Flashcards in Embryology (Ch 3) Deck (19):
What are the three stages of development?
1. Pre-Embryonic Development (weeks 1-2)
2. Embryonic Development (weeks 3-8)
3. Fetal Development (weeks 9-birth)
--> first two weeks after fertilization
1. fertilization (zygote)
2. cleavage: zygote (one cell) -> morula (16 cells)
3. morula takes up fluid --> blastocyst (hollow ball w/two cell types)
4. blastocyst implants into uterine wall
5. blastocyst differentiates into two laters (bilaminar disc)
series of mitotic divisions that causes zygote to break into 16 cells called the morula
hollow ball of two cell types
1. Inner Cell Mass: develops into embryo
2. Outer Ring of cells (trophoblast): develops into placenta
two layers of the blastocyst
-gastrulation (bilaminar disc-->trilaminar disc)
-blastocyst cells form the 3 germ layers
-primitive streak (raised groove) appears onto of embryo
-epiblast cells begin to migrate inward at primitive streak --> become endoderm
What is gastrulation?
--> process by which the cells of the epiblast migrate and form the three primary germ layers
(bilaminar --> trilaminar)
1. formation of primitive streak
2. cells travel up streak forming three layers
What are the three germ layers?
1. Ectoderm (outer)
2. Mesoderm (middle)
3. Endoderm (inner)
What are parts of the ectoderm?
epidermis, nervous tissue, pituitary gland, tooth enamel
What are parts of the mesoderm?
notochord, heart, kidney, skeleton, muscles, dermis
What are parts of the endoderm?
linings of digestive/respiratory tract, liver, pancreas, thyroid
What are the subdivisions of the mesoderm?
1. Notochord: central axis of embryo in adult
2. Lateral Plate Mesoderm
3. Intermediate Mesoderm
4. Paraxial Mesoderm
Somites and their subdivisions
block-like early body segments formed from paraxial mesoderm (become axial skeleton, muscle, cartilage, dermis, and connective tissue)
1. Sclerotome: become vertebrae and ribs
2. Myotome: becomes limb/trunk muscles
3. Dermatome: becomes dermis layer of skin
What is the notochord?
cylindrical mass of mesoderm becomes central axis in adults --> signals ectoderm to form neural tube (brain/spinal cord) (aka NEURULATION)
--> week 9 to birth
-period of rapid growth/maturation of organs
when the three germ layers have been formed
all organs present in some rudimentary form