Chapter: Central Nervous System; Topic: Brainstem Anatomy; Subtopic: Floor of the Fourth Ventricle
Keyword Definitions:
Fourth Ventricle: A cavity in the hindbrain located between the pons and medulla, continuous with the central canal of the spinal cord.
Vagal Triangle: A triangular area on the floor of the fourth ventricle overlying the dorsal nucleus of the vagus nerve.
Infundibulum: A stalk connecting the hypothalamus to the pituitary gland.
Mammillary Body: Rounded structures involved in memory, located in the hypothalamus.
Tuber Cinereum: A gray matter area in the hypothalamus between the optic chiasma and mammillary bodies.
Lead Question (2014):
Floor of 4th ventricle has?
a) Infundibulum
b) Vagal triangle
c) Mammillary body
d) Tuber cinereum
Explanation: The floor of the fourth ventricle, also called the rhomboid fossa, contains several nuclei and tracts of cranial nerves. The vagal triangle represents the underlying dorsal nucleus of the vagus nerve, making it a prominent feature of the ventricular floor. The correct answer is (b) Vagal triangle. Other options belong to the hypothalamic region. (100 words)
1. The facial colliculus is formed by?
a) Fibers of facial nerve winding around abducens nucleus
b) Hypoglossal nucleus
c) Vagal nucleus
d) Vestibular nucleus
Explanation: The facial colliculus is an elevation in the floor of the fourth ventricle formed by the facial nerve fibers looping around the abducens nucleus. It represents an important landmark in the pontine tegmentum. Hence, the correct answer is (a) Fibers of facial nerve winding around abducens nucleus. (100 words)
2. Which structure forms the roof of the fourth ventricle?
a) Superior medullary velum
b) Inferior olivary nucleus
c) Medial lemniscus
d) Hypothalamus
Explanation: The roof of the fourth ventricle is formed by the superior and inferior medullary vela, and the cerebellum. The superior medullary velum forms the upper part of the roof, connecting the superior cerebellar peduncles. Therefore, the correct answer is (a) Superior medullary velum. (100 words)
3. The floor of the fourth ventricle corresponds to which structure of the brainstem?
a) Pons and medulla
b) Midbrain
c) Hypothalamus
d) Cerebellum
Explanation: The floor of the fourth ventricle is formed by the dorsal surfaces of the pons and medulla oblongata. It has several important nuclei and tracts that form visible elevations. The midbrain and hypothalamus lie above this region. Thus, the correct answer is (a) Pons and medulla. (100 words)
4. The hypoglossal triangle overlies which cranial nerve nucleus?
a) Hypoglossal nerve nucleus
b) Glossopharyngeal nucleus
c) Abducens nucleus
d) Facial motor nucleus
Explanation: The hypoglossal triangle is a small triangular area on the floor of the fourth ventricle overlying the hypoglossal nerve nucleus. It is located medially to the vagal triangle. Therefore, the correct answer is (a) Hypoglossal nerve nucleus. (100 words)
5. The area postrema is associated with which physiological function?
a) Vomiting reflex
b) Vision
c) Hearing
d) Taste perception
Explanation: The area postrema is located in the medulla near the obex and lacks a blood-brain barrier. It detects toxins in the blood and triggers vomiting. Hence, it is known as the vomiting center of the brain. Therefore, the correct answer is (a) Vomiting reflex. (100 words)
6. (Clinical) A patient presents with deviation of the tongue to one side and dysarthria. Lesion is likely at?
a) Hypoglossal triangle region
b) Facial colliculus
c) Vagal triangle
d) Trapezoid body
Explanation: The hypoglossal nerve controls tongue movement. Lesions in the hypoglossal triangle region of the floor of the fourth ventricle damage its nucleus, leading to tongue deviation toward the affected side and speech difficulty. Hence, the correct answer is (a) Hypoglossal triangle region. (100 words)
7. (Clinical) A lesion involving the vagal triangle may cause?
a) Dysphonia and dysphagia
b) Loss of facial sensation
c) Diplopia
d) Ataxia
Explanation: The vagal triangle overlies the dorsal nucleus of the vagus nerve, which supplies motor fibers to the laryngeal and pharyngeal muscles. Lesions here produce dysphonia and dysphagia. Therefore, the correct answer is (a) Dysphonia and dysphagia. (100 words)
8. (Clinical) A tumor compressing the floor of the fourth ventricle may cause?
a) Vomiting and ataxia
b) Blindness
c) Deafness
d) Memory loss
Explanation: Tumors of the fourth ventricle (e.g., medulloblastomas) compress the area postrema and cerebellar connections, causing vomiting and ataxia due to obstruction of CSF flow and vestibular imbalance. Hence, the correct answer is (a) Vomiting and ataxia. (100 words)
9. (Clinical) Lesion near the facial colliculus results in?
a) Facial paralysis and medial strabismus
b) Hearing loss
c) Taste loss
d) Ptosis
Explanation: The facial colliculus contains fibers of the facial nerve looping around the abducens nucleus. Lesion here causes ipsilateral facial paralysis and inability to abduct the eye (medial strabismus). The correct answer is (a) Facial paralysis and medial strabismus. (100 words)
10. (Clinical) A lesion at the obex region leads to?
a) Interference with vomiting reflex
b) Loss of smell
c) Visual disturbances
d) Hemiparesis
Explanation: The obex is the caudal tip of the fourth ventricle near the area postrema, which regulates vomiting. A lesion here impairs toxin detection and vomiting reflex. Hence, the correct answer is (a) Interference with vomiting reflex. (100 words)
Chapter: Head and Neck Anatomy; Topic: Cranial Cavity and Meninges; Subtopic: Middle Meningeal Artery and Cranial Foramina
Keyword Definitions:
Middle Meningeal Artery: A branch of the maxillary artery that supplies the dura mater and the calvaria.
Foramen Spinosum: A small opening in the sphenoid bone through which the middle meningeal artery enters the cranial cavity.
Foramen Ovale: Transmits the mandibular nerve (V3) and accessory meningeal artery.
Foramen Rotundum: Transmits the maxillary nerve (V2).
Foramen Lacerum: A fibrocartilaginous structure at the skull base, not transmitting major arteries.
