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As you are aware, a family can continue to exist generation after generation. Organisms also produce their own kind. The earth’s diversity is maintained by the ability to reproduce one’s kind. Every living thing has a tendency to reproduce. It is just as important as other biological processes like respiration, circulation and nutrition. This lesson will teach you how new organisms grow, become viable, and then give birth to another generation. This lesson will also teach you the importance of good reproductive health and hygiene to stop the spread of sexually transmitted disease. You will be able to make the right decisions at the right time. OBJECTIVES Upon completion of this lesson, you will be able: * understand that reproduction is an essential feature of organisms for their continued existence.
State facts about reproduction in animals with a special emphasis on reproduction in humans; NOTES – * discuss the reproductive events that lead to pregnancy and parturition and raise concern about the negative consequences of adolescent pregnancies; * show awareness regarding the transmission of microbes You will be able to understand the transmission of HIV/AIDS and how to prevent it.Your parents must have told you how joyful it was to be born. You might have heard from your parents, family members or elder relatives how happy they were to witness you taking your first steps. As an infant, you remember being scared when a dog barks! Ask your parents about your childhood and infancy.
While your parents will likely recall many stories from the past, you as a teenager are busy learning about changes in yourself as you become an adult. Take note of the changes that occurred as you moved from infancy through childhood to adulthood. Make an album with all your photos from infancy through date. To get a better understanding of the changes that occur in the body as we grow up, you can collect photos of children growing up and infants. You will see that all organisms naturally grow up as you read this lesson. All organisms, including microbes and plants, must grow to the point where they can sustain their species. The species continues to exist from one generation of the next.
Reproduction is the biological process that perpetuates species. The biological process through which organisms give birth to their own species is called reproduction. There are two types of reproduction: — Asexual reproduction species: A group that includes animals, plants, and other living things. The Latin names of those who are able to mate with one another are used to identify them. Because they share the same genes, the members of the group appear similar and behave the same way. All human beings belong to the scientifically-named Homo sapiens. SCIENCE ANDTECHNOLOGY MODULE 5 Reproduction The Live World 118 Notes — Single individuals can produce bacterial or protozoan offspring.
This is called asexual reproduction. Figures 24.1 through 24.3 show how some animals and plants reproduce sexually. It is called sexual reproduction when two people are involved in reproduction. Sexual reproduction is when male and female gametes fuse to create a new individual. This is a common method of reproduction in animals and plants. 22.2 ASEXUAL REPRODUCTION Single-person reproduction occurs in many lower organisms, such as bacteria and protozoa, and some algae. Asexual reproduction in plants is done by vegetative propagation. Animals such as sponges and hydra can reproduce both sexually and asexually. (i) Asexual reproduction within lower organisms.
There are several types of sexual reproduction: (a) Binary Fission: A cell can divide to produce two individuals, but lose its identity. This is what happens in bacteria and amoeba (figure 24.1). (b) Budding is when a bud grows from the mother cell’s body and stays attached to it. The parental nucleus then elongates, and then splits into two. One of these moves into the bud. Example: yeast (figure 24-2). Multicellular animals such as sponges or hydra, where a bud is formed from a part of the body. It then enlarges and separates from the parent body. (c) Spore Formation: The cytoplasm of alga Chlamydomonas splits Offspring: These are the young organisms. Fig. 24.1 Binary Fission in Amoeba 24.3: Budding In Hydra Fig. 24.2: Budding In Yeast Multicellular: An organism that is made up of many cells.
