Intro to Embryology Flashcards
How many cells are present in the morula stage and what are they called?
16-32 Blastomeres
A ball of cells with a fluid filled cavity.
Blastocyst
Embryoblast
The inner cell mass of the blastocyst stage.
The outer cell mass of the Blastocyst
Trophoblast
What is the job of the trophoblast?
To contribute to support tissue, placenta
What happens during the blastocyst stage?
The zona pellucida begins to disintegrate. The blastocyst implants into the uterus between Days 6 and 7
What occurs during week 2 of fertilization?
The blastocyst flattens into a two-layered bilaminar disc which is squeezed between two fluid filled cavities, the amniotic above and yolk sac below.
Cyntotrophoblast
Mitotic inner layer of cells of the trophoblast
Multi-nucleated mass of fused cells in the Trophoblast. This layer secretes the hormone HCG
Synctiotrophoblast
What two outer layers are established during fertilization?
Zona pellucida and the Corona Radiata
Describe the structure of the placenta.
Two layers. The maternal, endometrial lining of the uterus. And the fetal, cytotrophoblast and synctiotrophoblast form the chorion and chorionic cavity of the placenta.
Formation of a three layered embryo consisting of three germ layers.
Gastrulation
What are the three primary germ layers and what do they give rise to?
Ectoderm, Mesoderm, and Endoderm
Neural Tube
A hollow tube that gives rise to most of the CNS. End of the tube closes at days 26 and 28.
Ectoderm cells that fail to be incorporated into the tube, which form a crest around the tube.
Neural Crest
When does the Neural Tube begin to form?
Days 19 to 23.
The cloaca is also known as what?
The future anus
The connecting stalk is known as what?
Future umbilicus
What forms from the ectoderm?
The epidermis and the NS (neural tube and crest)
Forms the primitive connective tissue and mesenchyme between the endoderm and ectoderm.
Mesoderm
The endoderm becomes…
The trachea, bronchi, lungs, liver, gall bladder, and pancreas
Mesoderm differentiates into…
Support tissues (connective tissue, cartilage), muscle, blood, and blood vessels. Also forms the urogenital system.
Coelem
Body cavities, or spaces in the mesoderm
Which system is the first to function?
The cardiovascular system.
When does the heart begin to beat?
Week 4
Blocks of mesoderm which form along the sides of the neural tube.
Somites
How many somites typically form in the embryo?
42 to 44
Somites give rise to…
- Myotome
- Sclerotome
- Dermatome
Skeletal muscles of the back and body wall
Myotome
Sclerotome
Vertebrae and ribs
Dermatome
Dermis of the skin
Pharyngeal Arches
Pouches filled with mesoderm and neural crest cells which mature to form the face and neck.
List events of Week 1 in chronological order.
Fertilization, Rapid Divisions, Morula, Blastula, and Implantation
Bilaminar embryo, yolk sac, amnion, cyto and syncytiotrophoblast formation occur when?
Week 2
What occurs during the embryonic period (Weeks 3-8)?
Gastrulation, Morphogenesis, and Organogenesis
Development of the three germ layers
Gastrulation
Organogenesis
Establishment of organ systems
When is the period of maximum sensitivity?
Embryonic Period (Weeks 3 to 8)
