Reproductive Systems Discussion Paper

Males and females both have primary reproductive organs called gonads, and secondary reproductive organs (ducts, glands, and external genitalia). Yet, particularly after puberty, male and female differences emerge. In this section, we will examine the anatomical elements of both the male and reproductive systems. Reproductive Systems Discussion Paper

Male Reproductive Organs

The male reproductive organs include primary sex organs (gonads) called testes, as well as secondary organs. Secondary organs include the scrotum, male duct system, penis, and glands. The three major male reproductive accessory glands are the prostate, seminal vesicles, and bulbourethral glands.

Encyclopedia Britannica. (2016). Male reproductive system [Illustration]. Britannica ImageQuest. https://go.openathens.net/redirector/rasmussen.edu?url=https%3A%2F%2Fquest-eb-com.eu1.proxy.openathens.net%2Fsearch%2Fmale-reproductive-system%2F1%2F309_365517%2FMale-reproductive-system%2Fmore

Testicles

The primary sex organs, testicles, come in a pair; they are made up of hundreds of seminiferous tubules which produce sperm. The seminiferous tubules transport sperm to the epididymis. The two types of cells within the seminiferous tubules are the germ cells, which mature into sperm, and the Sertoli cells, which support sperm development. Additional endocrine cells, Leydig cells, lie outside the seminiferous tubules. The Leydig cells produce testosterone.

Openstax. (2013). Testicle anatomy [Illustration]. Wikimedia Commons. https://en.wikipedia.org/wiki/Testicle#/media/File:Figure_28_01_03.JPG

The testicles’ surface is covered by a tunica albuginea, and then the scrotum. The scrotum’s location outside the abdominal cavity is critical for temperature regulation, as sperm require a temperature slightly lower than body temperature. The scrotum contains muscles and blood vessels to fine-tune temperature regulation.

· The dartos muscle can wrinkle the scrotum’s surface, therefore decreasing its surface area to promote heat retention.

· The cremaster muscle elevates the testes, and can serve to promote heat retention in cold conditions.

· The pampiniform venous plexus can, conversely, cool incoming blood due to its location surrounding the testicular artery.

Openstax. (2013). Musculature and inner workers of the scrotum [Illustration]. Wikimedia Commons. https://upload.wikimedia.org/wikipedia/commons/5/53/Figure_28_01_02.JPG

Each testicle’s posterior side contains a 20-foot coiled cord-like structure called the epididymis. The epididymis is where sperm cells mature. They take 20 days to pass through the epididymis. To exit the body, the sperm pass through additional ducts: ductus deferens (also called the vas deferens), the ejaculatory duct, and the urethra (which is shared with urine). The penis encases the ducts.

Sperm

Sperm make up only 10% of ejaculation, as male accessory glands create additional fluids to comprise seaman. Seminal vesicles secrete yellowish fructose-based alkaline liquids that comprise 60% of the semen volume. This fluid enhances sperm mobility within the female’s reproductive tract. The prostate secretion is a milky white substance that comprises 30% of the semen volume; it is nutrient-rich to support the sperm. The bulbourethral glands produce a small amount of additional clear fluid for lubrication.

Male anatomy [Illustration]. (2003). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Male_anatomy.png

Female Reproductive Anatomy

Like males, females have both internal and external reproductive anatomy. Internal female anatomical instructions include ovaries, ovarian tubes (also called fallopian tubes), the uterus, and the vagina. Externally, females have a clitoris and labia.

Typical sites for pelvic inflammatory disease [Illustration]. (2014). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Male_anatomy.png

Ovaries

The female primary sex organs (gonads) are called ovaries. They produce both eggs and sex hormones (progesterone and estrogen). The two ovaries are quite small, each being roughly the size of two almonds. They are not free-floating, as many ligaments support them. These ligaments include the ovarian ligament, suspensory ligament, broad ligament, and mesovarium.

Ovaries contain immature eggs (oocytes), each of which is surrounded by supporting granulosa cells and a follicle. Each month, one of these follicles is ovulated into a fallopian tube connected to the uterus.

The Uterus

The uterus is largely made of smooth muscle located between the bladder and rectum. Like kidneys, the uterus has three regions and three layers. The three regions are the fundus, body, and cervix. The three layers, from superficial to deep are the perimetrium, myometrium, and endometrium.

Encyclopedia Britannica. (2016). Female reproductive system [Illustration]. Britannica ImageQuest. https://go.openathens.net/redirector/rasmussen.edu?url=https%3A%2F%2Fquest-eb-com.eu1.proxy.openathens.net%2Fsearch%2Ffemale-reproductive-system%2F1%2F309_1156355%2FFemale-reproductive-system

The Vagina

The uterus leads to the vagina. The vagina is located between the rectum and bladder. It serves as a pathway for intercourse, menstruation, and the birthing process. In the next section, we will examine the menstrual process in further detail.

