Lecture Notes under Development (notice removed when completed)
This lecture is an introduction to the events of Endocrine Development and the associated endocrine organs.
Note that the placenta is an additional endocrine organ not present in the adult and that fetal hormones are required for normal development.
Historic image of the pituitary
(More? Carnegie Stages)
(Links to slides now fixed)
Lectopia Audio Link to the audio recording of this lecture will be added here when available.
The following text is extracted and modified from lecture slides and should be used as a "trigger" to remind you of key concepts.
The following links are to UNSW Embryology additional resources that provide further background information on the Lecture topics. Note that not all information found on these additional links is considered examinable and the lecture slides and laboratory classes should be used as your initial guide for course theory content.
Links: Introduction | Abnormalities | Stage 13/14 | Stage 22 | Selected Stage 22 | Thyroid | Pituitary | Adrenal | Pancreas | Pineal | Thymus | Gonad | Placenta | Hypothalmus | Parathyroid | Adipose Tissue | Other Tissues | Molecular |
The search window below allows a search within the UNSW Embryology website.
The endocrine organs distribute regulatory signals to many tissues. Some fetal endocrine organs are required to function for normal development. In addition to the classically identified endocrine organs there is also the placenta and a range of other tissues which have now been shown to have an endocrine function.
These lecture pages are being updated for the current course, so it is worth coming back again later to see if any changes have occurred. Please let me know by email of broken links or content that is not clearly covered in this supporting online material.
Developmental Biology 6th ed. Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000.
Below are listed links that relate to this Lecture from the textbook "Developmental Biology" which is available free online. You can either click the provided links or do your own search using the search link.
Molecular Biology of the Cell 4th ed. Alberts, Bruce; Bray, Dennis; Lewis, Julian; Raff, Martin; Roberts, Keith; Watson, James D. New York and London: Garland Publishing; c2002.
Below are listed links that relate to this Lecture from the textbook "Molecular Biology of the Cell" which is available free online. You can either click the provided links or do your own search using the search link.
Blue Histology - Nervous Tissue |
Lecture 22 Animal Models and Stem Cells Wed 13:00 - 14:00 Australian School Business 119 (K-E12-119)
acaricide - Acarida are a subclass of the athropods, ticks and mites. Chemicals used for killing or preventing ticks and mites in crops or animals. Some of the early chemicals (eg endosulphan) may have also had a suggested endocrine disruptor function. (More? Endocrine Abnormalities)
adenohypophysis - (anterior pituitary, pars distalis) Part of the pituitary develops in the early embryo from a region (that exists only transiently) on the roof of the pharynx called Rathke's pouch. (More? Endocrine Development - Pituitary)
adipose - Fat, mesodermal in origin it is a type of connective tissue consisting mainly of adipocytes. The two forms of adipose are white and brown adipose tissue. Brown adipose is found in newborns (2 - 5 % of the body weight) and can be used to dissipate stored energy as heat (thermogenesis), while adults have mainly white adipose. Adipose tissue also has an endocrine function secreting the hormones leptin, adiponectin, and resistin. (More? Musculoskeletal Development - Adipose | Endocrine Development - Adipose)
adrenal gland - (suprarenal gland) Endocrine organ that anatomically sits on top of the kidneys (renal). (More? Endocrine Notes - Adrenal Gland)
adrenal virilism - Abnormality that leads to the development of male secondary sexual characteristics in women with excessive adrenal gland activity. (More? Endocrine Notes)
androgens - The male sex hormones, eg testosterone. (More? Genital System - Male)
Anti-Mullerian Hormone - (AMH, Mullerian Inhibiting Substance, MIS) A secreted factor (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. Inhibits paramesonephric (Mullerian) duct development in males. (More? Male | OMIM - AMH)
brown adipose - (brown fat) Neonatal specialized form of adipose tissue used in mammals to generate body temperature (thermogenic organ) by non-shivering thermogenesis. Adult fat (white adipose) cannot be used in this fashion. This form of adipose tissue is also seen in animals that hibernate. (More? Musculoskeletal Development - Adipose)
buccal - (Latin, bucca = cheek) A term used to relate to the mouth (oral cavity). (More? GIT Notes)
corpus luteum - (Latin, corpus = body, luteum = yellow) The remains of ovarian follicle after ovulation that acts as an endocrine organ (produce progesterone and oestrogens) supporting pregnancy and preventing menstruation (loss of the endometrial lining). Formed by proliferation of both follicular granulosa cells (granulosa lutein cells) and thecal cells (theca lutein cells) after ovulation. granulosa lutein cells and theca lutein cells and produce progesterone and oestrogens. de Graaf first observed it in the ovary of a cow as a yellow structure. (More? Week 1 - Oogenesis)
cortex - (Latin, corticalis = at the outside) outer layer, used in association with medulla (innner layer or core) a general description that can be applied to describing an organ with a layered structure. Also used to describe the outer cellular (grey matter) layer of the central nervous system.
