Structure And Function Of The Endocrine System – Is a message system in the body that consists of feedback loops of hormones that are secreted by the endocrine glands directly into the blood system that target and regulate distant organs. In vertebrates, the hypothalamus is the central nervous system for the entire docrine system.
In humans, the major docrine glands are the thyroid, parathyroid, pituitary, pineal, and adrenal glands, as well as the (male) testicles and (female) ovaries. The hypothalamus, pancreas, and thymus also act as endocrine glands, among other functions. (The hypothalamus and pituitary gland are organs of the neurodocrine system. One of the most important functions of the hypothalamus-it is located in the brain near the pituitary gland-is to connect the docrine system to the nervous system through the pituitary gland.) Other organs, such as the kidneys , also have a role in the docrine system by secreting other genes. The study of the docrine system and its disorders is known as science.
- 1 Structure And Function Of The Endocrine System
- 2 Hypothalamus And The Pituitary Gland
Structure And Function Of The Endocrine System
Glands that signal to each other in sequence are called an axis, such as the hypothalamic-pituitary-adrenal axis. In addition to the specialized teaching organs mentioned above, many other organs in other body systems have secondary teaching functions, which include the bones, kidneys, liver, heart and gonads. For example, the kidney secretes the endocrine hormone erythropoietin. Hormones can be complex amino acids, steroids, eicosanoids, leukotries, or prostaglandins.
Endocrine System 1: Overview Of The Endocrine System And Hormones
The docrine system is divided into both exocrine glands, which secrete hormones to the outside of the body, and a system known as paracrine that signals betwe cells over a short distance. Docrine glands do not have ducts, have blood vessels, and usually have intracellular vacuoles or granules that store hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands in the gastrointestinal tract, are less vascular and have ducts or humus. docrinology is a branch of internal medicine.
The human docrine system consists of many processes that operate through feedback loops. Most of the important response systems are mediated by the hypothalamus and pituitary.
Docrine glands are glands of the docrine system that secrete their products, hormones, directly into interstitial spaces where they enter the bloodstream instead of through ducts. The major glands of the docrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal gland. The hypothalamus and pituitary gland are neurodocrine organs.
The hypothalamus and anterior pituitary are two of the three endocrine glands that are important in cell signaling. Both are part of the HPA axis which is known to play a role in cell signaling in the nervous system.
Endocrine System 6: Pancreas, Stomach, Small Intestine And Liver
Hypothalamus: The hypothalamus is the key regulator of the autonomic nervous system. The docrine system has three types of outputs
Which includes the magnocellular system, the parvocellular system, and the medial system. Magnocellular is involved in the expression of oxytocin or vasopressin. Parvocellular is involved in controlling the release of hormones from the anterior pituitary.
Some examples of hormones secreted by the anterior pituitary gland include TSH, ACTH, GH, LH, and FSH.
There are many types of cells that make up the docrine system and these cells usually form tissues and organs that function inside and outside the docrine system.
Endocrine Vs Exocrine Glands
The fetus can be diagnosed in the fourth week of pregnancy. The adral cortex originates from the intermediate thickness of the mesoderm. At five to six weeks of pregnancy, the mesonephros differentiates into a tissue known as the genital ridge. The genital ridge supplies steroidogenic hormones to the gonads and adrenal cortex. Adral medulla is derived from ectodermal cells. The cells that will become the adral tissue move retroperitoneally to the upper part of the mesonephros. At seven weeks of pregnancy, the adrenal cells fuse with sympathetic cells that originate from the adrenal gland to form the adrenal medulla. At d of the eighth week, the adrenal glands become capsulated and form a special organ above the developing kidneys. At birth, the adrenal glands weigh about eight to nine grams (twice the size of adult adrenal glands) and make up 0.5% of the total body weight. At 25 weeks, the adult adral cortex area develops and is responsible for the first synthesis of steroids in the first weeks of life.
The thyroid gland develops from two different sets of embryonic cells. One part is from the thickness of the pharyngeal floor, which acts as a thyroxine (T) receptor.
