As for now, we all should know that human existence and population rely heavily on the process of sexual reproduction.
In this Biology Form 5 reproduction topic, you will be learning in-depth about the features of the anatomical system of human reproduction, understand how the gametes are formed, how the period cycle happens, as well as the development of the human fetus with a Biology background.
How are the male and female reproductive systems different?
Females and males have different features of the reproduction system.
Female Reproductive System
Let’s take a look at the female reproductive system.
- An organ with a thick muscular wall. The inner wall is lined with endometrium tissue. It secretes mucus.
- A thin muscular tube. The inner wall is lined with cilia.
- An organ that produces the ovum and the female sex hormones, which are the estrogen and the progesterone.
- A narrow opening to the uterus that helps sperm swim up to the Fallopian tubes.
- A canal where sperm enter and also act as a passage for menstruation and birth.
Male Reproductive System
Now that we understand the female reproductive system and its function, let’s move on to the male reproductive system.
- An organ that secretes fluids that are filled with nutrients for the sperm.
- This is where the sperm is transported from the testis to the urethra.
- An organ that secretes fluid. The fluid helps the sperm movement.
- A sac-like structure that holds and protect the testis.
- An organ that produces sperm and the male sex hormone, which is the testosterone.
- An organ that releases sperm into a female’s vagina during copulation.
- A tube where sperm and urine are discharged from a male’s body.
You can refer to Biology form 4 for a detailed explanation of these reproductive systems. We would also recommend you to look out for Science form 3 and Science form 2 all chapters' notes.
There are some topics in Biology that have been taught briefly in form 3 and form 2 Science textbooks. You can also refer to those textbooks.
What are the phases of gametogenesis?
Gametogenesis is the production process of reproductive cells (gametes). This process happens in the gonads. Gonads are the primary reproductive organs. The gonads for a female are the ovaries and for a male is the testis.
Gametogenesis produces gametes that are haploid. A haploid is a cell that contains a single set of chromosomes. These chromosomes are responsible for the offspring variation since they inherited them from their parents.
Spermatogenesis is the process of sperm production. The process takes place in the seminiferous tubules. Each of the seminiferous tubules consists of primordial germ cells.
Primordial germ cells undergo cell division to produce sperm.
The sperm production has three phases:
- Primordial germ cells divide mitotically to create diploid spermatogonium.
- This spermatogonium develops to form primary spermatocytes (diploid).
- Each primary spermatocyte goes through meiosis I to develop two secondary spermatocytes (haploid).
- Each secondary spermatocyte is subjected to undergo meiosis II to produce haploid spermatids.
- Spermatids undergo differentiation to form sperms.
Oogenesis is the process of secondary oocyte or female gametes production. This process occurs in the ovaries. It starts in a female’s ovaries before they are born.
- Primordial germ cells undergo mitotic division multiple times to form oogonium (diploid).
- Oogonium develops into the primary oocytes. It is encapsulated with one or more layers of follicular cells to dorm primary follicles.
- The primary oocyte undergoes meiosis and stops at prophase I during fetal development.
- At birth, a baby girl already has millions of primary oocytes which remain dormant in the prophase I meiosis.
Puberty (Meiosis I)
- Once they reach puberty, the primary oocyte will continue meiosis I to form a secondary oocyte and a first polar body.
- Secondary oocyte will begin meiosis II and halted at metaphase II.
- The first polar body will complete meiosis II and form two polar bodies.
Puberty (Meiosis II)
- The second oocyte (immature ovum) will complete meiosis II once a sperm penetrates it.
- Meiosis II produces the ovum and the first polar body.
- Fertilization takes place once the sperm nucleus fuses with the ovum nucleus and produce a diploid zygote.
- The rest of the polar bodies will die and be disintegrated by the ovary.
What is the menstrual cycle?
The menstrual cycle is the process of the production of a secondary oocyte and thickening of the endometrial wall. The endometrium will be soft, thick and rich with blood vessels in order to prepare it for embryo implantation.
If the fertilization does not occur, the secondary oocyte will die and the endometrium will shed. This will cause bleeding, which is called menstruation.
Hormones and their function in the menstrual cycle
Here are the hormones released during the menstrual cycle. Each of them has its own functions.
Follicle-stimulation Hormone (FSH)
- To stimulate follicle growth in the ovary.
- To stimulate the release of estrogen.
Luteinizing Hormone (LH)
- To stimulate ovulation.
