|Embryology - 22 Feb 2017 Expand to Translate|
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- 1 Introduction
- 2 Some Recent Findings
- 3 Reading
- 4 Second Trimester
- 5 Third Trimester
- 6 Growth
- 7 Fetal Neural
- 8 Fetal Endocrine
- 9 Fetal Respiratory
- 10 Fetal Genital
- 11 Fetal Renal
- 12 Fetal Gastrointestinal
- 13 Fetal Integumentary
- 14 Fetal Surgical Procedures
- 15 References
- 16 Glossary Links
| This page shows some key events of human development during the fetal period (weeks 9 to 37) following fertilization. The long Fetal period (4x the embryonic period) is a time of extensive growth in size and mass as well as ongoing differentiation of organ systems established in the embryonic period. Clinically this period is generally described as the Second Trimester and Third Trimester. Many of the critical measurements of growth are now carried out by ultrasound and this period ends at birth.
|Changing fetal proportions, not size growth.||Use the links below to get more detailed information about this period of development.|
|Fetal Links: Introduction | Week 10 | Week 12 | Second Trimester | Third Trimester | Fetal Neural | Fetal Blood Sampling | Birth-Weight | Fetal Origins Hypothesis | Fetal Growth Restriction | BGD Practical | Medicine Lecture | Science Lecture | Preterm Birth | Birth | Category:Human Fetus|
Some Recent Findings
Then look in detail at the head development in a 12 week fetus showing both forms of ossification in the skull.
Third trimester Crown-Rump Length
Fetal Head Growth
- HPA axis established by week 20
- Pituitary functional throughout fetal development
- required for metabolic activity, also in the newborn
- important for neural development
- newborn has total calcium levels (approx 20 grams) accumulated mainly in the 3rd trimester (weeks 28–40)
- fetal parathyroid hormone (PTH) potentially available from 10–12 weeks and PTH does not cross the placenta
- fetus relatively hypercalcemic, active transplacental transport of Ca2+ to fetus
- maternal serum - calcium ions (Ca2+), inorganic phosphate (Pi) and PTH concentrations are within the non-pregnant normal range throughout pregnancy.
- maternal bone turnover increases in the 3rd trimester.
- maternal diabetes can affect fetal pancreas development (increase in fetal islet beta cells).
- testosterone - required during fetal development for external genital development and internal genital tract in male.
- estrogens - secreted inactive precursor converted to active form by placenta.
- Links: Endocrine System Development | Endocrinology - Control of steroid production in the fetal gonads | Neuroscience - The Effect of Sex Hormones on Neural Circuitry
- week 4 - 5 embryonic
- week 5 - 17 pseudoglandular
- week 16 - 25 canalicular
- week 24 - 40 terminal sac
- late fetal - 8 years alveolar
- ovary and testis development
- external genital development
- testis descent
|Tests descent beginning||Tests descent end|
- Links: Genital System Development
- week 32-34 nephron development completed
- term birth nephron number per kidney about 1 million (300,000 to 2 million)
Nephron development has four identifiable developmental stages:
- Vesicle (V) stage (13-19 weeks, second trimester)
- S-shaped body (S) stage ( 20-24 weeks, second trimester)
- Capillary loop (C) stage (25-29 weeks, third trimester)
- Maturation (M) stage (infants aged 1-6 months, neonatal and postnatal)
Fetal developmental features include: the growth and rotation of intestines initially herniated outside the ventral body wall; changes in mesenteries; development of the blood supply and tract wall.
The initial functions of the tract with amionic fluid swallowing and the accumulation of both secretions and swallowed components within the large intestine as meconium.
Fetal Surgical Procedures
There are a range of fatal abnormalities that are potentially amenable to surgical intervention, see recent review link Maternal-Fetal Surgical Procedures.
Some examples include:
- Cardiac Malformations
- Congenital Diaphragmatic Hernia
- Myelomeningocele/Spina Bifida
- Obstructive Uropathy
- Sacrococcygeal Teratoma
- Thoracic Lesions
- Twin-Twin Transfusion Syndrome
- Osman Sulak, Gülnur Ozgüner, Mehmet Ali Malas Size and location of the kidneys during the fetal period. Surg Radiol Anat: 2011, 33(5);381-8 PubMed 21110022
- Hitoshi Ishimoto, Robert B Jaffe Development and function of the human fetal adrenal cortex: a key component in the feto-placental unit. Endocr. Rev.: 2011, 32(3);317-55 PubMed 21051591
- Heiko Locher, John C M J de Groot, Liesbeth van Iperen, Margriet A Huisman, Johan H M Frijns, Susana M Chuva de Sousa Lopes Development of the stria vascularis and potassium regulation in the human fetal cochlea: Insights into hereditary sensorineural hearing loss. Dev Neurobiol: 2015; PubMed 25663387
- Takashi Satoh, Eiichi Sakurai, Hiroshi Tada, Tomoyuki Masuda Ontogeny of reticular framework of white pulp and marginal zone in human spleen: immunohistochemical studies of fetal spleens from the 17th to 40th week of gestation. Cell Tissue Res.: 2009, 336(2);287-97 PubMed 19255788
- A Afif, R Bouvier, A Buenerd, J Trouillas, P Mertens Development of the human fetal insular cortex: study of the gyration from 13 to 28 gestational weeks. Brain Struct Funct: 2007, 212(3-4);335-46 PubMed 17962979
- H J Kadhim, J F Gadisseux, P Evrard Topographical and cytological evolution of the glial phase during prenatal development of the human brain: histochemical and electron microscopic study. J. Neuropathol. Exp. Neurol.: 1988, 47(2);166-88 PubMed 3339373
- C Garel, E Chantrel, H Brisse, M Elmaleh, D Luton, J F Oury, G Sebag, M Hassan Fetal cerebral cortex: normal gestational landmarks identified using prenatal MR imaging. AJNR Am J Neuroradiol: 2001, 22(1);184-9 PubMed 11158907
- L B Paquette, H A Jackson, C J Tavaré, D A Miller, A Panigrahy In utero eye development documented by fetal MR imaging. AJNR Am J Neuroradiol: 2009, 30(9);1787-91 PubMed 19541779
- Maternal-Fetal Surgical Procedures. Walsh WF, Chescheir NC, Gillam-Krakauer M, et al. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011 Apr. (Comparative Effectiveness Technical Briefs, No. 5.) Report | Comparative Effectiveness Research, Health Care
Darren Farley, Donald J Dudley Fetal assessment during pregnancy. Pediatr. Clin. North Am.: 2009, 56(3);489-504, Table of Contents PubMed 19501688
Rosalie M Grivell, Lufee Wong, Vineesh Bhatia Regimens of fetal surveillance for impaired fetal growth. Cochrane Database Syst Rev: 2009, (1);CD007113 PubMed 19160321
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Cite this page: Hill, M.A. 2017 Embryology Fetal Development. Retrieved February 22, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/Fetal_Development
- © Dr Mark Hill 2017, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G