BIOL-162 (Ch. 47)
Terms in this set (126)
Which end, or pole, of the egg has the highest concentration of yolk?
What structures does each germ layer form? Which germ layer forms muscles? What germ layer forms the digestive tract?
-epidermis of skin and its derivatives (including sweat glands, hair follicles)
-nervous and sensory systems
-pituitary gland, adrenal medulla
-jaws and teeth
-skeletal and muscular systems
-circulatory and lymphatic systems
-excretory and reproductive systems (except germ cells)
-dermis of skin
-add renal cortex
-epithelial lining of digestive tract and associated organs (liver, pancreas)
-epithelial lining of respiratory, excitatory, and reproductive tracts and ducts
-Thymus, thyroid, and parathyroid glands
Fusion of egg and sperm cause release in the egg of an element which causes the cortical reaction (in most animals), what is that element?
Mostly sodium (sometimes calcium)
What is the name for the stage of development that is a three-layered embryo which has developed from a hollow ball of cells?
Name the hollow ball stage of development.
The first organs that develop in chordates are the neural tube and the notochord. What will the neural tube later become?
Brain in head; spinal cord along the rest of the body
What is the name for substances on a cell surface that contribute to the selective association of certain cells with each other?
What is the term that refers to the ability of one cell group to influence the development of another?
What's the term that refers to cells that retain the zygote's potential to form all parts of the animal?
Name the process by which an organism takes its shape and differentiated cells occupy their appropriate locations.
The embryos of reptiles, birds, and mammals develop in a fluid-filled sac called the ___.
How does the animal pole differ from the vegetal pole?
Yolk is more concentrated on vegetal. The animal will grow from the animal pole.
What is the correct developmental sequence, beginning with the zygote?
Zygote -> blastula -> gastrula -> embryo -> fetus
What is the source of the embryonic portion of the mammalian placenta?
Some of the totipotent cells become the placenta.
Describe the fast and slow blood blocks to polyspermy.
Fast: The sperm nucleus enters the egg as ion channels open in the egg's plasma membrane. Sodium ions diffuse into the egg and cause depolarization, a decrease in the membrane potential (about 1-3 seconds).
Slow: Within seconds of sperm binding, cortical granules (vesicles that lie beneath the egg plasma) fuse with the egg plasma membrane and release their contents into the space between the plasma membrane and a surrounding vitelline layer formed by the extracellular matrix of the egg.
Enzymes from the granules trigger a cortical reaction, which lifts the vitelline layer away from the egg and hardens the layer into a protective fertilization envelope. (about 30 seconds)
Differentiate meroblastic and holoblastic cleavage.
Meroblastic: incomplete division of a yolk-rich egg (characteristic of avian development)
Holoblastic: complete division of egg (occurs in eggs with little or moderate amount of yolk)
What do totipotent and pluripotent mean?
Toti: can make anything
Pluri: can only make parts of the body
What's the set order of embryonic development of most animals?
Fertilization: meeting of egg and sperm and chromosomes unite
Cleavage: cell division
Gastrulation: cells start to move inside and form germ layers
Organogenesis: organ formation
What's the cell called after fertilization?
Although animals display widely differing body plans, they share many basic mechanisms of developlent and use a common set of ___.
How does sperm reach the egg's plasma membrane?
It dissolves or penetrates protective layers surrounding the egg.
How is it guaranteed that sperm will fertilize egg of the same species?
Receptors on the egg surface bind to complementary molecules on the sperm surface.
Why do surfaces on the egg change?
To prevent polyspermy, the entry of multiple sperm nuclei into the egg that leads to an abnormal number of chromosomes in the embryo
What's triggered by contact between egg and sperm?
Acrosomal reaction in the sperm
How do the sperm know where to go?
The jelly coat surrounding the egg exudes soluble molecules that attract the sperm, which swim toward the egg.
What happens when the head of a sea urchin sperm contacts the jelly coat of a sea urchin egg?
Molecules in the jelly coat trigger the acrosomal reaction in the sperm.
Hydrolytic enzymes discharged from the acrosome, a specialized vesicle at the tip of the sperm, partially digest the jelly coat.
This enables an acrosomal process to elongate and penetrate the jelly coat.
