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MCAT Bio > Bio #3 > Flashcards

Bio #3 Flashcards

1
Q

all embryos are ____ by default but then the ______ gene produces ______. This occurs around _____ post-fertilization.

A

female
SRY
masculinization
6-8 weeks post-fertilization

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2
Q

fertilization

A

Occurs in the widest part of the fallopian tube called the ampulla.
o Sperm releases acrosomal enzymes that allow it to get through the corona radiata and the zona pellucida.
o First sperm to come in contact with the secondary oocyte’s cell membrane forms a tube-like acrosomal apparatus which extends and penetrates the cell membrane.
 Sperm pronucleus then enters the oocyte after meiosis II
o Cortical reaction: release of calcium ions after the sperm penetrates the cell membrane.
 The depolarization that occurs does not allow the egg to be fertilized by another sperm cell and it increases the metabolic rate of the newly formed zygote.
 Fertilization membrane: depolarized and impenetrable membrane.
o Twins
 Dizygotic (fraternal) twins: fertilization of two different eggs released during one ovulatory cycle by two different sperm.
• Each develops own placenta, chorion, and amnion.
 Monozygotic (identical) twins: when a single zygote splits into two.
• Conjoined twins: result of incomplete division, two offspring are physically attached.
• Specific label depends on when they split.
• The more shared gestational structures the more risks are apparent as the fetus grows.

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3
Q

what are the steps of embryogenesis

A
  1. fertilization
  2. cleavage
  3. blastulation
  4. gastrulation
  5. differentiation
  6. neurulation
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4
Q

where does fertilization occur?

A

Occurs in the widest part of the fallopian tube called the ampulla.

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5
Q

sperm releases _______ that allow it to get through the corona radiata and the zona pellucida.

A

acrosomal enzymes

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6
Q

First sperm to come in contact with the secondary oocyte’s cell membrane forms a tube-like _____ which extends and penetrates the cell membrane.
The sperm pronucleus then enters the oocyte after ______ is complete.

A

acrosomal apparatus

meiosis II

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7
Q

cortical reaction

A

release of calcium ions after the sperm penetrates the cell membrane.
 The depolarization that occurs does not allow the egg to be fertilized by another sperm cell and it increases the metabolic rate of the newly formed zygote.
 Fertilization membrane: depolarized and impenetrable membrane.

The calcium ions are held in cortical granules right inside of the secondary oocyte/mature ovum.

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8
Q

dizygotic twins

A

(fraternal) twins: fertilization of two different eggs released during one ovulatory cycle by two different sperm.
• Each develops own placenta, chorion, and amnion.

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9
Q

monozygotic twins

A

(identical) twins: when a single zygote splits into two.

characterized by what structures they share (chorion or amnion).

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10
Q

conjoined twins

A

result of incomplete division, two offspring are physically attached.

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11
Q

the _____ has the greatest nucleus to cytoplasm ratio

A

blastula

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12
Q

neural tube is _______ and the notocord is ______

A

ectodermal

mesodermal

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13
Q

need ____ to make adult stem cells pluripotent

A

transcription factors

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14
Q

imperforate anus is formed when there is not proper _______ in the digestive tract

A

apoptosis

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15
Q

_____ in the fetus are very sensitive and mature very late

A

lung tissues

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16
Q

cleavage

A

step 1
o Cleavage: the zygote undergoes rapid mitotic cell divisions.
 Indeterminate cleavage: cells that can still develop complete organisms or any cell type.
 Determinate cleavage: results in cells with fates that are already determined. They are committed to differentiating into a certain cell type. One path.
o Zygote must get to uterus in time so there is an endometrium still capable of supporting the embryo.
o First cleavage creates unicellularity.
o Divisions into smaller cells gives: increase the nuclear to cytoplasmic ration and the surface area to volume ratio (increased area for gas and nutrient exchange).

