Embryology Flashcards
What happens in the first week of embryology?
- Ovulation
- Fertilisation
- Implantation
What is ovulation?
- Egg released from ovaries and travels through fallopian tube
- Uterus prepares to receive egg - wall thickens
What is implantation?
fertilised egg attaches to wall of uterus
What is fertilised ovum called?
zygote (single cell)
What is a morula?
lump of cells formed at 4-6 days
(16 cells)
What is a blastocyst?
a hollow ball that has
a trophoblast
an inner cell mass (embryoblast)
formed at 6-10 days
What is the trophoblast?
A thin layer of cells that helps a developing embryo attach to the wall of the uterus, protects the embryo, and forms a part of the placenta.
What is the placenta?
organ that will organise the transport of nutrients to developing embryo and remove the waste from developing embryo
What positive factor can cause a rise of antibodies in the mother?
rhesus (Rh)
At approximately 10-12 days, the implanted trophoblast contains an embryoblast, which has 2 cell layers. (bilaminar embryo) What are the names of these layers?
epiblast
hypoblast
What does the epiblast give rise to?
embryonic ectoderm, mesoderm, endoderm
What does the hypoblast give rise to?
assists in formation of endoderm, extraembryonic (yolk sac) mesoderm
What does the embryo develop during gastrulation?
an axis (to become symmetrical)
the three cell layers (ectoderm, mesoderm, endoderm)
What is gastrulation?
Gastrulation is a key phase in embryonic development when pluripotent stem cells differentiate into the three primordial germ layers
What is the key stage of formation during gastrulation?
the formation of a groove which is the primitive streak
What is the primitive streak?
a linear band of thickened epiblast that first appears at the posterior end of the embryo and grows cranially
How do the three cell layers form?
Some ectodermal cells are induced to differentiate and migrate through the primitive streak, towards the hypoblast
These new cells are the mesoderm
An unknown interaction between the newly formed mesoderm and the hypoblast will form the endoderm
During what weeks do the major organs develop and what is this process called?
3-8
organogenesis
What is developing muscle structure called?
somite
What is present at 19-20 days?
neural groove and some somites
What does the neural tube become?
CNS
What is a disease caused by the developmental defect of the neural tube?
spina bifida
What is mesenchyme?
the meshwork of embryonic connective tissue from which all other connective tissues of the body are formed, including cartilage and bone
What is the neural crest derived from?
ectoderm
What does the neural crest have characteristics of despite being derived from another part?
mesenchyme
What is meant by the ‘trilaminar’ embryo?
embryo which exists as three different germ layers - the ectoderm, the mesoderm and the endoderm.
At around how many days does the embryo fold round the yolk sac, and some important organs appear?
25 days
When is the embryo called a foetus?
week 8
What are stem cells?
undifferentiated cells that can differentiate into many cell types
What are the two types of embryonic stem cells and where are they found?
totipotent (inner cell mass)
pluripotent (3 cell layers)
What is the difference between the embryonic stem cell types?
pluripotent (able to give rise to all cell types in an adult- more restricted)
totipotent (able to give rise to all embryonic and adult lineages).
What can adult stem cells differentiate into?
committed cell lines such as bone marrow
What are the layers of embryo from out to in?
ectoderm, mesoderm, endoderm
What does ectoderm give rise to?
skin
mucous membranes of mouth and anus
brain, spinal cord
tooth enamel
What does mesoderm give rise to?
connective tissue
most muscle
blood vessels
kidney and urinary system
reproductive system
serous membranes
What does the endoderm give rise to?
alimentary canal
respiratory system
parts of urogenital system
What is the name of the fourth layer of the embryo?
ectomesenchyme
What does the ectomesenchyme give rise to?
PNS
melanocytes
adrenal medulla
most of mesenchyme in head
dentine, cementum, PDL, jaw bones
What occurs if there is a developmental abnormality in the first 2 weeks of pregnancy?
spontaneous abortion
At what week do teeth begin to develop?
6
At what week do deciduous teeth fully form?
9
What happens if there is a developmental abnormality in weeks 3-12 (first trimester) of pregnancy?
development defect -period of critical sensitivity
What ‘period’ is weeks 13-39 of pregnancy?
functional maturity
What week does gastrulation occur?
week 3
