Endocrine System PDF

Endocrine system By Asmaa sabry bassit The endocrine system is made up of glands that produce and secrete hormones (chemical substances produced in the body that regulate the activity of cells or organs). The major glands of the endocrine system are; The hypothalamus, pituitary gland, and p...

Endocrine system By Asmaa sabry bassit The endocrine system is made up of glands that produce and secrete hormones (chemical substances produced in the body that regulate the activity of cells or organs). The major glands of the endocrine system are; The hypothalamus, pituitary gland, and pineal gland are in your brain. he thyroid and parathyroid glands are in your neck. The thymus is between your lungs. The adrenals are on top of your kidneys. The pancreas is behind your stomach. ovaries or testes. The hypothalamus: The hypothalamus is a small region of the brain. It’s located at the base of the brain, near the pituitary gland. Anatomy and function The hypothalamus has four main regions. Each one contains different nuclei. These are clusters of neurons that perform vital functions, such as releasing hormones.  Preoptic region Four nuclei in this region, (medial, median, lateral, and periventricular). It is responsible for thermoregulation( keep body temperature within certain boundaries) and sleep regulation  Anterior region (supraoptic region): Its major nuclei include the supraoptic and paraventricular nuclei. There are several other smaller nuclei (anterior-suprachiasmatic ) in the anterior region as well. Some of the most important hormones produced in the anterior region include: Corticotropin-releasing hormone (CRH). It sends signals to the pituitary gland to produce a hormone called adrenocorticotropic hormone (ACTH). ACTH triggers your adrenal glands to produce cortisol, an important stress hormone. Thyrotropin-releasing hormone (TRH). TRH production stimulates the pituitary gland to produce thyroid-stimulating hormone (TSH). Gonadotropin-releasing hormone (GnRH).GnRH production causes the pituitary gland to produce important reproductive hormones, such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Oxytocin. This hormone controls many important behaviors and emotions, such as sexual arousal, trust, recognition, and maternal behavior. It’s also involved in some functions of the reproductive system, such as childbirth and lactation. Vasopressin. Also called antidiuretic hormone (ADH), this hormone regulates water levels in the body. When vasopressin is released, it signals the kidneys to absorb water. Somatostatin. works to stop the pituitary gland from releasing certain hormones, including growth hormones and thyroid-stimulating hormones.  Middle(Intermediate ) region (tuberal region). Its major nuclei are the ventromedial , dorsomedial and arcuate nuclei. The ventromedial nucleus helps control appetite. While the arcuate nucleus is involved in releasing growth hormone-releasing hormone (GHRH). Which stimulates the pituitary gland to produce growth hormone. This is responsible for the growth and development of the body..  Posterior region (mammillary region). The posterior hypothalamic nucleus and mammillary nuclei are its main nuclei. The posterior hypothalamic nucleus helps regulate body temperature by causing shivering and blocking sweat production. The mammillary nuclei involved in memory function as part of the limbic system Function of hypothalmus releasing hormones regulating body temperature maintaining daily physiological cycles controlling appetite managing of sexual behavior regulating emotional responses. Blood supplyof hypothalmus Arterial supply: The hypothalamus is supplied by the circle of Willis, which surrounds it inferiorly. the anteromedial branches of the anterior cerebral artery the posteromedial branches of the posterior communicating artery and the thalamoperforating branches of the posterior cerebral artery. Venous drainage is largely via the circle of intercavernous sinuses.  HypophysisCerebri (Pituitary Gland-master endocrine gland) Position: a small and oval- shaped. It’s located behind the nose in the hypophyseal fossa (sella turcica). Attached to the undersurface of the brain by the infundibulum (pituitary stalk). The pituitary gland can be divided into two different parts: the anterior and posterior lobes.1.Anterior lobe: produce and release different types of hormones, including: 1. Growth hormone: Regulates growth and physical development. It can stimulate growth in almost all of your tissues. Its primary targets are bones and muscles. 2. Thyroid-stimulating hormone: activates your thyroid to release thyroid hormones. 3. Adrenocorticotropic hormone: Stimulates your adrenal glands to produce cortisol and other hormones. 4. Follicle-stimulating hormone: involved with growth of egg cells in women. It’s also important for sperm cell production in men. 5. Luteinizing hormone: involved in the production of progesterone in women and testosterone in men. 6. Prolactin: helps women who are breastfeeding produce milk. 7. Endorphins: have pain-relieving properties and are thought to be connected to the “pleasure centers” of the brain.  2. Posterior lobe: also secretes hormones. These hormones are usually produced in your hypothalamus and stored in the posterior lobe until they’re released and include: Vasopressin: This is also called antidiuretic hormone. Oxytocin. Blood Supply: The arteries are derived from: The superior and inferior hypophyseal arteries; Branches of the internal carotid artery. The veins drain into the intercavernous sinuses. Hypophyseal portal system: The system of blood vessels that links the hypothalamus and the anterior pituitary (adenohypophysis). This capillary network is a part of the hypophyseal portalsystem which carries substances from the hypothalamus to the anterior pituitary and hormones from the anterior pituitary into the circulatory system. A portal system carries blood from one capillary network to another; therefore, the hypophyseal portal system allows hormones produced by the hypothalamus to be carried directly to the anterior pituitary without first entering the circulatory system. Pineal body: This is a midline, unpaired structure Located between the two cerebral hemispheres. It is attached by a stalk to the posterior wall of third ventricle. In close proximity to the gland are the superior colliculi of the midbrain.  It is involved with reproductive cycles. It secretes a hormone called melatonin at relatively high rates during darkness. By the age of 17, calcification occurs in it (brain sand). This makes it opaque to x-rays, hence making it a useful radiological landmark. The arterial supply to the pineal gland is profuse.