Human Reproduction

Reproductive System The function of the reproduction system is to make new members of the species.The function of the reproduction system is to make new members of the species. –Individual can lead a healthy life without reproducing BUT… –Reproduction is single most important system for continuation of a species –(without it no species could produce another generation)

Puberty Puberty is period of rapid growth and sexual maturationPuberty is period of rapid growth and sexual maturation –Reproductive system becomes fully functional –At end of puberty, male and female reproductive organs are fully developed –Varies in age from 9-15 (females usually 1 year earlier than males)

Puberty Begins when hypothalamus signals pituitary gland to produce increased levels of two hormones that affect gonadsBegins when hypothalamus signals pituitary gland to produce increased levels of two hormones that affect gonads *follicle stimulating hormone (FSH) *luteinizing hormone (LH)

Male Reproductive System Main function is to produce and deliver spermMain function is to produce and deliver sperm –Release of FSH and LH stimulates cells in testes to produce testosterone –Testosterone stimulates the development of sperm –Once large numbers of sperm are produced in testes  puberty is complete = functional reproductive system

Structures of Male Reproductive System Scrotum-an external sac which holds the testesScrotum-an external sac which holds the testes –Temp is 1-3 degrees cooler than normal body temperature (lower temp is important for proper sperm development) Seminiferous tubules- one of hundreds of tiny tubules in the testes in which sperm is producedSeminiferous tubules- one of hundreds of tiny tubules in the testes in which sperm is produced

Gametes A Gamete is a cell which is used during sexual reproductionA Gamete is a cell which is used during sexual reproduction Gametes are usually either sperm or egg cells.Gametes are usually either sperm or egg cells. Gametes have HALF the number of chromosomes as normal cells.Gametes have HALF the number of chromosomes as normal cells. When gametes are created, they don’t undergo mitosis, they undergo…When gametes are created, they don’t undergo mitosis, they undergo… MEISOSIS!MEISOSIS!

Meiosis Meiosis is the process of cell division where an normal cell ends up as four cells with half the original number of chromosomes.Meiosis is the process of cell division where an normal cell ends up as four cells with half the original number of chromosomes. If a cell has 4 chromosomes to start with, at the end of meiosis, its four daughter cells would have 2 chromosomes.If a cell has 4 chromosomes to start with, at the end of meiosis, its four daughter cells would have 2 chromosomes.

Meiosis vs. Mitosis

Structures of Male Reproductive System Sperm cellSperm cell –Consists of: Head (highly condensed nucleus) Midpiece (packed with energy releasing mitochondria) Tail aka flagellum (propels cell forward) At tip of head is small cap that contains enzyme vital to fertilization

Structures of Male Reproductive System Epididymis-structure in which sperm fully mature and are storedEpididymis-structure in which sperm fully mature and are stored Vas deferens- tube from the epididymisVas deferens- tube from the epididymis –Extends upward from scrotum into abdominal cavity Urethra- merges with the vas deferensUrethra- merges with the vas deferens –Tube that leads to the outside of the body thru the penis

Structures of Male Reproductive System Seminal fluid- nutrient rich fluid which nourishes the sperm and protects them from the acidity of the female reproductive tractSeminal fluid- nutrient rich fluid which nourishes the sperm and protects them from the acidity of the female reproductive tract Semen- combination of sperm and seminal fluidSemen- combination of sperm and seminal fluid –Between million sperm present in 1mL of semen –(about 2.5 million sperm per drop)

Male Reproductive System Ejaculation- sperm are ejected from penis by smooth muscle contractionsEjaculation- sperm are ejected from penis by smooth muscle contractions –Regulated by autonomic nervous system= not completely voluntary –About 2-6mL of semen released

Female Reproductive System Primary organs are ovaries (located in abdominal cavity)Primary organs are ovaries (located in abdominal cavity) Puberty starts when hypothalamus signals pituitary gland to release FSH and LHPuberty starts when hypothalamus signals pituitary gland to release FSH and LH –FSH stimulates cells within ovaries to produce estrogen