Lead Question (2014):
Middle meningeal artery passes through?
a) Foramen ovale
b) Foramen lacerum
c) Foramen rotundum
d) Foramen spinosum
Explanation: The middle meningeal artery, a branch of the maxillary artery, enters the cranial cavity through the foramen spinosum. It supplies the dura mater and calvarial bones. This artery runs between the dura and the skull and is clinically important because fractures of the temporal bone can rupture it, causing epidural hematoma. Hence, the correct answer is (d) Foramen spinosum. (100 words)
1. Which nerve passes through the foramen ovale?
a) Maxillary nerve
b) Mandibular nerve
c) Ophthalmic nerve
d) Abducent nerve
Explanation: The foramen ovale transmits the mandibular nerve (V3), the accessory meningeal artery, and sometimes the lesser petrosal nerve. It is an oval opening in the sphenoid bone connecting the middle cranial fossa with the infratemporal fossa. Therefore, the correct answer is (b) Mandibular nerve. (100 words)
2. The middle meningeal artery is a branch of?
a) External carotid artery
b) Internal carotid artery
c) Vertebral artery
d) Superficial temporal artery
Explanation: The middle meningeal artery arises from the first part of the maxillary artery, which is a branch of the external carotid artery. It enters the cranial cavity through the foramen spinosum and divides into anterior and posterior branches, supplying the meninges and skull. Hence, the answer is (a) External carotid artery. (100 words)
3. Which bone is most commonly fractured leading to middle meningeal artery rupture?
a) Temporal bone
b) Parietal bone
c) Occipital bone
d) Frontal bone
Explanation: The temporal bone, particularly the pterion region, is the thinnest part of the skull and lies directly over the middle meningeal artery. Fractures here can rupture the artery, causing an epidural hematoma. Thus, the correct answer is (a) Temporal bone. (100 words)
4. The anterior branch of the middle meningeal artery lies beneath which region?
a) Pterion
b) Lambda
c) Bregma
d) Asterion
Explanation: The anterior branch of the middle meningeal artery runs deep to the pterion — a junction where the frontal, parietal, temporal, and sphenoid bones meet. Because of this anatomical relationship, trauma at the pterion can rupture the artery. Therefore, the correct answer is (a) Pterion. (100 words)
5. The foramen spinosum is located in which bone?
a) Temporal bone
b) Sphenoid bone
c) Parietal bone
d) Frontal bone
Explanation: The foramen spinosum is a small circular opening in the greater wing of the sphenoid bone. It transmits the middle meningeal artery, vein, and meningeal branch of the mandibular nerve. Thus, the correct answer is (b) Sphenoid bone. (100 words)
6. (Clinical) A patient with a temporal bone fracture develops rapid loss of consciousness and a biconvex hematoma on CT. The likely cause is?
a) Rupture of middle meningeal artery
b) Rupture of superior sagittal sinus
c) Rupture of vertebral artery
d) Rupture of cortical vein
Explanation: A temporal bone fracture can tear the middle meningeal artery, leading to accumulation of blood between the skull and dura — an epidural hematoma. This condition shows a biconvex (lens-shaped) appearance on CT and requires emergency evacuation. The correct answer is (a) Rupture of middle meningeal artery. (100 words)
7. (Clinical) Which clinical sign suggests an epidural hematoma due to middle meningeal artery rupture?
a) Lucid interval
b) Continuous unconsciousness
c) Subdural bleed
d) Bilateral mydriasis
Explanation: In epidural hematoma, patients often experience a “lucid interval,” a temporary recovery period after head trauma followed by rapid deterioration as the hematoma enlarges. This is a hallmark of middle meningeal artery rupture. Hence, the correct answer is (a) Lucid interval. (100 words)
8. (Clinical) During a craniotomy, the surgeon identifies bleeding near the foramen spinosum. The source is most likely?
a) Middle meningeal artery
b) Inferior alveolar artery
c) Ophthalmic artery
d) Internal carotid artery
Explanation: The middle meningeal artery enters the skull via the foramen spinosum and lies close to the inner surface of the skull. Bleeding near this area during surgery typically indicates injury to this artery. Thus, the correct answer is (a) Middle meningeal artery. (100 words)
9. (Clinical) A patient develops right-sided weakness and anisocoria after head injury. Which artery is most likely ruptured?
a) Middle meningeal artery
b) Anterior cerebral artery
c) Vertebral artery
d) Posterior inferior cerebellar artery
Explanation: In a middle meningeal artery rupture, an epidural hematoma may compress the brain, causing uncal herniation. The herniated temporal lobe compresses the oculomotor nerve, leading to anisocoria, and affects the contralateral corticospinal tract, causing hemiparesis. Hence, the answer is (a) Middle meningeal artery. (100 words)
10. (Clinical) In epidural hematoma, blood collects between?
a) Dura mater and skull
b) Dura mater and arachnoid mater
c) Arachnoid and pia mater
d) Brain tissue and pia mater
Explanation: An epidural hematoma results from arterial bleeding between the dura mater and the inner surface of the skull. The dura is stripped from the bone by pressure of the expanding hematoma, leading to a biconvex shape on imaging. Hence, the correct answer is (a) Dura mater and skull. (100 words)
Chapter: Head and Neck Anatomy; Topic: Oral Cavity and Salivary Glands; Subtopic: Submandibular Gland and Duct Relations
Keyword Definitions:
Submandibular Duct: Also known as Wharton’s duct, it opens at the sublingual papilla beside the lingual frenulum and carries saliva from the submandibular gland.
Lingual Nerve: A branch of the mandibular nerve (V3) that supplies general sensation to the anterior two-thirds of the tongue.
Hypoglossal Nerve: The twelfth cranial nerve, motor to intrinsic and extrinsic muscles of the tongue.
Recurrent Laryngeal Nerve: A branch of the vagus nerve that supplies intrinsic laryngeal muscles.
