Sec 2 Science - Chapter 12: Human Sexual Reproductive System PDF

Chapter 12: Human Sexual Reproductive System 12.1 Human sexual reproductive system 12.2 Sexual reproduction 12.3 Premarital sex and abortion 12.4 Birth control methods 12.1 Human sexual reproductive system Reproduction is the process by which humans produce new organisms like themselves....

Chapter 12: Human Sexual Reproductive System 12.1 Human sexual reproductive system 12.2 Sexual reproduction 12.3 Premarital sex and abortion 12.4 Birth control methods 12.1 Human sexual reproductive system Reproduction is the process by which humans produce new organisms like themselves. It ensures the continuity of a species. Humans reproduce through sexual reproduction, which involves a male reproductive cell from a male and a female reproductive cell from a female adult. A male has the male reproductive system while a female has the female reproductive system. Reproductive Cells/Gametes These cells are haploid. Which only has 23 chromosomes which also enables them to fuse. - The human sperm (male) is about 0.06 mm long - The human egg/ovum (female) is spherical and has a diameter of 1.20 mm Male Reproductive System 1. Penis - becomes erect when sexually excited, which makes sexual intercourse happen - semen is ejaculated through here - each ejaculation contains about 100,000,000 millions of sperm  2. Urethra - a tube which leads to the outside of the body through the penis - sperms pass from the testes into the sperm ducts and then into the urethra. - joins the base of the bladder where urine is stored - during sexual intercourse, the opening between the urethra and the bladder is closed so that urine and semen never mix. 3. Sperm Duct/Vas Deferens - there are 2 sperm ducts, one for each testis. 4. Testis - produces sperms and male sex hormones (testosterone) - these hormones are responsible for development of male characteristics during puberty. 5. Scrotum - a sack that hangs outside the body, where the temperature is slightly lower than body temperature (35-37 Celsius) - this lower temperature is important for production of healthy sperm 6. Male sex glands - secrete an alkaline fluid which contains nutrients and enzymes needed by the sperms - Prostate Gland, Cowper’s Gland, Seminal Vesicle - Fluid + Sperm = Semen Additional - Epididymis → temporary storage of inactive sperms - Ureter → Transports urine Female Reproductive System 1. Vagina (Birth canal) - a muscular tube - joins the cervix to the outside of the body 2. Cervix - a ring of muscle located in the bottom of the uterus - enlarges to allow the foetus to pass through during birth 3. Ovary  - produces eggs and female sex hormones (estrogen, progesterone), which are responsible for developing female characteristics during puberty - from puberty and onwards, an egg is released from one ovary per month. A total of 250 eggs will be produced a lifetime - when a woman reaches the age of 45-55, egg production will slow down and finally pause, reaching menopause. 4. Uterus - a pear-shaped organ with thick muscular walls - the uterus is the place where the foetus develops - the inner surface is covered by a small, smooth layer called the uterine lining. Which breaks down and sheds with some blood every month from puberty onwards. 5. Oviduct/Fallopian Tube - the egg released from the ovary is pushed along here towards the uterus by muscular contractions of the wall of the oviduct. - where the sperms meet the egg 12.2 Sexual reproduction Sexual reproduction involves the fusion of the sperm and the egg through the process of fertilisation. For a woman to get pregnant, she must have sexual intercourse with a male adult.  1. During sexual intercourse, the erect penis is inserted into the vagina 2. The penis ejaculates semen (containing sperms) into the upper end of the vagina. The sperms will then swim into the uterus. Fertilization  1. Sperms deposited in the vagina during sexual inter course will travel up the uterus through the oviduct and into the egg. 2. If an egg is present in an oviduct, fertilisation may take place. 3. The fertilised egg divides repeatedly to form an embryo 4. The embryo moves into the uterus where it is implanted on the uterine lining. This results in pregnancy. Pregnancy - lasts 9 months in humans - during pregnancy, the embryo forms into a fetus. - at the end, the fetus will exit as the muscles of the uterus contract and the cervix is enlarged. This process is called birth. Weeks 1-4: Arms and legs begin to develop, the embryo has a little tail. Week 7: nose, ears and fingers can be seen. Week 11+ : The embryo can be called a fetus as it looks like a baby Week 20: The fetus looks more like a baby Week 36: The baby is ready to be born Heredity Sexual reproduction involves fusion of gametes, which from a zygote The gametes contain chromosomes, which contain genes The sperm contains genes from the father, and egg from the mother. During fertilisation, the zygote will get genes from both parents. As a result, the baby will inherit characteristics from both parents. Definition: The process where characteristics are passed down genetically from one generation to the next. These characteristics are called hereditary characteristics. Example of characteristics DNA - Chromosomes contain DNA (deoxyribonucleic acid) molecules. - Each sequence of DNA containing genetic info is known as a gene - Genes contain instructions for making a human - These genetic info determines things like looks, intelligence, etc. Puberty Between the ages of 10-14, the human body starts to stimulate production of certain sex hormones It also produces a higher amount of growth hormone that leads to growth spurts Sex hormones changes the body and its function, in a period called puberty Definition: The period when an adolescent becomes capable of reproducing During puberty: - we become sexually mature and our body secretes hormones that attract us to the opposite sex - reproduction is now possible - sex and growth hormones change body systems (skeletal, muscular, etc.) Boys: Heavier bones and increase in muscle growth at the end of puberty Girls: Increase in fat tissues at the breasts, hips and pubic region at the end of puberty Changes during puberty Menstruation - when a female hits puberty, menstruation will start - menstruation marks the beginning of menstrual cycle in woman Definition: the discharge of the uterus tissues when an egg remains unfertilised There are 4 stages Stage 1: Menstruation ( Days 1-5: Standard ) First day of the menstrual cycle start with the menstrual flow Menstrual flow is the shedding of the unfertilised egg, uterine lining and blood Hormones determine how long the period will last (3 days, 5 days, a week, etc.) Stage 2: Repair and growth of uterine lining ( Days 6-13 ) The uterine lining thickens after menstruation Stage 3: Ovulation ( Days 14-16 ) A mature egg is released into the fallopian tube Ovulation will most likely occur in this time period Stage 4: Fertile period ( Days 14-28 ) Sexual intercourse around this period is likely to result in pregnancy Stage 5: Further thickening of uterine lining Remains thick to support the embryo with nutrients and oxygen for growth