ANAT2341 Lab 8 - Postnatal

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ANAT2341 Lab 8: Introduction | Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Online Assessment | Genital Quiz


This section gives a very brief overview of renal and genital postnatal changes that occur in neonatal, childhood and through to puberty. For sexual development at puberty, we will use resources available online from Endocrinology: An Integrated Approach (NCBI Bookshelf).

Renal - Nephron Development

Fetal nephron development 01.jpg

After nephron development has completed and concomitant with the development of the renal papilla in the newborn, the thin ascending limb of Henle’s loops is generated as an outgrowth from the S3 segment of the proximal tubule and from the distal tubule anlage of the nephron.[1] (birds and mammals)


Newborn uterus.jpg

Newborn uterus anatomy

  • Female tract abnormalities tend to be rarer and when they do occur are also more difficult to detect.
  • Male abnormalities are more likely and easily detected asociated with fusion of the urogenital folds, undescended testes or hernia.
  • This topic will be discussed on the next abnormalities will be discussed in detail on the next page.
Infant ovary.jpg * Ovary - Primordial follicle numbers are highest late fetal to around birth (estimated 2.5 - 7 million) and then decreasing by apopotic cell death.
  • At puberty there remain only about 400,000 and only about 10% of these will be released through reproductive life.

(Based on data from: Hassold, etal., Environ Mol Mutagen 1996. 28: 167-175)


Puberty growth.jpg Latin, pubertas = "adulthood"

In the teen years the endocrine changes that signal sexual development trigger changes in primary sex organs and the development of secondary sexual characteristics.

  • Hypothalamic expression of gonadotropin releasing hormone (GnRH) is a known puberty trigger.
  • Recent research suggests that an earlier signal could come from increased neuronal and hypothalamic expression of a peptide family (kisspeptins) and their receptor (G protein-coupled receptor GPR54) in the hypothalamus.
  • GnRH then signals the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to start sexual development.

Puberty can occur over a broad range of time and differently for each sex:

  • girls - age 7 to 13
  • boys - age 9 to 15
  • Early onset of puberty (precocious) occurs more frequently in girls than boys, in contrast late onset (delayed) occurs more frquently in boys than girls.
  • The physical characteristics that can be generally measured are: genital stage, pubic hair, axillary hair, menarche, breast, voice change and facial hair.
  • In 1976, Tanner and Whitehouse established a series of descriptive stages (Tanner Stages) for primary and secondary sexual characteristic development at puberty.

Study the Tanner stages comparing the male and female physiological changes.

Links: Puberty Development | Tanner stages

Female - Hypothalamus Pituitary Gonad (HPG) Axis

Menstrual cycle.png


  • menarche (the first menstruation or a period) usually occurs after the other secondary sex characteristics
  • cycles will continue until menopause (permanent cessation of reproductive fertility).
  • The diagram shows the hormonal regulation pathway from the brain to the ovary and subsequent impact on uterine changes during the menstral cycle.

GnRH = gonadotropin-releasing hormone (GnRH). This peptide hormone is a decapeptide (10 amino acids) with a short half life (<15 minutes).

LH = Luteinizing Hormone

FSH = Follicle Stimulating Hormone

A similar endocrine axis is also found for regulation of the male gonad.

Male - Testosterone

Male testosterone and AMH level graph.jpg


Testosterone and Anti-Müllerian Hormone (AMH) relative levels[2]

  • Sertoli cells - AMH production.
  • Leydig cells - Testosterone production
  • Spermatogonia - mitosis
  • Spermatozoa - maturation

Additional Information

Endocrinology: An Integrated Approach. Nussey S, Whitehead S. Oxford: BIOS Scientific Publishers; 2001.


  1. <pubmed>23338209</pubmed>
  2. <pubmed>16544032</pubmed>| Arq Bras Endocrinol Metabol.

ANAT2341 Lab 8: Introduction | Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Online Assessment | Genital Quiz

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Cite this page: Hill, M.A. (2024, June 14) Embryology ANAT2341 Lab 8 - Postnatal. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G