Science 10 Unit 13: The Reproductive System - Study Guide PDF

Unit 13 The Reproductive System: Parts and Function Table of Contents Table of Contents 1 The Reproductive System: Parts and Function 3 Essential Questions 4 Review...

Unit 13 The Reproductive System: Parts and Function Table of Contents Table of Contents 1 The Reproductive System: Parts and Function 3 Essential Questions 4 Review 4 Lesson 13.1: Sexual Reproduction in Animals 5 Objective 5 Warm-Up 5 Learn about It 6 Key Points 13 Web Links 13 Check Your Understanding 13 Challenge Yourself 14 Lesson 13.2: The Female Reproductive System 15 Objective 15 Warm-Up 15 Learn about It 16 Key Points 21 Web Links 21 Check Your Understanding 22 Challenge Yourself 22 Lesson 13.3: The Male Reproductive System 23 Objective 23 Warm-Up 23 Learn about It 24 Key Points 29 Web Links 29 1  Check Your Understanding 30 Challenge Yourself 30 Lesson 13.4: Spermatogenesis and Oogenesis 31 Objectives 31 Warm-Up 31 Learn about It 32 Key Points 36 Web Links 37 Check Your Understanding 37 Challenge Yourself 38 Laboratory Activity 39 Performance Task 43 Self Check 44 Key Words 45 Wrap Up 46 Photo Credits 47 References 47 2 GRADE 10 | SCIENCE Unit 13 The Reproductive System: Parts and Function Throughout the history of life, organisms have evolved and changed forms over a long period of time. This change and the propagation of species will not have been possible without the ability and capacity of organisms to reproduce in order to propagate their own species. Reproduction in animals can either be sexual reproduction, or asexual reproduction. Organisms have developed mechanisms to ensure that they are capable of reproducing. What are the structures that animals have for reproduction? How do they undergo sexual reproduction? 3  Essential Questions At the end of this unit, you should be able to answer the following questions. How do animals undergo sexual reproduction? What structures do humans and animals have in the reproductive system? What are the differences between the male and the female reproductive system? How do sex cells develop? Review Organisms can undergo either asexual or sexual reproduction. In asexual reproduction, sex cells of males and females fuse in the process of fertilization. The sex cells of males are sperm cells, and the sex cells of females are egg cells. Fertilization results in the formation of a zygote, which will eventually develop into a new organism. 4  Lesson 13.1: Sexual Reproduction in Animals Objective In this lesson, you should be able to: explain sexual reproduction in animals. Some animals are capable of undergoing sexual reproduction, while some can undergo asexual reproduction. There are also some animals that can undergo both. Sexual reproduction involves two parents, the male and the female, that produce reproductive cells called gametes. Asexual reproduction, on the other hand, utilize many means other than the use of gametes. What is sexual reproduction? Warm-Up Modeling the Kinds of Birth Materials: 3 small plastic animal toys, clay 2 plastic bottles Procedure: Conception: create three separate models for each item below. 1. Egg-laying animals: Coat the plastic animal in clay to represent the animal developing inside an egg. 2. Live-bearing animals: Place the second plastic animal inside the plastic bottle, which represents the uterus. Paint the bottle red. Remove the floor of the bottle. 3. Hatching inside the body: Coat the third plastic animal in clay and place it inside the plastic bottle, which again represents the uterus. Remove the floor of the bottle. 5 Birth: follow the succeeding steps, for birth based on the previous setup for conception. 1. Egg-laying animals: The clay will be broken apart, which represents the cracking of the egg, to hatch the animal. 2. Live-bearing animals: The plastic animal will be taken out through a hole on the floor of the bottle to represent birth. 3. Hatching inside the body: The clay will be broken apart to hatch the animal and taken out through the floor of the bottle. Guide Questions: 1. What are the differences between the three methods above? 2. Why do you think some animals lay eggs and others do not? Learn about It Gametes Gametes are the sex cells produced by the organism. Animals have organs known as gonads, and these gonads are the parts of the reproductive system that produce the gametes. Male and female organisms produce different kinds of gametes, and these are the cells that fuse together in the process of fertilization in order to produce a zygote. This zygote is what will eventually become the new organism. Male Gametes Male gametes are known as sperm cells. These gametes are produced by the gonads of male animals, which are the testes. Each sperm cell has a head, a midpiece, and a tail. The head of the sperm has a large nucleus that carries the haploid set of chromosomes. It has a sac called acrosome that contains enzymes for breaking the egg membranes to fertilize the egg cells. The midpiece is rich in mitochondria to provide energy for the sperm to swim to the egg. This is necessary as sperm cells need enough energy to be able to survive the journey inside the female reproductive system. The tail of the sperm is mostly made up of the flagellum. It has a beating 6 movement that enables the sperm cell to be motile in order to reach the female gamete during fertilization. It usually only takes one sperm cell to fertilize a female gamete, but in many animals, it takes a collective effort by multiple sperm cells to penetrate the protective wall of the gamete. Fig. 1. Sperm cell Female Gametes Female gametes are known as egg cells or oocytes and are produced by the ovaries, the female gonads. The egg cells are usually some of the largest cells found in animals. This is owed to the fact that the egg cells take nutrients and cytoplasmic material from structures known as polar bodies. These polar bodies form with the oocytes and serve to nourish the developing gametes. The egg cells mature inside structures known as follicles, which are found in the cortex of the ovary. The follicles are fluid-filled and have parts that are necessary for protecting the egg cells and allowing them to develop and mature. Each follicle contains one egg cell. The egg cell is surrounded by two surfaces: the cell surface membrane, which is surrounded by an outer membrane. Sperm cells need to penetrate these membranes for fertilization to take place. Follicles contain different structures, and some of these include the cumulus