Week 4 - Introduction to embryology Flashcards
Embryology
The study of development of an embryo from the state of fertilisation to the fetal stage
3 stages of life before birth
Preimplantation stage (w1)
Embryonic stage (organogenesis) (W2-8)
Fetal stage (9-38)
Oocyte
Another word for an egg
Process where embryo proliferates
Cleavage
What happens to the size of embryo as it travels down the fallopian tube
Stays the same
What is the narrowest part of the fallopian tube
Isthmus
Name of tough peptidoglycan coat around the embryo
Zona pellucida
What happens to pronuclei upon formation of a zygote
One contains paternal
One contains maternal
Two combine to form embryonic genome
What is embryo called when it contains 16 cells
Morula
In what structure can the first sign of cellular differentiation be seen
Blastocyst
What does the ICM go on to develop
Embryo
What are the outer cells called in the blastocyst and what do they contribute to
Trophoblasts - placenta
What happens when blastocyst enters the uterine cavity
Fluid enters via the zona pellucida forming the blastocyst cavity
Why does blastocyst need to impant
It runs out of nutrients
What causes ‘hatching’ of blastocyst
ICM continue to proliferate AND fluid fills up. Fluid bursts through the zone pellucida
Decidualisation
Morphological change to cells of endometrium in preparation for and during pregnancy
What happens to trophoblast cells upon making contact with endometrium
They differentiate and form the bilaminar disc
What is the bilaminar disc make up of
Hypoblast
Epiblast
What is the invasive layer of cells called and what does it do at the end of week 2
Synctiotrophoblast starts to communicate with maternal side of placenta. This enables diffusion of O2, waste and nutrients via blood supply
What is a urinal chemical marker used to detect pregnancy
Human chorionic gonadotrophin (HcG)
What is an ectopic pregnancy
Implantation in the wrong place e.g uterine tube, peritoneal cavity, surface of ovary
What can cause ectopic pregnancy
Slow transit through uterine tube
Premature hatching
Why do ectopic pregnancies not develop
They can’t produce a fully developed placenta
Amnion fetal membrane
Lines the amniotic cavity which protects the developing embryo
Chorion cavity membrane
Lines a structure called the chorionic cavity AND forms the fetal component of the placenta
Yolk sack
Continuous with hypoblast of the bilaminar disc.
Involved in nutrient transfer in w2-3 disappears at w20
Blood cell formation and formation of the gut
Allantois
Outgrowth of yolk sac
Contributes to umbilical arteries and connects to the fetal bladder
Process that happens during week 3
Gastrulation
What is gastrulation
Formation of trilaminar embryo (ectoderm, mesoderm, endoderm) from the bilaminar epiblast
Describe the movement of cells during gastrulation
Epiblast cells move in at the primative streak forming the future ectoderm, the mesoderm and the endoderm
Examples of structures produced from ectoderm
Epidermis of skin
Cornea and lens of eye
Examples of structures from mesodern
Skeletal system
Muscular system
Examples of structures formed from endoderm
Epithelial lining of digestive tract
Lining of urethra