Lead Question (2014):
Nerve which loops around submandibular duct?
a) Mandibular nerve
b) Lingual nerve
c) Hypoglossal nerve
d) Recurrent laryngeal nerve
Explanation: The lingual nerve passes deep to the submandibular duct after looping beneath it. This unique anatomical relationship allows the lingual nerve to carry both general sensation and special taste fibers (via chorda tympani) to the anterior two-thirds of the tongue. Hence, the correct answer is (b) Lingual nerve. Injury during submandibular surgery may cause sensory loss in the tongue. (100 words)
1. The lingual nerve is a branch of which cranial nerve?
a) Facial nerve
b) Glossopharyngeal nerve
c) Trigeminal nerve
d) Hypoglossal nerve
Explanation: The lingual nerve is a branch of the mandibular division of the trigeminal nerve (CN V3). It carries general sensory fibers from the anterior two-thirds of the tongue and is joined by the chorda tympani, which adds taste and parasympathetic fibers. Therefore, the correct answer is (c) Trigeminal nerve. (100 words)
2. Which nerve carries taste fibers from the anterior two-thirds of the tongue?
a) Lingual nerve
b) Glossopharyngeal nerve
c) Chorda tympani
d) Vagus nerve
Explanation: The chorda tympani nerve, a branch of the facial nerve (CN VII), carries taste fibers from the anterior two-thirds of the tongue. It joins the lingual nerve to reach its destination. Thus, though taste fibers travel within the lingual nerve, they originate from the facial nerve. Hence, the correct answer is (c) Chorda tympani. (100 words)
3. The submandibular duct opens into the oral cavity at?
a) Base of tongue
b) Floor of mouth beside lingual frenulum
c) Near tonsillar fossa
d) Soft palate
Explanation: The submandibular duct (Wharton’s duct) opens into the floor of the mouth beside the lingual frenulum at the sublingual papilla. This location allows easy saliva drainage into the oral cavity. The correct answer is (b) Floor of mouth beside lingual frenulum. (100 words)
4. Which nerve is closely related to the submandibular ganglion?
a) Hypoglossal nerve
b) Lingual nerve
c) Facial nerve
d) Glossopharyngeal nerve
Explanation: The submandibular ganglion is suspended from the lingual nerve by small filaments. Preganglionic fibers from the chorda tympani synapse here, and postganglionic fibers supply the submandibular and sublingual glands. Thus, the correct answer is (b) Lingual nerve. (100 words)
5. (Clinical) During surgery of submandibular duct stones, which nerve is at greatest risk of injury?
a) Lingual nerve
b) Hypoglossal nerve
c) Mylohyoid nerve
d) Glossopharyngeal nerve
Explanation: The lingual nerve loops beneath the submandibular duct and is in close relation to it. Surgical removal of ductal calculi (sialolithiasis) may damage the lingual nerve, resulting in loss of general sensation and taste from the anterior two-thirds of the tongue. Thus, the correct answer is (a) Lingual nerve. (100 words)
6. (Clinical) A patient presents with loss of taste and general sensation in the anterior two-thirds of the tongue. The lesion likely involves?
a) Lingual nerve distal to chorda tympani junction
b) Hypoglossal nerve
c) Glossopharyngeal nerve
d) Recurrent laryngeal nerve
Explanation: The lingual nerve distal to the chorda tympani junction carries both general sensory and taste fibers. A lesion at this point causes combined sensory and taste loss in the anterior tongue, while proximal injury affects only general sensation. Therefore, the correct answer is (a) Lingual nerve distal to chorda tympani junction. (100 words)
7. (Clinical) Parasympathetic fibers to the submandibular gland originate from?
a) Facial nerve via chorda tympani
b) Glossopharyngeal nerve via lesser petrosal
c) Vagus nerve
d) Hypoglossal nerve
Explanation: The facial nerve gives parasympathetic fibers through the chorda tympani, which joins the lingual nerve and synapses in the submandibular ganglion. Postganglionic fibers innervate the submandibular and sublingual glands, controlling salivary secretion. Hence, the correct answer is (a) Facial nerve via chorda tympani. (100 words)
8. (Clinical) Hypoglossal nerve supplies which muscles of the tongue?
a) Palatoglossus
b) Styloglossus
c) Hyoglossus
d) Both b and c
Explanation: The hypoglossal nerve (CN XII) supplies all intrinsic and extrinsic muscles of the tongue except palatoglossus (which is supplied by the vagus nerve). Therefore, the correct answer is (d) Both b and c. (100 words)
9. (Clinical) A patient with right hypoglossal nerve palsy shows?
a) Tongue deviation to the left
b) Tongue deviation to the right
c) Loss of taste
d) Paralysis of soft palate
Explanation: In hypoglossal nerve palsy, the tongue deviates toward the side of the lesion due to paralysis of the genioglossus muscle. Over time, atrophy and fasciculations appear on the affected side. Hence, the correct answer is (b) Tongue deviation to the right. (100 words)
10. (Clinical) Which condition results from inflammation of the submandibular gland?
a) Sialolithiasis
b) Parotitis
c) Glossitis
d) Pharyngitis
Explanation: Sialolithiasis is the formation of calculi (stones) within the salivary ducts, commonly the submandibular duct due to its long upward course. It leads to pain and swelling during meals. Chronic obstruction can cause infection (sialadenitis). The correct answer is (a) Sialolithiasis. (100 words)
Chapter: Neuroanatomy; Topic: Brainstem; Subtopic: Developmental Origin of Medulla Oblongata
Keyword Definitions:
Medulla oblongata: The lower part of the brainstem responsible for autonomic functions like respiration, heart rate, and blood pressure.
Myelencephalon: The posterior part of the embryonic hindbrain that gives rise to the medulla oblongata.
Brainstem: The central trunk of the brain connecting the cerebrum with the spinal cord.
Embryonic vesicles: Developmental brain regions — prosencephalon, mesencephalon, and rhombencephalon — that differentiate into various brain structures.
Lead Question - 2014
Medulla oblongata is derived from ?
a) Telencephalon
b) Diencephalon
c) Mesencephalon
d) Myelencephalon
Explanation: The medulla oblongata develops from the myelencephalon, the caudal part of the rhombencephalon (hindbrain). During embryonic development, the rhombencephalon divides into the metencephalon (forming the pons and cerebellum) and the myelencephalon (forming the medulla). The medulla controls vital autonomic functions like heart rate, respiration, and reflexes such as coughing and vomiting.
1) The pons is derived from ?
a) Metencephalon
b) Myelencephalon
c) Diencephalon
d) Mesencephalon
Explanation: The pons originates from the metencephalon, the upper division of the rhombencephalon. It serves as a communication bridge between the cerebrum and cerebellum. Functionally, it assists in respiratory control and facial sensation. During embryogenesis, neural tube segmentation determines these structures' distinct developmental origins.
2) The midbrain originates from which embryonic vesicle?
a) Prosencephalon
b) Mesencephalon
c) Diencephalon
d) Rhombencephalon
Explanation: The midbrain arises from the mesencephalon. It contains important structures such as the superior and inferior colliculi, red nucleus, and substantia nigra. These regions regulate visual and auditory reflexes and coordinate motor control, linking sensory input to motor output through cranial nerve nuclei and tracts.
