Embryology Flashcards
How many hours after fertilisation does eggs split into two blastomeres? How many cells after 3 more divisions? Known as what?
30 hours
16 cells
Morula
Within what week do the cells of the morula reorganise to form the blastocyst cavity?From then, known as what? Two cell types?
1st week
Blastocyst
Outer mass= trophoblast– endometrium for implantation
Inner mass= embryo blast
During what week does the trophoblast divide into the synctiotrophoblast and cytotrophoblast? The embryo blast divides into what? Known as what?
2nd week
Epiblast and hypoblast
Bilaminar disc
Amniotic cavity forms within what?
The epiblast
What happens in 1st week of embryonic period? 2nd week? 3rd week? 4th week? 5th- end of 8th week? End of 8th week?
Fertilisation and blastocyst formation- F= first
Implantation and bilaminar disc formation (2= bi)
Embryo development and trilaminar disc forms
Folding of embryo (F=4th=folding)
Development of all organs
All organs have developed and embryo looks like an adult- called a foetus
Which layer becomes continuous with the uterus? Maternal blood vessels known as what? Invades spaces in synctiotrophoblast known as what?
Synctiotrophoblast
Sinusoids
Lacunae
What occurs during gastrulation (3rd week)? Orchestrated by what? What is this? What lies within this and this?
Bilaminar disc forms 3 germ cell layers
Primitive streak
Groove in midline of epiblast
Primitive node at cranial end- within this= primitive pit.
Cells of epiblast break off and migrate towards primitive pit to form what 3 layers? They are each formed by what?
Endoderm, mesoderm and ectoderm
Endo= epiblast cells migrate through primitive pit and displace hypoblast cells
Meso= epiblast cells migrate through primitive pit and lie between epiblast and newly formed endoderm
Ecto= epiblast cells that remain in position
What structures derive from the endoderm?
Epithelial lining of GI and resp tract, lining of urethra, bladder and reproductive system, liver and pancreas
What structures derive from mesoderm?
Notochord, MSK system, muscular layer of stomach, intestine etc., circ system
What structures derive from ectoderm?
Epidermis of skin, cornea and lens of eye, CNS and PNS
What are the 3 mesoderm parts? What does each form?
Paraxial plate, intermediate plate and lateral plate
Paraxial–> somites–> a) Myotome- muscle tissue, b) sclerotome- cartilage and bone, c) dermatome- dermis of the skin
Intermediate—> kidneys, gonads and respective duct systems
Lateral–> 1) somatic- body wall, 2) splanchnic–> circ system, connective tissue for glands, muscle, connective tissue and peritoneal components of way of the gut
Somites develop in what direction? 1st pair on what day? At rate of how many pairs a day until 42-44 pairs formed?
Cephalocaudal direction- head to tail (paired segments on each side of notochord)
Day 20= 3 pairs per day until 42-44 pairs are formed
Where is oropharyngeal membrane what does it consist of? Where is cloacal membrane and what does it consist of?
At cranial end= small region of tightly adherent ectoderm and endoderm cells–> oral cavity
No mesoderm between ecto and endoderm
Caudal end- tightly adherent ectoderm and endoderm cells- no intervening mesoderm
What does cranial area contain? Where does cranial flexion bring these things?
Buccopharyngeal membrane, cardiogenic area and septum transversum–> ventrally–> ventral surface of future face, neck and chest
Heart into thoracic position and septum transversum–> diaphragm
