Chapter 3.2 Flashcards
What is a Teratogen?
Teratogens are substances that interfere with development. Common teratogens are alcohol, prescription drugs, bacteria, viruses, or chemical exposure.
From Zygote to Gastrula, what are the stages of development?
- Zygote
- 2 Cell embryo
- 4 Cell embryo
- 8 Cell embryo
- 16 Cell embryo
- Morula
- Blastula (Blastocyst in mammals)
- Gastrula
What structure does the archenteron eventually develop into?
The gut
What structure does the blastopore eventually develop into?
It depends. If you are an organism known as a deuterosome (humans as an example), the blastopore develops into the anus. If you are a protosome, the blastopore develops into a mouth.
MNEMONIC: In DEUTerosomes, the blastopore is for DOODOO (poop).
What is cell specialization?
Cell specialization is the development of a vast variety of specialized cells in the body from the same genetic information (DNA).
What are the three stages of cell specialization?
- Specification
- Determination
- Differentiation
What is specification?
Specification is when a cell is reversibly designated to a specific cell type.
What is determination?
Determination is when a cell is irreversibly commited to a cell type.
What causes cells to undergo determination?
Cells can undergo determination due to the asymmetric distribution of products during cell division (if one cell gets some proteins and mRNA but the other cell gets different proteins and mRNA, this can cause determination). Determination can also occur in response to the secretion of morphogens.
What is a morphogen?
A morphogen is a molecule secreted by cells that causes nearby cells to follow a particular development pathway.
What is differentiation?
Differentiation is when the cell begins to undergo changes in its structure, function, and biochemistry, to become a specific type of cell.
What is the difference between determination and differentiation?
Determination is when the cell commits to a fate, differentation is when the cell actually starts changing to reach that fate. As an analogy, you are determined to go to be a doctor one day, but you won’t actually start to differentiate into a doctor until you undergo the changes in your knowledge and skill set that await you in medical school and residency.
What are stem cells?
Stem cells are cells that have not differentiated or cells that give rise to other cells that will differentiate
What is potency in the context of stem cells?
The potency of a cell determines the types of cells into which it can differentiate.
What are the three levels of potency in stem cells?
- Totipotent
- Pluripotent
- Multipotent
What does it mean to be totipotent?
Totipotent cells can differentiate into literally any type of cell, either in the fetus or the placenta. These are the embryonic stem cells.
What does it mean to be pluripotent? Example?
Pluripotent cells can differentiate into any cell type in the body but not the cells in the placenta during fetal development. These are the cells in the inner cell mass that turn into the germ layers.
What does it mean to be multipotent?
Multipotent cells are semi-specialized stem cells that can differentiate into multiple cells within a type. For example, hematopoietic stem cells are capable of differentiating into red blood cells, white blood cells, and platelets (blood components), but not skin or nervous cells.
What are the 4 ways cells can communicate with chemical signals?
- Autocrine Signaling
- Paracrine Signaling
- Juxtacrine Signaling
- Endocrine Signaling
What is autocrine signaling?
Autocrine signaling is when a cell releases a chemical that acts on itself.
What is paracrine signaling?
Paracrine signaling is when a cell secretes a chemical that affects the local area of cells around it.
What is juxtacrine signaling?
Juxtacrine signaling is when a cell directly activates the receptors of a nearby cell with itself instead of sending out a chemical.
What is endocrine signaling?
Endocrine Signaling is when cells secrete hormones that travel through the bloodstream to target a distant tissue.
How is apoptosis important in fetal development?
The targeted destruction of cells allows the body to form into its desired shape. This is similar to how a marble sculptor breaks pieces of marble away from the block to make the shape he wants.
What is an apoptotic bleb and what does it become?
When a cell breaks down during apoptosis, it forms apoptotic blebs. These are small membrane bound sacs filled with broken down cell material. Becomes and apoptotic body
What is necrosis?
Necrosis is when cells die as a result of injury. These cells just leak out their damaged contents instead of packaging them.
What is senescence?
Senescence is the scientific term for the loss of integrity of cells over time due to aging.
What is a telomere?
The telomere is a segment of DNA at the end of the chromosomes.
What is the telomere’s function?
Because of the base pairs in the telomere, the telemore keeps the ends of the DNA tight so it doesn’t unravel.
How do telomeres relate to aging?
The special arrangement of base pairs in the telomere is difficult to replicate, and with each new attempted replication of DNA, there is a chance that a portion of the telomere is not replicated. Over time the telomeres shorten and the cell’s DNA is no longer protected. This leads to Senescence.
What does Telomerase do?
Telomerase is an enzyme that re-synthesizes the telomeres at the end of DNA, thereby increasing its longevity.
Why is it important that the fetal and maternal blood does not mix?
Because the fetus can have a different blood type than the mother! This is why all exchange of waste, nutrient, and gas happens across the membrane of the placenta.
What are the placenta’s two functions in fetal development?
- Provide a permeable barrier across which maternal and fetal nutrients and materials can cross.
- Protect the baby from pathogens and supply antibodies if necessary.
How is fetal circulation different than adult circulation?
Lungs and liver don’t play significant roles prior to birth, thus gas exchange occurs at placenta and detox and metabolism are controlled by moms liver.
Because these organs are nonfunctional and structurally weak, the fetus develops shunts to redirect blood away from these fragile organs.
Name the three fetal shunts?
- The Foramen Ovale
- The Ductus Arteriosus
- The Ductus Venosus
Where is the foramen ovale and what is its function?
The foramen ovale is a one way valve that connects the right atrium to the left atrium.
Normally, blood in the right atrium will travel to the right ventricle and then to the lungs.
With this shunt in place, blood in the right atrium travels to the left atrium where the aorta pumps it into the fetus’s systemic circulation.
This shunt allows the blood to bypass the developing lungs and refrain from damaging them.
possible due to right side having higher pressure
Where is the ductus arteriosus and what is its function?
The ductus arteriosus provides a one way shunt from the pulmonary artery to the aorta. Helps bypass lungs
possible due to higher right side pressure
Sometimes a little bit of blood will still be sent to the pulmonary artery, despite the efforts of the foramen ovale. The ductus arteriosus takes whatever blood is in the pulmonary artery and re-routes it to the aorta where it will go to the systemic circulation.
How is the pressure in the fetal heart different than in the adult heart?
In the adult heart, the left ventricle is more muscular, generates more force, and therefore generates more pressure than the right side. In the fetus, the difference between the two ventricles is not as large. In fact, the pressure in the right side of the fetal heart is higher than the pressure in the left side. As the fetus develops, the left ventricle’s relative size difference grows, and the pressure in the left side of the heart rises.
Where is the ductus venosus and what is its function?
The ductus venosus shunts blood returning from the placenta via the umbilical vein directly to a location farther up the inferior vena cava so that it can bypass the liver.
What are the three steps of childbirth?
First, the cervis thins out and the amniotic sac ruptures (Water breaking)
Second, strong uterine contractions result in the birth of the fetus.
Third, the placenta and the umbilical cord are expelled. (afterbirth)
What two hormones coordinate the contractions of the uterus in childbirth?
Prostaglandins and Oxytocin
