Human Reproduction GCE Study Buddy Biology Sexual Reproduction in Human testi s meiosis sperm s fertilization zygot
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Human Reproduction GCE Study Buddy Biology
Sexual Reproduction in Human testi s meiosis sperm s
fertilization
zygot e embry o foetus bab
ovar meiosisy eggs (ova)
Male Reproductive System ureter seminal vesicle prostate gland urethra
urinary bladder sperm duct Cowper’s gland penis
epididymis testis scrotum
Male Reproductive System
Male Reproductive System
secrete seminal fluid
seminal vesicle prostate gland Cowper’s gland
Testes ● For production of male gametes (sperms) ● For production of male sex hormones
Epididymis ● For temporarily storage of sperms ● During copulation, muscles of epididymis contract to release sperms
epididymi s vas deferens (sperm duct) sperm tubules
Functions of Seminal Fluid ● To provide a medium for the sperms to swim ● To activate and nourish the sperms ● To neutralize the acidity in female reproductive tract ● Sperms + seminal fluid = semen
Penis ● Erected during copulation for insertion into vagina ○ Dilation of arterioles causes the erectile tissue of penis to become turgid ○ Muscles of epididymis contract ○ Semen is squeezed from the penis to the top of vagina
(ejaculation)
Male Gamete (Sperm) vesicle contains enzymes involved in penetration of ovum during fertilization head middle piece tail brings about movement
Nucleus containing DNA mitochondria which release energy during respiration
Female Reproductive System oviduct funnel of oviduct uterine lining
ovary
uterus muscular wall
cervix vagina
opening of vagina
Female Reproductive System
Functions of Ovary ● For production of female gametes (ova/eggs) ● For production of female sex hormones
Ovulation ● The release of an ovum from an ovary
Oviduct ● Carries the ovum forward by ○ the beating action of the cilia on its inner surface ○ the contraction of muscles of oviduct ● Place for fertilization (upper part)
Human Gametes Sperm Size Shape
much smaller
much larger
(~0.05mm)
(~0.1mm)
tadpole-like (with head & tail)
Position of nucleus Movement
Ovum
in the head
spherical toward center
strongly mobile by not able to move its tail by itself
Menstrual Cycle ● Once in about 28 days ● The uterine lining becomes thickened 14 days after menstruation to prepare for the fertilized ovum to implant in it ● Uterus : ○ thickening of lining --> menstruation (discharge of lining if no fertilization)
● Ovary : ○ follicle --> mature follicle --> yellow body
Menstrual Cycle ● Day 1 - 5 ○ Menstruation starts ○ Uterine lining decreases in thickness to a minimum ● Day 6 - 14 ○ Lining becomes thicker with increased blood supply ○ Day 14 : ovulation ● Day 14 - 28 ○ Lining remains thick to ready for implantation of fertilized ovum ● Day 28 ○ No implantation of fertilization ovum ○ Uterine lining breaks down; menstruation starts
Inside Ovary ● Follicle & Yellow body ○ secretes different types of sex hormones ● No fertilization occurs ○ yellow body disappears after few days ○ no sex hormones secretion ○ menstruation (discharge of uterine lining)
Cycle of Follicle Development
Transfer of semen 1. Sexual stimulation --> Dilation of arteriole in erectile tissue of the penis --> Penis becomes erect. 2. Penis is inserted into the vagina --> Movement --> Muscles of epididymis contract --> Eject semen --> Ejaculation 3. Sperms are transferred from a man into a woman’s body. --> Copulation
Fertilization oviduct ovary uterus cervix
vagina
Fertilizatio n
Female nucleus
One sperm penetrates the egg membrane.
Clear membrane hardens; no others sperms can enter.
Male nucleus fuses with the female nucleus.
Events after Fertilization ● Sperms (from copulation) reach the upper part of the oviduct ● Ovum is fertilized at the oviduct ● Fertilized ovum (zygote) is carried to the uterus ● After reaching the uterus, the embryo (developed zygote) fixed firmly onto the thick uterine wall ○ Implantation
Implantation fertilized egg
cavity
2-cell stage
outer cell layer
a ball of cells
future embryo yolk sac
uterine lining inner cell mass
uterine lining amnion
1st day
st
1 week
2nd day
3rd day
2nd week
4th day
3rd week
Development of Human Foetus
uteru foetuss placent umbilicala
cord amnio n amniotic fluid
Functions of Uterus ● During embryo development ○ Protect the embryo ○ Provide a constant environment for the embryo to develop ○ Allow placenta to attach on
● During birth of baby ○ Push the baby (foetus) out by muscular contraction
Functions of Amniotic Fluid ● To keep the foetus moist to prevent dessication ● As a water cushion to ○ support the foetus ○ allow it to move freely ○ absorb shock during movement of mother ○ protect the foetus from mechanical injuries
● To reduce temperature fluctuation ● To lubricate the vagina during birth
The Placenta oxygenated blood from mother’s artery deoxygenated blood to mother’s vein villus umbilical vein umbilical artery
Functions of the Placenta ● As a place for exchange of materials between mother and the foetus ● For secreting female sex hormones ● Umbilical cord ○ umbilical artery ■ deoxygenated blood ■ less nutrient than umbilical vein ■ more CO2 & waste than umbilical vein
Adaptations of the Placenta ● With villi ○ to increase surface area for diffusion of materials
● Maternal blood and foetal blood flows in opposite direction ○ to maintain diffusion gradient for the whole length
● Maternal blood capillaries and foetal blood capillaries are separated by a thin membrane ○ to shorten the distance for diffusion of materials
● Maternal blood is separated from foetal blood by capillary wall ○ to prevent high pressure of maternal blood to break the delicate foetal blood vessels ○ to prevent harmful substances (eg. bacteria) to enter the foetus ○ to prevent clotting of maternal and foetal blood if their blood groups are incompatible
Birth Control ● Human population increases exponentially ○ leads to shortage of resources ○ problem of pollution becomes more serious ○ easily overcrowded
Contraception Methods 1. Natural (Rhythm) Method ○ Prevent copulation during 5 days before and after ovulation (fertile period)
2. Contraceptive pills ○ Contains female sex hormones which inhibit ovulation ○ Must be taken daily ○ May have side effects
3. Condom ○ Have male and female condom ○ As a barrier to prevent sperms from entering vagina
4. Diaphragm ○ Fitted over the cervix ○ To be used together with spermicides
Surgical Methods Vasectomy Cutting and tying up of sperm ducts
Tubal ligation Cutting and tying up of oviducts
Prevention of Implantation Intra-uterine device (IUD) - A form of coil / loop - Insert it into the uterus - Regular medical examination --> Remain in place - Irritation to the lining of the uterus