The endocrine system is an integrated system of glands, each of which secretes different types of hormones that travel through the blood.
The endocrine system differs from the exocrine glands, which in turn secrete their chemicals through ducts.
The endocrine system is similar to the nervous system in that it transmits information, although they differ in the mechanism of action. The endocrine system is slow but prolonged, lasting from a few hours to weeks. But the nervous system is fast, but the impact is short.
Hormones regulate vital functions in the body: metabolism, growth and development, sleep, tissue functions, mood and others.
The medical science that deals with endocrine disorders is called endocrinology and is a branch of internal medicine
Structure
Major endocrine systems
The human endocrine system consists of several systems that operate via feedback loops. Several important feedback systems are mediated via the hypothalamus and pituitary gland.
TRH - TSH - T3 / T4
Hypothalamic-pituitary-gonadal axis.
The hypothalamic-pituitary-adrenal axis.
The renin-angiotensin system.
Energy balance theory (leptin vs. insulin).
glands
Crystal Clear app kdict.png Main article: Endocrine gland
Endocrine glands are glands in the endocrine system that secrete their products and hormones directly into the interstitial spaces and absorb them into the blood rather than the duct. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid glands, hypothalamus, and adrenal gland. The pituitary gland and the hypothalamus are neuroendocrine organs.
cells
There are many types of cells that make up the endocrine system and these cells usually consist of larger tissues and organs that function in and out of the endocrine system.
Hypothalamus
anterior pituitary gland
Pineal gland
Posterior pituitary
Thyroid
T3 and T4 follicular cells produce and secrete T3 and T4 in response to elevated levels of TRH (thyrotropin-releasing hormone), which is produced by the hypothalamus, and subsequent elevated levels of TSH (thyroid-stimulating hormone), which are produced by the anterior pituitary, which further regulates metabolic activity Nutritional (metabolism) and all cell rates, including cell growth and tissue differentiation.
Parathyroid glands
The parathyroid epithelial cells supply an abundance of blood from the inferior and superior thyroid arteries and parathyroid hormone (PTH). BTH acts on the bones, kidneys, and digestive system to increase calcium absorption and phosphate excretion. In addition, BTH stimulates the conversion of vitamin D to its most active form, citriol, or 1,25-dihydroxycholecalciferol, which also stimulates the absorption of calcium in the digestive tract.
adrenal glands
adrenal cortex
adrenal medulla
pancreas
alpha cells
beta cells
delta cells
Islands of Langerhans
ovaries
granulosa cells
testicles
interstitial cells
Endocrine glands and hormones secreted
Hypothalamus
(English: Hypothalamus)
hormonal secretion effect
Thyrotropin releasing hormone stimulates the secretion of TSH
Dopamine inhibits prolactin secretion
Growth hormone-releasing hormone stimulates the secretion of growth hormone
Somatostatin inhibits the secretion of growth hormone and thyroid-stimulating hormone
Gonadotropin-releasing hormone stimulates follicle-stimulating hormone and luteinizing hormone
Corticotropin-releasing hormone stimulates the secretion of ACTH
Oxytocin, uterine contractions and breastfeeding
Vasopressin reabsorbs water in the kidneys, thus increasing blood volume
Pineal gland
It resembles a small pine cone and is located inside the brain and produces the hormone melatonin, which acts as a clock to regulate the sleep-wake pattern of humans.
the pituitary gland
They are the most important endocrine glands in the human body at all, because they control most of the vital activities in the body, including the activities of other endocrine glands, which are the size of a pea and connect to the hypothalamus and produce hormones that affect a large number of body activities, starting from growth to reproduction.
Thyroid
Located under the pharynx, it is rich in blood vessels and produces hormones that regulate the rate of metabolic processes, control the deposition of calcium ions in the bones, and promote the normal development of the nervous system.
Parathyroid glands
Parathyroid glands are connected to the parathyroid glands from the back side, which number 4 and regulate the level of calcium ions in the body.
Skin
The organ that covers the human body and the bodies of many other animals. The main function of the skin in humans is to protect the body in several ways: the skin is almost completely resistant to wetness, and it also prevents the permeation of fluids that submerge the tissues of the body.
