embryo exam 2
Chorion vs. Decidua
-Chorion - embryonic portion derived from the trophoblast -Decidua - maternal portion derived from the endometrium
The dermamyotome subdivides further into? (4)
-Dermatome - will form parts of the dermis and connective tissue -Myotome - will form muscle, this then subdivides further into: -Epimere - dorsal, forms deep muscles of the back -Hypomere - ventral, forms lateral and ventral muscles of body wall, limbs
2. Bending of neural plate:
-Edges of the neural plate thicken and move upwards to form the neural folds -The neural groove appears in the center of the neural folds -Epidermal cells move towards the center, pushing the cells in between
what is the decidual reaction?
-Endometrial cells contacting the blastocyst differentiate into decidual cells -This is called the decidual reaction and these cells form the decidua
What secretes growth factors the support the embryo?
-Endometrial glands enlarge and the endometrial wall becomes highly vascularized -The endometrial glands and the decidual cells secrete growth factors that support the embryo
Cranial and spinal neural crest form (3):
-Enteric ganglia of the gut - responsible for peristalsis of intestine -a defect in enteric ganglia formation leads to Hirschprung's Disease (lethal megacolon from an inability to pass feces) -Myelinating Schwann cells -Melanocytes - pigment cells of the skin
Inheritance pattern: Can females pass disease to their sons?
-Female carriers can pass the disease to their sons, they get their only X from her so they will have the disease
What is x-inactivation and what happens if it doesn't occur?
-Female mammals do this by silencing most genes on one of their two Xs -This is called X-inactivation, and which X is silenced is random ...If X-inactivation doesn't occur the female embryo dies
First 7 somitomeres will form __________ Rest develop into discrete chunks of mesoderm called ______ at about 3-4 per day
-First 7 somitomeres will form the muscles of the FACE, JAW AND THROAT -Rest develop into discrete chunks of mesoderm called SOMITES at about 3-4 per day
X-linked Diseases: Since males only have one X how do diseases showup?
-Males have only one X so if they have a mutation they show the disease -Male pattern baldness, hemophilia, red-green color blindness
3. Closure of the neural tube:
-Neural folds move up and towards the center, fusing to form the neural tube -The space in the center is the neural canal -The neural folds adhere and fuse at midline -The dorsal-most cells of the neural tube are the neural crest
Cranial neural crest forms:
-Pharyngeal arches - forms cartilage and bones of face and neck -Odontoblasts of teeth -Cranial nerve ganglia -Connective tissue around the eyes
Villus development: (primary, secondary, tertiary)
-Primary stem villus - outgrowth of the cytotrophoblast -Secondary stem villus - extraembryonic mesoderm penetrates into the center of the villus -Tertiary stem villus - extraembryonic mesoderm gives rise to blood vessels that connect to the embryonic circulation -By the end of the fourth week 3o villi cover the entire chorion
Why folic acid prevents NTDs is not well understood, it may:
-Supplement a dietary deficiency -Overcome a genetic defect that make some women absorb or use folate poorly
1. Formation/shaping of the neural plate:
-The ectoderm differentiates into columnar cells called neuroectoderm -Neural plate appears cranially and lengthens along the axis of the embryo
3. Closure of the neural tube: where is the neural tube open at?
-The neural tube separates from the overlying ectoderm -The neural tube is open at the cranial and caudal neuropores (eventually close)
How do you get the color pattern in calico cats?
-The random silencing of one allele by X inactivation generates the color pattern -Silencing early in development, followed by many mitoses, results in patches of cells with the same X inactivated = patches of color
The oropharyngeal membrane (buccopharyngeal) and the cloacal membrane will become what?
-They will become the ends of the gut tube (mouth/anus). - Position changes dramatically during embryonic folding.
What are the competing interests of mother and father? (Haig Hypothesis)
-maternal advantage to conserve her resources, maximize her reproductive output over her life -paternal advantage to use maternal resources for the growth of his offspring
What does the XIST RNA do?
-the XIST RNA coats the entire X chromosome it is produced from, and recruits proteins that compact that X
what are the two ways neurulation can occur?
1) 1o neurulation - neural plate cells invaginate and pinch off from the surface to form a tube 2) 2o neurulation - a solid row of cells sinks into the embryo and hollows out to form a tube
There are 3 steps in X-inactivation...what are they?
1) Counting 2) Choice 3) Inactivation
What is counting (x-inactivation)?
1) Counting - the cell counts how many X chromosomes it has -A cell with multiple X chromosomes inactivates all but one
The nervous system can be divided into two main parts what are they?
1. Central nervous system (CNS) • Brain • Spinal cord 2. Peripheral nervous system (PNS) • Motor neurons • Sensory neurons
There are four major types of environmental influences what are they?
1. Chemoattraction • Netrins 2. Contact attraction • Proteins of the growing neurite can bind the proteins fibronectin and laminin 3. Chemorepulsion • Semaphorins 4. Contact repulsion • Caudal half of the somite prevents the ingrowth of motor neurons
What are the Three main types of folds in embryonic folding?
1. Head fold 2. Tail fold 3. Lateral folds
During primary neurulation the ectoderm is divided into 3 sets of cells:
1. Neural tube - central, will form the brain and spinal cord 2. Epidermis - lateral, will form skin 3. Neural crest - in between, will migrate to form many different cell types
what are the Stages of circuitry maturation (4):
1. Pre-reflex stage - Initial growth of neurites (includes motor, sensory, and interneurons - called the primary circuit) 2. Closure of the primary reflex circuit 3. Connections with other axons descending down the spinal cord from the brain 4. Completion of complex circuits and myelination by oligodendrocytes
What is choice (x-inactivation)?
2) Choice - the cell chooses which X will remain active (Xa), and which X (or Xs if more than one) will be inactivated (Xi) -The choice is usually random, but there are mutations that can alter the chance that a given X chromosome will be active
What is inactivation (x-inactivation)?
3) Inactivation - The process begins in a region of the X chromosome called the X Inactivation Center (XIC)
Sex Chromosome Abnormalities: Turner's Syndrome:
45,X individuals have Turner's Syndrome (1 in 2500 females) -They are masculinized females - sterility, short, broad chest, webbed neck -If one X is normally silent, why aren't they normal?
47,XXX are they male or female? normal? fertile?
47,XXX individuals are usually normal, fertile females (1 in 1000 females) -Can have genitourinary malformations, delayed puberty, mild mental retardation -48,XXXX individuals have a more widely varying phenotype (Rare, ~100 cases) -There is increasing disability with each additional X (~15 IQ points per X)
Sex Chromosome Abnormalities: Klinefelter's Syndrome:
47,XXY individuals have Klinefelter's Syndrome (1 in 500 males) -They are feminized males - hypogonadism, sterility, gynecomastia -One of their Xs inactivates as it should, so why aren't they normal?
47,XYY are they male or female? normal? fertile?
47,XYY individuals are usually normal, fertile males (1 in 1000 males) -They may be taller than normal, have mild mental retardation -Reported increased aggression, risk of criminal behavior now shown to be untrue
48,XXYY are they normal?
48,XXYY individuals are viable males (1 in 20,000 males?) -May have severe psychiatric disorders, mental retardation, overgrowth
How can a mother who is Rh- have an Rh+ baby?
A mother without Rh proteins (Rh-) can have an Rh+ fetus if the father is Rh+
What is Microcephaly?
A variety of developmental defects can result in microcephaly. • Smaller than normal head due to impaired brain development. • Genetic causes: Down syndrome, Smith-Lemli-Opitz syndrome, Wolf-Hirschorn syndrome, many others. • Environmental causes: exposure to teratogens, radiation, drugs, fetal alcohol syndrome, maternal diabetes, infection.
Actual exam question: Q: What tissues induce the formation of the neural plate?
A: notochord and prechordal mesoderm
How many genes are expressed in an "imprinted manner"?
About 100 genes in the human or mouse are expressed in an "imprinted" manner -they are called imprinted genes, and the process that controls them is called genomic imprinting
How is the trilaminar germ disc formed?
After gastrulation: Once all cells have moved through the primitive streak, the remaining epiblast cells are now the ectoderm and the embryo is now called the trilaminar germ disc.
Do all animals with two different sex chromosomes have dosage compensation?
All animals with two different sex chromosomes must have some type of dosage compensation, but.... ....different methods are used in different animals.