oophorus, granulosa cells, theca, zona pellucida, corona radiata, and antrum. The cumulus oophorus aids in the development and nourishment of the 7 developing egg cell. It plays a major role in helping the egg reach maturity. The granulosa cells help in the production of hormones. The theca, on the other hand, performs many functions which include producing hormones and providing nourishment and support to the developing egg cell. Fig. 2. Mature Follicle The zona pellucida protects the egg cell and plays a role in the interaction between egg and sperm during fertilization. The corona radiata, on the other hand, is used for the nourishment of the egg cell and is the outermost layer of protection. The antrum of the follicle contains fluids that surround the egg. Gamete Chromosomes The gametes form as a product of gametogenesis, which involves the production and maturation of the sex cells. This will be discussed in more detail in Lesson 4. As a result of gametogenesis, all gametes end up having a haploid chromosome number (n). During fertilization, the sperm cell (n) fuses with the egg cell (n) forming a zygote with 2n chromosomes. With fertilization restoring the number of chromosomes (diploid number, 2n), 8 the number of chromosomes for a species remains the same from one generation to the next. Fertilization: Sperm Penetration and Fusion Fertilization is the process wherein the sperm cell penetrates the protective layers of the egg cell in order to fuse their genetic materials and produce a zygote. This may seem like a simple process, but there are actually a number of steps involved. Sperm cells utilize their motility to reach the egg cell. However, many individual cells will not survive the journey. Those that do, however, will work to penetrate the layers of the egg cell. The granulosa cells which serve to protect and nourish the egg will be penetrated by the sperm, in between their spaces. What follows is the enzymatic degradation of the zona pellucida under the granulosa. Recall that sperm cells have a number of enzymes contained within their acrosomes which serve to aid in egg cell penetration. This is the reason why it takes multiple sperms to break down the layer, but it only takes one sperm to fertilize. Once a sperm cell has entered the zona pellucida, the plasma membranes of the sperm and egg cells will fuse, and the nucleus containing the genetic material will also start to fuse with the egg. Fig. 4. Sperm penetration and fusion 9 What follows is a series of steps that will prevent polyspermy or the fertilization of an egg cell by multiple sperms. Some of these steps include the hardening of the zona pellucida, the loss of sperm receptors, and the “puffing up” of the corona radiata. Types of Fertilization in Animals Fertilization can occur either inside the body of the female organism or outside. These are referred to as internal or external fertilization. External Fertilization If fertilization happens outside the body of the animal, then it is known as external fertilization. External fertilization then happens in the outside environment. External fertilization is common to animals inhabiting aquatic or moist environments. The male and female animals will both release sperm cells and egg cells outside the body, and certain chemicals and signals allow the sperm and egg to recognize each other and meet. Fertilization then occurs. In some cases, animals need to stimulate each other into releasing the gametes. One such example of this stimulation is the amplexus of frogs, wherein the male frog rides on the back of the female as both deposit eggs and sperm into the outside environment. External fertilization results in more zygotes with lesser protection and parental care. However, since the zygote develops outside the female reproductive tract, it is adapted to survive heat stress and water loss. 10 Internal Fertilization Internal fertilization happens when the male’s sperm cells are directly deposited into the body of the female animal. In internal fertilization, the zygote develops inside the female reproductive tract. It results in less number of zygotes but with greater protection and parental care of the young. Examples of notable organisms that undergo internal fertilization are mammals and birds. mammal bird Fig. 7. Mammals and birds undergo internal fertilization. Eggs fertilized internally exhibit different types of development. They may be classified based on where the organisms develop after being fertilized. Organisms that lay and hatch their eggs outside their body are called oviparous. The eggs laid by oviparous organisms contain a substance known as the yolk. Since the eggs are physically separated from the mother, it is the yolk that provides nourishment to the developing embryo as it grows. Examples of oviparous organisms are birds. When eggs are hatched and retained within the uterus, the organisms are called ovoviviparous. Ovoviviparous embryos do not have an internal connection to the mother’s placenta. Their nourishment will primarily come from yolk within the mother’s body. Examples of ovoviviparous organisms are sharks. 11 Finally, organisms that complete their development in the uterus and are born alive are called viviparous. Viviparous organisms directly nourish the developing embryos within the body. There are species of organisms, however, that also rely on yolk while being viviparous. Examples of viviparous organisms are all placental mammals. Table 1. Difference between oviparous, viviparous, ovoviviparous Location of Source of Parity embryonic Examples nourishment development Most reptiles, all External birds, monotremes, Oviparous Yolk environment but some amphibians, inside the egg some fishes Some fishes, Inside the Viviparous Mother mammals except mother’s womb monotremes Some insects, some bony and Inside the Ovoviviparous Yolk cartilaginous mother’s womb fishes, and many reptiles mammal bird fish Fig. 8. Most mammals are viviparous, birds are oviparous, and fishes are ovoviviparous. 12  Key Points Sexual reproduction involves two parents, the male and the female, that produce reproductive cells called gametes. Male gametes are known as sperm cells. These gametes are produced by the gonads of male animals, which are the testes. Female gametes are known as egg cells or oocytes and are produced by the ovaries, the female gonads. Fertilization can occur either inside the body of the female organism or outside. These are referred to as internal or external fertilization. Eggs fertilized internally exhibit different types of development. They may be classified based on where the organisms develop after being fertilized. Web Links For further information, you can check the following web links: How did animal genitalia evolve? Ted-Ed. 2017. ‘The evolution of animal genitalia - Menno Schilthuizen.’ https://www.youtube.com/watch?v=vcPJkz-D5II Some organisms have unusual ways of reproducing. Watch: National Geographic. 2008. ‘Frog Love Foam | National Geographic.’ https://www.youtube.com/watch?v=1D8b4e9nGwE Check Your Understanding A. Identify the terms being described by the statements below. 1. These are the sex cells produced by the organism. 2. These are the male sex cells. 3. These are the organs that produce sex cells. 13  4.These are the female organs that produce sex cells. 5.This is the fusion of the male and female sex cells. 6.This is the tail of the male sex cell. 7.This refers to the union of the male and female sex cell outside the female’s body. 8. This refers to the union of the male and female sex cells inside the female’s body. 9. This refers to the stimulation of the frogs to release sex cells. 10. These are organisms that lay eggs that hatch outside the body. B. Write true if the statement is accurate, and false otherwise. 1. Ovoviviparous organisms only undergo external fertilization. 2. Viviparous organisms give birth to live young. 3. The zygote is produced by the male organism. 4. All types of reproduction require sex cells. 5. Most frogs undergo internal fertilization. Challenge Yourself Answer the following questions. 1. How do ovoviviparous organisms give birth? 2. Is sexual reproduction possible without gametes? Why or why not? 3. What is the sperm’s flagellum for? 4. Why do frogs need to undergo amplexus? 5. How does a zygote form? 14  Lesson 13.2: The Female Reproductive System Objective In this lesson, you should be able to: describe the female reproductive system. The reproductive system of humans is specific to males and females. The female reproductive system has its own set of organs that perform their own functions. What are the functions of the organs of the female reproductive system? Warm-Up Female Reproductive System Puzzle Materials: printouts of the puzzle Procedure: 1. Secure copies of the printouts of the female reproductive system below: Female Reproductive System Exercise https://drive.google.com/file/d/1Qai1S0varRcAEIrKn1Ee9X7aj2xLo3wT/view? usp=sharing 2. Cut out the printouts and arrange the organs by attaching them to where they are supposed to be connected. Your end product should form the female reproductive system. 3. With your group, trace the path of an egg cell from the ovary. 4. Brainstorm the functions of these organs with your group. Guide Questions: 1. Which is the central piece of the puzzle? 2. What do you think all these organs are for? 15  Learn about It Functions of the Human Reproductive System The human female reproductive system has several functions, some of which are for egg cell production, fertilization, and development of the zygote into a new organism. Egg Cell Production The female reproductive system is responsible for the nourishment and development of the female gametes. Gametogenesis, which involves the production, nourishment, and development of gametes occurs here. The type of gametogenesis in female organisms is known as oogenesis. The egg cells are stored in the ovaries until they are released in a process known as ovulation. Fertilization In humans, all fertilization is done internally. The female reproductive system is responsible for maintaining the necessary conditions for fertilization to occur. After the egg is fertilized, the female reproductive system prepares the body for pregnancy. Hormone Production There are cells in the organs of the female reproductive system that serve to produce hormones to be delivered to the different parts of the body. These hormones have many functions which include signaling the body to prepare for puberty or triggering the changes that happen in preparation for pregnancy. Pregnancy The organs of the female reproductive system work together in order to allow the body to accommodate pregnancy. Many changes happen to a woman’s body during this time, and many of these changes are triggered by the female reproductive system’s release of signals. The Internal Reproductive System of Females The female reproductive system is comprised of organs that can be found internally or externally. These organs are classified into the internal reproductive system and the external reproductive system. The internal reproductive system is composed of the vagina, uterus, fallopian tubes, and ovaries. 16  Fig. 9. Organs of the female reproductive system Vagina The vagina is an elastic, muscular canal that connects the external reproductive system to the cervix. It is made up of connective, fibrous, and epithelial tissues. The primary function of the vagina is to receive the penis and sperm during sexual intercourse and to pass blood during menstruation. It is also the passageway of the baby during delivery. Hence, it is also called the birth canal. The pH of the vagina is acidic. This is to protect the vagina from pathogens like bacteria or fungi. The reason for the vagina’s 17 acidity is due to the pH alteration by certain bacteria, like Lactobacillus acidophilus, which is somewhat mutualistic with humans. Cervix At the lower portion of the uterus is the cervix, a muscle that holds the fetus during pregnancy. The cervix expands once the baby is ready to be born. The cervix also contains cervical mucus, which facilitates the transport and nourishment of sperm to aid in fertilization, and also plays a role in hormonal signaling. It can also be used as an indicator of a woman’s fertility. This is shown in figure 11 below. Fig. 11. Cervical mucus chart Uterus The uterus is a hollow muscular organ that lies between the urinary bladder and the rectum. It has a very soft lining that holds the fertilized egg and nurtures it until it becomes a fetus. Fig. 12. Uterine wall layers 18 The lining of the uterus thickens and sheds during the different parts of the menstrual cycle of females. It is the lining of the uterus that is shed off and removed from the body during menstruation. The uterine wall has three distinct layers: the perimetrium, the myometrium, and the endometrium. These three layers have their own functions and characteristics. The perimetrium is the outermost layer of the uterus, and it provides support to the entire