sexual reproduction in humans Flashcards
Name the hormone produced by the developing ebryo which prevents the breakdown of corpus luteum (1)
HCG/human chorionic gonadotrophin
what process is involved in the produciton of oogonium (1)
mitosis
suggest why only one functional female gamete is produced as a result of meiosis (2)
- polar bodies produced/reductio in genetic material at each stage of meiosis
- functional gamete retains most of the cytoplasm
- cytoplasm acts as a food store for zygote/provide mitochondria for zygote
- needed until implantation takes place/obtained from the placenta
describe the role of the acrosome plays in fertilisation of the ovum (2)
- releases proteases
- to break down the corona radiata/zona pellucida
cell cleavage (1)
- splitting/diving of zygote early embryo cells to form new cells
blastocyst (1)
hollow ball of cells /ball of undifferentiated /partly differentiated cells
implantation (1)
burying/embedding /implantion of the blastocyst/embryo into the uternine lining/endometrium
describe how the sperm is able to penetrate outer layers of the secondary oocyte (2)
- acrosome
- releases proteases which break down layers
state how the secondary oocyte usually prevents the entry of more than one sperm and suggest a reason why there is an increased risk with IVF with a risl of secondary oocyte not being fully matured (2)
- cortical granules rupture/cortical rection and zonal pellucida thickens/ fertilisation membrane forms
- seconndary oocyte taken from graafian follice is immature so cannot form a fertiliation membrane/zona pellucida cannot thicken/ less developed cortical granules
the developing embryo is not transferred into the uterus until three days after IVF using your knowledge of fertilisation and implantatio explain why this delay is needed (3)
- fertilisation normally int he fallopian tube
- embryo needed to each uterus/blastocyst to form/allow cleavage to take place
- if embryo put into uterus immediatley endometrium would not be fully developed
- trophoblastic/chorionic villi will not have developed
- embryo/blastocyst would not implant/survive
state four differences between the composition of the blood in the umbilical arteries and umblical vein (2)
umbilical artery
* less oxygen
* more CO2
* more ureA
* less nutrients
* less antibodies
umblical vein
* more oxygen
* less CO2
* less urea
* more nutrients
* more anitbodies
give two reasons why there must be a barrier between foetal and maternal blood systems (2)
- barrier against hormones/toxic substances/microorganisms/cells/mothers rhesus group/mothers antigens
- protection against differences in pressure
- protection against mothers immune system/antibodies
suggest how the following feature of the placenta enable it to carry out it’s function
the arterial blood flow to the placenta is high and the blood in the intervillus space is exchanged three times per minute
(1)
maintain concetration/diffusion graidents / prevent equilibrium being reached
suggest how the following feature of the placenta enable it to carry out it’s function the pressure in the uterine arteries is ten times greater than the pressure in the intervillus space (1)
pressure difference forces materials through capillaries
suggest how the following feature of the placenta enable it to carry out it’s function the length of the capillaries in the placenta is about 320 km(1)
large surface area for exchange
what is function of sertoli cells (1)
nutrtion of the sperm cells/ supplies oxygen/removes waste products
state the type of cell division involved in the production of spermatogonia (1)
mitosis
explain why there are more spermatozoa than spermattogonia in the tubule (1)
4 cells produced from each during meiosis
name the hormone produced by the developing embryo which preventss th breakdown of corpus luteum (1)
hCG/ human chorionic gonadotrophin
which process is involved in the production of oogonium (1)
mitosis
state why only one functional female gamete is produced as a result of meiosis (2)
- poar bodies produced/ reduction in genetic material at each stage of meiosis
- functional gamete retains most of the cytoplasm
- cytoplasm acts as a food store for zygote/provide mitochondria for zyogte
- needed until implantation takes place/obtained from placenta
describe the role of the acrosome in fertilisation of the ovum (2)
- releases proteases
- to digest the corona radiata/zona pellucida
Describe the events that take place within a human female from the release of the secondary oocyte to implantation of the embryo. details of sexual intervourse arre not required (10)
- ovulation/release of secondary oocyte takes place from ovary
- wall of fallopina tube transports seconday oocyte/embryo/blastocyst towards uterus by ciliate epitherlium
- spermatozoa travel from the vagina to the fallopian tube
- capacitation
- changes in membrane covering the acrosome
- fertilization takes place in the fallopian tubes
- acrosome reaction
- difestion of zona pellucida/corona radiata/releases enzymes
- cortical reaction/ formation of fertilisation membrane
- prevent polyspermy
- triggers second meiotic division of oocyte
- nuclei fuse to form zygote
- cleavage of zygote / undergoes metosis
- to form blastocyst
- implantation take place in endometrium
describe the formation of spermatoxoa in mammales explain how the process of oogenesis differs (10)
- occuse in semiferous tubukes
- germinal epitherlium divides by mitosis
- forms diploid spermatogonia
- spermatogonia form primary spermatocytes
- meiosis 1 occurs producing haploid n
- secondary spermatocytes
- meiosis II forms spermatids
- differntiate / mature into spermatozoa
- nourished by sertoli cells / protects them from the immune system
- polar bodies form in oogenesis but not spermatogenesis
- process begins at puberty for sperm but prior to birth
- mee
