Chapter: Upper Limb Anatomy
Topic: Bones of the Hand
Subtopic: Ossification of Carpal Bones
Keyword Definitions
Carpal bones: Eight small bones forming the wrist (carpus).
Ossification: The process of bone formation from cartilage or fibrous tissue.
Capitate: One of the carpal bones, centrally located in the distal carpal row.
Lunate: A crescent-shaped carpal bone in the proximal row, beside the scaphoid.
Pisiform: A small, pea-shaped carpal bone on the ulnar side of the wrist.
Trapezium: A carpal bone at the base of the thumb, distal row.
Clinical: Relating to the observation and treatment of patients.
Radiograph: An image produced on sensitive plate or film by X-rays.
Developmental anatomy: Study of the structural changes of organisms as they grow.
Epiphysis: The end part of a long bone, initially growing separately from the shaft.
NEET PG: National Eligibility cum Entrance Test for Postgraduate medical courses in India.
Lead Question – 2013
First carpal bone to appear is?
a) Trapezium
b) Capitate
c) Pisiform
d) Lunate
Explanation: The **capitate** is the first carpal bone to ossify, usually around the 2nd month after birth. This knowledge is essential in pediatric radiology and helps assess bone age.
Guessed MCQs for NEET PG
1. Which carpal bone is last to ossify?
a) Trapezium
b) Capitate
c) Pisiform
d) Lunate
Explanation: Pisiform is the last carpal bone to ossify, appearing around 9–12 years, important for assessing delayed skeletal development in children.
2. Order of appearance of carpal bones in ossification usually is:
a) Capitate, Hamate, Triquetrum
b) Capitate, Trapezium, Pisiform
c) Lunate, Scaphoid, Hamate
d) Scaphoid, Capitate, Pisiform
Explanation: Capitate appears first, followed by Hamate and then Triquetrum, helping in the assessment of normal growth on X-rays.
3. A 3-year-old child’s wrist X-ray lacks ossified pisiform. This is:
a) Normal finding
b) Suggestive of delayed bone age
c) Indicates rickets
d) Indicates infection
Explanation: Absence of pisiform at 3 years is normal; pisiform ossifies around 9–12 years, so this is not a sign of pathology.
4. Which carpal bone lies most medial in anatomical position?
a) Scaphoid
b) Pisiform
c) Hamate
d) Lunate
Explanation: Pisiform is the most medial carpal bone when the palm faces up, a key landmark in wrist anatomy.
5. The bone forming the floor of the anatomical snuffbox is:
a) Lunate
b) Hamate
c) Trapezium
d) Scaphoid
Explanation: The scaphoid forms the floor of the anatomical snuffbox, relevant to wrist trauma assessment.
6. Which carpal bone articulates with the first metacarpal?
a) Capitate
b) Scaphoid
c) Trapezium
d) Trapezoid
Explanation: Trapezium articulates with the first metacarpal and is crucial for thumb movement, especially in clinical settings like Bennett's fracture.
7. A fall on outstretched hand may most likely fracture:
a) Capitate
b) Scaphoid
c) Pisiform
d) Lunate
Explanation: Scaphoid is most commonly fractured due to its anatomical position and vascular supply, important for recognizing complications like avascular necrosis.
8. In carpal tunnel syndrome, which bone forms the floor of the tunnel?
a) Pisiform
b) Hamate
c) Lunate
d) Capitate
Explanation: The floor of the carpal tunnel is formed by the carpal bones, including the **capitate**, important for understanding clinical symptoms and management.
9. An eight-year-old’s wrist X-ray shows ossified capitate and hamate only. Bone age is approximately:
a) 1 year
b) 3 years
c) 5 years
d) 8 years
Explanation: Capitate and hamate ossify by age 1; absence of other carpal bones suggests bone age is around 1 year, valuable for pediatric growth assessment.
10. The capitate bone is located in which row of the carpus?
a) Proximal row
b) Distal row
c) Both rows
d) Middle row
Explanation: The capitate is centrally located in the distal row of carpal bones, a crucial point in wrist biomechanics.
Keyword Definitions
• Pharyngeal arches – Embryonic structures forming head and neck components.
• Muscles of mastication – Muscles responsible for chewing, derived from 1st arch.
• Facial nerve – 7th cranial nerve, supplies muscles of facial expression.
• Stylopharyngeus – A muscle derived from 3rd pharyngeal arch.
• Recurrent laryngeal nerve – Branch of vagus nerve supplying intrinsic laryngeal muscles.
• Cranial nerves – Nerves emerging from brainstem supplying head, neck, thorax.
• Branchial apparatus – Collective term for arches, pouches, grooves, membranes.
• Palatine tonsil – Lymphoid tissue derived from 2nd pharyngeal pouch.
• Cleft palate – Developmental defect from failed fusion of palatal shelves.
• Treacher Collins syndrome – 1st arch developmental disorder with craniofacial anomalies.
• DiGeorge syndrome – Disorder from 3rd & 4th pouch failure, thymic hypoplasia.
Chapter: Embryology
Topic: Pharyngeal Apparatus
Subtopic: Pharyngeal Arches and Derivatives
Lead Question - 2013
Pharyngeal muscles are derived from which pharyngeal arch?
a) 1st
b) 2nd
c) 3rd
d) 5th
Explanation: The pharyngeal constrictor muscles originate from the 4th and 6th pharyngeal arches, supplied by branches of vagus nerve. Options provided omit the correct arches, but clinically, these muscles develop from the 4th and 6th arches. Correct interpretation emphasizes the vagus nerve contribution and arch differentiation.
Question 2
Which muscle is derived from the 1st pharyngeal arch?
a) Stylopharyngeus
b) Masseter
c) Buccinator
d) Cricothyroid
Explanation: The first pharyngeal arch gives rise to muscles of mastication, including masseter, temporalis, and pterygoids, supplied by mandibular nerve. Stylopharyngeus derives from 3rd arch, buccinator from 2nd, and cricothyroid from 4th. Correct answer: Masseter.
Question 3
The facial nerve supplies muscles originating from which arch?
a) 1st
b) 2nd
c) 3rd
d) 4th
Explanation: The second pharyngeal arch forms muscles of facial expression, stapedius, stylohyoid, and posterior belly of digastric, all supplied by facial nerve (cranial nerve VII). Correct answer: 2nd arch.
