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Health Sciences
HSCI 100
Nienke Van Houten

Ch 17 – reproductive systems FUNCTIONS - produces gametes - transports gametes - produces sex hormones - nurtures & gives birth to offspring in females DNA in body cells + sex cells - body cells = somatic cells o Each body cell has 46 chromosomes, 23 pairs. mitosis only o cells have pairs of chromosomes = diploid 2N - sex cells = germ cells = gametes o Gametes have only 23 chromosomes (1 of each pair) in nuclei. meiosis o cells with 1 pair = haploid, 1N o during fertilization = zygote, diploid number of 46 = 2N SPERMATOGENESIS - process of making sperm in males - from meiosis, all 4 haploid cells generate sperm - continual process after puberty - about 400 mil produced/day OOGENESIS - process of making eggs in females - during meiosis,1 egg & 2-3 polar bodies formed - polar bodies hold discarded chromosomes and disintegrate - all eggs (400k) produced BY puberty - 1 egg per month released approx 400 in reproductive cycle MALE ANATOMY - seminal vesicle – pair of glands that produces fluid that nourishes sperm, thickens semen, assists movement of sperm once in female tract - prostate gland – produces alkine secretes that activate sperm + reduce acidity of reprod system - bulbourethral gland – produce mucous secretion before ejaculation neutralize acidic urine in urethra - epididymis – ducts which sperm store and mature - testis – pair of gonads that produce sperm + testosterone - urinary bladder - vas deferens – transport sperm from epididymis to urethra - urethra – tube transport semen during ejaculation, urine - erectile tissue of penis – spongy connective tissue fills with blood during sexual arousal - penis – organ of sexual intercourse that delivers sperm to female reprod tract - glans penis – region @ tip of penis rich in sensory nerves Scrotum - sacs holding testes - regulate temp of testes – 37C too warm and kills sperm Testes - pair organs produce sperm + male sex hormones - composed of seminiferous tubules where sperm produced continuously - sertoli cells – nourish sperm (provide niche) and regulate process of sperm production - leydig cells [interstitial cells] – btwn seminiferous tubules, produce male hormones (androgens - testosterone) epididymis - sperm mature + store here - typical ejaculation contains 100-500 mil sperm - survive for 48 hrs Mature sperm anatomy VAS DEFERENS & URETHRA - duct system o epididymis = receives sperm from seminiferous tubules, site of sperm maturation and storage o vas deferens = conducts sperm from epididymis to urethra o urethra = conducts urine from urinary bladder, sperm from vas deferens 3 glands contributing to semen - semen = fluid containing sperm + secretions of accessory glands, released through urethra @ sexual climax - 1. seminal vesicles o produce sugary fluid (fructose) = provides energy for sperm & prostaglandins that stimulate uterine contractions - 2. prostate gland o produce alkaline fluid to help buffer acidic pH in vagina o may enlarge with age & cuts off flow from urethra o most of the time = benign, readily cured - 3. bulbourethral glands o produce mucus that acts as a lubricant in the urethra Erection - mediated by mechanical stimulation through autonomic nervous system (parasympathetic) – release nitric oxide (NO) a gas - occur in response to visual, auditory, olfactory, tactile stimuli through cerebral cortex - erection takes place when smooth muscles of arteries relax thanks to action of cyclic guanosine monophosphate (cGMP) in cells - erectile tissue fills with blood & veins get compressed + blood returns slowly - Viagra blocks phophodiesterase that breaks down cGMP = prolongs HORMONE REGULATION IN MALES 1. gondatropin-releasing hormone (GnRH) – secreted by hypothalamus to control release of other hormones 2. follicle-stimulating hormone (FSH) – Promotes production of sperm, released by anterior pituitary - negative feedback loop of inhibin – declines testosterone (from seminiferous tubules in testes) o inhibits FSH secretion 3. luteinizing hormone (LH) – controls production of testosterone, released by anterior pit 4. testosterone – produced by interstitial (leydig) cells of gonad, important for dev + function of male reproductive organs (masculinzation) FEMALE ANATOMY - uterus – houses & nourishes developing baby until birth o inner layer = endometrium  smooth muscle of uterine wall contracts rhythmically in waves during childbirth  if embryo forms = implants in endometrium (which provides nourishment)  if embryo doesn’t form = endometrium completes cycle by being lost in menstrual flow  ectopic pregnancy (tubal pregnancy) – implantation in other than uterus = has to be removed or mother will bleed to death internally - uterine wall – muscle layers stretch and accommodate developing baby, contract during birth to deliver baby - endometrium – lining of uterus that is built up & lost each month (menstrual), usual site of implantation - cervix – opening of uterus extends into vagina - vagina – muscular tube receives penis during intercourse, birth canal - oviduct – ciliated tubes that conduct the egg/embryo toward uterus, usual site of fertilization o aka uterine/fallopian tube - ovary – produce eggs & sex hormones (Estrogen/progesterone) - clitoris – rich in sensory nerves (not actually part of genital tract) - labium minora – inner skin folds part of external genitalia (hood over clitoris) - labium majora – outer skin fold part of external genitalia THE OVARY Function: produce eggs (oogenesis) & produce hormones (estrogen /progesterone) - contains many follicles containing immature egg (oocyte) - puberty female has 300k-400k follicles, no more produced - ovulation – monthly release of an oocyte from ovary when follicle ruptures OVARIAN CYCLE - formation + release of immature egg - controlled by GnRH from hypothalamus - with menopause ovaries fail to respond to gonadotropic hormone FSH & estrogen production stops - 2 phases o 1) follicle maturation  Follicles continue to divide, fluid builds btwn them  Follicles split into 2 layers, inner lay surrounds primary oocyte, outer layer encloses fluid o 2) formation of mature follicle  10-14 days after development, follicle assumes mature form (secondary/graafian)  Meiosis – forms 2unequal… larger = secondary oocyte/tiny = polar body o 3) Ovulation  12 hrs after secondary oocyte form, mature follicle pops releasing oocyte mass  If sperm penetrates, meiosis advances  Mature ovum = egg (if fertilization completed) o 4) Formation of Corpus luteum  Outer sphere – LH transforms into endocrine structure = corpus luteum (yellow body)  Secretes estrogen/progesterone  If pregnancy doesn’t occur – corpus luteum degenerates  If pregnancy occurs – maintained by human chorionic gonadotropin UTERINE CYCLE (menstrual cycle) - 28 day cyclic event in uterus - Days 1-5: low level of estrogen and progesterone causing the inner uterine lining (endometrium) to disintegrate and menstruation occurs - Days 6-13 (proliferative phase): increase in estrogen causing the endometrium to thicken - Day 14: ovulation usually occurs/formation of corpus luteum (in ovary) - Days 15-28 (secretory phase): increase in progesterone causes endometrium to double or triple in thickness in preparation for the developing embryo. - Corpus luteum degenerations: If the egg is not fertilized, then the corpus luteum regresses and the endometrium breaks down - If the egg is fertilized, human chorionic gonadotropin (HCG) is made by the embryo and this maintains corpus luteum and endometrium (n.b. HCG is what pregnancy tests detect) OVARIAN CYCLE UTERINE CYCLE Day 1-13 Follicle develops, caused by Day 1 Onset of menstrual flow FSH (breakdown of Follicle cells produce endometrium) estrogen Day 14 Ovulation triggered by LH Day 6 Endometrium begins to get surge thicker Day 15-21 Corpus luteum forms & Day 15-23 Endometrium future secretes estrogen prepared for implantation progesterone of embryo by estrogen & progesterone Day 22-28 Corpus luteum degenerates, Day 24-28 Endometrium beings to causing estrogen & deg
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