Lesson 1: Reproductive Systems

Male reproductive system

Further functions Urethra: tube from ejaculatory duct through penis that carries semen and urine (but not at the same time) Urethra: tube from ejaculatory duct through penis that carries semen and urine (but not at the same time) Prostate: also neutralizes acidity of vagina Prostate: also neutralizes acidity of vagina Bulbourethral gland: also “cleans out” urethra, releases fluid before ejaculation, contributes to unplanned pregnancies Bulbourethral gland: also “cleans out” urethra, releases fluid before ejaculation, contributes to unplanned pregnancies Sperm make only a small part of semen; 90+% of volume from seminal vesicles Sperm make only a small part of semen; 90+% of volume from seminal vesicles

1. Mitosis makes enough cells from spermatogonium to keep the same number and produce sperm 2. Primary spermatocytes grow 3. Cells divide through the two divisions of meiosis (secondary spermatocytes) 4. Cells (spermatids) differentiate as they develop Sertoli cells support developing sperm. (germinal epithelium)

(spermatozoa) (produce testosterone) (nurse cell)

Structure of a Mature Sperm (50 um) Acrosome: chemicals to enter egg Acrosome: chemicals to enter egg Nucleus: haploid Nucleus: haploid Midpiece: “motor”, many mitochondria Midpiece: “motor”, many mitochondria Flagellum: protein, 9+2 microtubule pattern Flagellum: protein, 9+2 microtubule pattern Flagellum ~40 um Flagellum ~40 um

Hormonal Control of Spermatogenesis  Luteinizing hormone (LH): increases testosterone levels  Follicle Stimulating hormone (FSH): controls meiosis / number of sperm  Testosterone: helps sperm production and development * FSH and LH named for role in females (menstrual cycle)

Secondary sexual characteristics  Related to sexual development, but not necessary for reproduction  Development occurs during puberty

Roles of Testosterone in Males  Gonads become either testes or ovaries (ovary is default)  Gene on Y chromosome (when fetus is in week 7) shifts gonads to testes  Testes release testosterone  Testosterone leads to  development of secondary sexual characteristics at puberty  Production of sperm  Maintenance of sex drive

Timing and Number of Sperm Production  Begins at puberty, continues until death  Continually produced, millions each day  Complete process takes several months  One diploid cell produces 4 haploid sperm with equal amounts of cytoplasm  May be released voluntarily

Ureter 2.Urinary bladder 3.Seminal vesicle 4.Prostate 5.Bulbourethral gland 6.Vas deferens (ductus deferens) 7.Epididymis 8.Scrotum 9.Testes 10.Urethra 11.Penis

(holds fetus in uterus) (site of fertilization) (for urination)

All follicles present at birth (one primary oocyte each) All follicles present at birth (one primary oocyte each) Follicle stimulating hormone (FSH) causes some follicles to develop; usually one per month will mature Follicle stimulating hormone (FSH) causes some follicles to develop; usually one per month will mature The follicle stays in the same place in the ovary The follicle stays in the same place in the ovary The mature, large, fluid- filled follicle seen before ovulation is called a Graafian follicle. The mature, large, fluid- filled follicle seen before ovulation is called a Graafian follicle. After ovulation, the follicle becomes the corpus luteum After ovulation, the follicle becomes the corpus luteum Mature (Graafian) follicle

unequal division of cytoplasm

A secondary oocyte is released to the fallopian tubes (oviduct) in ovulation A secondary oocyte is released to the fallopian tubes (oviduct) in ovulation When triggered by the arrival of a sperm, meiosis will finally be completed, releasing the second polar body. When triggered by the arrival of a sperm, meiosis will finally be completed, releasing the second polar body. (also called yolk, contains lipid droplets) (and centrioles) for first Haploid DNA in metaphase II

Estrogen and progesterone are major female hormones. They cause Estrogen and progesterone are major female hormones. They cause Pre-natal (embryonic/fetal) development of female sex organs Pre-natal (embryonic/fetal) development of female sex organs Development of secondary sexual characteristic during puberty Development of secondary sexual characteristic during puberty

Timing and Number of Ova Production All eggs begin meiosis during fetal development All eggs begin meiosis during fetal development At puberty, ~1 egg / month continues meiosis, release time hormonally controlled (menstrual cycle) At puberty, ~1 egg / month continues meiosis, release time hormonally controlled (menstrual cycle) Meiosis only completed if sperm enters egg Meiosis only completed if sperm enters egg Unequal division of cytoplasm; one diploid cell produces one ovum and 2-3 polar bodies Unequal division of cytoplasm; one diploid cell produces one ovum and 2-3 polar bodies Compare oogenesis and spermatogenesis.

Spermatogenesis v. Oogenesis In testes In testes Millions produced continually (after puberty); released as needed / voluntary control Millions produced continually (after puberty); released as needed / voluntary control Four motile sperm produced per meiosis (equal cytoplasm) Four motile sperm produced per meiosis (equal cytoplasm) Meiosis begins (primarily) in puberty Meiosis begins (primarily) in puberty Sperm made indefinitely Sperm made indefinitely Requires testosterone and Sertoli (nurse) cells Requires testosterone and Sertoli (nurse) cells In ovaries In ovaries One oocyte released per month long cycle, hormonal control One oocyte released per month long cycle, hormonal control One egg per meiosis (+2-3 small polar bodies) with unequal division of cytoplasm One egg per meiosis (+2-3 small polar bodies) with unequal division of cytoplasm Meiosis begins during fetal stage, none in childhood, completed after puberty (when sperm present) Meiosis begins during fetal stage, none in childhood, completed after puberty (when sperm present) Viable egg supply gone by menopause Viable egg supply gone by menopause Similarities include: mitosis in germ cells, cell growth before meiosis, two divisions of meiosis, haploid nuclei, need for LH and FSH, etc.

1.Uterus 2.Fallopian tube (oviduct) 3.(Fimbriae) 4.Ligament 5.Cervix 6.Vagina 7.Endometrium 8.Ovary 9.Urinary bladder 10.Urethra 11.Pelvic bone 12.Clitoris 13.Labia 14.Urethral orifice 15.Intestine 16.Anus