- To stimulate the release of progesterone.
- Causes the formation of the corpus luteum.
- To repair and stimulate the thickening of the endometrium.
- To stimulate follicle growth until it reaches maturity.
- To stimulate follicle-stimulation hormone and luteinizing hormone release prior to ovulation.
- To stimulate the thickening of the endometrium to prepare it for the implantation of an embryo.
- To stop the release of the follicle-stimulation hormone and luteinizing hormone to prevent follicle growth and ovulation.
What are the stages of embryonic development?
The process of fertilization happens when one of the millions of sperm managed to penetrate the secondary oocyte in the Fallopian tube.
It occurs by the changes to the secondary oocyte’s membrane that prevent other sperm to penetrate and the sperm nucleus fuses with the ovum nucleus. The infusion of the sperm nucleus and ovum nucleus will form a diploid zygote.
Development of a human fetus
The early development of an embryo starts when the zygote undergoes multiple divisions through mitosis. The first cell division produces a two-cell embryo. The division will keep on going until a morula is produced.
The morula transforms into a blastocyst and then get implanted in the endometrium through a process called implantation. The blastocyst continues to grow into an embryo.
The embryo soon starts to form the body structure and other organs including the digestive system. You can do revision on the human digestive system using the textbook Science form 2.
Human Chorionic Gonadotropin (HCG) Hormone Function
The human chorionic gonadotropin (HCG) hormone is produced by the placenta during pregnancy. The function of this hormone is to ensure that the corpus luteum continues to secrete estrogen and progesterone in the early stages of pregnancy. The level of this hormone increases in the early stages of pregnancy.
The placenta is formed by the mother’s endometrial and embryonic tissues. It is connected to the fetus through the umbilical cord that contains blood vessels that carries substance in and out of the fetus.
The umbilical cord is a tube that contains the umbilical vein and umbilical arteries.
- Umbilical vein - carries blood rich in oxygen and nutrients from the placenta to the fetus.
- Umbilical arteries - carry deoxygenated blood rich in carbon dioxide and nitrogenous waste, such as urea from the fetus to the placenta.
The placenta is important because:
- Acts as an exchange site of substances between the mother and the fetus.
- Acts as an endocrine organ that secretes hormones during pregnancy.
How to measure the growth in humans?
In Science form 2, you already learned that human growth can not be reversed. It is a permanent process that involves the development of a number of cells, size, volume and weight of a human. This process is important for the development and maturation of a bodily system.
Parameters used to measure human growth
There are a few parameters that are used in order to measure human growth:
Size or volume
- The increase of number in size or volume, for example, the increase in height of a person. The height of a person may be dictated by the genes of the parents. But other factors such as nutrition, gender and hormones also play important roles to determine a person's height.
- Changes in weight. For humans, this parameter is usually taken according to the fresh weight. Fresh weight is a less accurate method because the measurement of the weight includes the amount of fluid in the body. This method depends heavily on the amount of a person’s fluid intake.
6 phases of human growth
The growth curve is achieved by plotting growth parameters against time. Humans’ growth patterns usually following a sigmoid curve (S-shaped). It occurs gradually and continuously in six obvious phases:
- The low growth rate is caused by the little cell division and cell elongation.
- The highest growth rate occurs in this phase, when the cell division and cell elongation are actively developed.
- Human growth slows down and eventually stays at a constant rate. This is because the cells have reached their maximum size.
- In this phase, there will be zero growth in the cell because humans reached maturity. The cell division still happens but only to replace impaired and dead tissues.
- Cell growth starts to decrease when a human goes through an ageing phase.
- This phase is caused by ageing, illness or lack of nutrients leading to death.
The reproduction, development and growth in humans topic requires a deeper understanding of some genetic terms and genetic information, which can also be found in the form 4 science textbook. It could be really hard if you do not have the basics of bio-life.
But you do not have to worry. You can also look for a tutor by searching ‘Biology tuition near me’ or opt for a home tutor online. There are always options for you to look for a Biology private teacher from Superprof to help you out.
Superprof is a well known online tutoring website where you can find your ideal tutor to assist you in a bio-life subject. It has a wide database of experienced Biology tutors that can help you with your other SPM Biology syllabus such as biodiversity.
And the best of all is that most of the tutors offer the first one-hour tutoring session for free! Check out the website and look around for your preferred Biology tutor.
Are you looking for a home tuition Malaysia?
The platform that connects tutors and students