Reproductive System Flashcards
Testes
- contained within scrotum
- produce sperm and male sex hormones
- contain 250m of seminiferous tubules and interstitial cells
Seminiferous Tubules
- tightly coiled tubules in testes
- spermatogenesis occurs here
- contain Sertoli cells
Interstitial Cells
- lie between seminiferous tubules
- secrete male sex hormones (androgens)
epididymis
- tightly coiled duct lying just outside each teste
- for maturation of sperm cells
- 4.5m long
- if not ejaculated, sperm are reabsorbed after 60 days
ductus/vas deferens
- connect epididymis to urethra
- store and conduct sperm to urethra just prior to ejaculation
seminal vesicles (accessory gland)
- add to seminal fluid/semen via duct joining vas deferens
- basic fluid of 7.5 neutralizes vaginal acidity
- contain fructose (sperm energy source) and prostaglandins
prostate gland (accessory gland)
- donut-shaped, surrounds urethra at base of bladder
- secretions neutralize vaginal acidity and help make sperm motile
- in older men, prostate may enlarge and pinch off urethra, making urination difficult
- older men also require prostate check-ups to detect prostate cancer
Cowper’s/bulbourethral gland
- pea-sized, lie beneath prostate on either side of urethra
- fluid helps neutralize acidity of remaining urine in urethra
- provides mucus for lubrication within urethra for sperm to swim through and flushes out urea
Urethra
combined passageway for sperm and urine
Penis
- male organ of copulation
- consists of erectile tissue
- erection initiated by sympathetic nervous system, orgasm by parasympathetic
Pathway of sperm
epididymus -> ductus deferens -> urethra
*accessory glands contribute secretions to seminal fluid
Acrosome
- cap on head of sperm, has enzymes
- more than 1 sperm must contribute enzymes to get through protective layer of egg
Head
contains 23 chromosomes (haploid)
Midpiece
has mitochondria for energy for “swimming”
Tail/flagella
provides locomotion/”swimming”
Scrotum
- contains testes
- helps regulate temperature by raising/lowering testes (sperm production needs lower than body temp.)
Spermatogenesis
Sperm production
Sertoli cells
Support, nourish, and regulate developing sperm cells
Prostaglandins
Hormones that create uterine contractions to help propel sperm to egg
Ovaries
- female gonads, oogenesis occurs here
- females are born w/2 million follicles, each with an immature egg -> 300-400 thousand still viable at puberty -> only 400 mature during reproductive year
- r & l ovaries alternate releasing 1 egg/month (ovulation)
oviducts/fallopian tubes
- from uterus to ovaries
- fimbriae help sweep egg into oviduct
- egg moves to uterus via cilia & muscle contractions
- egg lives 6-24 hours -> fertilization usually occurs in oviduct
Fimbriae
- fingerlike projections at end of oviducts
- sweep egg from ovary into oviduct
Uterus/womb
- above bladder
- lining is called endometrium (where fetus implants)
- implantation and fetal development occur here
cervix
muscular opening to uterus
vagina
- cervix to external body surface
- serves as birth canal, copulatory organ, and exit for menstrual flow
- folded lining can extend to facilitate birth
clitoris
- role in female orgasm
- analogous to gland on end of penis
the egg
- 100 micrometers in diamater
- must be fertilized within 24 hours of release to survive
- granulosa cells surround egg & provide steroids & other growth factors
- zona pellucida = layer enzymes from acrosome eat through
testosterone
- male hormone
- causes sex organs to grow & mature at puberty
- promotes sperm production & maturation
- development of secondary sexy characteristics (ie. hair, deeper voice, libido/sex drive)
- increases metabolism by 15-20%
gonadotrophic-releasing hormone (GnRH)
- male hormone
- used by hypothalamus to control testes
- stimulates ant. pituitary to produce LH and FSH
- controlled by negative feedback system
lutenizing hormone (LH) in males vs. females
- males: produces testosterone in interstitial cells
- females: guides cycle of ovulation
follicle-stimulating hormone (FSH) in males vs. females
- males: spermatogenesis in seminiferous tubules
- females: guides cycle of ovulation
estrogen
- female hormone
- causes development of female genitalia
- increases thickening of endometrium
- increases water retention
- causes uterus to contract & help sperm along
- develops secondary sex characteristics (ie. broadening hips, breast development, adipose/fat tissue increase)
- causes ant. pituitary to release LH
progesterone
- female hormone
- development of endometrium in uterus
- maintains lining in preparation for pregnancy
ovarian cycle
- results in ovulation
- caused by variation in hormone levels
- average cycle length = 28 days
- follicular phase, ovulation, luteal phase
day 1-13: follicular phase
- low levels of estrogen & progesterone stimulate GNRH release by hypothalamus
- causes ant. pituitary to release FSH & LH
- FSH causes development of Graafian Follicle, which produces estrogen
- egg maturation causes small amounts of progesterone & lots of estrogen
Graafian Follicle
- development triggered by FSH
- cellular bag containing egg in ovary
Day 14: ovulation (ovarian cycle)
- estrogen levels peak causing ant. pit. to release LH
- LH causes Graafian follicle to burst, releasing egg
- fimbriae guide it into oviduct
Day 15-28: luteal phase
- LH continues to effect Graaf. foll. & changes it to corpus luteum
- this produces large amounts of progesterone & small amounts of estrogen
uterine/menstrual cycle
- effects of estrogen & progesterone on endometrium