organ. The myometrium is the middle layer, and the thickest one. It contains smooth muscles, and responsible for uterine contractions. The endometrium is the innermost layer. It maintains the structural integrity of the uterus and is the part that usually sheds off during the secretory phase of the menstrual cycle. Fallopian Tubes The fallopian tubes connect the ovaries to the uterus. These are narrow 10 centimeter-long tubes from which the eggs travel from the ovaries to the uterus during the process of ovulation. Their primary function is to transport the egg cell properly to the uterus. The fallopian tubes contain ciliated and non-ciliated columnar cells. The ciliated cells of the fallopian tube propel the egg cells to the uterus during ovulation. The non-ciliated cells, on the other hand, produce secretions in order to aid the ciliated cells with propulsion. The wave-like motions seen in the digestive system known as peristalsis can also be witnessed in the fallopian tube, and this motion also aids the movement of the egg cell during ovulation. Ovaries The ovary is the female gonad that contains the egg cells. It produces female sex hormones, estrogen, and progesterone. At birth, a female baby has around 70 000 immature egg cells in each ovary. The eggs mature and are released during puberty. The hormones estrogen and progesterone control the menstrual cycle and maintain the secondary sexual characteristics of females. These hormones are also responsible for some of the changes that happen during pregnancy. Estrogen is the primary female hormone. The External Reproductive System All the structures of the female reproductive system outside of the vagina are 19 considered to be structures of the external reproductive system. The main female external reproductive parts include the labia majora, labia minora, and clitoris. The mons pubis, also known as the mons, is a layer of fat that covers part of the pubic bones. This structure contains glands that are capable of secreting pheromones. Fig. 13. External parts of the female reproductive system Labia Majora The labia majora encloses and protects all the external reproductive organs. It contains sweat glands and oil-secreting glands. One of the structures covered by the labia majora is the vaginal orifice, which is the outer opening of the vagina. This structure contains the hymen, which is a thin layer of membrane that serves to protect the vagina. Labia Minora The labia minora surrounds the openings of the vagina and urethra. The labia minora serves to protect the vaginal and urethral openings. The urethral orifice is found in between the clitoris and the vagina and serves as the opening for the urethra which is a part of the excretory system as the exit point for urine. Clitoris The clitoris is a small, sensitive protrusion at which the two labia minora meet. The 20 clitoris itself, however, does not have any significant reproductive function. Key Points The human female reproductive system has several functions, some of which are for egg cell production, fertilization, and development of the zygote into a new organism. The type of gametogenesis in female organisms is known as oogenesis. The egg cells are stored in the ovaries until they are released in a process known as ovulation. The female reproductive system is comprised of organs that can be found internally or externally. The internal reproductive system is composed of the vagina, uterus, fallopian tubes, and ovaries. All structures outside the vagina are part of the external reproductive system. Web Links For further information, you can check the following web links: To learn more about ovulation, click this link to watch a video about ovulation. Ted-Ed. 2016. ‘How menstruation works - Emma Bryce’ https://www.youtube.com/watch?v=ayzN5f3qN8g 21  For more information about the menstrual cycle, watch: Ted-Ed. 2015. ‘Why do women have periods?’ https://www.youtube.com/watch?v=cjbgZwgdY7Q Check Your Understanding A. Identify the terms being described by the statements below. 1. This refers to the formation and development of gametes. 2. This refers to the formation and development of gametes in females. 3. This connects the female external reproductive system to the cervix. 4. This connects the ovaries to the uterus. 5. This is the protrusion where the two labia meet. 6. This is the muscle that holds the fetus during pregnancy. 7. This refers to the process of releasing egg cells. 8. This is the primary female hormone. 9. This surrounds the openings of the vagina and urethra. 10. This encloses all external reproductive organs of the female. B. Write true if the statement is accurate, and false otherwise. 1. Estrogen and progesterone aid in pregnancy. 2. The clitoris has a significant reproductive function. 3. The ovary contains the egg cells. 4. Oogenesis happens in the ovaries. 5. The fallopian tubes contain urine. Challenge Yourself Answer the following questions. 1. What is the significance of the function of the labia minora? 2. What are the functions of estrogen? 3. What is the menstrual cycle? 4. How is the cervix an indicator of childbirth? 5. What is the pathway of the egg cell during ovulation? 22  Lesson 13.3: The Male Reproductive System Objective In this lesson, you should be able to: describe the male reproductive system. The male reproductive organs have a different function from that of a female. As such, the organs themselves are also different in terms of structure and appearance. What are the functions and components of the male reproductive system? Warm-Up Male Reproductive System Puzzle Materials: printouts of the puzzle Procedure: 1. Secure copies of the printouts of the male reproductive system below: Male Reproductive System Exercise https://drive.google.com/file/d/1Qg73judrvLkvOLJ4hiQjFMX-5cstMVVE/view ?usp=sharing 2. Cut out the printouts and arrange the organs by attaching them to where they are supposed to be connected. Your end product should form the male reproductive system. 3. With your group, trace the path of a sperm cell from the testis. 4. Brainstorm the functions of these organs with your group. 