Hormones and Reproduction

Sperm Development Sperm develop in the testes and mature and get stored in the epididymis. Sperm development begins at puberty and continues until death. A male has the potential to make up to 400,000,000 sperm each day.

Spermatogenesis 2n=46 human sex cell diploid (2n) n=23 meiosis I n=23 sperm haploid (n) meiosis II

Egg Development Each ovary contains 400,000 follicles-help eggs mature. 400,000 immature eggs – 400 released

Oogenesis 2n=46 human sex cell diploid (2n) n=23 meiosis I n=23 Polar body Polar Body Egg haploid (n) meiosis II

Menstrual Cycle Menstrual Cycle 28 day cycle Menstruation –lining of uterus sheds if no fertilization

4 PHASES Of Menstrual Cycle 1. Follicular Phase FSH and LH are released causing a follicle to matureFSH and LH are released causing a follicle to mature cells around egg produce estrogen- causes the lining of the uterus to thicken.cells around egg produce estrogen- causes the lining of the uterus to thicken.

2. Ovulation- occurs midway in cycle and lasts 3-4 days 2. Ovulation- occurs midway in cycle and lasts 3-4 days –sudden release of FSH and LH- ruptures follicle and egg is released into fallopian tube, one egg a month.

3. Luteal phase –egg moves through fallopian tube –Ruptured follicle turns yellow (corpus luteum) and releases progesterone- this increases the lining and blood supply. Endometrium

If no fertilization…. 4. Menstruation –if no fertilization or implantation of an egg, corpus luteum disintegrates. – thus no extra estrogen and progesterone released – lining sheds along with the egg.

Fertilization and Beyond Embryonic Development

Fertilization Semen is deposited in the vagina: –Semen is a combination of sperm and fluid. The sperm cells begin to travel: –Sperm travel from the cervix… –To the uterus… –To the fallopian tubes (oviduct). Fertilization takes place in the fallopian tubes.

Fertilization The sperm is attracted to a chemical made by the egg. There are millions of sperm cells: –Most don’t make it through the trip. –The sperm may only live for hours –The sperm surround the egg… The sperm cells secrete an enzyme. The enzyme loosens the cells around the egg. the egg.

Fertilization: Uniting the Sperm and the Egg The sperm go to work: –The sperm release enzymes to eat through the jelly layer on the egg. Once the egg is fertilized: –A new protective layer called the fertilization membrane is made. –This prevents any more sperm from entering.

Human Females Fertilization Occurs in Oviducts –Fallopian tubes (oviducts) transport ova (mature egg cells) from ovaries to uterus. Lined with a membrane (endometrium). Smooth muscles contract, moving egg down tube to uterus. –Takes 5-7 days to arrive at uterus.

Human Females Any egg that arrives at uterus unfertilized, can never become fertilized. –Lining of the uterus and egg are shed- menstruation. –If the egg is fertilized, the zygote continues down fallopian tube and attaches to endometrial lining.

Embryonic Development First major event in human embryonic development is rapid division of zygote called cleavage. –Overall size of embryo does not increase. Embryo reaches uterus and attaches to uterine lining.

Embryonic Development Embryo attaches to uterine lining and initiates membrane formation. –Amnion - Encloses embryo. –Chorion - Interacts with uterine tissue to form placenta for embryo nourishment. The placenta is also a means of eliminating CO2 and other wastes.

Embryonic Development Gastrulation –Ten days after fertilization, certain groups of cells move inward from surface of cell mass. Lower cell layer differentiates into endoderm, and upper layer into ectoderm. –Mesoderm arises by cell invagination.

Embryonic Development Neurulation –In third week, three primary cell types begin development into tissues and organs. Begins with notochord and dorsal nerve cord. –On either side of notochord, segmented blocks of tissue called somites form. Give rise to muscle, vertebrae, and connective tissues.

Fetal Development Fourth Week - Organ Development –Organogenesis. Most women not yet aware of pregnancy. –Fetal Alcohol Syndrome.

Fetal Development Second Month - Morphogenesis –Limbs assume adult shape. –Major organs become evident. –Embryo is about one inch in length.

Fetal Development Third Month - Completion of Development –Now referred to as fetus. Nervous system and sense organs develop. All major organs established. Second Trimester - Growth –Bone formation occurs. –Covered with fine hair (lanugo). –By the end of the sixth month, baby is one foot in length.

Fetal Development Third Trimester - Pace of Growth Accelerates –Weight of fetus more than doubles. –Most major nerve tracts formed within brain. –By end, fetus is able to survive on own. Postnatal Development –Babies typically double birth weight within a few months. –Neuron production occurs for six months.

Birth Oxytocin is released from the pituitary gland-stimulates contractions of uterus. Contractions become more powerful and force the baby down and out. After the baby is born, the placenta must also come out-the afterbirth.

Approaches to Contraception Abstinence –Rhythm Method Prevention of Egg Maturation –Birth-Control Pills Estrogen and Progesterone Prevention of Embryo Implantation –Intrauterine Devices

Approaches to Contraception Sperm Blockage –Condom –Diaphragm Sperm Destruction –Spermicidal jellies, suppositories, and foam