- average is 28 day cycle (in synch w/ovarian cycle)
- mentruation, proliferative phase, ovulation, secretory phase
day 1-5: menstruation
- low levels of estrogen & progesterone cause endometrium to disintegrate & blood vessels to rupture
- lining breaks off and is eliminated through vagina
day 6-13: proliferative phase
- increased estrogen production from G. follicle causes endometrium to thicken & become vascular and glandular
day 14: ovulation (menstrual cycle)
release of egg changes hormone levels
day 15-28: secretory phase
- increased progesterone by corpus luteum causes endometrium to increase in thickness & maturation and mucus secretion in uterine glands
- endometrium is ready to recieve developing embryo
- if no embryo implants, corpus luteum breaks down and lack of hormones trigger menstruation to begin
Gametogenesis
either spermatogenesis or oogenesis
Spermatogenesis
- stem cells/spermatogonium divide by mitosis to produce primary spermatocytes
- pri. spermatocytes -> meiosis 1 = secondary spermatocyte
- sec. spermatocyte -> meiosis 2 = spermatids
- spermatids undergo spermiogenesis, then are released into seminiferous tubule
Spermatogonium
- stem cells
- 46
- have all chromosomes
Primary spermatocytes
- produced by spermatogonium
- 46
- have all chromosomes
Secondary spermatocytes
- produced by primary spermatocytes
- 23
- half of chromosomes
Spermatids
produced by secondary spermatocytes
Spermiogenesis
spermatids tranform into flagellated sperm (spermatozoa)
Oogenesis before puberty
- prior to birth
- oogenia divide by mitosis -> primary oocytes
- fetus has all oocytes at 20wks…each has begun meiosis 1 and stopped…no further development until puberty
Oogenesis at puberty
- primary oocytes resume development (1/mo)
- pri. oocyte grows -> meiosis 1 = 1 large sec. oocyte & small polar body (which doesn’t develop further)
- sec. oocyte proceeds to metaphase of meiosis 2 then stops (only completed if fertilization occurs…entry of sperm re-starts cycle, meiosis 2 completed, sec. oocyte converted into fertilized egg/zygote + 2nd polar body)
Oogenia
- stem cells
- all chromosomes
- produce primary oocytes
fertilization
- sperm pass through egg’s coronta radiata, then through zona pelucida, and then cortical reaction occurs
Coronta radiata
the egg’s outermost cell layer, sperm pass through it during fertilization
Zona Pelucida
egg’s second layer, sperm use enzymes in acrosomes to pass through it during fertilization
Cortical reaction during fertilization
- egg becomes impermeable -> prevents fertilization
- cell membrane of egg & sperm fuse
- egg finishes meiotic division -> creates mature ovum
- sperm’s tail & mitochondria degenerate (so all mitochondria in humans are of maternal origin)
- male & female pronuclei fuse to form new nucleus (46 chromosomes)
implantation
- may occur several days after fertilization
- zygote divides as it moves down fallopian tube
- at uterus, embryo embeds itself into thickened endometrial lining
- placenta produces Human Chorionic Gonadotrophic Hormone (HCG…what pregnancy tests look for)
- HCG maintains corpus luteum to keep estrogen & progesterone levels high (no HCG = no corpus luteum)
- Placenta will replace corpus luteum estrogen & progesterone with its own
effects of progesterone & estrogen during implantation
- shut down production of FSH = no new follicle during pregnancy
- maintain endometrium = don’t need corpus luteum
embryo development
- zygote quickly goes through 2, 4, & 8 cell stages (called cleavage)
- then through morula stage, blastula stage, gastrulation, embryonic period, and fetal period
morula stage
many cells, but still same size as original fertilized egg
blastula stage
hollow ball of cells
gastrulation
indent forms, allowing for 3 layers to develop. Each layer becomes a different part/organ
embryonic development period
up until end of 8th week
fetal period
from end of 8th week until end of pregnancy
support structures for fetus
- blastocyst provides 2 major divisions of cells: 3-4 cells become fetus, ~100 cells form trophoblast
- trophoblast produces 4 embryonic membranes
4 embryonic membranes produced by trophoblast
- chorion (placenta)
- amnion (amniotic sac)
- yolk sac
- allontois (umbilical cord)
birth
- scientific name: partuition
- 3 stages: contractions, delivery, placenta
Stage 1 of birth: Contractions
- uterus begins series of wavelike contractions that shorten uterine muscles & widen/dialate cervix.
- dialation -> release of oxytocin from post. pituitary -> oxy. causes more uterine contractions -> positive feedback loop maintained until delivery
- stage 1 ends when cervix is fully dialated
Stage 2 of birth: Delivery
- baby pushed out through contractions & mother “bearing down” or pushing w/stomach muscles
- if amniotic sac hasn’t broken yet, it does at this stage
Stage 3 of birth: Placenta
placenta (afterbirth) is pulled away from uterine wall and expelled through vagina after baby
Lactaction
- breast buds & duct system are in fetus at 18 weeks
- at puberty, estrogen & progesterone cause formation of adult breasts
- lactogenesis: changing mammary glands to allow full lactation (caused by hormones)
- 2 stages of lactation
Stage 1 of lactation
- mid-pregnancy
- glands able to secrete milk
- high levels of progesterone & estrogen stop secretion of milk
Stage 2 of lactation
- occurs about time of delivery
- onset of copious milk secretion
- removal of placenta is necessary for initiation of milk secretion
- hormones prolactin & oxytocin are essention for successful lactation