23 Guide Questions: 1. Where do you think does the sperm originate from? 2. What do you think are all these organs for? Learn about It Functions of the Male Reproductive System The male reproductive system is specialized for the production of sperm cells and their deposition into the female reproductive tract. It has a series of structures that serve to perform these functions efficiently. Sperm Cell Production The production, development, and maturation of sperm cells happens within the male reproductive system. Recall that this process is known as gametogenesis, and the type of gametogenesis that occurs in male organisms is known as spermatogenesis. Production of Hormones The primary sex hormone of male animals is known as testosterone, and it is produced by the testes. Testosterone is responsible for the changes that occur during puberty, as well as the signaling that is necessary in order to trigger spermatogenesis. Deposition of Sperm into the Female Another function of the male reproductive system of humans is to safely and properly deposit the sperm cells into the female reproductive tract. The male reproductive system has a number of secretions to ensure that the sperm cells are properly nourished and protected for it to be safely deposited into the female reproductive tract. An organ known as the penis does the deposition. Any organ that is used for depositing sperm into a female is known as an intromittent organ. This is the penis in humans. The Components of the Male Reproductive System The male reproductive system has organs that serve to fulfill the functions that were mentioned above. It is composed of the testes, scrotum, prostate gland, urethra, penis, and sperm ducts. 24  Fig. 14. Organs of the male reproductive system The Testes Recall that the gonads of the male reproductive system are the testes. Each male reproductive system has two testes. Their function is to produce male sex cells called sperm cells. They are also responsible for producing male sex hormones such as testosterone. The sperm cells develop inside the testes in a series of tubes known as the seminiferous tubules. The seminiferous tubules are structures that are coiled inside the testes, and this is where sperm is produced and where they mature. 25 Immature sperm cells are usually found near the border of the seminiferous tubule. As these cells mature, they move further and further inside the tubule, closer to the lumen, which refers to the space in the middle of a tube. Fully mature sperm, those that are motile and developed flagella, are found within the lumen itself. There are other cells like the Sertoli cells, Leydig cells, and myoid cells. The Sertoli cells release a variety of hormones that aid in the development of sperm, and the Leydig cells primarily release testosterone. The myoid cells, on the other hand, are for the contraction of the seminiferous tubules for moving cells and substances. There are also blood vessels in the testes, for the delivery of oxygen and nutrients. The Scrotum The scrotum is a bag of skin that contains the testes. It is a reproductive structure that is located under the penis. The scrotum is about 2–3°C lower than the normal body temperature, and this is the temperature that is favorable for sperm cell production and development. Within the scrotum are muscles known as the dartos and cremaster muscles. These play important roles in maintaining the temperature of the scrotum. When the environmental temperature is too low, the dartos contracts, which decreases the surface area of the scrotum in contact with the outside environment. This prevents further heat loss. The cremaster, on the other hand, brings the testes closer to the body to conserve heat. Epididymis Mature sperms are later on stored in a tube beside the testes known as the epididymis. The sperm cells are stored until they are released from the body through a process known as ejaculation. Ejaculation forcefully expels sperm and semen from the male body into the female’s vagina during sexual intercourse. This forceful expulsion of fluids is made possible by muscles like the pubococcygeus and the bulbospongiosus muscles. 26 Once the sperm cells are within the female reproductive tract, they can survive for as long as five days. This increases the chances of successfully fertilizing an egg. However, if the sperm remains within the male reproductive system for too long, they become phagocytosed and is reabsorbed back by the system. This is to ensure that the sperm that can potentially fertilize an egg are not of an advanced age. The epididymis contains proteins known as defensins. There are many kinds of defensins, all of which are found in the different areas of the body and performing different functions. The defensins in the epididymis serve to support the reproductive tract of males, protect against bacterial infections, and regulate recovery after a bacterial infection. Vas Deferens During ejaculation, sperm moves from the epididymis, into a tube called the vas deferens, and into another tube known as the urethra, and out of the body. The process of vasectomy is a method of birth control that deals with cutting or blocking the tube of the vas deferens. This prevents sperm cells from being transported out of the body and results to future sexual intercourse by the affected male to carry no risk of fertilization. Prostate Gland The prostate gland secretes the prostate fluid, which neutralizes the acidic conditions of the vagina. The mixture of sperm and prostate fluid is called semen. The muscles of the prostate gland help propel semen through the urethra and into the female reproductive organ during ejaculation. Urethra The urethra is the tube that transports and discharges urine and semen outside the body. It is connected to both the urinary bladder and sperm duct. This is the reason why the urethra serves as an exit point for both urinary and reproductive products. Penis 27 The penis is the external part of the male reproductive system. It is a tube-shaped organ that contains the urethra, which allows it to pass the urine and semen out of the body. The glans penis, also known as the head of the penis, is a sensitive structure at the end of the organ. It contains the opening for the urethra. The glans penis is covered by an excess skin known as the prepuce, which protects the glans. Within the penis is a structure known as the corpus cavernosum (plural: corpora cavernosa). This structure is known as the erectile tissue in men, which leads to the penis becoming erect when the corpora cavernosa is filled with blood. This is in preparation for sexual intercourse. Many cultures practice a medical process known as circumcision. This process involves the partial or complete removal of the prepuce in order to expose the glans penis. Studies show that circumcision has many medical benefits which include decreased risk of some diseases and