BSC Embryo 1 Flashcards
exam
what are the 3 anatomical planes? describe each
1) sagittal plane: vertical plane that divides the body into left and right
2) coronal plane: vertical plane that divides the body into front (anterior) and back (posterior)
3) transverse plane: horizontal plane that divides the body into upper (superior) and lower (inferior)
what are synonyms to superior and inferior?
cranial (superior) and caudal (inferior)
what guides embryonic development?
the genome
1) how many chromosomes does the human genome possess?
2) how are they arranged?
3)give detail about their sex characteristics
1) 46 chromosomes total
2) arranged in 23 pairs (from maternal and paternal parent)
3) 22 autosomal pairs, 1 pair of sex chromosomes
what does 1 gene lead to?
many different proteins
what do proteins regulate?
gene expression and act as signaling molecules
what is induction? describe what an inducer does
one group of cells or tissue causes another to change their fate
- INDUCER PRODUCES A SIGNAL AND RESPONDER REACTS TO THE SIGNAL
- ability to respond is called competence
- this process induces cells to differentiate into the tissues that make up our body
what kind of signaling is essential for induction
cell- to- cell
what is paracrine signaling
SIGNALING USING DIFFUSIBLE FACTORS
- signaling molecules (LIGAND) is released from cell 1
- RECEPTOR on cell 2 receives signaling molecule
what is an example pathway for embryogenesis (cell-to-cell signaling)
SONIC HEDGEHOG (SHH) MASTER GENE OF EMBRYOGENESIS
- involved in development of vasculature, left-right axis formation, cerebellum, neural/ smooth muscle patterning, limbs, heart, gut, pharynx, lungs, pancreas, kidneys, bladder, hair follicles, teeth, thymocytes, inner ear, eyes, and taste buds
- mutation and uncontrolled activation in this pathway has been implicated in cancers and congenital syndromes
what is the extracellular matrix
- substances secreted by cells into the tissue that surrounds them
- acts as structural support, communication between cells, cell movement and other functions
why is cell-to-cell signaling essential?
for induction to continue
which factors do juxtacrine signaling use? what are the 3 types of juxtacrine signaling?
- uses non- diffusible factors
1) protein on cell 1 SURFACE interacts with receptor on adjacent cell 2 SURFACE
2) receptor on cell 1 binds to ligand in the ECM SECRETED BY CELL 2
3) signal is transmitted directly from the cytoplasm of cell 1 through gap junctions into the cytoplasm of adjacent cell 2
what is the term for “small conduits” in cells
gap junctions
why do signaling errors may occur
genetic or environmental factors or BOTH
what is an example of a signaling error
SITUS INVERSUS: CONDITION WHERE THE POSITIONING OF ALL ORGANS IS REVERSED IN A MIRROR IMAGE ARRANGEMENT
what is heterotaxy?
ONE OR MORE ORGANS IS ABNORMALLY PLACED
what is gametogenesis
THE PROCESS BY WHICH GAMETES (GERM CELLS) ARE PRODUCED IN AN ORGANISM
describe the steps of gametogenesis
1) ova/ egg cell forms thru oogenesis
2) sperm forms thru spermatogenesis
3) gametes are derived from PGCs in the 2nd week of fetal development
4) PGCs arrive in the developing gonads of the genetically female or male embryo by 5th week
what is the term for female gamete? male gamete?
- ova/ egg cell
- sperm
what are PGCs
primordial germ cells
describe the overview of mitosis
- primordial germ cells (future mature gametes) first undergo mitosis
- cell division -> 2 daughter cells that are genetically identical
- each cell receives the complete complement of 46 chromosomes
describe the overview of meiosis
- future mature gametes then must undergo meiosis to REDUCE CHROMOSOME NUMBER (this process completes at different times in males and females)
- 2 successive meiotic divisions: meiosis I and meiosis II
- results in reduction of chromosomes from diploid (46) to haploid (23)
briefly describe meiosis I and meiosis II
meiosis I reduces chromosome number to 23
meiosis II resembles mitosis
what is a diploid
a cell or organism that has paired chromosomes, one set from each parent -> 2n
what is haploid
a cell or organism that has a single set of chromosomes, 1n
what is oogenesis
THE PROCESS BY WHICH OOGONIA BECOME MATURE OOCYTES
what happens to cells during oogenesis around the 5th week? at 3 months?
