Development Flashcards
1
Q
What is development?
A
Development is the events involved in an organism’s gradual changing from a simple to a more complex form.
2
Q
What are the main stages of embryonic development?
A
- Fertilization
- Cleavage
- Gastrulation
- Organogenesis
3
Q
What is the purpose of gastrulation?
A
Gastrulation gives rise to the embryonic cell layers: ectoderm, mesoderm, and endoderm.
4
Q
What happens during organogenesis?
A
Regions of the three embryonic cell layers develop into the rudiments of organs.
5
Q
What is cleavage?
A
Rapid cell division of the zygote to produce the blastula with little growth in mass or size.
6
Q
What is gastrulation?
A
The formation of the germ cell layers and a primitive gut.
7
Q
What is organogenesis?
A
The formation of organs and tissues.
8
Q
What is the blastocoel?
A
A fluid-filled cavity in the center of the blastula.
9
Q
What affects the size of the blastomeres?
A
The way in which the cleavage furrow forms and distributes the yolk affects the size.
10
Q
What does it mean for cellular divisions to be holoblastic?
A
For sea urchins, humans, and frogs, divisions are holoblastic, meaning the cleavage furrow passes entirely through the egg.
11
Q
What does it mean for cellular divisions to be meroblastic?
A
In reptiles, birds, and insects, divisions are meroblastic, meaning the large yolk prevents the cleavage furrows from passing through the entire egg.
12
Q
What are the differences in mitosis during and after cleavage?
A
During cleavage, there is little protein synthesis, cells are reliant on maternal RNA and proteins, and only S phase (DNA synthesis) and M phase (mitosis) occur. After cleavage, significant protein synthesis and growth during the gap (G1 and G2) phases.
13
Q
What is the ectoderm?
A
The outer layer of the gastrula.
14
Q
What is the mesoderm?
A
The layer of the gastrula between the ectoderm and the endoderm.
15
Q
What is the endoderm?
A
The layer of the gastrula that lines the embryonic gut–the archenteron.
16
Q
How do the embryonic germ layers form?
A
- Cells at or near the surface of the blastula move to the interior.
- The three cell layers are established, and the embryo is called a gastrula.
- The cell layers are collectively called the embryonic germ layers.
17
Q
How does gastrulation begin in sea urchins?
A
Mesenchyme cells migrate inward from the vegetal pole, and cells at the vegetal plate buckle inward, causing an invagination.
18
Q
What type of cells form the archenteron in sea urchins?
A
Endodermal cells.
19
Q
What type of cells send out filopodia in sea urchins?
A
Mesenchymal cells.
20
Q
What do filopodia do during gastrulation for sea urchins?
A
Filopodia drag the archenteron across the blastocoel, extending away from the blastopore.
21
Q
What forms the digestive tube in sea urchins?
A
Fusion of the archenteron with the blastocoel wall forms the digestive tube.
22
Q
What are protostomes?
A
Organisms in which the blastopore becomes the mouth
23
Q
What is the blastopore?
A
The point at which invagination happens.
24
Q
What are deuterostomes?
A
Organisms in which the blastopore becomes the anus.
25
What type of organisms are protostomes?
Mollusks, annelids, and arthropods.
26
What type of organisms are deuterostomes?
Echinoderms and chordates (humans, frogs, etc)
27
What is the difference between the animal and vegetal poles?
The vegetal pole has the majority of the yolk and is much denser.
28
How does invagination occur in frogs?
Cells from the animal pole invaginate to form the blastopore.
29
How does gastrulation in frogs begin?
Cells from the animal pole compress the vegetal pole. This causes the dorsal lip of the blastopore to buckle and start pushing some of those cells in.
30
In chicks, what is the embryo formed from?
The epiblast.
31
What forms the sac that surrounds the yolk in chicks?
The hypoblast.
32
How does gastrulation in chicks occur?
A primitive streak forms along the midline of the blastoderm. Epiblast cells migrate inward and down to form the different cell layers.
33
How does gastrulation in humans begin?
The trophoblast (outer layer) implants in the endometrium.
34
What does the inner cell mass divide into during human gastrulation?
The epiblast and the hypoblast.
35
What does the epiblast form during human gastrulation?
