Editing Endocrine system (section)

==Structure==
===Major endocrine systems===
The human endocrine system consists of several systems that operate via [[feedback loop]]s. Several important feedback systems are mediated via the [[hypothalamus]] and pituitary.<ref>{{Cite book |title=Human Physiology: From Cells to Systems |url=https://archive.org/details/humanphysiologyf00sher |url-access=registration |author=Sherwood, L. |publisher=Wadsworth Pub Co |year=1997 |isbn=978-0-495-39184-5}}</ref>
* [[Hypothalamic–pituitary–thyroid axis|TRH – TSH – T3/T4]]
* [[Hypothalamic–pituitary–gonadal axis|GnRH – LH/FSH – sex hormones]]
* [[Hypothalamic–pituitary–adrenal axis|CRH – ACTH – cortisol]]
* [[Renin–angiotensin system|Renin – angiotensin – aldosterone]]
* [[Energy homeostasis|Leptin vs. ghrelin]]

===Glands===
{{Main|Endocrine gland}}
Endocrine glands are [[gland]]s of the endocrine system that secrete their products, [[hormone]]s, directly into interstitial spaces where they are absorbed into blood rather than through a duct. The major glands of the endocrine system include the [[pineal gland]], [[pituitary gland]], [[pancreas]], [[Ovary|ovaries]], [[Testicle|testes]], [[thyroid|thyroid gland]], [[parathyroid gland]], [[hypothalamus]] and [[adrenal gland]]s. The hypothalamus and pituitary gland are [[neuroendocrine]] [[Organ (anatomy)|organ]]s.

The hypothalamus and the anterior pituitary are two out of the three endocrine glands that are important in cell signaling. They are both part of the HPA axis which is known to play a role in cell signaling in the nervous system.

Hypothalamus: The hypothalamus is a key regulator of the autonomic nervous system. The endocrine system has three sets of endocrine outputs<ref>{{cite journal |author1=Clifford B. Saper |author2=Bradford B. Lowell |title=The Hypothalamus |journal=Current Biology |date=December 1, 2014 |volume=24 |issue=23 |pages=R1111-6 |doi=10.1016/j.cub.2014.10.023 |pmid=25465326 |s2cid=18782796 |url=https://www.cell.com/action/showPdf?pii=S0960-9822%2814%2901299-8|doi-access=free |bibcode=2014CBio...24R1111S }}</ref> which include the magnocellular system, the parvocellular system, and autonomic intervention. The magnocellular is involved in the expression of oxytocin or vasopressin. The [[Parvocellular neurosecretory cell|parvocellular]] is involved in controlling the secretion of hormones from the anterior pituitary.

[[Anterior pituitary|Anterior Pituitary]]: The main role of the anterior pituitary gland is to produce and secrete [[tropic hormone]]s.<ref>{{cite book |url=https://accessmedicine.mhmedical.com/content.aspx?bookid=507&sectionid=42540503 |title=Endocrine Physiology |publisher=McGraw Hill |year=2013 |editor-link=Patricia E. Molina |edition=4 |chapter=Chapter 3. Anterior Pituitary Gland}}</ref> Some examples of tropic hormones secreted by the anterior pituitary gland include TSH, ACTH, GH, LH, and FSH.