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17
Q

cleavage

A

step 2
o Cleavage: the zygote undergoes rapid mitotic cell divisions.
 Indeterminate cleavage: cells that can still develop complete organisms or any cell type.
 Determinate cleavage: results in cells with fates that are already determined. They are committed to differentiating into a certain cell type. One path.
o Zygote must get to uterus in time so there is an endometrium still capable of supporting the embryo.
o First cleavage creates unicellularity.
o Divisions into smaller cells gives: increase the nuclear to cytoplasmic ration and the surface area to volume ratio (increased area for gas and nutrient exchange).

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18
Q

indeterminate cleavage

A

cells that can still develop complete organisms or any cell type.

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19
Q

determinate cleavage

A

results in cells with fates that are already determined. They are committed to differentiating into a certain cell type. One path.

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20
Q

cleavage allows for _____

A

o Divisions into smaller cells gives: increase the nuclear to cytoplasmic ration and the surface area to volume ratio (increased area for gas and nutrient exchange).

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21
Q

blastulation

A

step 3
morula ==> blastocyst ==> implantation

 Blastula moves to uterus and burrows into the endometrium.
 Trophoblasts connect the embryo to the maternal blood supply.
• Trophoblasts give rise to the chorion: an extraembryonic membrane that develops into the placenta.
• Trophoblasts form chorionic villi: microscopic fingerlike projections that penetrate the endometrium.
o Support maternal-fetal gas exchange

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22
Q

umbilical cord

A

connects the embryo to the placenta, consists of two arteries and one vein encased in gelatinous substance.
• Vein: oxygenated blood
• Arteries: deoxygenated blood and waste to placenta.

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23
Q

yolk sac

A

the site of early blood development that supports the embryo until the placenta is functional.

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24
Q

allantois

A

involved in early fluid exchange between the embryo and the yolk sac
o Umbilical cord is formed from allantois and yolk sac

