π± MCAT Biology Review - 3 Flashcards
(136 cards)
1
Q
What is the consequence of a cell releasing a substance that influences nearby cells?
A
This is an example of paracrine communication
2
Q
What is the role of oxytocin during childbirth?
A
Coordinates uterine contractions
3
Q
Which germ layer is correctly associated with the formation of fingernails?
A
Ectoderm
4
Q
From which layer does the notochord form?
A
Mesoderm
5
Q
What is the term for the influence of a specific group of cells on the differentiation of another group?
A
Induction
6
Q
What is likely to be found in the blood of a pregnant person?
A
Progesterone produced by placental cells
7
Q
Which type of twins results from the fertilization of two different eggs?
A
Dizygotic (fraternal) twins
8
Q
What occurs during the cortical reaction post-fertilization?
A
Release of calcium ions that depolarize the ovum membrane
9
Q
What is the first stage of embryonic development after fertilization?
A
Cleavage
10
Q
What type of cleavage results in cells that can develop into complete organisms?
A
Indeterminate cleavage
11
Q
What is the solid mass of cells formed after several divisions called?
A
Morula
12
Q
What is the fluid-filled cavity within a blastula known as?
A
Blastocoel
13
Q
Which cells give rise to the chorion and later the placenta?
A
Trophoblast cells
14
Q
Fill in the blank: Anencephaly is a rare physiological abnormality in which the cerebrum fails to develop during the _______.
A
First trimester
15
Q
True or False: Adult stem cells retain inherent pluripotency if harvested from selected organs.
A
False
16
Q
What does the term βdeterminate cleavageβ refer to?
A
Cells with fates already determined
17
Q
What type of twins can result from a single zygote splitting into two?
A
Monozygotic (identical) twins
18
Q
What is the term for the process of the embryo burrowing into the endometrium?
A
Implantation
19
Q
What is a blastula?
A
An embryo with a fluid-filled cavity called the blastocoel
The blastula is an early stage of embryonic development characterized by the formation of a cavity.
20
Q
What is implantation?
A
The process where the blastula burrows into the endometrium of the uterus
Implantation is a crucial step for establishing pregnancy.
21
Q
What are trophoblast cells?
A
Specialized cells that create an interface between maternal blood supply and the developing embryo
Trophoblasts also contribute to the formation of the placenta.
22
Q
What is the chorion?
A
An extraembryonic membrane that develops into the placenta
The chorion forms chorionic villi that penetrate the endometrium for maternal-fetal gas exchange.
23
Q
What is the function of the umbilical cord?
A
Connects the embryo to the placenta and carries nutrients and waste
It consists of two arteries and one vein encased in a gelatinous substance.
24
Q
What is an ectopic pregnancy?
A
A condition where the blastula implants outside the uterus, often in the fallopian tube
Ectopic pregnancies are generally not viable and can lead to serious complications.
25
What is the yolk sac?
An extraembryonic membrane that supports the embryo before the placenta is functional
## Footnote
It is also the site of early blood cell development.
26
What is the role of the amnion?
A thin membrane filled with amniotic fluid that protects the embryo
## Footnote
Amniotic fluid serves as a shock absorber during pregnancy.
27
What is amniocentesis?
A procedure to aspirate amniotic fluid for chromosomal analysis
## Footnote
It is recommended for individuals over 35 to check for chromosomal abnormalities.
28
What is gastrulation?
The generation of three distinct cell layers from the embryo
## Footnote
This process marks a significant stage of development after implantation.
29
What are the three primary germ layers?
* Ectoderm
* Mesoderm
* Endoderm
## Footnote
These layers give rise to various tissues and organs in the developing organism.
30
What does the ectoderm develop into?
The integument, nervous system, and parts of the eye
## Footnote
It includes structures like hair, nails, and the epidermis.
31
What does the mesoderm develop into?
Musculoskeletal, circulatory, and excretory systems
## Footnote
It also gives rise to gonads and connective tissues.
32
What does the endoderm develop into?
Epithelial linings of the digestive and respiratory tracts
## Footnote
It includes organs like the pancreas and thyroid.
33
What is selective transcription?
The process where only specific genes needed for a cell type are transcribed
## Footnote
This allows cells to develop distinct functions despite having the same genetic material.