Female Reproductive System Main function of female reproductive system is to produce ova or egg cellsMain function of female reproductive system is to produce ova or egg cells –Also prepares female’s body to nourish developing embryo –Ovaries only produce one mature ovum (egg) each month

Egg Development Follicle is cluster of cells surrounding single eggFollicle is cluster of cells surrounding single egg About 400,000 primary follicles in each ovaryAbout 400,000 primary follicles in each ovary Function of follicle is to help the egg mature for release into reproductive tract where it can be fertilizedFunction of follicle is to help the egg mature for release into reproductive tract where it can be fertilized Every 28 days follicle gets larger and completes first meiotic cell divisionEvery 28 days follicle gets larger and completes first meiotic cell division

Egg Development When meiosis is complete, single large haploid egg and 3 smaller cells called polar bodies are produced (very little cytoplasm and soon disintegrate)When meiosis is complete, single large haploid egg and 3 smaller cells called polar bodies are produced (very little cytoplasm and soon disintegrate)

Egg Release

Ovulation is process in which egg is released from ovaryOvulation is process in which egg is released from ovary Fallopian tubes are fluid filled tubes connected to ovary, egg moves thru by push of microscopic ciliaFallopian tubes are fluid filled tubes connected to ovary, egg moves thru by push of microscopic cilia Egg can be fertilized at this pointEgg can be fertilized at this point After a few days, egg passes into uterusAfter a few days, egg passes into uterus –Lining of uterus is ready to receive fertilized egg (if fertilization occurred)

Structures of Female Reproductive System Cervix is outer end of uterusCervix is outer end of uterus Vagina is canal beyond the cervix that leads to the outside of the bodyVagina is canal beyond the cervix that leads to the outside of the body

Menstrual Cycle Begins at puberty and continues until mid 40’sBegins at puberty and continues until mid 40’s Permanent stopping of menstrual cycle called menopause (50’s)Permanent stopping of menstrual cycle called menopause (50’s) During menstrual cycle, egg develops and is released from ovary and uterus is prepared to receive fertilized eggDuring menstrual cycle, egg develops and is released from ovary and uterus is prepared to receive fertilized egg If egg is not fertilized, then egg is discharged along with the lining of the uterusIf egg is not fertilized, then egg is discharged along with the lining of the uterus

Phases of the Menstrual Cycle 1.Follicular phase 2.Ovulation 3.Corpus luteum phase 4.Menstruation

Phases of Menstrual Cycle Follicular phaseFollicular phase days days FSH from pituitary stimulates maturation of FSH from pituitary stimulates maturation of egg in follicle Estrogen from follicle stimulates thickening of uterine lining Estrogen from follicle stimulates thickening of uterine lining

Phases of Menstrual Cycle OvulationOvulation mature egg released from follicle FSH production inhibited by estrogen, which stimulates release of LH bypituitary

Phases of Menstrual Cycle Corpus Luteum phaseCorpus Luteum phase days burst follicle develops into corpus luteum, whichproduces progesterone progesterone stimulates further thickening of uterine lining

Phases of Menstrual Cycle MenstruationMenstruation If egg is not fertilized, progesterone secretion decreases Uterine lining degenerates Tissue and blood are discharged from body

Sexually Transmitted Diseases Spread by sexual contactSpread by sexual contact Serious health problem in USSerious health problem in US Most commonly reported STD is chlamydia (more than 3 million cases/year)Most commonly reported STD is chlamydia (more than 3 million cases/year) –Bacteria –Females show highest incidence of infection –Puts them at risk for infertility due to damage caused to reproductive system

STD’s Other bacterial STD’s include syphilis (can be fatal) and gonorrheaOther bacterial STD’s include syphilis (can be fatal) and gonorrhea Viruses include hepatitis B, genital herpes, genital warts, HIVViruses include hepatitis B, genital herpes, genital warts, HIV Can be prevented by abstinence from sexual contact (100% effective!!!)Can be prevented by abstinence from sexual contact (100% effective!!!) Next safest option is to use a condom (every time!!!!!)Next safest option is to use a condom (every time!!!!!)