Alveolar capillary dysplasia -
Alveolar capillary dysplasia - • Capillaries fail to properly form around the alveoli • Shortly after birth, infants experience respiratory distress • Usually results in death of the newborn • In July 2012, the first newborn with ACD was kept alive via use of an artificial lung followed by a lung transplant
Alveolar ducts branch from the respiratory bronchioles and give rise to what?
Alveolar ducts branch from the respiratory bronchioles and give rise alveolar sacs
Alveolar sacs eventually give rise to what?
Alveolar sacs eventually give rise to alveoli
An XX individual in which a bit of the Y chromosome containing SRY has been translocated will be phenotypically ______
An XX individual in which a bit of the Y chromosome containing SRY has been translocated will be phenotypically male
An XY individual with a mutation in SRY will be phenotypically ______?
An XY individual with a mutation in SRY will be phenotypically female
All three folding events contribute to the following: An endoderm lined gut tube has formed consisting of what?
An endoderm lined gut tube has formed consisting of a foregut, midgut, and hindgut. • By 6 weeks only the midgut remains open to the yolk sac.
What causes respiratory passageways to open in infants?
An infant takes a first breath as a reflex, and this breath causes the respiratory passageways to open.
Are there side effects of using prenatal corticosteroids?
Are there side effects? - Repeated doses can cause alveolar structural damage; rarely given. - No known side effects for infant. - Maternal pulmonary edema when given with anti-labor medications.
how is the smooth chorion or chorion laeve formed?
As the embryo bulges into the uterine cavity, the villi on the abembryonic side of the chorion disappear... -This is now called the smooth chorion or chorion laeve
What happens to the villi as the embryo bulges into the uterine cavity?
As the embryo bulges into the uterine cavity, the villi on the abembryonic side of the chorion disappear... -This is now called the smooth chorion or chorion laeve -The part of the chorion associated with the decidua basalis is called the chorion frondosum
what happens to the yolk sac as the embryo gets bigger?
As the embryo grows, the yolk sac is used up and the amniotic cavity with the embryo enlarges to take up the entire chorionic cavity
Development of neural function: At # weeks, the entire embryo is sensitive to touch.
At 12 weeks, the entire embryo is sensitive to touch.
At 4 weeks, the developing brain is differentiated into 3 areas...what are those areas?
At 4 weeks, the developing brain is differentiated into 3 areas: prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain) • These regions are visible before the posterior neural tube closes
At 5 weeks, 5 secondary vesicles have formed from the 3 primary vesicles ...what are they and where did they come from?
At 5 weeks, 5 secondary vesicles have formed from the 3 primary vesicles: telencephalon and diencephalon from the forebrain; mesencephalon from the midbrain; metencephalon and myelencephalon from the hindbrain
At around 4 weeks, ________ form at the caudal end of the respiratory diverticulum
At around 4 weeks, lung (bronchial) buds form at the caudal end of the respiratory diverticulum
What are the Intrinsic factors that control the neurite?
Axonal transport & Growth Cones
What is axonal transport?
Axonal transport - transportation of materials produced in the cell body down the length of the axon • For example, tubulin subunits must be transported from the cell body to the end of the microtubules of an elongating neurite
Beckwith-Wiedemann Syndrome (BWS) what kind of disease is it? What happens?
Beckwith-Wiedemann Syndrome (BWS) is an imprinting disease One imprinted gene is called IGF2, it produces Insulin-like growth factor II -IGF2 is normally expressed only from the PATERNAL allele -in BWS, both IGF2 alleles are active - A DOUBLE DOSE OF THIS GROWTH FACTOR
Before birth, the fetus' lungs are filled with liquid...what two kinds?
Before birth, the fetus' lungs are filled with liquid • Surfactant and amniotic fluid
When does embryonic folding occur?
Between weeks 3 and 4 the embryo undergoes major morphogenetic changes called embryonic folding.
Binding of axons together is facilitated by what?
Binding of axons together is facilitated by N-cadherin
What kind of folding contributes to the formation of the gut?
Both lateral and cranial/caudal folding of the embryo contribute to formation of the gut.
What is botox and how does it work?
Botox = botulinum toxin = botulism = a neurotoxin Botox works by preventing the release of acetylcholine into the neuromuscular junction
How can we SEE X-inactivation in calico cats?
Calico cats are almost always female, because one of the genes that determines coat color lies on the X chromosome. -This gene comes in two alleles, one that makes orange and one that makes black
The cardiogenic plate carries the _________ along with it - (which is the future diaphragm).
Carries septum transversum mesoderm along with it - future diaphragm. 
What do neurons do?
Carry signals to and from the CNS
Name common histone modifications
Common histone modifications are phosphorylation, methylation and acetylation
How do axons and dendrites communicate?
Communicate with each other via synapses
What are neurons composed of?
Composed of axons, a cell body, and dendrites • Dendrites pick up electrical impulses from other cells • Axons transmit messages to/from the spinal cord
Conducting airways then respirator airways or vice versa?
Conducting airways then respirator airways Conducting: Bronchi-> Bronchioles Respiratory: (respiratory) bronchioles -> Alveoli
What is the cranial flexure? and how does it occur?
Cranial flexure (head fold) occurs as a sharp bend of the neural tube in the area of the future mesencephalon. The cranial flexure: • Constricts the cranial region of the yolk sac • Results in the formation of the foregut
Cranial portion forms the _____. Caudal portion forms the _____.
Cranial portion forms the brain. Caudal portion forms the spinal cord.
What aspects give rise to the ventral surface of the embryo?
Cranial, caudal, and lateral aspects give rise to the ventral surface of the embryo.
Nervous system developmental defects: Malformations of the eye What is cyclopia?
Cyclopia occurs when the prosencephalon fails to set up the proper midline, and the orbits of the eye develop too close to one another.
What happens in DNA methylation
DNA methylation - methyl groups added to the 5-carbon of cytosine, usually at CG dinucleotides, can alter the expression of nearby genes
DNA methylation requires what? Where does it get it from?
DNA methylation requires a methyl donor - a chemical compound to take the methyl group from. • S-adenosylmethionine (SAM) is a compound that can provide a methyl group for the DNA methylation reaction • The components to make SAM come from the diet • SAM is marketed as a dietary supplement, and is in clinical trials for several types of human disease • What are the long-term implications of such supplementation?
Dermatome vs. Myotome
Dermatome - will form parts of the dermis and connective tissue -Myotome - will form muscle, this then subdivides further into: -Epimere - dorsal, forms deep muscles of the back -Hypomere - ventral, forms lateral and ventral muscles of body wall, limbs
Development of the Brain Telencephalon: • Cerebral hemispheres...what does this control?
Development of the Brain • Telencephalon: • Cerebral hemispheres - control sensory perception and motor functions
Development of the Brain Diencephalon: • Hypothalamus does what?
Diencephalon: • Hypothalamus - main regulator of homeostasis in the body
Development of the Brain Diencephalon: • Optic vesicles do what?
Diencephalon: • Optic vesicles - future retina
Development of the Brain Diencephalon: • Thalamus does what?
Diencephalon: • Thalamus - relays sensory and motor signals to the cerebrum
When would the mother make antibodies against Rh?
During birth fetal blood can leak into the maternal circulation and the mother may subsequently make an antibody against Rh
Where do "pseudo‐embryos" come from? What are they also called?
ES cells can be differentiated in vitro to form different types of cells. The cells form "pseudo‐embryos" called embryoid bodies - they do not look like embryos, but they contain many embryonic cell types.
ES cells express pluripotency genes such as Oct4, Sox2, Nanog that help maintain what?
ES cells express pluripotency genes such as Oct4, Sox2, Nanog that help maintain pluripotency. Nanog expression in mouse preimplantation embryos. A,B: Whole‐mount in situ hybridization using a Nanog riboprobe revealed expression in morulae (A) and the inner cell mass of the blastocyst (B). C: Negative control, mouse Nanog sense probe.
What is the combined surface area for gas exchange
Each alveoli is very small, but the combined surface area for gas exchange is 70 square meters (about the size of a badminton court)
What do iPS generated mice develop?
Early methods introduced new copies of pluripotency genes into the cells, this occasionally caused mutations. Mice generated from mouse iPS cells developed cancer at a fairly high rate. Newer methods reactivate the endogenous copies of these genes, rather than inserting new copies. The long term potential of iPS cells is still unknown
All three folding events contribute to the following: Ectoderm now covers the entire surface of the body except what?
Ectoderm now covers the entire surface of the body except the umbilical region where the yolk sac emerges.
