Paper I — Q4
Describe the facial nerve under the following headings: 1. Functional columns and nuclei of origin 2. Course and branches 3…
Describe the facial nerve under the following headings: 1. Functional columns and nuclei of origin 2. Course and branches 3. Bell's palsy
Differentiate between indirect and direct inguinal hernia.
Define renal clearance. What key features should be present in a compound for it to be considered as a 'gold standard' for measurement of renal clearance? Explain why urea is not considered as a 'gold standard' for this.
Briefly describe the role of Restriction Fragment Length Polymorphism (RFLP) in DNA fingerprinting.
Give the physiological basis of anaemia in kidney and liver disease.
Describe the role of eosinophils in control of allergy reactions.
Describe the role of platelets in haemostasis.
हिंदी में प्रश्न पढ़ें
आनन तंत्रिका का वर्णन निम्नलिखित शीर्षकों के अंतर्गत कीजिए : 1. क्रियात्मक स्तंभ तथा उद्गम के केंद्रक 2. मार्ग एवं शाखाएं 3. बेल पाल्सी
तिर्यक वंक्षण हर्निया तथा ऋजु वंक्षण हर्निया के बीच भेद बताइए।
वृक्क उत्सर्जन की परिभाषा दीजिए। किसी यौगिक में ऐसे कौन-कौन से मुख्य गुण विद्यमान होने चाहिए जिससे कि वह वृक्क उत्सर्जन मापन का 'स्वर्ण मानक' माना जा सके? समझाइए कि क्यों यूरिया, वृक्क उत्सर्जन मापन का 'स्वर्ण मानक' नहीं माना जाता।
डी० एन० ए० अंगुलि छाप (फिंगरप्रिंटिंग) में प्रतिबंध खंड दैर्घ्य बहुरूपता (आर० एफ० एल० पी०) की भूमिका का संक्षेप में वर्णन कीजिए।
वृक्क रोग तथा यकृत रोग में होने वाली अरक्तता का शरीर-क्रियात्मक आधार बताइए।
प्रत्यूर्जता प्रतिक्रियाओं के नियंत्रण में इओसिनोफिल्स की भूमिका का वर्णन कीजिए।
रक्तस्तम्भन में बिम्बाणुओं की भूमिका का वर्णन कीजिए।
Model answer
Drafted with AI by UPSC Answer Check against this question's marking rubric, to the expected length. UPSC does not publish answers for Mains — this is one way to score well, not an official key. How we build rubrics and answers.
(a)(i) Facial nerve. Its functional columns are SVE, GVE, SVA and GSA, with nuclei/tracts: facial motor, superior salivatory, lacrimal, solitary tract and geniculate ganglion. SVE supplies facial expression muscles; GVE supplies lacrimal/salivary glands; SVA/GSA carry taste/external ear sensation. It enters the internal acoustic meatus, runs in the facial canal, with labyrinthine, tympanic and mastoid segments, and exits the stylomastoid foramen. Intratemporal branches are greater petrosal, nerve to stapedius and chorda tympani; after exit it gives posterior auricular, nerve to stylohyoid and nerve to digastric, and five terminal branches are temporal, zygomatic, buccal, marginal mandibular and cervical. Bell’s palsy is idiopathic LMN facial palsy, graded by House-Brackmann; unlike an UMN lesion, the forehead is not spared and the whole half of the face is weak, with loss of eye closure (Bell's phenomenon), drooling, and depending on the level, loss of taste in the anterior two-thirds of the tongue and hyperacusis. Treatment is early corticosteroids with eye care; Ramsay Hunt syndrome is a key differential.
(a)(ii) Inguinal hernia. Indirect hernia passes through the deep inguinal ring, lateral to the inferior epigastric artery, and lies within the coverings of the spermatic cord; it is usually congenital (patent processus vaginalis), common in children/young males, may present as scrotal swelling. Direct hernia protrudes through Hesselbach’s triangle, medial to the inferior epigastric artery, outside the cord coverings; it is acquired, common in older males, rarely descends into the scrotum and has a lower risk of strangulation. Both are assessed for reduction, cough impulse and Zieman’s three-finger test: impulse on the index finger over the deep ring suggests indirect, on the middle finger over the superficial ring direct, and on the ring finger over the saphenous opening femoral hernia.