) produce follicular cells. The other part is from the caudal secretory of the fourth pharyngobranchial pouch that gives rise to parafollicular calcitonin-secreting cells. These two features appear by 16 to 17 days of pregnancy. Around the 24th day of pregnancy, the cecum bubble, a thin flask-like part of the middle anlage develops. At about 24 to 32 days of pregnancy, the average anlage develops into a bilobed structure. By the 50th day of pregnancy, the central and peripheral nodes have merged together. At 12 weeks of pregnancy, the fetal thyroid can store iodine to produce TRH, TSH, and free thyroid hormone. At 20 weeks, the fetus can process the reaction to produce thyroid hormones. During fetal development, T
Lateral and vtral view of the embryo showing the third (smaller) and fourth (larger) parathyroid glands in the 6th week of embryogesis.
Hypothalamus And The Pituitary Gland
Once the embryo reaches four weeks of pregnancy, the parathyroid gland begins to develop. The human esophagus forms five rows of pharyngeal pouches. The third and fourth sacs are responsible for growth in the lower and upper parathyroid glands, respectively. The third pharyngeal pouch enumerates the developing thyroid gland and migrates to the lower lobes of the thyroid gland. The fourth pharyngeal nerve later articulates with the developing thyroid gland and migrates to the superior thyroid lobes. At 14 weeks of pregnancy, the parathyroid glands begin to grow from 0.1 mm in diameter to approximately 1 – 2 mm at birth. The developing parathyroid glands are physiologically active starting in the second trimester.
Studies in mice have shown that interfering with HOX15 ge can cause aplasia of the parathyroid gland, which indicates that ge plays an important role in the development of the parathyroid gland. ges, TBX1, CRKL, GATA3, GCM2, and SOX3 have also been shown to play important roles in parathyroid gland formation. Mutations in TBX1 and CRKL genes are associated with DiGeorge syndrome, while mutations in GATA3 also cause DiGeorge-like syndrome. Defects in GCM2 genes cause hypoparathyroidism. Studies on SOX3 gene mutations have shown that it plays a role in parathyroid development. These mutations also cause different types of hypopituitarism.
The human fetus begins to develop by the fourth week of pregnancy. After five weeks, pancreatic alpha and beta cells begin to appear. When it reaches eight weeks to t in development, the pancreas begins to produce insulin, glucagon, somatostatin, and pancreatic polypeptide. During the early stages of fetal development, the number of pancreatic alpha cells exceeds the number of pancreatic beta cells. Alpha cells reach their peak in the middle stage of pregnancy. From mid-stage to term, beta cells continue to increase in number until they reach an almost 1:1 ratio with alpha cells. The insulin concentration in the fetus is 3.6 pmol/g at seven weeks to t, which rises to 30 pmol/g at 16-25 weeks of pregnancy. Over time, the insulin concentration increases to 93 pmol/g. Docrine cells are dispersed throughout the body at 10 weeks. At 31 weeks of development, the islets of Langerhans are differentiated.
While the fetus has active beta cells by 14 to 24 weeks of pregnancy, the amount of insulin released into the bloodstream is relatively low. In a study of pregnant women with fetuses in the middle of pregnancy and near the stages of development, the fetuses did not have an increase in plasma insulin levels in response to injections of high glucose levels. Unlike insulin, fetal plasma glucagon levels are high and continue to increase during development. In the middle stage of pregnancy, the concentration of glucagon is 6 μg/g, compared to 2 μg/g in adults. Like insulin, fetal blood levels of glucagon do not change due to glucose infusion. However, one study showed that alanine infusion in pregnant women increased cord blood and maternal glucagon synthesis, indicating a fetal response to amino acid exposure.
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Thus, while fetal pancreatic alpha and beta islet cells are fully developed and capable of hormone synthesis during the rest of fetal growth, the islet cells are immature in their ability to produce glucagon and insulin. This is thought to be the result of better regulation of fetal blood glucose levels achieved by the transfer of glucose into the placenta through the placenta. On the other hand, the stability of the blood glucose levels of the fetus can be related to the failure of the pancreatic signal initiated by the incretin during feeding. In addition, offer pancreatic islets
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