Chapter 3.2

Question 1

What is a Teratogen?

Answer 1

Teratogens are substances that interfere with development. Common teratogens are alcohol, prescription drugs, bacteria, viruses, or chemical exposure.

Question 2

From Zygote to Gastrula, what are the stages of development?

Answer 2

1. Zygote
2. 2 Cell embryo
3. 4 Cell embryo
4. 8 Cell embryo
5. 16 Cell embryo
6. Morula
7. Blastula (Blastocyst in mammals)
8. Gastrula

Question 3

What structure does the archenteron eventually develop into?

Answer 3

The gut

Question 4

What structure does the blastopore eventually develop into?

Answer 4

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).

Question 5

What is cell specialization?

Answer 5

Cell specialization is the development of a vast variety of specialized cells in the body from the same genetic information (DNA).

Question 6

What are the three stages of cell specialization?

Answer 6

1. Specification
2. Determination
3. Differentiation

Question 7

What is specification?

Answer 7

Specification is when a cell is reversibly designated to a specific cell type.

Question 8

What is determination?

Answer 8

Determination is when a cell is irreversibly commited to a cell type.

Question 9

What causes cells to undergo determination?

Answer 9

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.

Question 10

What is a morphogen?

Answer 10

A morphogen is a molecule secreted by cells that causes nearby cells to follow a particular development pathway.

Question 11

What is differentiation?

Answer 11

Differentiation is when the cell begins to undergo changes in its structure, function, and biochemistry, to become a specific type of cell.

Question 12

What is the difference between determination and differentiation?

Answer 12

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.

Question 13

What are stem cells?

Answer 13

Stem cells are cells that have not differentiated or cells that give rise to other cells that will differentiate

Question 14

What is potency in the context of stem cells?

Answer 14

The potency of a cell determines the types of cells into which it can differentiate.

Question 15

What are the three levels of potency in stem cells?

Answer 15

1. Totipotent
2. Pluripotent
3. Multipotent

Question 16

What does it mean to be totipotent?

Answer 16

Totipotent cells can differentiate into literally any type of cell, either in the fetus or the placenta. These are the embryonic stem cells.

Question 17

What does it mean to be pluripotent? Example?

Answer 17

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.

Question 18

What does it mean to be multipotent?

Answer 18

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.

Question 19

What are the 4 ways cells can communicate with chemical signals?

Answer 19

1. Autocrine Signaling
2. Paracrine Signaling
3. Juxtacrine Signaling
4. Endocrine Signaling

Question 20

What is autocrine signaling?

Answer 20

Autocrine signaling is when a cell releases a chemical that acts on itself.

Question 21

What is paracrine signaling?

Answer 21

Paracrine signaling is when a cell secretes a chemical that affects the local area of cells around it.

Question 22

What is juxtacrine signaling?

Answer 22

Juxtacrine signaling is when a cell directly activates the receptors of a nearby cell with itself instead of sending out a chemical.

Question 23

What is endocrine signaling?

Answer 23

Endocrine Signaling is when cells secrete hormones that travel through the bloodstream to target a distant tissue.

Question 24

How is apoptosis important in fetal development?

Answer 24

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.

Question 25

What is an apoptotic bleb and what does it become?

Answer 25

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

Question 26

What is necrosis?

Answer 26

Necrosis is when cells die as a result of injury. These cells just leak out their damaged contents instead of packaging them.

Question 27

What is senescence?

Answer 27

Senescence is the scientific term for the loss of integrity of cells over time due to aging.

Question 28

What is a telomere?

Answer 28

The telomere is a segment of DNA at the end of the chromosomes.

Question 29

What is the telomere's function?

Answer 29

Because of the base pairs in the telomere, the telemore keeps the ends of the DNA tight so it doesn't unravel.

Question 30

How do telomeres relate to aging?

Answer 30

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.

Question 31

What does Telomerase do?

Answer 31

Telomerase is an enzyme that re-synthesizes the telomeres at the end of DNA, thereby increasing its longevity.

Question 32

Why is it important that the fetal and maternal blood does not mix?

Answer 32

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.

Question 33

What are the placenta's two functions in fetal development?

Answer 33

1. Provide a permeable barrier across which maternal and fetal nutrients and materials can cross. 2. Protect the baby from pathogens and supply antibodies if necessary.

Question 34

How is fetal circulation different than adult circulation?

Answer 34

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.

Question 35

Name the three fetal shunts?

Answer 35

1. The Foramen Ovale 2. The Ductus Arteriosus 3. The Ductus Venosus

Question 36

Where is the foramen ovale and what is its function?

Answer 36

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

Question 37

Where is the ductus arteriosus and what is its function?

Answer 37

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.

Question 38

How is the pressure in the fetal heart different than in the adult heart?

Answer 38

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.

Question 39

Where is the ductus venosus and what is its function?

Answer 39

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.

Question 40

What are the three steps of childbirth?

Answer 40

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)

Question 41

What two hormones coordinate the contractions of the uterus in childbirth?

Answer 41

Prostaglandins and Oxytocin