Embryology Flashcards
How long is the menstrual cycle on average?
28 days
What is the range of normal menstrual cycle length?
21�35 days
What is the purpose of the menstrual cycle?
Prepare for pregnancy
What happens during the menstrual phase (Days 1�5)?
Shedding of the uterine lining
What hormone helps follicles grow in the follicular phase?
FSH
What hormone thickens the uterus in the follicular phase?
Estrogen
What triggers ovulation on Day 14?
LH surge
What is released during ovulation?
Egg
Which phase follows ovulation?
Luteal phase
What hormone is produced by the corpus luteum?
Progesterone
What maintains progesterone levels if fertilization occurs?
hCG
What happens if fertilization does not occur?
Corpus luteum breaks down
What follows the breakdown of the corpus luteum?
Menstruation
What is amenorrhea?
Missed periods
What is dysmenorrhea?
Painful periods
What is menorrhagia?
Heavy bleeding
What is oligomenorrhea?
Irregular cycles
What commonly causes menstrual cycle issues?
Hormonal imbalances
What structure forms the placenta?
Trophoblast
What is the role of the trophoblast?
Implantation into the uterine wall
What does the cytotrophoblast provide?
Structural support
What does the syncytiotrophoblast secrete?
hCG
What is the blastocoel?
Fluid-filled cavity
What is the function of the blastocoel?
Provides space for cellular movement
What structure becomes the embryo?
Inner Cell Mass (ICM)
What does the epiblast give rise to?
Three germ layers
What does the hypoblast contribute to?
Yolk sac & extraembryonic structures
What is the morula?
Solid ball of cells
What marks the transition from morula to blastocyst?
Formation of a hollow structure
When does implantation begin?
Day 5�6
What facilitates implantation?
Trophoblast
Why is blastocyst formation important in IVF?
Higher implantation success
What does the chorion develop from?
Trophoblast & extraembryonic mesoderm
What is the function of the chorion?
Forms placenta for nutrient exchange
What are chorionic villi?
Projections that anchor the embryo
What is the function of the amniotic cavity?
Protects the embryo
What does the yolk sac provide?
Early nutrition
What does the yolk sac contribute to?
Blood cell formation & primitive gut
What forms during gastrulation?
Three germ layers
What does the ectoderm develop into?
Skin, brain, nervous system
What does the mesoderm form?
Muscles, bones, blood, circulatory system
What does the endoderm develop into?
Gut, liver, lungs, internal organs
What does the neural tube become?
Brain & spinal cord
What is the function of the connecting stalk?
Future umbilical cord
What does the connecting stalk transfer?
Oxygen & nutrients
What can errors in neurulation cause?
Neural tube defects
What protects the early embryo?
Zona pellucida
What does the trophoblast develop into?
Placenta
What is the role of the blastocoel cavity?
Cell differentiation
What does the amniotic cavity do?
Protects the embryo
What does the yolk sac support?
Blood cell formation & nutrition
What does the bilaminar disc lead to?
Gastrulation
What do chorionic villi help with?
Nutrient exchange
What forms around the embryo for protection?
Amniotic cavity
What happens at stronger implantation?
Uterine wall attachment
What structure absorbs nutrients from the mother?
Chorionic villi
What role does the blastocoel cavity play?
Provides support
What structure acts as a shock absorber?
Amniotic cavity
What does the yolk sac aid in?
Early blood cell formation
What is the significance of early embryonic stages?
Maternal-fetal connection
What does the neural plate form?
Brain & spinal cord
What is the function of the embryonic cavity?
Supports embryo growth
What is the amniotic membrane?
Protects the embryo
What does the placenta take over from the yolk sac?
Nutrient supply
What happens if the neural tube does not close properly?
Spina bifida
What is the purpose of the zona pellucida?
Regulates implantation
When does the neural tube form?
Week 3�4
What does the epiblast eventually form?
All three germ layers
What supports the embryo before the placenta?
Yolk sac
What key structure forms at implantation?
Blastocyst
What is the first sign of brain & spinal cord formation?
Neural plate
What is the purpose of the menstrual cycle?
To prepare for pregnancy.
How long does the menstrual cycle typically last?
About 28 days.
What is the normal range of the menstrual cycle length?
