1. Human Reproduction and Development

2. Human Reproductive cells
Sperm is the smallest cell in a human’s body and is the only flagellated cell found in humans
Produced in the testes
Eggs are the largest cells found in a human’s body and can be seen with the naked eye
Produced in the ovaries

3. Male reproductive anatomy

4. Male reproductive anatomy
Testes
Testes are the organs that are responsible for producing sperm and release sex hormones including testosterone
Testosterone
The hormone that promotes the development of male reproductive tissues such as testes and prostate
Promotes secondary sexual characteristics such as increasing muscle and bone mass, growth of body hair, deepening of voice, and broadening of shoulders relative to the hips

5. Male reproductive anatomy
Sperm Production
Sperm is immobile at body temperature, so the testes are located outside the body to regulate the temperature of the sperm
The scrotum suspends the testes outside the body at about 2 degrees Celsius less than body temperature to produce viable sperm
Sperm is produced in seminiferous tubules that are coiled in the testes
Once the sperm have been produced, they move to the epididymis where they continue to mature

6. Male reproductive anatomy
Vas Deferens (“Carrying-Away Vessel”)
The tube that carries mature sperm from the epididymis to the urethra
Bulbourethral (Cowper’s) Gland
Secretes an alkaline mucus that neutralizes the acidity of the reproductive tract prior to ejaculation
Seminal Vesicles
Secrete a fluid that partly composes semen (approximately 60%)
Prostate Gland
Secretes a slightly alkaline fluid to help sperm move more easily and composes about 30% of the volume of semen

7. Spermatogenesis
Stage 1: Spermatogonium divides mitotically to produce two spermatogonium sub-types
one will restart the cycle, the other differentiates into a primary spermatocyte
Stage 2: The primary spermatocyte divides meiotically (meiosis I) to produce two secondary spermatocytes
Stage 3: Each secondary spermatocyte undergoes meiosis II and divides into two haploid spermatids
Stage 4: The spermatids undergo a maturation process where they become motile

8. Spermatogenesis

9. Sperm Anatomy Head Middle Tail
The head of the sperm cell contains the nucleus (containing 23 chromosomes) and the acrosome which contains digestive enzymes to break down the walls of the eggs cell
Middle
The middle contains the mitochondria that provides the cell with energy to propel itself
Tail
The flagellum that whips back and forth to propel the sperm cell

10. Sperm anatomy

11. Female Reproductive Anatomy

12. Female Reproductive Anatomy
Ovaries
Ovaries are the organs that are responsible for producing eggs and release sex hormones including estrogen
Estrogen
The hormone that is responsible for the development and regulation of the female reproductive system
Promotes secondary sexual characteristics such as enlargement of breasts, growth of body hair, and broadening of hip relative to the waist

13. Female Reproductive Anatomy
Egg Production
The ovaries are the reproductive organs responsible for producing eggs
Within each ovary are follicles – a group of cells, each with the potential to release an oocyte for fertilization
A females is born with all the follicles, each containing one oocyte (immature egg) she will ever produce (more than one million)
When the oocyte is mature, luteinizing hormone is secreted to begin ovulation, where the follicle ruptures and releases oocyte
The follicle remains functional but reorganizes as a Corpus luteum, releases progesterone to prepare the uterus for the implantation of the embryo (thickening of the uterine lining)

14. Female Reproductive Anatomy
The oocyte is released by the ruptured follicle, it enters the fallopian tube and gradually moves towards the uterus
Approximately 1-2% of ovulations release more than one oocyte and the fertilization of more than one oocyte would result in fraternal twins
Fertilization of the oocyte occurs in the fallopian tube
The oocyte enters the uterus, a think-walled muscular organ that provides mechanical protection and nutritional support to the developing embryo/fetus

15. Oogenesis
During the 6th to 8th week of embryonic development, oogonia differentiate from germ cells and divide mitotically during the 9th to 22nd week
More the 7 million oogonia are created but only around 1-2 million will remain when she is born
Before puberty, about 11 thousand oocytes dies every month
She will have just remaining when she hits puberty
Each month after puberty, about oocytes die each month

16. Oogenesis
Stage 1: Takes place when the female embryo is still in her mother’s uterus during development
Through mitosis, oogonia proliferate during embryonic development creating millions of primary oocytes
Stage 2: Primary oocytes begin meiosis I but are halted at Prophase I until puberty when menstruation begins and only a few do so every menstrual cycle
Divides asymmetrically into one secondary oocyte that receives most cytoplasm and the first polar body that eliminates a set of chromosomes

17. Oogenesis
Stage 3: The secondary oocyte begins meiosis II immediately after meiosis I has completed but is again halted at metaphase II until fertilization occurs and if it does, the oocyte completes meiosis II resulting in an ootid and another polar body
Stage 4: The polar bodies disintegrate, leaving only the ootid, which then undergoes a maturation phase into a mature ovum (egg cell)

18. Menstrual Cycle
In many cultures, in particular, Native American cultures, menstruation (or moon time) is a sacred time of inner purification by ridding a woman negative energy
Women are life-givers and are the bearers of future generations
Indigenous cultures say that women are more closely connected to the spirit world and Mother Earth because of their common ability to bear life and are more powerful and sacred

19. Menstrual Cycle