Embryonic folding begins at the 3rd - 4th week of development: What is the force behind it?
Embryonic folding begins at the 3rd - 4th week of development. The force behind embryonic folding is driven by the differential growth of specific embryonic structures • At this stage, ectoderm grows faster than the mesoderm and endoderm; mesoderm grows faster than endoderm. Due to high cell proliferation.
Where do embryonic stem cells come from?
Embryonic stem (ES) cells are derived from the ICM of the blastocyst, and as pluripotent cells they can theoretically form any cell type
How can embryonic stem cells be differentiated in vitro?
Embryonic stem cells can be differentiated in vitro using growth factors and other compounds (assuming we know which to use), or transplanted and allowed to differentiate in vivo We are just beginning to understand the potential of these cells, and how to influence their differentiation along certain paths
3. Closure of the neural tube: What kind of cells cover the dorsal surface?
Epidermal cells cover the dorsal surface
What is epic-genetics and is it reversible?
Epigenetics describes processes that alter the activity or expression of a gene through modifications that do not involve changes to the DNA sequence -reversible chemical modification of the DNA
What is Erythroblastosis fetalis? Where does it come from?
Erythroblastosis fetalis (Hemolytic Disease of the Newborn, or HDN) is a disease caused by a maternal antibody that aaacks fetal red blood cells
When the embryo is pulled into the uterine wall, what proliferates and surrounds the embryo?
Eventually the embryo is completely pulled into the uterine wall -The syncytiotrophoblast proliferates and surrounds the embryo
Extrinsic factors are the environmental influences sensed by the _______
Extrinsic factors are the environmental influences sensed by the filopodia Influences can exist as concentration gradients or as fixed chemical/physical cues
True or False: Less neurons than are necessary initially make contact with a muscle
FALSE More neurons than are necessary initially make contact with a muscle
True or False: Mammalian eggs carry large stores of yolk to support their development?
FALSE Mammalian eggs DO NOT carry large stores of yolk to support their development -Must obtain nutrients from the mother -The placenta is a specialized organ to allow development within the uterus
Differentiation of ES cells into cardiac muscle in vitro: What are two of the growth factors used to differentiate ES cells?
FGF2 and BMP2 are two of the growth factors used to differentiate ES cells into cardiomyocytes
Failure of the cranial NT to close causes_____?
Failure of the cranial NT to close causes anencephaly -The skull doesn't form and sustained contact of the brain with amniotic fluid causes it to degenerate - the child is born with no brain -The fetus may survive to birth, but dies within hours or days
Feeding increased amounts of methyl donors to mothers during pregnancy can do what?
Feeding increased amounts of methyl donors to mothers during pregnancy can change the coat color of their offspring!
how many layers of tissue separate maternal and fetal blood, what are those layers?
Fetal and maternal blood are separated by 4 layers of tissue - the endothelium of the villous capillaries, the connective tissue of villus, a layer of cytotrophoblast, a layer of syncytiotrophoblast
what shape change occurs during embryonic folding?
Flat trilaminar disc -> C-shaped tube-within-a-tube body plan.
Fluid is removed in three ways:
Fluid is removed in three ways: 1. Pressure on the fetus' chest as it moves through the birth canal 2. Entrance into the pulmonary circulation via the alveolar capillaries 3. Entrance into the lymphatic system via the bronchioles
What happens when the amnionic cavity fills with fluid?
Folding changes embryonic and extraembryonic spaces such that amnion is wrapped around embryo. Gradually amniotic cavity fills with fluid, grows to fill the entire chorionic cavity. Extraembryonic coelom disappears
How many degrees does the heart rotate? When does it start beating?
Folding rotates the developing heart 180 degrees to its thoracic position. - Heart is already beating and around day 21.
For imprinted genes how is the active allele determined?
For imprinted genes, the active allele is determined by the parent it was inherited from, maternal or paternal
Explain the Dorsal/sensory horns?
Formation of peripheral nerves begin when neuroblasts of the dorsal root ganglia(derived from neural crest cells and located outside of the CNS) begin to grow • Dendrites grow from the cell body to the periphery • Axons grow from the cell body to the spinal cord and terminate in the dorsal horn (These axons are now called dorsal roots)
Formation of the intraembryonic coelom: • ___________ splits, giving rise to somatic and splanchnic mesoderm
Formation of the intraembryonic coelom: • Lateral plate mesoderm splits, giving rise to somatic and splanchnic mesoderm
Formation of the intraembryonic coelom: • The space between these mesoderm layers opens into the _______ • Embryonic folding brings these spaces inside the embryo establishing ________
Formation of the intraembryonic coelom: • The space between these mesoderm layers opens into the chorionic cavity • Embryonic folding brings these spaces inside the embryo establishing intraembryonic coelom
What patterns differ between ES and iPS cells?
From recent studies, it looks as though iPS cells are not the same as ES cells epigenetically DNA methylation patterns differ from ES cells Not yet clear what the significance of this is for their clinical use
What causes the separation of trachea and esophagus?
Fusion of the tracheoesophageal septum (ridge) causes separation of the trachea and esophagus.
Gas exchange takes place between the______ and the ______
Gas exchange takes place between the alveoli capillaries and the alveoli
What the difference between balletic and mono allelic? Which is more common?
Genes can be expressed in a biallelic manner -both alleles active (99% of genes) Or in a monoallelic manner -only one allele active (1% of genes)
Are maternal and paternal genomes equal? How was this discovered?
Genomic imprinting was discovered by nuclear transfer experiments in mice -embryos with two maternal or two paternal pronuclei die -- even though they have two normal genomes Showed that the maternal and paternal genomes are not equal
What do Glial cells do?
Glial Cells • Provide structure and nutrients to the neurons • Electrically insulate neurons • Direct axon growth
what are Glioblasts and what do they give off?
Glioblasts are formed when ample neuroblasts have differentiated. Give rise to: • Astrocytes - form blood brain barrier by wrapping around blood vessels • Oligodendrocytes - myelinate nerves in the CNS • Other glial cells that provide metabolic and structural support to neurons • For example, radial glial cells act as guides for migrating neurons
What is the growth cone?
Growth cones - the elongating area of the neurite that extend filopodia to sense the external environment • Filopodia are consistently extending and retracting in an attempt to correctly survey the surrounding environment
How can you prevent Erythroblastosis fetalis (Hemolytic Disease of the Newborn, or HDN)?
HDN can be prevented by giving the Rh- mother of an Rh+ fetus an antibody to Rh at delivery (Rhogam), removes fetal RBCs so she doesn't make her own antibody Erythroblastosis fetalis can be treated in utero with transfusions
What happens with Histone modifications
Histone modifications - chemical modifications to the tails of histone proteins in the nucleosome can alter the expression of nearby genes. Common histone modifications are phosphorylation, methylation and acetylation
How do Prenatal corticosteroids work?
How do they work? - Given 24-48 hrs before birth is expected - Promote differentiation of Type 1 and 2 AECs - Cause Type 2 AECs to release surfactant -Effect is time dependent; occurs in 24 hrs, lasts 7 days
Human diseases can result from defects in imprinting:
Human diseases can result from defects in imprinting: -both alleles can be expressed or neither can be expressed -these diseases usually involve abnormal growth, mental retardation, increased risk of cancer (even as a child)
What does generating new stem cell lines require?
Human embryonic stem cells are controversial - there are complicated legal and ethical issues Generating new stem cell lines requires the destruction of a blastocyst stage embryo
X Chromosome Inactivation: XX is ______ XY is ______ What problem is created for gene expression?
Humans have two sex chromosomes - X and Y -XX individuals are female and XY individuals are male This creates a problem for the expression levels of genes on these chromosomes -Females have no expression of Y genes and twice the expression of X genes
What is Hydatidiform mole?
Hydatidiform mole - an abnormality where the conceptus consists only of extraembryonic tissues, and the embryo itself is missing -Usually abort early but if not they can be diagnosed by very high levels of hCG
what is the Hydrostatic test used for?
Hydrostatic test - used to determine if a fetus was alive at the time of birth
What is hydrops fetalis?
If the fetus develops heart failure due to severe anemia this is called hydrops fetalis
How could a mother making antibodies against Rh negatively impact the baby?
If the mother carries a second Rh+ child, an>bodies from the first pregnancy cross the placenta to aaack the fetal RBCs during development, causing anemia, brain damage, fetal death
where on the blastocyst does implantation occur?
Implantation occurs at the embryonic pole of the blastocyst
True or False: Genetic Imprinting is only found in mammals?