3) Clinical-type: A patient with lesions in the medulla shows respiratory arrest. Which embryonic structure was primarily affected?
a) Telencephalon
b) Myelencephalon
c) Mesencephalon
d) Metencephalon
Explanation: The myelencephalon forms the medulla oblongata, housing the respiratory and cardiac centers. Lesions here result in life-threatening respiratory and cardiovascular dysfunction. The medulla integrates autonomic signals and transmits them via cranial nerves IX, X, XI, and XII to maintain homeostasis.
4) The cerebellum develops from ?
a) Metencephalon
b) Myelencephalon
c) Mesencephalon
d) Diencephalon
Explanation: The cerebellum arises from the metencephalon during neural tube development. It plays a crucial role in balance, posture, and coordination. The cerebellar hemispheres form from dorsal outgrowths of the metencephalon, developing the vermis and cerebellar cortex for fine motor control.
5) Clinical-type: Damage to the olive of medulla affects which function?
a) Auditory processing
b) Coordination
c) Taste
d) Smell
Explanation: The inferior olivary nucleus in the medulla assists cerebellar coordination by relaying sensory and motor information. Lesions disrupt timing and precision of movements, causing ataxia. This nucleus originates embryologically within the myelencephalon, confirming its role in medullary circuitry.
6) The diencephalon gives rise to ?
a) Thalamus and hypothalamus
b) Pons and medulla
c) Cerebral cortex
d) Midbrain
Explanation: The diencephalon forms structures like the thalamus, hypothalamus, epithalamus, and subthalamus. These regulate sensory relay, endocrine control, and autonomic functions. Positioned between the midbrain and telencephalon, it plays a central role in sensory integration and emotional processing via hypothalamic connections.
7) Clinical-type: A newborn with Arnold–Chiari malformation shows medullary herniation. Which embryonic part was affected?
a) Myelencephalon
b) Metencephalon
c) Telencephalon
d) Mesencephalon
Explanation: Arnold–Chiari malformation involves herniation of medulla (derived from myelencephalon) into the foramen magnum, compressing brainstem structures. This congenital defect leads to respiratory and swallowing issues, reflecting the medulla’s role in autonomic and cranial nerve function.
8) Which of the following is not derived from the rhombencephalon?
a) Pons
b) Cerebellum
c) Medulla
d) Midbrain
Explanation: The midbrain develops from the mesencephalon, not the rhombencephalon. The rhombencephalon gives rise to the pons, cerebellum, and medulla, collectively forming the hindbrain responsible for coordination, autonomic control, and reflex activity.
9) Clinical-type: A patient with loss of gag reflex has lesion in which structure derived from myelencephalon?
a) Nucleus ambiguus
b) Red nucleus
c) Substantia nigra
d) Thalamus
Explanation: The nucleus ambiguus in the medulla, derived from the myelencephalon, controls muscles of the pharynx and larynx via cranial nerves IX and X. Lesions impair the gag reflex, swallowing, and phonation. This highlights the medulla’s role in cranial nerve integration.
10) The telencephalon develops into ?
a) Cerebral hemispheres
b) Pons
c) Midbrain
d) Cerebellum
Explanation: The telencephalon forms the cerebral hemispheres, basal ganglia, and olfactory bulbs. These structures handle higher cognitive, emotional, and voluntary motor functions. As the most anterior brain vesicle, it develops from the prosencephalon during week five of embryonic development.
Chapter: Embryology; Topic: Early Development of Embryo; Subtopic: Cleavage and Morula Formation
Keyword Definitions:
Morula: A solid ball of blastomeres formed after cleavage, usually consisting of 16 cells before transforming into the blastocyst.
Cleavage: Rapid mitotic divisions of the zygote without growth, producing smaller cells called blastomeres.
Blastocyst: A hollow structure formed from the morula, consisting of an inner cell mass and trophoblast.
Blastomere: Individual cells formed during the cleavage of the zygote.
Lead Question - 2014
Morula is how many celled -
a) 4
b) 8
c) 12
d) 16
Explanation: The morula is typically a 16-celled stage of embryonic development formed after several cleavage divisions of the zygote. It appears around the 3rd day after fertilization, resembling a mulberry. The cells (blastomeres) of the morula are compacted together through tight junctions, leading to differentiation into inner and outer cell masses that form the blastocyst.
1) The blastocyst stage is formed on which day after fertilization?
a) 2nd day
b) 4th day
c) 6th day
d) 8th day
Explanation: The blastocyst forms on the 4th day after fertilization when the morula develops a fluid-filled cavity known as the blastocoel. The inner cell mass becomes the embryo proper, while the trophoblast develops into the placenta. This stage implants into the uterine wall by day 6–7.
2) The process of compaction during cleavage results in -
a) Formation of blastomeres
b) Formation of morula
c) Differentiation of inner and outer cells
d) Implantation
Explanation: Compaction occurs at the 8-cell stage, resulting in tight junctions between blastomeres that differentiate into inner and outer cells, forming the morula. This structural reorganization establishes polarity, preparing the embryo for blastocyst formation and implantation readiness.
3) Clinical-type: A 3-day-old embryo in fallopian tube shows 16 cells. What is this stage called?
a) Zygote
b) Blastocyst
c) Morula
d) Gastrula
Explanation: A 3-day-old embryo with 16 cells represents the morula stage. It travels through the fallopian tube before entering the uterus. The compacted blastomeres prepare for differentiation into inner and outer layers, marking the first step toward formation of the blastocyst.
4) The outer cell mass of the blastocyst forms -
a) Embryo proper
b) Amniotic cavity
c) Trophoblast
d) Neural tube
Explanation: The outer cell mass of the blastocyst forms the trophoblast, which contributes to the development of the placenta. The trophoblast later differentiates into cytotrophoblast and syncytiotrophoblast, essential for implantation and nutrient exchange.
5) Clinical-type: A woman has ectopic pregnancy; the implanted stage observed was a blastocyst. Which stage preceded it?
a) Morula
b) Gastrula
c) 8-cell stage
d) Zygote
Explanation: The morula precedes the blastocyst stage. In ectopic pregnancy, this morula undergoes abnormal implantation in the fallopian tube. It marks an early post-cleavage phase before the blastocoel cavity forms, leading to trophoblast differentiation and eventual abnormal fixation.