Question 4
Stylopharyngeus muscle is derived from which arch?
a) 1st
b) 2nd
c) 3rd
d) 4th
Explanation: Stylopharyngeus originates from the 3rd pharyngeal arch and is supplied by glossopharyngeal nerve (cranial nerve IX). This muscle plays a role in elevating the pharynx during swallowing. Correct answer: 3rd arch.
Question 5
The cricothyroid muscle originates from which pharyngeal arch?
a) 2nd
b) 3rd
c) 4th
d) 6th
Explanation: The cricothyroid muscle arises from the 4th pharyngeal arch and is innervated by the external branch of superior laryngeal nerve (branch of vagus). This distinguishes it from other intrinsic laryngeal muscles, which are from 6th arch. Correct answer: 4th arch.
Question 6
Which pharyngeal pouch gives rise to the palatine tonsil?
a) 1st
b) 2nd
c) 3rd
d) 4th
Explanation: The palatine tonsil develops from the endoderm of the 2nd pharyngeal pouch. It plays a role in immune defense and is part of Waldeyer’s ring. Correct answer: 2nd pouch.
Question 7
DiGeorge syndrome results from abnormal development of which pharyngeal pouches?
a) 1st & 2nd
b) 2nd & 3rd
c) 3rd & 4th
d) 4th only
Explanation: DiGeorge syndrome arises due to failure of 3rd and 4th pharyngeal pouches, leading to thymic hypoplasia, hypocalcemia, and cardiac defects. Correct answer: 3rd & 4th.
Question 8
Which cranial nerve innervates most intrinsic laryngeal muscles from the 6th arch?
a) Glossopharyngeal
b) Vagus - recurrent laryngeal
c) Hypoglossal
d) Accessory
Explanation: Intrinsic laryngeal muscles, except cricothyroid, are derived from 6th pharyngeal arch and supplied by recurrent laryngeal nerve (branch of vagus). Correct answer: Vagus - recurrent laryngeal.
Question 9
Treacher Collins syndrome results from maldevelopment of which arch?
a) 1st
b) 2nd
c) 3rd
d) 4th
Explanation: Treacher Collins syndrome (mandibulofacial dysostosis) results from abnormal neural crest cell migration affecting the 1st arch. It causes craniofacial abnormalities, micrognathia, and cleft palate. Correct answer: 1st arch.
Question 10
Cleft palate is most directly related to abnormal fusion of which structures?
a) Pharyngeal arches
b) Maxillary processes
c) Mandibular processes
d) Hyoid arches
Explanation: Cleft palate results from failure of fusion of the maxillary processes and palatal shelves during embryogenesis, not directly from arch failure. Correct answer: Maxillary processes.
Question 11
Which nerve is associated with the 3rd pharyngeal arch?
a) Trigeminal
b) Facial
c) Glossopharyngeal
d) Vagus
Explanation: The 3rd pharyngeal arch is associated with glossopharyngeal nerve (cranial nerve IX), which supplies stylopharyngeus muscle and contributes to oropharyngeal sensation. Correct answer: Glossopharyngeal.
Keyword Definitions
• Neural tube – Embryonic precursor of brain and spinal cord.
• Neural crest cells – Cells giving rise to peripheral nervous system and craniofacial structures.
• Somites – Mesodermal blocks forming vertebrae and skeletal muscles.
• Myelination – Process of forming myelin sheath around axons for faster conduction.
• Prosencephalon – Forebrain region forming cerebrum and diencephalon.
• Mesencephalon – Midbrain responsible for vision and auditory reflexes.
• Rhombencephalon – Hindbrain forming pons, medulla, and cerebellum.
• Central canal – Cavity of neural tube forming spinal cord canal.
• White matter – Myelinated axonal tracts in CNS.
• Grey matter – Neuronal cell bodies in CNS.
• Spina bifida – Neural tube closure defect affecting vertebral arches.
Chapter: Embryology
Topic: Development of Nervous System
Subtopic: Spinal Cord Development
Lead Question - 2013
Spinal cord develops from?
a) Neural tube
b) Mesencephalon
c) Rhombencephalon
d) Prosencephalon
Explanation: The spinal cord originates from the caudal portion of the neural tube during neurulation. Brain regions like mesencephalon, rhombencephalon, and prosencephalon develop into higher centers, not the spinal cord. Correct answer: Neural tube. Clinical relevance includes spina bifida, a defect from improper neural tube closure.
Question 2
Which cells form the dorsal root ganglia during spinal cord development?
a) Ectodermal placodes
b) Neural crest cells
c) Mesodermal somites
d) Endodermal cells
Explanation: Dorsal root ganglia arise from neural crest cells, which migrate bilaterally from the neural tube. They form sensory neurons, Schwann cells, and sympathetic ganglia. Correct answer: Neural crest cells. Defects may result in peripheral neuropathies or autonomic dysfunctions.
Question 3
The central canal of the spinal cord is derived from which embryonic structure?
a) Notochord
b) Somites
c) Lumen of neural tube
d) Amniotic cavity
Explanation: The central canal forms from the lumen of the neural tube. This canal remains continuous with the ventricular system of the brain. Correct answer: Lumen of neural tube. Its abnormal dilatation can lead to syringomyelia, presenting with dissociated sensory loss.
Question 4
Which glial cells are responsible for myelination in the spinal cord?
a) Schwann cells
b) Astrocytes
c) Oligodendrocytes
d) Microglia
Explanation: In the CNS, including the spinal cord, myelination is carried out by oligodendrocytes. Schwann cells perform the same role in the peripheral nervous system. Correct answer: Oligodendrocytes. Demyelinating disorders like multiple sclerosis highlight the importance of these cells.
Question 5
The motor neurons of the spinal cord develop from which plate of the neural tube?
a) Alar plate
b) Basal plate
c) Roof plate
d) Floor plate
Explanation: Motor neurons of the anterior horn arise from the basal plate of the neural tube. The alar plate gives rise to sensory neurons. Correct answer: Basal plate. Damage leads to motor weakness, as seen in anterior horn cell diseases like poliomyelitis.
