Endocrinology

ENDOCRINOLOGY -

This is the study of secretions that comes from inside There is also the so called Exocrine but this is not greatly used (exocrinology) The secretion comes from inside directly through the target glands without the use of no ducts or passageways Another name for endocrine is Ductless glands The secretion is called hormones The study of hormones of the ductless glands (study of secretion that is sent to the target glands)

The Major Endocrine Organs The major endocrine organs of the body include pituitary, thyroid, parathyroid, adrenal, pineal, thymus glands, the pancreas and the gonads (ovaries and testes). The hypothalamus which is part of the nervous system, is also recognized as a major endocrine organ because it produces several hormones. PITUITARY GLAND - A gland about 1 cm lodged into the sulla diaphragmatic sella (called sella turcica) - Devides into anterior (adenohypophysis) and posterior (neurohypophysis) *Hypothalamus – below the thalamus which send signals to the anterior pituitary so it could send all signals to the target glands *Hypothalamic – pituitary and whatever the target gland will be like: - thyroid gland (hypothalamic-pituitary-thyroid axis) - adrenals (hypothalamic-pituitary-adrenal axis_ gonads (hypothalamic-pituitary-gonadal axis) Examples: - Thyroid releasing hormone from the hypothalamus will stimulate the anterior pituitary to produce thyroid stimulating hormone which will stimulate the thyroid gland to produce T3 and T4 which will now go to all the tissues of the body. - Adrenals: with ACTH and with the hypothalamic factors that will affect the adrenals (called Adrenotropic releasing hormone which stimulates the adrenal gland to secrete its three secretions which are cortisone, aldosterone, and sex androgens) Hormones of the Anterior Pituitary - Growth hormone - Prolactin, something to do with lactation - Follicle stimulating hormone, stimulate follicle development in the ovaries, stimulate sperm develpment - Thyroid stimulating hormone (TSH), influences the the growth and activity of the thyroid gland.

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Luteinizing hormone (LH), triggers ovulation of an egg from female ovary and causes the ruptured follicle to become a corpus luteum, it also referred to as Interstitial cell-stimulating hormone (ICSH) because it stimulates testosterone production by the interstitial cells of the testes.

Hormones of the posterior Pituitary The posterior pituitary is not an endocrine gland in the strict sense because it does not make the peptide hormones it releases. Instead, it simply acts as a storage area for hormones made by hypothalamic neurons. - Oxytoxin, is released in significant amount only during childbirth and in nursing women. It stimulats powerful contractions of the uterine muscle during labor, during sexual relations, and when a women breast-feeds her baby. It also causes milk ejection (the letdown reflex) in a nursing woman. - Antidiuretic hormone (ADH), Diuresis is urine production. Thus antidiuretic is a chemichal that inhibits or prevent urine production. ADH causes the kidneys to reabsorb more water from the forming urine, as a result, urine volume decreases and blood volume increases.