1. Reproduction (1)
Lecture Notes

2. Reproduction
Baby is in the uterus, up to 6 weeks of conception, the gonads are indifferent
meaning that they are the same in both males and females.
so if you open up a 6 week old fetus you'll find both a Mullerian and a Wolffian duct whether the fetus is a male or a female

3. Reproduction
So, what makes these ducts develop into a male or a female?
What we need is a testis determining factor.
It is known as the SRY gene which is located on the short arm of the Y chromosome.
It determines weather a testis will develop or not.
If SRY gene is absent the fetus will have ovaries which will produce the ovarian follicles, so it would be a female.
If SRY gene in present you'll have the development of the testis.

4. Reproduction In the testis you have 2 kinds of cells
Sertoli cells  inside the semineferous tubules  will secret Mullerian inhibiting factor  it will inhibit the Mullerian duct.
Leydig cells  in the interstitial tissue surrounding the semineferous  will produce testosterone  which will determine of the internal genitalia of the male  after that you need an enzyme ( 5 alpha reductase) which will convert Testosterone into Dihydrotestosterone the hormone you need for the development of external genitalia of male.

5. Reproduction
What if we have an XY genotype but the SRY gene was missing of the short arm of the y chromosome, what fetus will you have, male or female?
Female , with internal and external genitalia.

6. Reproduction
What if we have an XY and SRY gene is present but the enzyme ( 5 alpha reductase) which converts Testosterone into Dihydrotestosterone was not present?
Ambiguous genitalia, external femal genitalia with internal male genitalia

7. Reproduction
What if we have an XY and SRY gene is present and the enzyme ( 5 alpha reductase) which converts Testosterone into Dihydrotestosterone was present, BUT, the Mullerian inhibiting factor was not there?
It will develop both male and female internal genitalia.

8. Development of Internal Genitalia
We have 2 kinds of ducts
A Mullerian duct  will develop into the female internal genitalia
A Wolffian duct  will develop into the male internal genitalia

9. Development of Internal Genitalia
Before 6 weeks BOTH DUCTS exist in BOTH SEXES
Between 6 – 8 weeks:
In males testes develop
Sartoli cells: Mullerian inhibiting factor (MIF)  regression of Mullerian duct.
Leydig cells: testosterone  growth & development of Wolffian duct  male internal genitalia ( epididymis, vas deferens, seminal vesicle, ejaculatory duct).

10. Development of Internal Genitalia
In females:
The internal genitalia are: fallopian tubes, uterus and upper third of vagina

11. Development of External Genitalia
In males:
5 alph-dihydrotestosterone ( dependent on 5alpha-reductase) external genitalia (penis, prostate, scrotum and penile urethra)
In females
The external genitalia are: clitoris, labia majora and minora and lower 2 thirds of the vagina

12. Regulation of Sex Hormone Secretions
Sex steroid hormones which are secreted from the gonads, will feedback negatively on the pituitary to inhibit LH and FSH
It will also feed back negatively on the hypothalamus to inhibit gonadotropin releasing hormone (GnRH)
Inhibin is also secreted from the gonads will feedback negatively on the pituitary gland ONLY to inhibit FSH

13. Onset of Puberty Before Puberty
There is a very low sex steroids concentration in the circulation.
BUT:
Hypothalamus is very very very sensitive to any amount of sex steroids, so Gonadotropin releasing hormone (GnRH) is inhibited
Pituitary is very very very sensitive to any amount of sex steroids, so LH & FSH are inhibited

14. Onset of Puberty
Just before puberty sensitivity of hypothalamus and pituitary to sex steroids changes, they become less sensitive to them.
So the inhibition will not occur because there is a low amount of sex steroids in the circulation
GnRH will stimulate the pituitary
Pituitary will release LH & FSH which will act on the gonads
Gonads will produce sex steroids which will help in the development of secondary sex characteristics.

15. Male Reproductive System
Paired testes suspended in the scrotal sacs of the scrotum.
Testes develop during fetal development in the abdominal cavity but they need to be descended into scrotal sac during development. this is related to sterility.
For sperms to develop you need the temperature to be about 2 degrees below body temperature, so if you have the testes remaining in the abdominal cavity the temperature will be high  sperms will not form.
Boys under age of 6: if testis didn’t descend, the surgical intervention is important or these boys will become infertile

16. Organs of Male Reproductive System
Testes: function in the production of sperms and sex hormones, because they have Sartoli and Leydig
Epididymis: a site of maturation of sperms it is where they become mobile), and some storage of sperms.
Vas deferens: conduct and store sperm
Urethra: conducts both sperms and urine
Penis: organ of copulation (sexual intercourse)

17. Organs of Male Reproductive System
Testes consists of 2 parts
Seminiferous tubules:
Germinal cells: sperms
Sartoli cells: possess FSH receptors (they are inside the Seminiferous tubules)
Germinal cells + Sartoli cells which are required for spermatogenesis
Interstitial tissue: Leydig cells possess LH receptors (they are outside the Seminiferous tubules)
Leydig cells produce testosterone BUT Sartoli cells DO NOT produce testosterone

18. Spermatogenesis
From one spermatocyte we get 4 sperms with haploid number of chromosomes.
Spermatogenesis occurs in the seminiferous tubules , it needs LH & FSH , (Starting ~ 13yers old)
Takes an average of 70 days to complete
120 million sperms are produced/day
Spermatogenesis is from a spermatocye to a sperm
Spermiogenesis is from a spermatids to a sperm

19. Spermatogenesis Spermiogenesis is also a part of spermatogenesis.
Spermiogenesis needs Sartoli cells , they are nursing cells, their function is to help the spermatid to mature into a sperm
At the completion of spermatogenesis:
Spermatozoa (sperm) will be released into the lumen of seminiferous tubules (nonmotile)
Motility and maturation occur outside the testis in the epididymis

20. Spermatogenesis Mature sperm contains 3 parts:
Head: contains a nucleus covered by an acrosome which stores enzymes to penetrate the egg.
Middle piece: contains mitochondria wrapped around microtubules of the flagellum to provide energy for the movement
Tail: contains microtubules as components of flagellum, its movements propels sperm.

21. Spermatogenesis Mature sperm :
Gain motility in the epididymis and become more resistant to changes in PH & temperature (female vagina is more acidic and higher in temperature)
Most of sperms are stored in the vas deferens
During ejaculation vas deferens will obtain fluid secretions from 3 different glands
Seminal vesicle
Prostate gland
Pulbourethral gland

22. Control of Male Hormone Secretion
Hypothalamus secretes GnRH to stimulate the pituitary
The pituitary secrets LH & FSH to stimulates the testes
The testes now secrets testosterone, estrogen and inhibin
Testosterone will feedback negatively to inhibit LH and GnRH
Inhibin will feedback negatively on pituitary to inhibit FSH

23. Functions of Testosterone
It is the main sex hormone in males
Essential for development of male secondary sex characteristics :
Tallness, longer legs, broad shoulders
Enlargement of larynx and vocal cords, deepening of the voice
Greater muscle strength
Sex drive and aggressiveness
Oil and sweat glands secretion leading to acne and body odor
Development of hair on face, chest and back
Triggers baldness if appropriate genes are present
Essential for the maturation of sperms

24. What is The Effect of Taking Exogenous Testosterone?
It will feedback negatively on the pituitary and hypothalamus , therefore LH & FSH are not secreted , so they do not act on the testis, if they don’t act on the testis that will cause many problems such as infertility, atrophy of the testis

25.  Good Luck 