Unit 2 - Reproduction and Development Flashcards
Primary Sex Characteristics )
(M)
Structured directly involved in forming and transporting gametes (sex cells/ sperm).
Secondary Sex Characteristics (M)
Develop in males due to testosterone, but are not directly involved in reproduction.
—>Large larynx (lower voice), facial and body, muscle development.
Testes
Contains long coiled tubes called SEMINIFEROUS TUBULES.
–>ST is where spermatogenesis occurs (creation of cells).
Sperm Structures
1) Head
2) Acrosome
3) Middle Piece
4) Long tail
Interstitial Cells (Ley dig Cells)
Cells between tubules, produce testosterone.
Sertoli Cells
Large pyramidal cells with seminiferous tubules.
–>They help develop and nourish the sperms.
Head
Contains the nucleus that has DNA as well as Acrosome.
Acrosome
Contains enzymes used to break down outer layer of the egg, so DNA can enter the egg.
Middle Piece
Contains lots of mitochondria to produce energy (ATP) for movement.
Long tail
Moves sperms forward.
Testes During Puberty
They descent.
–> Proper spermatogenesis needs temperature slightly lower than body temperature.
–> If testes don’t descend, can lead to sterility (unable to produce).
Pathway of Sperm
Testes –> Epididymis –> Vas (Ductus) Deferens –> Ejaculatory Duct (Prostate Gland, Cowper’s Gland, Seminal Vesicles) –> Urethra (within the penis).
Seminal Fluid
1) Sperm
2) Fluid from seminal vesicles containing sugars and used by sperm for ATP production.
3) Secretions from prostate gland, Cowper’s (bulbourethral) gland, alkaline to neutralize acidity of urine and acidity of female reproductive tract.
Primary Sex Characteristics (F)
Produce and transport gametes (eggs).
Gonads (F)
OVARIES, produce eggs and sex hormones (estrogen and progesterone).
Secondary Sex Characteristics (F)
Less facial/body hair, breasts, higher voice, wider hips, less muscle development.
–> Caused by estrogen.
Ovaries
Site of Oogenesis (production of eggs).
–>Contain specialized structure called follicles, each follicle contains one developing egg.
Ovulation
Once a month, one of the ovaries will develop an egg inside a follicle and release the egg into the reproductive tract.
Eggs (Ovum)
Cannot move.
–> Much larger than the sperm by about 20x because it contains all the resources (cytoplasm, organelles) for potentially developing embryo.
–> Contains 23 chromosomes (half a human’s DNA, sperm has the other half).
Gonads (M)
Structures which forms gametes, produce sex hormones.
Male:
—>Testes is responsible for production of sperm and testosterone.
Fimbriae
Sweeps egg into oviduct.
Oviduct (Fallopian Tube)
Carries egg from ovaries to uterus.
–> Site of fertilization.
Uterus (Womb)
Large, pear-shaped organ which holds and nourishes developing fetus.
–> If egg is fertilized, it will implant into inner lining of uterus.
–> If egg is NOT fertilized, it will exit the body through menstruation.
The Uterus (2 Major Tissues)
1) Outer Muscle Layer
2) Inner Glandular Layer (ENDOMETRIUM)
Endometrium
Contains many blood vessels to nourish developing embryo.
–> Thickness changes throughout menstrual cycle.
–> If fertilization does not occur, endometrium and unfertilized egg is shed.
Cervix
Opening at bottom of uterus.
Vagina
Birth canal, leading from uterus to outside of body.
Vulva
External reproductive structures, includes LABIA and GLANS CLITORIS.
Male Reproductive Hormones
1) GnRH
2) FSH
3) LH
4) Inhibin
GnRH (M)
At puberty: hypothalamus releases GnRH (Gonadotropin releasing hormone).
–>Causes pituitary gland to release FSH and LH.
FSH (M)
(Follicle - Stimulating Hormones)
–> Travels to Sertoli cells for Spermatogenesis.
–>Causes Sertoli cells in the seminiferous tubules to release INHIBIN which inhibits further lease of FSH by anterior pituitary.
LH (M)
Travels to interstitial (Leydig) cells, simulate production of testosterone.
–> Causes interstitial/Leydig cells to release testosterone which negatively feeds back to hypo/pit.
Andropause
At age 40: decline in testosterone and spermatogenesis, makes reproduction less likely.
–> Can cause low sperm count, loss of muscle/bone mass, depression, increased risk of prostate cancer.
Female Reproductive Hormones
At birth: females have finite number of immature follicles (primary follicles).
At puberty: one follicle will develop each month, producing one mature egg.
–>Ovaries produce female sex hormones ESTROGEN and PROGESTERONE.