The Living World, 119 Reproduction Science and Technology Notes Fig. 24.4 Spore formation in Chlamydomonas sequentially to form 4-8 spores Spores can also be formed to reproduce in moss, fungus and fern. Spores are single cells that, upon being released from their parent plants, develop into new individuals (figure 24,4.). (iii) Sexual reproduction in plants Vegetative propagation: New plants can be derived from the root, stem, or leaves of a plant, as illustrated in fig. 24.5 (a-h). This is called vegetative propagation. Table 24.1: Examples of vegetative propagation Modes of reproduction. 24.5 a&b (b) Stem(c) Leaves Adventitious root (a) Runner 24.5g) (b) Sucker(fig. 24.5g) (b) Sucker(fig. 24.5e) (f) Adventitious buds (fig. 24.5f Sweet potato, Dahlia Lawn, Chrysanthemum Onion Kartoffel, Canna Ginger Bryophyllum, Canna Ginger Bryophyllum, Canna Ginger Bryophyllum, Canna Ginger Bryogenium (B) Artificial Methods 24.6 a-c (a) Cutting (b), Layering (c), Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Graft Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose. Grafting Rose, Money Plant Jasmine. Grapevine Citrus. Mango Orchid. Chrysanthemum. Roots can be used to form new plants (fig. 24.5 a.b), stem (24.5 cm,d,e), or leaves (fig.24.5f), or when a stem reaches a certain distance, then enters soil to strike roots and form a new plant. 24.5 g.h. SCIENCE AND THE TECHNOLOGY MODULE 5 Reproduction The Living World 120 notes Fig. 24.5 (a-h) Natural vegetative reproduction in plants (iii). Artificial propagation In plants Humans have used the natural methods of vegetative growth to create many plants by artificial propagation. Fig. 24.6 illustrates the many methods that nursery owners and farmers can multiply desired plants by artificial propagation. Fig. 24.6 (a-d): Artificial vegetative reproduction in plants (c). (d): Vegetative reproduction using gootee (d). (a) The lower portion of the stem, or scion, is cut in a wedge. (b) The shoot of a plant that will be used for a stock is removed. The stem is cut vertically, and the scion is placed in the stock. The tape is then tied. (c) Graft union takes place within a very short time (a).: Cutting: A section of branch is removed and embedded into the soil. The roots form, and the new plant emerges. (b) Layering: One branch is placed on the ground, and another portion is embedded into the soil. This is the part that takes root and grows a new plant. MODULE 5 The Living World121 Reproduction Science and Technology Notes ACTIVITY 22. You can take a branch from a champa or money plant. It can be grown. Watch the growth of the branch into a fully fledged plant. 2. You might even attempt to grow grass from wild plants. What are your results? What conditions do grasses reproduce to make a carpet? Write your observations in the space provided below: (iv) Other methods of asexual propagation In the laboratories, researchers have raised offspring from single parent through tissue culture. Dolly was a sheep that was identical to her mother and was cloned. (a) Tissue culture has been standardized by micropropagation researchers. It has been proven that totipotent means that every living cell and every part of a plant is capable of giving rise to new ones. Can you explain? After you’ve finished this lesson, try to answer the question. Genes are responsible for all aspects of life, including growth and development. Cells can be taken from a piece of plant such as a root or leaf and cultured in sufficient nutrient solution. This will create a undifferentiated mass called callus, which can then be used to produce new plantlets. Micropropagation is the process of raising plants from tissue culture. (figure 24.7) Fig. Figure. Dolly was a exact copy of her mother when she was born. After removing the nucleus, the mother’s udder cells nucleus were transferred to the egg of a surrogate mother. Dolly’s mother gave her the genes, while the surrogate mom provided the womb (Fig. 24.8) to allow Dolly to grow from an embryo into a fully fledged person. Fig. 24.8 Cloning the Sheep Dolly INTERXT QUESTIONS 241 1. Define reproduction. 2. One difference between sexual reproduction and asexual reproduction. 3. Binary fission is an asexual reproduction method. 4. Use an example to help you define vegetative propagation. 5. Define the following (i) callus (ii) clone. 24.3 SEXUAL REPRODUCTION IN PLANTS You already know that sexual reproduction requires fusion of male and female gametes. Now we will see how sexual reproduction occurs in flowering plants. Surrogate mother: A female in the womb of which an embryo is being formed from another female. MODULE 5 The Living World. 123 Reproduction Science and Technology Notes (i). Sexual reproduction in plants. The flower is the reproductive organ for flowering plants (Fig. 24.9). The male part of pollen is produced by stamens (Androecium). Pollen grains contains male sex cells. Each flower may have several stamens. Each stamen (Androecium), has two parts. The anther, which bears pollen, is the upper part. It is attached to the filament at the bottom. The pistil (Gynoecium), which is the female portion, is held on the lower part called filament. Its basal part is the part of the ovary that carries eggs, ovules, or female sex cells. The pistil’s parts are the stigma, style, and ovary. Each flower in most plants bears both male parts and female parts. Bisexuals are also known as bisexual. Some plants have male flowers that only produce androecium, while female flowers only produce gynoecium. They are unisexual. ACTIVITY 24.3 Take a wilted plant and search for the stamens and pistil. Identify the parts of the flower and refer to the book for the terms. 2. Do you believe we should take flowers from plants? You can choose to answer “Yes” or “No” by selecting points from the following: * Look nice on plants * Are living * Where will butterflies go? Provide food for the butterflies. 3. What would happen if all flowers on a plant were taken? Write your answer in the space provided .