6) The inner cell mass of blastocyst forms -
a) Embryo proper
b) Placenta
c) Amniotic fluid
d) Decidua
Explanation: The inner cell mass forms the embryo proper and extraembryonic membranes. It gives rise to all three germ layers — ectoderm, mesoderm, and endoderm. These layers later form organs, tissues, and body systems, marking it as a key step in embryogenesis.
7) Clinical-type: During IVF, an embryo ready for uterine transfer shows 16 cells. Which term describes it?
a) Zygote
b) Blastocyst
c) Morula
d) Gastrula
Explanation: A 16-celled embryo observed during in vitro fertilization corresponds to the morula stage. This is ideal for uterine transfer because it ensures early implantation success and correct endometrial synchronization. It indicates active cleavage with compacted cells prior to blastulation.
8) The zygote undergoes its first cleavage after how many hours?
a) 6 hours
b) 12 hours
c) 24 hours
d) 36 hours
Explanation: The first cleavage of the zygote occurs at approximately 24 hours post-fertilization, resulting in two blastomeres. This marks the beginning of rapid mitotic divisions that will ultimately lead to the morula and blastocyst stages, essential for implantation.
9) Clinical-type: A biopsy from early conceptus shows outer trophoblastic cells and inner mass. The developmental stage is -
a) Morula
b) Blastocyst
c) Gastrula
d) Neurula
Explanation: The described structure represents a blastocyst, characterized by a trophoblast and an inner cell mass. The trophoblast later invades the endometrium during implantation. This stage follows the morula, signifying the start of differentiation and cavity formation.
10) Zona pellucida is lost during which stage?
a) 2-cell stage
b) Morula
c) Blastocyst
d) Gastrula
Explanation: The zona pellucida is shed during the blastocyst stage in a process called hatching. This allows implantation into the uterine wall. The morula remains within the zona pellucida until fluid accumulation and expansion trigger the formation of the blastocyst cavity.
Chapter: Embryology; Topic: Development of Tooth; Subtopic: Origin and Differentiation of Dental Structures
Keyword Definitions:
Dental Papilla: A condensation of ectomesenchymal cells beneath the enamel organ that forms dentin and pulp of the tooth.
Enamel Organ: An epithelial structure that gives rise to enamel-producing ameloblasts.
Dentin: Hard tissue beneath the enamel formed by odontoblasts derived from the dental papilla.
Dental Follicle: Connective tissue surrounding the developing tooth germ that gives rise to cementum and periodontal ligament.
Lead Question - 2014
Dental papilla give rise to ?
a) Enamel
b) Dental cuticle
c) Tooth pulp
d) None
Explanation: The dental papilla gives rise to dentin and the tooth pulp. It is derived from ectomesenchymal cells of the neural crest. Odontoblasts within the dental papilla secrete dentin, while the central cells remain as pulp. The enamel, however, arises from the enamel organ, not the dental papilla.
1) Which structure forms enamel of the tooth?
a) Dental papilla
b) Enamel organ
c) Dental follicle
d) Odontoblasts
Explanation: Enamel is formed by ameloblasts, which arise from the inner enamel epithelium of the enamel organ. It is the hardest tissue in the human body and is non-regenerative once formed. In contrast, dentin and pulp are derived from the dental papilla.
2) Clinical-type: In a child with dentinogenesis imperfecta, which embryonic structure is defective?
a) Dental papilla
b) Enamel organ
c) Dental follicle
d) Buccal mucosa epithelium
Explanation: Dentinogenesis imperfecta involves defective dentin formation due to abnormal odontoblast function from the dental papilla. The result is translucent teeth with weak structural integrity. Enamel remains normal but fractures easily because of poor dentin support.
3) The dental follicle gives rise to -
a) Enamel
b) Dentin
c) Cementum
d) Pulp
Explanation: The dental follicle forms the cementum, periodontal ligament, and alveolar bone. These supporting structures collectively form the periodontium. The follicle originates from surrounding ectomesenchymal tissue and plays a key role in tooth eruption and anchoring.
4) Clinical-type: A 7-year-old boy shows a radiolucent lesion around a tooth crown. Histology reveals remnants of enamel organ. The lesion is likely -
a) Dental cyst
b) Ameloblastoma
c) Dentigerous cyst
d) Odontoma
Explanation: A dentigerous cyst originates from remnants of the enamel organ around the crown of unerupted teeth. It is an odontogenic cyst associated with the reduced enamel epithelium. Dental papilla or follicle remnants can contribute to such developmental pathologies.
5) The cells that form dentin are known as -
a) Odontoblasts
b) Ameloblasts
c) Cementoblasts
d) Osteoblasts
Explanation: Odontoblasts form dentin and are derived from the outer cells of the dental papilla. These cells deposit predentin that later mineralizes. Once dentin formation begins, ameloblasts from the enamel organ form enamel in a reciprocal induction process.
6) Clinical-type: A tooth with exposed dentin but intact pulp indicates injury to which layer?
a) Enamel
b) Pulp
c) Cementum
d) Periodontal ligament
Explanation: Exposure of dentin occurs when the enamel is eroded or lost due to trauma or caries. The dentin arises from odontoblasts of the dental papilla, while the pulp remains unexposed initially. Prolonged exposure may lead to pulp inflammation (pulpitis).
7) The dental papilla is derived from which embryonic origin?
a) Endoderm
b) Mesoderm
c) Neural crest ectomesenchyme
d) Surface ectoderm
Explanation: The dental papilla originates from neural crest-derived ectomesenchyme. These specialized cells migrate into the developing jaw region, giving rise to odontoblasts and pulp tissue. This neural crest origin explains the tooth’s sensitivity and neurovascular connections.
8) Clinical-type: A patient has enamel hypoplasia but normal dentin. Which part was defective during development?
a) Dental papilla
b) Enamel organ
c) Dental follicle
d) Periodontal membrane
Explanation: Enamel hypoplasia results from defective ameloblasts in the enamel organ. The dental papilla, responsible for dentin and pulp, remains unaffected. Causes include nutritional deficiency, trauma, or systemic disease during tooth development.
9) Which component of the tooth is of ectodermal origin?
a) Enamel
b) Dentin
c) Cementum
d) Pulp
Explanation: Enamel is the only tooth structure derived from ectoderm, formed by ameloblasts from the enamel organ. In contrast, dentin, pulp, and cementum are mesenchymal derivatives from neural crest ectomesenchyme.
