differentiate. The epididymis is a coiled tube found along the outer edge of the testis where the sperm mature. 3. Testosterone is a male sex hormone produced in the interstitial cells of the testes. It is responsible for stimulating spermatogenesis and regulating and influencing the development of secondary male sexual characteristics and is associated with sex drive levels. 4. The hypothalamus and the pituitary gland control the production of sperm and male sex hormones in the testes. Negative feedback systems ensure that adequate numbers of sperm cells and a constant level of testosterone are maintained. The gonadotropic hormones, which regulate the functions of the testes, are produced and stored in the pituitary glands. Male follicle-stimulating hormone (FSH) stimulates the production of sperm cells in the seminiferous tubules. Male luteinizing hormone (LH) promotes the production of testosterone by the interstitial cells. At puberty, the hypothalamus secretes gonadotropin-releasing hormone (GnRH), which activates the pituitary gland to secrete and release FSH and LH. 5. The sources of energy for developing and mature sperm are fructose in semen in fluid produced by seminal vesicles, mitochondia in sperm, and Sertoli cells. 6. Luteinizing hormone (LH) is released from the pituitary gland at puberty. LH acts on the interstitial cells to produce testosterone. In turn, the testosterone itself increases sperm production. Once high levels of testosterone are detected by the hypothalamus, a negative feedback system is activated. Testosterone inhibits LH production by deactivating the hypothalamus. The hypothalamus releases less gonadotropin-releasing hormone (GnRH), which slows the production and release of LH and leads to less testosterone production. The feedback loop for sperm production is not well understood. It is believed that FSH acts on Sertoli cells, which produce a peptide hormone that sends a feedback message to the pituitary, inhibiting production of FSH. 7. (a) Yes, he would produce semen since the tissues involved in spermatogenesis (the seminiferous tubules) are not affected by the surgery. (b) Testosterone is produced by the testes, which is not affected by a vasectomy, so he would continue to produce testosterone. (c) A vasectomy is performed for pregnancy prevention. 16.2 THE FEMALE REPRODUCTIVE SYSTEM Web Activity: Simulation Structures of the Female Reproductive System (Page 521) This simulation provides an interactive diagram of the female reproductive system, from a side view. Students should produce a diagram similar to that shown on page 528 of the Student Book, but only the vagina, ovaries, cervix, Fallopian tubes, uterus, and endometrium need to be labelled. (Page 522) 1. Follicles are the structures in the ovary containing the oocyte. 2. The corpus luteum is formed by follicles that surround the dominant follicle cell but remain in the ovary after release of the secondary oocyte. The corpus luteum secretes the hormones estrogen and progesterone, which are essential for pregnancy. If pregnancy does not occur, the corpus luteum degenerates after about 10 days. Copyright 2008 Thomson Nelson Unit 30 B Solutions Manual 259
Mini Investigation: Microscopic Examination of the Ovary (Page 523) (a) to (c) Students responses will vary with the slide viewed. Below are examples of diagrams and labelling of immature follicles. The fluid-filled cavity (antrum) is absent or undeveloped and the follicle is surrounded by spindle-shaped that are characteristic of an immature follicle. fluid-filled cavity (d) The follicle depicted below is mature. There is a distinct, large, fluid-filled cavity (antrum) and an eccentric oocyte both of these attributes are characteristic of a mature follicle. fluid-filled cavity (e) fully-formed corpus luteum developing OR degenerating corpus luteum (f) As the follicle develops through the first half of the cycle, the increases in size and divides to form the secondary oocyte. As well, the follicle cells increase significantly in number and produce ever-increasing amounts of estrogen, which stimulates the endometrial lining to grow in anticipation of conception and implantation. This sequence of diagrams demonstrates the events leading up to and including ovulation. Students should arrange their diagrams in a similar fashion. 260 Unit 30 B Solutions Manual Copyright 2008 Thomson Nelson
Web Activity: Case Study Tubal Ligation (Page 523) Tubal ligation is the most common procedure for blocking the Fallopian tubes. Since the ovum cannot descend and the sperm cannot reach the ovum, pregnancy is not possible after tubal ligation. The Pomeroy technique was developed by Dr. Ralph Pomeroy about 100 years ago and is still the most common procedure. Tubal ligation involves tying a segment of the Fallopian tube and removing it. With the Pomeroy method, part of the tube is elevated to create a loop or knuckle, as shown in Figure 4 on page 523 of the Student Book. This is tied with an absorbable ligature, and the raised section of the tube is cut out. The cut ends of the Fallopian tube separate as the ligature dissolves. The peritoneum (the lining of the abdominal cavity) grows over the cut ends of the tubal segments. As a result, the cut segments cannot reattach to each other. Pomeroy tubal ligation is most often performed after delivery by cesarean section. Since the cut segments of the Fallopian tube remain healthy, they can also be successfully rejoined should the patient wish to become pregnant in the future. Teachers might also wish to have students research other technologies to prevent pregnancy, including hormone manipulation (the Pill), mechanical barriers (condoms and the diaphragm), and spermicides. Sample responses concerning these different methods are available on the Nelson Web site at www.science.nelson.com. (Page 526) 3. Estrogen and progesterone are two female sex hormones. Estrogen promotes the development of female secondary sex characteristics, including the development of body hair and breasts and the thickening of the endometrium. Progesterone also stimulates the endometrium and inhibits ovulation and uterine contractions. 4. The gonadotropic hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate the production of estrogen and progesterone. FSH stimulates follicle development in the ovary. The follicles secrete estrogen. After ovulation, LH stimulates the transformation of the remaining follicles into the corpus luteum. The corpus luteum secretes both estrogen and progesterone. Lab Exercise 16.B: Hormone Levels during the Menstrual Cycle (Pages 527 528) Analysis and Evaluation 1. (a) X and Z are gonadotrophic hormones: hormone X is follicle-stimulating hormone (FSH), and hormone Z is luteinizing hormone (LH). (b) W and Y are ovarian hormones: hormone W is estrogen, and hormone Y is estrogen and progesterone. (c) W (estrogen) and Y (estrogen and progesterone) exert negative feedback effects. Copyright 2008 Thomson Nelson Unit 30 B Solutions Manual 261