Imprinted genes are found only in mammals Many of the known imprinted genes are involved in the regulation of growth during development
Explain why certain alleles are differentially methylated?
Imprinting is controlled by epigenetic processes such as DNA methylation At imprinted genes, DNA methylation is allele-specific - the maternally and paternally inherited alleles are "differentially methylated" This is one way to regulate the expression of imprinted genes
Is imprinting in humans and mice similar or drastically different?
Imprinting works similarly in humans and the mouse, so we can use mouse models to study human imprinting diseases -Disrupting the imprinting of the mouse Igf2 gene gives a mouse model for BWS
In humans both of these processes are used, _______ structures form by primary neurulation and _______ structures form by secondary neurulation
In humans both of these processes are used, cranial structures form by primary neurulation and caudal structures form by secondary neurulation
failure of the neural tube to close in humans is called? is it always fatal?
In humans we call this defect spina bifida -- an open vertebral canal. The severity of spina bifida can be mild to severe/fatal
How is neurolemma formed in CNS?
In the CNS, the oligodendrocyte cell body does not encase the axons, no neurolemma is formed, and axons of the CNS show little regrowth after damage.
Nerve damage and repair: How is the myelin sheath made up?
In the PNS, a Schwann cell will wrap its entire self around a portion of an axon up to 100 times. The inner layers consist of Schwann cell membrane and make up the myelin sheath.
How is a neuromuscular junction formed?
In the case of motor neurons, neurite elongation termination occurs when a motor axon comes into contact with a muscle fiber • A neuromuscular junction (a type of synapse) is formed
Fruit Fly and Nematode dosage compensation:
In the fruit fly Drosophila melanogaster, females are XX and males are XY -Males increase the expression of genes on their single X In the nematode Caenorhabditis elegans, hermaphrodites are XX and males are XO -Hermaphrodites decrease the expression of genes on their two Xs
Can differentiated cells be transplanted into the body?
In vitro differentiated cells can be transplanted into the body - for research purposes, or to treat certain types of diseases But, you must first know how to direct the ES cells to form the specific cell type you want (i.e. adding growth factors specific for this cell type) - this requires understanding the natural development of the cells
Infant Respiratory Distress Syndrome
Infant Respiratory Distress Syndrome • Formerly called hyaline membrane disease because of lung histology • Symptoms = difficulty breathing, cyanosis • Associated with premature infants, gestational diabetes. Due to lack of surfactant. • 1% of all births. Leading cause of death for premature infants. • Treatments = artificial surfactant, oxygen via breathing machines. Corticosteroids given before birth can speed lung maturation.
Inheritance pattern: Can Males pass x-linked disease to their son? to their daughter?
Inheritance pattern: -Males CAN'T pass the disease to their SONS, because males give sons a Y -Males CAN pass to a DAUGHTER, but she gets a normal X from mom so she's OK
Intermediate zone (what is it what does it give off)?
Intermediate zone - established as the neuroblasts migrate away from the lumen • Contains cell bodies of post-mitotic neuroblasts • Future gray matter of the CNS. Also called mantle layer. • The post-mitotic neuroblasts form axonal and dendritic processes which extend into the marginal zone.
What is the Laryngotracheal groove? Is it a ventral or dorsal evagination?
Laryngotracheal groove (respiratory diverticulum) - precursor of the lungs and trachea. • It is a ventral evagination from the esophageal endoderm of the foregut.
Lateral folding • Right and left sides bend sharply toward the developing _______ surface, narrowing the neck of the yolk sac
Lateral folding • Right and left sides bend sharply toward the developing ventral surface, narrowing the neck of the yolk sac
Lateral folding • The lateral edges initially contact each other at the caudal and cranial regions, then zip shut towards the ________ region
Lateral folding • The lateral edges initially contact each other at the caudal and cranial regions, then zip shut towards the umbilical region
Lateral to that is intermediate mesoderm
Lateral to that is intermediate mesoderm - will form urinary and genital systems
Lateral to that is the flattened sheet of the lateral mesoderm -- will form the
Lateral to that is the flattened sheet of the lateral mesoderm -- will form the coverings of the abdominal organs and lining of the gut, part of dermis
How are the optic vesicles formed?
Lens placode - forms the lens of the eye • Evaginations of the diencephalon called optic vesicles come in contact with the surface ectoderm inducing formation of the lens placode
What is the lining of the trachea? What is the cartilage?
Lining is endoderm and the cartilage is mesoderm
Male-to-female sex reversal in M33 mutant mice
M33 is a protein that controls how other genes are turned on and off
Many of the known imprinted genes have functions in:
Many of the known imprinted genes have functions in: - controlling the growth of the embryo - controlling the development/function of the placenta - brain development - maternal nurturing behavior
Marginal zone (what is it what does it give off)?
Marginal zone - formed by projections (neuronal processes) extending from the neuroblasts • Contains the axons and dendrites of the neuroblast, but not the cell bodies • Future white matter of the CNS.
Maternal blood vessels expand to form _______? What do they do?/
Maternal blood vessels expand to form sinusoids (enlarged blood-filled spaces) that send maternal blood into the lacunae
Meningocele
Meningocele - only meninges protrude thru opening
Development of the Brain Metencephalon: • Cerebellum does what?
Metencephalon: • Cerebellum - controls movements, balance, and posture
Development of the Brain Metencephalon: • Pons does what?
Metencephalon: • Pons (brainstem) - relays signals from the cerebrum to the cerebellum
Nervous system developmental defects: Malformations of the eye What are Microphthalmas?
Microphthalmas, small eyes, are associated with genetic defects and/or intrauterine infections.
What happens to neurons that innervate vs those who do not innervate the muscle?
More neurons than are necessary initially make contact with a muscle • The ones that do not innervate undergo apoptosis • The ones that do innervate are stabilized by trophic factors such as NGF
More severe spina bifida results in physical and/or mental disability
More severe spina bifida results in physical and/or mental disability -Meningocele - only meninges protrude thru opening -Myelomeningocele - spinal cord and meninges protrude thru opening
Are most moles diploid or haploid?
Most moles are diploid but contain only paternal chromosomes. -2 sperm can fertilize an egg with no nucleus -Sperm can fertilize egg with no nucleus then undergo DNA duplication to become diploid
Development of the Brain Myelencephalon: • Medulla oblongata
Myelencephalon: • Medulla oblongata (brainstem) - controls physiological activities such as heart beat and respiration
What process insulates neuronal axons allowing signals to be sent faster?
Myelination insulates neuronal axons, allowing electrical signals to propagate along the axon quickly • Gives white matter its characteristic appearance
Myelomeningocele
Myelomeningocele - spinal cord and meninges protrude thru opening
NTDs result from ______?
NTDs result from a failure of the neural tube to close (at the cranial or caudal neuropore or someplace in between)
What is a nerve?
Nerve = a bundle of axons
Nervous system developmental defects: Malformations of the eye: Name 3...
Nervous system developmental defects: Malformations of the eye Anophthalomia, Microphthalmas, Cyclopia
Nervous system developmental defects: Malformations of the eye What is Anophthalomia?
Nervous system developmental defects: Malformations of the eye Anophthalomia, the absence of an eye, is a result of the failure of the optic vesicle to form on the affected side.
Neural crest cells begin migrating away when?
Neural crest cells begin migrating away as the neural tube is closing -Migration begins at the cranial end and moves caudally in a wave -NC cells form many different cell types
Neural tube defects can largely be prevented by making sure the woman receives adequate________ during early pregnancy
Neural tube defects can largely be prevented by making sure the woman receives adequate folic acid during early pregnancy. -Folate is a B vitamin (B9) found in many vegetables and whole grains -Must be taken very early in pregnancy, often before pregnancy is recognized Some evidence folic acid may also be protective against Alzheimer's Disease and other age-related dementias
What is a Neurite?
Neurite (axon or dendrite) outgrowth is controlled by both intrinsic and extrinsic factors
Neuroblasts of the ________ zone organize into four plates of gray matter which contain the neuronal cell bodies.
Neuroblasts of the intermediate zone organize into four plates of gray matter which contain the neuronal cell bodies.
Neuroblasts of the intermediate zone organize into four plates of gray matter which contain the neuronal cell bodies. • Those in the dorsal neural tube organize into two alar plates (dorsal/sensory horns) Afferent or efferent?
