Endocrine System Development 2021 PDF

Endocrine system – presentation’s plan HISTOLOGY - ENDOCRINE SYSTEM DEVELOPMENT- Endocrine system vs nervous system Endocrine system’s function and its organization What are hormones??...

Endocrine system – presentation’s plan HISTOLOGY - ENDOCRINE SYSTEM DEVELOPMENT- Endocrine system vs nervous system Endocrine system’s function and its organization What are hormones?? Hypothalamo-hypophyseal system Hypophysis: adenohypophysis, neurohypophysis Thyroid Parathyroid Department of Histology and Embryo Adrenal glands Pomeranian Medical University in Sz Pancreas – Islets of Langerhans Pineal gland ENDOCRINE GLANDS  overriding endocrine gland  adenohypophysis  neurohypophysis (ectodermal) (neuroectoderm close to outpocketing of primitive 3rd ventricle) oral cavity (stomodeum) in a downward extension of the front of the oropharyngeal diencephalon membrane → → → the infudibulum →→→Rathke’s pouch Notci pituitary gland oral carity ↳ ectoderm twordsBrain - Neural ↳ Rathke's Stalk Rouch  3rd week: Rathke’s pouch appears as an evagination of the oral cavity and subsequentlly grows dorsally, toward the infundibulum.  5th week: Rathke’s pouch attaches to the neurohypophysis 3 grow I a tad  By the end of 2nd month it loses its conection with the oral cavity 6- Z conel and then it is in close contact with the infundibulum i us  During further development the cells of Rathke’s pouch increase rapidly in numer and form: ▪ anterior part of Rathke’s pouch increase rapidly and form the anterior lobe of the hypophysis (pars distalis) Anterior lobe -> ▪ a small extension of anterior lobe (adenohypophysis) grows along the stalk of - the infudibulum and surrounds it → pars tuberalis ▪ posterior part of the Rathke’s pouch develops into pars intermedia (rudimentary) The infundibulum give rise to: consist of neuroglial  the median eminence (part of hypothalamus; occasionally included as part of the posterior pituitary gland) cells (pituicytes) +  the neural stalk (=infundibular stem) nerve fibers from the pars nervosa (=posterior lobe of the hypothalamic area ↳  hypophysis) natons That produce Hormones  4th month of development: sweemAdehypophysi a Adenohypophysis: clearly visible chromophobes and chromophils, Acido connective tissue stroma, well developed capilaries - - Basophils chromophobes are inactive o chromophilsare active and Produce hormones such GH Prolactic as Neurohypophysis: finally formed → neuroglia cells differentiated during 4th month developed into pituicytes; the presence of nerve fibers (axons) that arised from hypothalamus as thataat the ⚫ Hormones production: 12th week: detectable concentrations of the GH and ACTH → 12th week: stimuli adrenal cortex development; 20-24 weeks: peak of release of GH -> > supravenal glands() MESODERM NEUROECTODERM (neural crest) > below cells neural plat--> same as  adrenal cortex  adrenal medulla veurohypophysis Hypphys's ectoderm - Adee Mesoder  5th week of development→ mesothelial cells between the root of the dorsal mesentery and the developing gonad begin to proliferate and penetrate the underlying mesenchyme ->guide to migrate to their upfrateversation (first wave of migration - thanks to multiadhesive glycoprotein) Mesothelial the cavitiesof cells are living organs - 5th week Mesotheliah - Actoral glands  active halls -> hormones -> EAcerohygrait ▪ These cells differentiate into the large acidophilic cells that form → the fetal cortex (primitive cortex) oth Mesotheilal -> a cidophillic feetex  5- >Mesotheila -> migrate-dilt-acd Modified postganglonic  7 week → while the fetal cortex is being th sympathetic neurons innervated by preganglonic formed, cells originating in the sympathetic sympathetic fibers system (neural crests cells) invade medial from north cells area of already formed fetal cortex, where they form cords and clusters → medulla relentes gardent ofneural crest notochord Cells from dorsal aorta liberate the signals (eg. BMPs) that influence on migration and specialization of neural crests cells  12th week → second wave migration of cells from the mesothelium → DHEA-> penetration the mesenchyme → estagen surround the original acidophylic 7th week:Medulla neural crest (fetal) cortex 12th week: the Frrin defifile contex ▪ the cells of second wave are smaller than those of the first These cells are steroid-producing cells, and in 2nd trimester begin wave, and are basophilic, later secreting dehydroepiandrosterone (DHEA) that is converted to they form definitive/permanent estrogen by the placenta → important for maintaining the placenta and pregnancy cortex of the gland  Adrenal glands in fetus/infant could be even 10-20 times bigger than in adult (proportionally to the body). In newborns, the adrenal glands represent 1/3 size of kidney up to 1st year of life: intensive fetal cortical atrophy (apart of zona reticularis)  after birth the fetal cortex (its inner layer) regresses rapidly (by apoptosis) execept for its outermost layer →→→ zona reticularis ↓ fetal Cortex decrease in size due to apotosis except -  The thyroid gland appears (4th week; 24th day) as an epithelial (endoderm) proliferation in the floor of pharynx at the base of the tongue at point later indicated by the foramen cecum ▪ Proliferation becouse of EGF and IGF  Subsequently, the thyroid descends in the neck  During this migration, the thyroid is connected to the tongue by a narrow canal, the thyroglossal duct (later disappears).  Thyroid gland descends in front of the hyoid bone and the laryngeal cartilages.  In the 7th week thyroid diverticulum reaches the final position in front of the trachea; at this time the small median isthmus and 2 lateral lobes are visible  10th week → follicular structure  The thyroid gland begins to function at the end of the 3rd month (prenatally), at this time the 1st follicles containing colloid becomes visible. 3 Ythweek lobet Visible 7th week: final position are - 3 noth: follic  The 4th (/5th) pharyngeal