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Topic 17: Reproduction 17.3 Sexual reproduction in humans •Identify and name on diagrams of the male reproductive system: the testes, scrotum, sperm ducts, prostate gland, urethra and penis, and state the functions of these parts • Identify and name on diagrams of the female reproductive system: the ovaries, oviducts, uterus, cervix and vagina, and state the functions of these parts • Describe fertilisation as the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell/ovum) •State •State the adaptive features of sperm and egg cells that in early development, the zygote forms an embryo which is a ball of cells that implants into the wall of the uterus Sexual Reproduction in Animals Reproduction - Ability to produce individuals (offspring) of the same species Most animals reproduce sexually. In sexual reproduction male and female parents produce sex cells or gametes, the nuclei of which contain the genetic material. Sexual reproduction in humans Humans are characterized by: Internal fertilization: means that the gametes (sex cells) fuse inside the body of the female Internal development: means that the embryo grows inside the body of female Gonads are the organs responsible for producing gametes Male gonads are testis Female gonads are ovaries Male sex cell Male gamete = sperm – produced in testes and deposited though intercourse (mating) into female reproductive tract by male reproductive system Female sex cell Female gamete – egg (ovum) – produced in ovaries – fuses with male sperm to form a zygote (which develops into a baby) in the female reproductive tract. The egg cell has energy stores and a jelly coating that changes after fertilisation A human egg surrounded by sperm - one of which will fertilise it fertilization Each gamete contains half the number of parental chromosomes. The two gametes fuse together during fertilisation to make a new individual with a full set of chromosomes The sperm has flagellum for swimming to reach the ova and the presence of enzymes to digest the wall of ova Reproductive system Male reproductive system Carries urine from kidney to bladder Secretes fluid known as the seminal fluid to mix with the sperm, this fluid consists of: •Mucus: facilitate copulation and swimming of sperms •Sugars(fructose) : provide energy for sperm •Alkaline material to neutralize the acidity of urethra and vagina Coiled tube, Storage of sperm Site of sperm maturation Carries sperm from epididymis to urethra in penis by wave-like muscular contractions (peristalsis) to help in ejaculation Sac of skin, containing testes – hold it outside the body At lower temperature (below body temperature of 370C) for sperm formation Sperm cannot survive for long at 370C Produces sperm and the hormone testosterone (sex hormone) Common passage for both urine and semen (semen is the sperms plus the fluid produced by prostate gland and seminal vesicles) Has muscular wall to contract to help in ejaculation Male reproductive system Penis: Organ of copulation Contains erectile tissue which has blood cavities, when penis is stimulated blood fills the cavities making the penis long and strong enough for copulation, this is known as erection Covered with a piece of fore skin which is removed in the process of circumcision Female reproductive organ •Narrow tube carrying eggs from the ovaries to the uterus •Has ciliated cells to push the ova into the uterus •Site of fertilisation Muscular organ site of implantation of fertilises egg and embryo Site of formation of placenta Are two , right one and left one •Produces and releases ova (singular: ovum) into the oviduct •Produces hormones •Oestrogen – repairs uterine lining after menstruation •Progesterone – maintains uterine lining after repair Organ of copulation Muscular and elastic tube into which male penis is place during intercourse Expand during birth Muscular ring that separates the uterus and vagina Secretes mucus to help the sperm to swim Some adaptations: Uterus: the lining is soft and spongy with many blood vessels to supply the embryo with food and oxygen In the lining implantation of the embryo takes place (where the emvbryo fixes itself to the lining of uterus If there is no fertilization the lining is broken down releasing blood , this is called menstruation Some adaptations: Vagina: Expands during birth Secretes mucus to facilitate the movement of male organ during copulation Secrets acid to kill bacteria and other microorganism Intercourse Due to stimulation, the blood pressure increases in the penis and becomes stiff and erect The penis is inserted in the vagina and moves rhythmically The muscles of epididymis, sperms ducts and urethra contract in a wave motion to push sperms Seminal vesicle and prostate gland produce seminal fluid to be mixed with sperms and form the semen Fertilization Sperms are deposited on the top of vagina below the cervix Sperms swim using their tails through the cervix and the film of moisture lining the uterus Sperms are attracted to the ovum due to chemicals it produces Many sperms reach the egg, each sperm produces enzymes from its head to digest a way into the egg The sperm leaves the tail outside then the nucleus of the sperm and that of ovum fuse together to form the zygote Once a sperm has succeeded in penetrating the egg , a fertilization membrane is formed quickly to prevent any other sperm enter the ovum Some definitions Zygote: a cell formed due to the fusion of a male gamete and a female gamete Embryo: a ball of cells formed due to division of the zygote by mitosis Fetus: a mammalian embryo in advanced stage of development embryo Implantation (read only) Formation of embryo due to successive division of the zygote by a method of division called mitosis Menstrual cycle stops, until after the baby is born Implantation takes place, the process by which the embryo attach to the lining of uterus Formation of amnion and placenta What will happen if no fertilization ? Next slide Reproduction Sexual reproduction part 2 State the functions of the umbilical cord, placenta, amniotic sac and amniotic fluid Outline the processes involved in labour and birth Describe the ante-natal care of pregnant women, limited to special dietary needs and the harm from smoking and alcohol consumption Menstruation It is the break down of the lining of the uterus in case there is no fertilization It takes place due to a drop in the level of hormone called progesterone (the function of this hormone is to maintain the lining of the uterus) Menstruation and ovulation Ovulation is the release of ova into the oviduct, it takes place at day 14 of the menstrual cycle menstruation estrogen ovulation Amnion(amniotic sac or water sac) Secretes amniotic fluid which: 1. Act as shock absorber 2. Protects the embryo against adhesion of organs. 3. facilitates the movement of fetus placenta The placenta is an organ that connects the developing fetus to the uterine wall Blood in placenta includes: Maternal blood from uterine artery Fetal blood from umbilical artery and the umbilical vein in the umbilical cord Importance of placenta: 1. 2. 3. 4. Exchange of gases: Oxygen from mother’s blood diffuses into fetal blood CO2 from the fetal blood diffuses into mother’s blood Nutrition: Food such as glucose and amino acids diffuses into fetal blood Excretion: Waste products such as urea diffuses from fetal blood into mother’s blood Secretion of hormones: Secretes estrogen and progesterone to: Keep the uterine lining support the embryo Stimulate the growth of milk-producing tissues in the woman’s breast Prevent anymore to be released during pregnancy Importance of placenta: Fetal blood and maternal blood never mix in the placenta so : Protects the fetus against high blood pressure Protects the fetus against bacteria from mother’s blood(but viruses like HIV can pass because they are very small) 5. Umbilical cord Connects the placenta and fetus It contains: Umbilical artery: carries CO2 and other waste products of the fetus to placenta Umbilical vein: carries O2 and food materials from placenta to fetus How to care for the baby Ante-natal care Diet: Must include protein for building cells More carbohydrates and fats for energy More minerals as calcium for bones and iron to form hemoglobin 2. Drugs: Extra precautions Drugs must be avoided because they can pass through the placenta to fetal body and cause abnormalities 1. 25 How to care for the baby Ante-natal care Smoking: Must be avoided, it can result in small and less healthy body because: CO (carbon monoxide) can reduce the oxygen supply as it combines with hemoglobin forming stable carboxyhemoglobin Nicotine makes the fetal heart beats more quickly 3. 26 Smoking abnormalities 27 How to care for the baby Ante-natal care Alcohol: Should be avoided because it causes Abnormalities in fetus Premature baby Miscarriage 4. 28 Alcohol abnormalities 29