Question 6
Which vitamin deficiency is strongly linked with neural tube defects like spina bifida?
a) Vitamin B12
b) Folic acid
c) Vitamin D
d) Vitamin C
Explanation: Maternal folic acid deficiency is a major risk factor for neural tube defects including spina bifida and anencephaly. Correct answer: Folic acid. Supplementation during preconception and early pregnancy prevents these anomalies effectively.
Question 7
In syringomyelia, which part of the spinal cord is commonly affected?
a) Dorsal horn
b) Anterior horn
c) Central canal region
d) White matter tracts
Explanation: Syringomyelia involves cystic dilatation of the central canal of the spinal cord, often at the cervical region. Correct answer: Central canal region. Clinically, it produces cape-like loss of pain and temperature sensation while sparing touch and vibration.
Question 8
Which primary brain vesicle is continuous with the neural tube cranially during development?
a) Mesencephalon
b) Prosencephalon
c) Rhombencephalon
d) All of the above
Explanation: All three primary brain vesicles—prosencephalon, mesencephalon, and rhombencephalon—are continuous cranially with the neural tube, forming higher brain regions. Correct answer: All of the above. This shows the continuity of CNS development from neural tube.
Question 9
Which clinical condition results from failure of the neural tube to close at the cranial end?
a) Spina bifida occulta
b) Syringomyelia
c) Anencephaly
d) Meningomyelocele
Explanation: Failure of the neural tube to close at the cranial neuropore results in anencephaly, a lethal anomaly characterized by absence of cranial vault and brain tissue. Correct answer: Anencephaly.
Question 10
Which part of the neural tube gives rise to sensory neurons of the spinal cord?
a) Basal plate
b) Alar plate
c) Roof plate
d) Floor plate
Explanation: Sensory neurons of the dorsal horn arise from the alar plate of the neural tube. Correct answer: Alar plate. This structural differentiation explains the anatomical segregation of motor and sensory pathways in the spinal cord.
Question 11
A newborn with meningomyelocele most likely has defective development of which structure?
a) Mesodermal somites
b) Neural tube
c) Notochord
d) Amnion
Explanation: Meningomyelocele results from defective closure of the caudal neural tube, leading to herniation of meninges and spinal cord contents. Correct answer: Neural tube. It is associated with neurological deficits and requires early surgical intervention.
Keyword Definitions
• Pronephros – The earliest, rudimentary kidney structure, nonfunctional in humans.
• Mesonephros – The second temporary kidney, functions briefly during embryogenesis.
• Metanephros – The permanent kidney that develops during the 5th week of gestation.
• Ureteric bud – Outgrowth of mesonephric duct forming collecting system of kidney.
• Metanephric blastema – Mesenchymal tissue forming nephrons of the kidney.
• Nephron – Functional unit of kidney, includes glomerulus, tubules, loop of Henle.
• Collecting ducts – Structures draining urine from nephrons to renal pelvis.
• Oligohydramnios – Low amniotic fluid due to defective fetal renal function.
• Potter sequence – Clinical syndrome from renal agenesis causing oligohydramnios and limb deformities.
• Wilm’s tumor – Pediatric renal tumor derived from metanephric blastema.
• Polycystic kidney disease – Inherited disorder with cystic dilation of nephrons and collecting ducts.
Chapter: Embryology
Topic: Development of the Urinary System
Subtopic: Kidney Development
Lead Question - 2013
Collecting part of kidney develops from?
a) Pronephros
b) Mesonephros
c) Metanephros
d) Ureteric bud
Explanation: The collecting system of the kidney, including collecting ducts, calyces, pelvis, and ureter, develops from the ureteric bud. Nephrons arise from the metanephric blastema. Correct answer: Ureteric bud. Clinical correlation: failure of ureteric bud-metanephric interaction causes renal agenesis and Potter sequence.
Question 2
Which embryonic structure gives rise to the nephron?
a) Ureteric bud
b) Metanephric blastema
c) Mesonephric duct
d) Cloaca
Explanation: Nephrons including glomerulus, proximal tubule, loop of Henle, and distal tubule originate from the metanephric blastema. Correct answer: Metanephric blastema. Wilm’s tumor arises from abnormal proliferation of blastemal tissue.
Question 3
Failure of ureteric bud to develop results in?
a) Multicystic dysplastic kidney
b) Renal agenesis
c) Horseshoe kidney
d) Polycystic kidney disease
Explanation: If ureteric bud fails to form, the collecting system and kidney do not develop, leading to renal agenesis. Correct answer: Renal agenesis. Bilateral cases cause Potter sequence with pulmonary hypoplasia.
Question 4
Which structure forms the ureter?
a) Metanephric blastema
b) Ureteric bud
c) Mesonephros
d) Cloacal membrane
Explanation: The ureter, renal pelvis, calyces, and collecting ducts are derived from the ureteric bud. Correct answer: Ureteric bud. Anomalies may cause duplicated ureters or obstructive uropathy.
Question 5
A newborn with Potter sequence most likely had failure of?
a) Mesonephric duct development
b) Ureteric bud induction of metanephric blastema
c) Pronephros degeneration
d) Cloacal partitioning
Explanation: Potter sequence arises due to oligohydramnios from bilateral renal agenesis. This occurs when ureteric bud fails to induce metanephric blastema. Correct answer: Ureteric bud induction failure.
Question 6
Which week does the permanent kidney (metanephros) begin to develop?
a) 3rd
b) 4th
c) 5th
d) 8th
Explanation: Metanephros, the permanent kidney, begins development in the 5th week of gestation and becomes functional by the 10th week. Correct answer: 5th week.
Question 7
Multicystic dysplastic kidney results from abnormal interaction between?
a) Cloaca and allantois
b) Metanephric blastema and ureteric bud
c) Mesonephric duct and pronephros
d) Nephron and somites
Explanation: Multicystic dysplastic kidney occurs due to defective interaction between ureteric bud and metanephric blastema. Correct answer: Metanephric blastema and ureteric bud.
Question 8
Which structure contributes to formation of efferent arteriole of glomerulus?
a) Metanephric blastema
b) Ureteric bud
c) Mesonephric duct
d) Dorsal aorta branches
Explanation: Renal vasculature including afferent and efferent arterioles develops from branches of dorsal aorta. Correct answer: Dorsal aorta branches. This ensures blood supply to developing glomeruli.
