Exercise 10: Reproductive System

Figure 10.1 A human secondary oocyte is fertilized in vitro using intracytoplasmic sperm injection.

Exercise 10 Learning Goals 

After completing this lab, you should be able to: 

• Identify the internal and external structures associated with the male and female reproduction system
• Recognize and label the regions of the male urethra
• Detail the function of each reproductive system structure
• Recount the process of spermatogenesis
• Describe the phases of the menstrual cycle and the processes of oogenesis and fertilization
• Explain lactation and name the structures of the mammary glands

Pre-Lab Activities for Exercise 10

Pre-Lab Activity 10.1: Describe Structures of the Male Reproductive System

The male reproductive system includes the testes, epididymis, penis and a series of ducts and glands.

Figure 10.2 Major structures of the male reproductive system include the testes, epididymis, duct system, accessory glands and supporting structures including the penis.

Use your required textbook to complete the table below.

Table 10:1: Describe the structures of the male reproductive system.

Figure 10.3 External and deep view of the scrotum and testes. The first part of the figure shows the external appearance of the scrotum. The second part shows the muscle layers, and the third part shows the deep tissues, including the testes.

Figure 10. 4: Internal anatomy of the testis. The figure depicts the view of the testes with the cremaster muscle pulled away to reveal internal anatomy.

1. What is the order of ducts and glands that sperm pass through before exiting via the urethra?
2. Which muscles are responsible for adjusting the position of the testes relative to the body?

Pre-Lab Activity 10.2: Describe Structures of the Female Reproductive System

The female reproductive system is composed of the ovaries, uterine tubes, uterus, vagina, and vulva.

Figure 10.5 The major organs of the female reproductive system are located inside the pelvic cavity and include the ovaries, uterine tubes, uterus, vagina, and pudendum.

Use your required textbook to complete the table below.

Table 10:2: Describe the structures of the female reproductive system

Figure 10.6 The external female genitalia are referred to collectively as the vulva or pudendum. The figure depicts the external genitalia labeled, and the internal anterolateral view of the genitalia labeled as well.

Pre-Lab Activity 10.3 The Uterine Wall and the Menstrual Cycle

The uterine wall consists of 3 layers:

1. Perimetrium- outer layer, continuous with the visceral peritoneum
2. Myometrium- middle layer, composed of 3 layers of smooth muscle
3. Endometrium-inner layer, made up of the stratum basalis and functionalis

• stratum basalis – covers the myometrium and produces a new functional layer each month
• stratum functionalis - glandular and vascular layers that supports the embryo and otherwise sheds monthly resulting in menstruation.

The female reproductive cycle is a combination of two cycles: the uterine and the ovarian cycles. The ovarian cycle includes events that occur in the ovaries during and after ovulation. The uterine (menstrual) cycle occurs concurrently and involves changes in the endometrium and the uterus. The reproductive cycle is hormonally regulated by follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary and by estrogen and progesterone from the ovaries. The fluctuation in these hormones produces 3 phases:

1. Menstrual phase (menses): day 1-5, “sloughing off” of lining, accompanied with bleeding
2. Proliferative phase (pre-ovulatory): day 6-13, due to estrogen: the endometrium is repaired, glands and vessels proliferate, and the endometrium thickens. Ovulation occurs at the end of this phase on day 14 and is stimulated by increased levels of LH. During ovulation, a secondary oocyte is released into the pelvic cavity.
3. Secretory phase (post-ovulatory): day 15-28, is due to increases in progesterone and estrogen. During this phase there is an increase in vascular supply, the size of glands, and secretion of nutrients for sustaining an embryo if present. If there is not an embryo present hormone levels decline- the corpus luteum deteriorates and the endometrium deteriorates resulting in menses.

Figure 10.7 Hormone Levels in Ovarian and Uterine Cycles The correlation of the hormone levels and their effects on the female reproductive system is shown in this timeline of the ovarian and menstrual cycles.

Pre-Lab Activity 10.4: Label Structures of the Uterus, Uterine Wall, and Ovaries

Figure 10.8 Female reproductive structures including histology of the uterus

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Pre-Lab Activity 10.5: Mammary Glands and Lactation

The mammary glands are modified sweat glands that produce milk in lactation.

Each breast consists of:

• Lobes (15-20) separated by fat and connective tissue (suspensory ligaments or Cooper’s ligaments)
• Lobules –the smaller compartments of lobes and contain alveoli
• Alveoli –the milk secreting glands
• Lactiferous Ducts- site of milk expression
• Lactiferous Sinus -expansion of the mammary ducts where milk is stored before draining from the breast
• Nipple –pigmented projection where lactiferous ducts exit and surrounded by areola

Milk production occurs in the alveoli and passes from secondary tubules into mammary ducts to lactiferous sinuses which drain into lactiferous ducts. Milk is further pulled from these sinuses by the suckling of an infant who has latched on to the areola. Milk production is stimulated by the hormone prolactin.

Figure 10.9 Anatomy of the breast during lactation. The figure depicts external and internal anatomy of the breasts with several structures labeled.