- PCGs undergo mitosis, enter the female gonad @ 5th week, and differentiate to oogonia
- @ 3 months: some oogonia cells synchronously arrest division in prophase of meiosis 1 ->PRIMARY OOCYTES
when are primary oocytes formed
ALL PRIMARY OOCYTES ARE FORMED BEFORE BIRTH
when are oocytes arrested
primary oocytes ARRESTED IN PROPHASE 1 REMAIN ARRESTED UNTIL PUBERTY
what is/ are the resulting cell(s) in oogenesis?
1 PRIMARY OOCYTE ONLY PRODUCES 1 MATURE GAMETE
what is the overall result if fertilization occurs? what occurs if it does not?
1 PRIMARY OOCYTE-> 1 MATURE OOCYTE AND POLAR BODIES
- polar bodies are not fertilized and degenerate
- OVARIAN FOLLICLES are simultaneously undergoing maturation and provide the support for oocyte growth and maturation
- CORPUS LUTEUM secretes hormones to prepare the uterus for pregnancy
- if fertilization doesn’t occur, corpus luteum degenerates to CORPUS ALBICANS
define spermatogenesis
process of sperm cell development
what are the steps of spermatogenesis
- PGCs ARRIVE IN THE SPERMATOGONIA, UNDERGO SEVERAL CYCLES OF MITOSIS, AND THEN ENTER MITOTIC ARREST
- spermatogonia remain dormant until puberty when spermatogenesis begins
describe the haploid/ diploid evolution of spermatogenesis
spermatogonia (2n) -> spermatocyte stages (2n -> n) -> spermatids (n) -> mature spermatozoa (n)
how long does spermatogenesis last? describe the 2 significant features
- about 74 days
1) NO FORMATION OF POLAR BODIES
2) 1 PRIMARY SPERMATOCYTE -> 4 MATURE SPERMATOZOA
compare oogenesis vs. spermatogenesis
oogenesis
- finite pop. of oocytes established by birth
- 1 gamete per meiosis completion
- meiosis begins during fetal period, arrests, and resumes at puberty
spermatogenesis
- continuous stem cell pop.
- 4 gametes per meiosis completion
- meiosis begins at puberty
how many pregnancies end in miscarriage? how many are affected by chromosomal abnormalities? when do they occur?
- 50% of all pregnancies end in miscarriage, usually within 2-3 weeks before woman realizes she is pregnant
~ 50% result from chromosomal abnormality, limits birth defects to 2-3% of infants
what two pathways result due to alternate chromosome number? give examples for both categories
1) extra chromosomes ex. trisomy 21, Klinefelter syndrome XXY
2) fewer chromosomes ex. monosomy; Turner syndrome XO
what is trisomy 21
3 copies of chromosome 21
what is monosomy
absence of a chromosome from a pair
what are general features of trisomy 21?
- abnormality due to presence of extra copy of chromosome 21
- prevalence in the US is 13.65 per 10,000 livebirths
- karyotype analysis is diagnostic
what are the clinical features of trisomy 21
- varying degrees of intellectual disability
- craniofacial abnormalities (upward slanting eyes, epicanthal folds, flat facies, small ears)
- cardiac defect
- hypotonia
- INCREASED RISK OF LEUKEMIA, INFECTIONS, thyroid dysfunction, and premature aging
what are the head and neck manifestations of trisomy 21
MACROGLOSSIA, GINGIVITIS, PREMATURE PERIODONTITIS
what do certain genetic conditions depend upon?
which parent the defective or missing gene arises from
what is the concept of genomic imprinting
- 2 copies of each gene (1 from each parent) are inherited by offspring
- if a gene from parent 1 IS IMPRINTED, IT IS SILENCED, AND THEREFORE GENE EXPRESSION IN THE OFFSPRING IS ONLY BASED ON PARENT 2
what is an example of genomic imprinting
paraganglioma syndrome
- mutations can be inherited from either parent but ONLY paternal transmission conveys disease b/c maternal gene is imprinted
what is the diagnostic tool to identify genetic abnormalities?
