Embryology Flashcards
Urinary bladder and urethra are embryologically derived from
Primitive urogenital sinus
Persistent yolk sac lead to what condition
Meckels diverticulum
6th pharyngeal arch gives rise to
Intrinsic muscle of larynx
A Bicornuate uterus is due to
Abnormal fusion and reabsorption of the paramesonephric ducts
How many oocytes are available at the time of puberty?
400 000
The vitelline veins give rise to
the hepatic veins
the inferior part of the inferior vena cava
the superior mesenteric vein
the portal vein.
❌ The inferior mesenteric vein is not a derivative of the vitelline vein. 📕
What is the best indicator of gestational age on a dating scan in the first trimester?
Crown rump length
Omphalocoele is an abnormal herniation of
Midgut and yolk sac
Passage of sperm through epidydmis takes how many days?
8-14 days
C cells of thyroid derived from
Pouch of the 4th pharyngeal arch
The cells of which structure form the chorionic villi?
Extraembryonic mesoderm
Equivalent to vagina in males
Prostatic utricle
P.s The prostatic utricle is a small, epithelium-lined diverticulum of the prostatic urethra.
From which structure is the external auditory meatus derived?
Cleft of 1st pharyngeal pouch
Origin of urogenital sinus
Endoderm
Protective layer of graafine follicle
Theca externa
P.s. zona pellucida is the protective layer of oocyte
The renal tubules develop from
metanephrons
Derivatives of 1st Pharyngeal Pouch
-Tubotympanic recess
-Middle Ear
-Auditory tube
-Tubal Tonsil
Derivatives of 2nd Pharyngeal Pouch
Palantine Tonsil
Derivatives of 3rd Pharyngeal Pouch
Dorsal: Inferior Parathyroid Gland
Ventral: Thymus gland
Derivatives of 4th Pharyngeal Pouch
Dorsal: superior parathyroid gland
Ventral: Ultimobranchial body
Derivatives of 5th Pharyngeal Pouch
-Ultimobranchial body (fuses with lateral lobe of thyroid gland)
-Parafollicular cells
embryological origin of perineal body
Tip of Urorectal septum
At what stage of meiosis is the oocyte after ovulation?
Metaphase 2
At what age does meconium first appears in fetal terminal ileum?
10-16 weeks
the origin of renal tubules
Mesonephric blastema
At what gestation does physiological gut herniation occur?
6 weeks return at 10 weeks
From which germ layer does the kidney develop?
Intermediate mesoderm
Cells type present in human corpus luteum?
Granulosa Cells
Cells of pituitary gland secreting growth hormone are located in
Pars Distalis
Intraembryonic coelom forms within which structure?
Lateral Plate mesoderm
Which best describes the process of compaction?
It leads to the formation of the morula after the 16 cell stage
Embryology of bladder trigone
Intermediate Mesoderm
Approximately how many oocytes are present in ovaries at birth?
1 million
How many days after fertilization does the blastocyst form?
5 days
Approximately how many oocytes are present in ovaries at 20 weeks of gestation?
6-7 millions
How many days after fertilization does the morula form?
4 days
In which phase of oocyte development does zona pellucida appears around the ovum
Primary Oocyte
Layer surrounding the zona pellucida
cumulus oophorus
Embryological origin of Anal canal
The upper part of the anal
canal is derived from endoderm
The lower part is derived from ectoderm.
The lining and blood supply of anal canal
The upper two-thirds are lined with
columnar epithelium and derive their blood supply from the superior rectal artery (which is a branch of the inferior mesenteric artery).
The lower third, however, is lined with
stratified squamous epithelium and derives its blood supply from the inferior rectal artery (which is a branch of the Internal pudendal artery).
When does oocytogenisis complete
Birth
When does 1st meiotic division of oocyte is completed
Puberty
When does 2nd meiotic division of oocyte is completed
Fertilization
The forst mitotic division of the zygote is achieved at
30 hours post fertilization
What is gastrulation process
It’s formation of three germ layers
External carotid derived from which aortic arch
1st (debatable 3rd)
When does fertilization occur
24 hour after ovulation
What is blastocyst composed of?