1. Describe the series of ducts that milk flows through from production to exiting the nipple.
2. What hormones stimulate milk production?
3. What hormone stimulates ovulation?
4. Name the milk secreting glands.
5. List the parts of the vulva.
6. What are the 3 layers of the uterine wall?

Lab Exercise 10: Reproductive Anatomy

Lab Activity 10.1: Identification of the Male and Female Reproductive Structures

On the torso models or individual male and female reproductive models identify the following structure:

Figure 10.10 Model of the female reproductive system, medial view of a midsagittal section.

Lab Activity 10.2: Spermatogenesis

Spermatogenesis is the production of sperm cells that occurs in the seminiferous tubules of the testes. Mitosis of diploid (2n) spermatogonia is the first step in spermatogenesis. Spermatogonia differentiates into primary spermatocytes. Primary spermatocytes replicate their DNA, enter meiosis, and become secondary spermatocytes with only 23 chromosomes. The secondary spermatocytes enter meiosis II and form 4 haploid (n) spermatids. These haploid spermatids develop into sperm during spermatogenesis.

Figure 10.11: Spermatogenesis (a) Mitosis of a spermatogonia stem cell involves a single cell division that results in two identical, diploid daughter cells (spermatogonia to primary spermatocyte). Meiosis has two rounds of cell division: primary spermatocyte to secondary spermatocyte, and then secondary spermatocyte to spermatid. This produces four haploid daughter cells (spermatids). (b) In this electron micrograph of a cross-section of a seminiferous tubule from a rat, the lumen is the light-shaded area in the center of the image. The location of the primary spermatocytes is near the basement membrane, and the early spermatids are approaching the lumen.

Using the image above, describe and draw the divisions that take place during spermatogenesis. Include the name at each stage and whether they are diploid or haploid. Start with Spermatogonium and end with Spermatozoa.

*Provide your drawing of spermatogenesis in the space provided above.

Lab Activity 10.3: Label the Parts of a Single Sperm

Figure 10.12 Anatomy of a Sperm

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Lab Activity 10.4: The Ovarian Cycle

The ovarian cycle or oogenesis and follicular development is a cycle of maturation of oocytes and follicles. This process takes 28-days and corresponds to the menstrual cycle. The ovarian cycle involves the processes of oogenesis (the production of female gametes) which begins before birth and folliculogenesis (follicular development) which occurs from puberty to menopause.

Oogonia are diploid stem cells that form during female fetal development and give rise to female egg cells (oocytes). Gametogenesis, or more specifically, oogenesis, is the name of this maturation process. Mitotic division of a few oogonia give rise to primary oocytes. Primary oocytes remain arrested in meiosis I until puberty, when the female will undergo her first ovulation, or release of an oocyte from the ovary. Each month from puberty until menopause, primary oocytes develop to form primary follicles and mature to form secondary follicles. The secondary follicle enlarges to becoming a mature (graafian) follicle. Just before ovulation the primary oocyte completes meiosis I and produces two haploid cells of unequal size, the first polar body and a secondary oocyte.

Figure 10.13: Hormonal Regulation of Ovulation The hypothalamus and pituitary gland regulate the ovarian cycle and ovulation. GnRH activates the anterior pituitary to produce LH and FSH, which stimulate the production of estrogen and progesterone by the ovaries.

The mature follicle ruptures and releases the secondary oocytes into the pelvis, ovulation. If a sperm cell is present and penetrates the secondary oocyte, meiosis II resumes and the cell divides into two haploid cells. The later cell is the haploid ovum, and the smaller cell is the second polar body. Ovulation is triggered by a surge of luteinizing hormone and will continue monthly throughout the life of the female.

Figure 10.14 Oogenesis The unequal cell division of oogenesis produces one to three polar bodies that later degrade, in addition to a single haploid ovum which results only if there is penetration of the secondary oocyte by a sperm cell.

Using the image above, describe and draw the divisions that take place during oogenesis. Include the name at each stage and whether they are diploid or haploid cells. Start with Oogonia and end with the Ovum.

*Use the space above to draw the sequence of events for oogenesis.

Lab Activity 10.5: Histological Observation of Reproductive Tissues

View each slide provided by your instructor, identifying key features of each tissue.

Lab Activity 10.6: Fetal Pig Dissection (Optional)

Supplies needed: Gloves, scalpel/scissors, blunt probe, tweezers

For the FEMALE fetal pig reproductive system:

1. Locate the left and right ovaries, the small, pea-shaped structures at the base of the abdominal cavity.
2. Note the very small, convoluted tubules next to each ovary. These are the fallopian tubes.
3. The fallopian tubes connect to the much larger tubes that extend to the base of the bladder. These larger tubes are the uterine horns and are not present in humans. These allow animals like pigs, dogs, etc. to have large multiple pregnancies (litters).
4. Attached to each uterine horn is a large, membranous sheet of tissue. This is the broad ligament.
5. To see the rest of the uterus and the rest of the female reproductive system, make a medial incision through the pubis bone. You can feel the cavity where the reproductive structures lie by placing your blunt probe into the opening at the base of the bladder. You need to cut through the bone down to your probe to see the remaining structures.
6. Observe the body of the uterus after you have made your incision. Note also the urethra coming from the base of the bladder.
7. The vagina attaches to the base of the uterus. Note also the rectum lying posteriorly to the vagina.
8. Trace the vagina down to the point at which it merges with the urethra. This last section, which provides a common opening to the outside for both the vagina and urethra, is called the urogenital sinus, not present in humans. The urinary and reproductive systems remain separate in a human female.
9. Once you have completed this dissection find a male specimen and identify the components of that system.