CYTOGENETIC ANALYSIS
- EXAMINATION OF THE NUMBER OF THE PLOIDY AND THEIR INTEGRITY
what is ploidy? aneuploidy?
ploidy: number of sets of chromosomes in a cell
aneuploidy: 1+ extra/ missing chromosomes resulting in an unbalanced chromosome complement
- ex. a cell w/ 49 or 43chromosomes
what is cytogenetic analysis useful for
- looking at chromosomes in detail for prenatal assessment, assessing miscarriage cause, postnatal diagnosis of solid organ malignancies, hematologic malignancies, congenital diseases
what are the 3 specific testing modalities for identifying genetic abnormalities
1) FLUORESCENT IN SITU HYBRIDIZATION (FISH)
2) MICROARRAYS
3) EXOME SEQUENCING
describe the FISH specific testing modality
- fluorescent in situ hybridization
- FLUORESCENT DNA PROBES TO IDENTIFY SPECIFIC CHROMOSOMES OR ABNORMALITIES
- ex: probe for chromo21 will show 3 copies in a single cell in trisomy 21 (attaches in 3 places)
describe the microarrays specific testing modality
small sequences of DNA on chips act as probes to detect mutations
describe the exome sequencing specific testing modality
only coding regions of DNA are sequenced and assessed for abnormalities
how does development of a gamete begin?
FERTILIZATION - USUALLY OCCURS IN AMPULLA OF FALLOPIAN TUBE
- HAPLOID GAMETES FUSE TO FORM DIPLOID ZYGOTE
what cells does the term gametes include
sperm and oocyte
what makes up an oocyte
from female, 22 autosomal chromosomes + 1 sex chromosome (X)
what makes up a sperm
from male, 22 autosomal chromosomes + 1 sex chromosome (X or Y)
what is a genetic male zygote? female zygote?
male zygote: XY, Y chromosome carries SRY gene
female zygote: XX, absence of SRY gene
what does the SRY gene do? what occurs if it is not present?
present: dictates testis differentiation
not present: ovary development
how long is the embryonic period
0-8 weeks
what is the first step of the embryonic period? describe
- zygote undergoes a series of mitotic divisions
-> starts at 2 cell stage (both cells called blastomeres), moves to 4 cell stage, then becomes morula @ 16 cells at 3 days - begins to separate into INNER CELL MASS AND OUTER CELL MASS
describe blastocyst formation that occurs during embryonic development. what are the steps before and after this stage
-morula travels to uterine cavity, fluid begins to penetrate and forms a single cavity called BLASTOCELE
- EMBRYO AT THIS STAGE IS CALLED THE BLASTOCYST
- blastocyst implants in endometrium along anterior/ posterior wall
-INNER CELL MASS= EMBRYOBLAST, OUTER CELL MASS= TROPHOBLAST
- step before is zygote undergoing mitotic divisions, step after is week of 2s
what are properties of the inner cell mass
- source of embryonic stem cells
- embryonic stem cells are PLURIPOTENT including cells from ALL 3 GERM LAYERS (ECTODERM, MESODERM, ENDODERM)
what does pluripotent mean
able to give rise to many different cell types
what occurs during abnormal implantation? describe
- implantation outside uterus can take place and results in an extrauterine pregn. or ECTOPIC PREGNANCY
- can occur any place in abdominal cavity, ovary, uterine tube
- 95% occur in fallopian tube
- if left to grow can cause adjacent organ damage or life threatening blood loss
what happens to maternal immunity while an embryo is forming
- WOMEN IN ORDER TO NOT REJECT THE EMBRYO NEED TO UNDERGO IMMUNE SYSTEM SHIFT, from cell- mediated to humoral (antibody- mediated)
- not fully understood, but MAY INCREASE MOTHERS’ RISK OF INFECTIONS
how can the change in maternal immunity during embryo dev. alter symptoms of a mother’s autoimmune diseases? give examples
ex: multiple sclerosis & RA are cell mediated and show improvement during preg.
ex. SLE is predominantly antibody mediated and may worsen during preg.
what occurs during the second week of embryo development
- HUMAN CHORIONIC GONADOTROPIC (hCG) hormone is in significant quantities to be detected and are used for PREGNANCY TESTING
- week of 2s
-> trophoblast differentiates into 2 layers
-> embryoblast forms 2 layers
-> 2 cavities form: amniotic and yolk sac
-> extraembryonic mesoderm splits into two layers
what 2 layers does the trophoblast differentiate into? the embryoblast? what 2 cavities form during week of 2s
- tropho: cytotrophoblast and syncytiotrophoblast
- embryo: epiblast and hypoblast
- amniotic and yolk sac cavities
what specifically happens during week 1and week 2 of embryo development? what is the overall result?