21�35 days.
What are the four phases of the menstrual cycle?
Menstrual, Follicular, Ovulatory, Luteal.
What happens during the menstrual phase?
Shedding of the uterine lining.
What days does the menstrual phase usually occur?
Days 1�5.
What hormone helps follicles grow during the follicular phase?
FSH (Follicle-Stimulating Hormone).
What is the role of estrogen in the follicular phase?
Thickens the uterine lining.
What days does the follicular phase usually occur?
Days 1�14.
What triggers ovulation?
A surge in LH (Luteinizing Hormone).
On which day does ovulation typically occur?
Day 14.
What happens during ovulation?
The egg is released.
What structure produces progesterone in the luteal phase?
Corpus luteum.
What is the role of progesterone in the luteal phase?
Maintains the uterus for potential pregnancy.
What hormone maintains progesterone levels if fertilization occurs?
hCG (Human Chorionic Gonadotropin).
What happens if fertilization does not occur?
The corpus luteum breaks down, leading to menstruation.
What is amenorrhea?
Absence of periods.
What is dysmenorrhea?
Painful periods.
What is menorrhagia?
Heavy menstrual bleeding.
What is oligomenorrhea?
Irregular menstrual cycles.
What commonly causes menstrual cycle disorders?
Hormonal imbalances.
What does the trophoblast form?
The placenta.
What is the function of the trophoblast?
Implantation into the uterine wall.
What are the two layers of the trophoblast?
Cytotrophoblast and Syncytiotrophoblast.
What does the Syncytiotrophoblast secrete?
hCG.
What is the function of the blastocoel?
Provides space for cellular movement and development.
What does the inner cell mass (ICM) form?
The embryo.
What does the epiblast give rise to?
All three germ layers (ectoderm, mesoderm, endoderm).
What is the function of the hypoblast?
Contributes to the yolk sac and extraembryonic structures.
What marks the transition from a morula to a blastocyst?
Formation of a hollow structure.
What initiates implantation?
The blastocyst attaching to the uterine wall.
Why are blastocyst-stage embryos used in IVF?
Higher implantation success rates.
What does the chorion develop into?
The placenta.
What is the function of the amniotic cavity?
Protects the embryo and maintains temperature.
What is the role of the yolk sac?
Provides early nutrition and blood cell formation.
What is gastrulation?
Formation of three germ layers.
What does the ectoderm develop into?
Skin, brain, nervous system.
What does the mesoderm develop into?
Muscles, bones, blood, circulatory system.
What does the endoderm develop into?
Gut, liver, lungs, and internal organs.
What does the neural tube develop into?
Brain and spinal cord.
What structure transfers oxygen and nutrients from the placenta?
The umbilical cord.
What can errors in neural tube formation cause?
Spina bifida.
What protects the embryo before implantation?
Zona pellucida.
What is the function of the trophoblast?
Develops into the placenta.
What is the function of the blastocoel cavity?
Supports cell differentiation.
What does the amniotic cavity protect?
The developing embryo.
What stage marks the beginning of bilaminar disc formation?
Early blastocyst formation.
What structure helps anchor the embryo to the uterus?
Chorionic villi.
What does the yolk sac provide before placenta development?
Early blood cell formation and nutrition.
What structure helps in implantation and maternal-fetal exchange?
Chorionic villi.
What major event happens in early embryo development stage 5?
Neural plate formation.
What will the neural plate later form?
The brain and spinal cord.
What major structure begins forming in early embryo development stage 6?
The neural tube.
What is the first organ to start functioning?
The heart.
What is the purpose of the amniotic sac?
Protects the embryo with fluid.
What is the earliest form of placental villi?
Primary villi.
What invades primary villi to form secondary villi?
Extraembryonic mesoderm.
When do tertiary villi form?
By day 20�21.
What is the function of tertiary villi?
Gas, nutrient, and waste exchange.
How many arteries and veins are in the umbilical cord?
Two arteries, one vein.
What is a bilobed placenta?
A placenta divided into two lobes.
What is velamentous cord insertion?
Umbilical cord attaches to fetal membranes instead of the placenta.
What is vasa previa?
Fetal blood vessels cross the birth canal.
