Embryogenesis And Development

Question 0

Stage at which implantation occurs

Answer 0

Blastula (blastocyst) stage

Question 1

Ductus arteriosus

Answer 1

A shunt that connects the pulmonary artery to the aorta in order to bypass the fetal lung

Question 2

Stages of development from zygote to gastrula

Answer 2

Zygote -> 2-,4-,8-,16- cell stage -> morula -> blastula -> gastrula

Question 3

Process of neurulation

Answer 3

1. Notochord (rod of mesoderm cells) forms along the long axis of organism
2. Notochord induces overlying ectodermal cells to form neural folds, which surround a neural groove
3. Neural folds fuse to form neural tube (gives rise to CNS)
4. Neural crest cells at tip of each neural fold migrate outward to form PNS

Question 4

Foramen ovale

Answer 4

Connects the right atrium to the left atrium, bypassing the lungs

Question 5

Necrosis

Answer 5

Process of cell death in which a cell dies as a result of injury.
-internal substances can be leaked, causing irritation or an immune response

Question 6

Apoptosis

Answer 6

Cell undergoes changes in morphology and divides itself into many self-contained pieces (apoptotic blebs) which can then be digested by other cells.

• occurs via apoptotic signals or preprogramming
• membranes of blebs prevents the release of potentially harmful substances into the extracellular environment

Question 7

Location of fertilization

Answer 7

Ampulla, the widest part of the Fallopian tube

Question 8

Ductus venosus

Answer 8

Connects the umbilical vein to the inferior vena cava, bypassing the liver

Question 9

Cortical reaction results in…

Answer 9

Release of calcium ions which depolarize the membrane of the ovum, serving two purposes:

• depolarization prevents fertilization by multiple sperm cells
• increased calcium concentration increases metabolic rate of newly formed diploid zygote

Question 10

Third trimester

Answer 10

7th and 8th month: continued rapid growth and further brain development
9th month: antibodies are transported by highly selective active transport from the mother to the fetus for protection against foreign matter in preparation for life outside the womb

Question 11

Umbilical arteries…

Umbilical vein…

Answer 11

Carry deoxygenated blood away from the fetus toward the placenta

Carries oxygenated blood toward the fetus from the placenta

(Oxygenation occurs at the placenta rather than in the fetal lungs)

Question 12

First trimester

Answer 12

~22 days: heart begins to beat, soon after the eyes, gonads, limbs, and liver start to form
5 weeks: embryo is 10 mm in length
6 weeks: grown to 15 mm
7 weeks: cartilaginous skeleton begins to harden into bone
8 weeks: most of the organs have formed, brain is fairly developed, embryo becomes known as a fetus
End of third month: about 9 cm long

Question 13

Birth

Answer 13

Accomplished by rhythmic contractions of uterine smooth muscles, coordinated by prostaglandins and the peptide hormone oxytocin

1. Cervix thins and amniotic sac ruptures
2. Strong uterine contractions result in birth of the fetus
3. Placenta and umbilical cord are expelled (afterbirth)

Question 14

Stem cells potency (greatest to least)

Answer 14

Totipotent > pluripotent > multipotent

Question 15

Makeup of blastocyst

Answer 15

Inner cell mass -> embryoblast -> will become the embryo

Outer cell mass -> trophoblast -> gives rise to the chorion and later the placenta

Question 16

Division of embryo into progressively smaller cells increases two ratios. What are they?

Answer 16

The nuclear-to-cytoplasmic (N:C) ratio & the surface area-to-volume ratio
Thus cells achieve increased area for gas and nutrient exchange to overall volume.

Question 17

Second trimester

Answer 17

• Fetus undergoes a tremendous amount of growth
• Begins to move within the amniotic fluid
• Face takes on a human appearance
• Toes and fingers begin to elongate
• End of sixth month measures 30 to 36 cm long

Question 18

Fetal hemoglobin (HbF)

Answer 18

Has a higher affinity for oxygen than adult hemoglobin (primarily HbA), which also assists in the transfer (and retention) of oxygen into the fetal circulatory system