Menstrual Cycle
Starts at puberty and ends at menopause.
–>28 day cycle, ensures uterus is ready to receive a potentially mature egg.
–> Made up of OVARIAN CYCLE and UTERINE CYCLE.
–> Both occur at the same time in different locations.
Oogenesis Steps
Formation and development of egg.
–> Each follicle contains:
1) Primary Oocyte (immature egg)
2) Granulosa Cells (help and nourish developing egg)
Follicle cells start dividing, follicle increases in size.
–>Follicle bulges out, eventually burst, causing egg to be released from ovary (ovulation).
Left Over Follicle Cells –> Corpus Luteum
If no fertilization / pregnancy occurs, corpus luteum degenerates in ~10 days.
Ovarian Cycle Stages
1) Follicular Stage
2) Luteal Stage
Follicular Stage
Hypothalamus releases GnRH which causes pit. to release FSH.
–> FSH causes ovaries to develop a follicle, developing follicle releases ESTROGEN.
–> High estrogen levels negatively feeds back to prevent more FSH release.
–>Near the end of follicular stage (~13 days) GnRH causes pit. to release LH which stimulates ovulation (day 14)
Luteal Stage
Leftover follicle cells develop into CORPUS LUTEUM (caused by LH).
–> Corpus Luteum secretes PROGESTERONE and some estrogen.
–> Progesterone negatively feeds back which prevents release of LH.
–> As Corpus Luteum degenerates, progesterone and estrogen levels fall, causing GnRH to trigger FSH and the next cycle begins.
Testosterone
Further stimulates spermatogenesis and develop primary and secondary sex characteristics.
Uterine Cycle
Day 1-5: Menstruation
Day 6-13
Day 14: Ovulation
Day 15-28
Uterine Cycle : Day 1-5 (Menstruation)
Endometrium sheds due to low levels of progesterone and estrogen.
Uterine Cycle: Day 6-13
Estrogen released from developing follicle, causes endometrium to thicken.
Uterine Cycle: Day 14-28
Progesterone from Corpus Luteum maintains thickness of endometrium, inhibit uterine contractions to prevent menstruation.
—>If no fertilization: progesterone and estrogen levels fall, trigger menstruation and beginning of new cycle.
Menstrual Cycle
1) Flow Phase
2) Follicular Phase
3) Ovulatory Phase
4) Luteal Phase
Flow Phase
Menstrual
Follicular Phase
Follicle developing and releasing estrogen, restoring endometrium.
Ovulatory Phase
Ovulation, triggered by LH.
Luteal Phase
Corpus Luteum releases progesterone and estrogen, thicken and maintain endometrium.
—>No fertilization: progesterone and estrogen full due to Corpus Luteum degeneration triggers next cycle.
Menopause
Decreasing in estrogen and progesterone, due to decreasing number of functional follicles as woman ages.
—>Menstrual cycle stops.
—>SYMPTOMS: hot flushes, mood changes, less in bone mass, increased cholesterol.
—> Can be treated with replacement hormones.
Prenatal Development
1) Embryonic Period
2) Fetal Period
Embryonic Period
Week 1 to week 8, called embryo.
Fetal Period
Week 9 to birth, called fetus.
Fertilization
Zygote: Egg nucleus (23 ch) + Sperm nucleus (23 ch).
First stage of embryonic period.
—>Most occur in oviduct, with 24 hours of ovulation.
—>Billions of sperm during ejaculation (M), few dozen actually make it to the egg.
Zona Pellucida + Corona Radiata
Surround the egg, sperm must get through these layers to reach the egg.
—> When sperm meets egg, acrosome releases digestive enzymes to digest through ZP + CR.
First Sperm Enters Egg
Depolarizes plasma membrane of the egg, prevents other sperm from entering.
Cleavage
As zygote moves through oviduct, it begins to divide (1 cell –> 2 cells –> 4 cells –> 8 cells)
–> Volume of cell decreases as CLEAVAGE occurs, but number of chromosomes in each cell stage is the same.
Mitosis
Each cell keep full number of chromosomes after division.
Morula Stage
16 cell Stage
Blastocyst
When embryo reaches the uterus for implantations, it’s now called a BLASTOCYST.
Contains:
1) Trophoblast
2) Inner Cell Mass
hCG (Implantation)
HUMAN CHRONIC GONADOTROPIN:
–> It is a hormone secreted by TROPHOBLAST after implantation. It maintains corpus luteum for 2-3 months of pregnancy so it can continue secreting progesterone and estrogen = menstruation is inhibited.
Gastrulation
After implantation, cells of the embryo starts to differentiate.
–> Marks the beginning of distinct structure forming.