Question 9
In horseshoe kidney, fusion occurs at which pole?
a) Upper pole
b) Lower pole
c) Mid pole
d) Both poles
Explanation: In horseshoe kidney, the lower poles fuse, preventing ascent due to inferior mesenteric artery obstruction. Correct answer: Lower pole. It may predispose to obstruction, stones, or infection.
Question 10
Polycystic kidney disease is associated with defective development of?
a) Collecting ducts
b) Proximal tubules
c) Loop of Henle
d) Renal pelvis
Explanation: Polycystic kidney disease involves abnormal development of nephrons and collecting ducts, leading to multiple fluid-filled cysts. Correct answer: Collecting ducts. It can cause hypertension and renal failure.
Question 11
A child presents with a duplicated ureter. This anomaly is due to?
a) Early splitting of ureteric bud
b) Failure of mesonephros regression
c) Persistence of pronephros
d) Cloacal membrane defect
Explanation: Duplicated ureter results from premature bifurcation of the ureteric bud before penetrating the metanephric blastema. Correct answer: Early splitting of ureteric bud. Clinically, it may predispose to reflux or obstruction.
Keyword Definitions
• Somites – Paired blocks of paraxial mesoderm forming vertebrae, ribs, skeletal muscle, dermis.
• Paraxial mesoderm – Mesodermal tissue flanking the neural tube forming somites.
• Cervical somites – First somites to appear, giving rise to occipital and cervical structures.
• Thoracic somites – Form thoracic vertebrae, ribs, and associated muscles.
• Lumbar somites – Form lumbar vertebrae and trunk musculature.
• Sacral somites – Contribute to sacrum and pelvic structures.
• Dermatome – Somite portion forming dermis.
• Myotome – Somite portion forming skeletal muscles.
• Sclerotome – Somite portion forming vertebrae and ribs.
• Somitogenesis – Sequential formation of somites in cranio-caudal direction.
• Neural crest – Migrating cells associated with somite development.
Chapter: Embryology
Topic: Development of Musculoskeletal System
Subtopic: Somite Formation
Lead Question
Which level do somites initially form?
a) Thoracic level
b) Cervical level
c) Lumbar level
d) Sacral level
Explanation: Somites appear first in the cervical region around day 20 of development, and then proceed sequentially in a cranio-caudal direction. They differentiate into dermatome, myotome, and sclerotome. Correct answer: Cervical level. Clinical correlation: abnormal somitogenesis can cause congenital vertebral anomalies like scoliosis.
Question 2
At which day of embryonic development do the first somites appear?
a) Day 10
b) Day 15
c) Day 20
d) Day 25
Explanation: The first somites appear around day 20 of development in the cervical region. This marks the beginning of segmentation in the embryo. Correct answer: Day 20.
Question 3
How many pairs of somites are typically formed in humans?
a) 31
b) 33
c) 42-44
d) 28
Explanation: Humans develop about 42–44 pairs of somites, though some regress, leaving 31 pairs of spinal nerves. Correct answer: 42-44 pairs. Somite count is a reliable indicator of embryonic age.
Question 4
Which portion of a somite forms the vertebrae and ribs?
a) Dermatome
b) Myotome
c) Sclerotome
d) Neural crest
Explanation: The sclerotome differentiates into vertebrae and ribs. Myotome forms skeletal muscles, while dermatome forms dermis of skin. Correct answer: Sclerotome.
Question 5
Which somites contribute to the formation of limb muscles?
a) Cervical and thoracic
b) Lumbar and sacral
c) Thoracic and lumbar
d) Cervical and lumbar
Explanation: Limb muscles develop from myotomes of cervical and lumbar somites that migrate into limb buds. Correct answer: Cervical and lumbar. Defective migration may cause limb musculature anomalies.
Question 6
Dermatome cells derived from somites form which structure?
a) Epidermis
b) Dermis of skin
c) Cartilage
d) Skeletal muscle
Explanation: The dermatome portion of somites differentiates into dermis of the skin. Correct answer: Dermis of skin. This explains segmental dermatomal distribution of cutaneous nerves.
Question 7
The occipital somites contribute to which skeletal structures?
a) Mandible
b) Skull base and tongue muscles
c) Scapula
d) Sternum
Explanation: Occipital somites contribute to skull base bones and intrinsic tongue muscles. Correct answer: Skull base and tongue muscles. Their development is clinically significant in congenital craniovertebral anomalies.
Question 8
Failure of somite segmentation results in?
a) Scoliosis
b) Klippel-Feil syndrome
c) Spina bifida
d) Sirenomelia
Explanation: Failure of segmentation of cervical somites results in fused cervical vertebrae, seen in Klippel-Feil syndrome. Correct answer: Klippel-Feil syndrome. It presents with short neck, low hairline, and limited mobility.
Question 9
Which signaling pathway is crucial for somite formation?
a) Notch signaling
b) Hedgehog signaling
c) Wnt signaling
d) VEGF signaling
Explanation: Notch signaling plays a critical role in regulating segmentation and somitogenesis. Correct answer: Notch signaling. Its disruption can lead to congenital vertebral malformations.
Question 10
In congenital scoliosis, abnormal development of which somite derivative is implicated?
a) Dermatome
b) Myotome
c) Sclerotome
d) Neural crest
Explanation: Congenital scoliosis occurs due to defective vertebral formation from sclerotome. Correct answer: Sclerotome. Hemivertebrae or block vertebrae may cause lateral spinal curvature.
Question 11
Which clinical condition is associated with defective migration of hypoglossal nerve-related somites?
a) Micrognathia
b) Ankyloglossia
c) Tongue muscular hypoplasia
d) Cleft palate
Explanation: Defective migration of occipital somites, which form tongue muscles, can cause tongue muscular hypoplasia. Correct answer: Tongue muscular hypoplasia. It may impair swallowing and speech in infants.
Keyword Definitions
• Inferior vena cava (IVC) – Main vein returning deoxygenated blood from lower body to heart.
• Cardinal veins – Primitive venous system of embryo including anterior, posterior, common cardinal veins.
