Reproductive System - Embryology Flashcards
Explain how sperm gets to the right site.
At ovulation cervical mucus becomes less thick facilitating sperm transport
Fallopian tube come into close contact with the ovary as fimbria sweep the ovum into the tube
Peristaltic waves of fallopian tube musculature bring the ovum into the ampulla of the fallopian tube
Only 1% of sperm reach the site of fertilisation.
What is capacitation?
Final spermatozoan maturation step occurs in female reproductive tract
Spermatozoa can’t fertilise oocytes when newly ejaculated as membrane molecules are masked by plasma membranes
In uterus and oviduct, plasma protein covering is removed exposing binding portions of sperm head.
Describe the stages of fertilisation.
Binding of sperm to zona pellucida
Acrosome reaction
Penetration through zona pellucida
Fusion of plasma membranes
Sperm nucleus enters oocyte cytoplasm .
What are the results of fertilisation?
Restores diploid number of chromosomes (46)
Stimulates secondary oocyte to complete meiosis
Variation of human species as maternal and paternal chromosomes intermingle
Determination of the sex of new individual
Initiation cleavage .
What is cleavage?
Cleavage is a series of mitotic divisions
Resulting cells called blastomeres become smaller with each division
After 3 divisions blastomeres undergo compaction
Compact blastomeres divide to form a 16 cell morula.
Describe the formation of a blastocyst.
Blastocyst is an embryo 5-7 days after fertilisation
Hatches from zona pellucida before implantation
Central cavity filled with fluid
Outer cell mass - trophoblast
Inner cell mass - embryo blast .
Describe implantation.
When implantation begins outer cell mass divides and differentiates into
Outer syncytiotrophoblasts and inner cytotrophoblasts
Inner cell mass divides and differentiates into
Epiblast and hypoblast.
What is the uterus like during implantation?
Uterus is in secretory phase - blastocyst implants in the endometrium
If fertilisation doesn’t occur menstrual cycle begins.
Give some examples of why males can be infertile.
Low sperm count, blockage in genital tract, chromosomal defects etc
Sperm quality analysed based on count, motility and morphology
Low count - azoospermia
Poor motility - asthenospermia
Poor morphology - teratospermia.
Give some examples why females can be infertile.
Primary infertility - no evidence of being able to conceive
Secondary infertility - unable to bear a child after a successful pregnancy
No ovulation - no oocyte released.
Describe 2 assisted reproductive strategies.
Intrauterine insemination - cyropreservation of semen samples
IVF - collected sperm incubated with collected oocytes.
