Ch 47 Flashcards
When does a human embryo begin to show distinctive features?
5 week
Order of embryonic development (frog) (6)
Zygote
Blastula
Gastrula
Tail-bud embryo (frog)
Larval Stage
Adult
What is the definition for Fertilization?
Formation of diploid zygote from haploid egg and sperm
Sperm ____ the protective layer around the egg
Penetrate
What binds to the molecules on the sperm surface?
Receptors on egg surface
What is Polyspermy?
The entry of multiple sperm nuclei into the egg
What prevents polyspermy
Changes at egg surface
What is triggered when the sperm meets the Egg?
Acrosomal Reaction
What releases hydrolytic enzyme that digest material surround the egg?
Acrosome
What causes fast block to polyspermy
Gamete contact depolarizes the egg cell membrane and causes the blockage
Fusion of egg and sperm initiate which reaction? What does it form?
Cortical Reaction
Forms fertilization envelope
What does the fertilization envelope act as
Slow block to polyspermy
Cortical reaction requires?
High concentration of calcium ion in the egg
What is cortical reaction caused by?
Change in Ca concentration
Spread of Ca correlates with appearance of the fertilization envelope
The rise of Ca in cytosol cause increase of what?
Cellular respiration and protein synthesis by the egg cell
When is an egg activated?
With rapid changes of metabolism (inc cell respiration and protein synthesis)
Where are proteins and mRNA needed for activation come from?
Already present in the egg
Because humans have internal fertilization, sperm must travel through ______ to get to the zone of pellucida
follicle cells
Sperm must travel through a layer of follicle cells surrounding the egg to reach?
The zone pellucida
extracellular matrix of egg
Sperm binding triggers?
Cortical Reaction
Time in mammals for the first cell division?
12-36 hours
What follows after fertilization?
Cleavage: period of rapid cell division without growth
Cleavage partitions the cytoplasm of one large cell into many smaller cells called?
Blastomeres
Ball of cells
Blastula
Blastula fluid filled cavity
Blastocoel
Why is cleavage asymmetric in frogs?
Due to distribution of yolk
Which pole has more yolk?
Vegetal pole
Which pole has less yolk?
Animal pole
The first two cleavage furrows in the frog form?
4 equal blastomeres
What is the third cleavage in a frog like
Forms unequal blastomeres due to yolk in vegetal hemisphere
Complete division of the egg and occurs in species with little/moderate amount of yolk?
Holoblastic Cleavage
Incomplete Division of the egg and occurs in species with lots of yolk?
Meroblastic cleavage
Morphogenesis
The process by which cells occupy their appropriate locations
Gastrulation
Organogensis
The movement of cells from the blastula surface to the interior of the embryo
Gastrulation
The formation of organs
Organogenesis
Gastrulation
Rearranges the cells of a blastula into a three layered embryo called a gastrula
Gastrula
3 layered embyro
Three layers produced by gastrulation?
Germ layers
Ectoderm
outer layer
Endoderm
Digestive tract
Mesoderm
Fill the space between endoderm and ectoderm
Which germ layer gives rise to the epidermis
ectoderm
Which germ layer gives rise to the nervous system and sensory system
ectoderm
Which germ layer gives rise to the pituitary gland
ectoderm
Which germ layer gives rise to the adrenal medulla
ectoderm
Which germ layer gives rise to the jaws and teeth
ectoderm
Which germ layer gives rise to the skeletal and muscular systems
mesoderm
Which germ layer gives rise to the circulatory and lymphatic systems
mesoderm
Which germ layer gives rise to the excretory and reproductive systems
mesoderm
Which germ layer gives rise to the dermis of the skin
mesoderm
Which germ layer gives rise to the adrenal cortex
mesoderm
Which germ layer gives rise to the epithelial lining of digestive tract and associated organs
endoderm
Which germ layer gives rise to the epithelial lining of respiratory, excretory, and reproductive tracts and ducts
endoderm
Which germ layer gives rise to the thymus, thyroid, and parathyroid glands
endoderm
How does frog gastrulation begin?
Begins when a group of cells on DORSAL side of Blastula begin to invaginate
Frog gastrulation process
1) cells move from embryo surface into embryo by involution
2) Becomes endo and mesoderm
3) Cells on embryo surface will form the ectoderm
4) New cavity is called the Archenteron
5) This opens through the blastopore which will become the anus
Prior to gastrulation in chicks the embryo is composed of?
Upper/lower layer
epiblast
hypoblast
Where do the epiblast cells move during gastrulation
Move toward the midline of the blastoderm and then into embryo towards the yolk
Midline thickening forms what?
Primitive streak
Hypoblast role in chick gastrulation
Contribute to the sac that surround the yolk and connection between yolk and embryo
Human equivalent of the blastula
Blastocyst
Cluster of cells at one end of bastocyst
Inner cell mass
Outer epithelial layer of the blastocyst and initiates implantation
trophoblast
Trophoblast continues to expand what is formed?
Extraembryonic membranes
Gastrulation in humans is similar to chick embryo how?
It involves inward movement from epiblast through a primitive streak
Four extra embryonic membranes?
Chorion, Allantois, amnion, Yolk sac
Provide life support system for embryo
Reproduction out of aqueous environments require?
Shelled eggs
or Uterus
Embryos are surrounded by fluid in a sac called?
Amnion
Allows reproduction on dry land
Functions in gas exchange
Chorion
Encloses the amniotic fluid
Amnion
Encloses the yolk
Yolk sac
Disposes of waste products and contributes to gas exchange
Allantois
What process begins the formation of brain and spinal cord?
Neurulation
How does neurulation begin?
Cells from dorsal mesoderm form the notochord
What forms the neural plate?
Signaling molecules secreted by the notochord and other tissues cause the ectoderm above to form neural plate
When cells or tissues cause a developmental change in nearby cells?
Induction
Neural plate curves inward forming the _______?
Creates neural tube
Will become central nervous system
What happens to the notochord?
Disappears before birth but helps contributes to parts of the disks between vertebrae
Where do the neural crest cells develop and migrate along?
It develops along the neural tube of vertebrates and migrate in the body
What does the mesoderm form lateral to the notochord
Somites
What do Somites form?
Form mesenchyme cells form vertebrae, ribs, and muscles
Organogenesis in Chick
Similar to frog
By the time embryo is 3 days old most rudiments of the major egg are apparent
Whats required to help cause cell shape changes or cause a cell to migrate to a new location?
Microtubules and microfilaments of the cytoskeleton are essential to these events
What is the major force in changing cell shape?
Reorganizing the cytoskeleton
How do cells become wedge shaped
Contraction of actin filaments at the apical end of cells
4 examples of Apoptosis
1) tail of tadpoles
2) used to eliminate extra neurons
3) Formation of ventricles of the brain and heart
4) Apoptosis of tissue between digits
Resulting specialization in structure and function
Differentitation
Process by which a cell becomes committed to particular fate
Determination
Cells in multicellular organism share?
The same genome
How are differences in cell types caused?
Result of the expression of different sets of genes