10) Clinical-type: In tooth regeneration research, stem cells are derived from which embryonic component to form pulp-like tissue?
a) Enamel organ
b) Dental papilla
c) Dental follicle
d) Buccal epithelium
Explanation: Dental stem cells with regenerative potential are obtained from the dental papilla. These cells can differentiate into odontoblast-like and pulp-like tissues. This discovery supports advances in regenerative dentistry, helping in pulp repair and tissue engineering.
Chapter: Embryology; Topic: Development of Pharyngeal Arches; Subtopic: Derivatives of Pharyngeal Arches
Keyword Definitions:
• Pharyngeal Arches: Series of tissue bands in the embryonic head and neck that give rise to structures of the face, neck, and pharynx.
• Malleus and Incus: Middle ear ossicles responsible for sound transmission.
• Mandibular Arch (First Arch): The first pharyngeal arch forming mandible, malleus, incus, and associated muscles.
• Meckel’s Cartilage: Cartilage within the first arch forming malleus and incus.
• Stapes: Derived from the second pharyngeal arch (Reichert’s cartilage).
Lead Question - 2014
Malleus and incus are derived from ?
a) 1st Arch
b) 2nd Arch
c) 3rd Arch
d) 4th Arch
Explanation:
The malleus and incus arise from Meckel’s cartilage of the first pharyngeal (mandibular) arch. This arch gives rise to structures such as the mandible, malleus, incus, and associated muscles like tensor tympani. The stapes and styloid process originate from the second arch. Hence, the correct answer is 1st Arch.
1) Stapes is derived from?
a) 1st Arch
b) 2nd Arch
c) 3rd Arch
d) 4th Arch
Explanation: The stapes, styloid process, and part of the hyoid bone develop from the second (hyoid) arch, also called Reichert’s cartilage. This arch contributes to facial muscles and structures related to the stapes. Thus, the correct answer is 2nd Arch.
2) Meckel’s cartilage contributes to formation of?
a) Hyoid bone
b) Mandible
c) Stapes
d) Styloid process
Explanation: Meckel’s cartilage, derived from the first pharyngeal arch, acts as a template for the mandible. The anterior ligament of malleus and sphenomandibular ligament also arise from it. Thus, the correct answer is Mandible.
3) Which muscle is derived from the first pharyngeal arch?
a) Stylopharyngeus
b) Buccinator
c) Tensor tympani
d) Cricothyroid
Explanation: The first pharyngeal arch gives rise to the muscles of mastication (masseter, temporalis, pterygoids), mylohyoid, anterior belly of digastric, and tensor tympani. Hence, the correct answer is Tensor tympani.
4) Nerve supply of first pharyngeal arch?
a) Facial nerve
b) Mandibular nerve
c) Glossopharyngeal nerve
d) Vagus nerve
Explanation: The mandibular division of the trigeminal nerve (CN V3) supplies all muscles derived from the first pharyngeal arch, including the muscles of mastication and tensor tympani. Thus, the correct answer is Mandibular nerve.
5) The second pharyngeal arch cartilage is called?
a) Meckel’s cartilage
b) Reichert’s cartilage
c) Thyroid cartilage
d) Cricoid cartilage
Explanation: The second arch cartilage is known as Reichert’s cartilage. It forms the stapes, styloid process, stylohyoid ligament, and upper part of the hyoid bone. Hence, the correct answer is Reichert’s cartilage.
6) A newborn with micrognathia and malformed malleus likely has a defect in?
a) 1st Arch
b) 2nd Arch
c) 3rd Arch
d) 4th Arch
Explanation: Both the mandible and malleus develop from the first arch. Micrognathia and malformed malleus therefore indicate a first pharyngeal arch developmental anomaly. Thus, the correct answer is 1st Arch.
7) Muscles of facial expression arise from?
a) First arch
b) Second arch
c) Third arch
d) Fourth arch
Explanation: The muscles of facial expression, including orbicularis oculi and buccinator, originate from the second pharyngeal (hyoid) arch. They are innervated by the facial nerve (CN VII). Therefore, the correct answer is Second arch.
8) Third pharyngeal arch gives rise to?
a) Styloid process
b) Greater horn of hyoid
c) Cricoid cartilage
d) Mandible
Explanation: The third arch contributes to the greater horn and lower part of the hyoid bone and the stylopharyngeus muscle. The glossopharyngeal nerve (CN IX) innervates this arch. Thus, the correct answer is Greater horn of hyoid.
9) A child with facial paralysis and absence of stapes development has a defect in?
a) First arch
b) Second arch
c) Third arch
d) Fourth arch
Explanation: The facial nerve (CN VII) and stapes both derive from the second pharyngeal arch. Hence, congenital absence of stapes with facial paralysis suggests second arch abnormality. The correct answer is Second arch.
10) Derivatives of fourth pharyngeal arch include?
a) Muscles of mastication
b) Stylopharyngeus
c) Cricothyroid
d) Mylohyoid
Explanation: The fourth arch forms cricothyroid, levator veli palatini, and pharyngeal constrictors. It is supplied by the superior laryngeal branch of the vagus nerve. Hence, the correct answer is Cricothyroid.
Chapter: Embryology; Topic: Development of Eye; Subtopic: Derivatives of Germ Layers in Eye Formation
Keyword Definitions:
• Optic Cup: A double-walled structure formed from the optic vesicle that gives rise to the retina.
• Neural Ectoderm: Layer of ectoderm giving rise to the brain, spinal cord, retina, and posterior pituitary.
• Surface Ectoderm: Gives rise to lens, corneal epithelium, and eyelid skin.
• Mesoderm: Forms extraocular muscles and vascular components of the eye.
• Neural Crest Cells: Contribute to corneal stroma, sclera, choroid, and ciliary muscles.
Lead Question - 2014
Optic cup is derived from ?
a) Neural ectoderm
b) Surface ectoderm
c) Mesoderm
d) Neural crest
Explanation:
The optic cup is derived from the neural ectoderm, which originates as an outpouching from the diencephalon. The outer layer of the optic cup becomes the pigmented layer of the retina, and the inner layer forms the neural retina. This dual-layered cup induces lens formation from surface ectoderm. Thus, the correct answer is Neural ectoderm.
