Ch 47 Animal Development Flashcards
Three steps of fertilization
1) Sperm penetrate the protective layer around the egg
2) Receptors on the egg surface bind to molecules on the sperm surface
3) Changes at the egg surface prevent polyspermy
Development occurs when during the life cycle of an animal?
At many points
Polyspermy
The entry of multiple sperm nuclei into the egg
In sea urchins, what is triggered when the sperm meets the egg?
An acrosomal reaction
Acrosome
A substance at the tip of sea urchin sperm that releases hydrolytic enzymes that digest that digest material surrounding the egg
The acrosomal process binds to what?
Receptors in the egg in a lock-and-key fashion
Gamete contact and/or fusions serves what two purposes?
1) Depolarizes the egg cell membrane
2) Sets up a fast block to polyspermy
Cortical reaction
A reaction where vesicles beneath the egg plasma membrane release their contents and form and fertilization envelope that acts as a slow block to
polyspermy
Calcium ion released in the cortical reaction activates what?
The egg to increase respiration and protein synthesis
The nuclei of the sperm and egg merge
Fertilization in mammals and other terrestrial animals is internal or external?
Internal
Capacitation
Secretions in the mammalian female productive tract alter sperm motility and structure
What must occur before sperm are able to fertilize an egg?
Capacitation
Is a form of fast block to polyspermy known in mammals?
No.
What triggers a slow block to polyspermy in mammals?
Sperm binding a receptor in the extracellular so a pellucida
Blastomeres
Smaller cells formed by cleavage
Blastula
A ball of cells with a blastocoel
Blastocoel
Fluid-filled cavity of the blastula
In frogs and many other animals, what influences the pattern of cleavage?
The distribution of yolk
The difference in yolk distribution results in what?
Animal and vegetal hemispheres that differ in appearance
Vegetal pole has more or less yolk?
More
Animal pole has more or less yolk?
Less
Holoblastic cleavage
Complete division of the egg
Holoblastic cleavage occurs in what species?
Species whose eggs have little or moderate amounts if yolk
Ex: Sea urchins and frogs
Meroblastic cleavage
Incomplete division of the eggs
Meroblastic cleavage occurs in what species?
Species with yolk-rich eggs
Ex: Reptiles and birds
Morphogenesis
The process by which cells occupy their appropriate locations
Morphogenesis involves what two things?
1) Gastrulation
2) Organogenesis
Gastrulation
The movement of cells from the blastula surface to the interior of the embryo
Germ layers
The three layers produces by gastrulation
Ectoderm (definition)
Forms the outermost germ layer
Endoderm (definition)
Lines the digestive tract
Mesoderm (definition)
Partly fills the space between the endoderm and ectoderm
Each germ layer contributes to what?
Specific structures in the adult animal
The ectoderm gives rise to what?
1) Epidermis of skin and its derivatives (sweat glands, hair follicles)
2) Nervous and sensory systems
3) Pituitary gland, adrenal medulla
4) Jaws and teeth
5) Germ cells
The mesoderm gives rise to what?
1) Skeletal and muscular systems
2) Circulatory and lymphatic systems
3) Excretory and reproductive systems
4) Dermis if skin
5) Adrenal cortex
The endoderm gives rise to what?
1) Epithelial lining if digestive tract and associated organs
2) Epithelial lining if respiratory, excretory, and reproductive tracts
3) Thymus, thyroid, and parathyroid
How much yolk do human eggs have?
Very little
Blastocyst
Human equivalent of the blastula
Topholblast
The outer epithelial layer of the blastocyst
Does the trophoblast contribute to the embryo?
No
What does the trophoblast initiate?
Implantation
What occurs to the trophoblast following implantation?
It continues to expand and a set of extraembryonic membranes is formed
Organogenesis
Process during which various regions of the germ layers develop into rudimentary organs
What two structures form early in vertebrate ogranogenesis?
1) Notochord forms from mesoderm
2) Neural plate forms from ectoderm
Mesoderm lateral to the notochord forms what?
Somites
Somites
Blocks of mesoderm
What occurs laterally to somites?
The mesoderm splits to form the coelom
During organogenesis, what changes cell shape and position?
Reorganization of the cytoskeleton
Apoptosis
Programmed cell death
At various times during development, what happens to indvidual cells, sets of cells, or whole tissues?
They stop growing and are engulfed by neighboring cells
Determination
Describes the process by which a cell or group of cells becomes committed to a particular fate
Differentiation
Refers to the specialization in structure and function resulting from determination
Fate maps
Describe cell differentiation by showing what structures arise from each region
What helps establish the anterior-posterior axis in animals such as chicks?
Gravity
What helps establish the dorsal-ventral axis?
pH differences between the two sides of the blastoderm
In mammals, what may help establish embryonic axis?
Orientation of the egg and sperm nuclei before fusion
Inductive signals play a major role in what?
Pattern formation
Pattern formation
Development of spatial organization
Positional information
Molecular cues that control pattern formation
What tells a cell where it is with respect to the body axes?
Positional information
In the human embryo, ciliary function is essential for what?
Proper specification of cell fate in the human embryo
Monocilia (nonmotile cilia)
Plays roles in normal kidney development in human embryo
Motile cilia
Play roles in left-right specification in human embryo