Neuroblasts of the intermediate zone organize into four plates of gray matter which contain the neuronal cell bodies. • Those in the dorsal neural tube organize into two alar plates (dorsal/sensory horns) Afferent
CNS and PNS are made up of 2 major cell types: what are they?
Neurons and Glial Cells
Neurulation begins at the _____ end of the embryo and moves ______
Neurulation begins at the CRANIAL end of the embryo and moves CAUDALLY -Neurulation has begun in the head while gastrulation is still going on in the tail
what is Neurulation?
Neurulation is the process by which the neural tube is formed -The neural tube will form the brain and spinal cord
Non-neural is also known as what? What does it become?
Non-neural (surface) ectoderm becomes the epidermis of the skin, but certain areas of the epidermis will give rise to more complex structures
Name 3 non-placodal derivatives
Non-placodal derivatives • Epidermis • Hair and Nails • Linings of the mouth and anus
Is every gene on X silenced?
Not every gene on the X is silenced however, a small number of genes have counterparts on the Y and so these "escape" X inactivation (to have = dosage)
What prevents embryo from completely folding in half?
Notochord, neural tube, and somites stiffen the dorsal side of the embryo, preventing it from folding completely in half.
Nuclei near the __________ of the neural tube undergo mitosis as they move through the cell cytoplasm toward the lumen (inside of the neural tube)
Nuclei near the external limiting membrane of the neural tube undergo mitosis as they move through the cell cytoplasm toward the lumen (inside of the neural tube)
How do nutrients and oxygen cross vs. Co2 and waste products?
Nutrients and oxygen cross by diffusion from the maternal blood into the fetal blood, and carbon dioxide and waste products cross in the other direction
what are choriocarcinomas? do they occur often?
Occasionally moles form tumors that are usually benign -If they are malignant (rare) they are called choriocarcinomas -Very fast growing and invasive cancer, but the cure rate is high
What does the actual neuron insulation in the CNS?
Oligodendrocytes myelinate neurons in the CNS • A single cell can myelinate several nerve fibers Both kinds can wrap themselves around a nerve process many times
Once radial glial cells are no longer needed to guide neurons, they convert to ________
Once radial glial cells are no longer needed to guide neurons, they convert to ependymal cells.
What is fasciculation?
Other axons follow the pioneering axon and form fascicles, or bundles, of axons • This process is called fasciculation
what is placental abruption?
PREMATURE SEPARATION OF THE PLACENTA FROM THE UTERINE WALL -Treated with bed rest, transfusion, early delivery of the fetus -Occurs in about 1 in 100 pregnancies
Differentiation of ES cells into neurons: What kind of disease could that help?
Parkinson's!
How do peripheral nerves start forming?
Peripheral nerves start forming when a pioneering axon precedes the other axons in the region in growing toward a target
Placenta is made of both fetal and maternal tissues and has 2 components:
Placenta is made of both fetal and maternal tissues and has 2 components: -Chorion - embryonic portion derived from the trophoblast -Decidua - maternal portion derived from the endometrium
What are placental lactogens?
Placental lactogens are protein hormones important for growth of the fetus
Predictions (Haig hypothesis):
Predictions: -imprinted genes will be involved in fetal growth -paternally expressed genes will promote growth -maternally expressed genes will retard growth -imprinting will be absent in oviparous species -imprinting will be absent in monogamous species
what is Preeclampsia? when does it usually occur and what's a sign?
Preeclampsia is a condition where the mother's blood pressure rises dramatically, usually in the 3rd trimester (diagnostic symptom is protein in the urine). Preeclampsia is due to poor development of the placenta, when the villi do not penetrate deeply enough into the endometrium. -Occurs in about ~2-3% of pregnancies -Can lead to stroke, kidney failure in the mother, fetal distress/death -Treated with bed rest, antihypertensives, early delivery of the baby
What are Prenatal corticosteroids used to treat?
Prenatal corticosteroids are used to treat lung development disorders that are associated with immaturity (low surfactant levels). Ex: infant respiratory distress syndrome.
Prenatal diagnosis of NT defects can be done by measuring levels of ________?
Prenatal diagnosis of NT defects can be done by measuring levels of ALPHAFETOPROTEIN -Protein produced by the developing fetus, higher in certain birth defects -Formerly ~50% aborted, can sometimes surgically repair in utero
Primary bronchioles grow out from what?
Primary bronchioles grow out from the tertiary bronchi
Progesterone and estrogen maintain pregnancy (placenta takes over the role of what?)
Progesterone and estrogen maintain pregnancy (placenta takes over the role of the corpus luteum)
Are the Prostaglandins necessary for the onset of labor?
Prostaglandins that are required for the onset of labor
What is Pulmonary hypoplasia?
Pulmonary hypoplasia • Underdevelopment of the lungs • Found frequently in premature infants. • Can be caused by diaphragm hernias, cysts/tumors , dextrocardia, hydrops fetalis. • Symptoms = Reduced lung volume leads to respiratory distress, often death • Treatment = oxygenation, surgical repair of causal disorder, corticosteroids.
Development of neural function: Reflex activity can be detected from #-# weeks.
Reflex activity can be detected from 6- 8 weeks.
The cranial flexure relocates the________ to the future chest
Relocates the cardiogenic region to the future chest
Remember there are two major morphogenetic events that set the stage for embryonic folding...what are they?
Remember there are two major morphogenetic events that set the stage for embryonic folding: Neurulation and Somitogenesis
Respiratory bronchioles grow from what?
Respiratory bronchioles grow from the terminal bronchioles
What does microcephaly result in?
Results in mental retardation. Severity is related to when insult occurs and how small the brain is
What is Rh factor?
Rh factors are proteins on the surface of RBCs in some people
What is the role of the placenta?
Role of the placenta is to bring maternal blood into close contact with the embryonic blood so nutrients and gases can be exchanged -- also an>bodies, bacteria, viruses
What does the actual neuron insulation in the PNS?
Schwann cells (neural crest derived) myelinate neurons in the PNS • A single cell can only myelinate one nerve fiber Both kinds can wrap themselves around a nerve process many times
Secondary (lobar) bronchi grow out from what?
Secondary (lobar) bronchi grow out from the primary bronchi • Three on the right and two on the left • Will eventually give rise to the lobes of the lung
Neural Tube Defects
Seen in ~1 in 500 human births (the 2nd most common human birth defect) For women who had a previous fetus with a NTD, the risk is 1 in 30 to 1 in 50
What does SRY stand for?
Sex determining Region on the Y chromosome
Why does imprinting exist?
Silencing of one allele of a gene should be evolutionarily unfavored - there are advantages to being diploid Suggests there is some benefit conferred by imprinting that overrides the disadvantages
Specialized zones of ependymal cells called choroid plexus cells produce what?
Specialized zones of ependymal cells called choroid plexus cells produce cerebrospinal fluid.
Spina bifida occulta
Spina bifida occulta - a single vertebral arch doesn't close properly -No protrusion of neural tissue -Often asymptomatic, sometimes identified by a dimple in the skin or tuft of hair
Spinal neural crest forms:
Spinal neural crest forms: -Chromaffin cells of adrenal gland -Dorsal root ganglia
5 stages of lung development: Stage 1
Stage 1 - Embryonic stage (4-7 weeks) • Formation of the respiratory diverticulum through formation of tertiary bronchi
5 stages of lung development: Stage 2
Stage 2 - Pseudoglandular stage (8- 16 weeks) • Formation of the rest of the conductive airway • Stops after formation of the terminal bronchioles
5 stages of lung development: Stage 3
Stage 3 - Canalicular stage (17-26 weeks) • Formation of respiratory bronchioles and alveolar ducts from the terminal bronchioles • Blood vessels begin to grow into the lungs, and capillaries become associated with the respiratory bronchioles
5 stages of lung development: Stage 4
Stage 4 - Terminal/saccular/alveolar stage (26 weeks - birth) • Alveoli (terminal air sacs) bud from the alveolar ducts • Type I alveolar cells - gas exchange • Type II alveolar cells - production of pulmonary surfactant
5 stages of lung development: Stage 5
Stage 5 - Postnatal stage (birth - approximately 8 years old) • Mature lungs contain about 300 million alveoli, about 90% of which are formed after birth • This is due to the formation of secondary septa that divide the alveoli
What are stem cells?
Stem cells - cells with the ability to differentiate into a variety of tissues ‐embryonic stem cells, adult stem cells, induced pluripotent stem cells
Steps in primary neurulation:
Steps in primary neurulation: 1. Formation/shaping of the neural plate 2. Bending of neural plate to form the neural groove 3. Closure of the neural tube
what is Placenta previa?