1) The lens of the eye is derived from?
a) Surface ectoderm
b) Neural ectoderm
c) Neural crest
d) Mesoderm
Explanation: The crystalline lens develops from the surface ectoderm, which forms the lens placode in response to induction from the optic vesicle. This placode invaginates to form the lens vesicle. Thus, the correct answer is Surface ectoderm.
2) The retina is derived from?
a) Surface ectoderm
b) Neural ectoderm
c) Neural crest
d) Mesoderm
Explanation: Both the neural and pigmented layers of the retina originate from the neural ectoderm, which forms the optic vesicle and subsequently the optic cup. Therefore, the correct answer is Neural ectoderm.
3) Corneal endothelium develops from?
a) Neural crest cells
b) Neural ectoderm
c) Mesoderm
d) Surface ectoderm
Explanation: Neural crest cells migrate between the lens and surface ectoderm to form the corneal endothelium and stroma. The corneal epithelium arises from surface ectoderm. Thus, the correct answer is Neural crest cells.
4) Which of the following eye structures arises from mesoderm?
a) Iris
b) Lens
c) Extraocular muscles
d) Retina
Explanation: The extraocular muscles and blood vessels of the eye arise from mesoderm, contributing to movement and vascularization of the eye. Hence, the correct answer is Extraocular muscles.
5) A defect in closure of the optic fissure leads to?
a) Anophthalmos
b) Coloboma
c) Cyclopia
d) Glaucoma
Explanation: Failure of the embryonic optic fissure to close results in coloboma, a keyhole-shaped defect in the iris, retina, or choroid. This occurs during the 5th week of development. Thus, the correct answer is Coloboma.
6) A baby born with absence of lens most likely had developmental failure of?
a) Neural ectoderm
b) Surface ectoderm
c) Mesoderm
d) Neural crest
Explanation: The lens develops from the surface ectoderm via the lens placode. Failure of placode induction or invagination results in congenital aphakia (absence of lens). Thus, the correct answer is Surface ectoderm.
7) Which structure induces lens formation in the embryo?
a) Optic cup
b) Surface ectoderm
c) Neural crest
d) Mesoderm
Explanation: The optic cup derived from neural ectoderm induces the overlying surface ectoderm to form the lens placode through epithelial-mesenchymal interactions. Thus, the correct answer is Optic cup.
8) The sclera and choroid are derived from?
a) Surface ectoderm
b) Mesoderm and neural crest
c) Neural ectoderm
d) Endoderm
Explanation: The sclera and choroid develop mainly from neural crest cells, with mesodermal contribution to vascular structures. They form the fibrous and vascular coats of the eyeball. Hence, the correct answer is Mesoderm and neural crest.
9) A neonate presents with a cleft in the iris and retina. The developmental cause is?
a) Failure of lens vesicle separation
b) Persistence of hyaloid artery
c) Nonclosure of optic fissure
d) Overgrowth of choroid
Explanation: Nonclosure of the embryonic optic fissure results in coloboma affecting iris or retina. It manifests as a characteristic cleft defect. Thus, the correct answer is Nonclosure of optic fissure.
10) Neural crest cells contribute to which ocular structure?
a) Corneal stroma
b) Lens capsule
c) Retina
d) Iris epithelium
Explanation: Neural crest cells form corneal stroma, corneal endothelium, sclera, and ciliary muscles. They do not contribute to retina or lens. Hence, the correct answer is Corneal stroma.
Chapter: Embryology; Topic: Development of Eye; Subtopic: Derivatives of the Optic Cup
Keyword Definitions:
• Optic Cup: A double-layered structure derived from the optic vesicle, forming retina and related structures.
• Retina: Neural tissue responsible for photoreception and visual transmission.
• Lens: Transparent, biconvex structure focusing light on the retina.
• Cornea: Transparent front part of the eye formed from surface ectoderm and neural crest.
• Sclera: Dense connective tissue forming the outer protective layer of the eyeball, derived from mesoderm and neural crest.
Lead Question - 2014
Optic cup give rise to ?
a) Lens
b) Retina
c) Cornea
d) Sclera
Explanation:
The optic cup, derived from neural ectoderm, gives rise to the retina — both its neural and pigmented layers. The inner layer forms the neural retina, while the outer layer becomes the retinal pigment epithelium. It also contributes to the iris and ciliary body epithelium. Thus, the correct answer is Retina.
1) The outer layer of the optic cup forms?
a) Neural retina
b) Pigmented retina
c) Cornea
d) Lens capsule
Explanation: The optic cup has two layers — the outer layer forms the retinal pigment epithelium, and the inner layer becomes the neural retina. This double-walled cup structure is essential for visual function. Therefore, the correct answer is Pigmented retina.
2) The ciliary body epithelium develops from?
a) Surface ectoderm
b) Neural ectoderm of optic cup
c) Neural crest
d) Mesoderm
Explanation: The epithelium of the ciliary body arises from the anterior extension of both layers of the optic cup, which is of neural ectodermal origin. The connective tissue and muscles of the ciliary body are derived from neural crest cells. Thus, the correct answer is Neural ectoderm of optic cup.
3) Which of the following structures is derived from the inner layer of the optic cup?
a) Retinal pigment epithelium
b) Neural retina
c) Corneal endothelium
d) Lens fibers
Explanation: The inner layer of the optic cup forms the neural retina, which contains photoreceptor cells, bipolar cells, and ganglion cells responsible for vision. Hence, the correct answer is Neural retina.
4) During eye development, lens formation is induced by?
a) Optic vesicle
b) Optic cup
c) Surface ectoderm
d) Neural crest
Explanation: The optic vesicle induces the overlying surface ectoderm to form the lens placode, which invaginates to form the lens vesicle. This inductive interaction is a classic example of epithelial-mesenchymal signaling. Thus, the correct answer is Optic vesicle.
5) A developmental defect in closure of the optic fissure leads to?
a) Aniridia
b) Coloboma
c) Microphthalmia
d) Glaucoma
Explanation: Failure of the embryonic optic fissure to close leads to coloboma, a cleft-like defect usually seen in the iris, choroid, or retina. It may affect one or both eyes. Thus, the correct answer is Coloboma.
6) The iris pigment epithelium develops from?
a) Surface ectoderm
b) Mesoderm
c) Neural ectoderm of optic cup
d) Neural crest
Explanation: The iris pigment epithelium originates from the outer layer of the optic cup, which is neural ectoderm in origin. The connective tissue of the iris is derived from neural crest cells. Hence, the correct answer is Neural ectoderm of optic cup.