–> Embryo is now called GASTRULA.
Gastrula Organ Formation
Weeks 3-8, it has 3 primary layers, each of which will form different structures in the human body:
1) ECTODERM: nervous system, epidermis (skin)
2) MESODERM: skeleton, muscles, repro structures
3) ENDODERM: lining of digestive and respiratory system, glands
Extra- Embryonic Structures
1) CHORION
2) AMNION
3) ALLATOIS
4) YOLK SAC
Amnion (Amniotic Sac)
Encloses the embryo (fetus, only penetrated by umbilical cold).
–> Filled with AMNIOTIC FLUID which cushions/ protects embryo/fetus.
Yolk Sac
Helps form parts of digestive tract, blood, sex cells, but does not provide nurtrients.
Chorion
Outer most later, forms fetal portion of placenta.
The Placenta
Disk shaped organ attached to uterine wall.
–> Fetus attached to placenta by umbilical cord.
–> Has fetal portion and maternal portion.
Fetal Portion
Formed from CHORION.
–> Contains CHORIONIC VILLI: extended projections of fetal blood vessels extending into uterine lining.
Maternal Portion
Pools of blood around chorionic villi.
–> Nutrients and waste can diffuse from mother to fetus, fetus to mother, but their bloods don’t mix.
–> Alcohol, drugs, nicotine can also diffuse through, can harm fetus.
Umbilical Cord
Connects fetus to placenta, contains fetal blood vessels.
–> Cut and tied after birth.
Trophoblast
Outer layer, later develops into part of placenta.
Inner Cell Mass
Develop into the baby.
DURING IMPLANTATION: Inner Cell Mass faces inside of endometrium, trophoblast helps digest through endometrial tissue.
hCG (After 2-3 Months)
–>Placenta will be fully formed, can secrete estrogen and progesterone to maintain endometrium. CL can now degenerate.
–> Pregnancy tests detect hCG in urine.
–> Levels decline at 4 months as placenta can secrete the hormones and CL is no longer needed.
Allantois
Forms base of umbilical cord, parts of urinary bladder.
Determining Biological Sex
Egg (X ch) + Sperm (X ch) = Female Zygote (XX)
Egg (X ch) + Sperm (Y ch) = Male Zygote (XY)
Trimesters
Pregnancy can be divided into three trimesters (3 months/ 12 weeks each).
Teratogens
An agent which can harm development of embryo/ fetus.
–> Genetic (disorders) or Environmental (drugs, alcohol, smoke, infections).
–> Embryo / Fetus is most vulnerable to teratogens during embryonic development.
Parturition
Contraction of uterine muscles:
–>Baby’s head pushes down on cervix, cervix is stretched.
–>Cervical stretching sends nervous signal to pituitary which releases OXYTOCIN.
1) Dilation
2) Expulsion
3) Placental
Oxytocin
Causes uterine contractions, also cause release of prostaglandins, further stimulate contractions.
–> Contractions cause baby’s head to push on cervix, causing more release of oxytocin, etc.
Relaxin
Releases pelvic muscles and ligaments.
Dilation
2-20 Hours. Dilation of cervix to 10 cm.
–> Water breaks: amniotic sac breaking, the “water” is referring to amniotic fluid.
Expulsion
30-2 Hours.
–> Strong uterine contractions push baby out through cervix to birth canal (vagina).
Placental
10-25 minutes after expulsion (after birth).
–> Continues contractions cause placenta to be expelled.
C-Section
Make incision in abdomen and uterus to remove the baby.
–> Baby in breech (feet first)
–> Mother has STI, can be passes to baby in birth canal.
–> Mother has a narrow pelvis.
Lactation
Production and release of breast milk.
–> Suckling at the nipple sends nervous signal to hyp. , hyp. signals to pit. to release OXYTOCIN.
1) Prolactin
2) Colostrum
Prolactin
Responsible for milk production.
–> Secretion of prolactin inhibited during pregnancy by estrogen/ progesterone.
Colostrum
Released for first few days after birth, high proteins and antibodies for immune protection of newborn baby.
Sterile
Cannot have children.
Infertile
Struggling to have children, but not impossible.
In-Vitro Fertilization (IVF)
Taker egg out of female, sperm out of male, fertilize them outside of the body, fertilized zygote placed back to uterus for implantation.
Superovulation
Female given dose of FSH, causes ovaries to release multiple eggs.
Surgical Sterilization
Women: cutting and tying oviduct (TUBAL LIGATION)
Men: cutting and tying vas deference (VASECTOMY)
Hormonal Contraception
Mimic progesterone, negative feed back to prevent release of FSH and LH, preventing ovulation.