THE PLACENTA LIES OVER THE OPENING OF THE CERVIX -May result from pre-existing scarring of the uterus (infection, surgery) -Can cause severe bleeding during vaginal delivery, C-section recommended -occurs in about 1 in 200 pregnancies
True or False: Lungs are not needed for respiration in utero, but are necessary immediately upon birth.
TRUE Lungs are not needed for respiration in utero, but are necessary immediately upon birth.
Terminal bronchioles grow out from what?
Terminal bronchioles grow out from the primary bronchioles
Tertiary bronchi grow from what?
Tertiary bronchi grow from the secondary bronchi
The ________ secretes enzymes that break down the connections between endometrial cells, and the _______ extends processes that move between the separated cells
The CYTOTROPHOBLAST secretes enzymes that break down the connections between endometrial cells, and the SYNCYTIOTROPHOBLAST extends processes that move between the separated cells
What is The Haig Hypothesis?
The Haig Hypothesis Imprinting is an evolutionary arms race! Imprinting results from the competing interests of the mother and father (working through their genes) to control the growth of their offspring
The _______ and ________ induce the development of the neural plate
The PRECHORDAL PLATE MESODERM and NOTOCHORDAL PROCESS INDUCE the development of the neural plate
Where is the XIST gene located?
The XIST gene is located in the XIC, and is active only on the future Xi (X Inactivation Center _
What is the abembryonic pole?
The abembryonic pole (side opposite the embryo) begins to bulge into the uterine cavity... -This is covered with a thin layer of endometrium called the decidua capsularis -The decidua underlying embryonic pole is called the decidua basalis, it will form the placenta
what is the allantois?
The allantois is an outgrowth of the yolk sac - it grows into the connecting stalk to form the umbilicus that surrounds the blood vessels
The cardiogenic plate is initially located where?
The cardiogenic plate is initially located at the cranial end of the embryo.
The caudal flexure (tail fold): • Brings the _________ to the area of the future anus
The caudal flexure (tail fold): • Brings the cloacal membrane to the area of the future anus
The caudal flexure (tail fold): • Brings the __________ next to the yolk sac, designating the future umbilical area
The caudal flexure (tail fold): • Brings the connecting stalk next to the yolk sac, designating the future umbilical area
What is the caudal flexure? what does it constrict and what does it result in?
The caudal flexure (tail fold): • Constricts the caudal region of the yolk sac • Results in the formation of the hindgut
The caudal flexure (tail fold): Folds the ________ so that it surrounds the dorsal and ventral regions of the of the posterior of the embryo
The caudal flexure (tail fold): • Folds the amniotic cavity so that it surrounds the dorsal and ventral regions of the of the posterior of the embryo
The coelom forms within what? and what does it subdivide?
The coelom begins to form within the lateral mesoderm, subdividing it into the dorsal somatic mesoderm and the ventral splanchnic mesoderm
The contacting trophoblast proliferates to form the _____ The trophoblast surrounding the blastocyst forms the___
The contacting trophoblast proliferates to form the SYNCYTIOTROPHOBLAST The trophoblast surrounding the blastocyst forms the CYTOTROPHOBLAST
The cranial flexure brings the __________ to the area of the future mouth, establishing the ventral surface of the future face, neck and chest
The cranial flexure Brings the oropharyngeal membrane to the area of the future mouth, establishing the ventral surface of the future face, neck and chest
The cranial flexure folds the ________ so that it surrounds the dorsal and ventral regions of the of the anterior of the embryo
The cranial flexure Folds the amniotic cavity so that it surrounds the dorsal and ventral regions of the of the anterior of the embryo.
Which one is wider cranial neural plate or caudal neural plate?
The cranial neural plate is wider, and divided into regions that will form the forebrain, midbrain and hindbrain The caudal neural plate is narrower and forms the spinal cord
what are stem villi?
The cytotrophoblast proliferates and forms extensions that penetrate into the syncy>otrophoblast and then into the lacunae, these are called stem villi
What does the diverticulum do?
The diverticulum elongates and branches forming lung buds. • The straight portion will form the trachea. • The lung buds will give rise to the mature lung.
All three folding events contribute to the following: Explain the "tube within a tube" body plan
The ectoderm, mesoderm, and endoderm layers fuse with each other when they meet along the ventral surface midline, creating a tube within a tube body plan.
how are the blood vessels of the umbilical cord formed?
The extraembryonic mesoderm of the connecting stalk differentiates into the blood vessels of the umbilical cord (two umbilical arteries, one umbilical vein)
Difference between myelin sheath and neurolemma?
The final outer layer enclosing the myelin sheath is the cell body and nucleus of the Schwann cell and is called the neurolemma. • When an axon is damaged, the neurolemma aides in repair and regeneration.
All three folding events contribute to the following: The foregut is capped cranially by the _________, which ruptures by the end of the #th week forming the mouth.
The foregut is capped cranially by the oropharyngeal membrane, which ruptures by the end of the 4th week forming the mouth.
The functional tissues of the respiratory system are made of what?
The functional tissues of the respiratory system are made of endoderm.
All three folding events contribute to the following: The hindgut is capped by the _________, which ruptures at # weeks to form the orifices of the anus and urogenital system.
The hindgut is capped by the cloacal membrane, which ruptures at 7 weeks to form the orifices of the anus and urogenital system.
When does the human blastocyst implant?
The human blastocyst implants at the end of the first week of development
What is the significance of viewing the presence of the "barr body"
The inactive X is silenced by becoming very condensed - most genes are not able to be expressed The super-compacted silent X is visible in cells as a darkly staining structure call the Barr body The presence of the Barr body can distinguish male cells from female cells -useful in forensics
what is the pronephros and how is it formed?
The intermediate mesoderm begins to develop into the pronephros, the earliest kidney
The lateral folds result in what?
The lateral folds: Result in the formation of an endodermal gut tube from the intraembryonic endoderm. Result in the yolk sac and gut becoming two defined structures Midgut is still connected to the yolk sac • Results in the formation of the intraembryonic coelom
The lateral folds: • Folds the amniotic cavity so that it surrounds the ___ and _____regions of the embryo
The lateral folds: • Folds the amniotic cavity so that it surrounds the right and left lateral regions of the embryo
How are the lens and optic cup formed?
The lens placode and vesicle then invaginate to form the lens and the optic cup, respectively. The lens detaches from the surface ectoderm
The lung buds become what? Right primary bronchi = Left primary bronchi =
The lung buds become the primary bronchi • Right primary bronchi = right lung; • Left primary bronchi = left lung
There can even be XX males and XY females - How?
The main sex determining gene on the Y chromosome is called SRY
The most caudal part of the neural tube is formed by (primary/secondary) neurulation?
The most caudal part of the neural tube is formed by 2o neurulation -Arises from the caudal eminence, not from the neural plate -Cells from the caudal eminence form a solid tube that hollows out and joins the cranial neural tube
The mouse Agouti gene encodes a protein that controls what?
The mouse Agouti gene encodes a protein that controls coat color. Mice that express the Agouti gene are yellow, mice that do not express the Agouti gene are dark brown. Increased methylation of the Agouti gene can decrease its expression,causing mice to have varying amounts of brown in their coat.
The neural tube is composed of three distinct layers (zones)...what are they?
The neural tube is composed of three distinct layers (zones): 1. Ventricular (or ependymal) zone 2. Intermediate (or mantle) zone 3. Marginalzone
The neural tube is organized into a ________ epithelium.
The neural tube is organized into a pseudostratified epithelium.
The optic cup and lens then induce the surface ectoderm to form what?
The optic cup and lens then induce the surface ectoderm to form the cornea
The orientation of the metaphase plate determines the fate of the daughter cells • Parallel to the lumen:
The orientation of the metaphase plate determines the fate of the daughter cells • Parallel to the lumen: daughter cell closest to the lumen will continue to be a progenitor cell capable of mitosis, while the daughter cell closest to the basement membrane will become a postmitotic neuroblast (neuron progenitor).
The orientation of the metaphase plate determines the fate of the daughter cells • Perpendicular to the lumen:
The orientation of the metaphase plate determines the fate of the daughter cells • Perpendicular to the lumen: cells will move back to the external limiting membrane and prepare for another round of mitosis
The paraxial mesoderm begins to form rounded structures called __________, moving cranially to caudally
The paraxial mesoderm begins to form rounded structures called somitomeres, moving cranially to caudally
What is the chorion frondosum?