7) A neonate presents with a cleft in the inferior iris. The most likely developmental defect is?
a) Failure of optic cup formation
b) Non-closure of choroidal fissure
c) Persistence of hyaloid artery
d) Absent lens placode
Explanation: Non-closure of the choroidal (optic) fissure during embryogenesis causes coloboma, presenting as a notched iris. It results from incomplete fusion of the optic cup margins. Thus, the correct answer is Non-closure of choroidal fissure.
8) Which germ layer gives rise to the corneal epithelium?
a) Surface ectoderm
b) Neural ectoderm
c) Mesoderm
d) Neural crest
Explanation: The corneal epithelium originates from surface ectoderm, while its stroma and endothelium develop from neural crest cells. The cornea is vital for light refraction and transparency. Thus, the correct answer is Surface ectoderm.
9) Failure of lens vesicle separation leads to?
a) Congenital aphakia
b) Persistent lens stalk
c) Microcornea
d) Coloboma
Explanation: Incomplete separation of the lens vesicle from the surface ectoderm causes persistent lens stalk, potentially forming epithelial pearls. It interferes with corneal development. Hence, the correct answer is Persistent lens stalk.
10) Neural crest cells contribute to all except?
a) Sclera
b) Corneal stroma
c) Retina
d) Iris connective tissue
Explanation: Neural crest cells form the sclera, corneal stroma, corneal endothelium, and connective tissue of the iris and ciliary body. The retina, however, is derived from neural ectoderm. Thus, the correct answer is Retina.
Chapter: Embryology; Topic: Development of Urogenital System; Subtopic: Development of Kidney
Keyword Definitions:
Ureteric Bud: An outgrowth from the mesonephric duct that forms the collecting system of the kidney.
Metanephros: The permanent kidney that appears in the fifth week of development.
Nephron: The functional filtration unit of the kidney derived from metanephric blastema.
Pronephros and Mesonephros: Primitive kidneys that function temporarily during early embryonic life.
Lead Question - 2014
Excretory system of kidney is derived from?
a) Ureteric bud
b) Mesonephros
c) Metanephros
d) None
Explanation:
The excretory system of the kidney, including nephrons, originates from the metanephric mesoderm (metanephros), while the collecting ducts, calyces, pelvis, and ureter arise from the ureteric bud. Metanephros appears by the 5th week and becomes the permanent kidney. Hence, the correct answer is c) Metanephros.
1. Which part of the kidney develops from the ureteric bud?
a) Glomerulus
b) Collecting ducts
c) Bowman’s capsule
d) Loop of Henle
Explanation:
The ureteric bud gives rise to the collecting ducts, renal pelvis, major and minor calyces, and ureter. The excretory units, including the glomerulus and nephron tubules, come from the metanephric mesenchyme. Therefore, the correct answer is b) Collecting ducts.
2. The metanephric blastema contributes to the formation of:
a) Collecting ducts
b) Nephrons
c) Ureter
d) Pelvis
Explanation:
The metanephric blastema differentiates into nephrons including Bowman’s capsule, proximal tubule, loop of Henle, and distal convoluted tubule. It interacts with the ureteric bud to form the complete kidney structure. Hence, the answer is b) Nephrons.
3. Clinical: A neonate presents with bilateral renal agenesis. Which embryological structure failed to develop?
a) Pronephros
b) Ureteric bud
c) Mesonephros
d) Metanephric blastema
Explanation:
Bilateral renal agenesis occurs due to the failure of the ureteric bud to form or interact with the metanephric blastema. This leads to the absence of both kidneys and causes oligohydramnios (Potter’s sequence). The correct answer is b) Ureteric bud.
4. The ureter develops from:
a) Metanephric blastema
b) Mesonephros
c) Ureteric bud
d) Wolffian duct
Explanation:
The ureter develops as a continuation of the ureteric bud, which sprouts from the Wolffian duct. This bud elongates and differentiates to form the ureter, pelvis, and collecting system of the kidney. Thus, the correct answer is c) Ureteric bud.
5. Clinical: Hydronephrosis in a fetus results mainly due to obstruction in which embryonic derivative?
a) Ureteric bud
b) Metanephros
c) Pronephros
d) Mesonephric duct
Explanation:
Hydronephrosis is caused by obstruction in the ureter or collecting system, which are derivatives of the ureteric bud. Obstruction prevents urine outflow, leading to dilatation of renal pelvis and calyces. Therefore, the correct answer is a) Ureteric bud.
6. Pronephros in humans is:
a) Functional
b) Non-functional
c) Forms nephrons
d) Gives rise to ureter
Explanation:
Pronephros is the first and most primitive form of the kidney in human embryology. It appears early in the 4th week and is non-functional, regressing completely. Hence, the correct answer is b) Non-functional.
7. Clinical: A child with duplicated ureter likely had abnormal branching of which embryonic structure?
a) Mesonephric duct
b) Metanephric blastema
c) Ureteric bud
d) Cloaca
Explanation:
Duplicated ureter occurs due to early division or duplication of the ureteric bud. Each branch may induce separate regions of metanephric tissue, forming two ureters or pelves. Thus, the answer is c) Ureteric bud.
8. Mesonephros contributes to formation of:
a) Testis
b) Kidney
c) Urethra
d) Ovarian follicle
Explanation:
Mesonephros acts as a temporary excretory organ in embryos and contributes to the formation of genital structures such as efferent ducts in males and vestigial remnants in females. Thus, the correct answer is a) Testis.
9. Clinical: Horseshoe kidney results from fusion of the:
a) Ureteric buds
b) Lower poles of metanephric blastema
c) Mesonephric ducts
d) Cloaca
Explanation:
Horseshoe kidney forms when the lower poles of metanephric blastema fuse before ascent. During ascent, the fused kidney gets trapped under the inferior mesenteric artery. The correct answer is b) Lower poles of metanephric blastema.
10. The collecting tubules of kidney arise from:
a) Ureteric bud
b) Metanephric blastema
c) Mesonephros
d) Cloacal membrane
Explanation:
Collecting tubules develop as terminal branches of the ureteric bud. These tubules connect with the distal ends of nephrons derived from the metanephric blastema, allowing urine drainage. Therefore, the correct answer is a) Ureteric bud.