Embryology Flashcards
What is derived from the 1st aortic arch?
Maxillary artery
What are the derivatives of the 2nd aortic arch?
Stapedial and hyoid artery
What does the 3rd aortic arch develop into?
Common carotid artery, proximal part of internal carotid artery
What are the derivatives of the 4th aortic arch?
Right: proximal part of the right subclavian
Left: aortic arch
What happens to the 5th aortic arch?
Disappears on both sides
What is derived from the 6th aortic arch?
Right: Proximal part of right pulmonary artery
What does the 1st pharyngeal pouch develop into?
Eustachian tube, middle ear cavity and mastoid antrum
What are the derivatives of the 2nd pharyngeal pouch?
Palatine tonsils
What develops from the dorsal wings of the 3rd pharyngeal pouch?
Inferior parathyroid glands
What develops from the ventral wings of the 3rd pharyngeal pouch?
Thymus
What do the 4th pharyngeal pouch derivatives become?
Superior parathyroid glands
What are the three germ layers in embryology?
Ectoderm, Mesoderm, Endoderm
What structures are derived from surface ectoderm?
- anterior pituitary (Rathke pouch)
- epidermis
- lens of eye
- mammary glands
What is derived from the neural tube? (7)
- CNS neurons
- astrocytes
- oligodendrocytes
- ependymal cells
- posterior pituitary
- retina
- spinal cord
What structures are formed from the neural crest?
- aorticopulmonary septum
- autonomic nerves
- cranial nerves
- enterochromaffin cells
- facial and skull bones
- melanocytes
- odontoblasts
- parafollicular cells of the thyroid
- Schwann cells
- adrenal cortex
- bones (except facial and skull)
- connective tissue
- muscle
- myocardium
- kidneys
- ureters
- gonads
- serous lining of body cavities
- spleen
What does the nucleus pulposus (notochord) contribute to? (6)
- epithelial lining of the GI tract
- liver
- pancreas
- thyroid
- parathyroid
- thymus
What is intraventricular hemorrhage (IVH)?
Haemorrhage that occurs into the ventricular system of the brain
What is a common cause of IVH in premature neonates?
Birth trauma combined with cellular hypoxia
What is the primary treatment for intraventricular hemorrhage?
Supportive therapies
True or False: Jaundice in the first 24 hours is always pathological.
True
List the causes of jaundice in the first 24 hours.
- rhesus haemolytic disease
- ABO haemolytic disease
- hereditary spherocytosis
- glucose-6-phosphodehydrogenase deficiency
What causes physiological jaundice in neonates from 2-14 days?
Combination of more red blood cells, more fragile red blood cells, and less developed liver function
What is indicated if jaundice persists after 14 days?
Prolonged jaundice screen
What tests are included in a prolonged jaundice screen?
- conjugated and unconjugated bilirubin
- direct antiglobulin test (Coombs’ test)
- TFTs
- FBC and blood film
- urine for MC&S and reducing sugars
- U&Es and LFTs
What are common causes of prolonged jaundice?
- biliary atresia
- hypothyroidism
- galactosaemia
- urinary tract infection
- breast milk jaundice
- prematurity
- congenital infections (e.g., CMV, toxoplasmosis)
What is necrotising enterocolitis?
A leading cause of death among premature infants characterized by feeding intolerance, abdominal distension, and bloody stools
What does abdominal x-ray show in necrotising enterocolitis?
- dilated bowel loops
- bowel wall oedema
- pneumatosis intestinalis
- portal venous gas
- pneumoperitoneum
- air outlining the falciform ligament (football sign)
What is neonatal sepsis?
A serious bacterial or viral infection in the blood affecting babies within the first 28 days of life
What are the two categories of neonatal sepsis?
- early-onset sepsis (EOS)
- late-onset sepsis (LOS)
What is the incidence of neonatal sepsis?
1-5 per 1000 live births
What are the most common causes of neonatal sepsis?
- group B streptococcus (GBS)
- Escherichia coli
What are some risk factors for neonatal sepsis?
- Previous GBS infection
- Current GBS colonization
- Premature birth
- Low birth weight
- Maternal chorioamnionitis
What are common clinical presentations of neonatal sepsis?
- Respiratory distress
- Grunting
- Tachypnoea
- Lethargy
- Jaundice
What laboratory test is usually used to diagnose neonatal sepsis?