In this section, we will examine the physiological processes that occur within the male and female reproductive systems. These processes are male sperm production (spermatogenesis), and the female ovarian and uterine cycles.

Spermatogenesis

Males create 1,500 sperm per second, and the process continues throughout the adult life span. This process, known as spermatogenesis occurs in the seminiferous tubules within the testes. The Sertoli cells within the seminiferous tubules support sperm development. Once the sperm are fully mature, they enter the seminiferous tubules and pass their way to the epididymis, where they travel through the epididymis and mature into fully functional sperm. This process takes about 20 days, and then the sperm are stored in the tail of the epididymis until ejaculation.

Ruiz Villarreal, M. (2006). Complete diagram of a human spermatozoa [Ilustration]. Wikimedia Commons. https://en.wikipedia.org/wiki/Sperm#/media/File:Complete_diagram_of_a_human_spermatozoa_en.svg

Sperm Anatomy

The head of the sperm contains the nucleus which houses the DNA or chromosomes. Capping the head of the sperm is a structure called the acrosome that contains the enzymes to help penetrate the egg during fertilization. The midpiece of the sperm contains the mitochondria that supplies the sperm with ATP to be able to propel the tail to move through the female reproductive tract. Finally, the tail of the sperm is the flagellum that beats like a whip to propel and move the sperm forward and enables it to move through the reproductive tract of the female. We will examine the physiology of fertilization in our next module.

Ovarian and Uterine Cycles

Female reproductive physiology is more complex, as it involves coordinating two cycles: the ovarian cycle and the uterine cycle. The ovarian cycle regulates egg development. The uterine cycle regulates endometrium development within the uterus. The cycles occur at the same time in a 21-40-day range; the most typical range is 28 days.

Females are born with approximately 1 million oocytes, of which only 300-500 will develop to the point of ovulation. The ovarian cycle occurs in the ovaries, and consists of follicle and oocyte maturation, ovulation, and development of the corpus luteum. The ovarian cycle consists of two phases, the follicular phase and the luteal phase.

The Follicular Phase

The follicular phase lasts from day 1-14 of the 28-day cycle; during this phase, a dominant follicle matures and secretes large amounts of estrogen. Ovulation of this follicle’s mature oocyte will occur on day 14. Ovulation is the process by which the egg leaves an ovary to enter into the fallopian tubes. At this transition point, remaining granulosa cells form the corpus luteum as the cycle transitions to the luteal phase. This luteal phase lasts from day 14-28 and involves the activity of the corpus luteum. The corpus luteum secretes progesterone, which influences endometrial lining development in the uterus.

This ovarian cycle is coordinated with the uterine cycle, which pertains to the events that occur within the uterus. Most of the uterine changes involve thickening of the endometrium to prepare to receive a potentially fertilized egg, and shedding of this lining through menstruation as the alternative. The uterine cycle is divided into three phases: menstrual phase, proliferative phase, and secretory phase.

The Menstrual Phase

Days 1-5 of the 28-day cycle are termed the menstrual phase, as the endometrium is discharged through the vagina. At this point, the controlling hormones of estrogen and progesterone are at their lowest. After this period, estrogen begins to rise, and the endometrium rebuilds to prepare to receive a potentially fertilized egg. At day 14, progesterone from the corpus luteum begins to rise, which leads to thickening of the endometrium. If the egg is not fertilized, the corpus luteum breakdown (as part of the ovarian cycle) leads to endometrial decomposition as the uterine cycle re-enters into the menstrual phase.

Menstrual cycle [Illustration]. (2009). Wikimedia commons. https://commons.wikimedia.org/wiki/File:MenstrualCycle2_en.svg

The Endocrine System’s Hormonal Regulation

Both of these cycles are under the endocrine system’s hormonal regulation. The hypothalamus secretes gonadotropin releasing hormone, which signals the anterior pituitary’s release of follicle stimulating hormone (FSH) and luteinizing hormone (LH). These regulate the ovaries’ estrogen production, which sends a feedback loop to the hypothalamus to maintain homeostasis. Reproductive Systems Discussion Paper

Encyclopedia Brittanica. (2016). Female reproductive system [Illustration]. Britannica ImageQuest. https://go.openathens.net/redirector/rasmussen.edu?url=https%3A%2F%2Fquest-eb-com.eu1.proxy.openathens.net%2Fsearch%2Ffemale-reproductive-system%2F1%2F309_1156355%2FFemale-reproductive-system

Now that we have examined the physiology of the reproductive systems, check your understanding with the cases and activities that follow.