Part 1: Reproductive anatomy and hormones Unit 5 Topic 4 Part 1: Reproductive anatomy and hormones

Seminal vesicle Urinary bladder Vas deferens Prostate gland urethra Bulbourethral gland epididymis Testes: male gonads, where sperm develop. Seminiferous tubules: coiled tubes inside the testes. Lots of surface area for sperm production. These are lined with the speratogonia (germ cells) from which primary spermatocytes are made. Epididymis: Coiled tubes adjacent to the testes in the scrotum. Sperm are stored here as they mature (grow a flagella and replicate mitochondria) Scrotum: Sac containing the testes and epididymis. This is separate from the abdominal cavity to keep the sperm cells at a lower temperature, necessary for production, approx. 35C (vs. 37C for normal body temp) Vas deferens: Ducts through which sperm leave each epididymis. Loop up into the abdominal cavity to merge with the seminal vesicles into the ejaculatory duct. Seminal vesicles: Gland that secretes a thick fluid containing fructose. Prostate gland: secretes an alkaline substance and a nutrient solution. Bulbourethral gland: secretes an alkaline mucus that neutralizes urine that remains in the urethra and the vaginal environment and lubricates the vaginal cavity. Urethra: duct through which urine and semen are excreted Penis: consists mainly of erectile tissue (glans and prepuce contain lots of nerve cells) Ejaculation: occurs in two stages. Stage 1 muscles surrounding the ducts contract, forcing all secretions and sperm into the urethra. A sphincter closes off the bladder. Stage 2 the penis fills with semen which is expelled via muscle contractions. Orgasm= rhythmic involuntary contraction of reproductive structures. testes scrotum

Hypothalamus Pituitary GnRH Pituitary LH FSH GnRH is made by the pituitary gland and stimulates the secretion of LH and FSH. FSH acts on the germ line cells of the testes, stimulating the formation of sperm. LH acts on the testes and stimulates the production of testosterone. Testosterone also stimulates sperm production in also regulates the process in a feedback loop. When testosterone reaches very high levels in the blood stream, the hypothalamus is inhibited in its ability to secrete GnRH. This is a negative feedback loop: when the products of a process slow down the process itself. LH stimulates release of testosterone FSH stimulates sperm production Testes

Female reproductive anatomy: side view B C D E F G H oviduct ovary uterus Urinary bladder rectum cervix urethra vagina Ovary: the ovaries are the reproductive organs of females. Each female has 2. This is where meiosis occurs to make gametes (eggs). Each month one of the ovaries releases a mature ovum. The ovaries are lined with follicles containing primary oocytes. The ovaries also make estrogen and progesterone. Oviduct: This connects to the uterus and is adjacent to but does not touch the ovary. There are two, one on each side. The inside is lined with cilia to move the egg towards the uterus. Fertilization takes place in the first third of the oviduct. Uterus: this is also called the womb. It is where the embryo and fetus develop.. It is a cavity. It is usually only 3 inches long and very narrow. It expands with the growing fetus. Endometrial lining: This is the thick muscular lining of the uterus. There are lots of blood vessels in the walls. The embryo implants into this when it gets into the uterus. Cervix: this is the narrow opening between the uterus to the vagina. It is usually blocked with mucus. During birth, surround muscles contract to open it. Vagina: this is the birth canal and sperm repository. Protected by folds of skin collectively called labia. Urethra: this is the tube through which urine is excreted. It is separate from all the reproductive ducts.

Female reproductive anatomy G F B C H I J K oviduct ovaries fimbriae follicles Corpus luteum uterus Endometrial lining Follicle: Spherical cluster of cells enclosing a secondary oocyte. It protects and nourishes the developing egg. Every 28 a follicle matures and releases its egg. 400,000 of these line each ovary. Corpus luteum: when a follicle releases an egg, if that egg is fertilized, the follicle becomes a corpus luteum…this structure produces the hormones estrogen and progesterone to maintain the uterine lining until the embryo implants. Fimbriae: These are projections of tissues are activated by hormones during ovulation. They have cillia which sweep the egg into the oviduct from the peritoneal cavity. Endometrial lining: also called the uterine lining. This is the inner lining of the uterus. It cyclically builds up tissue layers to cushion and nourish an embryo. If no embryo implants each cycle, the innermost layers of this lining (the ones adjacent to the cavity) are shed (menstruation). Clitoris: function is arousal. Consists of erectile tissues. Stimulates the secretion of mucus for lubrication of the vaginal canal. cervix vagina

What's happening in the ovaries? Follicle stimulating hormone (FSH) After birth: primary oocytes are arrested in prophase I. After puberty: 1 follicle per month matures. The follicle that matures is random…whichever is activated first by follicle stimulating hormone, FSH. The follicle and maturing egg grow bigger. Meiosis 1 is completed and meiosis 2 starts and pauses in metaphase II. Maturation within the ovary takes 10-14 days. When the level of luteinizing hormone peaks (day 14 of cycle) the egg is released by the follicle. This is called ovulation. If the egg is fertilized, the follicle becomes the corpus luteum and begins to release estrogen and progesterone, which maintain the endometrial lining. Luteinizing hormone (LH)

Comparison of hormone levels during a 28-day menstrual cycle

____________ levels of estrogen and ____________ Triggers Release of FSH and ____. _________ and ________ levels drop. Triggers Secondary oocyte maturation in ______ Follicle releases _________ Promotes ___________thickens LH spike around day ___ ______ bursts and releases _____ Rupture follicle becomes __________ Releases Estrogen and _______________ Inhibits Promotes ________ and ________ production The _________ thickens more If fertilization occurs, corpus luteum continues to make ______________ If no fertilization, __________ degenerates

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