Blood culture
What is the first-line treatment for suspected neonatal sepsis?
Intravenous benzylpenicillin with gentamicin
What is the embryological origin of the pancreas?
Foregut
What does the ventral pancreatic bud develop into?
- uncinate process
- main pancreatic duct
- pancreatic head
What does the dorsal pancreatic bud develop into?
- body
- tail
- accessory pancreatic duct
- pancreatic head
What is annular pancreas?
Abnormal development resulting in the duodenum being surrounded by a ring of pancreatic tissue
What is pancreatic divisum?
Ventral and dorsal pancreatic ducts fail to fuse together
What is surfactant deficient lung disease (SDLD)?
A condition in premature infants caused by insufficient surfactant production
What is the characteristic chest x-ray finding in SDLD?
‘Ground-glass’ appearance with an indistinct heart border
What is the commonest cause of respiratory distress in the newborn period?
Transient tachypnoea of the newborn (TTN)
What is the management for transient tachypnoea of the newborn?
Observation and supportive care
What are the stages of kidney development in embryology?
- Pronephros
- Mesonephros
- Metanephros
What does the ureteric bud develop into?
- ureter
- renal pelvis
- collecting ducts
- calyces
What does the metanephrogenic blastema develop into?
Glomerulus and renal tubules up to and including the distal convoluted tubule
What does the mesonephric duct develop into in males?
- Sertoli cells
- Seminal vesicles
- Epididymis
- Ejaculatory duct
- Ductus deferens
What does the paramesonephric duct develop into in females?
- fallopian tube
- uterus
- upper third of the vagina
What are the derivatives of the genital tubercle in males?
Glans penis
What do the labioscrotal swellings develop into in females?
Labia majora
What is derived from the truncus arteriosus?
Ascending aorta and pulmonary trunk
The division of the truncus arteriosus is triggered by neural crest cell migration from the pharyngeal arches.
What cardiac structures are derived from the bulbis cordis?
Right ventricle and smooth parts of left ventricle
What do the primitive atria develop into?
Trabeculated parts of the left and right atria
What is the major derivative of the primitive ventricle?
Majority of left ventricle
What does the left horn of the sinus venosus become?
Coronary sinus
What does the right horn of the sinus venosus develop into?
Smooth part of the right atrium
The right common cardinal vein and right anterior cardinal vein form which structure?
Superior vena cava
What is the embryonic origin of the fossa ovalis?
Foramen ovale
What do the umbilical arteries become after birth?
Medial umbilical ligaments
What is the derivative of the umbilical vein?
Ligamentum teres hepatis (inside falciform ligament)
What does the ductus arteriosus develop into?
Ligamentum arteriosum
What is formed from the ductus venosus?
Ligamentum venosum
What does the allantois become?
Urachus
What embryological layer corresponds to the mouth to the proximal half of duodenum?
Foregut
What is the blood supply for the midgut?
Superior mesenteric artery
The hindgut extends from the descending colon to what structure?
Rectum
What structures are derived from the telencephalon?
Cerebral cortex, lateral ventricles, basal ganglia
What does the diencephalon develop into?
Thalamus, hypothalamus, optic nerves, third ventricle
What structures are formed from the mesencephalon?
Midbrain, cerebral aqueduct
What is derived from the metencephalon?
Pons, cerebellum, superior part of fourth ventricle
What does the myelencephalon develop into?
Medulla, inferior part of fourth ventricle
What do the alar plates give rise to?
Sensory neurons
What structures are derived from the basal plates?
Motor neurons
True or False: Absence of the vas deferens may be unilateral or bilateral.
True
What gene mutations are responsible for 40% of cystic fibrosis cases?
CFTR gene mutations
What condition may cause non-CF cases of vas absence?
Unilateral renal agenesis
What is a possible solution for assisted conception in cases of vas absence?
Sperm harvesting
Where are the testicles located until the end of fetal life?
Abdominal cavity
What structure is attached to the inferior aspect of the testis?
Gubernaculum testis
As the fetus grows, what happens to the gubernaculum?
Becomes progressively shorter
By the third month of fetal life, where are the testes located?
Iliac fossae
By the seventh month of fetal life, where do the testes lie?
Level of the deep inguinal ring
What may happen if the processus vaginalis does not close after birth?
Indirect hernias
What may result from part closure of the processus vaginalis?
Development of cysts on the cord