(ii) Pollination and fertilisation For fusion of their nuclei, pollen and ovule are brought together by several agencies like the wind, water, and insects. Pollination is the process of transferring pollen grains from anther to the stigma of a flower. When pollen Fig. is self pollinated, it’s when pollen Fig. 24.9 TS of an Typical Flower SCIENCE & TECHNOLOGY MODULE 5 Reproduction The Live World 124 Notes of a bloom falls on its stigma and fertilizes it. Cross pollination occurs when pollen from one plant falls on another flower’s stigma and fertilizes that flower. Pollen can be transferred from one flower to the next using agents like insects, wind, and water. Any pollinating agent, including insects, can bring pollen to a flower for fertilization. Figure 24.10 shows that each pollen grain makes a pollen tube, and the pollen grains nucleus reaches an ovule when the pollen tube pushes through a pistil. The fertilized ovules become seeds that can germinate into new plants and seedlings (Fig. 24.11). (a) Gram seed to a new gram plant (b). Maize seed to a new maize plant 24.11: Seed germination in (a), gram and (b), maize INTEXT Q&A 24.2 2. Wet seeds take less time to germinate (e.g. gram, moong). Once they sprouted. Plant them in pots. Keep them until they are seedlings. Keep track of the times when they grow, flower and form seeds. 24.4 SEXUAL REPRODUCTION IN ANIMALS As mentioned earlier (24.1 section i )) lower animals like the sponge and hydra can reproduce through asexual methods. However, they can also reproduce sexually. The male produces sperms and the female makes eggs in all animals. A sperm and an egg fuse to create the zygote. The embryo then becomes a fully-fledged person. The egg may be partially or fully developed. Fish, birds, reptiles, and reptiles are all examples of oviparous animals, which can lay eggs. The baby is born in the mother’s womb, which can be mammals like cats and dogs. They are called viviparous. Tapeworms and earthworms have both male and female sex organs. These individuals are called hermaphrodites. In all animals, the sexes are distinct. The male has testes and the female has ovaries. The animal kingdom also includes humans. They are mammals, and therefore viviparous. 24.5 REPRODUCTION in HUMANS Childhood and adolescence are the periods from infancy through reproductive maturity in humans. Below are pictures that show human life’s progression through infancy, childhood and adolescence to adulthood and then ageing. Figure 24.5.1 The stages of Human Life Write down two to three sentences about each stage. Draw a picture of the stage in your life. The appropriate stages are infancy through childhood, adolescence and adulthood. MODULE 5 The Living World, 127 Reproduction Science and Technology Notes As one enters the reproductive phase of life, natural changes occur in the body. These changes occur between the ages of 10-11 years old and continue until 18-19 years old. Adolescence is the next stage of human life. Puberty is the time when humans become capable of reproducing. Humans are not the only organism that can reproduce, as no organism is mature enough to be capable of doing so soon after birth. In animals, the time between birth and maturity can be very short. It is perhaps the longest for humans. The table below lists changes that occur during adolescence. Please take a look at the table carefully. These changes are common in adolescents. However, individual timing and pace may vary. This is just another example of how each person is unique. Figure 24.2 illustrates changes during puberty. These changes can be described as psychological, physiological, and physical. Table 24.2 Developments during puberty and adolescence – SCIENCE AND TECHNOLOGY MODULE -5 Reproduction The Living World 128 Notes Both the males and females develop sex organs during adolescence. This lesson will provide more information about the structure and function of sex organs. 5. Secondary sexual characters appear as * Pubic and axil hairs. * Girls develop breasts. Boys begin to develop facial hair. * Both girls and boys can reproduce. It is essential to maintain good hygiene and clean all parts of your body, including the external genital organs for girls and testicles for boys. * Teenagers can feel sexual excitement or masturbate. A boy may experience an erection or ejaculate when he is sexually stimulated in a dream. This is called a ‘wetdream’ and it is normal. * Breast development is one sign of puberty for girls. The amount of fat in breasts can affect the shape and size of the breasts. This is normal. The size of breasts does not correlate with milk production or pleasure. What do you know? A female should immediately consult a doctor if she notices any changes in her breasts. Increased activity in sweat and oil glands
* Acne and pimples can be caused by overactivity of the oil glands. Once hormonal changes stabilize, acne will usually disappear. These can be controlled by washing your face with soap and water multiple times per day, eating lots and drinking plenty of water (8-10 glasses) daily, and avoiding foods high in fat and oil. Avoid picking pimples, as they can become infected and cause scarring. If you have severe acne, consult a doctor or health worker. * Increased sweating can lead to odours. Regular washing and cleaning will prevent this. 2. An increase in appetite The body needs more nutrition as it grows. Adolescence is a time when the body changes rapidly, making adolescents hungry more often. 3. An increase in hormone levels in blood. Blood levels of growth hormone and sexual hormones are increasing. * Growth is controlled by the anterior pituitary’s growth hormone. * The hormones secreted by the anterior pituitary influence the production of sex hormones by the sex organs. Testes produce testosterone in males, while ovaries and ovaries release oestrogen in females. 24.8 HUMAN POPULATION India could become the largest nation in terms of population, surpassing China which is the current most populous country. This will happen within the next 20 years. It’s easy to see how a large group of 1 billion people can accomplish all development goals. India is behind in many development indicators. India must make systematic and consistent investments to improve education, health and employment, as well as social welfare, before it can realize its immense human potential. It is up to you, young people like you, to move the country forward. MODULE 5 The Living World, 137 Reproduction Science and Technology Notes ActIVITY 24.8 Imagine you are the Prime Minister for India. Describe three areas where your government will invest to increase the country’s development pace so that its vast human potential can be realized. 2. India is facing problems due to its large population. Japan and Sweden, on the other hand are concerned about their declining population and offer incentives for young people to help increase their numbers. To identify the main advantages and challenges that countries with small and large populations face, please fill out the following table. India (Large Population) Sweden (Small Population) Advantages Problems Advantages Problems