corticosteroid - A steroidal hormone produced by the adrenal cortex. (More? Endocrine Notes)
corticotropin-releasing hormone - (CRH) A hypothalamic neuropeptide hormone, which is also produced by embryonic trophoblast and maternal decidua cells, with receptors in several reproductive organs. Thought to have a role in endometrial decidualization, blastocyst implantation and early maternal tolerance.
cretinism - The term describing a neurological abnormality due to insufficient thyroid hormone during neural development. The main cause of this disorder is an insufficiency or lack of iodine in the diet. (More? Endocrine Development - Thyroid | Abnormal Development - Iodine Deficiency)
DES - Diethylstilbestrol or diethylstilbetrol, a drug prescribed to women from 1938-1971 to prevent miscarriage in high-risk pregnancies. Acts as a potent estrogen (mimics natural hormone) and therefore a potential endocrine disruptor. Female fetus, increased risk abnormal reproductive tract and cancer. Male fetus, abnormal genitalia. Banned by USA FDA in 1979 as a teratogen, previously used as livestock growth promoter. (More? Abnormal Development)
diabetes insipidus - The disorder is related to the hormone antidiuretic hormone (ADH, also called vasopressin) its synthesis, secretion, receptors and signaling pathway. In diabetes insipidus there is an excretion of large amounts (up to 30 litres/day) of a watery urine and an unremitting thirst. (More? Kidney Abnormalities - Diabetes Insipidus)
Diabetes Type 2 - The disease due to noninsulin-dependent diabetes, where body does not respond correctly to insulin a life-long disease marked by high levels of sugar in the blood. (More? Endocrine- Pancreas | Maternal Diabetes | Medline - Diabetes Type 2)
dihydrotestosterone - The hormonally active form of testosterone (male sex hormone) produced by enzyme (5-alpha reductase) conversion. In the male embryo, this can occur in the genital skin which then supports external genital development. In the adult, this conversion occurs in a number of different tissues. A known treatment for prostate cancer include 5-alpha reductase inhibitors. (More? Urogenital Notes | Endocrine Notes )
diverticulum - (Latin, diverticulum = by-road) blind tubular process, also used to describe a sac or pouch in organ or seen in the colon. Occurs often in development when a new structure is forming from a epithelia or tract branch or in the initial/early stages of an epitheilal-mesenchymal interaction. The plural term is diverticula. Can also be found in normal and abnormal adult anatomical structures. (More? Developmental Mechanism - Epithelial Mesenchymal Interaction | GIT Abnormalities - Meckel's Diverticulum)
dynorphin - Protein whos full biological function unknown, 2 possibilities. In development, neuroendocrine regulation of the developing hypothalamo-pituitary-adrenal (HPA) axis. Secondly, a potential endogenous opioid peptide which has a high affinity for the kappa-opioid receptor.
