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MCAT Biology > Biology: Chapter 4: Embryogenesis > Flashcards

Biology: Chapter 4: Embryogenesis Flashcards

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1
Q

what is fertilization

A

joining of a sperm and an ovum

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2
Q

where does fertilization occur

A

ampulla of the fallopian tube

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3
Q

What happens when a sperm penetrates the ovum

A

an acrosomal apparatus appears and the sperm injects its pronucleus; calcium is released to prevent other sperm from fertilizing the egg (cortical reaction)

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4
Q

how do fraternal twins happen

A

result from the fertilization of two eggs by two different sperm

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5
Q

how do identical twins happen

A

splitting of the zygote into two

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6
Q

What happens after the first cleavage of the zygote

A

it becomes an embryo as it is no longer unicellular

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7
Q

What is an indeterminate cleavage

A

results in cells that are capable of becoming any cell in the organism

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8
Q

what is determinate cleavage

A

results in cells that are committed to differentiating into a specific type of cell

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9
Q

what is the morula

A

solid mass of cells seen in early development

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10
Q

what is the blastula (blastocyst)

A

has fluid filled center called a blastocoel with two different structures: trophoblast and inner cell mass

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11
Q

what are trophoblasts

A

cells in the blastula that become placental structures

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12
Q

what is the inner cell mass

A

cells in the blastula that becomes the organism

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13
Q

where does the blastula implant

A

the endometrial lining

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14
Q

what is the chorion

A

contains chorionic villi which penetrate the endometrium and create interface between maternal and fetal blood

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15
Q

what supports the embryo before the placenta forms

A

yolk sac

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16
Q

what is the allantois

A

involved in early fluid exchange between the embryo and the yolk sac

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17
Q

what is the amnion

A

lies inside the chorion and produces amniotic fluid

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18
Q

what happens during gastrulation

A

the archenteron is formed with a blastopore at the end; As the archenteron grows through the blastocoel it contacts the opposite side establishing three germ layers

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19
Q

what is the ectoderm

A

becomes the epidermis, hair, nails, the epithelial of the nose and mouth, anal canal, lens of the eye and the nervous system (adrenal medulla)

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20
Q

what is the mesoderm

A

becomes muscloskeletal, circulatory, excretory systems; gives rise to the gonads, muscular and connective tissue layers of digestive and respiratory systems and the adrenal cortex

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21
Q

what is the endoderm

A

becomes epithelial linings of the respiratory and digestive tracts; parts of the pancreas, thyroid, bladder, and distal urinary tracts

22
Q

what happens during neurlation

A

the notocord induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove; the folds fuse to form the neural tube; the tip of each neural fold contains neural crest cells

23
Q

what does the neural tube become

A

CNS

24
Q

what does the neural crest become

A

PNS

25
Q

what are teratogens

A

substances that interfere with development causing defects or death

26
Q

what is determination

A

commitment of the cell to a specific lineage

27
Q

what are morphogens

A

promote development of specific cell line; cell must have competency to respond to morphogens

28
Q

what is differentiation

A

refers to the changes of a cell due to selective transcription to take on appropriate characteristics of cell type

29
Q

what are totipotent stem cells

A

able to differentiate into all cell types; including placental structures and germ layers

30
Q

what are pluripotent stem cells

A

able to differentiate into all three of germ layers and their derivatives

31
Q

what are multipotent stem cells

A

able to differentiate only into a specific subset of cell types

32
Q

what is autocrine signaling

A

signals act on the same cell that released the signal

33
Q

what is paracrine signaling

A

signals acts on local cells

34
Q

what is juxtacrine signaling

A

signals act through direct stimulation of adjacent cells

35
Q

what is endocrine signaling

A

signals act on distant tissues after traveling through circulatory system

36
Q

what are growth factors

A

peptides that promote differentiation and mitosis in certain tissue

37
Q

what is reciprocal induction

A

two tissues both induce further differentiation in each other

38
Q

what is apoptosis

A

programmed cell death

39
Q

what is necrosis

A

cell death as result of an injury

40
Q

why is the placenta important

A

nutrient, gas, and waste exchange through concentration gradients

41
Q

what is fetal hemoglobin

A

has a higher affinity for oxygen to assist the transfer and retention of oxygen into the fetal circulatory system

42
Q

what is the placental barrier

A

serves as immune protection against pathogens and assists in antibody transfer

43
Q

what hormones does the placenta excrete

A

estrogen, progesterone, and human chorionic gonadotropin

44
Q

what are umbilical artieries

A

carries deoxygenated blood to the placenta from the fetus

45
Q

what are umbilical veins

A

carries oxygenated blood from the placenta to the fetus

46
Q

what is the importance of the foreman ovale

A

bypasses the lungs by connecting the right atrium to the left atrium

47
Q

what is the importance of the ductus arteriosus

A

bypasses the lungs by connecting the pulmonary artery to the aorta

48
Q

what is the importance of the ductus venous

A

bypasses the liver by connecting the umbilical vein to the inferior vena cava

49
Q

what is happens during the first trimester

A

organogenesis occurs (heart, eyes, gonads, limbs, liver, some of the brain)

50
Q

what happens during the second trimester

A

tremendous growth, movement begins, the face becomes human, and digits elongate

51
Q

what happens during the third trimester

A

rapid growth and brain development; transfer of antibodies to the fetus

52
Q

what happens during birth

A

1) cervix thins and amniotic sac ruptures
2) uterine contractions coordinated by prostaglandins and oxytocin
3) placenta and umbilical cord are expelled

MCAT Biology (11 decks)

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