2. (d) See graph below. (e) Day 14 is ovulation day. (f) The temperature decreases before ovulation and rises above normal body temperature during ovulation. (g) Body temperatures with a functioning corpus luteum are higher than those without. 3. (h) Ovulation occurs at X, and menstruation occurs at Z. (i) Estrogen is being produced at W and Y. (j) Estrogen and progesterone are produced by the corpus luteum at Y. 4. (k) LH increases progesterone and estrogen levels by stimulating the formation of the corpus luteum. The corpus luteum produces both female sex hormones. Section 16.2 Questions (Page 529) 1. Ovulation is the release of an egg from a follicle held within the ovary. The follicles are made of two types of cells, the and. The provide nutrients for the. The undergoes meiosis I, splitting into two cells. One cell receives the majority of the nutrients and cytoplasm and becomes the secondary oocyte. The other cell forms a polar body and soon dies because it receives little cytoplasm. The follicle pushes outward against the wall of the ovary, eventually bursting it and releasing the secondary oocyte, which then enters the oviduct. In the oviduct, the secondary oocyte undergoes meiosis II. Meiosis II again forms two cells. The one that receives most of the cytoplasm and nutrients is an ovum, and the other cell is the polar body, which soon dies. 2. The flow phase of the menstrual cycle is marked by the shedding of the endometrium. This is the only part of menstruation to occur externally. This process takes about five days. This next phase is known as the follicular phase, during which time the follicle develops within the ovary. This phase lasts between 6 and 13 days and is characterized by high concentrations of the hormone estrogen. This phase is followed by ovulation and finally by the luteal phase. The start of the luteal phase is signalled by the development of the corpus luteum. Estrogen levels decline when the oocyte bursts from the ovary but increase when the corpus luteum forms. The luteal phase lasts for about 14 days and prepares the uterus to receive a fertilized egg. If fertilization does not occur, estrogen and progesterone levels fall and mild uterine 262 Unit 30 B Solutions Manual Copyright 2008 Thomson Nelson
contractions occur. The lining of the endometrium breaks away from the wall of the uterus because of these contractions and is shed again during the next flow phase. 3. A negative control feedback system is one in which the products of the reaction inhibit the initial stimulating agents. In the case of the female reproductive system, follicle-stimulating hormone (FSH) stimulates the production of estrogen via follicular development. As the estrogen concentration rises, a message is sent to the pituitary gland to stop the production and secretion of FSH. 4. Low secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus may affect the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland. If these hormones are not released, the menstrual cycle may not be initiated. Without FSH, follicle development may not be stimulated, in which case, estrogen would not be produced. Without estrogen, the endometrium would not be developed. Also, without estrogen, the next phase of menstruation, ovulation and the formation of the corpus luteum, would not occur because estrogen would not stimulate the LH-producing cells of the pituitary gland. 5. A Pap smear is a cell sample taken from the cervix and is used to diagnose cervical cancer. 6 (a) After this procedure, although ovulation would occur, the ovum would not be able to reach the uterus to be fertilized and implant. (b) Yes, a woman will ovulate following a tubal ligation because hormones are still produced to trigger the menstrual and ovulation cycles. The difference is that the ovum cannot travel down the Fallopian tube to the uterus. 7. Estrogen and progesterone in contraceptive pills inhibit ovulation by suppressing the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by the pituitary gland. They also stimulate the cervical mucus to thicken, making it difficult for sperm to get to the egg, and change the lining of the uterus, making implantation difficult. 8. If identical triplets are born, there will be a single ovum; therefore, one corpus luteum will be present. If the triplets are fraternal, three corpus lutei will be found. 9. Women may take hormone therapy in which their levels of estrogen are maintained after menopause to prevent the side effects of the reduced amount of this hormone in the body. Some side effects of the therapy, however, include breast cancer, heart disease, and stroke. Increasing calcium in the diet may be another factor that could reduce the possibility of bone loss, resulting in osteoporosis. Regular exercise can also aid in increasing bone density. 10. Using certain hormones in livestock may be detrimental to human health. If steroid hormones are used, these may be passed along into humans through their diet since they are not as easily digested when compared with protein hormones. Growth hormones being used in cattle will increase the overall size of the animal, but the same hormones may be passed on in the milk and meat products from these animals. This could cause cancer in humans due to the increased rate of cell division that these hormones may cause. 16.3 FERTILIZATION, PREGNANCY, AND BIRTH (Page 532) 1. See Figure 3 on page 531 of the Student Book for an example. The amnion is a fluid-filled extraembryonic structure that surrounds and protects the embryo. The allentois is an extraembryonic structure that provides blood vessels to the placenta. Copyright 2008 Thomson Nelson Unit 30 B Solutions Manual 263