Fertilisation To Trilaminar Embryology Flashcards
What receptor does sperm bind to on the ovum
Glycoprotein ZP3 on the zona pellucida
How does the sperm penetrate the zona pellucida
Release o acrosomal enzymes
What are the 3 components of a sperm head
Acrosome
Sperm nucleus (haploid)
Plasma membrane
Why do the plasma membranes of the sperm and ovum need to fuse
So nucleus of sperm can enter
What does the entry of sperm into the ovum trigger
Completion of meiosis 2
Release of cortical granules by oocyte
What is the function of cortical granules
Hardens zona pellucida prevent polyspermate
What is the opening for ovum to enter the uterine tubes called
Uterine abdomen oss
What happens to the overall size of the zygote structure
Doesn’t change, blastomere cells get smaller
What types of cell does up to the 8 cell stage blastomere contain
Totipotent
What is a totipotent cell
Can form any cell type
Embryonic cell
Placental cell
What is mosaicism / mitotic nondisjunction
2 different cell lines with different chromosome compliments
(E.g. if 1 cell divides unevenly where 1 daughter cell has 1 chromo and another has 3, only affects those 2 cells not all cells)
How does compaction of the morula
Confined within zona pellucida
To make max use of space, cells become tighter and form cell junctions
Outer-cells form gap junctions
What happens when outer cells in contact with the zona pellucida form gap junctions
Fluid enters through the zona pellucida
What are the 4 components of the blastocyst
Trophoblas (embryonic part of placenta)
Zona pellucida
Blastocyst cavity
Inner cell mass (forms the embryo)
How does blastocyst hatching occur
Trophoblas broken down
Cell bundles contract to burst out allowing implantation
Where does implantation occur
Directly on the endometrial lining on the superior aspect of the posterior uterine wall
What is the function of the corpus luteum
After ovulation, follicle develops into corpus luteum which secretes progesterone
What is the function of progesterone
Maintain thick endometrial lining for implantation
What are the 2 cell layers of the bilaminar embryo
Epiblast
Hypoblast
Amniotic cavity also begins to form in embryo
What do trophoblast (outer cell mass) develop into
Cytotrophoblast
Syncytiotrophoblast
What is the function of the synctiotrophoblast
Produces human chorionic gonadotropin (hCG)
Stimulates corpus luteum
Drives invasion of endometrial lining
What surface of the embryo os the epiblast
Dorsal
What surface of the embryo is the hypoblast
Ventral
Where does the amniotic cavity form
Epiblast
Where does the primitive yolk sac form
Hypoblast
When implantation is complete how is the small gap closed
Fibrin coagulum
Where do lacunae form
In the synctiotrophoblast
How does oxygen diffuse to the embryo
Uteroplacental circulation
Maternal blood flows into lacunae to diffuse to the embryoblast
What is formed after the extraembryonic mesoderm develops then degenerates
Chorionic cavity
What forms the definitive yolk sac
A second wave of hypoblasts
As the chorionic cavity develops what other structure develops
Connecting stalk
What entirely encircles an implanted embryo
Chorionic cavity
What structure separates the amniotic sac and definitive yolk sac
Bilaminar embryonic disc
What are the abnormal sites where implantation can occur
Ovary
Uterine tube
Peritoneum
Where does the primitive streak appear
Midline at caudal end of epiblast
What is found at the cranial (head) end of the primitive streak
Primitive pit
Primitive node
What does the primitive streak consist of
Pit
Node
Groove
What is the function of the primitive pit
Helps with the rotation of folds ( sets up body axis)
What are hypoblast cells replaced by
Definitive endoderm
How are the 3 germ layers formed
Movement of epiblast cells through the primitive streak
How does the misoderm form
Cells migrate through the primitive streak between epiblast and endoderm
Epiblast becomes ectoderm
What does the ectoderm form
Epidermis of skin
Nervous system
What is the notochord
Transient embryonic anatomical structure with the 3 regions of the mesoderm at each side
What are the 3 regions of the mesoderm
Paraxial
Intermediate
Lateral plate
What are the 2 layers of the lateral plate mesoderm
Somatic layer - body
Visceral layer - organs
What does the paraxial mesoderm form
Vertebral column
Skeletal muscle
Parts of the dermis
What does the intermediate mesoderm form
Urogenital systems
Kidney and ureter
Primary and secondary reproductive organs
What does the somatic layer of the lateral plate mesoderm form
Most of the dermis
Lining of body wall
Parts of limb
What does the visceral layer of the lateral plate mesoderm form
Cardiovascular system
Lining of organs
Smooth (involuntary) muscle
What does the endoderm form
Lining of gut tube
Lining of respiratory tract
Lining of bladder and urethra
