Chapter_15_Sexual_Reproduction,Development_and_Growth_in_Humans.pptx

science form 3

1. CHAPTER 15 SEXUAL REPRODUCTION, DEVELOPMENT AND GROWTH IN HHMANS AND ANIMALS

2. 15.1: REPRODUCTIVE SYSTEM OF HUMANS

3. The Male and Female Reproductive System OVARY Produces ovum and the female sex hormones (oestrogen and progesterone) FALLOPIAN TUBE A thin, muscullar tube The inner wall is lined with cilia The action of cilium and peristalsis of the fallopian tube deliver embryo to the uterus UTERUS Has thick muscular walls. The inner wall is lined with endometrium tissue, which secretes mucus and rich in blood vessels. Supplies implanted embryo with netrients and oxygen. CERVIX Narrow opening to the uterus Secretes mucus to help sperm swim up to the fallopian tubes VAGINA A canal where sperm enter As a passage for birth and menstruation

4. The Male and Female Reproductive System TESTIS Within the scrotum. Produces sperm and the male sex hormone (testosterone) PROSTATE GLAND Secretes a fluid that helps in sperm movement. SPERM DUCT Transport the sperm PENIS Rich in tissues and blood vessels Releases sperm into the a female’s vagina during copulation SCROTUM A sac-like structure that holds and protects the testis URETHRA A tube for the discharge of sperm and urine from the body

5. 15.2: GAMETOGENESIS IN HUMANS

6. The Necessity of Gametogenesis Gametogenesis is the production process of reproductive cells (gametes) Take place in the gonads ; Testes in males Ovaries in females. Produce haploid (n) gametes and after fertilisation occurs form a diploid zygote (2n)

7. Each seminiferous tubule consists of primordial germ cells . SPERMATOGENESIS Primordial germ cells undergo cell division to produce sperm. Sertoli cells within the seminiferous tubules provide nutrients throughout this process. Sperm is transported from the seminiferous tubules to the epididymis and flows out through the sperm duct . Sperm duct (vas deferens) epididymis Seminiferous tubules The process is stimulated by the follicle-stimulating hormone (FSH) and testosterone also aided by the luteinizing hormone(LH) which stimulates testosterone secretion in the testes. A process of sperm production takes place in the seminiferous tubules .

8. Spermatogonium expands to form primary spermatocytes (diploid) . Primordial germ cells divide mitotically to form diploid spermatogonium . Each primary spermatocytes (diploid) . Undergoes meiosis I to form two secondary spermatocytes (haploid) Spermatogonium primary spermatocytes development repetitive mitotic divisions Primordial germ cell meiosis I secondary spermatocytes

9. Spermatids undergoes diferrentiation and form sperms Each secondary spermatocyte undergoes mieosis II to produce two haploid spermatids meiosis I secondary spermatocytes meiosis II differentiation spermatid sperm

10. Oogonium develops into primary oocyte . Primary oocyte is encapsulated with one or more layers of follicular cells, forming primary follicles. The groth of the follicle is stimulated by FSH. Primary oocyte undergoes meiosis and stops at prophase I during fetal development. Primordiall germ cells undergoe mitotic division multiple times to form oogonium (diploid) BEFORE BIRTH primordial germ cell oogonium mitosis development 2 1 OOGENESIS A process of female gamete production takes place in the ovaries.

11. Reaching puberty, the primary oocytes continue meiosis I to form secondary oocyte and a first polar body . Secondary oocyte will begin meiosis II which is then halted at metaphase II and form two secondary polar bodiess . At birth, a baby girl has millions of primary oocytes that remin dormant in prophase I meiosis I and decreasing at puberty. A layer of follicular cells envelops the secondary oocyte ( secondary follicle ), and then develop into Graafian follicle (release oestrogen) 3 4 5 AFTER BIRTH

12. The secondary oocyte (immature ovum) compelete meiosis II onve a sperm penetrates it. Meiosis II produces ovum (n) and first polar body (n). Fertilisation takes place when the sperm nucleus fuses with ovum nucleus and produces a diploid zygote (2n). Ovulation occurs A mature Graafin follicle approach the ovary’s surface and release secondary oocyte into the Fallopian tube After ovulation, the remaining follicle forms corpus luteum. Corpus luteum continues to grow and secretes oestrogen and progesterone. Corpus luteum and secondary oocyte degenerate and dies and then is removed through menstruation 7 8 6 10 9

13. STRUCTURE OF SPERM AND GRAAFIAN FOLLICLE Three main parts: head , midpiece and tail . Head contains a nucleus. The midpiece is full of mitochondria to generate energy for the sperm to swim. A secondary oocyte is a large cell that is surrounded by a gel-like substance and follicular cells. The secondary oocyte and follicular cells will form the Graafian follicle. Secondary oocyte Follicle cells

14. MENSTRUAL CYCLE 15.3:

15. Role of Hormones in Menstrual Cycle MENSTRUAL CYCLE Involves the production of a secondary oocyte and thickening of the endometrial wall throughout one cycle. In this cycle, the endometrium become soft, thick and rich with blood vessels to prepare the endometrium for embryo implantation. If fertilisation does not take place, the secondary oocyte will die and the endometrium wall will shed lead to bleeding known as menstruation .