24.8.1 Family Size: Making informed decisions about family size. Individuals’ decisions about the size and composition of their families will impact the country’s population growth. People’s aspirations, resources and financial status drive decisions about family size. A large section of Indian society places pressure on young couples, especially the females, to prove their fertility and have male children. Children are an integral part of a family. Unplanned pregnancies can cause serious health problems for both the mother as well as the child. The child might not have the opportunity to grow and develop holistically if his or her parents aren’t ready to support him/her financially and emotionally. While we all know that planning is important in decision-making, it is equally important to have the right information in order to make informed decisions. Planning the size and timing of childbirth can help you have a better quality of your life. You will likely have enough resources to support food, education and health for all members of your family. Who would make that decision? Below is Table 24.5 which lists some of the most recent methods to prevent pregnancy. Contraceptive methods include SCIENCE and TECHNOLOGY MODULE 5 Reproduction The Living World 138, Notes. They can be broadly divided into two types: permanent and temporary. Temporary methods can lead to fertility returning after discontinuing their use. They can be used to delay the birth or increase the interval between children. For all practical purposes, permanent methods cannot be reversed and are suitable for couples who have had their children and no longer want to have any children. After consultation with a qualified medical practitioner, couples should decide on contraceptive methods that are most appropriate for them. Table 24.5: Common Contraception Device Function Temporary Modes Condoms for males/Diaphragms for females Physical barrier that prevents the sperm from reaching the egg Intra Uterine Contraceptive device (IUCD), such as Copper T
To prevent the implantation of the embryo, inserted in the female body by a medical practitioner. Pills used to prevent ovulation by interfering with the release of ovary hormones. Fertilization is not possible because of this. These procedures should only be performed under the supervision of a qualified medical practitioner. Permanent Methods Vasectomy for males/Tubectomy for females are surgical procedures to tying the tube vasdeferens, which is how sperms travel between males and females. This prevents fertilization. There are a variety of health service delivery centers at different levels that offer contraceptive services at low or free rates. These centres may offer counselling services. 24.9 REPRODUCTIVE TRUCT INFECTIONS and SEXUALLY TRANSMITTED DIISEASES Reproductive tract Infections (RTIs), are infections of the reproductive organs. Poor genital hygiene can lead to these illnesses, such as poor MODULE-5 The Living World 139 REPRODUCTIVE TRACT INFECTIONS and SEXUALLY TRANSMITTED DISEASES. This article focuses on menstrual hygiene in girls. RTIs are sexually transmitted diseases (STDs) that can be passed from one person to the other during sexual contact. 2.9% STDs These infections can be transmitted through vaginal, anal or genital contact. Common STDs include syphilis and chancroid, chlamydia (chlamydia), syphilis, chlamydia, warts, and syphilis. Sexual contact can also transmit the Human Immunodeficiency Virus, (HIV), to others. STD symptoms include: * Itching, soreness, or anus, * Blisters and sores in the genitals * Urinary tract infections that can be foul-smelling or urinating in females and males * Pain in the lower back and abdomen. Some people may not have any symptoms but may transmit the infection to their partner unknowingly. Women are more likely to contract STIs than men because the disease-causing organisms can remain in the vagina longer. Women are more likely to remain symptomless (without showing signs of STD) for longer time periods after getting the infection. Young women are more likely to get STDs because their vaginal mucosas is still developing. If you experience symptoms of STDs, it is important that you see a doctor immediately. Most sexually transmitted diseases can be treated quickly and effectively with prompt treatment. Infertility can result from STDs that are not treated. The infected person’s sexual partner should seek medical advice. If the person infected is not cured, they should stop having sexual intercourse. STDs can easily be avoided by having one trusted sex partner and using condoms consistently. SCIENCE AND TECHNOLOGY MODULE – 5, Reproduction The Living World 140 notes 24.10 HIV/AIDS HIV/AIDS. HIV is a retrovirus, which means that its genetic material, RNA, is HIV. It causes the body to be vulnerable to many infectious agents by destroying vital cells in the immune system. It can infect T-lymphocytes, and creates thousands of copies. HIV-infected individuals may not experience symptoms for up to 15 years. As the victim loses their resistance to other diseases, the T-helper cells in the immune system gradually decrease in numbers. This is the stage known as full-blown AIDS. AIDS is a serious disease that affects 30 million people worldwide and 3 million children under 15. HIV can be passed from one person to another through the following methods: * Unprotected sexual relations * Infected blood* Infected syringes or needles: HIV-positive injection-drug users could pass on infected needles. HIV can also be transmitted through infected needles used for tattooing and acupuncture. The effectiveness of anti-retroviral therapy has been proven to stop the progression from HIV infection into full-blown AIDS. This is how HIV/AIDS can be transmitted. It cannot be transmitted by touching, kissing, holding hands or hugging. AIDS-positive people should not be stigmatized and discriminated against. T-lymphocyte is a type of white blood corpuscle which protects the body from infectious agents MODULE 5 The Living World, 141 Reproduction Science and Technology Notes 24.