Inner cell mass (embryoblast): later forms embryonic tissue
Outer layer (Trophoblast): later forms extra embryonic tissue i.e placenta
When does implantation occur
Day 6 of fertilization
Phases of Embryogenesis
- Fertilization (in ampulla, 12-24 hrs after ovulation)
- Gastrulation: formation of three germ layer (3rd week of IU life)
- Organogenesis
The neural plate may be seen by which day
Day 18
The neural tube may be seen by which day
Day 22
When cranial and caudal neuropores closes?
What is the result of their closure failure?
The cranial neuropore closes at day 24, failure of its closure leads to anencephaly
The caudal neuropore closes by day 26, failure of its closures leads to spina bifida.
When does primitive heart begins to beat?
from day 21
Week 3
The primitive cloaca is connected to the umbilicus by
the allantois
While urinary bladder grows, the allantois constricts and become thick fibrous cord called
the urachus (represented in adults as the median umbilical ligament)
The anal canal is derived from two embryological tissues
The upper part of the anal canal is derived from endoderm.
While the lower part is derived from ectoderm.
Demarcated by the pectinate line.
Derivatives of 1st Aortic Arch
Maxillary Artery
External Carotid (debatable)
Derivatives of 3rd Aortic Arch
Common carotid
Proximal part of internal carotid
Derivatives of 4th Aortic Arch
• RIGHT- Proximal part of right subclavian artery
• LEFT - Arch of aorta
Derivatives of 5th Aortic Arch
None. It disappears
Derivatives of 6th Aortic Arch
• RIGHT- Distal part of right subclavian artery
• LEFT PROXIMAL - Pulmonary artery
• LEFT DISTAL- Ductus arteriosus
primary oocytes enter the prophase of first meiotic division and remain suspended in this phase until puberty.
This meiotic arrest is produced by secretion of
Oocyte maturation inhibitor OMI
primary oocytes enter the prophase of first meiotic division and remain suspended in this phase until puberty.
This meiotic arrest is produced by secretion of
Oocyte maturation inhibitor OMI
A primary oocyte surrounded by a single layer of follicular cells is called
Primary Follicle
What process changes a spermatogonium into a primary spermatocyte?
Maturation
What process would you expect a secondary spermatocyte to undergo during
spermatogenesis?
2nd meiotic division
In which phase of oocyte development does zona pellucida appear around ovum?
Primary oocyte
The Mesoderm layer spreads out in all directions to lie between the
ectoderm and the endoderm, except in two locations where the
original two germ layers remain in contact:
Cephalic: prochordal plate
Caudal: cloacal plate
The process of the formation of the brain and spinal cord is known as
neurulation
The first pair of somites forms at which day
20 days
by day 17 the mesodermal layer becomes thickest closest to the midline, which is known as the
Paraxial Mesoderm.
The parts further out are known as the intermediate and lateral plate mesoderm.
Somites are what in origin?
Mesodermal
The external genitalia is undifferentiated until what age of intrauterine life?
9 weeks ##
What is the innervation to the 4th part of duodenum?
T10/T11
Ductus venosus is completely obliterated after birth to form what adult structure?
Ligamentum venosum
From what structure does Ligamentum Arteriosum come from?
Ductus arteriosus
Primitive gut is formed by what gestational age
Week 4
Origin of Superior 2/3 of Anal Canal
Endoderm (Hindgut)
Origin of Inferior 1/3 of Anal Canal
Ectoderm (proctodeum)
Epithelium of Superior 2/3 of Anal Canal
Columnar
Epithelium of Inferior 1/3 of Anal Canal
Stratified squamous
Arterial supply of Superior 2/3 of Anal Canal
Superior rectal artery
branch of IMA
Arterial supply of Inferirlor 1/3 of Anal Canal
Inferior rectal Artery
branch of internal pudendal artery
Venous drainage of Superior 2/3 of rectum
Inferior rectal vein
tributary of inferior mesenteric vein
Venous drainage of Superior 2/3 of rectum
Superior rectal vein
tributary of inferior mesenteric vein
Venous drainage of inferior 1/3 of Anal Canal
Inferior rectal vein
tributary of internal pudendal vein
Lymph drainage of Superior 2/3 of Anal Canal
Inferior mesenteric Lymph node
Lymph drainage of Inferior 1/3 of Anal Canal
superficial inguinal lymph nodes
Nerve supply of Superior 2/3 of Anal Canal
Autonomic nervous system
Nerve supply of Inferior 1/3 of Anal Canal
Inferior rectal nerve
Dorsal mesentery is lost in
•Duodenum (Except 1st inch and 4th part where it forms the suspensory ligament of the duodenum “Ligament of Trietz”).