endocrine disruptors - Term used to describe environmental chemicals that interfere with hormone function. Three main forms of interference: Mimic (effects of natural hormone), Block (binding of hormone to receptor or synthesis), Interfere (with hormone transport or elimination). (More? Endocrine Abnormalities)
endocrine gland - (Greek, endon = within) A gland (organ, tissue) that is specialized for secretion of a hormone into the bloodstream for general circulation. (More? Endocrine Notes)
Endosulfan - The commercial name for a chemical (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro- 6,9-methano-2,4,3-benzodioxathiepin-3-oxide) broad-spectrum insecticide and acaricide to control agricultural insect and mite pests in crops. Technical-grade endosulfan is composed of two stereochemical isomers, alpha-endosulfan (70%) and beta-endosulfan (30%). An Indian study has suggested that it acts as an endocrine disruptor, exposure in male children may delay sexual maturity and interfere with sex hormone synthesis. (More? Endocrine Notes | PubMed Environ Health Perspect. 2003 Dec;111(16):1958-62)
estrogens - Sex hormone found in both male and female. In the female, this hormone is produced by the ovaries and is responsible for development of secondary feminine sex characteristics. Together with progesterone these hormones also regulate changes that occur each menstral cycle. In the male, Leydig cells produce estrogen into the rete testis fluid at variable levels in different species. During male embryonic development exposure to high levels of estrogen can lead to genital abnormalities. (More? Human Menstrual Cycle)
fetal period - In humans, the development week 9 to 36 is the fetal stage (second and third trimester) and during this time organs formed in the embryonic period continue to develop and the fetus grows in size and weight. The first 8 weeks of development is considered the embryonic period and is divided into 23 Carnegie stages based upon developmental milestones. Note when searching an alternate spelling "foetal". (More? Fetal | Embryo Stages)
Finasteride - A chemical used to prevent male pattern baldness and enlargement of prostate glands. An anti-androgen (blocks synthesis of dihydrotestosterone) and therefore a potential endocrine disruptor, exposed pregnant women can impact on male fetus genetial development. (More? Endocrine Abnormalities)
follicle stimulating hormone - (FSH, gonadotropin) Glycoprotein hormone secreted by anterior pituitary and acts on gametogenesis and other systems in both males and females. In females, FSH acts on the ovary to stimulate follicle development. Negative feedback by inhibin from the developing follicle decreases FSH secretion. In males, acts on the testis Sertoli cells to increase androgen-binding protein (ABP) that binds androgens and has a role in spermatogenesis. FSH-deficientcy in females results in infertile (block in folliculogenesis prior to antral follicle formation) and in males does not affect fertility (have small testes but are fertile). FSH protein has a molecular weight 30 kDa and a 3-4 hour half-life in circulation. Gonadotrophins have been used clinically in humans for the treatment of infertility. Other glycoproetin hormones include luteinizing hormone (LH), thyroid stimulating hormone (TSH), and chorionic gonadotropin. (More? Week 1 - Oogenesis | Human Menstrual Cycle | Endocrine Development - Pituitary | Kumar TR, Wang Y, Lu N, Matzuk MM. Follicle stimulating hormone is required for ovarian follicle maturation but not male fertility. Nat Genet. 1997 Feb;15(2):201-4.)
genital ridge - (= gonadal ridge) The thickened epithelial/mesenchymal region adjacent and medial too the mesonephros. Primordial sex cells migrate into this region to form the indifferent gonad. These undifferentiated gonads have a cortex and a medulla. Female XX chromosome complex, cortex differentiates into an ovary, and medulla regresses. Male XY complex, medulla differentiates into a testis and cortex regresses. (More? Urogenital Notes)
ghrelin - (Greek, leptos = thin) a polypeptide hormone produced in the gastrointestinal tract (stomach) that stimulates release of growth hormone from the anterior pituitary. Hormone which probably has a role in regulating appetite and energy balance. (More? Endocrine Other Endocrine Notes | Meier U, Gressner AM. Endocrine regulation of energy metabolism: review of pathobiochemical and clinical chemical aspects of leptin, ghrelin, adiponectin, and resistin. Clin Chem. 2004 Sep;50(9):1511-25.
GHRH - Arconym for Growth Hormone Releasing Hormone, secreted by the Hypothalamus it is a protein that activates Growth Hormone synthesis and release from the pituitary. (More? Endocrine Notes - Hypothalamus)
goitre - (goiter) enlargement of thyroid gland due to a dietry deficiency of iodine, or thyroid hormone level abnormalities. Iodine is required to synthesise thyroid hormone which in turn is required for normal neurological development. (More? Abnormal Development - Iodine Deficiency | Endocrine Development - Thyroid)
gonadotrophin releasing hormone - (Greek, gonos = seed) (GnRH) Hormone released from hypothalamus that stimulates pituitary gonadotropin synthesis and secretion (luteinizing hormone, LH and follicle stimulating hormone, FSH). The cyclic release of GnRH has been shown to differentially affect gonadotropin release (rapid frequency, more than 1 pulse / hour LH; slower frequencies FSH secretion). (More? Week 1 Notes | Marshall JC, Eagleson CA, McCartney CR. Hypothalamic dysfunction. Mol Cell Endocrinol. 2001 Oct 25;183(1-2):29-32. Review.)
