Reproductive System Chapter 27: Male Reproductive System

Male Reproductive System

• A gamete is a specialized sex cell carrying 23 chromosomes, with sperm being the male gamete and oocyte being the female gamete.
• Testes produce sperm and androgens to support reproduction, located inside the scrotum to maintain a temperature 2-4 degrees cooler than body temperature.
• The testes have two layers: tunica vaginalis (outer layer) and tunica albuginea (tough connective tissue).
• Seminiferous tubules are where sperm develops, and they are tightly coiled and separated into 300-400 lobules.
• Sertoli cells promote sperm production and can eliminate germ cells, creating the blood-testis barrier due to tight junctions.
• Spermatogonia are stem cells or germ cells of the testes, and spermatogenesis is the process of producing sperm in the seminiferous tubules, which begins at puberty.

Structure of Sperm

• Sperm is smaller than most cells, with a volume 85,000 times less than a female gamete, producing 100-300 million sperm per day.
• The head of the sperm contains a haploid nucleus and little cytoplasm, covered in lysosomal enzymes in the acrosome.
• The mid-piece of the sperm contains tightly packed mitochondria.
• The tail of the sperm is a flagellum for movement or motility.

Sperm Travel

• Sperm travels from the seminiferous tubules to the epididymis, taking 12 days to move through the epididymis.
• The epididymis is a 6-meter-long, tightly coiled tube where sperm continues to mature.
• Sperm is stored in the tail of the epididymis until ejaculation occurs.

Male Reproductive Organs

• Seminal vesicles contribute 60% of semen volume, providing fructose for ATP.
• The prostate gland is a walnut-sized muscle and gland tissue that secretes fluid to coagulate semen.
• Bulbourethral glands contribute a thick, salty fluid to lubricate the end of the urethra and vagina.

Penis and Testosterone

• The penis has three chambers surrounding the urethra that fill with blood during arousal and REM sleep.
• Nitric oxide is released to dilate blood vessels and rapidly increase blood volume to fill the chambers.
• Testosterone is secreted by the 7th week of development to differentiate male sexual organs, increasing again at puberty.

Female Reproductive System

• The primary function of the female reproductive system is to produce gametes and hormones, as well as support and deliver a developing fetus.
• Ovaries are the female gonads, and oocytes are produced in the ovaries.
• The vulva includes external reproductive structures such as the labia minora, clitoris, hymen, and vagina.

Ovarian Cycle

• The ovarian cycle is approximately 28 days and has two interrelated processes: oogenesis (production of female gamete) and folliculogenesis (growth and development of follicles).
• The ovarian cycle consists of the follicular phase, ovulation, and the luteal phase.

Oogenesis

• Oogonia are ovarian stem cells that divide by mitosis, formed during fetal development.
• Primary oocytes halt development until puberty and last until menopause.
• Ovulation is the release of a mature oocyte from the ovary, which divides unequally with only one cell large enough to become a mature ovum.

Folliculogenesis

• Follicles grow and develop in the ovary, with only one dominant follicle surviving to release an oocyte.
• The process is regulated by GnRH, LH, and FSH hormones.

Menstrual Cycle

• The menstrual cycle is the shedding, rebuilding, and preparation of the uterine lining for implantation, consisting of three phases: menses, proliferative, and secretory.
• The timing starts with the first day of menses (day 1 of period).

Breasts and Hormonal Birth Control

• Breasts are accessory organs that supply milk to infants during lactation.
• Hormonal birth control works by manipulating the negative feedback system, providing constant hormones to prevent FSH and LH production.