• Subcardinal veins – Embryonic veins contributing to renal, gonadal, and IVC formation.
• Supracardinal veins – Embryonic veins forming azygos, hemiazygos, and part of IVC.
• Sacrocardinal veins – Veins draining lower limbs, contribute to distal IVC.
• Anastomosis – Connection between vessels ensuring proper venous return.
• Venous anomalies – Variations due to abnormal regression or persistence of embryonic veins.
• Double IVC – Persistence of bilateral supracardinal or subcardinal channels resulting in two IVCs.
• Left IVC – Occurs when left supracardinal persists instead of regressing.
• Retroaortic renal vein – Venous anomaly from altered regression of subcardinal/supracardinal veins.
• Clinical relevance – Important for imaging, renal surgery, and catheter placement.
Chapter: Embryology
Topic: Development of Venous System
Subtopic: Inferior Vena Cava and Variants
Lead Question - 2013
Double inferior vena cava is formed due to?
a) Persistence of sacrocardinal veins
b) Persistence of supracardinal veins
c) Persistence of subcardinal veins
d) Persistence of both supracardinal and subcardinal veins
Explanation: A double inferior vena cava results when both right and left supracardinal veins persist instead of regression. This anomaly is clinically significant in radiology and surgical planning. Correct answer: Persistence of supracardinal veins. It may mimic lymphadenopathy or retroperitoneal mass on imaging.
Question 2
Which embryonic vein forms the hepatic segment of the inferior vena cava?
a) Right vitelline vein
b) Left vitelline vein
c) Subcardinal vein
d) Supracardinal vein
Explanation: The hepatic segment of the IVC develops from the right vitelline vein, which contributes to liver sinusoids and portal vein. Correct answer: Right vitelline vein. Defects may present as interrupted IVC with azygos continuation.
Question 3
The renal segment of the IVC is formed by?
a) Subcardinal vein
b) Supracardinal vein
c) Sacrocardinal vein
d) Vitelline vein
Explanation: The renal segment of IVC is formed from subcardinal veins and their anastomosis with supracardinal veins. Correct answer: Subcardinal vein. Developmental errors can cause retroaortic left renal vein anomaly.
Question 4
Which embryonic structure gives rise to the azygos and hemiazygos veins?
a) Subcardinal veins
b) Supracardinal veins
c) Vitelline veins
d) Sacrocardinal veins
Explanation: The azygos and hemiazygos veins develop from supracardinal veins. Correct answer: Supracardinal veins. These provide alternate pathways for venous return in IVC obstruction.
Question 5
A retroaortic left renal vein develops due to abnormal persistence of?
a) Dorsal arch of subcardinal–supracardinal anastomosis
b) Ventral arch of subcardinal–supracardinal anastomosis
c) Sacrocardinal venous loop
d) Left vitelline venous loop
Explanation: Retroaortic left renal vein arises from persistence of dorsal limb of subcardinal–supracardinal anastomosis. Correct answer: Dorsal arch of subcardinal–supracardinal anastomosis. It has clinical implications during renal transplantation and surgery.
Question 6
Which part of the IVC is derived from the sacrocardinal veins?
a) Suprarenal segment
b) Renal segment
c) Hepatic segment
d) Postrenal segment
Explanation: Sacrocardinal veins contribute to the postrenal segment of the IVC, responsible for draining lower limbs. Correct answer: Postrenal segment. Persistence of abnormal channels here can cause double IVC.
Question 7
A left-sided inferior vena cava develops from persistence of?
a) Left supracardinal vein
b) Left subcardinal vein
c) Left sacrocardinal vein
d) Left vitelline vein
Explanation: Persistence of left supracardinal vein causes a left-sided IVC. Correct answer: Left supracardinal vein. It may complicate retroperitoneal surgery and is important in radiological diagnosis.
Question 8
Which clinical condition is associated with azygos continuation of IVC?
a) Persistence of left vitelline vein
b) Absence of hepatic segment of IVC
c) Absence of sacrocardinal segment
d) Failure of renal anastomosis
Explanation: Azygos continuation occurs when hepatic segment of IVC is absent, blood drains through azygos vein. Correct answer: Absence of hepatic segment of IVC. This anomaly is often detected incidentally on imaging.
Question 9
Which embryonic vein mainly contributes to gonadal veins?
a) Subcardinal vein
b) Supracardinal vein
c) Vitelline vein
d) Sacrocardinal vein
Explanation: Gonadal veins develop from subcardinal veins. Correct answer: Subcardinal vein. Left gonadal vein drains into left renal vein, while right drains directly into IVC, explaining asymmetry in varicocele prevalence.
Question 10
Which anomaly results from persistence of both supracardinal veins?
a) Double IVC
b) Left renal vein anomaly
c) Retroaortic renal vein
d) Interrupted IVC
Explanation: Double IVC arises when both right and left supracardinal veins persist. Correct answer: Double IVC. Clinically, it is important in IVC filter placement and radiology to avoid misdiagnosis as a pathological mass.
Question 11
Interrupted IVC with azygos continuation is most associated with which syndrome?
a) Down syndrome
b) Turner syndrome
c) Polysplenia syndrome
d) Patau syndrome
Explanation: Interrupted IVC with azygos continuation is a classic feature of polysplenia syndrome, a heterotaxy disorder. Correct answer: Polysplenia syndrome. Awareness is crucial during cardiac and abdominal imaging to prevent misinterpretation.
Keyword Definitions
• Heart tube – Primitive structure that gives rise to the adult heart.
• Cardiac jelly – Gelatinous connective tissue surrounding the early heart tube, aiding septation and valve formation.
• Mesocardium – Mesodermal tissue suspending the developing heart tube.
• Myocardium – Muscular layer of the heart derived from splanchnic mesoderm.
• Endocardium – Inner endothelial lining of the heart tube.
• Pericardium – Fibroserous sac enclosing the heart.
• Endocardial cushions – Thickenings in cardiac jelly that contribute to septa and valves.
• Septation – Partitioning process forming atria, ventricles, and outflow tracts.
• Splanchnic mesoderm – Embryonic layer giving rise to myocardium and epicardium.
• Conotruncal ridges – Structures contributing to aorticopulmonary septum.