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25
amnion
surrounds the allantois, thin, tough membrane filled with amniotic fluid. o Shock absorber during pregnancy
26
chorion
develops into the placenta | forms another outer layer around the amnion.
27
the umbilical cord is formed from the _____
allantois and yolk sac
28
gastrulation
step 4 after the cell mass implants, can begin more developmental processes such as the generation of three distinct cell layers. o Gastrula: results after invagination, poke finger into balloon and then the outer membrane comes together.
29
archenteron
the membrane invagination into the blastocoel, later develops into the gut.  Blastopore: opening of the archenteron • Deuterostomes: the blastopore is the anus • Protostomes: the blastopore is the mouth
30
what are the primary germ layers
ectoderm mesoderm endoderm
31
what does the ectoderm give rise to?
outermost layer • Gives rise to the integument: epidermis, hair, nails, epithelia of nose, mouth, and lower anal canal. Lens of the eye, nervous system (adrenal medula too) and inner ear.
32
what does the mesoderm give rise to?
the middle layer Means of gettering around: bones and muscle, sleeping around, around the body circulatory system • Gives rise to the musculoskeletal, circulatory, and most of the excretory systems. Gives rise to the gonads, muscular and connective tissue layers of the digestive and respiratory systems and the adrenal cortex.
33
what does the endoderm give rise to?
innermost layers Linings of endernal, digestive and respiratory tract • Gives rise to the epithelial linings of the digestive and respiratory tracts, including the lungs. • Also the pancreas, thyroid, bladder, distal urinary tracts, and parts of the liver.
34
differentiation
step 5 o Selective transcription: of the genome allows it, certain genes are turned on o Induction: the ability of one group of cells to influence the fate of nearby cells.  Inducers: chemical substances that diffuse from organizing cells to responsive cells.
35
induction
the ability of one group of cells to influence the fate of nearby cells.
36
inducers
chemical substances that diffuse from organizing cells to responsive cells that influence the fate of responsive cells.
37
neurulation
step 6 o Neurulation: development of the nervous system, after the 3 germ layers are established. o First the notochord forms from mesoderm cells. o The notochord induces ectodermal cells to slide inward to form neural folds, which surround a neural groove. o Neural folds grow toward one another to form the neural tube, gives rise to the central nervous system. o Neural crest cells: at the tip of each neural groove.  Migrate to form the peripheral NS (sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells) and other stuff (melanocytes in skin) o Ectodermal cells migrate over the neural tube and crest to cover the rudimentary NS.
38
the _____ induces ectodermal cells to slide inward to form ______ and eventually the ______
notochord neural folds neural tube
39
neural crest cells and what they become
at the tip of each neural groove.  Migrate to form the peripheral NS (sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells) and other stuff (calcitonin producing cells of the thyroid, melanocytes in skin)
40
teratogens
substances that interfere with development, causing defects or even death of the developing embryo.  Ex: alcohol, drugs, viruses, bacteria, and environmental chemical  Overall effects depend on genetics of fetus and exposure levels.
41
cell specialization
o In order to create an organism as complex as the human, each cell must perform a specialized function and the cells must be organized so that the organ can function properly.
42
specification
the cell is reversibly designated as a specific cell type
43
determination
the commitment of a cell to a particular function in the future. Irreversibly committed to a specific cell lineage. Happens in a couple ways: • Unequal distribution of existing mRNA and protein during cleavage • Secretion of morphogens (molecules) from nearby cells. • Commitment to particular cell type, but the cell has not produced what it needs to to carry out the function of that cell type yet.
44
differentiation
changing the cell’s structure, function, and biochemistry to match the cell type it has been determined to be.
45
stem cells
cells that have not yet differentiated or that give rise to other cells that will differentiate. they exist in both embryonic and adult tissue
46
potency
determines the types of tissues a particular stem cell can differentiate into.
47
totipotent
have the greatest potency, can differentiate into any cell type either in the fetus or the placental structures.
48
pluripotent
cells can differentiate into any cell type except for those found in the placental structures.
49
multipotent
cells that can differentiate into multiple cells types within a particular group. o Example: hematopoietic stem cells: can differentiate into any blood cell type but not neurons, muscle cells, etc.
50
Research on embryonic stem cells
• Research into ES cells and also using multipotent stem cells, inducing potency via addition of transcription factors, and then putting them back into patients to try and regrow lost tissue.
51
The determination and differentiation of a cell depends on the ______ of the cell as well as well as the _______ of the surrounding cells.