The embryo.
36
What does the hypoblast form during human gastrulation?
The yolk sac.
37
After the embryo and yolk sac have formed, what happens next during human gastrulation?
A primitive streak forms and cells of the epiblast invaginate, causing the ectoderm, mesoderm, and endoderm to form.
38
What is the placenta formed from?
Cells from the trophoblast, epiblast, and endometrium.
39
What are the four extraembryonic membranes in a reptile egg?
1. Chorion
2. Allantois
3. Amnion
4. Yolk sac
40
What is the role of the chorion?
In reptiles, gas exchange; in mammals, gas and nutrient transfer. It is the layer of the egg furthest out from the center.
41
What is the role of the amnion?
It encases the fluid that protects the embryo, is important in preventing dehydration, and acts as a shock absorber.
42
What is the role of the allantois?
In reptiles, it disposes of wastes; in mammals, joins the embryo to the mother via the umbilical cord.
43
What is the role of the yolk sac?
In reptiles, it encloses the yolk; in mammals, early formation of blood cells.
44
How does the placenta transfer materials from the mother to the fetus?
Both the mother and child have blood vessels that come in close contact but do not actually exchange blood. However, they are close enough to allow the diffusion of materials.
45
How is labor initiated?
The placenta begins to secrete estradiol, which activates oxytocin receptors in the uterus, causing contractions to begin.
46
What happens when the baby pushes against the top of the cervix?
That induces the baby's and mother's posterior pituitaries to produce oxytocin, telling the uterus to contract and stimulating the placenta to make prostaglandins.
47
What do prostaglandins do?
They induce additional contractions during labor.
48
Prostaglandins act in what type of feedback loop?
Positive feedback. They induce contractions along with feeding back to the posterior pituitary to create more oxytocin and in turn more contractions.
49
What causes monozygotic (identical) twins?
Monozygotic twins are the result of the split of a blastocyst or early-stage embryo.
50
Cells must be what type to create monozygotic twins?
Totipotent or pluripotent.
51
What determines the nature of the placenta in monozygotic twins?
The timing of the split determines the nature of the placenta or placentas.
52
In the case of monozygotic twins, what happens when embryonic division happens prior to implantation?
The embryo divides, splitting into two. As long as the cells are totipotent, both of them will be able to implant into the endometrium. The result is two placentas, two chorion, and two amnions. 30% chance
53
In the case of monozygotic twins, what happens when embryonic division happens during implantation?
There will be one placenta, one chorion, and two amnions. 70% chance. Cells are pluripotentent.
54
In the case of monozygotic twins, what happens when embryonic division happens after implantation?
There will be one chorion and one amnion. Cells are pluripotent.
55
What tissues does the ectoderm give rise to?
1. Epidermis of skin and its derivatives (including sweat glands, hair follicles, etc)
2. Nervous and sensory systems.
3. Pituitary gland, adrenal medulla.
4. Jaws and teeth.
56
What tissues does the mesoderm give rise to?
1. Skeletal and muscular systems.
2. Circulatory and lymphatic systems.
3. Excretory and reproductive systems (except germ cells)
4. Dermis of skin.
5. Adrenal cortex.
57
What tissues does the endoderm give rise to?
1. Epithelial lining of digestive tract and associated organs.
2. Epithelial lining of respiratory, excretory, and reproductive tracts and ducts.
3. Thymus, thyroid, and parathyroid glands.
58
What is gastrulation?
The formation of the germ layers: the ectoderm, mesoderm, and endoderm.
59
When does the notochord perform its function?
The notochord is a structure essential for development, but when the organism is born, the notochord is no longer there.
60
What is the role of the notochord?
The notochord is made of mesoderm, and it sends inductive signals to the ectoderm immediately above it.
61
What is the ectoderm's response to the inductive signals of the notochord?
They begin buckling until they form a structure called the neural plate, which becomes the neural tube.
62
What does the neural tube give rise to?
The central nervous system: brain and spinal cord.
63
What does the neural crest give rise to?
Its cells will migrate to give rise to the peripheral nerves and other tissues.
64
What do the somites give rise to?
They give rise to segmental regions of the body (for example, the ribs).
65
How does the vertebral column form?