34
What is induction in developmental biology?
The ability of one group of cells to influence the fate of nearby cells
## Footnote
Induction is mediated by chemical substances called inducers.
35
What is neurulation?
The development of the nervous system from the ectoderm
## Footnote
It involves the formation of the neural tube, which gives rise to the central nervous system.
36
What are neural crest cells?
Cells that migrate outward from the neural folds to form the peripheral nervous system
## Footnote
They also develop into various cell types in other tissues.
37
What are teratogens?
Substances that interfere with development, causing defects or death of the embryo
## Footnote
Common teratogens include alcohol, drugs, and environmental chemicals.
38
What is the impact of maternal health on embryonic development?
Certain conditions can lead to overexposure or underexposure of the embryo to harmful substances
## Footnote
Examples include diabetes and folic acid deficiency affecting neural tube closure.
39
What is the difference between determinate and indeterminate cleavage?
* Determinate cleavage: Cells are committed to a specific cell type early
* Indeterminate cleavage: Cells can develop into any cell type
## Footnote
This distinction affects the potential of the resulting cells.
40
What are the stages of development from zygote to gastrula?
* Zygote
* 2-cell stage
* 4-cell stage
* 8-cell stage
* Morula
* Blastula
* Gastrula
## Footnote
Each stage represents a key step in embryonic development.
41
What is the role of morphogens in determination?
They are secreted molecules that influence neighboring cells' developmental pathways
## Footnote
Morphogens play a crucial role in cell differentiation.
42
What is the significance of the notochord in neurulation?
It induces the formation of the neural folds and ultimately the neural tube
## Footnote
The notochord is a mesodermal structure that acts as a signaling center.
43
What are the potential outcomes of neural tube defects?
* Spina bifida
* Anencephaly
## Footnote
Outcomes can vary from mild to fatal, highlighting the importance of folate in pregnancy.
44
What is cleavage in cellular development?
The asymmetric distribution of existing mRNA and protein between daughter cells
45
What are morphogens?
Specific molecules secreted from nearby cells that influence neighboring cell development
46
What is determination in cell development?
A commitment to a particular cell type without yet producing necessary functions
47
What process follows determination?
Differentiation
48
What is differentiation?
The process by which a determined cell changes structure, function, and biochemistry to match its cell type
49
What defines stem cells?
Cells that have not yet differentiated or give rise to other cells that will
50
What are totipotent stem cells?
Stem cells that can differentiate into any cell type, including those in the fetus and placental structures
51
What are pluripotent stem cells?
Cells that can differentiate into any cell type except for those found in placental structures
52
What are multipotent stem cells?
Stem cells that can differentiate into multiple types of cells within a particular group
53
How does potency relate to stem cells?
Potency is a spectrum from totipotent to pluripotent to multipotent as cells become more differentiated
54
What are embryonic stem (ES) cells?
Cells derived from the inner cell mass of a very early-stage embryo that retain pluripotency
55
What is the blastocyst?
A hollow ball of cells that forms about a week after fertilization, consisting of trophoblasts and an inner cell mass
56
What are the three germ layers formed during gastrulation?
* Endoderm
* Mesoderm
* Ectoderm
57
What is the significance of adult stem cells?
They are typically multipotent and can be induced to differentiate into different tissue types from the patient
58
What is the role of microRNA-29b in differentiation?
It influences the differentiation of neuroectoderm cells into neural tube epithelial cells and neural crest cells
59
What are inducers in cell differentiation?
Signals that promote differentiation and mitosis in specific tissues, often in the form of growth factors
60
What are the types of cell-cell communication?
* Autocrine
* Paracrine
* Juxtacrine
* Endocrine
61
What is reciprocal development?
A process where the differentiation of one tissue induces changes in another tissue
62
Fill in the blank: The inner cell mass (ICM) will eventually become the _______.
fetus
63
True or False: All stem cells are derived only from embryonic tissues.
False
64
What is a key challenge in using adult stem cells?
Inducing differentiation into the correct cell type
65
What happens when the optic vesicle touches the ectoderm during eye development?
The optic vesicle induces the ectoderm to form the lens placode
66
What are hematopoietic stem cells capable of differentiating into?
* White blood cells
* Red blood cells
* Platelets
67
What are optic vesicles?