Its overall function is to produce offspring. * Testes produce male sexhormones and sperm * Ovaries produce eggs and male sexhormones. * Mammary glands make milk. COMPILED BY HOWIEBAUM INTRODUCTION. The reproductive system is an amalgamation of both internal and external organs that are responsible for procreating. Many scientists believe that the reproductive system is one of the most important in the body. The reproductive system, which is one of the most important systems in the body, is also the one that has the least variation between the sexes and the only one that doesn’t function until puberty. The male reproductive system delivers sperm to the female system. MALE REPRODUCTIVE SYTEM. In males, the reproductive organs are the penis, testes, various storage and transport conduits, and some supporting structure. The testes, also known as testicles, are oval-shaped and lie outside of the body. They are kept in a pouch of skin called scrotum. This allows them to maintain a temperature that is optimal for sperm production, which is approximately 5 degrees F lower than the body’s temperature. The testes are the oval-shaped glands that produce sperm and testosterone. The epididymis is the last stage of maturation. Sperm are passed from each testis into a coiled tube called the epididymis.
INSIDE THE SCROTUM There are two testes (testicles), where sperm can be produced within tubes called seminiferous tubeules. The epididymides are where sperm can be stored. Contrary to female egg maturation which happens in cycles and ends at menopause. Sperm production is continuous and decreases with age. Each epididymis is approximately 20 feet in length and tightly coiled into a bundle of 2 inches. MAKE SPERM A testis is a mass made up of approximately 800 tightly coiled and folded vessels called seminiferous tubes. The sperm begins inside each tubule as blob-like cells known as spermatogonia that line the inner wall. They then move through a larger stage called primary spermatocytes. The secondary spermatocytes become smaller and develop tails into spermatids. They move slowly towards the center of the tubule as all this occurs. Finally, the spermatids become mature sperm with long tails. Each sperm matures in two months and produces thousands of them every second. DIFFERENCE IN SEMEN and SPERM Sperm, also known by seminal fluid (also called sperm), is more than just sperm. Only 5-10% of a male single ejaculation contains sperm. The rest are fructose, fatty acids and proteins that nourish the sperm throughout their journey. Sperm count A man can produce approximately 525 billion sperm in his lifetime, and nearly 1 billion per month. In a single human ejaculation, there are approximately 200 to 500 millions sperm. Sperm cell – A single sperm cell is approximately 1/500 inches long. However, most of it is a tail. The size of a sperm head, which is approximately 1/5000 inches, is about the same as a red blood cells. The sperm is formed in the testes. It consists of a head and a tail. The nucleus is composed of densely coiled chromatin fibers, (chromosomes), and a front section – the Acrosome – which contains enzymes that allow for penetration of the female egg. To give the tail energy and propel it forward, the midpiece contains a central filamentous core that has many Mitochondria spiraled about it.