It forms where the notochord disintegrates. So, the notochord serves as the placeholder for the backbone.
66
What does the coelum give rise to?
The thoracic cavity.
67
Where does neurulation happen in chicks?
On top of the yolk.
68
What three things do you need for morphogenesis?
1. Cell movement.
2. Changes in cell shape.
3. Cell migration.
69
What happens in convergent extension?
Convergence: adjacent cells elongate and crawl between each other.
Extension: The sheet of cells becomes longer and narrower.
70
What happens during neurulation at the cellular level?
Cells start as cubes and then they extend to become rectangular cells. Microtubule and actin fibers pinch the cells into wedge shapes so that a row of cells can take on a cylindrical shape.
71
What promotes the interaction between cells during cell migration?
Transmembrane glycoproteins called cell adhesion molecules (CAMs) promote the interaction between cells.
72
What is the extracellular matrix (ECM)?
The meshwork of secreted glycoproteins and other molecules that lie outside of the plasma membrane.
73
What dictates the direction in which a cell moves?
The proteins and materials available in the ECM for the cell to grab onto and use as an anchor for movement.
74
In vertebrate animals, apoptosis disposes of what structures?
1. Cells between the future digits.
2. Nerve cells that do not form synapses.
3. Auto-reactive immune cells (this continues throughout adulthood).
4. Structures that are no longer needed (vestigial structures).
75
What is fate mapping, and what does it reveal?
Fate mapping is the process of tracking a cell from embryogenesis until you figure out what it will become. It reveals that differentiated cells can be traced to their origin in the embryo.
76
How many cells does the adult C. elegans have?
959 somatic cells exactly.
77
How many apoptotic events does C. elegans have?
131.
78
What are P granules in C. elegans?
Cells specific to the germ line that will eventually develop into reproductive structures.
79
In many species (but not humans), what does uneven distribution of substances during embryonic development do?
Uneven distribution determines the anterior-posterior axis prior to fertilization.
80
What is the animal pole in fertilized frog eggs made of?
Dark melanin.
81
What is the vegetal pole in fertilized frog eggs made of?
Yellow yolk.
82
Does fertilization happen in the animal or vegetal pole?
Only in the animal pole.
83
What is the gray crescent?
The point at which animal and vegetal pole cells mix.
84
What is cortical rotation?
Cortical rotation occurs when the plasma membrane and cortex rotate toward the point of sperm entry.
85
What axis does the animal pole set?
The anterior-posterior axis.
86
What axis does the gray crescent set?
The dorsal-ventral axis. The gray crescent gives rise to the dorsal side.
87
What happens if cytoplasmic determinants are not properly distributed at the first cleavage?
The totipotency of early embryonic cells is lost.
88
How long is totipotency retained for most mammals?
Until ~8 cell stage.
89
What happens when forced cleavage on a fertilized frog egg is symmetric?
Researchers split the gray crescent, animal, and vegetal poles evenly, resulting in a set of twins.
90
What happens when forced cleavage on a fertilized frog egg is asymmetric?
One cell has ALL the gray crescent, some animal pole, and some vegetal pole, and the other has no gray crescent and only animal and vegetal pole. The cell with the crescent develops normally but the one without does not because it only has ventral structures.
91
What is Spermann's organizer?
This is an experimental technique that transplants the dorsal lip to the other side of another embryo to induce gastrulation on that side as well.
92
Where does the dorsal lip of the blastopore (in the gastrula) come from?
The gray crescent.
93
What happens if Spemann's organizer is used?
It gives rise to conjoined tadpoles that had two dorsal sides.
94
What happens on the molecular level to induce Spermann's organizer?
Chordin and noggin diffuse from the dorsal side to the ventral side. They then inactivate BMP4.
95
What two structures drive wing development in chickens?
In chicks, the apical ectodermal ridge (AER) and the zone of polarizing activity drive wing development.
96
What does AER make?
The apical ectodermal ridge makes fibroblast growth factor and tells the limb to extend.
97
What does the zone of polarizing activity do?
It produces a signal called sonic hedgehog.
98
What does sonic hedgehog determine?
The posterior structures.
99
What happens when a chicken has a ZPA implanted in addition to its own?
It will have posterior structures on both sides.