Lateral outpocketings from the brain that grow out during the development of the eyes.
## Footnote
They induce the formation of the lens placode and optic cup.
68
What is the function of the lens placode?
It induces the optic vesicle to create the optic cup and develops into the cornea and lens.
## Footnote
The lens placode is formed from the ectoderm.
69
What is a morphogen?
Molecules that cause determination of cells by diffusing throughout the organism.
## Footnote
They create gradients that influence cell differentiation.
70
What are some common morphogens?
* Transforming growth factor beta (TGF-Ξ²)
* Sonic hedgehog (Shh)
* Epidermal growth factor (EGF)
71
What is cell migration?
The process by which cells disconnect from adjacent structures and move to their correct location.
## Footnote
An example is the migration of the anterior pituitary gland.
72
What is apoptosis?
Programmed cell death that occurs during development, allowing for the removal of unnecessary cells.
## Footnote
It is different from necrosis, which is cell death due to injury.
73
What happens during apoptosis?
Cells undergo morphological changes, forming apoptotic blebs that are eventually digested by other cells.
## Footnote
This process recycles materials and prevents harmful substance release.
74
What is the difference between apoptosis and necrosis?
* Apoptosis: Programmed cell death with controlled processes
* Necrosis: Uncontrolled cell death due to injury
75
What is regenerative capacity?
The ability of an organism to regrow certain parts of the body, varying significantly among species.
## Footnote
Complete regeneration means identical tissue replacement, while incomplete regeneration does not.
76
What is senescence?
Biological aging that occurs at the cellular and organismal level, leading to cellular division failure.
## Footnote
It may be caused by shortened telomeres.
77
What role do telomeres play in cellular senescence?
Telomeres protect chromosome ends and shorten with each cell division, limiting the number of divisions.
## Footnote
Shortened telomeres eventually prevent replication.
78
What is the function of telomerase?
An enzyme that synthesizes the ends of chromosomes, preventing senescence and allowing indefinite cell division.
## Footnote
It is expressed in germ cells, fetal cells, and tumor cells.
79
What is unique about fetal circulation?
Fetal circulation bypasses the lungs and liver through three shunts, as these organs are not functional before birth.
## Footnote
Gas exchange occurs at the placenta instead.
80
What are the umbilical arteries and veins?
* Umbilical arteries: Carry deoxygenated blood from the fetus to the placenta
* Umbilical vein: Carries oxygenated blood from the placenta to the fetus
81
What are the three fetal shunts?
* Foramen ovale: Connects right atrium to left atrium
* Ductus arteriosus: Connects pulmonary artery to aorta
* Ductus venosus: Connects umbilical vein to inferior vena cava
82
What occurs during the first trimester of gestation?
Major organs begin to develop, the heart starts beating, and the embryo is known as a fetus by the end of eight weeks.
## Footnote
The embryo grows from 10 mm to about 9 cm by the end of the third month.
83
What characterizes the second trimester of gestation?
The fetus undergoes significant growth and begins to move within the amniotic fluid.
## Footnote
By the end of the sixth month, the fetus measures 30 to 36 cm long.
84
What happens during the third trimester of gestation?
Rapid growth continues, and antibodies are transferred from the pregnant individual to the fetus for protection.
## Footnote
This transfer peaks in the ninth month.
85
What is the first stage of fetal development called?
Fertilization
## Footnote
Fertilization is the joining of a sperm and an ovum, usually occurring in the ampulla of the fallopian tube.
86
What occurs during the cortical reaction?
Release of calcium ions preventing additional sperm from fertilizing the egg
## Footnote
This reaction increases the metabolic rate of the resulting diploid zygote.
87
What are fraternal twins also known as?
Dizygotic twins
88
What is the solid mass of cells seen in early development called?
Morula
89
What does the blastula consist of?
Trophoblast and inner cell mass
90
What is the role of the chorion?
Contains chorionic villi that penetrate the endometrium
## Footnote
This creates the interface between maternal and fetal blood.
91
What do the umbilical arteries carry?
Deoxygenated blood from the fetus to the placenta
92
What is the function of the ductus arteriosus?
Connects the pulmonary artery to the aorta, bypassing the lungs
93
What is the term for programmed cell death?
