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MCAT > Biology Ch. 3 > Flashcards

Biology Ch. 3 Flashcards

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MCAT flashcards
1
Q

Fertilization occurs in the ____

A

Ampulla of the fallopian tube

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2
Q

The tubular acrosomal apparatus is formed when the ____ and does ____

A

first sperm contacts the secondary oocyte’s cell membrane; it extends into the cell membrane so that the pronucleus can enter the oocyte

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3
Q

What occurs after the penetration of the tubular acrosomal apparatus?

A

A cortical reaction releases calcium ions to depolarize the ovum’s membrane

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4
Q

Why does the ovum’s membrane depolarize after contact with sperm?

A

to prevent further fertilization and increase the metabolic rate of the diploid zygote

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5
Q

Dizygotic/fraternal twins form from ____

A

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

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6
Q

Monozygotic/identical twins form from _____

A

Indeterminate cleavage: a single zygote splitting into two

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7
Q

If a zygote incompletely divides, this forms ____

A

Conjoined twins

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8
Q

Define monochorionic/monoamniotic twins

A

Identical twins that share the same amnion and chorion

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9
Q

Define monochorionic/diamniotic twins

A

Identical twins that share same the chorion but different amnion

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10
Q

Define dichorionic/diamniotic twins

A

Identical twins that have separate amnions and chorions

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11
Q

The ____ of a zygote forms an embryo

A

First cleavage

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12
Q

List the two types of zygotic cleavage

A

1) Indeterminate

2) Determinate

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13
Q

Define indeterminate cleavage

A

results in cells that can develop into complete organisms

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14
Q

Define determinate cleavage

A

results in cells with predetermined fates- will differentiate into a specific cell type

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15
Q

A blastula forms from ___

A

Basculation of the morula

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16
Q

Define morula

A

A solid ball of cells resulting from division of a fertilized ovum, and from which a blastula is formed.

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17
Q

A blastula is compose of ____

A

Blastocoel (fluid-filled cavity)

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18
Q

Define blastocyst

A

Human blastula

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19
Q

Blastulas are composed of ____

A

Blastocoel, inner cell mass, trophoblast

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20
Q

The trophoblast cells will form ____

A

Chorion, then placenta

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21
Q

The inner cell mass will form ____

A

the organism

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22
Q

Chorionic villi form from ____

A

The chorion

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23
Q

Describe the function of chorionic villi

A

Support maternal-fetal gas exchange

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24
Q

Describe the structures and mechanisms involved in fetal-maternal gas exchange

A

The veins of the umbilical cord carry oxygenated blood from the placenta to the embryo

The arteries of the umbilical cord carry deoxygenated blood and water from the embryo to the placenta

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25
Q

Early blood cell development occurs in the ____

A

yolk sac

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26
Q

Describe the function of the yolk sac

A

Supports the embryo until the placenta is functional, is the site of early blood cell development

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27
Q

Define allantois

A

The extraembryonic membrane that is involved in early fluid exchange between the embryo and yolk sac

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28
Q

The umbilical cord is formed from ___

A

The yolk sac and allantois

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29
Q

Define amnion and it’s function

A

It’s a fluid-filled extraembryonic membrane that acts as a shock absorber

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30
Q

Define gastrulation

A

The generation of 3 distinct cell layers

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31
Q

Describe the steps of gastrulation

A
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32
Q

The invagination in the blastula causes __ to merge and forms ___

A

Archenteron membranes merge to form gastrula

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33
Q

The archenteron membranes develop into the ____

A

Gut

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34
Q

The opening of the archenteron is ___

A

the blastopore

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35
Q

In deuterostomes, the blastopore develops into ___

A

the anus

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36
Q

In protostomes, the blastopore develops into ___

A

the mouth

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37
Q

Define primary germ layers

A

3 layers of cells that have migrated into the blastocoel (ectoderm, mesoderm, endoderm)

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38
Q

Define ectoderm

A

The outermost layer that forms integument (i.e. epidermis, hair, nails) epithelia of nose, mouth, and lower anal canal, lens of the eye, nervous system (adrenal medulla) and inner ear

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39
Q

Define mesoderm

A

The middle layer that develops into different systems, including musculoskeletal, circulatory, and excretory systems, in addition to gonads, muscular and connective tissue layers of the digestive and respiratory systems, and adrenal cortex

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40
Q

Define endoderm

A

The innermost layer that forms epithelial linings of digestive and respiratory tracts (i.e. lungs), pancreas, thyroid, bladder, distal urinary tracts, and parts of liver

41
Q

Define spina bifida

A

some or all of spinal cord is open

42
Q

Define anencephaly

A

skull is left open and brain doesn’t develop

43
Q

What causes spina bifida and anencephaly

A

The neural tube doesn’t close

44
Q

Define teratogens

A

substances the interfere with development of the embryo, i.e. alcohol, drugs, viruses, environmental chemicals

45
Q

Overexposure to sugar in utero can cause ____

A

a fetus that is too large to be delivered and suffers form hypoglycemia (due to high levels of insulin synthesized to compensate)

46
Q

What can prevent the complete closure of the neural tube?

A

Maternal folic acid deficiency

47
Q

Define specificiation

A

The initial stage of cell specialization, in which cell is reversibly designated as a specific cell type

48
Q

Define determination

A

The irrevocable commitment of cell to a particular future function and lineage

49
Q

Which is first: specificiation or determination?

