REPRODUCTION 10 CMH Integrated Science

What is Reproduction? The process by which new organisms are generated. There are two means of reproducing: asexual and sexual reproduction.

Asexual Reproduction Does not involve the fusion of sex cells. Parts of the parents form the offspring. Only one parent is needed. Advantages Reproduce in large amount very quickly. No need to search for a mate. Desirable characteristics can be artificially bred into a population.

Farmers can now produce high-yield or disease – resistant crops and livestock. Disadvantages All the offspring are clones. A poor quality parent will produce poor quality offspring. There is a lack of variation.

Sexual Reproduction Requires a male and a female. Male sex cell is called sperm and female the egg(ovum). The two sex cells must join during fertilization. Fusion of the gametes forms a single cell called zygote.

Advantages of Sexual Reproduction Offspring are different both from each other and to parents. It produces variation in the offspring so organisms gradually change or evolve. There will always be a proportion of organisms which can survive unfavourable changes, so the population is less likely to die out.

Disadvantages of Sexual Reproduction Mating partners must be available. Fewer offspring are produced.

Movement of Sperm During ejaculation, the sperm cells leave the epididymis and flow through the vas deferens towards the penis. The epididymis passes through the prostate gland and seminal vesicles. These structures bathe the sperm cells with seminal fluids. This mixer is called semen.

Structure of the Sperm The head is where the nucleus is. Tip of head contains a small sac called the acrosome. Acrosome contains hydrolytic enzymes. This is responsible for burrowing through egg during fertilization. The neck area contains lots of mitochondria.

Mitochondria generate energy. The tail allows sperm cell to swim through vagina and uterus.

Female Reproductive System Make the female gametes (egg cells) Receive the sperm cells from male for fertilization. Maintain an environment suitable the implantation of an embryo. Provide everything needed for the develop- ment of foetus. Deliver baby to the outside world.

Female Reproductive System the parts of the female reproductive system are located in the pelvic region. Vagina the entrance to the inner parts It is a muscular channel Receives penis at copulation Passage for baby at birth

The ovary Where egg cells are produce. Site for oestrogen production. About ten thousands ova are present at birth. Only about 400 will develop fully (1 per month/14 to 45). Ova develop inside follicles. Mature follicle is called graafian follicle. When ripe it moves to ovary’s surface.

Egg live for 3-4 days after ovulation It move along the oviduct by the beating of cilia.

Fertilizations The fusion of a sperm with an ovum. This occurs in the oviduct. About 3-5 cm3 of semen expelled from penis Contains between 180 and 500 million spermatozoa.

Spermatozoa swim up the oviduct. Sperm enter head first, losing its tail as it does so. The acrosome produce enzymes which help penetrate the ovum. Only one sperm can enter the ovum. The resulting zygote has contents of both male and female nuclei ,which is fuse.

Implantation The corpus luteum continues to produce progesterone. Progesterone prepares the uterus wall for the zygote. Uterus wall thickens. Zygote now divides into a ball of cells and stick into the wall of the uterus.

Pregnancy The thick wall of uterus is called the placenta It has rich blood supply stimulated by oestrogen and progesterone.

The placenta is formed mainly from the embryo and partly from the mother’s tissue. There is no joining of the maternal and fetal red blood cells. A thin layer of cells acts as a barrier, separating maternal and fetal red blood cells.

Nicotine, alcohol and other drugs and pathogens do pass across the placenta to cause harm. Nutrients and oxygen diffuse from maternal blood capillaries to embryo. Carbon dioxide and other waste materials diffuse from the embryo to mother.

Umbilical cord Carries nutrients in veins to fetus and waste in artery from fetus. The cord runs from the embryo’s abdomen to the placenta. Amnion A sac of water. Membrane enclosing fluid, protecting fetus from shock and allowing movement. The water distributes pressure evenly around fetus.

N. B A fetus moves its limbs from the age of about 16 weeks onwards N.B A fetus moves its limbs from the age of about 16 weeks onwards. After two months, the human form of the fetus is recognizable. At three months the sex can be seen. Birth follows about nine months after fertilization (37-40) wks.