What side of the placenta is covered by the amnion?
Fetal surface.
What side of the placenta has cotyledons?
Maternal surface.
What twin type shares a placenta but has two amniotic sacs?
Monochorionic diamniotic (MCDA) twins.
What is Twin-Twin Transfusion Syndrome (TTTS)?
Abnormal vascular connections between MCDA twins.
What twin type shares both a placenta and an amniotic sac?
Monochorionic monoamniotic (MCMA) twins.
What is a major risk of MCMA twins?
Cord entanglement.
What structure connects the fetus to the placenta?
The umbilical cord.
What is circumvallate placenta?
What complications can circumvallate placenta cause?
Where is the umbilical cord inserted in marginal cord insertion?
What risks are associated with marginal cord insertion?
What is a bilobed placenta?
What risk is associated with a bilobed placenta?
Are all placental variations harmful?
Why is ultrasound monitoring important in placental variations?
Where does the umbilical cord attach in velamentous cord insertion?
Why is velamentous cord insertion dangerous?
What complications can result from velamentous cord insertion?
What imaging is used to monitor velamentous cord insertion?
Why might a C-section be needed for velamentous cord insertion?
What are conjoined twins?
What are craniophagus twins?
What are cephalophagus twins?
What are omphalophagus twins?
What are pygophagus twins?
What forms during Stage I of facial development?
What does the frontonasal prominence form?
What do the maxillary prominences contribute to?
What does the mandibular prominence form?
What are nasal placodes?
What forms during Stage II of facial development?
What do nasal pits develop into?
How do maxillary prominences change in Stage II?
What happens to the mandibular prominences in Stage II?
What structures surround the nasal pits?
What major fusion occurs in Stage III of facial development?
What continues to merge in Stage III?
What facial structure fully forms in Stage III?
What groove forms between the developing eye and lip?
What structures are more defined in Stage III?
What is the final stage of facial development?
What completes fusion in Stage IV?
What facial feature becomes fully visible in Stage IV?
What happens to the eyes in Stage IV?
What structures finalize in Stage IV?
From which gut section does the stomach develop?
What rotation does the stomach undergo?
What does stomach rotation create?
What does the duodenum develop from?
What happens if duodenal recanalization fails?
What structure gives rise to the liver and biliary system?
What structures arise from the cystic diverticulum?
What forms the pancreas?
What happens to the ventral pancreatic bud?
What artery supplies the foregut?
What artery marks the foregut-midgut transition?
How many somites are visible at 14 somite stage?
What do somites develop into?
What is happening to the neural tube at 14 somite stage?
What do pharyngeal arches contribute to?
What is the visible heart feature at 14 somite stage?
What body shape is characteristic at 14 somite stage?
How many somites are present at 25 somite stage?
What region expands at 25 somite stage?
What new structures appear at 25 somite stage?
How does the heart change at 25 somite stage?
What happens to pharyngeal arches at 25 somite stage?
What is the first stage of palate development?
What does the median palatine process form from?
What begins growing medially in early palatal development?
What occurs in Stage II of palate development?
What separates the oral and nasal cavities?
What does the nasal septum do in palate development?
What does palate fusion prevent?
What structures fully separate after palate fusion?
What is the function of the hard palate?
What is the function of the soft palate?
What forms the primary palate?
The intermaxillary segment.
What does the primary palate give rise to?
The premaxilla and anterior hard palate.
What forms the secondary palate?
The lateral palatine processes.
What does the secondary palate give rise to?
The majority of the hard and soft palate.
What are palatal shelves?
Embryonic structures that elevate and fuse to form the roof of the mouth.
What is the nasopalatine canal?
A persistent communication between the primary and secondary palates.
What results if the palatal shelves fail to fuse?
Cleft palate.
What problems can cleft palate cause?
Issues with speech and feeding.
What is the function of the thyroglossal duct?
Helps form the thyroid gland.
What happens if the thyroglossal duct does not disappear?
A thyroglossal cyst forms.
Where does the thyroid gland originate?
At the base of the tongue.
How does the thyroid gland move during development?
It migrates down to the neck.
Where do thyroglossal cysts typically appear?
As a midline neck swelling.
How do thyroglossal cysts move?
They move when swallowing.