• Ascending colon.
• Descending colon.
Ventral mesentery covers
• Terminal esophagus
• Stomach
• Initial portion of duodenum
The greater omentum is derived from
Dorsal mesogastrium
Vitteline duct connects
Midgut and yolksac
Vittelime duct connects
Midgut and yolksac
Thyroid cartilage and cricothyroid are developed from which pharyngeal arch
4th
Diagnosis of TTTS is staged by using
Quintero System ##
TTTS presented before 26 weeks, must be treated by
Fetoscopic Laser ablation
Delivery of monochorionic twin pregnancy previously complicated by TTS and treated, when?
Between 34+0 and 36+6 weeks ##
Gonadal ridge stay undifferentiated until weeks?
6-7 weeks ##
Uterus is derived from
fused paramesonephric duct
(uterus, cervix, upper half of vagina)
lower half: sinovaginal bulb
Lower half of vagina is derived from
Sinovaginal bulb (swelling in the urogenital sinus)
Intra embryonic coelom forms ?
Pericardial, peritoneal & plural cavity
Somites form regularly at the level of body in the direction of ?
Rostrocaudally
Intra embryonic coelom forms ?
Pericardial, peritoneal & plural cavity
The important human cardiogenic event commencing during week 5 is ?
Heart septation
The lower end of mesonephric duct branches to form ?
Ureteric bud
Intra embryonic coelom is form within?
Lateral plate mesoderm
What is intra embryonic coelom
Lateral plate mesoderm divides into Ventral splanchnic and dorsal somatic mesoderm, the cavity between them is intra embryonic coelom
Central nervous system forms in sequence of?
Neural plate–> neural groove–> neural tube
Lung buds grow into the coelomic cavity in the region of ?
Pericardio peritoneal canals
derivatives of the vitelline vein
Lower inferior vena
Superior mesenteric vein
portal vein
Hepatic vein
Lumen of anal canal recanalizes at?
week 9
How many weeks after conception does the fetal heart and it’s conducting system develop?
3-6 weeks
Trigeminal nerve develop from which pharyngeal arch?
1st
After birth the proximal portion of umbilical arteries will become?
Internal Iliac Artery
From which germ layer does the myenteric plexus of the GI tract developed:
Neural crest of Ectoderm
The posterior fontanelle usually closes by what age?
3 months
What is the layer between the theca cells and the mural granulosa?
Basal lamina
Zona pellucida disappears??
after early blastocyte stage( 4to 5 days)
At what gestational age do fetal breathing movements commence?
12 weeks
What is the embryological origin of Gartner duct ?
Mesonephric duct
How many turns does the midgut go through in its embryological formation?
Three 90° turns counterclockwise
(270)
The cells of which structure form the chorionic villi?
Extraembryonic mesoderm
A 16-year-old girl is diagnosed with transverse vaginal septum. The most likely embryological mechanism responsible for this anomaly is?
Incomplete fusion of sinovaginal bulb with mullerian system
What part of the embryo is the origin of primordial germ cells?
Yolk sac endothelium
The greater omentum is derived from which of the following embryonic structures?
Dorsal mesogastrium
What is the embryonic origin of the trigone of urinary bladder?
Mesonephric duct
The rectum originates from posterior division of which structure?
Primitive cloaca
What happened to decidua basalis in the third trimester
Remain decidua basalis
They ureteric bud is derived from which of the embryonic structures
Mesonephric duct
In the new non invasive prenatal diagnostic test of cell -free fetal DNA what is the source of the cells in maternal blood ?
placental trophoblast
Malleus derived from
1st pharyngeal arch
Stapes is derived from
2nd pharyngeal arch
Inferior parathyroid gland derived from
Third pharyngeal pouch
Eustachian tube is derived from
1st pharyngeal arch
Superior parathyroid gland is derived from
Fourth pharyngeal pouch
Innervation of foregut
T5 - T9
Innervation of midgut
T10 - T11
Innervation of Hindgut
T12-L1
During oogenesis which cell type has the greatest number of chromatides
Primary oocyte
Adrenal gland is derived from
Cortex: intermediate mesoderm
Medulla: Neural crest of ectoderm
Pituitary is derived from
Ectoderm