External and internal genitalia are part of the female reproductive system. External genitalia is formed by the vulva and its components. The three-part system that makes up the internal genitalia is the uterine tubes and uterus, as well as the vagina. This system of ducts connects with the ovaries, which are the primary reproductive organs. The eggs are produced by the ovaries and released for fertilization. The uterus is where fertilized eggs are produced. The female reproductive organs, unlike the male, are entirely within the body. They are responsible for ripening and releasing eggs at regular intervals. If fertilized, they protect and nourish the embryos and fetuses. After birth, eggs cannot be manufactured – a woman is born with a complete set of eggs. Reproductive tract (Ovaries) The female reproductive glands are located in the abdomen. The menstrual cycle includes a release of this hormone approximately once per month. The ripe egg travels down the fallopian tube to reach the uterus. This is where it develops into an embryo, and then a fetus. EGG CELLS FROM OVARIES MOVE THRU THE UTERINE TUBS The uterine tubes, also known as Fallopian tubes and oviducts, connect the ovaries with the uterus. Each tube has an outer serous layer, an inner mucous layer and a middle muscular layer. The uterine tube is divided into three sections: the infundibulum Isthmus connects to the uterus. The ampulla curves above the ovary and is a dilated section. The ampulla is where egg fertilization occurs. The eggs then travel through theisthmusintotheuterus. THE VAGINA: A TUNNEL WITH THREE CORE FUNCTIONS. The vagina runs from the cervix (lower part of the body) to the vestibule. This is the part of both the external genitalia and the vulva. It is located behind the bladder and just in front of it. The smooth vaginal muscle walls are lined by an inner mucous membrane. Like the uterine tubes’ inner layers, this lining is continuous with the mucous membrane of the uterus. The vagina serves three main functions. It transports menstrual flow outside of the body. It receives the male penis when he has sex. It also acts as a birth canal during labor. OVULATION The ovary is home to thousands of mature egg cells. Folliclestimulating Hormone (FSH), which causes one egg to develop during each menstrual cycle of a woman’s period, triggers the development of an egg. This occurs inside a primary folliculum. As its cells multiply, the follicle expands and fills with fluid. This creates a secondary follicule that is able to move to the surface of an ovary. It also produces more Estrogen. The luteinizing hormone (LH), which causes the follicles to burst and release the ripe eggs, is called ovulation. The corpus luteum, a temporary source for hormones, is formed when the lining of an empty follicle becomes thicker. Undeveloped eggs, eggs from follicles that are at different stages of maturation, as well as empty follicles, all can be found in the ovary. The stroma is the bulk of the glandular tissue that surrounds these follicles. EGG AND SPERM HAVE PERFECTLY NIFTY THINGS TO MAKE CONCEPTION HAPPEN. The protection fades after about half an hour when the semen is more fluid. Call the transport unit. The cervical canal offers sperm a more inviting environment. Sperm are able to swim in the cervical mucus. The mucus was designed to efficiently transport sperm when you are most fertile. Your suddenly thick mucus becomes more flexible, clear, and thin as you get closer to ovulation. The strings of molecules become like train tracks, and the sperm can ride along them. Speed – After sperm cells have been ejaculated, they must go through biochemical changes and gain speed in order to make it into the uterus. Timing is important – Sperm must arrive at their destination in the correct timeframe to hatch the egg. It is also important to choose their destination carefully. An egg can only be found in one of the fallopian tubes each month. If the tube is not right, the sperm will end up partying with each other without a guest of honor. The best sperm wins! You should note that there are two layers to the egg that the sperm must pass through. The outer Corona Radiata irregular top and the Zona Pallucida, which is transparent but thicker. The sperm that reaches the oocyte first is not the one who will fertilize it. Instead, hundreds of sperm cells must undergo an acrosomal response, which degrades the corona reddi and zona pellucida. Once a path has been created, one sperm can contact the plasma membrane of the egg (egg) and fuse. FERTILIZATION: A STERM AND A EGG FORM A ZYGOTE. Sperm from the male penis can swim through the female uterus and vagina to an oocyte (egg) floating in one the uterine tubes. Gametes are the sperm or egg. Each contains half the genetic information required for reproduction. This genetic information is combined when sperm cells penetrate and fertilize an egg. The 23 chromosomes of the sperm are combined with the 23 chromosomes found in the egg to form a 46-chromosome cell, called a “zygote”. The zygote begins to divide and multiply. It divides as it travels towards the uterus and becomes a blastocyst. This will burrow into your uterine wall. DELEVATION PRIOR TO AND DURING IMBLANTATION: THE ZYGOTE BECOMES A ZYGOTE. It takes five days for a fertilized egg (or zygote) to reach the uterus via the uterine tube. The zygote splits as it moves and becomes a blastocyst with an inner mass and protective outer ring. The blastocyst attaches itself to the uterine wall and slowly implants itself in the uterine lining. Its cells continue to differentiate after implantation. The embryonic disc is formed by the cells of the embryo at day 15. Others cells form support structures. The digestive tract will be formed from the yolk sac on the one side of the disc. The amnion, which is filled with fluid, surrounds the embryo during its development. Other cell types initiate the placenta or umbilical cord. These cells will remove waste and bring in nutrients. ZYGOTE A fertilized egg travels along the fallopian tube. It divides into two cells within 24-36 hours, then into four cells 12 hours later, and so forth. This is called cleavage. The resulting cells shrink at each stage and gradually reach normal size. MORULA A zygote splits many times to form a blackberry-like cluster 16-32 cells. This is called the “morula”, which derives its name from Latin for “mulberry”. The morula enters the uterine cavity around 3-4 days after fertilization. BLASTOCYST Six days after fertilization, the cell group forms a hollow cavity. This is called a blastocyst. The blastocyst floats in the uterus for approximately 48 hours before landing on the thick endometrium (uterus lining). This softens to facilitate implantation (burrowing the blastocyst into its endometrium). The embryo will be made up of the inner cells. EMBRYONIC DIC An embryonic disc is formed within the inner cell mass. The embryonic disc is formed by separating the cell cluster from the amniotic cavities. This creates a sac which will fill with fluid, fold around and cover the embryo. Three circular sheets are called the primary germ layers, Ectoderm Meoderm Endoderm. These are the foundation of all future body structures.