What is the treatment for thyroglossal cysts?
Surgical removal using the Sistrunk procedure.
What embryonic structures contribute to tongue development?
Pharyngeal arches.
What germ layers contribute to tongue development?
Ectoderm and endoderm.
What forms in Stage I of tongue development?
Lingual swellings.
What is the role of lateral lingual swellings?
They form the anterior two-thirds of the tongue.
What is the function of the tuberculum impar?
It appears transiently but does not contribute significantly.
What does the copula arise from?
The second pharyngeal arch.
What happens to the copula?
It is later overgrown.
What does the hypobranchial eminence form?
The posterior one-third of the tongue.
What structures support tongue development?
Surrounding mesenchymal tissues.
What happens in Stage II of tongue development?
The lateral lingual swellings enlarge and merge.
What does the hypobranchial eminence contribute to?
The posterior tongue and epiglottis.
What is the foramen cecum?
A depression marking the site of the thyroglossal duct.
What occurs in Stage III of tongue development?
Maturation and innervation.
What nerve innervates the anterior two-thirds of the tongue for general sensation?
Lingual nerve (branch of CN V3).
What nerve provides taste sensation to the anterior tongue?
Chorda tympani (branch of CN VII).
What nerve innervates the posterior one-third of the tongue?
Glossopharyngeal nerve (CN IX).
Where do tongue muscles originate from?
Occipital somites.
What nerve innervates tongue muscles?
Hypoglossal nerve (CN XII).
What nerve innervates the epiglottis and laryngeal structures?
Vagus nerve (CN X).
What forms the pancreas?
Dorsal and ventral pancreatic buds.
What germ layer does the pancreas originate from?
Endoderm of the foregut.
What does the dorsal pancreatic bud form?
The body and tail of the pancreas.
What does the ventral pancreatic bud form?
The head and uncinate process.
What happens during pancreatic rotation?
The ventral pancreatic bud rotates around the duodenum to fuse with the dorsal bud.
Why is pancreatic rotation important?
It forms a single functional pancreas.
What structure forms from the fusion of pancreatic ducts?
The main pancreatic duct (duct of Wirsung).
What happens if pancreatic rotation fails?
Congenital anomalies like annular pancreas.
What is annular pancreas?
A condition where the pancreas encircles the duodenum and causes obstruction.
What are the two major functions of the pancreas?
Endocrine (hormone secretion) and exocrine (enzyme production).
What is the function of the superior mesenteric artery (SMA)?
It serves as the central axis for gut rotation.
What is the first stage of gut rotation?
Midgut loop formation and physiological herniation.
Why does the midgut herniate?
The abdominal cavity is too small to accommodate rapid growth.
Where does the midgut herniate?
Into the extraembryonic coelom within the umbilical cord.
What happens in the second stage of gut rotation?
A 90-degree counterclockwise rotation.
What happens to the cranial limb during initial rotation?
It moves to the right.
What happens to the caudal limb during initial rotation?
It moves to the left.
What happens during the third stage of gut rotation?
Retraction and an additional 180-degree rotation.
When does the midgut return to the peritoneal cavity?
Week 10-11.
What is the total degree of gut rotation?
270 degrees counterclockwise.
What guides the large intestine into position?
The downward shifting of the cecum.
What happens in the final stage of gut rotation?
Fixation and final arrangement.
What happens to the colon during final positioning?
It frames the small intestine.
Where does the ascending colon end up?
On the right side.
Where does the descending colon end up?
On the left side.
Where does the transverse colon lie?
It crosses the abdomen.
What anchors the intestines?
The mesentery.
What is malrotation?
Incomplete or incorrect gut rotation.
What can malrotation lead to?
Volvulus, causing intestinal obstruction.
What is an omphalocele?
Persistent herniation of the gut outside the abdominal cavity.
What is Meckel�s diverticulum?
A remnant of the vitelline duct.
What complications can Meckel�s diverticulum cause?
Bleeding or infection.
What forms the small intestine?
The cranial limb of the midgut loop.
What forms parts of the large intestine?
The caudal limb of the midgut loop.
What part of the gut elongates the most?
The small intestine.
What provides blood supply to the midgut?
The superior mesenteric artery (SMA).
