Endocrine and Immune Systems - NCLEX-PN

The pituitary is located just below the hypothalamus. The pituitary and the hypothalamus are connected by nerves and maintain an important working relationship with one another. Both are located near the base of the brain.

Lysozymes are a group of defense enzymes found in tears, saliva, mucus, and breast milk. It is considered part of our innate immune systems, as its presence in tears prevents infectious conjunctivitis. Cathelicidin, Defensin-5, and DEFA1 are found in the lysosomes of polymorphonuclear leukocytes (PMN's) and macrophages.

Interleukins (IL) are cytokines that play a role in signaling the immune cells. IL-8 is produced mainly by macrophage and dendritic cells and plays a major role in inflammation as a chemoattractant for neutrophils. IL-1 and IL-6 both induce acute phase proteins. TNF-alpha is involved in the acute phase reaction. It is an endogenous pyrogen (meaning it induces fever) and is also involved in apoptosis and tumor inhibition.

Major histocompatibility complex 1 in a membrane protein that binds to peptide fragments from pathogens such as viruses and bacteria and then displays them on the cell surface in order to alert other immune cells of the presence and nature of infection.

All cells with nuclei express MHC-1. Red blood cells do not have nuclei, and do not express MHC-1 on membranes.

Antibodies are only produced by B cells, specifically by a type of specialized B cell called a plasma cell. B cells belong to a broader category of leukocytes known as lymphocytes, which are agranulocytes.

T lymphocytes are so titled because they mature in the thymus, unlike B lymphocytes, which mature in the bone marrow. The thymus is located in the anterior superior mediastinum, ventral to the heart and dorsal to the sternum. It is most active in the neonatal and pre-adolescent periods, afterwards, it degenerates and is replaced with adipose tissue.

Lymphoid progenitor cells are produced in all of the following tissues: the liver, the bone marrow, spleen, and gut associated lymphoid tissue (mainly found in the liver and intestines). However, note that the vast majority of all blood cells are produced in the red bone marrow of long bones by hematopoietic stem cells.

Mast cells are rich in granules that contain high concentrations of heparin, histamine, and trypsin, among other preformed proteases. These granules also contain serotonin and various eicosanoids. The function of mast cells is primarily to regulate immune (inflammatory) responses to allergens.

While all of the cells listed may have some indirect involvement in the overall response to a parasitic infection, eosinophils are the only immune cells that are specialized to respond to multicellular parasites, especially helminths such as hookworms and pinworms.

Calcitonin is produced by the parafollicular (c cells) of the thyroid as a response to elevated blood calcium levels. Calcitonin reduces plasma calcium by inhibiting osteoclast activity and stimulating osteoblasts to deposit more bone. Parathyroid hormone has the opposite effect - it acts to increase calcium levels when serum calcium decreases. While they may ultimately affect serum calcium levels, thyroid hormone and cortisol are not directly involved in calcium homeostasis.

Thyroid-stimulating hormone (TSH) is produced in the anterior pituitary. Somatostatin, dopamine, and gonadotropin releasing hormone are all hypothalamic hormones. Somatostatin is also secreted by the pancreas, and slows down digestive processes. To remember the hormones of the anterior pituitary, use the following mnemonic: FLAT PEG, Follicle-stimulating hormone, Luteinizing hormone, Adrenocorticotropic hormone, Thyroid-stimulating hormone, Prolactin, Endorphins, Growth hormone.

Macrophages, the main blood cells responsible for phagocytosis of debris, bacteria, and virally infected cells, are part of the nonspecific immune response. While they are able to recognize self versus non-self proteins, they are not uniquely sensitive to any particular non-self protein type. Rathe, they phagocytose foreign matter as well as cellular debris. Plasma cells, memory cells, and CD8 T cells are all lymphocytes, and as such they are all part of the adaptive or "specific" immune system, meaning that they are uniquely sensitive to particular pathogenic proteins.

While all of the enzymes listed are present in saliva, lysozyme is the only enzyme listed that has antibacterial properties. This enzyme, present not only in saliva but also in tears, sweat, and breast milk, damages bacterial cell walls, making it an important part of the innate immune system. Amylase breaks down carbohydrates, lipase breaks down lipids, and kallikrein breaks down proteins.

Calcitonin is produced by the thyroid gland. The hormone plays an important role in lowering blood calcium levels. It is also synthesized as a drug and used in the treatment of hypercalcemia. The other three hormones are indeed secreted by the islets of Langerhans in the pancreas. Insulin, secreted by the beta cells lowers blood sugar, glucagon, secreted by the alpha cells, increases blood sugar, and somatostatin, secreted by the gamma cells regulates digestive and metabolic processes. Lipase is not a hormone, but an enzyme that facilitates the breakdown of lipids. The pancreas does indeed secrete lipase.

Selenium is essential for conversion of T4 to T3. Deiodinase enzymes, which remove iodine from T4 during conversion into T3, are selenium dependent. Tyrosine and iodine are both required for synthesis of T4, and iron is the cofactor for conversion of phenylalanine into tyrosine.

The nutrients specifically required for thyroid hormone production are tyrosine, iodine, and selenium, in addition to zinc and several B vitamins. While magnesium, manganese, and methionine are all essential for metabolism and overall hormone production, they are not direct substrates or cofactors in the production of thyroid hormone.

Tyrosine and iodine are both precursors for synthesis of T4. Selenium is essential for conversion of T4 to T3, and iron is the cofactor for conversion of phenylalanine into tyrosine.

Oxytocin is produced by the hypothalamus, and is released by the posterior pituitary. Women experience an increased level of oxytocin during labor, after birth, and while breastfeeding. It helps to increase uterine contractility, aiding in the delivery process and preventing hemorrhage after birth. Progesterone and estrogen are hormones released from the ovary. Estrogen is has many effects on the body, one of which is the development of sex characteristics in females. Progesterone is important in regulation of the uterine lining. Prolactin is made by the anterior pituitary gland and functions in the production on breast milk.

Epinephrine is the only hormone of those listed that is produced by the adrenal medulla. The adrenal medulla is the center of the adrenal gland. Antidiuretic hormone is produced by the posterior pituitary. Calcitonin is produced by the thyroid. Thyroid-stimulating hormone is secreted from the anterior pituitary, as is follicle-stimulating hormone.