infections. Sperm Ducts Sperm ducts are composed of the vas deferens and seminal vesicles. Recall that the vas deferens is a tube through which sperm cells pass before entering the urethra. On the other hand, seminal vesicles secrete a fluid that makes the sperm cells more mobile, increasing the chances of fertilization. The spermatic cord is a structure associated with the vas deferens. Its primary function is to hold and support structures like blood vessels and the vas deferens itself. The Accessory Glands The male reproductive system also has a series of organs known as the accessory glands. These glands secrete substances that aid in the nourishment of sperm and 28 contribute to higher chances of fertilization. The seminal vesicles are also considered to be accessory glands. Other accessory glands include the bulbourethral gland and the prostate. The bulbourethral gland has secretions that serve to neutralize the vagina’s acidity, while the prostate gland releases substances to increase the motility of the sperm cells. Key Points The male reproductive system is specialized for the production of sperm cells and their deposition into the female reproductive tract. The production, development, and maturation of sperm cells happens within the male reproductive system. The type of gametogenesis that occurs in male organisms is known as spermatogenesis. The male reproductive system is composed of the testes, scrotum, urethra, penis, sperm ducts, and accessory glands. The gonads of the male reproductive system are the testes. Each male reproductive system has two testes. Web Links For further information, you can check the following web links: To see the comparison between the sperm cells of different animals, watch: Ted-Ed. 2013. ‘Human sperm vs. the sperm whale - Aatish Bhatia’ https://www.youtube.com/watch?v=U9g4gRWkFTs 29  To learn more about the journey of the sperm, watch: Seeker. 2014. ‘The Sperm Struggle is Real’ https://www.youtube.com/watch?v=icTWNDK825Y Check Your Understanding A. Identify the terms being described by the statements below. 1. These are the male gametes. 2. This refers to the formation and development of gametes in males. 3. This holds the gonads of the male. 4. This is where the sex cells of the male develop in the gonad. 5. This is where mature sex cells are stored. 6. This is the release of male sex cells from the body. 7. This is the exit tube of the sex cells from the male body. 8. This gland secretes prostate fluid. 9. This is the tube-shaped external organ of the male reproductive system. 10. This secretes the fluid that makes sperm more mobile. B. Write true if the statement is accurate, and false otherwise. 1. Males have a significant amount of estrogen. 2. The exit point for urine and sperm are different. 3. The sperm ducts include the seminal vesicles and the vas deferens. 4. Prostate fluid neutralizes vaginal acidity. 5. The scrotum is an internal organ. Challenge Yourself Answer the following questions. 1. What is the fluid with the sperm for? 2. How does the sperm travel from the testes and out of the body? 3. What are the effects of testosterone in males? 4. Why is there a need for sperm to be motile? 5. What is spermatogenesis for? 30  Lesson 13.4: Spermatogenesis and Oogenesis Objectives In this lesson, you should be able to: define the roles of testes and ovaries; and explain the process of gametogenesis. The development of gametes in the gonads of both males and females makes reproduction possible. Without gametogenesis, fertilization will not be possible. How does gametogenesis occur? Warm-Up Modeling Gametogenesis Materials: clay toothpicks, colored red and blue yarn Procedure: Spermatogenesis: 1. Primary spermatocyte: Make a model of a cell on an illustration board and attach two blue and two red toothpicks to the model. Shape these into an “X” shape, with each X having the same color. These toothpicks represent the chromosomes. 2. Secondary spermatocyte: In this step, create two cells for this model on an illustration board, split the toothpicks to get two in each cell. Each will receive one red and one blue toothpick. This represents the distribution of chromosomes. 3. Spermatid: Split each secondary spermatocyte into two (in another new 31  model) and give each one toothpick. 4. Adult sperm: Attach a piece of yarn to the model cells. Oogenesis: 1. Primary oocyte: Make a model of a cell on an illustration board and attach two blue and two red toothpicks to the model. Shape these into an “X” shape, with each X having the same color. These toothpicks represent the chromosomes. 2. Secondary oocyte: In this step, create two cells for this model on an illustration board and make the model for one significantly smaller than the other. Place two of the toothpicks on the larger cell. It should receive one red and one blue toothpick. This represents the distribution of chromosomes. 3. Development: Split each cell into two models, but make one model from the larger cell bigger in size than the other. You should have three smaller cells and one larger cell. Place a toothpick in the larger cell. Guide Questions: 1. What do you think does the larger ball in oogenesis represent? 2. What does the yarn in the sperm represent? Learn about It In animals, the reproductive organs called gonads produce the gametes. The male gonads are the testes, and the female gonads are the ovaries. Each of these gonads further has structures that serve to produce and nourish the developing gametes. Gametes all have a haploid set of chromosomes. This means that they only have one set of chromosomes which is unpaired. This is in contrast with a cell having a diploid set, as is the case of somatic cells. Diploid cells have a complete set of paired chromosomes. Spermatogenesis The seminiferous tubules produce sperm cells, and this is where the maturation of these cells occurs. Sperm cells are considered mature if they are motile and possessing haploid set of chromosomes. The production of mature sperm cells is called spermatogenesis. The entire process of spermatogenesis takes about 65–75 days in mature human males. 32  Fig. 19. Events of spermatogenesis Spermatogonia During spermatogenesis, progenitor cells called spermatogonia are produced. Some spermatogonia undergo mitosis to renew themselves while others divide and commit to become primary spermatocytes. 