location | identity
52
inducer
cell that sends signal
53
responder
cell that receives signal | receiver cells must be Competent: the responder cell must be able to receive the signal.
54
what are the different signals for cell-cell communication
autocrine paracrine juxtacrine endocrine
55
autocrine signals
act on the same cell that secreted the signal in the first place.
56
paracrine signals
act on cells in the local area
57
juxtacrine signals
do not usually involve diffusion, but involve a cell directly stimulating receptors on an adjacent cell
58
endocrine signals
secreted hormones that travel through the bloodstream to a distant target tissue.
59
growth factors
inducers | peptides that promote differentiation and mitosis of certain tissues.
60
reciprocal development
something that gets induced then induces something else (the same thing that originally induced it).
61
morphogens
use gradients to induce, diffuse throughout the organism. • Depending on the concentration of the morphogen, it will induce a specific response by the cell. Many different morphogens at once can result in highly specific differentiation (specific signal being received by groups of cells).
62
cell migration
 Cells must be able to detach from where they are and migrate to parts of the body to function properly.
63
cell death
 Apoptosis: programmed cell death • Can occur via apoptotic signals or preprogramming • Ex: our fingers are webbed and then the webbing undergoes apoptosis resulting in separation of the fingers. • The cell divides into apoptotic blebs, which can then be broken apart into apoptotic bodies and digested by other cells. o Digested by other cells so harmful chemicals are never released.  Necrosis: cell death as a result of injury and internal substances are leaked which can cause irritation of nearby tissues.
64
apoptosis
programmed cell death • Can occur via apoptotic signals or preprogramming • Ex: our fingers are webbed and then the webbing undergoes apoptosis resulting in separation of the fingers. • The cell divides into apoptotic blebs, which can then be broken apart into apoptotic bodies and digested by other cells. o Digested by other cells so harmful chemicals are never released.
65
during apoptosis, the cell divides into _______, which can then be broken apart into ________ and digested by other cells.
apoptotic blebs | apoptotic bodies
66
necrosis
cell death as a result of injury and internal substances are leaked which can cause irritation of nearby tissues.
67
regeneration
 Regenerative capacity: the ability of an organism to regrow certain parts of the body, varies from species to species.  Complete regeneration: the lost or damaged tissues are replaced with identical tissues. • Stem cells can migrate to and differentiate into the lost tissue  Incomplete regeneration: the newly formed tissue is not identical in structure or function to the tissue that has been injured or lost. • Heart has no regenerative capacity while the liver has a lot.
68
regenerative capacity
the ability of an organism to regrow certain parts of the body, varies from species to species. salamanders have a large amount of stem cells so they have a high regenerative capacity.
69
complete regeneration
the lost or damaged tissues are replaced with identical tissues. • Stem cells can migrate to and differentiate into the lost tissue
70
incomplete regeneration
the newly formed tissue is not identical in structure or function to the tissue that has been injured or lost. • Heart has no regenerative capacity while the liver has a lot.
71
senescence
biological aging, can occur at the cellular and organismal level as the changes accumulate.
72
cellular level senescence
Cells are no longer able to divide properly, possibly due to shortening of telomeres. • Telomerase prevents this from happening but is only acting in germ cells, fetal cells, and tumor cells.
73
organismal level senescence
Changes in the body’s ability to respond to a changing environment.
74
____ in the fetus occurs across the placenta as _____ do not function until birth.
Gas exchange | fetal lungs
75
the placenta serves endocrine functions, secreting ______
estrogen, progesterone, and human chorionic gonadotropin (hCG)
76
Oxygenation occurs at the placenta, so umbilical arteries carry ______ blood and the umbilical vein carries ______ blood.
deoxygenated | oxygenated
77
Maternal and fetal blood cannot mix because ____
they may be different blood types
78
fetal hemoglobin (HbF)
greater affinity for oxygen than maternal hemoglobin (HbA) | o Helps with transfer and retention of oxygen by HbF
79
umbilical arteries
carry blood away from the fetus toward the placenta deoxygenated
80
umbilical veins
carries blood toward the fetus from the placenta. oxygenated
81
what are the differences between fetal and adult circualtion
 Lungs and liver do not function until after birth  Gas exchange at the placenta (rather than lungs)  Detoxification and metabolism by mother’s liver  Nutrients and waste exchange at the placenta
82
what are the names of the 3 shunts of the fetus
foramen ovale ductus arteriosus ductus venosus
83
what are the shunts used to reroute blood from the lungs
foramen ovale | ductus arteriosus
84
what is the shunt to bypass the liver
ductus venosus
85
what part of the baby are the shunts used for
liver and lungs
86
foramen ovale