adipose tissue
stomach
The stomach is a muscular sac that mixes food with its digestive juices
duodenum
liver
pancreas
The pancreas is located under the stomach and digests food. Within the pancreas, hundreds of endocrine tissues are called islets of Langerhans. The cells that make up these islets produce hormones that lead to the regulation of the level of sugar in the blood
the college
It is found in the urinary system
Adrenal
There is one gland above each kidney, and this gland with a complex structure produces a number of hormones, some of which play an important role in adapting the body to emergency situations
ovary
The ovaries are the female reproductive organs in the lower part of the abdominal cavity, and the size of each ovary is equal to the size of an almond
placenta (when pregnant)
uterus (when pregnant)
Evolution and growth
adrenal glands
The adrenal glands can be identified on the fetal adrenal cortex within four weeks of conception. The adrenal cortex arises from the thickness of the mesoderm. During five to six weeks of pregnancy, the mesonivirus (or intermediate nephrosis) differentiates into a tissue known as the gonad strand. The gonadal cascade produces the steroidal cells of both the gonads and the adrenal cortex. The adrenal medulla is derived from skin cells. The cells that will become retroperitoneal adrenal tissue move to the top of the mesonivirus. Within seven weeks of gestation, the adrenal cells attach to sympathetic cells arising from the neural crest in order to form the adrenal medulla. At the end of the eighth week, the adrenal glands are encapsulated and form an organ above the developing kidney. The adrenal glands weigh eight to nine grams at birth (twice the weight of the adult adrenal glands) and make up 0.5% of the total body weight. At 25 weeks, the area of the adult adrenal cortex develops and becomes responsible for the primary synthesis of steroids during the early postpartum weeks.
The thyroid gland develops from two different sets of embryonic cells. Part of the pharyngeal floor thickening, which serves as a precursor to follicular-cell-producing thyroid hormone (T4). The other part of the caudal extensions of the fourth pharyngeal follicles leading to the calcitonin-secreting para-follicle cells. These two structures appear on the 16-17th day of pregnancy. The foramen develops on the 24th day of gestation and is a thin flask-like atresia of the mesocosm. At about 24 to 32 days of gestation, the mesosphere develops into a binary structure. During 50 days of gestation, the medial and lateral mantle fuses. At the 12th week of pregnancy, the fetal thyroid gland is able to store iodine in order to produce TRH, TSH and free thyroid hormone. At week 20, the fetus is able to implement feedback mechanisms in order to produce thyroid hormones. During fetal development, T4 is the major thyroid hormone produced while triiodothyronine (T3) and its inactive derivative, reverse T3, are not detected until the third trimester.
parathyroid glands
The parathyroid glands begin to develop once the fetus reaches four weeks of gestation. The human embryo forms five groups of lining pharyngeal follicles. The third and fourth follicles are responsible for development into the inferior parathyroid glands. The third pharyngeal follicle faces the developing thyroid gland and migrates down the poles of the thyroid lobes. The fourth pharyngeal follicle later encounters the developing thyroid gland and passes to the upper poles of the thyroid lobes. In the 14th week of pregnancy, the parathyroid glands begin to enlarge from 0.1 mm in diameter to approximately 1-2 mm at birth. The developing parathyroid glands are physiologically functional from the second trimester of fetal life.
Studies in mice have shown that interference with the HOX15 gene can cause parathyroid aplasia, suggesting that the gene plays an important role in the development of the parathyroid gland. The genes TBX1, CRKL, GATA3, GCM2, and SOX3 have also been shown to play a critical role in parathyroid formation. Mutations in the TBX1 and CRKL genes are associated with DiGeorge syndrome, while mutations in GATA3 have also led to DiGeorge syndrome. Abnormalities in the GCM2 gene led to hypothyroidism. Studies of mutations in the SOX3 gene have shown that it plays a role in the development of the parathyroid glands. These mutations also lead to varying degrees of hypopituitarism.
pancreas
The fetal pancreas begins to develop by the fourth week of pregnancy. After five weeks, the alpha and beta cells of the pancreas begin to appear. After eight to ten weeks of development, the pancreas begins to produce insulin, glucagon, somatostatin, and pancreatic polypeptide. During the early stages of fetal development, the pancreas has more alpha cells than beta cells. Alpha cells reach their peak in the middle stage of pregnancy. Beta cells continue to increase until they reach an approximate ratio of 1:1 with alpha cells from the middle stage to the end. The insulin concentration within the fetal pancreas is 3.6 pmol/g at seven to ten weeks, rising to 30 pmol/g at 16-25 weeks of gestation. In the short term, the insulin concentration increases to 93 mmol/g. The endocrine cells spread throughout the body within 10 weeks. The Islets of Langerhans vary in their 31 weeks of development.
While the fetal pancreas contains functional beta cells at 14 to 24 weeks of gestation, the amount of insulin released into the bloodstream is relatively low. In a study of pregnant women carrying fetuses in mid-gestation and near term development, the fetuses did not have an increase in plasma insulin levels in response to injections of high levels of glucose. Unlike insulin, fetal plasma glucagon levels are relatively high and continue to increase during development. In the middle of pregnancy, the glucagon concentration is 6 mcg/g, compared to 2 mcg/g in adult humans. Just like insulin, fetal plasma glucagon levels do not change in response to glucose infusion. However, a study of alanine infusions in pregnant women has been shown to increase umbilical cord blood and maternal glucagon concentrations, indicative of the fetus''s response to exposure to the amino acids.