Protein molecules on the tip of the extended acrosomal process bind to specific receptor proteins that jut out from the egg plasma membrane.
This "lock-and-key" recognition guarantees that sperm and egg are from one species.
Contact between the tip of the acrosomal process and the receptors on the egg leads to the fusion of the sperm and egg plasma membranes.
What happens as ion channels open in the egg's plasma membrane?
The sperm nucleus enters the egg.
What happens within 1-3 seconds?
Sodium ions diffuse into the egg and cause depolarization, a decrease in the membrane potential.
How does this depolarization act as a fast block to polyspermy?
By preventing additional sperm from fusing with the egg's plasma membrane
What happens in about 30 seconds?
Vesicles called cortical granules lie beneath the egg plasma membrane in an area cytoplasm called the cortex.
Within seconds of sperm binding, cortical granules (vesicles that lie beneath the egg plasma) fuse with the egg plasma membrane and release their contents into the space between the plasma membrane and a surrounding vitelline layer formed by the extracellular matrix of the egg.
Enzymes from the granules trigger a cortical reaction, which lifts the vitelline layer away from the egg and hardens the layer into a protective fertilization envelope.
What happens to the remaining receptor proteins and any attached sperm?
They're released as the envelope forms.
How does the envelope contribute to the process?
Together, the fertilization envelope and other changes in the egg's surface impede the entry of additional speed nuclei and thus act as longer-term slow block to polyspermy.
What's required for formation of the fertilization envelope?
A high concentration of calcium ions (Ca2+) in the egg
What controls release of Ca2+ into the cytosol from the endoplasmic reticulum?
A signal transduction pathway activated by sperm binding
What does the resulting increase in Ca2+ levels cause?
Cortical granules to fuse with the plasma membrane in sea urchins and in vertebrates such as fishes and mammals.
How does fertilization lead to activation of the egg?
Fertilization initiates metabolic reactions that trigger the onset of embryonic development, thus "activating" the egg.
What happens to rates of cellular respiration and protein synthesis in the egg following fertilization?
They increase markedly.
What triggers egg activation?
Injecting Ca2+ into an unfertilized egg activates egg metabolism in many species, despite the absence of sperm.
Researchers conclude that the rise in Ca2+ concentration that causes the cortical reaction also causes egg activation.
How is it possible that artificial activation is possible even if the nucleus has been removed from the egg?
Egg activation requires only the proteins and mRNA already present in the egg cytoplasm.
The fast block is basically caused by ___.
The slow block is basically caused by ___.
Concentration of calcium
Why don't other species' eggs impregnate each other?
You only have receptors on your eggs for the sperm of your species.
What marks the end of the fertilization phase?
The first cell division
What's a main difference in the timing of events of sea urchin eggs and human eggs?
Sea urchin eggs have already completed meiosis when they are released from the female.
Human eggs, however, are arrested at metaphase of meiosis II prior to fertilization.
Fertilization of mammals is ___.
What's the process of capacitation?
Secretions in the mammalian female reproductive tract provide a moist environment for the sperm, and alter sperm motility and structure.
Only after these changes occur do sperm have the capacity to fertilize an egg.
In humans, this process occurs during the first 6 hours after the sperm enter the female reproductive tract
What surrounds the mammalian egg and remains with it during and after ovulation?
A sperm must penetrate this layer to reach what?
The zona pellucida, the extracellular matrix of the egg
How does the zona pellucida allow sperm to get through?
The zona pellucida contains a sperm receptor.
Binding of a sperm to this receptor induces an acrosomal reaction, facilitating sperm passage through the zona pellucida to the egg and exposing a protein on the sperm that binds with the egg plasma membrane.
At this point, the two cells fuse.
What does sperm binding do?
Triggers changes in the mammalian egg that lead to a cortical reaction, the release of enzymes from cortical granules outside the cell
What do those enzymes do?
Catalyze changes in the zona pellucida, which then functions as the slow block to polyspermy
Which block to polyspermy has not been identified in mammals?
In mammalian fertilization, what part of the sperm is taken into the egg?
The whole thing
How do the chromosomes come together?
The envelopes of both haploid nuclei disperse and the sperm and egg chromosomes are organized into a single mitotic spindle.
A true diploid nucleus with a nuclear membrane forms only after the first division.
At which end is the yolk concentrated? What's the other end?
