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Biology Kaplan MCAT > Ch. 3: Embryogenesis and Development > Flashcards

Ch. 3: Embryogenesis and Development Flashcards

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1
Q

Fertilization

A

Joining of a sperm and an ovum. After fertilization, zygote must travel to uterus for implantation. If it arrives too late, there will no longer be an endometrium capable of supporting the embryo.

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2
Q

Ampulla

A

Location in the fallopian tube where fertilization occurs, widest part of fallopian tube

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3
Q

Zygote

A

Diploid formed after sperm fertilizes egg

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4
Q

How does the Sperm penetrate into the egg?

A

The sperm uses acrosomal enzymes to penetrate the corona radiata and zona pellucida

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5
Q

Acrosomal apparatus

A

Tubelike structure formed when first sperm comes into direct contact with the secondary oocyte’s cell membrane. This structure extends to and penetrates the cell membrane. Its pronucleus may then freely enter the oocyte once meiosis II has come to completion

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6
Q

Cortical Reaction

A

When the first sperm penetrates, it causes a release of calcium ions, which prevents additional sperm from fertilizing the egg and increases the metabolic rate of the resulting diploid zygote

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7
Q

Fraternal (dizygotic) twins

A

Result from the fertilization of two eggs by two diff sperm. Both zygotes implant in the uterine wall and each develop own placenta, chorion, and amnion. Possible for placenta to overgrow onto each other

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8
Q

Identical (monozygotic) twins

A

Result from the splitting of a zygote in two. Conjoined twins occur when division is incomplete: the following depend on when separation occurred

  • Monochorionic /monoamniotic: share same amnion and chorion
  • Monochorionic/diamniotic: have own amnion but same chorion
  • Dichorionic/diamniotic: have own amnion and chorion
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9
Q

Cleavage

A

Defined as the early divisions of cells in the embryo that happen as the zygote travels to uterus. First cleavage officially creates an embryo These mitotic divisions result in a larger number of smaller cells, as the overall volume does not change. Cells increase 2 ratios: nuclear to cytoplasmic and surface area to volume- thus increased area for gas and nutrient exchange relative to overall volume

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10
Q

When does a zygote become an embryo?

A

After the first cleavage bc it is no longer unicellular

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11
Q

Indeterminate cleavage

A

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

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12
Q

Determinate cleavage

A

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

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13
Q

Morula

A

Several divisions later, solid mass of cells seen in early development

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14
Q

Blastula

A

Once morula is formed, it undergoes blastulation, which forms blastula, mammalian blastula is known as blastocyst; hollow ball of cells which as a has a fluid-filled center called a blastocoel which has 2 diff cell types: 1. Trophoblasts 2. Inner cell mass

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15
Q

Trophoblasts

A

Become placental structures– surround blastocoel and give rise to the chorion and later the placenta

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16
Q

Inner cell mass

A

Becomes the developing organism, protudes into the blastocoel and gives rise to the organism itself

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17
Q

How does the placenta form?

A

The blastula move through the fallopian tube to the uterus where it burros into the endometrial lining . trophoblast cells ae specialized to create an interface between the maternal blood supply and the developing embryo

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18
Q

Chorion

A

Arise from trophoblastic cells, Contains chorionic villi, which penetrate the endometrium and create the interface between maternal and fetal blood. Develops into the placenta. Also forms an outer membrane around the amnion adding an additional level of protection

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19
Q

Yolk Sac

A

Before the placenta is established, the embryo is supported by the yolk sac. Also the site of early blood cell development

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20
Q

Allantois

A

Involved in early fluid exchange between the embryo and yolk sac

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21
Q

Amnion

A

Surrounds allantois, thin tough membrane filled w amniotic fluid, Lies just inside the chorion and produces amniotic fluid which serves as a shock absorber during pregnancy

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22
Q

Umbilical cord

A

ultimately formed from remnants of yolk sac and allantois, Connects the developing organism to the placenta; consists of 2 arteries and one vein encased in a gelatinous substance

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23
Q

Gastrulation

A

Archenteron is formed w a blastopore at the end. As the archenteron grows through the blastocoel it contacts the opposite side, establishing 3 primary germ layers: ectoderm, endoderm, mesoderm (first invagination– imagnine pushing fist through a balloon)

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24
Q

Ectoderm

A

Becomes epidermis, hair, nails, and the epithelia of the nose, mouth and anal canal, as well as the nervous sys (including adrenal medulla) and lens of the eye

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25
Q

Mesoderm

A

Becomes much of the musculoskeletal, circulatory and excretory systems. Mesoderm also gives rise to the gonads and the muscular and connective tissue layers of the digestive and respiratory systems as well as the adrenal cortex

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26
Q

Endoderm

A

Becomes much of the epithelial linings of the respiratory and digestive tracts and parts of the pancreas, thyroid, bladder, and distal urinary tracts

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27
Q

Differentiation

A

Cells with the same genes develop into distinctly diff cell types w highly specialized functions

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28
Q

Selective transcription

A

Process by which differentiation occurs, only the genes needed for a particular cell type are transcribed. Related to the concept of induction

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29
Q

Induction

A

Ability of one group of cells to influence the fate of other nearby cells. Process is mediated by chemical substances called inducers which diffuse from the organizing cells to the responsive cells.

