SLG-BIO2-LG4-4.1-4.2 Human Male Reproductive System PDF

LEARNING GUIDE 04 HUMAN MALE REPRODUCTIVE SYSTEM Subject Code: BIOLOGY 2 Learning Guide Code: 4.0 HUMAN MALE REPRODUCTIVE SYSTEM Lesson Code: Lesson 4.1 Human Male Reproductive Anatomy Time Frame: 30 minutes MATERIALS NEEDED To complete this module, you need the follow...

LEARNING GUIDE 04 HUMAN MALE REPRODUCTIVE SYSTEM Subject Code: BIOLOGY 2 Learning Guide Code: 4.0 HUMAN MALE REPRODUCTIVE SYSTEM Lesson Code: Lesson 4.1 Human Male Reproductive Anatomy Time Frame: 30 minutes MATERIALS NEEDED To complete this module, you need the following: 1. pen; 2. paper; 3. phone/tablet/laptop; 4. Adobe scanner mobile app; 5. Moodle Learning Management System account; 6. stable internet connection and; 7. Biology: A Global Approach by Campbell et al. (2015). TARGET After completing this module, you are expected to: 1. identify key male reproductive structures and their functions; and 2. discuss how the hypothalamic-pituitary-gonadal (HPG) axis regulates the male HOOK reproductive system. HOOK IS IT ALL ABOUT SEX? A dad’s tiny sperm breaks through the surface of a mom’s huge egg. Voilà! A new son, or daughter, will be born in nine months. Like most other multicellular organisms, human beings reproduce sexually. In human sexual reproduction, males produce sperm and females produce eggs, and a new offspring forms when a sperm unites with an egg. How do sperm and eggs form? And how do they arrive together at the right place and time so they can unite to form a new offspring? These are the features of the reproductive system. Adapted from http://www.pdimages.com/web9.htm. © Wikimedia.org. THINK IT OVER Why do organisms need to reproduce? What would eventually happen to a species if every member suddenly lost its ability to reproduce? PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 1 of 11 Biology 2-G10: SY 2020-21  IGNITE Reproduction is one of the key defining characteristics of life. As indicated in the previous learning guide, sexual reproduction is dependent on the production of gametes. All animals and plants have special organs for reproduction in which the gametes are formed. In humans, these special organs are called gonads; the male gametes are formed in the testis; the female gametes are formed in the ovary. The succeeding section focuses on the human male reproductive anatomy. THINK IT OVER Do you ever ask yourself what makes a male a male and a female a female? The male’s external reproductive organs are the scrotum and penis. The male’s internal reproductive organs are the gonads, which produce sperm and hormones, accessory glands that secrete products needed for sperm motility, and ducts that carry sperm and other glandular secretions. Figure 4.1a presents a view of the male reproductive system. Figure 4.1a. Reproductive Anatomy of the Human Male (side view). The figure shows the ejaculatory duct, seminal vesicles, and the bulbourethral gland that produce semen. The figure also shows the other major structures of the male reproductive system. © 2003 CC-BY-SA 3.0. Testes. In male animals, sperm are the gametes produced from primordial germ cells. They are developed in the differentiating male gonads, the testes, which consist of highly coiled connective tissue tubes called seminiferous tubules, which are the site of sperm production (Figure 4.1b). The sperm together with their associated accessory cells called Sertoli cells line the perimeter of the tubules and as they grow and develop, they migrate towards the lumen of the tubules. Between the tubules are vascularized connective tissue cells called Leydig cells which are responsible for secretion of reproductive hormone (Figure 4.1c). The sperm eventually enter the lumen in order to be released either into a female or the immediate external environment. The normal production of sperm cannot occur at the body temperatures of most mammals hence their testes descend through the abdominal cavity in a sac called scrotum, where the temperature is cool enough to produce viable sperm. PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 2 of 11 Biology 2-G10: SY 2020-21 Figure 4.1b. Cross-Section of a Testicle. This drawing includes a testis, epididymis, and vas (or ductus) deference. The three structures are connected to create a tract through which sperm can travel. Adapted from Testicle, by NCI, 2001, https://visualsonline.cancer.gov/details.cfm?imageid=1769. © 2001 by the NCI. Figure 4.1c. Cross-Section of a Seminiferous Tubule. A cross-sectional drawing of a testis and seminiferous tubule shows the lining of Sertoli cells and different stages of sperm