Embryonic Development Flashcards
How many days can sperm survive in the uterus?
5
What is auto-immune orchitis?
Where a man’s own body produces antigens against his own sperm - a cause of infertility.
What marks the gestational age?
From last menstruation to fertilisation.
What marks the embryonic period?
The end of the 2nd week to the end of the 8th week.
What marks the foetal period?
The end of the 8th week to birth.
What marks the embryonic age?
Fertilisation to birth.
What day does implantation in the embryonic period occur?
Day 6
Before implantation, what is the name of the layer a blastocyst must shed and what does it do?
Zona Pellucida - this layer prevents the blastocyst from sticking to the oviduct, however is no longer necessary for implantation.
What the removal of the zona pellucida known as?
Hatching
What the trophoblast become in later stages of pregnancy?
The yolk sac and placenta
What is placenta previa?
When the placenta implants itself across the cervix. A C-section is needed to deliver the baby.
What is an ectopic pregnancy?
What the blastocyst implants OUTSIDE the uterus…
During implantation, what does the trophoblast differentiate into?
The cytrophoblast and syncytiotrophoblast
What does the embryoblast differentiate into?
The epiblast and the hypoblast.
During implantation, what two cavities does the hypblast differentiate into?
The yolk sac and the chorionic cavity.
During gastrulation, what key feature appears at the end of the third week?
A primitive streak
What is the name of the new layer created by the primitive streak? What are the names of the three layers that now make up the new trilaminar disk?
Mesoderm Ectoderm (top), mesoderm (middle), endoderm (bottom).
Describe the future functions of the a)ectoderm b)mesoderm and c)endoderm.
Ectoderm - structures that maintain contact with the outside world e.g. Skin
Mesoderm - supporting tissues e.g. Muscle, cartilage
Endoderm - internal structures e.g. Epithelial lining of GI tract
During gastrulation after the development of the primitive layer, two small gaps occur in the mesoderm layer. What will these gaps become later on in fetal life?
The mouth and the anus.
What is situs inversus?
When the heart is on the wrong side of the body - symmetrical.
Only an issue if there is normal and abnormal mirror image disposition.
After the development of the primitive streak and creation of new mesoderm layer - what happens in neurulation?
A notochord appears from the primitive streak.
This sends signals to the ectoderm to change shape.
The edges of the ectoderm curl towards each other, lifting out to create a neural tube.
This feature makes up the basis of the foetal backbone.
During neurulation the mesoderm layer changes considerably, what are the name of the some of the sections it creates?
Paraxial mesoderm Somatic mesoderm Intraembryonic coelem Splanchnic mesoderm Intermediate mesoderm
What are somites?
Groves on the neural tube that make up future spinal discs.
They are created thorough organisation of the paraxial mesoderm into segments.
What three areas do somites differentiate into and what are their future functions?
Myotome - ‘muscle’ section
Dermatome - ‘skin’ section
Sclerotome - ‘hard tissue’ section
What is the cardiogenic area on the neural tube?
A half ring area at the cranial end of the neural tube, soon to be the foetal heart.
How many somites are there?
31
How does the trilaminar disc look different after its folded?
Folds into itself - the embryo becomes suspended into amniotic fluid with a connective stalk connecting it to the outside.