one-way valve that connects the right atrium to the left atrium. o Blood entering the right atrium from the inferior vena cava can flow into the left atrium instead of the right ventricle. Pumped through the aorta into systemic circulation directly. Due to pressure gradient where pressure is higher in left side (switched upon birth)
87
ductus arteriosus
shunts leftover blood from the pulmonary artery to the aorta. Pressure difference once again pushes blood through this opening and into systemic circulation.
88
ductus venosus
shunts the blood returning from the placenta via the umbilical vein directly into the inferior vena cava.
89
ductus venosus
shunts the blood returning from the placenta via the umbilical vein directly into the inferior vena cava.
90
placental lungs are filled with ______
fluid
91
human gestation lasts _____ weeks
40
92
what occurs during the first trimester?
organogenesis o The major organs begin to develop. o Embryo grows in size. o Fetus: after 8 weeks, brain is developing, organs have formed, bones harden.
93
what occurs during the second trimester?
– movement and face o Grows, face and fingers take shape o Begins to move in the amniotic fluid
94
what occurs during the third trimester?
antibody transfer o Rapid growth o Further brain development o Antibody transport from mother to fetus increases rate in preparation for outside world. o At the end, growth slows, and becomes less active because it has less room to move
95
parturition
vaginal childbirth accomplished by rhythmic contractions of uterine smooth muscle, coordinated by prostaglandins and peptide hormone oxytocin.
96
what hormone is responsible for uterine smooth muscle contraction during birth?
oxytocin
97
what are the steps of birth?
 1. Cervix thins out and amniotic sac ruptures (water breaking)  2. Strong uterine contractions result in birth  3. Placenta and umbilical cord are expelled (from mother), known as afterbirth
98
What is the fertilization membrane
depolarized and impenetrable membrane that is the result of the cortical reaction (a release of calcium ions into the zygote).
99
cortical granule
holds the calcium ions responsible for the cortical reaction upon fertilization.
100
_____ occurs in the fallopian tubes while _______ and _____ occurs in the uterus.
fertilization | implantation and growth
101
____ occurs as the zygote moves from the fallopian tubes to the uterus.
cleavage
102
what are two things that occur when cleavage occurs
increase in the nucleus to cytoplasmic ratio. | increase in the surface area to volume ratio.
103
Blastocyst: the trophoblast gives rise to ____ and the inner cell mass gives rise to _____
chorion and placenta | the organism itself
104
draw a blastocyst
fluid filled inner cavity surrounded by tropoblast cells with the inner cell mass cells at the top.
105
chorionic villi
microscopic finger-like projections that penetrate the endometrium.
106
compare deuterosomes and protostomes
Deuterostomes: the blastopore is the anus Protostomes: the blastopore is the mouth
107
what is selective transcription?
only genes needed for a particular cell type are transcribed which allows cells to be different (differentiated)
108
_____ diffuse from organizing cells to the responsive cells
inducers
109
the adrenal medulla is derived from the ______ and the adrenal cortex is derived from the _____
ectoderm | mesoderm
110
the notocord is a part of the ____ germ layer
mesodermal
111
how does induction influence development?
Certain cells influence the differentiation of nearby cells. It plays a role in spatial organization and is important for cells that play similar roles or are complementary to each other.
112
when a cell is _____, it is committed to a particular lineage (irreversibly). When the cell ______, it assumes the structure, function, and biochemistry of that cell type.
determined | differentiates
113
to create ______, scientists remove the _______ from a _____ created in a laboraotry
embryonic stem cell lines, inner cell mass, blastocyst
114
to respond to an inducer signal, a cell must be _____, or able to respond to the inducing signal.
competent
115
compare the regenerative capacity of the human heart, kidney, and liver
heart has no regenerative capacity liver has high regenerative capacity kidneys have moderate regenerative capacity
116
what types of cells express telomerase
tumor, germ cells, fetal cells
117
the placenta is where fetal ____, ___, and ____ exchange occurs
nutrient, gas, waste
118
fetal and maternal ____ cannot mix because they may be different types
blood
119
a _______ is used to move oxygen into the fetal blood stream along with the high affinity of fetal hemoglobin (HbF)
concentration gradient
120
fetal lungs do not function until ____
birth
121
the crossing of ______ across the placental membrane serves as a protective function
antibodies
122
the 3 fetal shunts direct blood away from what fetal organs: ____ and ____
liver and lungs
123
what do prostaglandins and oxytocin (peptide hormone) do during birth?
coordinate uterine smooth muscle contractions
124
the development stage with the greatest nuclear to cytoplasmic ratio is the _____
blastula
125
the neural tube forms from the ____
ectoderm
126
the last structure to become fully functional in a developing child during pregnancy is the ____
lungs
127
the placenta serves endocrine functions, secreting ______
estrogen, progesterone, and human chorionic gonadotropin (hCG)

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