development. Adapted from Anatomy & Physiology, by OpenStax College, 2013, http://cnx.org/content/col11496/1.6/. © 2013 CC- BY-SA 3.0. PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 3 of 11 Biology 2-G10: SY 2020-21  Ducts. From the seminiferous tubules of each testis, sperm pass into a coiled duct called epididymis, which stores sperm while they develop. During ejaculation, sperm are propelled through the muscular vas deferens into the abdomen and loops around the urinary bladder joining with the seminal vesicle to form a short ejaculatory duct. This common duct receives secretions from other glands and wends its way through the urethra in order to deliver sperm and seminal fluid for the fertilization reaction. Accessory Glands. The sperm plus three sets of glandular secretions help form the semen, the fluid ejaculated from the penis during orgasm. The two seminal vesicles secrete a thick, yellowish fluid that protects and nourishes the sperm. This contributes about 60% of the total volume of semen. The prostate gland secretes a milky, alkaline fluid directly into the urethra through several small ducts to form the seminal fluid. The bulbourethral glands secrete a clear mucus before ejaculation to neutralize the acidic urine remaining in the urethra. About 5 mL (50-120 million sperm per mL) of semen are discharged during a typical ejaculation. Figure 4.1d illustrates the two processes of ejaculation and summarizes the production of semen and its expulsion. Figure 4.1d. The Two Stages of Ejaculation. Adapted from Biology Concepts and Connections (p. 539), by Campbell et al., (2003), Pearson Education (Asia) Pte, Ltd. © 2003 by the Pearson Education, Inc. PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 4 of 11 Biology 2-G10: SY 2020-21  Penis. The human penis consists mainly of three cylinders of spongy erectile tissue. During sexual arousal, the erectile tissue fills with blood from the arteries, causing an erection. The head of the penis or glans consists of a thinner skin covering which is richly supplied with nerve endings hence it is highly sensitive to stimulation. The glans is surrounded by a fold of skin called prepuce or foreskin (Figure 4.1e). The surgical removal of the prepuce or circumcision is commonly performed for religious and health reasons. Figure 4.1e. Structure of the Penis. This section shows the internal anatomy of the penis and related structures. The corpus spongiosum is the column of erectile tissue that contains the urethra. The corpora cavernosa are the other two columns that erect the penis. Adapted from “An Atlas of Anatomy,” by J.C.B. Grant, 1962. Go to the following link to visualize the functional anatomy of the reproductive system of the human male. https://www.youtube.com/watch?v=k60M1h-DKVY PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 5 of 11 Biology 2-G10: SY 2020-21 Subject Code: BIOLOGY 2 Learning Guide Code: 4.0 HUMAN MALE REPRODUCTIVE SYSTEM Lesson Code: Lesson 4.2 Hormonal Control of the Male Reproductive System Time Frame: 30 minutes The maintenance of a constant internal environment is called homeostasis. Perhaps the most familiar homeostatic control system is based around the principle of feedback mechanism. The components of a feedback system are shown in Figure 4.2a. There are three major components: a receptor, an integrating center, and an effector. The receptor is accountable for detecting change in the environment of the animal, either the external environment in which it lives or its internal environment (e.g. change in testosterone levels). The integrating center is actually the brain or spinal cord. As will be discussed later, the hypothalamic region of the brain is the integrating center for the control of the male reproductive system in humans. An effector is a general term given to structures which generate a biological response. Figure 4.2a. The Basic Components of a Feedback System and their Arrangement. The endocrine system together with the nervous system make up the control and coordinating systems of animals. The endocrine system works by transmitting chemical signals while the nervous system utilizes chemical messengers at synapses. The endocrine system secretes specific chemical messengers called hormones. The hormones are carried either in the bloodstream or in the body fluids of animals to their target organs where they exert their biological effect. The typical hormonal system is seen to consist of three principal glands or groups of glands: the hypothalamus; the pituitary gland; and the peripheral endocrine glands. Figure 4.2b. The Hypothalamic-Pituitary Axis. The pituitary gland is located at (a) the base of the brain and (b) connected to the hypothalamus by the pituitary stalk. Adapted from © National Cancer Institute; © Gray’s Anatomy. PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 6 of 11 Biology 2-G10: SY 2020-21  The Hypothalamic-Pituitary-Gonadal (HPG) Axis. The hypothalamus is a part of the brain that sits beneath the thalamus. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland. The secretions of the hypothalamus are transported to the pituitary gland. There are two types of secretions: those that are released into the anterior pituitary gland and those released into the posterior pituitary gland (Figure 4.2b). Another important group of secretions produced by the hypothalamus are the releasing hormones. As the name suggests, their function is to influence the release of hormones from the pituitary. Alternatively, release of hormones may be inhibited by release-inhibiting hormones secreted by the hypothalamus. The secretion levels are controlled via a negative feedback mechanism as illustrated in Figure 4.2c. Figure 4.2c. Hormones Control Sperm Production in a Negative Feedback System. GnRH, gonadotropin-releasing hormone; FSH, follicle-stimulating hormone; LH, luteinizing hormone; +, stimulatory; –, inhibitory. Adapted from Biology (p. 1291), by OpenStax College, 2013, Rice University. © 2013 by Rice University. The Hormonal Control of Sperm Production. Much of what is known about the control of sperm production comes from studies on mammals as summarized in Figure 4.2c. As previously discussed, the Sertoli cells are a group of accessory cells in the testes that are principally involved in the process of spermatogenesis, which nourish developing sperm cells. The Sertoli cells are stimulated by follicle-stimulating hormone (FSH) which is released from the anterior pituitary gland. FSH release is promoted by gonadotropin-releasing hormone (GnRH), which is released from the hypothalamus. FSH is thought to stimulate the Sertoli cells to release substances which promote spermatogenesis. The Sertoli cells are also stimulated by testosterone, which is produced by the Leydig cells of the testes. Testosterone is a steroid hormone and it is essential for the growth and development of the male reproductive system. The release of testosterone and other androgens is under the control of another anterior pituitary hormone called luteinizing hormone (LH). Like FSH, LH is itself under the control of GnRH. Testosterone regulates the production of GnRH, FSH, and LH through negative feedback mechanisms. When the sperm count is too high, Sertoli cells secrete the hormone inhibin which reduces FSH secretion from the anterior pituitary gland. This will cause spermatogenesis to slow down. But when the sperm count reaches 20 million per mL, the Sertoli cells cease the release of inhibin, and the sperm count increases. Under the control of this chemical regulating system, the testes produce hundreds of millions of sperm every day, from puberty well into old age. PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 7 of 11 Biology 2-G10: SY 2020-21  THINK IT OVER The human male (all male mammals, in fact) produce in a lifetime billions of individual sperm cells. Yet only a few, if any, of these will ever fertilize an egg and propagate the species. Isn’t this a wasteful process, considering the amount of protein and other organic molecules that go into producing all these sperm? Why should such an arrangement–billions of sperm for perhaps hundreds of eggs–have evolved? You may also refer to your textbook (Campbell et al., 2015) for other illustrative examples and more detailed explanations (pp. 1055 – 1056; pp. 1060 – 1061). You can also visit the following link to visualize the hormonal regulation of male reproduction. https://www.youtube.com/watch?v=GC58kOcsx9U NAVIGATE It is your time to work on the following figure by providing the structure and function of the lettered parts of the reproductive anatomy of the human male. Level I: Knowledge/Comprehension (10 pts) Figure 4. Reproductive Anatomy of the Human Male. Adapted from Biology: A Global Approach (p. 1055), by Campbell et al., (2018), Pearson Education, Ltd. © 2018 by the Pearson Education, Ltd. Structure Major Function A. Testis (or seminiferous tubule) male gonad in which sperm and hormones are produced B. Prostate Gland secretes an acid-neutralizing component of semen C. Scrotum maintains the testes at the lower temperature required for spermatogenesis D. Vas Deferens serves as a tube in which sperm travel from the epididymis to the urethra E. Urethra serves as