Concentrated at vegetal pole
Other end is animal pole
There's no fast block to sperm in mammals. What is there?
A cortical reaction (slow block)
What's the hollow ball stage?
Which developmental stage comes after fertilization?
What characterizes the cleavage stage of early development?
A succession of rapid cell divisions
During cleavage, the cell cycle consists primarily of which phases? Why?
S (DNA synthesis)
Cells skip the G1 and G2 (gap) phases and little or no protein synthesis occurs.
Cleavage partitions the cytoplasm of a large fertilized egg into many smaller cells or ___.
The fist five to seven cleavage divisions produce a hollow ball of cells, the ____, surrounding a fluid-filled cavity called the ___.
Where's the yolk often concentrated?
The difference in yolk distribution results in what?
Animal and vegetal hemispheres that differ in appearance
During cell division, what happens to make the cells separate?
An indentation groove called a cleavage furrow forms in the cell surface as cytokinesis divides the cells in half
Cleavage in amphibian development is ____, because...
Holoblastic because the cleavage furrow passes entirely through the egg
Cleavage in echinoderms, mammals, and annelids is ____.
In animals with little yolk, how are the blastocoel and blastomeres?
The blastocoel forms centrally and the blast omers are of similar size, particularly during the first few divisions.
What kind of development do humans undergo?
Holoblastic (embryo completes three divisions in the first three days after fertilization)
In which animals's eggs is yolk most plentiful and has its most pronounced effect on cleavage?
Birds, other reptiles, many fishes, and insects
What does the great volume of yolk in these animals mean?
The cleavage furrow cannot pass through it.
So what is this cleavage?
Meroblastic: the incomplete cleavage of a yolk-rich egg
In birds, what's the yolk? Where are cell divisions?
The entire egg cell
Cell divisions are limited to a small area at the animal pole.
What do these divisions produce?
A cap of cells that sort into upper and lower layers; the cavity between these two layers is the avian blastocoel
What in animals involve specific changes in cell shape, position, and survival?
What happens after cleavage? What's this called?
Gastrulation, in which a set of cells at or near the surface of the blastula moves to an interior location, cell layers are established, and a primitive digestive tube is formed
How does further transformation occur?
Organogenesis - the formation of organs
Gastrulation and organogenesis are responsible for what?
Morphogenesis - the process by which cells occupy their appropriate locations in the embryo and the animal body takes shape
Gastrulation is what?
Dramatic reorganization of the hollow blastula into a two- or three-layered embryo called a gastrula
The cell layers produced by gastrulation are collectively called what?
The embryonic germ layers
In the late gastrula, what do the ectoderm and endoderm form?
Ectoderm forms outer layer and endoderm lines the embryonic digestive tract
What are cnidarians and a few other symmetrical animals?
Diploblasts (only form 2 germ layers)
What are animals with bilateral symmetry?
Triploblasts, having a third germ layer, the mesoderm, between the ectoderm and endoderm
Most endocrine gland contain what kind of tissue?
What's an example of something that has both ectodermal and mesodermal tissue?
How does gastrula ruin in the sea urchin happen?
Begins at the vegetal pole of the blastula as cells called mesenchyme cells individually detach from the blastocoel
The remaining cells near the vegetal pole flatten slightly and cause that end of the embryo to buckle inward as a result of cell shape changes
The unfolding of a sheet of cells into the embryo
What does the shallow depression develop into?
A deep, narrow, blind-ended tube called the archenteron
What's the open end of the archenteron? What will it become?
Will become anus
When does a second opening form? What will it become?
A second opening, which will become the mouth, forms when the opposite end of the archenteron touches the inside of the ectoderm and the two layers fuse to produce a rudimentary digestive tube
What develops from first opening in protostomes and deuterostomes?
Protostomes: mouth develops from first opening that forms in the embryo
Deuterostomes: mouth forms from second opening
What are echinoderms?
What are chordates?
In frog gastrulation, what's the part above the crease that become the dorsal side of the blastopore called?
In frogs: as the blastopore is forming, a sheet of cells begins to spread out of the animal hemisphere. Some of these cells roll over the edge of the lip into the interior of the embryo. What's this process called?
Once inside the embryo, what do the cells do?
