates information about environmental lighting to various parts of the body. It is attached to the roof of third ventricle in the rear part of brain. It functions as a biological clock and a neurosensory transducer, converting the neural information.