33 Primary Spermatocytes The primary spermatocytes will then undergo meiosis I. This is when the number of chromosomes is reduced from a diploid number to a haploid number. The haploid number will be maintained until the sperm matures. Secondary Spermatocytes Through meiosis I, each primary spermatocyte divides into two secondary spermatocytes. Spermatids Meiosis II will allow each secondary spermatocyte divides into two spermatids or young spermatozoa. Young spermatozoa will eventually develop into mature spermatozoa, also known as sperm cells. Oogenesis The production of mature egg cells is called oogenesis. The female gonads, the ovaries, are the primary organs involved with oogenesis. The ovary has two major layers, which are the cortex and the medulla. The cortex is the outer layer, whereas the medulla is the inner. Oogenesis occurs in the cortex, and the developing egg cells are contained inside structures known as follicles. The follicles serve to protect and nourish the egg cells as they develop. The medulla contains blood vessels and nerves. Primordial Follicle A human female, when born, already has a fixed number of primordial follicles. This means that the number of times wherein a person can ovulate over the course of a lifetime is already dictated by the number of primordial follicles present. This is also the reason why menopause happens. Menopause occurs when a female is already incapable of ovulating as a result of having no more viable egg cells. These primordial cells will eventually mature as the female enters puberty. Oogonia Oogenesis begins with a germ cell called oogonium. These oogonia undergo mitosis, from which the primary oocytes are derived. 34 Primary Oocytes The diploid oogonium undergoes mitosis to produce two diploid primary oocytes. This process usually happens before birth, or shortly after birth. The primary oocytes will remain as primary oocytes because they are arrested at prophase of meiosis I until puberty when oogenesis continues. Further maturation of these oocytes will start to happen during puberty and beyond. Fig. 20. Meiotic events and oogenesis Secondary Oocytes The primary oocyte is arrested at prophase of meiosis II. The maturation will continue when a woman ovulates as part of her menstrual cycle. The primary oocyte will continue the process of meiosis to produce a haploid secondary oocyte 35 and a polar body. The polar body usually dies. At ovulation, the secondary oocyte is released. It travels toward the uterus through the oviduct. If the secondary oocyte is fertilized, the cell completes the process of meiosis, producing a second polar body and a fertilized egg. Egg Cell From the 70 000 immature egg cells present at birth in each ovary, only around 500 will become mature. These are released when the females reach physical maturity. The egg cell has a large nucleus with a haploid set of chromosomes. It has a small amount of yolk with an abundance of the cytoplasm. Key Points In animals, the reproductive organs called gonads produce the gametes. The male gonads are the testes, and the female gonads are the ovaries. The ovary has two major layers, which are the cortex and the medulla. The cortex is the outer layer, whereas the medulla is the inner. Oogenesis occurs in the cortex. Developing egg cells are contained inside structures known as follicles. The follicles serve to protect and nourish the egg cells as they develop. The medulla contains blood vessels and nerves. Oogenesis produces many cells called oogonia. These oogonia undergo mitosis, from which the primary oocytes are derived. Oogenesis begins with a germ cell called oogonium. The diploid oogonium undergoes mitosis to produce two diploid primary oocytes. The primary oocyte will continue the process of meiosis to produce a haploid secondary oocyte and a polar body. The polar body usually dies. From the 70 000 immature egg cells present at birth in each ovary, only around 500 will become mature. 36  Web Links For further information, you can check the following web links: How do people become male or female? Watch: Ted-Ed. 2012. ‘Sex Determination: More Complicated Than You Thought’ https://www.youtube.com/watch?v=kMWxuF9YW38 To see the journey from fertilization to development of the organism, watch: Nova PBS. 2015. ‘Greatest Miracle PBS’ https://www.youtube.com/watch?v=vA0xZ3K_0q8 Check Your Understanding A. Identify the terms being described by the statements below. 1. This is the layer of the ovary that contains the egg cells. 2. This is the layer of the ovary that contains mostly blood vessels and nerves. 3. This process of oogenesis produces primary oocytes. 4. This process of spermatogenesis produces primary spermatocytes. 5. This is the chromosome count of the oogonia and spermatogonia. 6. This is the chromosome count of the mature sperm and eggs. 7. This process results in the reduction of chromosome count for the developing gametes. 8. This part of the sperm contains enzymes for breaking the egg’s membrane. 9. This is the mitochondria-rich part of sperm. 10. This structure in the ovary’s outer layer contains the developing egg cell. B. Write true if the statement is accurate, and false otherwise. 1. Hormones are important in gametogenesis. 2. The number of chromosomes doubles after mitosis. 3. The cumulus oophorus nourishes the developing egg cell. 4. The theca plays no role in gametogenesis. 5. The medulla contains blood vessels. 37  Challenge Yourself Answer the following questions. 1. Why is it necessary to reduce the number of chromosomes in the gametes? 2. What is the function of the ovarian follicle? 3. Why does the chromosome number go back to diploid after fertilization? 4. Why are polar bodies formed? 5. Can humans reproduce without gametogenesis? Justify. 38  Laboratory Activity Activity 1.1 Animal Reproductive Systems Objectives At the end of this laboratory activity, the students should be able to: locate the male and female gonads of different animals; differentiate the appearance and function of the gonads; and practice proper dissection skills. Materials and Equipment male and female frog/toad tilapia crab dissecting pan and set Procedure Frog dissection: 1. Set the frog down on a dissecting pan with the back of the frog on the wax. 2. Pin the arms and legs to the wax. 3. Make an incision onto the skin as follows: 39  4. Cut the muscle of the abdomen vertically until the chest area. 5. For the male frog, check the back body wall and try to locate two yellowish oval organs. These are the testes. 