week 1: trophoblast cells invade into uterine wall for implantation
week 2: trophoblast splits into cytotrophoblast (inner) and synctiotrophoblast (outer)
overall: these structures are important to FORMATION OF MUCH OF THE PLACENTA
how are body axes established during embryo development
- embryoblast differentiates into epiblast and hypoblast
-> these cells migrate and orient such that EPIBLAST IS DORSAL AND HYPOBLAST IS VENTRAL
-> both of these layers together form the BILAMINAR DISC - some cells of the hypoblast differentiate into the AVE
-> AVE CELLS MIGRATE TO FUTURE CRANIAL SITE OF EMBRYO AND ARE IMPORTANT FOR SIGNALING BODY AXES
what is AVE
anterior visceral endoderm
during embryoblast formation what structures do we start to see on the embryo
- AMNIOTIC CAVITY: small cavity appears within epiblast
- PRIMITVE YOLK SAC: cavity forms between hypoblast and exocoelomic membrane (formed from cells of hypoblast)
describe what the yolk sac is and important features
- early pregnancy structure that provides nutrients to growing embryo
- absorbed by the embryo sometime between 10-14 weeks
- cells of the yolk sac are important in forming other structures
what 3 structures are formed by the cells of the yolk sac
1) ORIGIN OF THE FIRST BLOOD CELLS
2) UMBILICAL CORD
3) REPRODUCTIVE STRUCTURES
discuss yolk sac tumors
- rarely occur
- can occur anywhere in the body but most common to ovary or testicle
- most common malignant germ cell tumor of children
what happens when the extraembryonic mesoderm develops? what is it derived from?
- splits into 2 layers: extraembryonic splanchnic mesoderm & extraembryonic somatic mesoderm
- large cavities form between the layers -> CHORIONIC CAVITY
- derived from yolk sac cells
what is the amnion
refers to a membranous structure which covers and protects the embryo (inside chorion)
what is the chorion
double- layered membrane formed by the trophoblast and extra- embryonic mesoderm, which eventually will give rise to the fetal part of the placenta
what characteristic does week 3 of the embryonic have? describe important events during this period
- the trilaminar disc
- gastrulation is most characteristic event
- begins in the head region and then moves caudal until end of the 4th week
what is gastrulation?
THE PROCESS THAT ESTABLISHES ALL THREE GERM LAYERS IN THE EMBRYO
- starts with bilaminar disc (epiblast + hypoblast) -> trilaminar disc
1) ectoderm
2) mesoderm
3) endoderm
describe the specifics of gastrulation
- primitive streak appears at the caudal aspect of embryo
-> cranial aspect of streak thickens and forms primitive node - cells of the epiblast begin to invaginate
-> 1st wave of cells migrating thru the streak interdigitate w/ hypoblast layer -> ENDODERM
->2nd wave -> MESODERM
-> remaining cells in epiblast layer is ECTODERM
what do the ecto/meso/endoderm layers give rise to
ALL ORGANS AND TISSUES OF THE EMBRYO
describe the steps for formation of the notochord and how mouth and anus openings develop
- prenotochordal cells migrate thru the primitive streak, become intercalated in the endoderm to form the notochordal plate
- plate detaches from endoderm -> NOTOCHORD
- NOTOCHORD FORMS TH EMIDLINE AXIS WHICH SERVES AS BASIS OF AXIAL SKELETON
- mouth: oropharyngeal membrane eventually breaks down
- anus: cloacal membrane breaks down
what are key features of weeks 3-8 for the embryonic period
- period of organogenesis
- by the end main organ systems established
- THIS TIME AT GREATEST RISK FOR INDUCTION OF BIRTH DEFECTS
-> SENSITIVE TO GENETIC AND ENVIRONMENTAL IMPACTS
what structures are derived from the ectoderm layer
1) CNS ( BRAIN & SPINAL CHORD)
2) PERIPHERAL NERVOUS SYSTEM
3) SENSORY EPITHELIUM OF EARS, EYES, AND NOSE
4) EPIDERMIS
5) HAIR AND NAILS
6) SUBCUTANEOUS GLANDS
7) MAMMARY GLANDS
8) PITUITARY GLAND
9) ENAMEL OF THE TEETH
what is neurulation?
