Embryology Flashcards

Terms Definitions
urinary bladder
cloaca (in all vert. but mammals serves as chamber for waste of urin. and digest. sys and prod of reprod. sys)
Chromosome Derangements
Half Miscarriages
cerebral hemispheres
olfactory centers
mucosal lining of uterus
muscoskeletal system, circulatory, excretory, gonads, connective tissue, some respitory and digestive (IN BETWEEN ENDO AND ECTO)
Human Chorionic Gonadotropin, tells corpus luteum to produce progesterone and estrogen
Neural tube derivatives
Spinal cord
Motor nerves
Optic vesicles
Posterior pituitary
Early Developmental Stages
a) cleavage
b) implantation
c) gastrulation
d) neurulation
transformation of the single cell layer of blastula into a three-layered structure called
Chorionic villi
attaches baby to mothers uterus
caused by protozoan > Toxoplasma gondi(from cat fecal material)
antibiotic - harms hearing, balance, equalibrium in baby
Differentiation arises from
selective transcription of genomes
What is this process known as?
- when morula develops a fluid-filled cavity called the "blastocoel"
- by the fourth day becomes a hollow sphere of cells called the "blastula"
- blastocyst: mammalian blastula, consist of two cell groups
- thin, tough membrane containing a watery fluid called amniotic fluid
third complete cleavage occurs
72 hours after ferilization
begins when contraction are at timed intervals
contains enzymes in sperm that can digest through layers of cells surrounding the egg
Genital Swelling
Fuse together > scrotumThicker & separates > labia majora
Placenta Formation
Begins with the CHORION, surrounding membrane of AMNION (thin,tough, membrane w/ amniotic fluid (shock absorber)). Chorion extends chorionic villi into uterine wall.
After the third cleavage, the 8-celled embryo reaches where?
The uterus
- the embryo implants in the uterine wall during blastulation, approximately 5-8 days after fertilization
- uterus is prepared for implantation by progesterone, which causes glandular proliferation in the endometrium (mucosal lining of the uterus)
- embryonic cells secrete proteolytic enzymes that digests tissue and implant itself in the endometrium
- eventually maternal & fetal blood exhange materials here, and later it'll be the location of the placenta
First Trimeseter
- major organs develop
- heart begins to beat at approximately 22 days
- eyes, gonads, limbs and liver start to form
- cartilaginous skeleton begins to turn into bone by the 7th week
- most organs formed by the 8th week, embryo is referred to a fetus by then
- at the end of the third month, the fetus is about 9 cm long
identical twins are a result of _____ cleavage
process by which three germ layers are formed, cells begin to specialize
drug to help with morning sickness - harms babies (limb dev)
metanephros (kidney)
last to form and posterior to mesonephros

adult kidney in birds/mammals
Umbilical Cord Formation
The _ALLANTOIS_ develops as an outpocketing of the gut. The blood cells of the allantoic wall enlarge and become umbilical vessels; The Yolk Sac, site of early development of blood vessels, and Allantois, become enveloped by the placenta and form the embryonic cord.
What does it produce?
Progesterone, estrogen, and Human chorionic gonadotropin
What forms next?
An inpocketing forms as cells continue to move toward the invagination, eventually eliminating the blastocoel
What is the opening of the archenteron called?
The blastopore
- embryo is referred to as a fetus after eight weeks of gestation
- receives oxygen directly from its mother through a specialized circulatory system
Foramen ovale/ductus arteriosus
structures found in fetal heart but not in newborn heart
Teratology of Fallot
four parts of heart are messed up
Chorion of egg
outer membrane within shell, used for gas exchange
Fetal Circulation:There are three shunts whose sole purpose is to...
divert blood from the lungs
In deuterostomes such as humans, the blastopore is the site of what?
The future anus
Amniotic Fluid
- acts as a shock absorber of external and localized pressure from uterine contractions during labor
The zygote divides into __ cells in approx ___ hrs; at which point it should be at the ______
8; 72; uterus
What is the trophoblast?
It surrounds the blastocoel and later gives rise to the chorion
At the end of the third month, the fetus is how long?