the exit tube for the reproductive system PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 8 of 11 Biology 2-G10: SY 2020-21 Level II: Application/Analysis (10 pts) A partial sentence regarding the hormonal control of the testes is provided, read this statement carefully. Write the word (or words) in the blank by selecting the answer from among the choices that best completes the statement. HOW THE MALE GONADAL AXIS WORKS? anterior pituitary GnRH Leydig cells negative scrotum gland feedback posterior pituitary inhibin Sertoli cells positive feedback testicles gland spermatogenesis testosterone sperm cells decreased increased The hypothalamus secretes ____________________ which travels down to the ____________________ where it binds to its receptors. This causes release of LH and FSH that travel in the bloodstream to the ____________________. LH stimulates ____________________ in the testicles to produce ____________________ which is required for ____________________ and many other important biological processes. FSH stimulates ____________________ to produce androgen and ____________________ which helps support spermatogenesis and inhibits production of GnRH, FSH, and LH. High levels of testosterone and inhibin cause ____________________ on the pituitary and hypothalamus. This results in ____________________ production of LH and FSH. Level III: Synthesis/Evaluation (10 pts) Answer the following questions in complete sentences. 1. What would happen if the epididymis leading to both testes of a male was damaged or blocked? Explain your answer. __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ 2. If each vas deferens in a male was surgically sealed off, what changes would you expect in sexual response and ejaculate composition? __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 9 of 11 Biology 2-G10: SY 2020-21  KNOT To summarize, the human male reproductive system consists of testes, ducts that carry gametes, and structures for copulation. The testes produce sperm which are expelled through ducts during ejaculation. Sertoli and Leydig cells are also found in the testes. Sertoli cells are principally involved in spermatogenesis supplying nutrition to developing cells. Several glands contribute to the formation of seminal fluid that carries, nourishes, and protects developing sperm. This fluid and the sperm constitute the semen. Hormones control sperm production by the testes. Influenced by signals from other parts of the brain, the hypothalamus secretes GnRH that regulates release of FSH and LH by the anterior pituitary gland. FSH promotes spermatogenesis while LH promotes secretion of testosterone. Testosterone in the bloodstream helps maintain homeostasis by a negative feedback mechanism inhibiting secretion of the GnRH, FSH, and LH. For additional assessment, complete the negative feedback loop below for the hormonal regulation of the male reproductive system. 1. 2. 3. 4. REFERENCES Biology LibreTexts. (2019, May 19). Retrieved from Structures of the Male Reproductive System: https://bio.libretexts.org/Courses/Butte_College/BC%3A_BIOL_2_- _Introduction_to_Human_Biology_(Grewal)/Text/22%3A_Reproductive_System/22.03%3A _Structures_of_the_Male_Reproductive_System PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 10 of 11 Biology 2-G10: SY 2020-21 Campbell, N., Reece, J., Mitchell, L., & Taylor, M. (2003). Reproduction and Embryonic Development. In N. Campbell, J. Reece, L. Mitchell, & M. Taylor, Biology Concepts & Connections (pp. 532- 561). Philippines: Pearson Education (Asia) Pte, Ltd. Kay, I. (1998). Homeostasis: The Central Concept in Physiology. In I. Kay, Introduction to Animal Physiology (pp. 1-8). UK: BIOS Scientific Publishers, Ltd. Kay, I. (1998). Endocrine Function. In I. Kay, Introduction to Animal Physiology (pp. 55-71). UK: BIOS Scientific Publishers, Ltd. Kay, I. (1998). Reproduction. In I. Kay, Introduction to Animal Physiology (pp. 175-192). UK: BIOS Scientific Publishers, Ltd. OpenStax College. (2013). Hormonal Control of Human Reproduction. In O. College, Biology (pp. 1290-1291). Houston, Texas: Rice University. Reece, J., Urry, L., Cain, M., Wasserman, S., Minorsky, P., & Jackson, R. (2014). Animal Reproduction. In J. Reece, L. Urry, M. Cain, S. Wasserman, P. Minorsky, & R. Jackson, Campbell Biology (pp. 1013-1036). USA: Pearson Education, Inc. Prepared by: Reviewed and Approved by: JOEL C. MAGDAY, JR. MICHELLE B. DUCUSIN Special Science Teacher III Special Science Teacher V/Team Lead (Biology) PSHS-CAGAYAN VALLEY CAMPUS PSHS-ILOCOS REGION CAMPUS PHILIPPINE SCIENCE HIGH SCHOOL SYSTEM Page 11 of 11 Biology 2-G10: SY 2020-21