Chapter 3: Embryogenesis & Development

Question 1

Where does fertilization occur?

Answer 1

In the ampulla of the falopian tubes

Question 2

What is the name of the structure that penetrates the secondary oocyte’s cell membrane?

Answer 2

Acrosomal apparatus

Question 3

Cortical reaction

Answer 3

Release of Ca2+, that depolarizes the membrane of the ovum, preventing fertilization by another sperm cell, and increase metabolic rate of the zygote.

Question 4

Fertilization membrane

Answer 4

The impenetrable membrane that forms after the cortical reaction has taken place.

Question 5

Dizygotic (fraternal) twins (formation)

Answer 5

Form by the fertilization of 2 different eggs during one ovulatory cycle by 2 different sperm.

Question 6

Monozygotic (identical) twins (formation)

Answer 6

Form when a single zygote splits into two.

Question 7

Indeterminate cleavage

Answer 7

Rapid cell division that results in cells that can still develop into complete organisms.

Question 8

Determinate cleavage

Answer 8

Cell division that results in cells with specific (determinate) fate.

Question 9

Morula

Answer 9

Solid mass of cells that forms after the embryo continues dividing.

Question 10

Blastulation

Answer 10

The formation of the blastula out of the morula. It is a hollow ball of cells with a fluid-filled cavity - blastocoel/blastocyst.

Question 11

Trophoblast cells

Answer 11

Surround the blastocyst and gives rise to the chorion and later, the placenta.

Question 12

Inner cell mass

Answer 12

The region of the blastula that protrudes into the blastocyst and gives rise to the organism itself.

Question 13

Chorion / chorionic villi

Answer 13

Embryonic membrane that later develops into the placenta. As the chorionic villi develop into the placenta, they support maternal-fetal gas exchange.

Question 14

Yolk sac

Answer 14

• Support for the embryo until placenta is formed.
• Site of early blood development
• The umbilical cord is formed from remnants of it and the allantois.

Question 15

Allantois

Answer 15

• Involved in early fluid exchange between the embryo and yolk sac.
• The umbilical cord is formed from remnants of it and the yolk sac.

Question 16

Amnion

Answer 16

Thin, tough membrane filled with amniotic fluid which serves as a shock absorber during pregnancy.

Question 17

Gastrulation

Answer 17

The generation of distinct cell layers which occurs after the cell mass implants.

Question 18

Ectoderm

Answer 18

Outermost layer

Germ layer that gives rise to the integument (hair, skin, nails, epithelia of the nose, mouth, lower anal canal, lens of the eye & the NS including the adrenal medulla!)

attract-o-derm

Question 19

Mesoderm

Answer 19

• Middle layer
• Develops into MSK, circulatory, most of excretory sys, gonads, muscular & connective tissue layers of the digestive and respiratory syst., and the adrenal cortex

means-o-derm

Question 20

Endoderm

Answer 20

• Innermost layer

- Epithelial linings of the digestive & respiratory tracts including the lungs

Question 21

Neurulation

Answer 21

• Development of the NS
• Occurs after the germ layers are formed.
• The notochord induces ectodermal cells to slide inward to form neural folds along the neural groove.
• The neural folds grow toward each other until the neural tube is formed , which gives rise to the CNS.
• Neural crest cells at the tip of the neural folds, migrate outward to form the PNS.

Question 22

Notochord

Answer 22

Rod of mesodermal cells that forms along the axis of the organism, providing a primitive spine.

Question 23

Teratogens

Answer 23

Substances that interfere with development, causing defects or death of the embryo.

Question 24

Determination

Answer 24

The commitment to a specific cell lineage

Question 25

Morphogens

Answer 25

Molecules that promote development down a specific line.

Combinations of multiple morphogens secreted simultaneously result in differentiation of specific cell types.

Question 26

Differentiation

Answer 26

Changes in structure, function, and biochemistry of the cell to match the determined cell type.

Question 27

Totipotent cells

Answer 27

Cells that can differentiate into any cell type, either in the fetus or in the placental structures.

Question 28

Pluripotent cells

Answer 28

Cells that can differentiate into any cell type except for those found in placental structures.

Question 29

Multipotent cells

Answer 29

Cells that can differentiate into multiple types of cells within a particular group.

i.e.: hematopoietic stem cells –> various types of WBCs, RBCs, etc

Question 30

Name 3 concerns about stem cell therapy / immunologic concerns

Answer 30

1. transplanting cells from a different genetic makeup may cause an immune response causing rejection of cells or tissue
2. Pluripotent cells may not always differentiate into the desired tissue
3. Transplanted cells may become cancerous.

Question 31

Autocrine signals

Answer 31

Signals that act on the same cell that secreted the signal.

Question 32

Paracrine signals

Answer 32

Signals that act on cells in the local area.

Question 33

Juxtacrine signals

Answer 33

Signals transmitted via direct stimulation of receptors in an adjacent cell. (Does not require diffusion)

Question 34

Endocrine signals

Answer 34

Signals that involve secreted hormones that travel through the bloodstream to a distant target tissue.

Question 35

Growth factors

Answer 35

Peptides that promote differentiation and mitosis in certain tissues. Most gfs only function on specific cell types or in certain areas.

Question 36

Apoptotic blebs

Answer 36

Self-contained pieces of apoptotic cell remnants that can subsequently be absorbed and digested by other cells.

Question 37

Complete regeneration

Answer 37

Regeneration that allows damaged tissue to be replaced with identical tissues.

Question 38

Incomplete regeneration

Answer 38

Regeneration that results in newly-formed tissue that is not identical to that which is replacing.

Question 39

Placenta

Answer 39

Organ where nutrient, gas and waste exchange occurs.

Also an endocrine organ - produces estrogen, progesterone & hCG.

Question 40

Differences between fetal and adult circulation

Answer 40

1. HbF has greater affinity for oxygen
2. Lungs don’t work / oxygenate blood - 3 shunts to make sure no blood goes into lungs
3. Umbilical arteries carry deoxygenated blood away from fetus toward placenta
4. Umbilical veins carry oxygenated blood from the placenta toward fetus
5. There is a difference in pressure between the right and left sides.

Question 41

Umbilical arteries

Answer 41

Carry blood away from the fetus toward the placenta. Carries deoxygenated blood.

Question 42

Umbilical veins

Answer 42

Carries blood toward the fetus from the placenta. Carries oxygenated blood.

Question 43

Foramen ovale

Answer 43

Connects the RA-LA, bypassing the lungs

Question 44

Ductus arteriosus

Answer 44

Connects the pulmonary artery to the aorta, bypassing the lungs.

Question 45

Ductus venosus

Answer 45

Connects the umbilical vein to the IVC, bypassing the liver.

Question 46

What are the key developmental events that occur during the first trimester of gestation?

Answer 46

Organogenesis occurs (development of heart, eyes, gonads, limbs, liver, brain).

Question 47

What are the key developmental events that occur during the second trimester of gestation?

Answer 47

Tremendous growth occurs, movement begins, the face becomes distinctly human, and the digits elongate.

Question 48

What are the key developmental events that occur during the third trimester of gestation?

Answer 48

Rapid growth and brain development continue, and there is transfer of antibodies to the fetus.

Question 49

What are the main events that occur during birth?

Answer 49

1. The cervix thins out and the amniotic sac ruptures.
2. Uterine contractions, coordinated by prostaglandins and oxytocin, result in birth of the fetus.
3. The placenta and umbilical cord are expelled.