A small number of cells are “put aside” during gastrulation, which is early in the development process. These cells later become oocytes (eggs), and sperm. These cells are called primordial germ cells (PGCs), and they are a type stem cell. Primordial germ cells are the first recognizable precursors to gametes. They arise outside of the gonads, and then migrate into the latter during embryonic development. The first time that human primordial germ cells are easily identifiable is 24 days after fertilization in the yolk sac layer. The germ cells leave the yolk sac and migrate to the hindgut tissue, where they can be found the sex organs. They can differentiate into male testis in the early years of puberty or female ovary later in life. GROWING EMBRYO As development proceeds, cells continue to divide. Cells divide to form new groups, which will eventually become tissues or organs. As genes in their chromosomes can be switched on or off, they also specialize to specific cell types. Development is generally head-down. The brain and head are formed first, followed by the body and arms, which then form as small buds. Finally, the legs. Eight weeks after fertilization, all major organs are developed. The baby is now called a fetus. 3 weeks – The neural tubes form. It will grow into the spinal cord. Pulsates the simple, tube-shaped heart. The embryo measures 4/50 to 5/50 inches in length. To be able to reproduce, HUMANS MUST GENERATE MALE GONADS OR FEMALE GENITALIA. Reproductive structures start to form during the embryonic stage. Week 6 is when gonads, genitalia and other reproductive structures are formed. One chromosome from the sperm determines whether they will become males or females. This pair includes an X sexchromosome (from the female egg) and an X or an Y sexchromosome (from the male sperm). If the chromosome pairing is XY the gonads become testes in week 7. If the chromosome pairing is XY, the gonads develop into testes starting in week 7. Testes produce testosterone and form male genitalia in week 10. Female genitalia will not form without testosterone. All reproductive structures are present at birth, or soon after. At puberty, an increase in sex hormones will grow them to their adultsizeandreproductivecapability. FOUR WEEKS Four-chambered hearts beat, sending blood through simple veins. You can see the liver, pancreas and limb buds. The embryo measures approximately 1/5 inches in length. EIGHT WEEKS The embryo is approximately 1/5 inch in length. At this stage, the neck and face shape change, the back straightens, fingers and toes can be distinguished clearly, and the back straightens. The embryo begins to move. The embryo is now approximately 1 to 1-1/5 inches in length. The embryo develops in eight weeks. BY WEEK 10, THE EMBRYO IS a fertile egg. It is now a period of fifteen days. The embryo has a flat embryonic disc. This disc now differentiates into three layers, the endoderm mesoderm and the ectoderm. These three tissues are the basis of all organs in the human body. They start to bend and fold, and then to form an oval body. The embryo develops a head and tail by week 4. It also has a beating heart. In the next six weeks, limbs and eyes develop, as well as brain regions and vertebrae. All body systems are primitive versions. The embryo is now a fetus by week 10. This refers to the gestational year of the fetus. One of the most important features of the human face is the Philtrum, or the little groove between our noses and upper lips. The Philtrum, also known as the “cupid’s bow”, is the space between the nose and the upper lip. CHANGES IN FETUS: Although the head is larger than the rest of the body by 12 weeks, its features are still distinctively human. All of the major internal organs have been developed. Even tiny nails can be found as folds on fingers and toes. Also formed are the external ears, eyelids and 32 permanent tooth buds. The rapid development of the fetus allows it to move its limbs vigorously a month later. However, this is not felt by the mother at this point. External genitalia can be seen and a fine, downy hair (lanugo), grows all over the body. The fetus continues to grow, becoming thinner and more wrinkled. However, by the seventh or eighth month it begins to gain weight and take on the appearance of a newborn. The uterus has now made the fetus somewhat smaller. The side of placenta that faces the fetus has a smooth, circular outline. The umbilical cord is attached at the center. CHANGES IN THE FIRST TRIMESTER Pregnancy lasts on average 40 weeks, usually 38 weeks after fertilization. The length of pregnancy can be divided into three trimesters or thirds. Each one lasts for approximately three months. The mother’s body experiences many changes during this period to support and accommodate the growing fetus and prepare for childbirth