Flashcards in Embryology Deck (39):
Study of the origin and development of an organism
How long is the "fetal" age?
How long is the "gestational" age?
How long and what defines the "embryonic" period?
First 8 weeks
All major organs formed
How long and what defines the "fetal" period?
Remaining 30 weeks
Organs grow larger and increase in complexity
Egg released into the peritoneal cavity
Occurs as egg travels down the fallopian tube
The cell that forms when the ova and sperm fuse
Define Cell Division
Begins immediately as the zygote travels down the fallopian tube and into the uterus
What occurs during the first week after conception?
Zygote divides repeatedly
Daughter cells = blastomeres
Solid cluster of 12-16 blastomeres at about 72 hours
When occurs on day 4 post conception?
Morula enters uterus and takes up fluid becoming a blastocyst
Types of Cells in the Blastocyst Stage
Inner cell mass
Define Inner Cell Mass
Forms the embryo
Layers of cells surrounding the cavity which helps form the placenta
What occurs on day 6 post conception?
Implantation of the zygote
What occurs during implantation?
Tropholast erodes uterine wall
Three Primary Germ Layers
The ectoderm and endoderm form what?
Sheets of epithelial tissue
The mesoderm forms what?
Invagination of epiblast cells
When does the endoderm form?
When does the mesoderm form?
What occurs during days 16-18?
Epiblast cells invaginate
Migrate anteriorly with endoderm cells
Rod defining body axis formed
Notochord is future site of vertebral column
Formation begins of spinal cord and brain
What occurs during neurulation
Neural plate to neural groove to neural tube
What are the three regions of the mesoderm?
Somites: beginning of vertebral bones
Lateral plate: forms cavity
When does the neural tube close?
Starts at the end of week 3 and completes at end of week form
What is the somatic mesoderm opposed to?
What is the splanchnic mesoderm opposed to?
What is between the somatic mesoderm and splanchnic mesoderm?
What serous cavities form from the coelom?
Major Derivatives of the Ectoderm
Epidermis, hair, nails, glands of skin
Brain & spinal cord
Neural crest: sensory nerve cells, nervous structures, pigment cells, portions of skeleton, blood vessels in H&N
Major Derivatives of the Endoderm
Epithelial lining and glands of digestive and respiratory tracts
Major Derivatives of the Mesoderm
Vertebrae & ribs
Trunk & limb musculature
Ventral body dermis
CT of limbs
Wall of digestive & respiratory tracts
When does the heart start pumping?
4 weeks to 1 month
When Does Organogenesis Occur?
What occurs during organogenesis?
Stem cell populations established for each organ
MOST gross structural birth defects are induced