PROCESS BY WHICH THE ECTODERM (GUIDED BY NOTOCHORD) FORMS THE NEURAL PLATE WHICH THEN BENDS UPWARD AND FUSES -> NEURAL TUBE
what does neurulation result in?
- segregation of 3 ectodermal derivatives: NEURAL TUBE, NEURAL CREST, AND EPIDERMIS
-> NEURAL TUBE WILL BECOME THE CRANIAL END AND CAUDAL END (SPINAL CORD)
how are neural crest cells formed? where do they go? what are they involved in?
- during formation of neural tube the lateral border/ crest cells dissociate
- NEURAL CREST CELLS MIGRATE ALL ALONG THE TUBE IN 5 GROUPS THAT FORM SPECIFIC STRUCTURES
1) cranial
2) cardiac
3) vagal
4) trunk
5) sacral - INVOLVED IN AT LEAST 1/3 OF ALL BIRTH DEFECTS AND MANY CANCERS
what structures are derived from the mesoderm layer
1) SUPPORTING TISSUES
- MUSCLE
- CARTILAGE
- BONE
- DERMIS OF THE SKIN (CT, NERVES)
2) VASCULAR SYSTEM
- HEART
- ARTERIES
- VEINS
- LYMPH VESSELS, ALL BLOOD AND LYMPH CELLS
3) UROGENITAL SYSTEM
- KIDNEYS
- GONADS
- DUCTS
4) SPLEEN
what structures are derived from the endoderm layer
1) LINING
- EPITHELIAL LINING OF: GI TRACT, RESPIRATORY TRACT, URINARY BLADDER, URETHRA, TYMPANIC CAVITY, AUDITORY TUBE
2) GASTROINTESTINAL TRACT
3) THYROID
4) PARATHYROID
5) LIVER
6) PANCREAS
what is occurring in the ectoderm layer while neurulation is happening
- SIMULTANEOUSLY ENDODERM ROLLS DOWN TO FORM THE GUT TUBE (FUTURE GI TRACT)
- embryo at this stage consists of a tube on top of a tube
-> neural tube dorsal
-> gut tube ventral
what is occurring in the mesoderm layer while neurulation is happening
- TWO TUBES ARE HELD TOGETHER BY THE MESODERM
- mesoderm splits into VISCERAL AND PARIETAL LAYERS
- between visceral and parietal layers in the primitive body cavity
- lateral body walls fold ventrally and fuse at midline to create a closed body cavity except in the region connected by the stalk
-> connecting stalk will become umbilical cord
what are the fates of visceral vs. parietal layers? give 3 examples
- visceral layer ultimately covers various organs
- parietal layer ultimately lines various body cavities
- between the 2 layers is body cavity space w/ fluid
ex 1: lungs- visceral and parietal pleura
ex 2: heart- visceral and parietal pericardium
ex 3: abdomen- visceral and parietal peritoneum
when is the fetal period
3rd month -> birth
what are important characteristics during the fetal period
- maturation of organ systems
- rapid growth occurs during this time
-> length ~ 5 cm/ month for 3rd-5th months
-> weight: there is a striking increase in last 2 months
what are highlights for month 3 of the fetal period
- face becomes more recognizable
- eyes move from lateral to ventral
- limbs extend
- primary ossification centers are present in long bones and skull
- external genitalia develops to a degree that sex can be determined on ultrasound
describe the gut tube
- divided into 3 regions: foregut, midgut, and hindgut
- midgut communicates w/ yolk sac by way of a broad stalk, the vitelline (yolk sac) duct
-> gets nutrients to fetus
what are highlights for month 4&5 of the fetal period
- fetus lengthens rapidly (end of 5th months weight is still <500g, minimal subcutaneous fat)
- fetus is covered with fine hair
- eyebrows and head hair are visible
- movements are felt by mother by 5th month
what are highlights for month 6&7 of the fetal period
- fetus born early in 6th month has difficulty surviving
-> respiratory system and CNS have not differentiated sufficiently - coordination between the systems needed for breathing isn’t well established
- by 6.5-7 months, fetus has a CRL of ~25cm and weighs ~1100g
-> BORN AT THIS TIME, THE INFANCT HAS A 90% CHANCE OF SURVIVING
what is CRL? CHL?