Move away from the blastopore toward the animal pole and become organized into layers of endoderm and mesoderm, with endoderm on the inside
Cells continue to spread over the gastrula surface, doing what to the blastopore?
What happens in the interior of the embryo?
An archenteron forms and grows as the blastocoel shrinks and then disappears.
What happens to the cells remaining on the surface at the end of gastrulation?
They form the ectoderm.
How do the frog's mouth and anus form?
As in the sea urchin, the frog's anus develops from the blastopore and the mouth breaks through at the opposite end of the archenteron.
What are amniotes?
Mammals and reptiles, including birds
Inside the shell or uterus, the embryos of these animals are surrounded by fluid within a sac formed by the amnion.
In chicks, the pileup of cells moving inward at the blastoderm'a midline produced a thickening called what?
The primitive streak
What's the mammalian version of a blastula?
What's the first step of vertebrate organogenesis?
Neurulation, the formation of the brain and spinal cord
Neuralation begins as...
Cells from the dorsal mesoderm come together to form the notochord, a rod that extends along the dorsal side of chordate embryos
Where does the neural plate come from?
Signaling molecules secreted by these mesodermal cells and other tissues induce the ectoderm above the notochord to become the neural plate.
What curves the neural plate inward?
Cells change shape.
What does the neural plate become? Where?
Rolls into the neural tube, which runs along the anterior-posterior acids of the embryo
What does the neural tube become?
The brain in the head and the spinal cord in the rest of the body
In vertebrate embryos, two sets of cells develop near the neural tube and then migrate elsewhere in the body. What are they?
The first set is a band of cells called the neural crest, which develops along the borders where the neural tube pinches off from the ectoderm.
Groups of cells located in strips of mesoderm lateral to the notochord separate into blocks called somites.
What do neural crest cells do?
Migrate throughout the embryo, forming a variety of tissues that include peripheral nerves as well as parts of the teeth and skull bones.
An error in neural tube formation in humans results in what?
Spina bifida, the most common disabling birth defect in the US
What happens in spina bifida?
A portion of the neural tube fails to develop or close properly, leaving an opening in the spinal column and causing nerve damage.
The opening can be surgically repaired shortly after birth, but the nerve damage is permanent and results in varying degrees of paralysis.
In animals, morphogenetic involves the ___ of cells.
Reorganization of _____ changed cell shape during development?
What plays a key role in cell migration by promoting interaction between pairs of cells?
Transmembrane glycoproteins called cell-adhesion molecules
Cell migration also involves the ECM. What is it and what does it do?
The extracellular matrix (ECM), the meshwork of secreted glycoproteins and other macromolecules lying outside the plasma membrane of cells
The ECM helps to guide cells in many types of movements, such as migration of individual cells that shape changes of cell sheets.
Cells that line migration pathways regulate movement of migrating cells by secreting specific molecules into the ECM.
Programmed cell death is a common feature of animal development. During development, individual cells, sets of cells, or whole tissues cease to stop developing and are engulfed by neighboring cells.
What's the tadpole an example of?
In some cases, a structure has a function in a larval form but is eliminated during later development.
What are determination and differentiation?
Determination: process by which a cell or group of cells becomes committed to a particular fate
Differentiation: resulting specialization in structure and function
How do cells acquire different fates?
Particular tissues, and often cells within a tissue, differ from one another by expressing distinct sets of genes from their shared genome.
What are fate maps?
Diagrams showing which organs and other structures arise from each region of an embryo
When is the dorsal-ventral axis of the frog embryo determined?
How does cortical rotation establish the dorsal-ventral axis?
Cortical rotation allows molecules in one portion of the vegetal cortex to interact with molecules in the inner cytoplasm of the animal hemisphere.
Inductive signals play a major role in what?
Pattern formation, the development of an animal's spatial organization, the arrangement of organs and tissues in their characteristic places in three-dimensional space
What's positional information? What does it tell?
The molecular cues that control pattern formation
-tell a cell where it is with respect to the animal's body axes
-help to determine how the cell and its descendants will respond to molecular signaling
YOU MIGHT ALSO LIKE...
MCAT Biology | Kaplan Guide
Ch. 47 - Animal Development
Ch.47 Animal Development
OTHER SETS BY THIS CREATOR
BIOL-330 (Ch. 5)