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In addition, the pituitary secretes hormones that signal the reproductive organs to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women. The posterior lobe of the pituitary releases antidiuretic pronounced: THY-royd , located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxine pronounced: These hormones control the rate at which cells burn fuels from food to produce energy.
The production and release of thyroid hormones is controlled by thyrotropin pronounced: The more thyroid hormone there is in a person's bloodstream, the faster chemical reactions occur in the body. Why are thyroid hormones so important? There are several reasons — for example, they help kids' and teens' bones grow and develop, and they also play a role in the development of the brain and nervous system in kids.
Attached to the thyroid are four tiny glands that function together called the parathyroids pronounced: They release parathyroid hormone , which regulates the level of calcium in the blood with the help of calcitonin pronounced: The body also has two triangular adrenal pronounced: The adrenal glands have two parts, each of which produces a set of hormones and has a different function:. It secretes melatonin pronounced: The gonads are the main source of sex hormones.
Most people don't realize it, but both guys and girls have gonads. In guys the male gonads, or testes pronounced: TES-teez , are located in the scrotum. They secrete hormones called androgens pronounced: AN-druh-junz , the most important of which is testosterone pronounced: These hormones tell a guy's body when it's time to make the changes associated with puberty , like penis and height growth, deepening voice, and growth in facial and pubic hair. Working with hormones from the pituitary gland, testosterone also tells a guy's body when it's time to produce sperm in the testes.
A girl's gonads, the ovaries pronounced: OH-vuh-reez , are located in her pelvis. They produce eggs and secrete the female hormones estrogen pronounced: ESS-truh-jen and progesterone pronounced: Estrogen is involved when a girl begins to go through puberty. During puberty, a girl will experience breast growth, will begin to accumulate body fat around the hips and thighs, and will have a growth spurt. Estrogen and progesterone are also involved in the regulation of a girl's menstrual cycle.
These hormones also play a role in pregnancy. Although the endocrine glands are the body's main hormone producers, some other organs not in the endocrine system — such as the brain, heart, lungs, kidneys, liver, and skin — also produce and release hormones. PAN-kree-us is also part of the body's hormone-secreting system, even though it is also associated with the digestive system because it produces and secretes digestive enzymes.
The pancreas produces in addition to others two important hormones, insulin pronounced: IN-suh-lin and glucagon pronounced: Situated in a small depression in the sphenoid bone called the sella turcica, the pituitary gland is actually made of 2 completely separate structures: The posterior pituitary gland is actually not glandular tissue at all, but nervous tissue instead. The posterior pituitary is a small extension of the hypothalamus through which the axons of some of the neurosecretory cells of the hypothalamus extend.
These neurosecretory cells create 2 hormones in the hypothalamus that are stored and released by the posterior pituitary:. The anterior pituitary gland is the true glandular part of the pituitary gland. The function of the anterior pituitary gland is controlled by the releasing and inhibiting hormones of the hypothalamus. The anterior pituitary produces 6 important hormones:. The pineal gland is a small pinecone-shaped mass of glandular tissue found just posterior to the thalamus of the brain. The pineal gland produces the hormone melatonin that helps to regulate the human sleep-wake cycle known as the circadian rhythm.
The activity of the pineal gland is inhibited by stimulation from the photoreceptors of the retina. This light sensitivity causes melatonin to be produced only in low light or darkness. Increased melatonin production causes humans to feel drowsy at nighttime when the pineal gland is active. The thyroid gland is a butterfly-shaped gland located at the base of the neck and wrapped around the lateral sides of the trachea. The thyroid gland produces 3 major hormones:. Calcitonin is released when calcium ion levels in the blood rise above a certain set point.
Calcitonin functions to reduce the concentration of calcium ions in the blood by aiding the absorption of calcium into the matrix of bones. Increased levels of T3 and T4 lead to increased cellular activity and energy usage in the body. The parathyroid glands are 4 small masses of glandular tissue found on the posterior side of the thyroid gland.
The parathyroid glands produce the hormone parathyroid hormone PTH , which is involved in calcium ion homeostasis. PTH is released from the parathyroid glands when calcium ion levels in the blood drop below a set point. PTH stimulates the osteoclasts to break down the calcium containing bone matrix to release free calcium ions into the bloodstream.
bahana-line.com: The Endocrine System (The Human Body-How It Works) ( ): Lynette Rushton, Denton A., M.D. Cooley: Books. The Human Body: How It Works Series Read about the key components and complex interac More Much like the nervous system, the endocrine syste.
PTH also triggers the kidneys to return calcium ions filtered out of the blood back to the bloodstream so that it is conserved. The adrenal glands are a pair of roughly triangular glands found immediately superior to the kidneys. The adrenal glands are each made of 2 distinct layers, each with their own unique functions: The adrenal cortex produces many cortical hormones in 3 classes: The adrenal medulla produces the hormones epinephrine and norepinephrine under stimulation by the sympathetic division of the autonomic nervous system. These hormones also work to increase heart rate, breathing rate, and blood pressure while decreasing the flow of blood to and function of organs that are not involved in responding to emergencies.
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