growth hormone - (GH) A peptide hormone, made in the anterior pituitary, that stimulates tissue and skeletal growth. (More? Endocrine Notes - Pituitary)
growth hormone releasing hormone - (GHRH) secreted by the hypothalamus it is a protein that activates Growth Hormone synthesis and release from the pituitary. (More? Endocrine Notes - Hypothalamus)
hormone - A substance, made and released by cells in a specific organ or structure, that moves throughout the organism and exerts specific effects on specific cells in other organs or structures. (More? Endocrine Notes)
human chorionic corticotropin - (human chorionic adrenocorticotropin, hCACTH) Placental hormone thought to have corticotropin (ACTH)-like activity, increasing maternal cortisol levels. (More? Placenta Notes)
human chorionic gonadotrophin - (hCG) Placental hormone initially secreted by syncitiotrophoblasts supports corpus luteum which in turn supports endometrial lining and therefore maintaining pregnancy. Hormone also stimulates the onset of fetal gonadal steroidogenesis, high levels are teratogenic to fetal gonadal tissues. (More? Placenta Notes | Week 2 Notes)
human chorionic somatomammotropin - (hCS, human chorionic somatommotropin, human placental lactogen, HPL) Placental peptide hormone, similar to pituitary growth hormone, secreted by placental syncytiotrophoblasts. Hormone level increases in maternal blood through pregnancy, decreases maternal insulin sensitivity (raising maternal blood glucose levels and decreasing maternal glucose utilization) aiding fetal nutrition. Has some weak growth hormone activity. (More? Placenta Notes | Integumentary Development - Mammary Glands)
human chorionic thyrotropin - (hCT) Peptide placental hormone, similar to anterior pituitary released thyroid stimulating hormone (TSH), which along with human chorionic gonadotrophin (hCG) is thought to act on maternal thyroid. There is little recent research published on this hormone, its level and activities. (More? Placenta Notes | Integumentary Development - Mammary Glands)
hypopharyngeal eminence - (hypobranchial eminence) An early embryonic structure in the developing head. A narrow midline mesodermal (mesenchymal) exension lying within the floor curve of the developing pharynx. Fusion of 3rd pharyngeal arches and precursor of root of tongue. Early developing thyroid cells also migrate into this structure as cords of cells. (More? Head Notes | Endocrine Development - Thyroid)
insulin - A protein hormone, produced by specialized cells of the pancreas, that regulates glucose uptake; a signal for the absorptive state; promotes the synthesis of glycogen and inhibits its breakdown. (More? Endocrine Development - Pancreas)
interstitial cell stimulating hormone - (ICSH, gonadotropin, lutropin, Interstitial Cell Stimulating Hormone, ICSH) Glycoprotein hormone releasd from anterior pituitary hormone that acts on the gonad and has a role in male and female reproduction. In male, stimulates testis interstital cell (Leydig cell) production of testosterone. In female, increase in concentration during the menstrual cycle triggers ovulation (release of the oocyte). (More? Endocrine Development - Gonads | Genital System - Male)
Iodine - (Greek, ioeides = violet) An element named for the color of its vapour. It is an essential element required for the synthesis of thyroid hormone, which in turn is required for normal neural development. (More? Abnormal Development - Iodine Deficiency)
islets of Langerhans - A small cell clusters spread throughout the exocrine pancreas with an endocrine (hormonal) function. (More? Endocrine Development - Pancreas)
larynx - Site of the the vocal folds in the neck. Embryologically develops from the foregut with the lining derived from endoderm and the cartilage from pharyngeal arch 4 and 6. Beginning as a simple foregut groove, the laryngotracheal groove which folds to form the laryngotracheal bud, then the larynx and trachea. (More? Gastrointestinal Tract NotesRespiratory Notes | Head Notes)
leptin - (Greek, leptos = thin) a polypeptide hormone (16 kDa) produced in adipose and many other tissues. Hormone receptor (OB-R, leptin receptors) found in many different tissues. Hormone levels associated with fertility and reproductive maturity in many species. Other hormonal roles include: satiety, adiposity, and metabolism, body mass control, angiogenesis, immunity, wound healing, bone remodelling cardiovascular function, and specific metabolic pathways. (More? Endocrine Adipose Endocrine Notes | Henson MC, Castracane VD. Leptin in pregnancy: an update. Biol Reprod. 2006 Feb;74(2):218-29.)