9cm long
No Gas Exchange in Fetal Lungs
- pulmonary arteries carry partially oxygenated blood to the lungs
- blood that doesn't reach the lungs is deoxygenated as blood unloads its oxygen to the lungs
- deoxygenated blood returns to the left atrium via pulmonary veins and eventually returned to the placenta via umbilical arteries
part of 4 or 5 C missing - sounds like cat meowing
During the ninth month what occurs?
Antibodies are transported by highly selective active transport from the mother to the fetus for protection against foreign matter
how much time does is allowed for the egg to be ferlized after ovlation
12-24 hours after ovulation
What happens when umbilical blood flow stops?
The blood pressure in the inferior vena cava decreases
how exactly does labor occur
1cervix thins and dilates 2amniotic sac raptures 3uterine contractions 4cutting of umbilical chord and placenta
The placenta is permeable to what however?
Viruses, alcohol, and many drugs and toxins
The neural crest cells go to what end?
They migrate laterally to become the PNS, inc the sensory ganglia, autonomic gang, schwann cells, adrenal medulla...
Even though this blood mixes with the partially oxygenated blood that crossed over from the right atrium before being pumped into the system circulation by the left ventricle, the blood delivered via the aorta has what?
An even lower partial pressure oxygen than the blood that was delivered to the lungs
What is the major thing that happens in the second trimester?
The fetus does a tremendous amount of growing
segment of vertebra
Deficient amnionic fluid?
Urachus (median umbilical fold)
Programmed cell death. Non-inflammatory process. Regulated by mitochondria.
What causes Synpolydactyly?
Hoxd13 defect
Species Specific sperm receptor located on the zona pellucida
Opening of the archenteron (gut)
image p. 118 fetal landmark
Fetal erythropoiesis time frames/locations: 28+ wk
Bone marrow
Caused developmental abnormalities in 10k+ in West Germany and Australia: caused limb defects (amelia or meromelia or phocomelia)
Underdevelopment of the zygomatic bones, mandible, ears due to abnormal migration of neural crest to the first arch.
The alimentary canal develops from which germinal tissue?
Most contraceptive pills are either ________________, or an analogue thereof.
What provides ridigity to the embryo?
Ureteric bud - ureter, pelvis, calicesMetanephric blastema - interaction with bud gives rise to glomerulus and renal tubules
Teratogenic effect of:
ACE inhibitors
Fetal Renal damage
umbilical cord
connection between placent and embryo
Posterior 1/3 from
3rd and 4th arches
Three most common tirsomy?
21, 18, 13
It becomes associated with what?
Umbilical vessels
Macrostomia, microstomia
Macro: maxillary and mandibular prominences don't completely fuse laterally
Micro: excessive fusion
when the cell divides into 2
Period of human development around weeks 8 and continue through birth when tissues enlarge and proliferate?
endoderm forms
1 most of respiratory system, epithelium, mucous glands, except nasal passageways2 most of digestive tract,pancreas, liver, epithelium (except mouth and anus), exocrine (except salivary glands) 3reproductive and urinary ducts and gamete stem cell3 thymus, pancreas, thyroid glands, parathyroid gland
Dizygotic Twins
Fraternal Twins - multiple ovulations and multiple fertilizations
Cluster of cells formed after the first 4 days after fertilization that enters uterus
Ectomesenchyme is unique because of its contribution from:
neural crest
Kidney parts
Pronephros - week 4 then degeneratesMesonephros - interim kidney that becomes male genetaliaMetanephros - 5th week
genetial tubercle exposed to estrogen will develop into
glans clitoris
What nerve innervates:
Sensation on anterior 2/3 of tongue
CN V3- Trigeminal
definitive notochord
formed from notochordal cells that proliferate and detach from the endoderm, a solid cord of cells, serves as the basis for the axial skeleton, cranial end forms first
A sequencing mechanism that ensures an orderly series of events which culminate in the development of a highly complex structure, feature, etc.
Primary oocytes begin meiosis I
During fetal life
How long is sperm viable invitro?