6. For the female frog, you will sometimes find black grains inside the abdomen. These are eggs. Check the sides of the frog inside the abdomen to locate the oviducts, which are long, thin, coiled tubes. Tilapia dissection: 1. Set the tilapia down on the dissecting pan. 2. Make an incision onto the skin and muscles as follows: 3. Check the lower part of the fish abdomen to locate paired yellow or pink organs. These are the fish gonads. Crab dissection. 1. Set the crab down on the dissecting pan, with the rounded part of the shell touching the wax. 2. Check the crab’s underside. There is a structure known as the apron. See the photo below. 40 3. If the apron is pointed, the crab is a male. If the apron is round, the crab is a female. 4. Flip the crab to expose the back. Remove the shell as follows: 5. The ovaries of the female and testes of the male are located as follows: Dissected female crab with ovary. Dissected ovary (A) anterior horn, (B) commissure, (A) anterior horn, (B) commissure, (C) heart, (D) posterior horn. (C) posterior horn. (D) spermatheca 41  Dissected male crab with gonad Male reproductive system (A) testis, (B) commissure, (A) testis, (B) commissure, (C) (C) anterior vas deferens, anterior vas deferens, (D) median (D) heart vas deferens, (E) posterior vas deferens, (F) ejaculatory duct Waste Disposal Place all dead animals in a black garbage bag for disposal. Wash all dissecting equipment. Table 1. Observations on the gonads. Animal Male gonad appearance Female gonad appearance Frog/Toad Crab Fish Guide Questions 1. What are the differences between the testes and ovaries in terms of appearance? 2. Are there other distinguishable traits between the males and females? 42  Performance Task Proper Care for the Reproductive System Goal Your goal is to show how proper hygiene and care should be done for the benefit of the reproductive system. Role You are young health professionals who wish to raise awareness on how to properly care for the reproductive system. Audience Your audience includes the members of your school community. Situation We should constantly practice proper ways to take care of the reproductive system. These practices should be part of our daily lives. Product, Performance, and Purpose You should create a skit or TV commercial showing the effects of good and bad reproductive health care. Your skit or commercial can be done live or presented as a video. Your skit should show the effects of proper and improper diet; proper and improper hygiene; and good and bad exercise habits. Standards and Criteria Your performance will be graded by the following rubric. Below Needs Successful Exemplary Criteria Expectations, Improvement Performance Performance 0% to 49% 50% to 74% 75% to 99% 100% Content. Details are not Details are Details are Details are presented. presented but not presented in an presented in an Detailed facts are Content is not organized. There is organized manner. organized matter presented well. related to the task. some content that Content is related that can be easily Content related to the is not related to to the task. understood. task. the task. Content is related 43  to the task. Additional supporting details are presented. Communication The presentation The presentation The presentation The presentation was not done. was done but in a was done was done clearly. Skills. disorganized and smoothly but the Concepts were The presentation was illogical manner. concepts are presented in a done in a clear and presented in such logical manner logical manner. a way that should and easily be rearranged for understandable by better the audience. understanding. Audiovisual No audiovisual Audiovisual Audiovisual Audiovisual materials used. materials are used materials are well materials are well materials. but are messy and organized and organized and Materials presented disorganized. done neatly. Some done creatively. in a creative way but There is no attention is paid to There is also great not sacrificing the attention to detail. attention to accuracy of facts. details. details. Integrating No concept of The concept of The concept of The concept of reproductive care reproductive care reproductive care reproductive care concepts in discussed in the was mentioned was properly was integrated in reproductive task. but not integrated integrated into the an organized and care. into the task. task. Concepts logical way. The subject matter is were properly Additional integrated and presented in concepts about relation to the reproductive care properly used in task. related to the task presenting facts. were presented. Self Check Check I can… explain the parts and functions of the reproductive system. differentiate between the male and female reproductive systems. differentiate and explain the processes of gametogenesis. 44  Key Words Amplexus A process wherein the male frog rides on the back of the female as both deposit eggs and sperm into the outside environment Circumcision This process involves the partial or complete removal of the prepuce in order to expose the glans penis. Egg Cell Female gametes are known as egg cells. Fertilization The process wherein the sperm cell penetrates the protective layers of the egg cell in order to fuse their genetic materials and produce a zygote. Flagellum The flagella are used for swimming and motility in order for the sperm cell to reach the female gamete during fertilization. Gametes Gametes are the sex cells produced by the organism. Gametogenesis Gametogenesis is a biological process by which haploid gametes are formed by the meiotic division of diploid sex cells. Gonads Gonads are the parts of the reproductive system that produce the gametes. Oogenesis Oogenesis is the type of gametogenesis in females. Ovaries Ovaries are the gonads of the female reproductive system. Sperm Cells Sperm cells as gametes produced by the gonads of male animals Spermatogenesis Spermatogenesis is the type of gametogenesis in males. Testis Testes are the male gonads. Testosterone The primary sex hormone of male animals. 45  Wrap Up Male and Female Reproductive System 46  Photo Credits Fig. 4. Frogspawn_closeup by Tarquin, is licensed under CC BY-SA 3.0 via Wikimedia Commons. References Linda J. Heffner and Danny J. Schust. 2010. The Reproductive System at a Glance (3rd edition), Singapore: Wiley-Blackwell. The Human Body: The Reproductive System. Britannica Educational Publishing, 2011. Kerri O’Donnell. 2001. The Reproductive System. New York: The Rosen Publishing Group, Inc. Concord-Carlisle High School. Reproductive System Grades 9-12, Lesson 2. http://www.concordcarlisle.org/jreed/wp-content/uploads/sites/37/2015/01/Reprod uctive-System-.pdf 47