The birth Process Stage one The uterus muscles start to contract to start the labour process. Baby stimulates the release of the hormone oxytocin. Rhythmic contractions of the uterus cause amnion to break. The fluid will now pass out.

Stage two Increasing contractions of the uterine muscle push the baby through the cervix and then the vagina.

Stage 3 Finally the baby is expelled head first The mother bending forward Holding her breath, aids this, to push the diaphragm on top of the uterus.

After Birth The umbilical cord is cut and tied so that the remains form the navel on the abdomen. The placenta and membranes are shed from the mother and are called the afterbirth.

Medical Abortion Surgery The lining of the uterus, including the embryo is removed by suction The uterus lining can also be scrap away

Drugs Drags can be use, which kill the embryo and make her go into labour. She gives birth to the dead embryo.

Disadvantages of abortion High risk of blood loss during the surgical procedure. Surgery can cause diversion of blood flow to different organs.

Disadvantages of abortion Increases risk of developing depression, guilty feeling and anxiety. Medical instruments may cause uterus injury and infection.

Reasons for abortion The woman is not healthy enough to carry a healthy baby and give birth to it. Woman feels that she will not be able to look after and support the baby. Woman may not want her family or friend to know that she has become pregnant. Getting pregnant was an accident.

What is cancer? This is the uncontrolled growth of the cells in the human body and the ability of these cells to migrate from the original site and spread to distant sites.

Disorders of the female reproductive system Ovarian cancer Begins in the ovaries. More common in women over 50. Very hard to detect early. There is no or just mild symptoms until it is in an advanced stage and difficult to treat.

Signs and symptoms Heavy feeling in pelvis. Pain in lower abdomen. Weight gain or loss. Abnormal periods. Unexplained back pain that gets worse. Gas, vomiting or loss of appetite.

Treatment Chemotherapy This is when medicines are used to destroy cancer cells and can cause side- effects, including tiredness and feeling sick or vomiting.

Radiotherapy This is when radiation is used to destroy cancer cells.

Cervical cancer Can be detected at an early stage by cervical smears. Causes Should be taken by those most at risk, such as: Women who have sex with many partners.

Start having sex at a early age. Have been infected with sexually transmitted disease. Cause by a virus (human papilloma virus, HPV) that is sexually transmitted. Using birth control pills for 5 or more years.

Symptoms irregular vaginal bleeding. vaginal discharge with an unpleasant odor. watery vaginal discharge. vaginal discharge tinged with blood. pelvic or back pain.

What is breast cancer? Breast cancer is a malignant tumor that starts in the cells of the breast. A malignant tumor is a group of cancer cells that can grow into (invade) surrounding tissues or spread to distant areas of the body. Symptoms A lump in the breast or underarm that persists after your menstrual cycle. Swelling in the armpit Pain or tenderness in the breast.

A noticeable flattening or indentation on the breast. Any change in the size, contour, texture, or temperature of the breast. Unusual discharge from the nipple that may be clear, bloody, or another color

Prostate Cancer When cancerous cells begins to develop in the prostate. Usually occurs in older men. Diet is a contributing factor in reducing the risk of prostate cancer.

What are the symptoms of prostate cancer? The patient urinates more often The patient gets up at night more often to urinate He may find it hard to start urinating He may find it hard to keep urinating once he has started There may be blood in the urine Urination might be painful Ejaculation may be painful Achieving or maintaining an erection may be difficult 

Menstruation At puberty (12 to 13) a girl begins what is called her menstrual cycle. About every 28 days, blood and other particles from the uterus lining are expelled out. Usually over over 4 to 5 days.

Ovulation A woman born with all of the sex cells she will ever make. The eggs are in an immature state. A follicle in one of the ovaries begins to develop or mature. After menstruation the follicle mature and releases oestrogen.

Oestrogen causes the uterus lining to become thicker, containing a lot of blood and blood vessels. This is called endometrium. Its purpose is to provide an environment that will sustain the growing fetus.

This continues for about 2 weeks. The hormone luteinising (LH), then triggers the release of a mature egg from the follicle.

Breast Feeding During pregnancy the mammary glands enlarge. It get prepared to secrete milk. Shortly after birth the baby will suck at the nipples.