DNB CET Anatomy Syllabus

Classify joints structurally and give an example of each.

Fibrous (sutures of skull, syndesmosis), cartilaginous (primary/synchondrosis-epiphyseal plate; secondary/symphysis-pubic symphysis), and synovial (knee, shoulder).

Compare the three types of cartilage by matrix and location.

Hyaline: type II collagen, glassy matrix, articular surfaces/costal cartilage. Elastic: elastic fibres, epiglottis/external ear. Fibrocartilage: type I collagen, dense, intervertebral discs/menisci/pubic symphysis.

Describe the microarchitecture of compact bone (osteon/Haversian system).

An osteon consists of concentric lamellae around a central Haversian canal (carrying vessels/nerves); osteocytes lie in lacunae connected by canaliculi; Volkmann's canals connect Haversian canals transversely.

Distinguish the histology of primary vs secondary lymphoid organs.

Primary (thymus, bone marrow): site of lymphocyte production/maturation. Secondary (lymph nodes, spleen, MALT/tonsils): site of antigen-driven immune response. Thymus has Hassall's corpuscles in its medulla.

Name the three layers (tunics) of a blood vessel wall and their main components.

Tunica intima (endothelium + internal elastic lamina), tunica media (smooth muscle + elastic fibres), tunica adventitia (connective tissue, vasa vasorum). Elastic arteries have abundant elastin in the media.

Outline the key stages of spermatogenesis from spermatogonium to spermatozoon.

Spermatogonium → primary spermatocyte (meiosis I) → two secondary spermatocytes → four spermatids (meiosis II) → spermatozoa via spermiogenesis. Takes ~64-74 days; produces 4 functional gametes.

How does oogenesis differ from spermatogenesis in number and timing?

Oogenesis yields one ovum + polar bodies (unequal cytoplasmic division); begins in fetal life, arrests in prophase I until puberty (ovulation) and in metaphase II until fertilization. One gamete vs four in spermatogenesis.

Where does fertilization normally occur and what marks its completion?

In the ampulla of the uterine (fallopian) tube. Completion is marked by fusion of male and female pronuclei to form the diploid zygote, with the cortical reaction preventing polyspermy.

Describe the timing and site of normal implantation.

The blastocyst implants in the posterior superior wall of the uterine body, in the functional layer of the endometrium, around day 6-7 after fertilization, completing by about day 10-12.

List the principal derivatives of each of the three germ layers.

Ectoderm: epidermis, nervous system, neural crest. Mesoderm: muscle, bone, blood, cardiovascular, kidneys, gonads, dermis. Endoderm: epithelial lining of GI/respiratory tracts, liver, pancreas, thyroid, bladder lining.

What is gastrulation and what structure initiates it?

Gastrulation is the process forming the three germ layers from the bilaminar to trilaminar disc. It begins with formation of the primitive streak; epiblast cells invaginate to form endoderm and mesoderm.

Match each pharyngeal arch to its nerve.

Arch 1: trigeminal (V3); Arch 2: facial (VII); Arch 3: glossopharyngeal (IX); Arch 4 & 6: vagus (X) — arch 4 via superior laryngeal, arch 6 via recurrent laryngeal. (Arch 5 regresses.)

List the main muscle/skeletal derivatives of the first pharyngeal arch.

Muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini. Skeletal: malleus, incus, Meckel's cartilage (template for mandible).

What are the derivatives of the pharyngeal (endodermal) pouches 1-4?

Pouch 1: tubotympanic recess (middle ear, auditory tube). Pouch 2: palatine tonsil. Pouch 3: inferior parathyroids + thymus. Pouch 4: superior parathyroids + ultimobranchial body (C cells).

Which pharyngeal cleft persists and what anomaly arises from the others?

Only the first cleft persists, forming the external acoustic meatus. Clefts 2-4 are normally obliterated by the cervical sinus; their persistence produces a branchial (cervical) cyst or fistula along the anterior border of sternocleidomastoid.

From which embryonic structures do the great vessels (aortic arch derivatives) form?

