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57 Cards in this Set
- Front
- Back
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Fertilisation |
nuclei of a sperm and egg (secondary oocyte) join together = zygote is formed = maternal and paternal chromosomes join |
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zygote |
fertilised ovum (secondary oocyte) |
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When can fertilisation occur? |
During ovulation (14days before next period) oocyte can be fertilised for upto 24hrs after fertilisation |
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sperm viability |
sperm are viable for 24-48hours after ejaculation |
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for fertilisation to occur, sperm must: |
- stay in the vagina - not be destroyed by acidity - become able to swim and penetrate egg - swim through cervical mucus - swim towards correct uterine tube - not be consumed by phagocytes |
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Acrosome of sperm |
Sacwhich Containsenzymes so it can penetrate egg |
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nucleus of sperm |
contains DNA |
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Middle part of sperm (spiral coil) |
contains mitochondria to power the tail and give energy |
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tail of sperm |
propels the sperm to swim & move |
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sperm capacitation = |
sperm become able to swim and penetrate the oocyte occurs over 8-10hours after ejaculation substances present in semen cause the sperm to become motile by the time sperm reaches egg, its acrosome is ready to rupture |
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ovulation = |
rupture of an ovarian follicle releasing a secondary oocyte vascular follicle produces large amounts of oestrogen triggers LH surge ovulation occurs |
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what happens to the ovarian follicle after the secondary oocyte enters uterine tube? |
changes into the corpus luteum |
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what happens to secondary oocyte when ovulation occurs? |
enters the uterine tube |
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OOCYTE: corona radiata |
layer of cells surrounding the oocyte |
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OOCYTE: zona pellucida |
thick transparent membrane surrounding membrane |
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OOCYTE: oocyte nucleus |
contains DNA |
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sperm penetration |
sperm moves between cells of corona radiata acrosomal reaction occurs = |
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protection against polyspermy |
entry of sperm hardens the zona pellucide = blocks polyspermy (the entry of more than 1 sperm) |
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after sperm penetration, the oocyte completes meiosis 2, and becomes: |
ovum |
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sperm capacitation |
Whensperm become motile and capable of penetrating anoocyte. |
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zona pellucida |
Tough transparent membrane around the oocyte. |
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corona radiatia |
Alayer of cells surrounding the ovum. |
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process of fertilisation: |
1. Ejaculation 2. Sperm capacitation 3. Acrosomal reaction 4. Sperm penetration 5. Ovumcompletes meiosis II 6. Fertilisation |
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acrosomal reaction = |
- acrosomes of hundreds of sperm rupture - enzymes released from acrosomes break down the zona pellucida |
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embryo |
fertilisation( wk.1) to week 8 |
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morula |
solid ball of cells |
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implantation |
embryo implants in endometrium |
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gastrulation |
3 embryonic germ layers form |
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neurulation |
nervous system forms |
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Organogenesis |
organs form |
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cell division occuring from a zygote onwards |
mitosis |
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fetus |
from week 9 - term |
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cleavage |
mitotic division of zygote first occurs at 36hrs = 2 daughter cells (blastomeres) at 72hrs = morula (16+cells) Day 3-4 = 100 cells have reached uterus (blastocyst) |
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trophoblast cells |
form the placenta release HCG |
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inner cell mass |
becomes the embryonic disc (embryoand three of the embryonic membranes ) |
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implantation : |
blastocysts floats for 2-3 days ovulation begins 6-7 days after ovulation. Takes 5 days to complete trophoblast sticks to endometrium and cells proliferate blastocyst is covered by epithelial cells and is surrounded by a pool of from degraded endometrial blood vessels. Implantation is completed by the twelfthday after ovulation. |
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Trophoblast 2 layers: |
Cytotrophoblast: inner cells of cells Syncytiotrophoblast: outer cells thatlose their plasma membranes, invade and digest the endometrium |
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HCG |
secreted by trophoblast cells and later chorion prompts corpus luteum to continue secretine oestrogen and progesterone |
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HCG levels |
levels rise until the end of the second month, then decline as the placenta begins to secrete progesterone and oestrogen |
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placenta |
- provides nutrition to fetus - acts as a respiratory and excretory organ - produces hormones of pregnancy - is fully formed and functional by the end of 3rd month - physically separates maternal and fetal blood |
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placenta formed from; |
- formed by: maternal and fetal layers ---- embryonic tissue (chorionic villi) ---- Maternal tissue - endometrium |
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placental chorionic villi |
- grow into intervillous spaces filled with maternal blood contains blood vessels that run into umbilical arteries and veins |
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placental Endometrium |
- Deciduabasalis – between chorionic villi. - Deciduacapsularis – surrounding the embryo/fetus – towarduterine cavity |
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during implantation: |
the blastocyst starts to change into a gastrula (3 layered embryo) inner cell mass develops into embryonic disc 3 primary germ layers develop extra embryonic membranes develop |
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gastrulation |
embryonic disc changes into a 3 layered embryo occurs wk.3 •A groove appears on the dorsal surface ofthe embryonic disc = primitive streak. •Forms the longitudinal axis of theembryo. |
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gastrulation: formation |
•Cells begin to migrate into the grooveand form the 3 primary germ layers |
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gastrulation: endoderm |
first cells formed: - forms epithelial linings of digestive, respiratory and urogenital systems |
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gastrulation: Ectoderm |
cellsthat remain on the embryo’s dorsal surface Embryonic germ layer that forms the epitheliallining of respiratory and digestive tracts. |
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gastrulation: mesoderm |
Secondembryonic germ layer formed. cellsthat follow push laterally, |
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amnion |
fluid filled transparent sac |
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allantios |
base of umbilical cord. forms part of urinary bladder |
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yolk sac |
•Makes earliest blood cells and bloodvessels. |
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Chorion |
•Encloses embryo and all other membranes.Forms part of the placenta outermost embryonic membrane |
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Decidua basalis |
Thematernal portion of the placenta. |
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blastocyst |
Fluidfilled ball of trophoblast cells. |
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Embryonicdisc |
Structureformed from the inner cell during gastrulation. |
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trophoblasts |
Embryonic cells that form the fetalplacenta. |
