[Biology] Ch.3: Embryogenesis and Development

Question 1

What happens after sperm penetrate through the cell membrane

Answer 1

A release of calcium ions (cortical reaction)

Question 2

What’s the difference between dizygotic (fraternal) and monozygotic (identical) twins

Answer 2

dizygotic = two different eggs released during one ovulatory cycle, monozygotic = a single zygote splits into two

Question 3

In the process of moving to the uterus for implantation the zygote undergoes [ 1 ] in a process called cleavage

Answer 3

Rapid mitotic cell divisions

Question 4

Does the size of the embryo change during early cleavage

Answer 4

No. The size remains unchanged

Question 5

Explain the difference between indeterminate and determinate cleavage

Answer 5

• Indeterminate = cells that can still develop into complete organisms
• Determinate = results in cells with fates that are already determined (the cells are committed to differentiating into a certain cell type

Question 6

After several divisions the embryo becomes [ 1 ] known as a morula

Answer 6

A solid mass of cells

Question 7

What is a blastula

Answer 7

A hollow ball of cells with a fluid-filled inner cavity (known as a blastocoel)

Question 8

What is the mnemonic to remember what a blastula is

Answer 8

The blastula is an embryo with a blasted-out cavity

Question 9

What is the difference between the trophoblast cells and the inner cell mass

Answer 9

Trophoblast cells surround the blastocoel and gives rise to the chorion and later the placenta whereas the inner cell mass protrudes into the blastocoel and gives rise to the organism itself

Question 10

What does the umbilical cord consist of

Answer 10

Two arteries and one vein encased in a gelatinous substance

Question 11

What is the difference between the substances carried in the umbilical vein and arteries

Answer 11

• Vein = freshly oxygenated blood rich with nutrients from the placenta to the embryo
• Arteries = deoxygenated blood and waste to placenta for exchange

Question 12

What is the allantois

Answer 12

The fluid that serves as a shock absorber during pregnancy and lessens the impact of maternal motion on the developing embryo

Question 13

What is gastrulation

Answer 13

When the cell mass implants and three distinct cell layers are generated

Question 14

What are the three primary germ cell layers from outermost to innermost layer

Answer 14

Ectoderm, mesoderm, and endoderm

Question 15

What does ectoderm give rise it

Answer 15

To integument (including the epidermis, hair, nails, and the epithelial of the nose, mouth, and lower anal canal)

Question 16

What does the mesoderm develop into

Answer 16

Into several different systems including the musculoskeletal, circulatory, and most of the excretory systems

Question 17

What does the endoderm form

Answer 17

The epithelial linings of the digestive and respiratory tracts, including the lungs

Question 18

What would happen if neurulation couldn’t occur

Answer 18

The nervous system wouldn’t be able to develop

Question 19

The notochord is like a [ 1 ]

Answer 19

Primitive spine

Question 20

What are teratogens

Answer 20

Substances that interfere with development, causing defects or even death of developing embryo

Question 21

True or False: teratogens have the same effect on every embryo or fetus

Answer 21

False. They will not have the same effect on every embryo or fetus

Question 22

What are common teratogens

Answer 22

Alcohol, prescription drugs, viruses, bacteria, and environmental chemicals

Question 23

What’s the effect of maternal folic acid deficiency

Answer 23

It may prevent complete closure of the neural tube resulting in spina bifida (parts of the nervous system are exposed to the outside world or covered with a thin membrane)

Question 24

What are morphogens

Answer 24

Molecules that may cause nearby cells to follow a particular development pathway

Question 25

What is the difference between determination and differentiation

Answer 25

- Determination = commitment to a particular cell type | - Differentiation = when a cell produces the products to carry out the function of their cell type

Question 26

What is the difference between totipotent, pluripotent, and multipotent stem cells

Answer 26

- Totipotent = can ultimately differentiate into any cell type - Pluripotent = can differentiate into any cell type except for those found in placental structures - Multipotent = can differentiate into all of the cells within a particular group (ex: hematopoietic stem cells)

Question 27

What’s the difference between autocrine, paracrine, juxtacrine, and endocrine signaling

Answer 27

- Autocrine = signals act on the same cell that secretes the signal - Paracrine = signals act on cells in the local area - Juxtacrine = signals with a cell that’s directly stimulates receptors on an adjacent cell (usually doesn’t involve diffusion) - Endocrine = signals involve secreted hormones that travel through the bloodstream

Question 28

Why doesn’t apoptosis lead to tissue damage the way necrosis does

Answer 28

During apoptosis the cell divides into many self contained pieces called apoptotic blebs that can be digested by other cells but in necrosis internal substances can be leaked, causing irritation of nearby tissues or even an immune response

Question 29

What is senescence

Answer 29

Biological aging that occurs as changes accumulate

Question 30

What is the difference between fetal hemoglobin and maternal hemoglobin

Answer 30

Fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin

Question 31

How does the placenta serve as immune protection

Answer 31

Antibodies crossing the membrane serve a protective function

Question 32

Why does the placenta qualify as an endocrine organ

Answer 32

It produces progesterone, estrogen, and human chorionic gonadotropin (hCG) all of which are essential for maintaining pregnancy

Question 33

The [ 1 ] and [ 2 ] both don’t serve significant functions prior to birth so the fetus constructs shunts to [ 3 ] while they develop

Answer 33

1) lungs 2) liver 3) actively direct blood away from these organs

Question 34

What happens by the end of the first trimester

Answer 34

Most of the organs have formed, the brain is fairly developed, and the embryo is known as a fetus (also, the heart beats)

Question 35

What happens during the second trimester

Answer 35

The fetus undergoes tremendous growth, it begins to move in the amniotic fluid, its face takes on human appearance, and its toes and fingers elongate

Question 36

What’s the relationship between the third trimester and the immune system

Answer 36

Antibodies are transported by highly selective active transport from the mother to the fetus (for protection against foreign mater in preparation for life outside the womb)

Question 37

What are the steps of birth (or parturition)

Answer 37

1. Cervix thins out and amniotic sac ruptures 2. Strong uterine contractions result in birth 3. Placenta and umbilical cord are expelled