• Congenital heart disease – Malformations due to abnormal heart tube development.
Chapter: Embryology
Topic: Cardiovascular Development
Subtopic: Development of Heart Tube
Lead Question – 2013
Jelly formed around the heart tube during early development, contributes to the formation of:
a) Pericardium
b) Mesocardium
c) Myocardium
d) Endocardium
Explanation: The jelly around the early heart tube is known as cardiac jelly. It plays a crucial role in septation and valve formation. It contributes to the development of the endocardial cushions, which later form septa and valves. Correct answer: Endocardium. Clinical relevance: abnormal cushions cause atrioventricular septal defects.
Guessed Questions for NEET PG
1) The myocardium of the heart develops from:
a) Neural crest cells
b) Splanchnic mesoderm
c) Cardiac jelly
d) Endocardial cushions
Explanation: The myocardium develops from the splanchnic mesoderm surrounding the heart tube. Neural crest cells contribute to outflow tract formation. Correct answer: Splanchnic mesoderm. Clinically, failure of proper myocardial compaction leads to non-compaction cardiomyopathy.
2) Endocardial cushions are primarily derived from:
a) Cardiac jelly
b) Neural crest
c) Paraxial mesoderm
d) Somites
Explanation: Endocardial cushions arise from cardiac jelly with contribution from neural crest cells. They form atrial and ventricular septa, as well as atrioventricular valves. Correct answer: Cardiac jelly. Maldevelopment causes atrioventricular septal defects.
3) The epicardium of the heart develops from:
a) Neural crest
b) Splanchnic mesoderm (proepicardial organ)
c) Cardiac jelly
d) Endocardium
Explanation: The epicardium arises from mesothelial cells of the proepicardial organ derived from splanchnic mesoderm. Correct answer: Splanchnic mesoderm. Epicardial defects can impair coronary vessel development.
4) Which embryological structure gives rise to the sinoatrial node?
a) Sinus venosus
b) Endocardial cushion
c) Cardiac jelly
d) Conotruncal ridge
Explanation: The sinoatrial node develops from the sinus venosus and atrial wall junction. Correct answer: Sinus venosus. Clinical importance: abnormalities cause arrhythmias and conduction defects.
5) Cardiac looping establishes which relation of ventricles?
a) Left ventricle anterior, right ventricle posterior
b) Right ventricle anterior, left ventricle posterior
c) Both anterior
d) Both posterior
Explanation: During cardiac looping, the primitive ventricle moves left and inferior, right ventricle moves anteriorly. Correct answer: Right ventricle anterior, left ventricle posterior. Abnormal looping causes congenital malpositions.
6) Failure of endocardial cushion fusion results in:
a) Tetralogy of Fallot
b) Transposition of great arteries
c) Atrioventricular septal defect
d) Patent ductus arteriosus
Explanation: Endocardial cushions are essential for atrioventricular septation. Their failure causes AV septal defect. Correct answer: Atrioventricular septal defect. Seen in Down syndrome.
7) Neural crest cells contribute to formation of:
a) Interventricular septum muscular part
b) Aorticopulmonary septum
c) Endocardial cushions
d) Cardiac jelly
Explanation: Neural crest cells form the aorticopulmonary septum, which separates aorta and pulmonary trunk. Correct answer: Aorticopulmonary septum. Defects cause persistent truncus arteriosus and conotruncal anomalies.
8) Which embryological structure forms the coronary arteries?
a) Endocardial cushions
b) Proepicardial organ
c) Cardiac jelly
d) Sinus venosus
Explanation: Coronary vessels develop from mesenchymal cells of the proepicardial organ. Correct answer: Proepicardial organ. Defects cause coronary artery anomalies leading to ischemia.
9) Which part of the heart develops last embryologically?
a) Left atrium
b) Right atrium
c) Ventricles
d) Outflow tracts
Explanation: Outflow tracts are the last structures to complete development with neural crest contribution. Correct answer: Outflow tracts. Defects cause conotruncal malformations like transposition of great arteries.
10) Abnormality of cardiac jelly primarily affects formation of:
a) Pericardium
b) Myocardium
c) Valves and septa
d) Coronary arteries
Explanation: Cardiac jelly is key in valve and septum development. Defects in its formation or migration result in septal defects. Correct answer: Valves and septa.
Keyword Definitions
• Retina – Light-sensitive tissue lining the back of the eye, derived from neuroectoderm.
• Optic vesicle – Outgrowth from the diencephalon that develops into the retina.
• Neuroectoderm – Embryonic tissue forming nervous system structures, including retina.
• Diencephalon – Part of the forebrain giving rise to retina, thalamus, and hypothalamus.
• Mesencephalon – Midbrain, involved in visual and auditory pathways.
• Telencephalon – Forebrain region developing into cerebral hemispheres.
• Optic cup – Double-layered structure from optic vesicle forming neural and pigmented retina.
• Lens placode – Surface ectoderm thickening forming the lens.
• Choroid fissure – Temporary groove in optic cup for hyaloid artery entry.
• Coloboma – Defect due to failure of choroid fissure closure.
• Retinoblastoma – Malignant retinal tumor from embryonic retinal cells.
Chapter: Embryology
Topic: Nervous System Development
Subtopic: Development of Eye
Lead Question – 2013
The retina is an outgrowth of the?
a) Mesencephalon
b) Diencephalon
c) Telencephalon
d) Pons
Explanation: The retina originates from the optic vesicle, which is a direct outgrowth of the diencephalon. This neuroectodermal origin distinguishes it from mesodermal or surface ectodermal derivatives. Correct answer: Diencephalon. Clinical relevance: optic nerve hypoplasia results from defective diencephalic outgrowth.
Guessed Questions for NEET PG
1) The optic nerve develops from:
a) Mesoderm
b) Diencephalon
c) Optic stalk
d) Surface ectoderm
Explanation: The optic nerve develops from the optic stalk, which connects the optic vesicle to the brain. Correct answer: Optic stalk. Clinically, optic nerve coloboma occurs if the choroid fissure fails to close.
2) The lens of the eye develops from:
a) Surface ectoderm
b) Neural crest
c) Diencephalon
d) Mesoderm
Explanation: The lens is derived from surface ectoderm as the lens placode, induced by the optic vesicle. Correct answer: Surface ectoderm. Clinical note: congenital cataract results from abnormal lens development.