CRL: crown-rump length (sitting height)
CHL: crown-heel length (measurement from vertex of the skull to the heel, standing height)
what are highlights for month 8 of the fetal period
- skull has largest circumference of all parts of the body
- at the time of birth, weight of a normal fetus is 3-3400g
-CRL is ~36cm and CHL ~50cm - most fetuses are born w/in 10-14 days of calculated delivery date
-> POSTMATURE/ PREMATURE
what is the placenta and what are its two components?
- placenta is a fetomaternal organ
- fetal component (chorion) & maternal component
-> fetal derived from the trophoblast & extraembryonic mesoderm
-> maternal derived from uterine endometrium
what are the 5 functions of the placenta?
1) PROTECTION
2) NUTRITION
3) RESPIRATION
4) EXCRETION
5) HORMONE PRODUCTION
what is the amnion? what does it do?
- LARGE SAC CONTAINING AMNIOTIC FLUID IN WHICH THE FETUS IS SUSPENDED BY ITS UMBILICAL CORD
1) absorbs jolts
2) allows for fetal movements
3) prevents adherence of the embryo to the amnion
describe amniotic fluid and its key features
- derived primarily from the maternal blood
- volume is replaced every 3 hours
- increases throughout pregn. from ~30mL @ 10wks to 1000mL near delivery
- EITHER HYDRAMNIO OR OLIGOHYDRAMNIOS IS ASSOCIATED W/ BIRTH DEFECTS
- fetus drinks ~400mL/day beginning at 5 months
what does hydramnios mean? what does oligohydramnios mean?
hydramnios- too much amniotic fluid
oligohydramnios- too little amniotic fluid
what is the difference between dizygotic twins and monozygotic twins
dizygotic: fraternal, 2 separately fertilized eggs, NOT GENETICALLY IDENTICAL
monozygotic: identical, 1 fertilized egg splits into 2 embryos, GENETICALLY IDENTICAL
what are key features about twins
- di/monozygotic
- `60% are born preterm (delivery before 37 weeks)
- high incidence of low birth weight (<2500 g)
- infant mortality rate is 3x that of single birth
what are the 3 causes for birth defect? describe them
1) ENVIRONMENTAL FACTORS (15%)
- drugs, pollutants, infectious diseases, maternal diseases
- ex: TORCHES diseases, thalidomide: sedative that caused limb defects
2) GENETIC FACTORS (30%)
- chromosomal abnormalities
- single mutations
3) INTERAXN OF BOTH GEN. AND ENV.
what is a teratogen
agent/ factor able to induce defects in the embryo
what is the susceptibility to a teratogen based on?
1) FETAL AND MATERNAL GENETICS
- resistance to infection, drug metabolism
2) DEVELOPMENT STAGE AT THE TIME OF EXPOSURE
- ex: cleft palate can be induced at blastocyst stage/ gastrulation/ 5th week/ 7th week, many induced 3-8 weeks
3) DOSE AND DURATION OF EXPOSURE
how does the stage of pregnancy impact pregnancy defects?
