Biology - Embryology Flashcards
Where does fertilization take place?
Lateral portion of the Fallopian tube.
How many hours after ovulation can an egg be fertilized?
12-24 hours
What is cleavage?
Mitotic division
Does protoplasm change in cleavage?
No. The total volume of cytoplasm remains constant.
What is formed from repeated cleavages?
Smaller cells with increasing nuclear to cytoplasm ratio.
How does the surface to volume ratio change with cleavage?
It increases so has exchange is improved.
What is formed from indeterminate cleavage?
Cells that retain ability to become an organism…..identical twins.
What results from determinate cleavage?
Cells whose future differentiation is determined at early stage.
When does first cleavage of zygote occur?
32 hours after fertilization.
When does 8-felled embryo reach the uterus?
After 3rd cleavage - 72 hours after fertilization.
What is a morula?
Solid ball of embryonic cells.
What is a blastula?
Hollow sphere of cells made from blastulation of the morula.
When is blastula formed?
4 days after fertilization.
When does embryo adhere to uterine wall?
As a blastula.
What is a gastrula?
3 layered structure. (Three germ layers)
What are the 3 layers of a gastrula?
Ectoderm
Endoderm
Mesoderm
What is the ectoderm?
Integumentary, lens of eye, retina, and nervous system.
What is the endoderm?
Epithelial linings of digestive and resp tracts, parts of the liver, pancreas thyroid and bladder.
What is the mesoderm?
Musculoskeletal system, circulatory system, excretory system, connective issues, portions of digestive and resp organs.
Where does embryo of a fish or amphibian develop?
In the egg that is laid in the water?
What is a chorion in an egg?
Inside of the shell….membrane permitting gas exchange.
What is the allantois in an egg?
Saclike structure used for respiration and excretion. Contains blood vessels to transport oxygen, CO2, water and salt and waste.
What is the amnion in an egg?
Membrane enclosing amniotic fluid of an egg.
What is amniotic fluid in an egg?
Aqueous environments that protects embryo from shock.
What is the yolk sac in an egg?
Encloses the yolk. Transfer food to embryo.
Marsupials develop in a placenta?
No. Neither do some tropical fish.
How does has exchange occur in a fetus?
Across the placenta.
Name the 4 extra-embryonic membranes formed during development:
Amnion
Chorion
Allantois
Yolk sac
What is the amnion in placental development?
Thin membrane containing amniotic fluid.
What is the chorion in placental development?
Membrane completely surrounding amnion.
What is the allantois in placental development?
Third membrane. Develops as an out pocketing of the gut.
What does the umbilical cord develop from?
Enlarged blood vessels of the allantoic wall.
What is the yolk sac in placental development?
Site of early development of blood vessels.
3 stages of labor:
Cervix thins and dilates as amniotic sac ruptures.
Rapid contractions
Uterus contracts to expels the placenta and umbilical cord.
What is different about arthropod and mammal maturation?
Arthropods are suspended in pupal stage. Mammals develop uninterrupted.
What is the epicotyl?
Precursor of upper stem and leaves.
What are the cotyledons?
Seed leaves. Dicots have two seed leaves and monocots only have one seed leaf.
What is the hypocotyl?
Develops into the lower stem and root
What is the endosperm?
Grows and feeds the embryo of a plants.
What absorbs the endosperm in dicots?
Cotyledon
What is the seed coat?
Develops from the outer covering of ovule.
What is fruit formed from?
Ovary walls, the flower base and flower pistil
What are meristem cells?
Undifferentiated cells in plants. Activate cell reproductions.
What is the apical meristem?
Tips of rotor and stems. This is where growth in length occurs.
What is the lateral meristem/cambium?
Between xylem and phloem. Permits growth in diameter.
What kind of plants have an active lateral meristem/cambium?
Woody dicots like oaks. (not monocots like grass or herbaceous dicots like alfalfa)
