REPRODUCTION 10 CMH HUMAN AND SOCIAL BIOLOGY Created by : Reynaldo Thomas

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.

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 joint during fertilization. Fusion of the gametes forms a single cell called zygote.

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

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

The ovary Where egg cells are produce. Where egg cells are produce. Site for oestrogen production. Site for oestrogen production. About ten thousands ova are present at birth. About ten thousands ova are present at birth. Only about 400 will develop fully (1 per month/14 to 45). Only about 400 will develop fully (1 per month/14 to 45). Ova develop inside follicles. Ova develop inside follicles. Mature follicle is called graafian Mature follicle is called graafian follicle. follicle. When ripe it moves to ovary’s When ripe it moves to ovary’s surface. 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. This occurs in the oviduct. About 3-5 cm 3 of semen expelled from penis About 3-5 cm 3 of semen expelled from penis Contains between 180 and 500 million spermatozoa. 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.acrosome 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.corpus luteum 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. 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. There is no joining of the maternal and fetal red blood cells.maternal A thin layer of cells A thin layer of cells acts as a barrier, acts as a barrier, separating maternal separating maternal and fetal red blood and fetal red blood cells. cells.

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

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

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.nine months

The birth Process Stage one The uterus muscles start to contract to start the labour process. The uterus muscles start to contract to start the labour process. Baby stimulates the release of Baby stimulates the release of the hormone oxytocin. the hormone oxytocin. Rhythmic contractions of the Rhythmic contractions of the uterus cause amnion to break. uterus cause amnion to break. The fluid will now pass out. 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 from the navel on the abdomen. The placenta and membranes are shed from the mother and are called the afterbirth.