The part of the chorion associated with the decidua basalis is called the chorion frondosum
IN preeclampsia what happens to the placenta as the fetus grows?
The placenta becomes hypoxic as the fetus grows, and secretes factors into the maternal blood that cause endothelial cell changes in the mother -Results in increased maternal blood pressure -A misguided aaempt by the hypoxic placenta to obtain a greater blood supply
The placenta contains # ml of maternal blood at any one time and the blood is exchanged # times/minute?
The placenta contains 150 ml of maternal blood at any one time and the blood is exchanged 3-4 times/minute
How many cell layers thick is the respiratory membrane?
The respiratory membrane (diffusion path length) is two cell layers thick
how is the dermamyotome formed?
The rest of the somite is pushed dorsolaterally, becoming the dermamyotome The dermamyotome subdivides further into: -Dermatome - will form parts of the dermis and connective tissue -Myotome - will form muscle, this then subdivides further into: -Epimere - dorsal, forms deep muscles of the back -Hypomere - ventral, forms lateral and ventral muscles of body wall, limbs
The sclerotome appears when_____? Cells that move out _________, next to the neural tube, will form vertebrae
The sclerotome appears when THE SOMITES DEVELOP A CENTRAL CAVITY AND RUPTURE -Cells that move out VENTROMEDIALLY, next to the neural tube, will form vertebrae -Induction from neural tube is required for vertebrae formation
what forms the somatopleure?
The somatic mesoderm plus the ectoderm is called the somatopleure -Forms the inner lining of the body wall, parts of the limbs and part of the dermis
The somites will form the ______, including the vertebral column, some bones of the skull and muscles of the neck, body wall and limbs, trunk
The somites will form the axial skeleton, including the vertebral column, some bones of the skull and muscles of the neck, body wall and limbs, trunk Somites begin to subdivide, and give rise to specific structures
what forms the splanchnopleure?
The splanchnic mesoderm plus the endoderm is called the splanchnopleure -Forms the coverings of the abdominal organs
Hydrostatic test theory...
The theory: • if the fetus was alive at the time of birth, it would have taken a breath, the lungs would fill with air, and they would therefore float when placed in water • If the fetus was stillborn at the time of birth, it would not take a breath, the lungs would not inflate and would sink when placed into water
The two alar plates are connected dorsally by a ________
The two alar plates are connected dorsally by a roof plate
The two basal plates are connected ventrally by a _______
The two basal plates are connected ventrally by a floor plate
what the heck is Placentophagy?
There are many rituals surrounding the placenta in different cultures -Some Asian and Native American cultures bury the placenta Placentophagy (eating the placenta) is common in many mammalian species -To recover nutrients? -To deter predators? -May contain hormones that stimulate uterine recovery and milk production- a rich and cheap source of protein
There are two types of ectoderm in the early embryo - what are the two types?
There are two types of ectoderm in the early embryo - neural, and non-neural
Development of neural function: There doesn't appear to be neural function in the first # weeks of embryonic development.
There doesn't appear to be neural function in the first 5 weeks of embryonic development.
Tissues that surround the functional tissues (i.e. cartilage, muscle, connective tissues) are derived from what?
Tissues that surround the functional tissues (i.e. cartilage, muscle, connective tissues) are derived from splanchnic mesoderm.
What is the trachea?
Trachea (windpipe) - connects the pharynx/larynx to the lungs • Lining is endoderm and the cartilage is mesoderm
Malformations of the Lungs: TEF...
Tracheoesophageal fistula (TEF) - an • Abnormal connection between the trachea and the esophagus, usually due to a failure of the tracheoesophageal ridges to fuse. • Co-occurs with esophageal atresia (EA) • Symptoms = problems feeding and abdominal distention • Treatment = surgical repair
TEF and co-occurs... with what?
Tracheoesophageal fistula (TEF) - an • Abnormal connection between the trachea and the esophagus, usually due to a failure of the tracheoesophageal ridges to fuse. • Co-occurs with esophageal atresia (EA) • Symptoms = problems feeding and abdominal distention • Treatment = surgical repair
Two classes of cells arise from the proliferating neuroepithelial cells...what are they?
Two classes of cells arise from the proliferating neuroepithelial cells; neuroblasts and glioblasts.
Two depressions appear in the ectoderm, one cranially and one caudally what are they?
Two depressions appear in the ectoderm, one cranially and one caudally -Where ECTODERM HAS ADHERED TO THE ENDODERM and excluded mesoderm -The oropharyngeal membrane (buccopharyngeal) and the cloacal membrane
What layer is excluded in the two depressions?
Two depressions appear in the ectoderm, one cranially and one caudally -Where ectoderm has adhered to the endoderm and EXCLUDED MESODERM -The oropharyngeal membrane (buccopharyngeal) and the cloacal membrane
What are two types of epigenetic modifications?
Types of epigenetic modifications: DNA methylation, histone protein modifications Epigenetics regulates processes that must be stable through cell division, but also reversible at some point (for example in the germline)
how does umbilical blood vessel nomenclature differ from the rest of the body?
Umbilical blood vessel nomenclature differs from the rest of the body: -The umbilical arteries carry deoxygenated blood from the embryo to the placenta -The umbilical vein carries oxygenated blood from the placenta to the embryo
Upon birth, the fluid needs to be quickly removed and replaced with what?
Upon birth, the fluid needs to be quickly removed and replaced with oxygen.
Vacuoles called _____________ appear within the syncytiotrophoblast
Vacuoles called trophoblastic lacunae appear within the syncytiotrophoblast
Explain the Ventral/motor horns?
Ventral/motor horns: • Formation of peripheral nerves begin when motor neuroblasts of the ventral horn begin to grow • Axons grow from the cells body to the periphery • These axons are now called ventral roots
Ventricles and central canal form from the _____ of the neural tube.
Ventricles and central canal form from the lumen of the neural tube.
Ventricular zone (what is it what does it give off)?
Ventricular zone - the inner margin (near the central canal) where mitosis takes place • Gives rise to neuroblasts and glioblasts (future supporting cells) which migrate into the intermediate zone.
Somitogenesis (# week of development): As the primitive streak regresses, mesoderm on each side of the notochord forms cylindrical structures called
Week 3 As the primitive streak regresses, mesoderm on each side of the notochord forms cylindrical structures called PARAXIAL MESODERM (segmental plate mesoderm) -Will form axial skeleton, part of dermis of the skin
When all neuroblasts and glioblasts have been formed, the remaining cells in the ventricular layer also differentiate into what?
When all neuroblasts and glioblasts have been formed, the remaining cells in the ventricular layer also differentiate into ependymal cells. These cells line the cerebral ventricles and the central canal of the spinal cord.
X Chromosome Inactivation: What is dosage compensation?
X chromosome has lots of important genes and a double dosage of the X is lethal Dealing with this problem is called dosage compensation: -Female mammals do this by silencing most genes on one of their two Xs -This is called X-inactivation, and which X is silenced is random
When does x-inactivation occur in the process?
X-inactivation occurs early in development (shortly after implantation), so as cells continue to divide there become "clones" of cells with the same X inactive
X-linked Diseases: What are X-linked Diseases?
X-linked Diseases -Diseases for which the causative gene lies on the X chromosome -These diseases affect males but not females, who are carriers
X Chromosome Inactivation: Which (between X and Y) is gene expression problem more serious on?
Y genes aren't an issue - there is nothing much on the Y except genes for being male. X chromosome has lots of important genes and a double dosage of the X is lethal
Does placenta structure vary?
YES Placental structure can be very different among even closely related mammals
Do maternal antibodies cross into fetal circulation?
YES Maternal antibodies cross into the fetal circulation where they can persist for several months aSer birth, helping protect the infant until it's own immune system develops
Does the placenta produce growth factors and hormones or nah?
YES!! The placenta produces many growth factors and hormones Progesterone and estrogen Human chorionic gonadotropin (hCG) Placental lactogens are protein hormones important for growth of the fetus. Prostaglandins that are required for the onset of labor.