Leydig cells - (interstitial cells) Testis (male gonad) cell which secrete testosterone, beginning in the fetus. These cells are named after Franz von Leydig (1821 - 1908) a German scientist who histologically described these cells. (More? Genital Notes | Urogenital Notes)
Leydig cell hypoplasia - (LCH) or male pseudohermaphroditism is an autosomal recessive disorder in individuals with a 46,XY karyotype with a predominantly female phenotype (More? Hermaphroditism | Reproductive System - Abnormalities)
lingual - (Latin, lingua = tongue) Term used to describe structures and features related to the tongue: lingual papilla, lingual plate, lingual plexus, lingual thyroid nodule. (More? Tongue Notes | Head Notes)
luteinizing hormone - (LH, gonadotropin, lutropin, Interstitial Cell Stimulating Hormone, ICSH) Glycoprotein hormone releasd from anterior pituitary hormone that acts on the gonad and has a role in male and female reproduction. In female, increase in concentration during the menstrual cycle triggers ovulation (release of the oocyte). In male, stimulates testis interstital cell (Leydig cell) production of testosterone. Gonadotrophins have been used clinically in humans for the treatment of female infertility. (More? Human Menstrual Cycle | Genital Notes)
luteinizing hormone/chorionic gonadotropin receptor - (LHCGR) a G protein-coupled receptor expressed in male testis (Leydig cells) and female ovary (granulosa-lutein and theca cells) (More? Genital Notes)
median eminence - (Latin, medialis = middle) A midline pouch or recess in the floor of the third ventricle and an extension of the hypothalamus together with the neural stalk forms the infundibular stem, which in turn together with the posterior lobe forms the pituitary neurohypophysis. (More? Endocrine - Hypothalamus | Endocrine - Pituitary )
menopause - (Greek, mene = moon, men = month, pause = end or cessation) decrease in ovarian production of estrogen and progesterone leading to cessation of menstrual cycles, decrease in fertility, and end of female reproductive life. Usually occurs in the mid-40's, the term was first used by the French physician, de Gardanne in 1812. (More? Human Menstrual Cycle | Medline Plus - Menopause)
Mullerian Inhibiting Substance - (MIS, Anti-Mullerian Hormone, AMH, Mullerian inhibiting hormone, MIH). A sertoli cell secreted glycoprotein (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. The main role is to inhibit paramesonephric (Mullerian) duct development in males. Postnatally, after puberty it is also expressed in females by ovarian granulosa cells and has a role in follicle development. (More? Male | OMIM - AMH)
neural crest - cell region at edge of neural plate, then atop the neural folds, that remains outside and initially dorsal to the neural tube when it forms. These paired dorsal lateral streaks of cells migrate throughout the embryo and can differentiate into many different cell types (= pluripotential). Those that remain on the dorsal neural tube form the sensory spinal ganglia (DRG). Neural crest cells also migrate into the somites. (More? Neural Crest Notes)
osteoclast - Cells that remove bone (bone resorption) by enzymatically eroding the bone matrix. These cells are blood cell (monocyte-macrophage) in origin and fuse to form a multinucleated osteoclast. These cells allow continuous bone remodelling and are also involved in calcium and phosphate metabolism. The erosion cavity that the cells lie iwithin and form is called Howship's lacuna. Osteoclasts express a number of proteolytic Matrix MetalloProteinases (MMPs) including MMP-9, MMP-10, MMP-12 and MMP-14. (More? Musculoskeletal Development - Bone |Cardiovascular System - Blood)
oxytocin - (Greek, "quick birth") an 8 amino acid peptide hormone released from the maternal posterior pituitary, involved in initiation and maintenance of birth labor by acting on the myometrium. (More? Normal Development - Birth | Birth Overview )
pancreas - The gastrointestinal tract associated organ with both exocrine (pH change and digestive enzyme secretion) and endocrine (hormone secretion) functions. In humans, the pancreas develops at the foregut/midgut junction (the septum transversum) and initially form connected to the gastrointestinal tract as two pancreatic buds (dorsal and ventral endoderm) which later fuse to form a single organ. The pancreas exocrine function (alkylate acidic stomach contents and amylase protein digestion) begins mainly fter birth. The endocrine function (alpha cell - glucagon, delta cell - somatostatin, beta cell - insulin) can be measured from 10 to 15 weeks onward. (More? Gastrointestinal Tract - Pancreas | Endocrine Development - Pancreas)
parathyroid hormone-related protein - (PTHrP) A protein hormone produced by many fetal tissues and with a number of different functions including endochondral bone development, tooth development, and mammary gland epithelial-mesenchymal developmental interaction. Also suggested to have an autocrine role in lung development. (More? Parathyroid Notes | Respiratory Notes)
parenchyma - (Greek, enkeim = "to pour in") Term used to describe the cells forming the functional cells of an organ or tissue. These cells carry out the function of the organ at a cellular level. Within the organ, the other population of cells, stroma, are structural cells, connective tissue, the non-cellular extracellular matrix.