A

Specificiation

50
Q

Define morphogens

A

molecules that cause determination to occur

51
Q

Define differentiation

A

The changing of cells structure, function, and biochemistry to match the cell type established during determination

52
Q

Tissues that a stem cell can differentiate into is determined by ____

A

Potency

53
Q

As cells become more differentiated, potency (decreases/increases)

A

Decreases

54
Q

Define totipotent

A

Cells with the greatest potency (i.e. embryonic stem cells)

55
Q

Embryonic stem cells are derived from ___

A

The inner cell mass of a blastocyst

56
Q

Define pluripotent

A

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

57
Q

Pluripotent stems are only formed after ____

A

totipotent cells differentiate into germ cell layers

58
Q

Define multipotent

A

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

59
Q

Hematopoietic cells are cells that can differentiate into any blood cells, but not any other cell type. A hematopoietic cell is an example of what type of cell?

A

Multipotent

60
Q

Define induction

A

The ability of 1 group of cells to influence the fate of nearby cells

61
Q

Induction is mediated by __

A

Inducers

62
Q

Define growth factors

A

peptides that promote differentiation and mitosis in certain tissues

63
Q

Inducers are usually ___

A

Growth factors

64
Q

Define reciprocal development

A

During induction, when cells mutually induce differentiation of one another

65
Q

What ensures that different cell types that work together will remain in proximity to one another

A

Inducers

66
Q

The cell that is induced is called a ___

A

Responder

67
Q

A responder must be ___ to be induced

A

Competent (able to respond to an inducing signal)

68
Q

Define autocrine signal

A

acts on the same cell that secreted first signal

69
Q

Define paracrine signals

A

act on cells in local area

70
Q

Define juxtacrine signals

A

involve a cell directly stimulating receptors of an adjacent cell

71
Q

Define endocrine signals

A

involve secreted hormones that travel through bloodstream to distant target tissue

72
Q

Define apoptotic blebs

A

Self-contained protrusions on a cell about to undergo apoptosis

73
Q

Apoptotic blebs are broken into ___

A

apoptotic bodies

74
Q

Define complete regeneration

A

lost or damaged tissues completely replaced

75
Q

Define incomplete regeneration

A

newly formed tissue is not identical to lost tissue

76
Q

Define senescence

A

biological aging that can occur at cellular and organismal level

77
Q

Define telomerase? What cells is it found on?

A

a reverse transcriptase enzyme that is able to synthesize the ends of chromosomes and prevent senescence; germ, fetal, and tumor cells

78
Q

(Higher/Lower) partial pressure of oxygen in maternal blood than fetal blood allows diffusion of oxygen across placental barrier

A

Higher

79
Q

Define fetal hemoglobin (HbF) and it’s function

A

Fetal blood cells; its greater affinity for O2 assists in the transfer and retention of oxygen in the fetal circulatory system

80
Q

Fetal hemoglobin has a (greater/lesser) affinity for O2

A

Greater

81
Q

The placenta is a __ organ

A

Endocrine

82
Q

List the hormones produced by the placenta

A

Estrogen, progesterone, and hCG

83
Q

Describe the process of fetal detoxification and metabolism

A

Detoxification and metabolism are controlled by the maternal liver, nutrient and waste exchange occurs at placenta

84
Q

The fetal lungs and liver are sensitive to high blood pressures in postnatal life. How does the body respond to thisl?

A

The formation of 3 shunts to direct blood away from the lungs and liver

85
Q

List the 3 fetal shunts

A

1) foramen ovale
2) ductus arteriosus
3) ductus venosus

86
Q

Describe the structure and function of the foramen ovale

A

It’s a one way valve that connects the left and right atria; Allows blood entering right atrium from inferior vena cava to flow into the left atrium instead of right ventricle and therefore directly into the aorta and systemic circulation. It shuts at birth to reverse the pressure differential

87
Q

The ___ side of the heart is at higher pressure in a fetus

A

Right

88
Q

At birth, the ___ is shut to reverse the pressure differential of the fetal hear

A

Foramen ovale

89
Q

Describe the function of the ductus arteriosus

A

shunts leftover blood from pulmonary artery to aorta

90
Q

Describe the function of the ductus venosus

A

shunts blood returning from placenta directly into the inferior vena cava, bypassing the liver

91
Q

How does the liver receive blood?

A

from small hepatic arteries

92
Q

Describe the events of the first trimester

A

Major organs develop, heart beats partway through, eyes, gonads, limbs, and liver form
Cartilaginous skeleton hardens into bone (by 7th week)
Most of organs and much of brain is developed by 8 weeks

93
Q

Describe the major events of the second trimester

A

Movement in amniotic fluid, face takes on appearance, toes and fingers elongate

94
Q

How large is the fetus during the first trimester

A

9cm

95
Q

How large is the fetus during the second trimester

A

30-36 cm

96
Q

Describe the events of the third trimester

A

Rapid growth and brain development initially, followed by slowed growth rate toward end of trimester
Antibodies transported from mother to fetus at highest
Fetus becomes less active

97
Q

Contractions are stimulated by ___

A

prostaglandins and oxytocin

98
Q

Oxytocin is an example of a ____ hormone

A

Peptide

99
Q

Describe the 3 events of parturition

A

1) Cervix thins and amniotic sac ruptures
2) Contractions expel fetus
3) Placental and umbilical are expelled (afterbirth)

MCAT (13 decks)

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