and breastfeeding. The breasts may become more tender, and have darkerened areolas. There is also a possibility of nausea and vomiting. SECOND TIMESTER An enlarging of the uterus may indicate an increase in heart rate. The “mask” of pregnancy is when the mother’s cheeks and forehead darken temporarily. The umbilical cord supplies nutrients-rich blood that fuels the fetus’ growth. The placenta supplies oxygen and nutrients for the fetus, and also removes any waste products from the blood. THIRD TRIMESTER Skin may stretch over the abdomen. Sometimes, slight contractions can be felt. MULTIPLE PREGNANCY and FETAL POSITIONS A multiple pregnancy is when more than one fetus is present in the uterus. One in 80 pregnancies will have twins, while one in eighteen will have triplets. These events are increasing in frequency partly because of better antenatal care, and the increased use of fertility methods like IVF (in vitro fertilization). The most common fetal position after 30 weeks is head down, facing the mother, neck flexed forward. This position allows for easier passage through the birth canal. Breech is an uncommon condition in which the baby’s stomach rises above the head. It occurs in about one in thirty full-term births. Monozygotic twins: A single fertilized egg (or zygote) forms an embryo which splits into two. Each one becomes a fetus. They share the same genes, sex, and one placenta. They are often called “identical twins” because they look the same. DIZYGOTIC TWINS Usually, a woman only releases one egg per ovulation cycle. In 1% of ovulation cycles however, there are two eggs released and both are fertilized. Two zygotes are formed, implanted, and then develop into dizygotic twins. Dizygotic twins are created from two eggs fertilized with two sperm. They are not identical to siblings born at different times. Two eggs are fertilized separately and each egg develops with its own placenta. They could have different sex or be the same. They are also known as “fraternal Twins” and have the same degree in resemblance to their brothers and sisters. FRANK BREECH Also known as incomplete breech or frank breech the baby does not turn its head in the uterus. The hips are bent and the legs straight. They extend alongside the body, so the feet are next to the head. COMPLETE BEECH The baby’s legs should be flexed at their hips and knees so that the feet are near the buttocks. This is less common than frank or breech. Premature babies are more likely to have breech deliveries. CHANGES IN CERVIX The cervix becomes more flexible in late pregnancy to prepare for childbirth. Braxton-Hicks contractions are sporadic uterine tightenings. They thin the cervix to allow it to join the lower segment of the uterus. Braxton-Hicks contractions can be felt throughout pregnancy. They are often painless and become noticeable after the second trimester. Softening of the Cervix as labor approaches. The cervix tissues begin to lose their firmness. Prostaglandins, natural substances found in blood, cause them to soften and become more spongy. CERVIX THINNING As the cervix grows in width and thickness, it merges seamlessly with the uterus wall. Effacement is the process of softening or thinning. CONTRACTS The uterus, which is the largest and most powerful muscle in the female body, becomes full-term when pregnancy reaches its peak. It is also known as a “contraction” or a uterine contraction when its muscle fibers become shorter with the ultimate goal of removing the fetus. Contrary to Braxton-Hicks contractions which are irregular and more frequent than Braxton-Hicks ones, true contractions are more regular, more painful and last longer. The main area of contraction lies in the uterine Fundus (upper uterus), where it stretches and thins the lower uterus. False alarms can make it difficult to determine when labor is actually starting. EPIDURAL ANALGESIA Epidural analgesia is one of the most common methods for pain relief during labor and delivery. It is administered via a needle through the space between the vertebrae, the spinal column, and the lower (lumbar), region of the back. It causes contraction pains to be felt by the nerve fibers. The “walking epidural”, a new type of epidural that reduces pain but does not remove sensation, allows women to move during labor and take part in the birth process. The process of labor starts around week 36 (usually). The first stage of dilation is when hormones trigger downward contractions in the uterine walls. The contractions push the head against the cervix at lower end of the body. The cervix dilates. The second stage of expulsion is when powerful contractions push the head, along with the rest, through the dilated cervical and out through the vagina. The baby is now born. To complete the placental stage, further contractions will expel the placenta