Flashcards in Developmental Biology Deck (31):
Rapid mitotic divisions in early embryonic development
What happens to the cell size in cleavage?
-Increasing nuclei to cytoplasm ratio
-Increases gas/nutrient exchange
When does first cleavage occur?
-32 hrs after fertilization
What is the order of development?
Fertilized egg --> 2-cell stage --> 4-cell stage --> 8-cell --> 16 cell --> morula --> blastula --> gastrula
What is the morula?
-Solid ball of embryonic cells
What marks blastulation?
-Morula develops fluid-filled cavity called blastocoel which becomes hollow sphere of cells called blastula
Which cell stage implants in uterus?
What is an ectopic pregnancy?
-When the blastula implants outside the uterus
At what week is the embryo fully implanted?
What is the three-layered structure called?
What does the ectoderm form?
-Integumentary system, lens, retina, nervous sys
What does the endoderm form?
-Epithelial lining of digestive/respiratory tract, liver, pancreas, thyroid, bladder lining
What does the mesoderm form?
-Muscoskeletal system, circulatory system, excretory system, gonads, connective tissue, portions of digestive/respiratory
What is neurulation?
-End of gastrulation
-Regions of germ layers --> rudimentary nervous sys
-Rod of mesodermal cells developing along longitudinal axis of embryo under dorsal layer of ectoderm
What is the inductive effect of the notochord?
-Causes ectoderm to fold in to form groove which forms closed tube --> spinal cord and brain
Neural crest cells
-Cells at top of neural tube that migrate laterally
-Sensory ganglia, autonomic ganglia, adrenal medulla, Schwann cells
What can prevent spina bifida?
-Thin, tough membrane containing amniotic fluid
What develops into the placenta?
What is the chorion?
-Membrane that completely surrounds the amnion
-Assist with transfer of nutrients from mother to fetus
-Develops as outpocketing of gut
-Blood vessels enlarge --> umbilical vessels
What is the function of the umbilical vessels?
-Connect fetus to developing placenta
Site of early development of blood vessels
-Major organ development
-Heart beat at 22 days
-Eyes, gonads, limbs, liver
-Cartilaginous skeleton --> bone
-Face appears human
-Antibodies transported by highly selective active transport
-Growth slows, fetus less active
What are the three stages of labor?
1. Cervix thins and dilate, amniotic sac ruptures
2. Rapid contractions, birth of baby
3. Uterus contracts to expel placenta and umbilical cord
-Chemical and biological agents that can cause congenital disorders
Which plant stems allow for growth in length?
-Apical meristems at tips of roots/stems