For the MALE fetal pig reproductive system:

1. Locate the scrotum, the sac of tissue lying outside the abdominal cavity between the legs.
2. Within the abdominal cavity, locate the gonadal arteries. Trace these arteries to the point where they go through the abdominal wall. The opening where the gonadal arteries go through the abdominal wall is the beginning of the inguinal canal. Note also that another tube is coming out of the inguinal canal at the same point where the gonadal artery is going in. This other tube is the vas deferens.
3. Make a small incision along one inguinal canal so that you can expose the testis.
4. Note the membranous tube that covers all the structures. This is the rest of the inguinal canal. Peel off this membrane so that you can see the structures within.
5. The testis is the small, dark, bean-shaped structure at the end of the inguinal canal.
6. The epididymis is the tightly coiled tube on one side of the testis. Trace the epididymis around to the other side of the testis. Note the tube becomes uncoiled and extends through the inguinal canal to the bladder. This is the vas deferens.
7. To see the rest of the male reproductive system, make a medial incision through the pubis bone. You can feel the cavity where the reproductive structures lie by placing your blunt probe into the opening at the base of the bladder. You need to cut through the bone down to your probe to see the remaining structures.
8. Find the urethra coming off the base of the bladder. Note also the rectum lying underneath the urethra.
9. Trace the urethra down until you see a small white bulge of tissue on each side of it. These bulges of tissue are the bulbourethral (Cowper’s) gland.
10. Continue to trace the urethra down through the rest of the body. Note that at the base, the urethra bends and continues up toward the umbilical cord. Beyond this bend, the urethra is now the penis.
11. Locate the preputial orifice, the external opening of the penis located just below the umbilical cord.
12. Once you have completed this dissection find a female specimen and identify the components of that system.

Clean up procedure:

• Dispose of all organic debris in the appropriate biohazard containers and clean the dissecting instruments and tray with soap and water before leaving the laboratory. Do not forget to wash your hands with water and soap, and to disinfect the lab bench.

Post-Lab 10 Review

Post-Lab Activity 10.1 Review Questions

1. Which structures make up the duct pathway of the male reproductive system?
2. Which structure produces spermatozoa?
3. What is the function of the prostate gland?
4. Which structural feature of the penis is removed during a circumcision?
5. What is the name of the erectile tissue in the penis? Describe the shape and position of these tissues.
6. List the structures a spermatocyte will pass through from the testis to the urethra?
7. What are the 3 accessory glands in males and what is their function?
8. Describe the difference between the dartos and the cremaster muscles.
9. What structure in the female reproductive system is made of erectile tissue?
10. Describe the location of the uterus within the pelvic cavity. Which structure sits anterior and posterior to it? What are the three main parts of the uterus?
11. What are fimbriae and where are they located?
12. What type of tissue lines the vaginal canal?
13. Where is the cervix located?
14. Describe the phases of the female reproductive cycle, including the predominant hormones in each phase.
15. Describe the production and flow of milk in the process of lactation. Which hormone is involved with milk production?
16. Name the structures associated with milk production.

Post-Lab Activity 10.2: Identify the Structures of the Mammary Glands

Use the image below to identify the lettered structures.

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Figure 10.15 Anatomy of the breast during lactation.

Post-Lab Activity 10.3: Identify the Structures of the Internal Testis

Using the image below, identify the lettered structures on the testis.

Figure 10.16: Internal anatomy of the testis.

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Post-Lab Activity 10.4: Identify Structures of the Female Reproductive System

Figure 10.17 The major organs of the female reproductive system are located inside the pelvic cavity and include the ovaries, uterine tubes, uterus, vagina, and pudendum.

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Post-Lab Activity 10.5: Reproductive Histology

1. The uterus shown is in the Luteal phase. Describe what is happening to the layers (endometrium, myometrium, periosteum) of the uterus during this phase. Identify the glands of the endometrial layer.

Figure 10.18 Histology of the uterus. Photograph by Gina Profetto

1. The image below is a histological prep of a penis. Locate the urethra and the erectile tissue within this image.

Figure 10.19 Histology of the penis. Photograph by Gina Profetto

1. The image below shows a testis with an attached epididymis. Locate the epididymis. Circle where sperm is stored.

Figure 10.20 Histology of the testis. Photograph by Gina Profetto

4. Using the image of the oviduct/ fallopian tubes below, identify the three layers of muscle: mucosa, muscularis, and serosa.

Figure 10.21 Histology of the oviduct. Photograph by Gina Profetto