Embryology Flashcards
Where does fertilisation take place?
Ampulla (in the Fallopian Tube)
Describe the process of fertiisation
- Sperm binds to a glycoprotein in the zona pelucida
- The sperm releases acrosomal enzymes to overcome the zp (and digest their way over the eg)
- The egg and sperm plasma membrane fuses and the sperm contents enter the egg
- The entry of sperm triggers the completion of meosis 2 and the release of corticle granules (preventing multiple sperms fusing with the egg)
What is Clevage?
Clevage is the process in which the zygote udergoes a series of mitotic divisions which sub-divide the egg into blastomeres
What is Compaction?
Compaction is the process in which the cells maximise space in the zona pelucida by coming into close contact with each other through tight junctions.
In this process the inner cell mass will begin to form the yolk sac and embryonic menbrane
Name the different parts of the blastocyte
Trophoblast (embryonic part of placenta- differeniates into syncitiotrophoblast and cytotrophoblast ) , Zona Pellucida, Blastocyte Cavity, Inner Cell Mass/ embryoblast (differeniates into epiblast and hypoblast)
What are the steps involved in implantation?
Adplantation of the blastocyte - takes place on 5th day- the blastocyte emergs from the zona pellucida and interacts with maternal tissue (endometrial uterine lining)
Once the blasocyte adheres to the the uterine wall, the trophoblast will secrete enzymes that digest the extracellular matrix and intrude between the endometrial cells attaching the blastocyte. Trophoblast cells continue to divide forming cytotrophoblast and syncytiotrophoblast
The embryo will also divide into a bilayerof Epiblast and Hypoblast
Implantation is complete by day 9
What is Gastrilation?
The process by which the bilamaniar embryo becomes three layers - driven by the primary streak. In the porcess epiblast cells move through the primary streak to form three germ layers (
What are the three germ layers formed from?
Ectoderm - Epiblast
Mesoderm - from both endoderm and epiblast
Definitive Endoderm - replaces hypoblast
What becomes of the Ectoderm?
Epidermis - nails/skin/hair
Nervous System - Brain Spinal cord and peripheral nerves
What becomes of the Paraxial Mesoderm?
Organises into two rods of tissue to form the midline structures - axial skeleton, voluntary muscles, part of the dermis
What becomes of the Intermediate Mesoderm?
Forms the urogenital systems - kidneys and ureter , gonads
What does the Somatic Mesoderm become (Part of the Lateral Plate) ?
Linings of the body, apendicular skeleton, majority of dermis and limb girdles
What does the Viseral Mesoderm become (Part of lateral Plate) ?
Cardiovascular system and mesoethil coverings (thin serrous membrane) , smooth muscles
What does the endoderm become?
Linings of the gut tube, Linings respiratory tract, Liings of bladder and urethera