3) Pigmented layer of retina develops from:
a) Surface ectoderm
b) Inner layer of optic cup
c) Outer layer of optic cup
d) Neural crest cells
Explanation: The outer layer of the optic cup forms the retinal pigmented epithelium. Correct answer: Outer layer of optic cup. Defects may cause albinism due to melanin pathway abnormalities.
4) Failure of choroid fissure closure leads to:
a) Retinoblastoma
b) Coloboma
c) Cataract
d) Aniridia
Explanation: Incomplete closure of the choroid fissure results in a coloboma, seen as a keyhole defect in the iris or retina. Correct answer: Coloboma.
5) Corneal endothelium and stroma are derived from:
a) Neural crest cells
b) Surface ectoderm
c) Diencephalon
d) Mesoderm only
Explanation: Neural crest cells migrate to form corneal stroma and endothelium. Correct answer: Neural crest cells. Clinical note: abnormal migration causes congenital corneal opacities.
6) Which of the following is a neuroectodermal derivative?
a) Lens
b) Retina
c) Corneal epithelium
d) Conjunctiva
Explanation: The retina arises from neuroectoderm, specifically the diencephalic optic vesicle. Correct answer: Retina. Clinical relevance: retinoblastoma arises from retinal neuroectodermal cells.
7) The ciliary body muscles are derived from:
a) Neuroectoderm
b) Neural crest
c) Surface ectoderm
d) Mesoderm
Explanation: Ciliary body muscles are unusual because they are neuroectodermal in origin, unlike most smooth muscles. Correct answer: Neuroectoderm. Clinical note: dysfunction leads to impaired accommodation.
8) Aniridia results from mutation in:
a) PAX6 gene
b) PAX2 gene
c) SHH gene
d) RET gene
Explanation: PAX6 is the master gene for eye development. Its mutation causes aniridia, characterized by absence of iris. Correct answer: PAX6 gene.
9) Persistent hyaloid artery may cause:
a) Cataract
b) Coloboma
c) Aniridia
d) Retinitis pigmentosa
Explanation: If the embryonic hyaloid artery fails to regress, it leads to persistent fetal vasculature causing cataract. Correct answer: Cataract.
10) Which part of the brain gives rise to the pineal gland and retina both?
a) Mesencephalon
b) Diencephalon
c) Telencephalon
d) Myelencephalon
Explanation: Both pineal gland and retina originate from the diencephalon, showing its key role in sensory organ development. Correct answer: Diencephalon.
Keyword Definitions
• Aortic arches – Embryonic vascular structures connecting the truncus arteriosus with the dorsal aortae.
• Arch of aorta – Major systemic artery arch formed mainly from the left 4th aortic arch.
• Dorsal aorta – Paired embryonic vessels that later fuse to form the descending aorta.
• Truncus arteriosus – Primitive outflow tract of the heart, later forming the aorta and pulmonary artery.
• Right subclavian artery – Derived from right 4th arch and part of dorsal aorta.
• Left common carotid – Derived from the left 3rd arch.
• Pulmonary arteries – Derived from the 6th aortic arch.
• Patent ductus arteriosus – Persistence of the distal left 6th arch, connecting aorta and pulmonary artery.
• Double aortic arch – Vascular ring anomaly due to persistence of both 4th arches.
• Coarctation of aorta – Congenital narrowing of the aortic lumen, often at ductus arteriosus site.
• Interrupted aortic arch – Rare defect due to abnormal regression of 4th aortic arch.
Chapter: Embryology
Topic: Cardiovascular System Development
Subtopic: Development of Aortic Arches
Lead Question – 2013
Arch of Aorta develops from which aortic arch artery?
a) Right Pt
b) Right 3rd
c) Left 4th
d) Left 3rd
Explanation: The arch of the aorta is derived primarily from the left 4th aortic arch. This embryonic vessel contributes to the definitive systemic circulation. Correct answer: Left 4th arch. Clinically, abnormal development may result in anomalies like double aortic arch or interrupted aortic arch, causing airway/esophageal compression.
Guessed Questions for NEET PG
1) The right subclavian artery is derived from:
a) Right 3rd arch
b) Right 4th arch
c) Left 4th arch
d) Right 6th arch
Explanation: The right subclavian artery forms from the right 4th aortic arch and a part of the right dorsal aorta. Correct answer: Right 4th arch. Clinical note: abnormal regression may cause aberrant right subclavian artery, compressing the esophagus (dysphagia lusoria).
2) The common carotid artery is derived from:
a) 1st arch
b) 2nd arch
c) 3rd arch
d) 4th arch
Explanation: Both right and left common carotid arteries develop from the 3rd aortic arches. Correct answer: 3rd arch. Clinical note: anomalies can alter carotid bifurcation, relevant in vascular surgery.
3) Pulmonary arteries develop from:
a) 4th arch
b) 6th arch
c) 2nd arch
d) Dorsal aorta only
Explanation: The proximal part of the 6th aortic arches form the proximal pulmonary arteries. Correct answer: 6th arch. Clinical: persistence of distal left 6th arch forms patent ductus arteriosus (PDA).
4) Which arch gives rise to maxillary artery?
a) 1st arch
b) 2nd arch
c) 3rd arch
d) 4th arch
Explanation: The 1st aortic arch largely disappears, but remnants contribute to the maxillary artery. Correct answer: 1st arch. Clinical relevance: early vascular anomalies in the head and neck may involve this origin.
5) Stapedial artery arises from which arch?
a) 1st arch
b) 2nd arch
c) 3rd arch
d) 4th arch
Explanation: The stapedial artery develops from the 2nd arch artery, though it regresses later. Correct answer: 2nd arch. Persistent stapedial artery may cause conductive hearing loss.
6) The ductus arteriosus develops from:
a) Right 4th arch
b) Left 6th arch
c) Right 6th arch
d) Left 3rd arch
Explanation: The ductus arteriosus, an essential fetal shunt, originates from the distal part of the left 6th arch. Correct answer: Left 6th arch. Clinical: persistence after birth leads to PDA, causing left-to-right shunt.