===Endocrine cells===
There are many types of cells that make up the endocrine system and these cells typically make up larger tissues and organs that function within and outside of the endocrine system.
* [[Hypothalamus]]
* [[Anterior pituitary|Anterior pituitary gland]]
* [[Pineal gland]]
* [[Posterior pituitary|Posterior pituitary gland]]
** The posterior pituitary gland is a section of the pituitary gland. This organ does not produce any hormone but stores and secretes hormones such as [[antidiuretic hormone]] (ADH) which is synthesized by supraoptic nucleus of hypothalamus and oxytocin which is synthesized by paraventricular nucleus of hypothalamus. ADH functions to help the body to retain water; this is important in maintaining a homeostatic balance between blood solutions and water. [[Oxytocin]] functions to induce uterine contractions, stimulate lactation, and allows for ejaculation.<ref>{{cite journal |last1=Quesada |first1=Ivan |date=2008 |title=Physiology of the pancreatic α-cell and glucagon secretion: role in glucose homeostasis and diabetes |url=https://joe.bioscientifica.com/view/journals/joe/199/1/5.xml |journal=Journal of Endocrinology |volume=199 |issue=1 |pages=5–19 |doi=10.1677/JOE-08-0290|pmid=18669612 |doi-access=free }}</ref><ref>{{cite book |title=How Does The Pancreas Work? |chapter=Physiology, Posterior Pituitary |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK526130/ |year=2021 |publisher=StatPearls |pmid=30252386 |last1=Patel |first1=H. |last2=Jessu |first2=R. |last3=Tiwari |first3=V. }}</ref>
* [[Thyroid|Thyroid gland]]
** [[Thyroid follicular cell|follicular cells]] of the thyroid gland produce and secrete [[Triiodothyronine|T<sub>3</sub>]] and [[Thyroxine|T<sub>4</sub>]] in response to elevated levels of [[Thyrotropin-releasing hormone|TRH]], produced by the [[hypothalamus]], and subsequent elevated levels of [[Thyroid-stimulating hormone|TSH]], produced by the [[Anterior pituitary|anterior pituitary gland]], which further regulates the [[Metabolism|metabolic activity]] and rate of all cells, including [[cell growth]] and [[Cellular differentiation|tissue differentiation]].
* [[Parathyroid gland]] The endocrine system can control all emotions and can control temperature.
** [[Epithelium|Epithelial]] cells of the parathyroid glands are richly supplied with blood from the [[Inferior thyroid artery|inferior]] and [[superior thyroid arteries]] and secrete [[parathyroid hormone]] (PTH). PTH acts on bone, the kidneys, and the [[Gastrointestinal tract|GI tract]] to increase [[calcium]] [[reabsorption]] and phosphate excretion. In addition, PTH stimulates the conversion of [[Vitamin D]] to its most active variant, [[1,25-dihydroxyvitamin D3|1,25-dihydroxyvitamin D<sub>3</sub>]], which further stimulates [[calcium]] absorption in the GI tract.<ref name="Marieb" />
* [[Thymus|Thymus Gland]]
* [[Adrenal gland]]s
** [[Adrenal cortex]]
** [[Adrenal medulla]]
* [[Pancreas]]
** Pancreas contain nearly 1 to 2 million [[islets of Langerhans]] (a tissue which consists cells that secrete hormones) and acini. Acini secretes digestive enzymes.<ref name=":2">{{Cite web|title=267 Endocrine System Facts|url=https://factslegend.org/267-endocrine-system-facts-learn-now-excel-exams/ |website=Facts Legend|date=September 19, 2018}}</ref>
*** [[Alpha cell]]s
**** The alpha cells of the pancreas secrete hormones to maintain [[Homeostasis|homeostatic]] blood sugar. Insulin is produced and excreted to lower blood sugar to normal levels. Glucagon, another hormone produced by alpha cells, is secreted in response to low blood sugar levels; glucagon stimulates [[glycogen]] stores in the liver to release sugar into the bloodstream to raise blood sugar to normal levels.<ref>{{cite journal |last1=Patel |first1=H. |last2=Jessu |first2=R. |last3=Tiwari |first3=V. |title=Physiology, Posterior Pituitary |url=https://www.ncbi.nlm.nih.gov/books/NBK526130/ |website=NCBI |year=2020 |publisher=StatPearls|pmid=30252386 }}</ref>
*** [[Beta cell]]s
**** 60% of the cells present in [[Pancreatic islets|islet of Langerhans]] are beta cells. Beta cells secrete [[insulin]]. Along with glucagon, insulin helps in maintaining glucose levels in our body. Insulin decreases blood glucose level ( a hypoglycemic hormone) whereas glucagon increases blood glucose level.<ref name=":2" />
*** [[Delta cell]]s
*** [[Pancreatic islets|F Cells]]
* [[Ovary|Ovaries]]
** [[Granulosa cell]]s
* [[Testicle|Testis]]
** [[Leydig cell]]s<ref>{{Cite web |title=Leydig cell {{!}} anatomy |url=https://www.britannica.com/science/Leydig-cell |access-date=2022-06-14 |website=Britannica |language=en}}</ref>