Human Reproductive System Section 8.5 in Biology 12 textbook

Sexual Reproduction Cons: High energy cost Takes a long time Requires 2 individuals of the same species Can be difficult to find a mate! Exchange of body fluids – risk of transmitting bacteria & viruses So… why do we do it?

Sexual Reproduction Pros: Offspring are genetically unique – more likely to survive Genes can be combined in many different ways Humans seem to like it…

Basic process: Requires 2 gametes, one from the male, one from the female Produced during meiosis Sperm & ovum (egg) Production of a new individual: sperm fuses with ovum Fertilization: nucleus of the sperm passes into the egg & the 2 nuclei fuse

2 nuclei: haploid + haploid = diploid Cell divides by mitosis  zygote  embryo fetus

In order for sperm to meet ovum, mating has to take place Mammals – sperm from the male is injected into the female Sensory stimulus produces a reflex which results in the ejaculation of semen (sperm + fluids) into the vagina

Male Reproductive System

Male Reproductive System Vas deferens Seminal vesicle Urethra Penis Prostate Gland Epididymis Testis Cowper’s Gland Seminiferous Tubules: not pictured, inside testes

Male Sex Hormones (Androgens) Testosterone (& androsterone – less of this) Produced in the testes Stimulates spermatogenesis Responsible for secondary male sex characteristics at puberty Maturation of testes & penis Male sex drive Facial & body hair Growth of the larynx (Adam’s Apple) – deep voice Strengthening of muscles Increased oil production (causes acne)

Negative Feedback Control Production of testosterone & sperm controlled by hypothalamus & pituitary Beginning at puberty (12~14 years old) Hormones involved: Gonadotropin-releasing hormone (GnRH) From the hypothalamus – stimulates pituitary Follicle-stimulating hormone (FSH) From the pituitary gland – stimulates sperm production Luteinizing hormone (LH) From the pituitary – stimulates testosterone production

Female Reproductive System

Female Reproductive System Fallopian Tube Ovary Fimbria Uterus Cervix Vagina

Ovaries Contain connective tissue & follicles (small groups of cells) Follicles are either: primary oocytes (undergo meiosis) OR: granulosa cells (provide nutrients for oocyte) Under constant decline (review – from meiosis ppt)

Ovulation At the end of meiosis I – secondary oocyte Bursts through ovary wall & is released into the fallopian tube (oviduct) Swept along by fimbria Opening becomes a yellow mass of cells called the corpus luteum Secretes hormones in the event of pregnancy Meiosis II happens in the oviduct Polar bodies deteriorate

Menstrual Cycle ~28 days in length 4 phases Flow phase Follicular phase Ovulatory phase Luteal phase

Flow Phase Shedding of the endometrium Known as “menstruation” Externally visible Used to mark the beginning of the cycle ~5 days in length

Follicular Phase Development of follicles in the ovary Ovaries secrete estrogen Estrogen levels increase throughout phase Day 6 – 13 ~8 days in length

Ovulatory phase Ovulation happens Short – characterized by the release of the egg from the ovary Day 14

Luteal Phase Development of the corpus luteum Estrogen levels drop during ovulation Corpus luteum restores levels Releases estrogen & progesterone Progesterone – builds up the endometrium Lining of the uterus (prepare for pregnancy) Inhibits additional ovulation Prevents uterine contractions Days 15-28 ~14 days in length

If no fertilization… Estrogen & progesterone levels drop Uterus contracts Endometrium pulls away from wall of the uterus Shed from the body Cycle starts again

Negative Feedback Control Production of estrogen & progesterone controlled by hypothalamus & pituitary Begins at puberty GnRH from hypothalamus stimulates pituitary During follicular phase: FSH is released & stimulates development of follicles Follicles secrete estrogen which builds the endometrium Increased release of estrogen causes the pituitary to stop releasing FSH

Negative Feedback Control Increase in estrogen causes an increase in release of LH (+ feedback) Stimulates ovulation Corpus luteum forms Secretes estrogen & progesterone Inhibit the release of FSH & LH Corpus luteum deteriorates, stops producing estrogen & progesterone

Homework Questions Page 399 #1-11 Lab exercise 8.5.1, page 404-405