What are the symptoms of BWS? What is BWS a double dosage of?
double insulin growth factor -in BWS, both IGF2 alleles are active - A DOUBLE DOSE OF THIS GROWTH FACTOR Symptoms of BWS: Somatic overgrowth; Organomegaly; Macroglossia; Embryonic tumors
How is the XIST gene turned on?
early in female development one X turns on the XIST gene
how much does a full-term placenta weigh?
full-term human placenta weighs 450-500g, or about 1 pound
humans # somites form, but the _____-most disappear, giving # final somites
humans 42-44 somites form, but the caudal-most disappear, giving 37 final somites
What are iPS cells? Can iPS cells solve stem cell dilemma?
iPS cells are induced pluripotent stem cells - differentiated cells that are "turned back" into embryonic stem cells by adding back 3‐4 pluripotency genes (Oct‐4, Sox2, c‐Myc, Klf4). These have promising clinical potential, and can be generated from a patient's own cells
What do filopodia do?
sense the external environment • Filopodia are consistently extending and retracting in an attempt to correctly survey the surrounding environment
What does the XIST gene make (and not make)?
the XIST gene makes an RNA, but no protein
adult stem cells circumvent many of the ethical issues of embryonic stem cells, but have disadvantages...like what?
‐Supply is typically limiting - must come from a donor, or be harvested from the patient (if possible) ‐They can be very difficult to isolate from many adult tissues ‐Uses are restricted to cell types the stem cells would normally form Current uses being explored: Pancreatic islet cell transplantation Neuronal cell transplantation - Parkinson's Disease, spinal cord injury, etc.
Where are all placodes formed from?
• All placodes are formed from the preplacodal region, which encircles the cranial neural plate
Infant Respiratory Distress Syndrome due to lack of what?
• Associated with premature infants, gestational diabetes. Due to lack of surfactant. Infant Respiratory Distress Syndrome • Formerly called hyaline membrane disease because of lung histology • Symptoms = difficulty breathing, cyanosis
Example of Contact repulsion:
• Caudal half of the somite prevents the ingrowth of motor neurons
True or False the nuclei of the CNS cells migrate back and forth during each cell cycle?
• Cell nuclei are at different heights, giving the appearance of multiple cell layers • The nuclei of these cells migrate back and forth during each cell cycle.
What do axons do vs. what do dendrites do?
• Dendrites pick up electrical impulses from other cells • Axons transmit messages to/from the spinal cord
Elongated neuroepithelial cells span from the external limiting (basement) membrane to what?
• Elongated neuroepithelial cells span from the external limiting (basement) membrane to the central canal of the spinal cord.
What does Endoneurium surround?
• Endoneurium: surrounds individual neurons and their Schwann cells
Connective tissue surrounds axons and Schwann cells (what are the three layers called?):
• Endoneurium: surrounds individual neurons and their Schwann cells • Perineurium: surrounds axon groups to form fascicles (bundles of axons) • Epineurium: surrounds the entire nerve (bundles of fascicles)
What does Epineurium surround?
• Epineurium: surrounds the entire nerve (bundles of fascicles)
What is the gustatory placode going to form?
• Gustatory placode - forms the taste buds
Experiments have been conducted that demonstrate the relationship between nerve formation and the presence of a target tissue: • In experiments where a limb has been deleted before neurite outgrowth, there is a decrease in the number of motor neurons and size of the sensory ganglia in the spinal cord at the level of the deletion
• In experiments where a limb has been deleted before neurite outgrowth, there is a DECREASE in the number of motor neurons and size of the sensory ganglia in the spinal cord at the level of the deletion
Toxoplasmosis infection incidence and presentation
• Incidence is 1 in 1000-8000 births per year in the U.S. • Microcephaly, nystagmus, bulging fontanelle, seizure • Macrocephaly due to hydrocephalus.
What does the lens placed form?
• Lens placode - forms the lens of the eye
Experiments have been conducted that demonstrate the relationship between nerve formation and the presence of a target tissue: • Limb graft experiments show an (increase/decrease) in the number of motor neurons and the size of the sensory ganglia in the spinal cord at the level of the graft
• Limb graft experiments show an INCREASE in the number of motor neurons and the size of the sensory ganglia in the spinal cord at the level of the graft
Development of the Brain Mesencephalon: • Midbrain does what?
• Mesencephalon: • Midbrain (brainstem) - visual relay system; coordinate visual and auditory reflexes
What allows the cerebrospinal fluid to flow from the 3rd to the 4th ventricle
• Mesencephalon: cerebral aqueduct (aqueduct of Sylvius) - allows cerebrospinal fluid to flow from the 3rd to the 4th ventricle
What forms the upper part of the 4th ventricle? What forms the lower part of the 4th ventricle?
• Metencephalon: upper part of 4th ventricle • Myelencephalon: lower part of 4th ventricle
Neural folds form along the embryo, with the midline depression forming what?
• Neural folds form along the embryo, with the midline depression forming the neural groove.
• Neural folds meet in the midline and fuse to form what?
• Neural folds meet in the midline and fuse to form the neural tube.
What is the olfactory placode the precursor to?
• Olfactory placode - precursor of the nasal cavity epithelium
What are the Placodal derivatives? (4)
• Olfactory placode - precursor of the nasal cavity epithelium • Gustatory placode - forms the taste buds • Otic placode - forms the inner ear • Lens placode - forms the lens of the eye
What is Hydrocephalus?
• One cause is a blockage in the cerebral aqueduct (aqueductal stenosis) • Incidence is 1-2 per 1000 births in U.S. ...too much CSF in brain
What does the otic placode form?
• Otic placode - forms the INNER ear
What does Perineurium surround?
• Perineurium: surrounds axon groups to form fascicles (bundles of axons)
Example of Contact attraction:
• Proteins of the growing neurite can bind the proteins fibronectin and laminin
Unmyelinated axons: Where are they located? How does conduction speed change?
• Rest in invaginations of Schwann cells or oligodendrocytes. • Not wrapped around the axon. • Conduct action potentials slowly. • Generally shorter, which makes conduction speed less important.
Example of Chemorepulsion:
• Semaphorins
Formation of the intraembryonic coelom: ________will line the body wall of future cavities
• Somatic mesoderm will line the body wall of future cavities
What are placodes and what forms them?
• Specific areas of the epidermis will form placodes - ectodermal thickenings • Epidermal derivatives can be placodal or non-placodal • All placodes are formed from the preplacodal region, which encircles the cranial neural plate
Formation of the intraembryonic coelom: _________ will cover future organs
• Splanchnic mesoderm will cover future organs
Development of the Ventricles: What develops first two, what develops third?
• Telencephalon: 1st and 2nd (lateral) ventricles • Diencephalon: 3rd ventricle
The cells of the __________ will go on to form specific brain regions.
• The cells of the NEURAL TUBE will go on to form specific brain regions. • The lumen of the neural tube will become the fluid-filled ventricles of the brain.
How is the otic vesicle formed?
• The hindbrain induces the overlying ectoderm to form the otic placode which invaginates to form the otic vesicle
Formation of the intraembryonic coelom: The intraembryonic coelom will give rise to what three cavities?
• The intraembryonic coelom will give rise to the pericardial, pleural, and peritoneal cavities.
What forms the ectoderm?
• The neural plate forms from ectoderm
The diverticulum elongates and branches forming lung buds: The________ will form the trachea. The_______ will give rise to the mature lung.
• The straight portion will form the trachea. • The lung buds will give rise to the mature lung.
What are the alar plates?
• Those in the dorsal neural tube organize into two alar plates (dorsal/sensory horns) • The two alar plates are connected dorsally by a roof plate • The alar plates are composed of afferent neurons that carry sensory information toward the CNS
What are the basal plates?
• Those in the ventral neural tube organize into two basal plates (ventral/motor horns) • The two basal plates are connected ventrally by a floor plate • The basal plates are composed of efferent neurons that carry motor information away from the CNS
how is congenital toxoplasmosis formed?
• Toxoplasmosis infection can be passed from mother during gestation causing congenital toxoplasmosis. • Parasitic disease caused by protozoan Toxoplasma gondii. • Primary host is cats. Transferred to humans by contact with cat fecal matter or undercooked meat (lamb, pork).
Difference between type I and type II alveolar cells
• Type I alveolar cells - gas exchange • Type II alveolar cells - production of pulmonary surfactant
Example of chemoattraction:
•Netrins
Can epigenetic processes be altered?
Epigenetic processes can be altered in many ways by the environment (through diet and other exposures) Natural and synthetic hormones Environmental chemicals like polychlorinated biphenyls (PCBs) and plasticizers Drugs and toxins (i.e. heavy metals) can alter cell methylation levels Nutrition, i.e. changes in the intake of methyl donors can alter DNA methylation -there is evidence that early nutrition can play a role in the life-long susceptibility to disease (Dutch Hunger Winter of 1944)