16. GLAND HORMONE FUNCTION Pituitary Follicle-stimulating hormone (FSH) Stimulates follicle growth in the ovary Stimulates the release of oestrogen Luteinizing hormone (LH) Stimulates ovulation. Causes the formation of the corpus luteum. Stimulates the release of progesterone. Ovary Oestrogen Repairs and stimulates the thickening of the endometrium. Stimulates follicle growth until it matures. Stimulates FSH and LH release prior to ovulation. Progesterone Stimulates the thickening of the endometrium, making it thick, folded and rich in blood vessels to prepare for the implantation of embryo. Stops the release of FSH and LH to prevent follicle growth and ovulation.

17. DAY 0-5 Before a menstrual cycle begins, the level of hormones is low, cause the thickened endometrium will shed and menstruation will begin (first day). A menstrual cycle begins when the hypothalamus releases the gonadotrophin-releasing hormone (GnRH). GnRH stimulates the pituitary gland to release the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) into the blood. FSH stimulates follicle growth in the ovary . Within the primary follicle, the oocyte grows into the secondary oocyte, which is contained within the Graafian follicle. Growing follicles release oestrogen which encourages follicle maturation and also encourages endometrial wall repair. Low levels of oestrogen inhibit the release of FSH and LH via a negative feedback mechanism, which in turn prevents the growth of new follicles.

18. DAY 6-14 Oestrogen level rises and peaks on day 12, stimulating the hypothalamus to secrete GnRH A high level of GnRH stimulates the pituitary gland to secrete more FSH and LH. The LH level rises until it peaks on day 13, leading to ovulation and release of a secondary oocyte from Graafian follicle on day 14. LH also stimulates the follicular tissue left behind to transform into the corpus luteum . DAY 15-21 LH stimulates the corpus luteum to secrete oestrogen and progesterone. Oestrogen and progesterone inhibits the release of FSH and LH from the hypothalamus to stop the growth of new follicles. Progesterone stimulates endometrial wall thickening, enriching it with blood vessels in preparation for embryo implantation if the fertilisation takes place.

19. DAY 22-28 If fertilisation does not take place, decreasing LH levels will cause the corpus luteum to degenerate, which in turn stops the secretion of oestrogen and progesterone. Without stimulation from oestrogen and progesterone, the endometrium will shed and menstruation will begin. Low levels of progesterone and oestrogen will no longer inhibit the hypothalamus and pituitary gland, for secreting GnRH again, which stimulates secretion of FSH and LH. A new menstrual cycle will begin with new follicle growth. If fertilisation occurs, the corpus luteum will continue to grow and secrete progesterone and oestrogen . This will cause the endometrial wall to continually thicken in order to support foetal growth.

20. Roles of Hormone in Pregnancy and Miscarriage The corpus luteum will continue to produce oestrogen and progesterone up to three to four months after pregnancy. Thereafter, the corpus luteum will degenerate. Progesterone inhibits the secretion of FSH and LH . Therefore, the menstrual cycle and ovulation do not occur throughout a pregnancy. The imbalance of progesterone and oestrogen levels may lead to a miscarriage, due to the decrease of progesterone level which causes the uterus to shrink . The production of oestrogen and progesterone will be taken over by the placenta until birth.

21. Premenstrual Syndrome and Menopausal Syndrome Premenstrual Syndrome Menopause Symptoms that appear prior to a menstrual cycle usually manifest between 7 to 14 days before the first day of the menstrual cycle due to the imbalance of oestrogen and progesterone hormones within the menstrual cycle. Example: Headache, emotional instability and bad temper Occurs within ages of 46 to 50 years old when ovulation and menstruation stop naturally due to reduced secretion of progesterone and oestrogen , cause the FSH and LH stimulation on ovaries are reduced. The ovaries stop producing ovum. Example: Difficulty sleeping, Hot flushes, Low mood and Bad temper

22. 15.4: DEVELOPMENT OF A HUMAN FOETUS

23. The zygote undergoes multiple division through mitosis Fertilisation and The Development of An Embryo until Implantation Fertilisation : Occurs when the sperm nucleus fuses with the ovum nucleus to form a diploid zygote. Cell divided until produce morula . The morula transforms into a blastocyst . The blastocyst implant in the endometrium ( implantation ) and continues to grow into an embryo .