30
Q

Neurulation:

A

Development of the nervous sys, begins after formation of the 3 germ layers (second invagination)

31
Q

Notochord

A

Forms along the long axis of the organism like a primitive spine, Induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove

32
Q

Neural Tube

A

Neural folds fuse to form the neural tube which becomes the central nervous system

33
Q

Neural crest cells

A

The tip of each neural fold contain neural crest cells which become the peripheral nervous system (sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells) as well as specific cell types in other tissues (calcitonin-producing cells of the thyroid, melanocytes in the skin, and others).

34
Q

Teratogens

A

Substances that interfere w development, causing defects or even death of the developing embryo. They include alcohol, certain prescription drugs, viruses, bacteria, and environmental chemicals

35
Q

Maternal Health and Development

A

Maternal health can affect development, including diabetes (increased fetal size and hypoglycemia after birth) and folic acid deficiency (neural tube defects)

36
Q

Determination and differentiation

A

Cell specialization occurs as a result of these processes

37
Q

Specialization

A

Initial stage of cell specialization where cell is reversibly designated to a specific cell type

38
Q

Determination

A

Follows specialization, Commitment to a specific cell lineage, which may be accomplished by uneven segregation of cellular material during mitosis or by morphogens

39
Q

Morphogens

A

Specific molecules secreted from nearby cells which promote development down a specific cell line

40
Q

Competency

A

To respond to a specific morphogen a cell must have competency

41
Q

Differentiation

A

Refers to the changes a cell undergoes due to selective transcription to take on characteristics (structure, function, and biochemistry) appropriate to its cell line

42
Q

Stem cells:

A

Cells that are capable of developing into various cell types, can be classified by potency

43
Q

Totipotent Cells

A

Able to differentiate into all cell types including the 3 germ layers and placental structures

44
Q

Pluripotent Cells

A

Able to differentiate into all 3 of the germ layers and their derivatives

45
Q

Multipotent Cells

A

Able to differentiate only into a specific subset of cell types

46
Q

Cell Communication:

A

Cells communicate through a number of different signaling methods

47
Q

Inducer and Responder

A

An inducer releases factors to promote the differentiation of a competent responder

48
Q

Autocrine Signaling

A

Act on the same cell that released the signal

49
Q

Paracrine Signaling

A

Act on cells in the local area

50
Q

Juxtacrine Signaling

A

Act through direct stimulation of the adjacent cells

51
Q

Endocrine Signaling

A

Act on distant tissues after traveling through the bloodstream

52
Q

Growth factors

A

Autocrine Signals, Paracrine Signals, Juxtacrine Signals, Endocrine Signals are often growth factors which are peptides that promote differentiation and mitosis in certain tissues

53
Q

Reciprocal induction

A

Two tissues both induce further differentiation in each other

54
Q

Signaling often occurs

A

Via gradients

55
Q

Cells may need to

A

Migrate to arrive @ their anatomically correct location

56
Q

Apoptosis

A

Programmed cell death via the formation of apoptotic blebs. Can be used for sculpting certain anatomical structures, such as removing the webbing between digits

57
Q

Apoptotic Blebs

A

Can be absorbed and digested by other cells

58
Q

Regenerative capacity

A

Ability of an organism to regrow certain parts of the body. The liver has high regenerative capacity, while the heart has low regenerative capacity

59
Q

Senescence

A

Result of multiple molecular and metabolic processes; most notably, the shortening of telomeres during cell division

60
Q

What processes occur at the placenta?

A
  • Nutrient, gas, and waste exchange occurs @ the placenta
  • Oxygen and CO2 are passively exchanged due to concentration gradients
  • serves endocrine functions: secreting estrogen, progesterone, and human chorionic gonadotropin (hCG)
61
Q

Fetal Hemoglobin (HbF)

A

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 sys

62
Q

Placental Barrier

A

Among other functions, servers as immune protection against many pathogens, and antibodies are transferred from mother to child

63
Q

Umbilical arteries

A

Carry deoxygenated blood from the fetus to the placenta

64
Q

Umbilical vein

A

Carries oxygenated blood from the placenta back to the fetus

65
Q

How does the fetal circulatory system differ from its adult version?

A

Fetal circulatory sys has 3 shunts: foramen ovale, ductus arteriosus, ductus venosus

66
Q

Foramen Ovale

A

Connects the right atrium to the left atrium bypassing the lungs

67
Q

Ductus arteriosus

A

Connects the pulmonary artery to the aorta, bypassing the lungs

68
Q

Ductus venosus

A

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

69
Q

First trimester

A

Organogenesis occurs– development of heart, eyes, gonads, limbs, liver, brain

70
Q

Second trimester

A

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

71
Q

Third trimester

A

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

72
Q

Birth

A

The cervix thins out and the amniotic sac ruptures. Then, uterine contractions, coordinated by prostaglandins and oxytocin, result in birth of the fetus. Finally, the placenta and umbilical cord are expelled.

Biology Kaplan MCAT (12 decks)

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