Apoptosis
94
What are the three primary germ layers formed during gastrulation?
* Ectoderm
* Mesoderm
* Endoderm
95
What does the ectoderm develop into?
* Epidermis
* Nervous system
* Hair and nails
96
What is the term for the commitment of a cell to a specific lineage?
Determination
97
What are totipotent cells capable of differentiating into?
All cell types, including the three germ layers and placental structures
98
What is the difference between indeterminate and determinate cleavage?
* Indeterminate cleavage: cells can become any cell type
* Determinate cleavage: cells are committed to a specific cell type
99
What is the function of the placenta?
* Nutrient exchange
* Gas exchange
* Immune protection
* Hormone secretion
100
What is the significance of fetal hemoglobin (HbF)?
Higher affinity for oxygen than adult hemoglobin (HbA)
101
What is the primary function of the allantois?
Involved in early fluid exchange between the embryo and the yolk sac
102
Fill in the blank: The _______ connects the right atrium to the left atrium, bypassing the lungs.
Foramen ovale
103
During which trimester does organogenesis occur?
First trimester
104
What happens during the second phase of birth?
Strong uterine contractions result in the birth of the fetus
105
What is the term for substances that interfere with development?
Teratogens
106
What is the process by which nearby cells influence the differentiation of adjacent cells called?
Induction
107
What is senescence?
Result of multiple molecular and metabolic processes, including shortening of telomeres
108
What is the role of growth factors in cell signaling?
Promote differentiation and mitosis in certain tissues
109
What is the fluid-filled center of the blastula called?
Blastocoel
110
True or False: The umbilical vein carries deoxygenated blood.
False
111
What hormones are involved in uterine contractions during birth?
Prostaglandins and oxytocin
## Footnote
Prostaglandins promote cervical dilation and the onset of contractions, while oxytocin promotes uterine contractions in a positive feedback loop.
112
What occurs in the third phase of childbirth?
The placenta and umbilical cord are expelled
113
What does the ectoderm give rise to?
* Integument (epidermis, hair, nails)
* Epithelia of nose, mouth, and anal canal
* Lens of the eye
* Nervous system (including adrenal medulla)
114
What does the endoderm give rise to?
* Epithelial linings of the digestive tract
* Epithelial linings of the respiratory tract
* Parts of the liver
* Pancreas
* Thyroid
* Bladder
115
What structures does the mesoderm develop into?
* Musculoskeletal system
* Circulatory system
* Excretory system
* Gonads
* Adrenal cortex
116
What is the role of the notochord during embryonic development?
Inductive effects on the overlying ectoderm to form the neural tube
117
What is induction in developmental biology?
Influence of a specific group of cells on the differentiation of another group of cells
118
What does competence refer to in developmental biology?
The ability of a cell to respond to a given inducer
119
What is senescence?
Biological aging
120
What are the hormones produced by the placenta during pregnancy?
* Estrogen
* Progesterone
121
True or False: Fetal hemoglobin can easily cross the placenta.
False
122
What type of signaling occurs when a cell releases a substance that diffuses to a nearby cell?
Paracrine signaling
123
What happens to somatic cells as they divide?
They divide a limited number of times until telomeres shorten
124
What allows cells to divide indefinitely without senescence?
Activation of the enzyme telomerase
125
When does organogenesis primarily occur during pregnancy?
During the first trimester
126
What is an example of incomplete regeneration in humans?
Formation of a fibrous scar in the heart after injury
127
What is the morula?
A solid ball of cells formed after the first cell divisions
128
What is the final structure to become fully functional during organogenesis?
Lungs
129
What is the direction of blood flow in the ductus arteriosus during prenatal life?
From the pulmonary artery to the aorta
130
What is apoptosis?
Programmed cell death necessary for proper development
131
Fill in the blank: The _______ is a rod of mesodermal cells that develops along the longitudinal axis of the embryo.
notochord
132
What is the result of failure of apoptosis in the digestive tract?
An imperforate anus
133
True or False: Adult stem cells are naturally pluripotent.
False
134
What do embryonic stem cells require for harvesting?
Termination of an embryo
135
What is the blastula?
The stage of embryonic development characterized by a hollow center
136
What occurs due to the reciprocal induction between the brain and ectoderm?
Formation of the eyes