7) Double aortic arch is due to persistence of:
a) Right 6th arch
b) Both 4th arches
c) Left 3rd arch
d) Right 2nd arch
Explanation: Failure of regression of the right 4th arch alongside the left 4th arch causes double aortic arch. Correct answer: Both 4th arches. Clinically, this creates a vascular ring compressing trachea and esophagus.
8) The external carotid artery develops from:
a) Ventral part of 3rd arch
b) Ventral part of 1st arch
c) Dorsal part of 2nd arch
d) Dorsal aorta
Explanation: The external carotid artery arises as a branch from the ventral part of the 3rd arch. Correct answer: Ventral part of 3rd arch. Clinical note: variations important in carotid endarterectomy.
9) Interrupted aortic arch type B is due to regression of:
a) Left 3rd arch
b) Left 4th arch
c) Left 6th arch
d) Right 4th arch
Explanation: In type B interrupted aortic arch, the defect is due to abnormal regression of the left 4th arch. Correct answer: Left 4th arch. Clinical: presents with severe neonatal heart failure.
10) The vertebral arteries are derived from:
a) Intersegmental arteries
b) 3rd arch
c) 4th arch
d) 6th arch
Explanation: The vertebral arteries are formed by longitudinal anastomosis of cervical intersegmental arteries, not aortic arches. Correct answer: Intersegmental arteries. Clinical: anomalies may contribute to vertebrobasilar insufficiency syndromes.
Keyword Definitions
• Pharyngeal arches – Embryonic structures forming muscles, arteries, cartilage, and nerves of head and neck.
• First arch – Gives muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, tensor palati.
• Second arch – Muscles of facial expression, stapedius, stylohyoid, posterior belly of digastric.
• Third arch – Gives rise to stylopharyngeus muscle, supplied by glossopharyngeal nerve (CN IX).
• Fourth arch – Cricothyroid, pharyngeal constrictors, soft palate muscles (except tensor palati).
• Sixth arch – Intrinsic laryngeal muscles except cricothyroid.
• Stylopharyngeus – Elevates pharynx during swallowing, only muscle of third arch.
• Cranial nerves – Each arch linked to a nerve: V, VII, IX, X.
• Arch anomalies – Defective arch development causes syndromes (DiGeorge, Treacher Collins).
• Clinical importance – Lesions of CN IX affect gag reflex and swallowing.
Chapter: Embryology
Topic: Pharyngeal Apparatus
Subtopic: Muscular Derivatives of Pharyngeal Arches
Lead Question – 2013
Muscle of third arch?
a) Tensor tympani
b) Stylopharyngeus
c) Cricothyroid
d) None
Explanation: The third arch forms only the stylopharyngeus muscle, innervated by CN IX (glossopharyngeal). Correct answer: Stylopharyngeus. It plays a role in elevating pharynx during swallowing. Lesions impair gag reflex. Tensor tympani (1st arch), cricothyroid (4th arch) are incorrect.
Guessed Questions for NEET PG
1) Muscles of mastication are derived from:
a) First arch
b) Second arch
c) Third arch
d) Fourth arch
Explanation: The first arch produces muscles of mastication along with tensor palati, tensor tympani, mylohyoid. Correct answer: First arch. Clinical: V3 nerve injury causes jaw deviation and chewing weakness.
2) Which arch forms muscles of facial expression?
a) First
b) Second
c) Third
d) Fourth
Explanation: Second arch forms muscles of facial expression and stapedius, supplied by facial nerve (CN VII). Correct answer: Second arch. Clinical: Bell’s palsy causes facial droop due to CN VII dysfunction.
3) Cricothyroid is derived from:
a) Second arch
b) Third arch
c) Fourth arch
d) Sixth arch
Explanation: Cricothyroid belongs to fourth arch derivatives, innervated by external laryngeal branch of vagus. Correct answer: Fourth arch. Injury leads to inability to produce high-pitched sounds.
4) All intrinsic laryngeal muscles except cricothyroid develop from:
a) Fourth arch
b) Sixth arch
c) First arch
d) Second arch
Explanation: The sixth arch gives rise to intrinsic laryngeal muscles (except cricothyroid), supplied by recurrent laryngeal nerve. Correct answer: Sixth arch. Injury results in hoarseness or stridor.
5) Mylohyoid belongs to which arch?
a) First
b) Second
c) Third
d) Fourth
Explanation: The mylohyoid muscle is a derivative of the first arch, innervated by mandibular nerve (V3). Correct answer: First arch. Weakness causes impaired swallowing and tongue movements.
6) A patient with glossopharyngeal nerve lesion will show paralysis of:
a) Stylopharyngeus
b) Cricothyroid
c) Buccinator
d) Mylohyoid
Explanation: Glossopharyngeal nerve supplies stylopharyngeus (third arch). Correct answer: Stylopharyngeus. Clinical finding: absent gag reflex and swallowing difficulty.
7) Stapedius arises from which arch?
a) First
b) Second
c) Third
d) Fourth
Explanation: The stapedius is a derivative of the second arch, supplied by facial nerve. Correct answer: Second arch. Injury causes hyperacusis due to loss of dampening of sound vibrations.
8) Which muscle is supplied by mandibular nerve but not part of mastication?
a) Tensor tympani
b) Masseter
c) Temporalis
d) Medial pterygoid
Explanation: Tensor tympani, a first arch derivative, is innervated by mandibular nerve but not a muscle of mastication. Correct answer: Tensor tympani. Dysfunction causes abnormal sound sensitivity.
9) Pharyngeal constrictors are derived from:
a) First arch
b) Third arch
c) Fourth arch
d) Sixth arch
Explanation: The pharyngeal constrictors come from the fourth arch, supplied by pharyngeal branches of vagus. Correct answer: Fourth arch. Dysfunction produces dysphagia and aspiration risk.
10) Neonatal stridor due to recurrent laryngeal nerve injury involves muscles from:
a) Fourth arch
b) Sixth arch
c) Second arch
d) Third arch
Explanation: Sixth arch gives intrinsic laryngeal muscles except cricothyroid. Correct answer: Sixth arch. Recurrent laryngeal palsy causes hoarseness and airway compromise post-thyroid surgery.