NO STAGE OF PREGNANCY IS COMPLETELY SAFE FROM TERATOGEN EFFECTS
- more severe if early on
list a few teratogens
alcohol, androgens, cocaine, lead, tetracycline (causes yellow-gray staining of teeth), tobacco
how can we try to prevent birth defects
- supplementation w/ iodine helps eliminate intellectual disability and bone deformities of cretinism
- women w/ diabetes or phenylketonuria can be under strict dietary regimens
- folate supplementation: lowers risk of neural tube defects
- physicians prescribing meds to pregnant women need to be aware of potential teratogenic effects
what are the 4 prenatal diagnosis methods? what are the 2 categories and assign each method to the correct category
1) ultrasound - screening
2) maternal serum testing- screening
3) amniocentesis- diagnostic
4) chorionic villus sampling- diagnostic
- screening tests and diagnostic tests
describe maternal serum testing
ex: alpha fetoprotein (AFP)
- normally produced by fetal liver, peaks at 14 wks
- normally increases during second trimester then declines
- abnormally low levels / persistent high levels are seen in various abnormalities like neural tube defects
describe amniocentesis
- needle is inserted transabdominally into amniotic cavity and ~20-30mL of fluid withdrawn
- <14 weeks to ensure enough fluid
- can perform karyotyping on sample
describe chorionic villus sampling
- needle is inserted transabdominally or transvaginally into placental mass and ~ 5-30 of villus tissue withdrawn
what occurs in neurulation goes wrong
ANENCEPHALY: failure of neural tube to close in the cranial aspect of the embryo
- LETHAL DEFECT THAT CAUSES THE BRAIN TO NOT FORM
SPINA BIFIDA: failure of neural tube to close in the caudal aspect of the embryo
- SEVERITY OF DEFECT RANGES FROM MILD TO SEVERE
what are the rates of neural tube defects? how can we lower these
- 1:1500 US births
- LOWERED BY FOLIC ACID SUPPLEMENTATION BEGINNING ~3 MONTHS prior to pregn
what are the 3 types of spina bifida
1) SPINA BIFIDA OCCULTA
2) MENINGOCELE
3) MYELOMENINGOCELE
describe SPINA BIFIDA OCCULTA. what are the clinical signs
- open posterior vertebral body
-> usually an incidental finding/ condition found when examining a patient for a separate reason - clinical signs: skin change over the bony defect such as a patch of thick hair, growth, unusual pigment, extremely large dimple or pad of fat
describe MENINGOCELE
- protrusion of the meninges through opening in the vertebral body
- sac of fluid comes thru an opening in the baby’s back, spinal cord is not in this sac
- usually little/ no nerve damage, may cause minor disability
describe MYELOMENINGOCELE
- protrusion of spinal cord through opening in the vertebral body
- spinal cord is damaged
- causes moderate to severe disability: including paralysis and impaired cognitive function
what are neurocristopathies? give a few examples
A GROUP OF DISEASES CAUSED BY THE ABNORMAL GENERATION, MIGRATION, OR DIFFERENTIATION OF NEURAL CREST CELLS
ex: DiGeorge syndrome, ectodermal dysplasia, Pierre Robin SEQUENCE
what is association
a group of malformation that occur together more than would be expected by chance alone
what is a syndrom
a recognizable pattern of signs/ symptoms that run together. typically differs form association in that a molecular cause has been elucidated
what is a sequence
a pattern of deformations and malformations which is a consequence of a single malformation
ex: Step 1 causes 2 & 3 to happen
describe Pierre Robin Sequence
- well recognized presentation characterized by CLEFT PALATE, MANDIBULAR MICROGNATHIA, AND GLOSSOPTOSIS
- can occur as an isolated finding or in association w/ other syndromes
- exact cause is unknown
- sequence of events: UNDERDEVELOPED JAW -> TONGUE DISPLACEMENT -> CLEFT PALATE or high-vaulted U- shaped palate
describe DiGeorge syndrome. what are some clinical features
- caused by 22q11.2 (chromo 22)
-> most common microdeletion syndrome reported in humans
-> may be inherited (autosomal dominant) or spontaneous
-> 1:6000 births - multiple associated clinical features: congenital heart disease, breathing abnormalities, CRANIOFACIAL MALFORMATIONS (COMMONLY CLEFT PALATE), IMMUNODEFICIENCY, developmental delay, behavioral and emotional problems
describe ectodermal dysplasia
- group of inherited disorders defined by the FAILURE TO DEVELOP 2+ ECTODERMAL DERIVED ANATOMIC STRUCTURES
- most well- known ectodermal dysplasia (hypohidrotic) syndrome most commonly shows an X-LINKED RECESSIVE INHERITENCE
-> leads to male predominance of disease - clinical features: HYPOPLASTIC OR ABSENT SALIVARY GLANDS, OLIGODONTIA/ HYPODONTIA/ RARELY ANODONTIA, heat intolerance (reduced eccrine glands), fine sparse hair, fine wrinkling and hyperpig. around eyes, midface hypoplasia, dystrophic/ brittle nails
what is oligodontia? hypodontia? anodontia?
oligo/ hypo: reduced number of teeth
ano: no teeth
what is a defect that originates from the mesoderm
- hemangioma
what is hemangioma? how does it manifest
- abnormally dense collections of capillary blood vessels that form the MOST COMMON TUMORS OF INFANCY (~10% OF ALL BIRTHS)
- often associated w/ craniofacial structures
- tumor may form as a result in defects during vasculature formation