3rd arch: common carotid + proximal internal carotid. 4th arch: left = arch of aorta, right = proximal right subclavian. 6th arch: pulmonary arteries; left also forms ductus arteriosus.

Explain the embryological basis of Tetralogy of Fallot.

It results from anterosuperior displacement of the infundibular (conotruncal/aorticopulmonary) septum, causing: pulmonary stenosis, VSD, overriding aorta, and right ventricular hypertrophy.

What is the embryological cause of transposition of the great arteries?

Failure of the aorticopulmonary (conotruncal) septum to spiral, so it runs straight, resulting in the aorta arising from the right ventricle and the pulmonary trunk from the left ventricle.

Describe the normal rotation of the midgut and the defect causing malrotation.

The midgut herniates and rotates 270° counterclockwise around the superior mesenteric artery axis, then returns to the abdomen by ~week 10. Incomplete/abnormal rotation predisposes to volvulus and Ladd's bands.

What is the embryological defect in spina bifida and anencephaly?

Failure of neural tube closure: failure of the caudal (posterior) neuropore → spina bifida; failure of the cranial (anterior) neuropore → anencephaly. Associated with low folate; raised maternal AFP.

Trace the pathway of the lateral spinothalamic tract.

Carries pain/temperature. First-order neuron enters dorsal horn; second-order neuron decussates within 1-2 segments via the anterior white commissure, ascends contralaterally to the VPL of the thalamus; third-order projects to the postcentral gyrus.

Describe the course and decussation of the dorsal column-medial lemniscus pathway.

Carries fine touch, vibration, proprioception. First-order ascends ipsilaterally in fasciculus gracilis/cuneatus to the gracile/cuneate nuclei in the medulla; second-order decussates as internal arcuate fibres forming the medial lemniscus to the VPL thalamus.

Where does the lateral corticospinal (pyramidal) tract decussate and what does it control?

About 85-90% of fibres decussate at the pyramidal decussation in the lower medulla, then descend in the lateral funiculus to control contralateral limb (distal/fine voluntary) movement.

Name the major nuclei of the basal ganglia.

Caudate nucleus, putamen, globus pallidus (externa and interna), with the functionally associated subthalamic nucleus and substantia nigra. Caudate + putamen = striatum; putamen + globus pallidus = lentiform nucleus.

Describe the parts of the internal capsule and what passes through the genu and posterior limb.

Parts: anterior limb, genu, posterior limb, retrolenticular and sublenticular portions. Genu carries corticobulbar fibres; posterior limb carries corticospinal fibres and sensory (thalamocortical) fibres.

List the major thalamic nuclei and one key projection of each.

VPL (body somatosensory → postcentral gyrus), VPM (face/taste), VL (cerebellar/basal ganglia → motor cortex), LGB (vision → occipital), MGB (hearing → temporal), anterior nucleus (limbic/Papez circuit).

Name the three cerebellar peduncles and the main fibres each carries.

Superior (efferent: dentatorubrothalamic to red nucleus/thalamus; afferent ventral spinocerebellar), middle (afferent: pontocerebellar from contralateral pons), inferior (afferent: dorsal spinocerebellar, olivocerebellar, vestibular).

Describe the functional zones of the cerebellum and their roles.

Vestibulocerebellum (flocculonodular lobe): balance/eye movements. Spinocerebellum (vermis + paravermis): posture/gait/muscle tone. Cerebrocerebellum (lateral hemispheres): planning/coordination of fine voluntary movement.

Trace the circulation of cerebrospinal fluid from production to absorption.

Produced by choroid plexus in the lateral ventricles → interventricular foramina of Monro → third ventricle → cerebral aqueduct of Sylvius → fourth ventricle → foramina of Luschka (×2) and Magendie → subarachnoid space → absorbed by arachnoid granulations into the dural venous sinuses.

At what level does the spinal cord end in adults and what is the clinical relevance for lumbar puncture?

The conus medullaris ends at approximately L1-L2 in adults. Lumbar puncture is performed at the L3-L4 or L4-L5 interspace (below the cord) to safely sample CSF from the lumbar cistern containing the cauda equina.