24. unfertilised secondary oocyte fertilisation zygote 2 cells 4 cells 8 cells morula endometrium blastocyst The thickened blastocyst wall will develop into embryo placenta foetal blood vessels maternal blood foetal blood capillaries umbilical cord umbilical arteries umbilical vein

25. Role of Human Chorionic Gonadotropin (HCG) Hormone Produce by the placenta during pregnancy. The level of HCG hormone increases at the early stages of pregnancy and double every two to three days in the 1 st four weeks of pregnancy. Detected in the urine of pregnant women. The function: Ensure that the corpus luteum continues to secrete oestrogen and progesterone in the early stages of pregnancy

26. PLACENTA Formed from the mother’s endometrial tissue and embryonic tissue. Connected to the foetus through the umbilical cord. UMBILICAL CORD A tube that contains : Umbilical vein carries blood rich in oxygen and nutrients from placenta to the foetus. Umbilical arteries carry deoxygenated blood and nitrogenous waste (urea from foetus) Role of Placenta and Umbilical Cord in Foetal Development Importance of placenta: The exchange site of substances between mother and foetus Acts as an endocrine organ that secretes hormones during pregnancy

27. Foetal and Maternal Blood Circulatory Systems The blood of the mother and the foetus do not mix and separated by a thin membrane. The importance: Protects the foetus from dangerous chemical such as toxins and bacteria that can be absorbed into the foetal blood circulation. Prevents the thin foetal blood vessels from bursting due to the mother’s high blood pressure. Prevents agglutination or blood clots from happening in the foetus, as the foetus’s blood might not same blood group as the mother. The thin membrane layer: Allow certain substance from being absorbed (drugs, medication, cigarette smoke and alcohol) Allow viruses (HIV and rubella) across the placenta

28. 15.5: FORMATION OF TWINS

29. Process of Twin Formation Types of Twins Identical Twins Fraternal Twins One ovum & one sperm forming one zygote Embryo divides into two One placenta is shared between two foetus Physical appearances are similar The sex of both twins is the same Two ova & two sperm forming two zygote Embryo does not divide Each foetus has its own placenta Physical appearances are different The sex of both twins may be the same or different

30. Development of Conjoined Twins Developed when there is in complete division of the embryo in identical twins. Some physical parts are still fused together (chest, abdomen or buttocks) They do not have time alone and have limited movement. Might have short lifespan. Might share one or two internal organs Can be separated through surgery.

31. 15.6: Health Issues Related to The Human Reproductive System

32. Impotency Causes of Male Impotency Testes do not produce sperm Erectile dysfunction Low sperm count Low quality sperm/ Abnormal sperm Hormonal imbalance Causes of Female Impotency Ovaries do not produce secondary oocyte Blocked Fallopian tubes Growth in the uterus Abnormal uterus Hormonal imbalance TREATMENT: Hormonal imbalance 🡪 Hormonal therapy Blocked Fallopian tubes or blocked sperm ducts 🡪 Surgery Blocked Fallopian tubes 🡪 In vitro fertilisation (IVF)

33. 15.7: Growth in Humans and Animals

34. Growth in Organisms Permanent process that involves the increase in the number of cells, size, volume and weight of the organism’s body. Involves in specialising the shapes and functions of cells. Important for the development and maturation of body system. Parameter to measure the growth: Increase in size or volume Fresh weight – Less accurate because the amount of fluid in the body depends on the organism’s fluid intake. Dry weight – Dried at 100°C and the organism has to be killed

35. Growth in Insects Complete Metamorphosis Incomplete Metamorphosis A few stages of ecdysis 4 different stages of growth

36. Growth Phases in Sigmoid Growth Curves of Humans and Animals LAG PHASE The growth rate is low because it involves little cell division and cell elongation. The phase of adjustment to new sources available in the environment. EXPONENTIAL PHASE Highest growth rate. Cell division and elongation occurs actively Organism’s size increases rapidly. STATIONARY PHASE Slow growth rate and occurs at a constant time. Cell reach maximum size. Cells undergo differentiation to form specialised cells.

37. Growth Phases in Sigmoid Growth Curves of Humans and Animals MATURITY PHASE Zero growth rate. Organism reaches maturity. The rate of cell division = the rate of cell death Cell division happens to replace impaired or dead tissues. SENESCENCE PHASE Negative growth rate. Organism goes through ageing DEATH PHASE Ageing, illness Lack of nutrients or space.

38. Intermittent Growth Curve of Animal with Exoskeletons Animal with exoskeletons must shed their hard exterior (known as ecdysis process) controlled by hormones. The polar growth is intermittent . Zero growth, the insect is not increasing in length. Rapid growth, the nymph undergoes ecdysis and increase in size rapidly. A new exoskeleton form underneath the old exoskeleton. Before it hardens, the insect increase its volume by sucking in air to expand its body. This action breaks the old exoskeleton and the insect with its new exoskeleton will emerge The insect expand its body one more time. ECDYSIS PROCESS