2 weeks
When do the first somites appear
Day 20
maternal imprinted genes are important for
embryo development
Are the circulatory systems of the mother and fetus directly connected?
THC can cross the placenta, nervous system disorders, deficits in learning, memory, behavior
Muscles and arteries are derived from which embryologic tissue?
What is the gene responsible for proper organization along the dorsal-ventral axis?
In the primitive mouth, the _________ is the smooth, undifferentiated bulge.
hindgut forms
remaining large intestine through the rectum and part of the anal canal
Fetal period
from 8th week to 38th week
parent or stem cells (diploid cells) which reside in the testes and produce sperm
Cloacal membrane
opens to form the urethra and anus
Define placental abruption
Separation of placenta from the endometrium
what does the prosencephalon become?
the telencephalon (cerebral hemispheres, lateral ventricles) and diencephalon (thalami, 3rd ventricle)
Urogenital folds forms...
A. Labia minor in women
B. Ventral shaft of penis (urethra) in men, responsible for hypospadius
Give the derivatives from cartilages of the 4th and 6th branchial arches
Cartilages of larynx
CN V2 and V3 came from:
branchial arch 1
T or F: Spleen arises from dorsal mesentary but is supplied by artery of foregut
attachment to endometrial epithelium occurs when?
end of week 1
nephrogenic cord
an unsegmented mass of tissue more caudal, from intermediate mesoderm
Wolffian duct develops in SEED?
Seminal vesicles, Epididymis, Ejactulatory duct,
layer which is cellular and helps keep the structure intact
What is the fetal period?
After emybryonic till birth
Does its face appear human at this point?
MI: zygotene (2)
point where pairing of homologous chromosomes occur (2 sister chromatids pair w 2 homologous sister chromatids)
Arnold-Chiari syndrome
Displacement of the medulla and part of the cerebellum into the spinal canal, causing hydrocephalus. May result from abnormal development of the posterior fossa, or hypertrophic growth of the cerebellum. May also be associated with spina bifida.
During fetal development, which germ layer gives rise to the lens of the eye?
The surface ectoderm
What does the septum transversum become in the mature diaphragm?
The central tendon
What are formed by the posterior projection of the globular processes?
Nasal laminae
where are the sclerotome portions of the somites derived
paraxial mesoderm
Fertilization is the uniting of what?
sperm and ovum
what month does the pulmonary alveoli begin to develop?
the 6th month
What structures does the myelencephalon give rise to? what are the cavities?
medulla oblongatacavities: caudal 4th ventricle
Around day ____, the blastocyst implants in the endometrium. Describe the course of events.
Day 6-7.
The embryoblast implants, the trophoblast differentiates into the syncyntiotrophoblast and the cytotrophoblast.
Define Cleavage?
A series of mytotic divisions of the FERTILIZED OVUM which increase the number of blastomneres, thus forming a Morula, (a 16 blastomere formation).
ductus venosus
By which the blood bypasses the fetal liver before convergining with the inferrior vena cava
The bones of the skull, layngeal cartilage, and odontoblasts are derived from:
NEURAL crest (ectoderm)
Teratogenic effect of:
13-cis-retinoic acid
Extremely high risk for birth defects
allantoenteric diverticulum (allantois)
appears around the 16th day of development, a small diverticulum from the posterior wall of the yolk sac, appears when the cloacal membrane appears, in humans is rudimentary but may be involved in abnormalities of bladder development, forms part of the umbilical cord
What tissue do both the urinary and genital systems come from?
intermediate mesoderm
Where does fertilization occur?
The ampulla of the uterine tube
How is this deoxygenated blood returned to the placenta?
Via the umbilical arteries
What is the endometrium?
The mucosal lining of the uterus
How is the hindbrain organized?
The hindbrain (Rhombencephalon) is organized in a segmental fashion as rhombomeres, which are closely associated with the branchial arches. Arch 1 is associated with Rhombomeres 2,3; arch 2 is associated with rhombomeres 4,5; arch 3 and 4 with rhombomeres 6,7,8. Some rhombomeres are associated with specific cranial ganglia.
Thyroglossal duct cyst
Remnants of the thyroglossal duct that protrude from the neck.
