Embryology Flashcards
How long is the embryonic period?
8 weeks
How long is pregnancy after the last menstrual cycle
38 weeks
What is the layer of cells that appears between the cytotrophoblast and the exocoelomic membrane?
EXTRA-embryonic mesoderm
What is the extra embryonic mesoderm responsible for?
The formation of blood vessels that will connect the embryo to the placenta - chorion/chorionic villi
What is grastrulation
The formation of the trilaminar disc
Cells from the epiblast migrate towards the primative streak, slip beneath it, and form the INTRA-embryonic mesoderm
Epiblast forms ectoderm
Hypoblast forms endoderm
What does the ectoderm give rise to?
CNS PNS Skin Hair Nails Enamel of teet Sensory ep - nose, ear, eye Pituitary, mammary, sweat glands
What are the 3 regions of the mesoderm?
Para-axial
Intermediate
Lateral
What does the para-axial mesoderm give rise to?
Myotomes (muscle tissue)
Dermatomes (subcutaneous tissue)
Sclerotome (bone/cartilage)
What does the intermediate mesoderm give rise to?
They urogenital system: gonad, kidneys and their respective systems
What does the lateral mesoderm give rise to?
2 layers of the lateral mesoderm Somatic (parietal) - future body wall Splanchnic (visceral) -circulatory system -connective system of glands and gut
What does the endoderm give rise to?
Epithelial lining of GI tract, resp sys and urinary bladder
Epithelial lining of tympanic cavity and auditory tube
Parenchyma (functioning tissue) of the thyroid gland, parathyroid gland and auditory tube
What two germ layers are found at the oropharyngeal and cloacal membranes?
Endo and ecto derm - no intervening mesoderm
In the embryo - what are the boundaries of the foregut
Oropharyngeal membrane to liver bud (at 2nd part of the duodenum)
What are the 3 main branches of the coeliac trunk?
Splenic artery
Left gastric artery
Common hepatic
From which two germ layers is the primitive gut formed by?
Endoderm and visceral (splanchnic) mesoderm (lateral plate)
From which germ layer are the hepatocytes derived?
Endoderm
How many pharyngeal arches are there? And what germ layer are they derived from?
5 (1,2,3,4 and 6!) Mesoderm
Stapes, styloid process, and the upper part of the hyoid bone are all skeletal features derived from which pharyngeal arch
2 - hyoid arch
What muscles are derived from the 1st/mandibular pharyngeal arch?
Muscles of mastication Anterior belly of the digastric Mylohyoid Tensor tympani Tensor palatini
What are the bony structures that arise from the 1st pharyngeal arch?
Mandible Maxilla Malleus Incus Middle ear
What are the muscles derived from the 2nd pharyngeal arch?
Muscles of facial expression Buccinator Platysma Stylohyoid Posterior belly of the digatric
What does the 3rd pharyngeal arch give rise to?
Stylopharyngeus
Lower part of the hyoid bone
What does the 4th pharyngeal arch give rise to?
Cricothyroid, intrinsic muscles of the soft palate
Thyroid cartilage, epiglottic cartilage
What does the 6th pharyngeal arch give rise to?
All the intrinsic muscles of the larynx except the cricothyroid
Cricoid cartilage, arytenoid cartilage, corniculate cartilage
How many pharyngeal pouches are there? And from what germ layer are they formed?
4
Endoderm
What does the 1st pharyngeal pouch give rise to?
Middle ear cavity
Auditory/eustachian tube
What does the 2nd pharyngeal pouch give rise to?
Palatine tonsils and tonsillar palatini
What does the 3rd pharyngeal pouch give rise to?
Inferior parathyroid gland
What does the 4th pharyngeal pouch give rise to?
Superior parathyroid gland
How many pharyngeal clefts are there? And what germ layer are they formed from?
4
Ectoderm
What does the 1st pharyngeal cleft give rise to?
External acoustic meatus
What do pharyngeal arches 2,3 and 4 give rise to?
Cervical sinus
Describe the mesentery of the oesophagus
(Lower part) both ventral and dorsal mesentry
Where is the lung bud/respiratory diverticulum found?
Ventral forgut at - End of pharynx, beginning of oesophagus
What divides the oesophagus and lung bud?
Tracheoesophageal septum
How many degrees does the stomach rotate by in the longitudinal axis? Does the original posterior wall move to the right or to the left?
90
Left
What structure develops in the dorsal mesentery (only) of the foregut?
Spleen
What structure develops in both the ventral and dorsal mesentery of the foregut?
Pancreas (ventral and dorsal)
What structure develops in the ventral mesentery (only) of the the foregut?
Liver
Does the lesser omentum form part of the ventral or dorsal mesentery of the foregut? And what structures does it connect?
Ventral
Connect liver to stomach
What is the lienorenal ligament? Does is form part of the ventral or dorsal mesentery of the foregut?
Connects the spleen to the kidney
Dorsal
Where are the lesser and greater omentum continuous with one another?
Epiploic foramen
What structures can be found at the ventral side of the epiploic foramen?
Portal vein
Hepatic artery
Bile duct
Which mesentery is the greater omentum part of? Where does it hang down from?
Dorsal
Greater curvature of the stomach
What connects the midgut to the yolk sac?
Vitelline duct
Which parts of the duodenum are retroperitoneal?
2-4
Which parts of the pancreas are retroperitoneal?
All except tail
What are the 5 stages of the development of the foregut?
Elongation Herniation Rotation Retraction Fixation
Which part of the small intestine is the first to retract and therefore lies more towards the left?
Jejunum
What are the boundaries of the primitive hind gut?
Left 1/3 of the transverse colon to the cloacal membrane
What divides the cloaca in two? What is formed as a result of this division?
Urorectum septum - expands to form perineal body
Urogenital membrane - urogenital sinus
Anal membrane - anal canal
What epithelium is found at the upper 2/3 of the anal canal?
Simple columnar
What epithelium is found at the lower 1/3 of the anal canal?
Stratified squamous non keratinising
What is the name of the line that marks the changing of epithelium between the upper 2/3 and lower 1/3 of the anal canal?
Pectinate line
What does the urogenital sinus give rise to?
Bladder
Urethra
(Female - lower vagina, labia majora, labia minora and clitoris)
From what germ layer is the pancreas derived from?
Endoderm
In what percentage of people does an accessory duct exist in the pancreas?
10%
Name the 3 kidneys that occur during embryological development?
Pronephros
Mesonephros
Metanephros
Which is the permanent kidney?
Metanephros
At what week which does the pronephros arise?
4
What is the pronephros composed of?
7-10 solid cell groups = nephrotomes
The pronephros is non-functioning, true or false?
True
When does the mesonephros arise and disappear?
4th week 8th week (mesonephric ridge/tubules disappear but not the mesonephric (wolffian) duct in males*
At what week does the metanephros occur?
5th week
At what week does the metanephros begin to function?
12 weeks
What two parts form the metanephros?
Metanephric blastema Ureteric bud (*although forms meTanephros the ureteric bud is actually an outgrowth of meSonephric duct)
What does the metanephric blastema give rise to?
The excretory units - nephrons
What does the ureteric bud give rise to?
Collecting system
In what region of the body does the pronephros develop?
Cervical
In what region of the body does the mesonephros develop?
Thoracolumbar
In what region of the body does the metanephros develop?
Pelvic region
Where are the ureters derived from?
Mesonephric duct
From what germ layer is the urogenital system derived from?
Intermediate mesoderm