1. Human Anatomy and Physiology
Chapter 27 – Reproductive System

2. The Reproductive System
Functions:
Produce sex cells (eggs and sperm)
Permit the joining of the sex cells
Provide an environment for the development of a fertilized egg (only in the female)

3. Male Reproductive System
The male gonads (organs that produce sex cells) are the testes.
The testes are held within the scrotum
Optimum sperm production occurs at about 3° C cooler than internal body temperature
The scrotum helps to regulate the temperature of the testes
The dartos and cremaster muscles
Figures 27.1 and 27.2

4. Male Reproductive System
The penis contains erectile tissue – Figure 27.4

5. Male Reproductive System
Inside the testes there is a series of coiled tubes called seminiferous tubules (ST)
these are the site of sperm production
they have a total length of nearly half a mile!
Outside the ST are the interstitial or Leydig cells that produce testosterone
Figure 27.3

6. Male Reproductive System (cont.)
Spermatogenesis
about 400 million sperm are produced each day!
Inside the ST there are two cell types:
Spermatogenic cells – these will become sperm
Sertioli cells (sustentacular cells) – help nourish the germ cells
They also form the blood-testis barrier
Figure 27.8

7. Male Reproductive System (cont.)
Germ Cells
Spermatogonia – around the periphery of the ST
Divide by mitosis to start the process of sperm production
One cell  spermatocyte, One cell  spermatogonia
The spermatocytes then proceed through meiosis to produce functional sperm cells
Figure 27.8

8. Male Reproductive System (cont.)
Mature sperm have three distinct parts:
head - nucleus and acrosome
midpiece - contains mitochondria
tail - flagellum for motility
Figure 27.9

9. Male Reproductive System (cont.)
Sperm produced in the testes mature in the epididymis
They are also stored here for as long as several months
the epididymis is connected to the urethra by a long tube called the vas deferens (ductus deferens)
vasectomy - severing of the vas deferens
Figure 27.1 and Figure from other text

10. Male Reproductive System (cont.)
Before leaving the body, sperm are mixed with a fluid
seminal fluid + sperm = semen

11. Male Reproductive System (cont.)
Seminal fluid is produced by three glands:
seminal vesicles – (60%) mucus, fructose, fibrinogen, prostaglandins
prostate gland – (30%) enzymes, clotting factors
bulbourethral gland – (5%) mucus
The remaining 5% of semen is composed of sperm
Normal sperm count is million sperm per ml of semen
Figure 27.1

12. Male Reproductive System (cont.)
Hormonal Regulation in Males
Hypothalamus – Gonadotropin-releasing hormone (GnRH)
Stimulates the release of the gonadotropins from the anterior pituitary gland:
Luteinizing Hormone (LH) – increases testosterone production in the Leydig cells
Follicle-Stimulating Hormone (FSH) – binds to Sertioli cells and stimulates sperm cell production
Figure 27.10

13. Male Reproductive System (cont.)
Puberty – onset of sexual maturity
Human chorionic gonadotropin is produced by the placenta during fetal development
This stimulates the release of testosterone for initial male sex organ development
After birth, very little testosterone is produced until puberty

14. Male Reproductive System (cont.)
At puberty the hypothalamus increases GnRH secretion
This in turn increases LH and FSH secretion resulting in testosterone production
Effects of testosterone
Development and enlargement of male reproductive system
Stimulates hair production on face, legs, chest, pubic region (and back, occasionally)

15. Male Reproductive System (cont.)
Increases rate of sebaceous gland secretion
Can result in acne
Increases metabolism, RBC production, and protein synthesis
Causes rapid bone growth (but also stimulates the closure of the epiphyseal growth plate)

16. Female Reproductive System
The female gonads are the ovaries
the ovaries alternate in producing one egg per month
The ovaries also produce estrogen and progesterone (the female sex hormones)
Anatomy - Figures and 27.14

17. Female Reproductive System (cont.)
Oogenesis
There are many follicles within the ovaries
each follicle contains an immature egg
there are about 2 million follicles at birth
300, ,000 at puberty
only ~400 are ever released as mature eggs
the egg is released from the ovaries during ovulation
The corpus luteum is a hormone-secreting gland in the ovary
Figures and 27.19

18. Female Reproductive System (cont.)
Puberty
Marked by menarche (the first menstrual period)
Reproductive organs and breasts enlarge and develop
Puberty results from estrogen and progesterone production

19. Female Reproductive System (cont.)
The Menstrual Cycle
Typically the cycle lasts 28 days
Includes both the ovarian and uterine cycles

20. Female Reproductive System (cont.)
The Ovarian Cycle:
Days 1-14 are the Follicular Phase
Day 14 – Ovulation
Days are the Luteal Phase

21. Female Reproductive System (cont.)
The Follicular Phase
Early in the cycle GnRH secretion increases
Effect?
FSH and LH stimulate the development of a follicle and
The production of estrogen by the ovary

22. Female Reproductive System (cont.)
A surge of LH results in ovulation
It also leads to the development of the corpus luteum
The corpus luteum secretes estrogen and progesterone
If fertilization does not occur, the cells of the corpus luteum degenerate
Estrogen and progesterone secretion then rapidly declines and the cycle starts over
Figures and 27.22

23. Female Reproductive System (cont.)
The Uterine Cycle:
Days 1-5: Menstrual Phase
the endometrium is sloughed off
Days 6-14: Proliferative Phase
endometrium thickens and prepares for pregnancy
Caused by estrogen and progesterone
Days 15-28: Secretory Phase
endometrium continues to thicken and secretions increase
Figure 27.22, Figure from other text, and CD

24. Female Reproductive System (cont.)
Menopause - period when uterine cycles and ovulation cease
usually occurs between the ages of 45 and 55

25. Fertilization and Pregnancy
Fertilization occurs in the fallopian tubes
If the egg is fertilized, human chorionic gonadotropin is released
This keeps the corpus luteum from degenerating and stops the uterine cycle
The embryo can become embedded in the uterine wall
Figures from other text and 28.4

26. Fertilization and Pregnancy
Timing of intercourse:
The egg is only viable for hours after ovulation
Sperm cells can survive for hours
Therefore intercourse must occur between days in the menstrual cycle
Even given the right timing, fertilization is not certain
Figure 28.2 and other figure

27. Fertilization and Pregnancy
Twins:
Fraternal – 2 eggs released and fertilized
Identical Twins – 1 egg separates to form 2 babies
Figures from other text

28. Methods of Birth Control
Table and Figures from other text

29. Methods of Birth Control
Discussion

30. Infertility 15% of all couples in the US cannot have children
these couples would be considered sterile
Another 10% have fewer children than they wish
these couples are termed infertile
The most frequent causes of infertility in females are:
blocked oviducts
endometriosis - presence of uterine tissue outside the uterus
The most frequent cause of infertility in males is:
low sperm count

31. Alternative Methods of Reproduction
Artificial Insemination - sperm are placed in the vagina by a physician
sperm from donor
concentrated sperm from husband with low sperm count
In Vitro Fertilization - sperm and egg are mixed in a test tube
fertilized egg is placed in the female’s uterus

32. Alternative Methods of Reproduction (cont.)
Gamete Intrafallopian Transfer - eggs and sperm are mixed in a test tube
they are immediately injected into the fallopian tubes
Surrogate Mothers - individuals donate eggs and/or sperm
the surrogate mother carries the fetus