PCB - polychlorinated biphenyls, a class of chemicals linked to developmental defects. (More? Defects - Chemical Notes)
peritoneal cavity - The anatomical body cavity in which the lower body organs lie: intestines, liver, bladder, uterus, ovary. The peritoneal cavity forms initially from two separate regions of the early intraembryonic coelom (formed in the lateral plate mesoderm), which with embryo folding, fuse to form a single cavity. Note the single intraembryonic coelom forms all three major body cavities: pericardial, pleural, peritoneal. (More? Coelomic Cavity Notes | Gastrointestinal Tract Notes)
peritubular cells - (peritubular myoid cells) The stromal cells (mesenchymal) located in the male gonad (testis) seminiferous tubule lying outside the basal membrane in the lamina propria surrounding seminiferous tubulus that regulate Sertoli cell function and contractility of seminiferous tubules. Also used to describe cells found in the kidney glomerulus. (More? Week 1 - Spermatogenesis)
pharyngeal arch pouch - An out-pocketing of the endoderm lined pharynx occurring between each developing pharyngeal arch. Each of the pharyngeal arch pouches contributes different components of the head and neck, either cavities or endocrine tissues. Pharyngeal Arch 1 pouch elongates to form tubotympanic recess tympanic cavity, mastoid antrum and auditory tube (Eustachian tube). Pharyngeal Arch 2 pouch forms the tonsillar sinus and is later mostly oblierated by palatine tonsil. Pharyngeal Arch 3 pouch forms the inferior parathyroid and thymus. Pharyngeal Arch 4 pouch forms the superior parathyroid, parafollicular cells of Thyroid. (More? Middle Ear Notes | Thymus Notes | Parathyroid Notes | Thyroid Notes | Endocrine Notes | Head Notes | Face Notes)
pineal gland - endocrine gland named as shape resembles a pine cone. Formed from a dorsal outpocket of diencephalon. The hormone melatonin (high in dark, low in day) involved with the diurnal cycle, inhibits pituitary-gonad axis. (More? Endocrine Notes | Pineal Gland)
pharynx - uppermost end of gastrointestinal and respiratory tract, in the embryo beginning at the buccopharyngeal membrane and forms a major arched cavity within the phrayngeal arches. (More? Head Notes | GIT Notes | Carnegie stage 13 pharynx)
progesterone - A steroidal hormone of the progestogens class, which has many roles in the female. Functions include regulation of the menstrual cycle, uterine changes, maintaining pregnancy and effects on systems throughout the body. Biological sources include: adrenal glands, gonads (corpus luteum), brain, and placenta. Male progesterone has a suggested role in neural development. Progesterone is also used clinically as a part of hormone replacement therapy (HRT) in women. The human progesterone receptor has two isoforms (PRA and PRB). (More? Human Menstrual Cycle)
prolactin - (PRL) anterior pituitary hormone which stimulates breast development and milk production in pregnancy. Also has a role in regulating follicle stimulating hormone (FSH) effect on the ovary. Protein hormone is similar in structure to both growth hormone (anterior pituitary) and chorionic somatomammotropin (placenta). Anterior pituitary release of prolactin is in turn regulated by the hypothalamus prolactin-releasing hormone (PRLH, prolactin-releasing peptide). Recently been shown to to mimic in pregnancy effects of increased maternal myelination processes (oligodendrocyte precursor proliferation). (More? Endocrine Development - Pituitary | Normal Development - Milk | OMIM - PRL)
puberty - (Latin, pubertas = adulthood) process involving maturation of the reproductive system. A complex process, initiated by an unknown mechanism, but involving the brain driving the hormonal axis. (More? Endocrine Notes - Gonad | Puberty Notes)
Rathke's pouch - An ectodermal fold in roof of pharynx forming anterior pituitary (adenohypophysis) and pars intermedia. Named after German embryologist and anatomist Martin Heinrich Rathke (1793 — 1860). (More? Pituitary Notes | Endocrine Notes | Martin Heinrich Rathke)
second trimester - Clinical term used to describe and divide human pregnancy period (9 months) into three equal parts of approximately three calendar months. The first trimester corresponds approximately to embryonic development (week 1 to 8) of organogenesis and early fetal. The second and third trimester correspond to the fetal period of growth in size (second trimester) and weight (third trimester), as well as continued differentiation of existing organs and tissues. (More? Embryo Stages | Human Fetal Period | Development Week by Week)