Which cranial nerve mediates taste and sensation in the extreme posterior portion of the tongue?
Cranial nerve X
Which branchial arches form the cricoid and arytenoid cartilages and the cartilage of the trachea?
Arches #4 and $5
o Vascular Ring
when regression of the right 6th arch (mainly), dorsal aorta (between 3rd/4th arches), misc. right dorsal aorta, fails; this keeps the foregut in a “cage”
Prediction for the time of birth
LMP+1 year-3 months+1 week
at what point does differentiation occur? What direction?
mid 3rd to 4th weekcephalocaudally(gastrualtion occurs in caudal portiaons while fidderentiation occurs cranially)
Define situs inversus
One or more organs on the opposite site of the body from "normal"
adrenal gland derives from what tissue?
Mesoderm (cortex)neural crest cells (medulla)
Third trimester of gestation (pregnancy)
Antibodies are transported by highly selective ACTIVE transport from mother to fetus for protection against foreign matter.
give the cranial nn responsible for pain
CN V3, IX, X
Growth differentiation factor 9 (GDF9)
member of the TGF-beta family, mediates proliferation of follicular cells
Fetal development landmarks: When are fetuses most susceptible to teratogens
Weeks 3-8 during organ formation
How does the thyroid develop?
The thyroid diverticulum arises from the primitive pharynx.
thyroglossal duct connects tongue to thyroid. Disappears, but may persist as pyramidal lobe of thyroid.
Foramen cecum is a remnant of thyroglossal duct.
Vitelline duct - closure time
VItelline duct normally closes around week VI of intrauterine life
Where is the thalamus?
The thalamus lies at the dorsoventral level appropriate for receiving somatic afferents.
Obstruction of ureter, polycystic kidney
Persistent older arteries or veins that can constrict and block the ureter, urine backs up in the tubules and loops of Henle.
An infant is born with a truncus arteriosus malformation; what germ layer is normally responsible for the aorticopulmonary septum?
Neural crest cells
When does fusion of the medial and lateral nasal processes occur?
The 6th week
what does formation of the vertebrate body plan include
ecto, endo and mesoderm
Tissue that makes up septum transversum
thick plate of mesodermal tissue between thoracic cavity and yolk sac
what does the 3rd branchial pouch develop into?
the inferior parathyroids (dorsal wings)
Tobacco smoking (nicotine or carbon monoxide) will cause what teratogenically?
Preterm labor, placental issues, ADHD, IUGR (intra uterine growth restriction = small slow grow babies)
Purpose of foramen ovale =
shunt O2-rich blood arrived from IVC to left side of heart to be pumped out the AO and to the head
The bulbar and truncal ridges grow to separate the:
Aorta and pulmonary trunk
malformation related to the urachus
patent urachus: the urachus does not fully close off to the bladder and therefore provides a site of leakage from the bladder through the umbilicus.
What does the truncus arteriosus give rise to?
Ascending aorta and pulmonary trunk
For the following teratogen state the effects on the fetus: tobacco
preterm labor, placental problems, ADHD
What does the paramesonpehric duct form?
Müllerian ducts or uterine or fallopian tubes, and the uterus and proximal vagina
How is the bladder formed?
subdivision of the cloaca, via the urorectal septum, which splits the hindgut into the urogenital sinus and the rectum
What are the consequences of tobacco use during pregnancy?
Preterm labor, intrauterine growth restriction, attention-deficit hyperactivity disorder, placental problems
when is the indiffernet stage
first 6 weeks of development (cant tell the sex)
When is surfactant fxn significant?
S levels rise before birth (2 wk before) and most lung fluid resorbed after delivery, yet fatty surfactant layer left behind and is important in first breath to stop water from collapsing alveolar sacs
What disorder causes an organ or organs to be formed outside the body? What development error causes this?
Gastroschisis - caused by anterior wall defect (failure to completely enclose splanchnic/somatic mesoderm)
what is the leading cause of congenital malformations in the US?
