Reproduction

Created by Li Monnie

Age of the onset of puberty

Depends on the activity levels and body fat

• More activity→ inhibit GnRH secretion
• Leptin (protein) secreted by fat cells is required for puberty

secondary sex characteristics

Influence by

testestrone or estradiol-17β secretion

^{a. In girls: growth spurt, breast development,}

^{menarche (first menstrual flow)}

^{b. In boys: later growth spurt; body, muscle, penis,}

^{and testis growth}

^{c. In both sexes: body hair is stimulated by}

^{androgens from adrenal gland at puberty}

Male Accessory sex organs

Spermatogenesis

Spermatogenesis: Process of production or development of spermatozoa (stage 3→4)

Spermatogonia(2n)→ Spermatocytes(2n)/(1n)→ Spermatids(1n)→ Spermatozoa(1n)

Male reproductive system

Puberty

1. FSH and LH secretion remains high for first 6 months, then decline until puberty
2. Puberty begins with release of LH→  increase in (testestrone or estradiol-17β secretion)

→ Produce secondary sex characteristics

Why?

To have correct timing for puberty and secondary sexual characteristics development

Reproduction

Erectile tissues

Sex hormones very low in childhood

Fertility

Contraceptive methods

Hypothalamus

Endocrine regulation of reproduction

Sexual reproduction

Placental protein hormones

Placental steroid hormones

GnRH

• regulate FSH and LH
• pulsatory

Anterior pituitary

Hormones

Sex chromosomes

Implantation

Mammary gland structure

Lactation

Gonads

Gonadotropins

Hormones such as FSH and LH in both female and male, for:

1. Stimulation of spermatogenesis or oogenesis

2. Stimulation of gonadal hormone secretion

3. Maintenance of the structures of the gonads

Testosterone: negative feedback on FSH and LH

Esteradiol: inhibit LH

Gonadal hormones

Male: testosterone

Female: estrogen, progestrone

Inhibin

1. Secreted by Sertoli cells in testes
2. Secreted by granulosa cells of ovarian follicles
3. Specifically inhibits release of FSH (no effect

on LH)

Contraceptive methods

Disorders of embryonic sexual development

1.  Hermaphroditism: an ovary on one side and a testes on the other side; or have fused ovotestes.

Question: What determine a genetically male/female?

Ans: It involved complex factors such as DNA, internal gonads, external genitalia, etc, not only influenced by hormones.

1. Pseudohermaphroditism: accessory structures are not complete or are inapropreiate for the genetic sex. 

• Female Pseudohermaphroditism: congenital adrenal hyperplasia; exessive production of adrenal androgens (male sex hormone).
• Male Pseudohermaphroditism: due to malfunctionally testosterone receptors.
  1. Female external gentalia form, but internal mullerian ducts are degenerated
  2. Wollfian ducts also not stimulated 
  3. Inability to produce emzyme 5⍺-reductace, which required for musclinization of external genetalia 

Female reproductive system

Menopause

Pregnancy

Parturition

TDF on SRY gene

Menstrual cycle

Fertilization

Formation of testes

Seminiferous tubules form after production of TDF:

1. Germinal cells: Spermatogonia
2. Supporting cells: Sertoli cells
   1. make androgen-binding protein→ concentrate testosterone lv. 
3. Testosterone-producing: Leydig cells 

Reproductive organs

Hormone

Formation of ovaluries

Without TDF, gonads of XX embryos develops into ovaries

Sex determination

Mullerian-inhibiting factors

Testosterone

Testosterone from Leydig cells stimulate the developement of wolffian ducts.

LH triggers secretion of testosterone 

It contributes to muasculination, converted to DHT in brain cells by 5⍺-reductace or to estradiol by aromatase.

Question: Why testosterone need to be converted into DHT?

Ans: It has higher affinity for androgen receptors

1. help develop and maintain of male secondary sexual characteristics
2. differentiation of male external genitalia during fetal development

Development of ovum and follicle

Amniocentesis

External genitalia

They are identical for boy and girl in the first 6 months.

Primary and secondary follicle

Mullerian ducts

Becomes female tracts

Wolffian ducts

Become male tracts

Pituitary ovarian axis

Oogenesis

Graafin follicle

Mature follicle