sella turcica - (Latin sella = saddle, turcica = Turkish) refers to the shape of the sphenoid bone in which the pituitary gland resides (pituitary fossa). (More? Endocrine Notes - Pituitary)
Sertoli cells - The supporting cells in the testes (male gonad) that induce primordial germ cells to commit to sperm development. Support is nutritional and mechanical, as well as forming a blood-testis barrier. In development these cells secrete anti-Müllerian hormone, which causes the Müllerian (paramesonephric) duct to regress, and help to induce other somatic cells to differentiate into Leydig cells. The cells are named after Enrico Sertoli (1842 - 1910), and italian physiologist and histologist. (More? Urogenital Notes | Enrico Sertoli | UWA Blue Histology - Male Reproductive System)
sonic hedgehog - (SHH) secreted growth factor that binds patched (ptc) receptor on cell membrane. SHH function is different for different tissues in the embryo. In the nervous system, SHH is secreted by the notochord, ventralizes the neural tube, inducing the floor plate and motor neurons. In the limb, SHH is secreted by the zone of polarizing activity (ZPA) organizing limb axis formation. SHH has still others roles in organ development in lung, pancreas, etc. SHH name derives from homology to the original fruitfly (drosophila) "hedgehog" mutation, where these flies have hairs in regions (ventral) which are normally hair-free, and therefore have a disrupted body pattern. Nomenclature note lower case shh for other species, upper case SHH in humans. (More? Musculoskeletal Notes | Neural Notes | Molecular Notes)
stroma - (Greek, stroma = "a cover, table-cloth, bedding") Histological term used to describe supportive cells within an organ, tissue or structure. The term is often paired with parenchyma, which describes the functional cells of an organ, tissue or structure. All organs can therefore be functionally divided into these 2 components, stromal/parenchymal.
stromal cells - (Greek, stroma = "a cover, table-cloth, bedding") Descriptive term in the ovary, for cells surrounding the developing follicle that form a connective tissue sheath (theca folliculi). This layer then differentiates into 2 layers (theca interna, theca externa). This region is vascularized and involved in hormone secretion. (More? Week 1 Notes)
surfactant - A detergent secreted by Type 2 alveolar cells between alveolar epithelium. Functions to lower surface tension, allowing lungs to remain inflated. Note: In humans, these cells and their secretion develop towards the very end of the third trimester, just before birth. Hence the respiratory difficulties associated with premature births (Newborn Respiratory Distress Syndrome, Hyaline membrane disease). (More? Respiratory Notes | Respiratory Abnormalities | Newborn Respiratory Distress Syndrome)
testes (Latin testis = "witness") The two male gonads (singular testis) where male germ cells (spermatozoa) are generated and also the source of testosterone (male hormone). Embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are preserved in male gonad development and lost in females. (More? Genital System - Male)
third trimester - Clinical term used to describe and divide human pregnancy period (9 months) into three equal parts of approximately three calendar months. The third trimester corresponds to the fetal period of growth in weight, as well as continued differentiation of existing organs and tissues. The respiratory system matures late in teh third trimester. The first trimester corresponds approximately to embryonic development (week 1 to 8) of organogenesis and early fetal period, the second trimester is the fetal period of growth in size. (More? Embryo Stages | Human Fetal Period | Development Week by Week)
thyroid - (Greek, thyreos = sheild , eidos = form) endocrine gland located in the neck, the origin of the name reflects the organs anatomical structure. In the fetus, the thyroid gland has a role in neurological development. (More? Endocrine Notes | Thyroid Gland | Abnormal Development - Iodine Deficiency)
trimester - Clinical term used to describe and divide human pregnancy period (9 months) into three equal parts of approximately three calendar months. The first trimester corresponds approximately to embryonic development (week 1 to 8) of organogenesis and early fetal. The second and third trimester correspond to the fetal period of growth in size (second trimester) and weight (third trimester), as well as continued differentiation of existing organs and tissues. (More? Embryo Stages | Human Fetal Period | Development Week by Week)
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