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MCAT > Biology Ch. 3 > Flashcards

Biology Ch. 3 Flashcards

(99 cards)

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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
Early blood cell development occurs in the ____
yolk sac
26
Describe the function of the yolk sac
Supports the embryo until the placenta is functional, is the site of early blood cell development
27
Define allantois
The extraembryonic membrane that is involved in early fluid exchange between the embryo and yolk sac
28
The umbilical cord is formed from ___
The yolk sac and allantois
29
Define amnion and it's function
It's a fluid-filled extraembryonic membrane that acts as a shock absorber
30
Define gastrulation
The generation of 3 distinct cell layers
31
Describe the steps of gastrulation
32
The invagination in the blastula causes __ to merge and forms ___
Archenteron membranes merge to form gastrula
33
The archenteron membranes develop into the ____
Gut
34
The opening of the archenteron is ___
the blastopore
35
In deuterostomes, the blastopore develops into ___
the anus
36
In protostomes, the blastopore develops into ___
the mouth
37
Define primary germ layers
3 layers of cells that have migrated into the blastocoel (ectoderm, mesoderm, endoderm)
38
Define ectoderm
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
39
Define mesoderm
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
40
Define endoderm
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
Define spina bifida
some or all of spinal cord is open
42
Define anencephaly
skull is left open and brain doesn’t develop
43
What causes spina bifida and anencephaly
The neural tube doesn't close
44
Define teratogens
substances the interfere with development of the embryo, i.e. alcohol, drugs, viruses, environmental chemicals
45
Overexposure to sugar in utero can cause ____
a fetus that is too large to be delivered and suffers form hypoglycemia (due to high levels of insulin synthesized to compensate)
46
What can prevent the complete closure of the neural tube?
Maternal folic acid deficiency
47
Define specificiation
The initial stage of cell specialization, in which cell is reversibly designated as a specific cell type
48
Define determination
The irrevocable commitment of cell to a particular future function and lineage
49
Which is first: specificiation or determination?
Specificiation
50
Define morphogens
molecules that cause determination to occur
51
Define differentiation
The changing of cells structure, function, and biochemistry to match the cell type established during determination
52
Tissues that a stem cell can differentiate into is determined by ____
Potency
53
As cells become more differentiated, potency (decreases/increases)
Decreases
54
Define totipotent
Cells with the greatest potency (i.e. embryonic stem cells)
55
Embryonic stem cells are derived from ___
The inner cell mass of a blastocyst
56
Define pluripotent
Cells that can differentiate into any cell type except for those found in placental structures
57
Pluripotent stems are only formed after ____
totipotent cells differentiate into germ cell layers
58
Define multipotent
cells that can differentiate into multiple types of cells within a particular group
59
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?
Multipotent
60
Define induction
The ability of 1 group of cells to influence the fate of nearby cells
61
Induction is mediated by __
Inducers
62
Define growth factors
peptides that promote differentiation and mitosis in certain tissues
63
Inducers are usually ___
Growth factors
64
Define reciprocal development
During induction, when cells mutually induce differentiation of one another
65
What ensures that different cell types that work together will remain in proximity to one another
Inducers
66
The cell that is induced is called a ___
Responder
67
A responder must be ___ to be induced
Competent (able to respond to an inducing signal)
68
Define autocrine signal
acts on the same cell that secreted first signal
69
Define paracrine signals
act on cells in local area
70
Define juxtacrine signals
involve a cell directly stimulating receptors of an adjacent cell
71
Define endocrine signals
involve secreted hormones that travel through bloodstream to distant target tissue
72
Define apoptotic blebs
Self-contained protrusions on a cell about to undergo apoptosis
73
Apoptotic blebs are broken into ___
apoptotic bodies
74
Define complete regeneration
lost or damaged tissues completely replaced
75
Define incomplete regeneration
newly formed tissue is not identical to lost tissue
76
Define senescence
biological aging that can occur at cellular and organismal level
77
Define telomerase? What cells is it found on?
a reverse transcriptase enzyme that is able to synthesize the ends of chromosomes and prevent senescence; germ, fetal, and tumor cells
78
(Higher/Lower) partial pressure of oxygen in maternal blood than fetal blood allows diffusion of oxygen across placental barrier
Higher
79
Define fetal hemoglobin (HbF) and it's function
Fetal blood cells; its greater affinity for O2 assists in the transfer and retention of oxygen in the fetal circulatory system
80
Fetal hemoglobin has a (greater/lesser) affinity for O2
Greater
81
The placenta is a __ organ
Endocrine
82
List the hormones produced by the placenta
Estrogen, progesterone, and hCG
83
Describe the process of fetal detoxification and metabolism
Detoxification and metabolism are controlled by the maternal liver, nutrient and waste exchange occurs at placenta
84
The fetal lungs and liver are sensitive to high blood pressures in postnatal life. How does the body respond to thisl?
The formation of 3 shunts to direct blood away from the lungs and liver
85
List the 3 fetal shunts
1) foramen ovale 2) ductus arteriosus 3) ductus venosus
86
Describe the structure and function of the foramen ovale
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
The ___ side of the heart is at higher pressure in a fetus
Right
88
At birth, the ___ is shut to reverse the pressure differential of the fetal hear
Foramen ovale
89
Describe the function of the ductus arteriosus
shunts leftover blood from pulmonary artery to aorta
90
Describe the function of the ductus venosus
shunts blood returning from placenta directly into the inferior vena cava, bypassing the liver
91
How does the liver receive blood?
from small hepatic arteries
92
Describe the events of the first trimester
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
Describe the major events of the second trimester
Movement in amniotic fluid, face takes on appearance, toes and fingers elongate
94
How large is the fetus during the first trimester
9cm
95
How large is the fetus during the second trimester
30-36 cm
96
Describe the events of the third trimester
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
Contractions are stimulated by ___
prostaglandins and oxytocin
98
Oxytocin is an example of a ____ hormone
Peptide
99
Describe the 3 events of parturition
1) Cervix thins and amniotic sac ruptures 2) Contractions expel fetus 3) Placental and umbilical are expelled (afterbirth)

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