Embryology Flashcards
Embryonic period
From fertilization to end of the 8th week of development.
All essential structures for speech and hearing form during this period.
Embryo
Organism in the early stages of growth and differentiation.
Zygote
A new cell formed from the union of the two gametes (egg and sperm). This is a newly fertilized egg. Continues to travel along the filopian tube as it starts to divide (cellular division called mytosis)
Mitosis
The process of the division of the chromosomes and then the division of the cytoplasm to form two new identical cells. Then the 2 cells divide into 4 cells, the 4 cells divide into 8 cells etc…
Morula
About the third day after fertilization. This is when the cell divides into 12 to 16 cells
Blastocyst
(changes from morula to…)When the cells will begin to separate into two masses.around the 5-7 day after fertilization. Implantation is completed after the 10th day.
Outer cell mass (trophoblast)- will become the placenta
Inner cell mass will become the embryo Attaches to the uterine lining
Etopic pregnancy
Egg implants in out of place area- not in uterus . Etopic means out of place…
Week 1
Egg released into filopian tubes, becomes fertilized-occurs in uterine tube 12-24 hrs after ovulation, Zygote, Mitotic cell division, Morula, and Blastocyst.
Week 2
Cell differentiation, Primary germ layers ( ectoderm:upper, Mesoderm: between:, Endoderm cells: lower)
Cell differentiation- what week does it begin?
Begins week 2, cells begin to become different than the one that created it by division.
Primary Germ Layers
Ectoderm: upper
Mesoderm:between
Endoderm:lower
Ectoderm Cells
Upper surface of primary germ layers. Will eventually develop into: Epidermis of the skin Teeth Nervous system Hair Nails Epithelial tissue
Mesoderm cells
Between layer of Primary germ layers.
Will eventually become:
Connective tissue: bones, muscles, blood vessels, cartilage
Endoderm cells
Lower layer of Primary Germ layers.
Eventually becomes:
Epithelial lining of digestive tract “Inner skin”
Epithelial lining of respiratory tract. “inner skin”
Week 3
Will begin to change from a round disk shape to a long tube or pear shape
Primitive Streak
Also referred to as the primitive line. Establishes a structural foundation for change along the longitudinal axis.
Hensen’s Node
Found along the primitive streak. Small area of proliferating cells. (in the bottom area on the diagram)
Neural Plate
Beginning of the nervous system.
Cells grow an thicken to form the neural folds.
Will give rise to all of the neurons and neuroglial cells (supporting cells of the entire nervous system. Then grows upward to form the neural folds.
Notochord
Along the midline of the neural plate- a strip of cells. Will eventually become the primitive axial skeleton.
Neural folds
Thickening along the lateral margins of the neural plate. Meet and fuse in the midline to form a tube.
Neural Tube
Formed when the neural folds meet a the midline and fuse.
WIll give rise to the entire central nervous system.
- brain and spinal chord.
Neural Crest
Ridge of ectodermal cells on either side of the neural tube.
- will become spinal and cranial nerve ganglia and ganglia of the sympathetic and automatic nervous system.
- also known as neural crest of the ganglion ridge.
Somites
Develop as the neural tube is formed. Blocks of tissue that resemble the vertebral column. Appears about the 16th day of development. Three groups: Sclerotome Myotome Dermotome
Sclerotome
Innermost part of a somite.
Will become individual vertebrae, intervertebral discs, and ribs.