FAS = increased incidence of: congenital abnormalities, pre/post natal retardation, microcephaly, holoprosencephaly, facial abnormalities, limb discoloration, and heart/lung fistulas. mechanism may include inhibition of cell migration.
Give the specific epimere derivatives of thoracic myotomes
deep intrinsic back muscles of the thoracic area
A child is born with a heart murmur and high blood pressure. She has a small jaw, low blood calcium, and has had seven upper respiratory infections in her first 3 months with failure to thrive. Which of the cardiac lesions above is most likely?
Coarctation of the aorta
reaction of zona after sperm touches zona
contact results in release of lysosomal enzymes from cortical granules, causes a prevention in more sperm penetration and inactivates species specific receptor on the zona pelucida sites for spermatozoon
What keeps the PDA open?
What closes it?
Open- prosta E, intrauterine asphyxia, neonatal asphyxia
Closed- Indomethacin, ACh, Histamine, and catecholamines
What are some of the embryologic derivatives of the Notochord?
nucleus polpsus of the intervertebral disk
Match the following nerves with their innervations:
trigeminal nerve (V, maxillary and mandibular divisions)
facial nerve (VII)
glossopharyngeal nerve
vagus nerve
accessory nerve
cranial nerve XII (hypoglossal nerve)
trigeminal nerve (V, maxillary and mandibular divisions) first arch, face lining of mouth
facial nerve (VII) second arch
glossopharyngeal nerve third arch, pharynx, and esophagus
vagus nerve fourth and sixth arch, pharynx, esophagus
accessory nerve sternocleidomastoid and trapezius muscles
cranial nerve XII (hypoglossal nerve) muscle of the tongue
Name 3 clinical findings seen with a congenital diaphragmatic hernia.
Hypoplasia of thoracic organs, scaphoid abdomen, and cyanosis
Origin of mesentery that suspends the gut
Caudal end of foregut from dorsal mesentery
what is the mnemonic for fetal erythropoiesis?
Young Liver Synthesizes Blood = yolk sac (3-8 wk), liver (6-30 wk), spleen (9-28 wk), bone marrow (20 wk +).
what is gastrulation? when does it occur?
migration of cells from the epiblast through the primative groove and pit into area underneath (ventral)
what are the functions of the syncytiotrophoblast and cytotrophoblast?
Syncytio- does not divide, grows into the endometrium. produces HCG
cytotrophoblast- divides, Primary chorionic villi.
What happens because oxygenated blood from the umbilical vein mixes with the deoxygenated blood of the venae cavae?
The blood entering the right atrium is only partially oxygenated
What do the urogenital folds become?
fuse --> shaft of penis or remain open --> labia minora
In the embryonic heart, the smooth part of the right atrium is derived from what structure?
The right horn of the sinus venosus
what happens when the endodermal germ layer folds
head, tail and lateral body folding leaves the foregut, midgut and hindgut
what is the role of the Wnt-7 gene?
this is produced at the *apical ectodermal ridge and is necessary for proper organization along the *dorsal-ventral axis.
Does the size of the morula change?
No, it doesn't get bigger, it just gets more "packed"
How does most of this blood bypass the pulmonary circulation?
By way of the foramen ovale
What are the muscles of the tongue derived from?
What muscles do the 1st and 2nd arches form?
somites in the occipital region (the occipital myotomes)

Cells of the first arch make the muscles of mastication, e.g., masseter, mylohyoid and temporalis muscles. Those of the second arch make the muscles of facial expression.
the neural crest cells give rise to what sensory neurons?
All at the spinal level (both somatic and autonomic sensory at the spinal level) they also give rise to cranial autonomic while cranial sensory is derived from n. c. cells and placodes
What happens to the placenta as the embryo grows?
It remains attached to the embryo by the umbilical cord
If a zygote splits within the first 3 days after fertilization, what type of twin pregnancy will result?
The twins will be dichorionic and diamniotic
A 7 year old boy develops a fever of 39 C while playing in his front yard a Dallas summer day. He becomes limp and lethargic, prompting his mother to rush hime to the emergency room. She stats that he never seems to sweat, and that he often feels very war
A defect in gasturlation that produces undergrowth of the ectoderm.
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