(b)(i) Renal clearance. Clearance C=UV/P, where U, V and P are urine concentration, flow and plasma concentration. A gold-standard marker must be freely filtered, neither secreted nor reabsorbed, metabolically inert and non-toxic; inulin is the exogenous standard. Urea is unsuitable because it is not inert: it undergoes net tubular reabsorption, about half in some states, and varies with hydration; although some tubular secretion may occur, net reabsorption makes urea clearance underestimate GFR.
(b)(ii) RFLP. RFLP DNA fingerprinting uses restriction endonuclease digestion, gel electrophoresis, Southern blotting and probe hybridisation to detect variable-length polymorphic bands from genomic DNA. It was used in early forensic identification (Colin Pitchfork case), paternity disputes and prenatal diagnosis.
(c)(i) Anaemia. In CKD, anaemia results from EPO deficiency, iron deficiency, blood loss, shortened RBC survival and uraemic toxins suppressing marrow; Indian CKD/dialysis cohorts show high prevalence, often in a majority of patients. In liver disease, causes include bleeding (varices, coagulopathy), hypersplenism, folate deficiency and alcohol toxicity, haemolysis (spur cells) and macrocytosis from altered red-cell membrane lipids.
(c)(ii) Eosinophils. Recruited by IL-5 and eotaxin, they contain major basic protein, eosinophil cationic protein and peroxidase and kill helminths by degranulation. They limit allergic reactions by releasing histaminase (degrades histamine) and arylsulfatase (inactivates leukotrienes) and by inhibiting mast-cell degranulation; in allergic asthma, however, their granule proteins also damage airway epithelium.
(c)(iii) Platelets. Platelets adhere via vWF–GPIb, activate with ADP and thromboxane A2, expose GP IIb/IIIa, secrete dense/alpha granule contents, aggregate to form a platelet plug, and stabilise the clot by fibrin-mediated clot retraction.
How this answer will be evaluated
Framework: Medical Science, Paper 1
What earns full marks: Precise anatomical/physiological terminology, clear differentiation, and correct application of clinical concepts.
Evaluation rubric
Each sub-part is marked on its own, against the marks and word limit printed on the paper.
- (a)(i) Facial nerve: functional columns and nuclei, course and branches, Bell's palsy. 10 marks
describe— define → structure or process in order → labelled diagram → significance
Must cover
- Components SVE (motor nucleus), GVE (superior salivatory/lacrimatory), SVA (nucleus tractus solitarius), GSA (spinal trigeminal)
- Intracranial, intratemporal (meatal, labyrinthine, geniculate, tympanic, mastoid segments) and extracranial course; exits stylomastoid foramen
- Branches: greater petrosal, nerve to stapedius, chorda tympani; posterior auricular, digastric, stylohyoid; five terminal branches in parotid
- Bell's palsy: idiopathic LMN palsy — whole half of face including forehead, loss of taste, hyperacusis, Bell's phenomenon; steroids, eye care
Loses marks
- Forehead sparing in Bell's palsy
Earns more
- Topographic localisation of lesion
Extra mark
- UMN vs LMN comparison
- (a)(ii) Differentiate indirect and direct inguinal hernia. 5 marks
compare— paired headings or point-wise contrast → key differences → significance → conclusion
Must cover
- Indirect: through deep ring, lateral to inferior epigastric vessels, within the cord coverings, can reach scrotum
- Direct: through Hesselbach's triangle, medial to inferior epigastric vessels, outside the cord, rarely scrotal
- Aetiology/age: indirect congenital (patent processus vaginalis), direct acquired/elderly
- Clinical tests: deep ring occlusion, Zieman's test; strangulation risk higher in indirect
Loses marks
- Reversed relation to inferior epigastric vessels
Earns more
- Pantaloon hernia
Extra mark
- Surgical repair principles
- (b)(i) Renal clearance; features of a gold-standard marker; why urea is not. 10 marks
define— precise definition → the distinguishing feature → one example
Must cover
- C = UV/P definition
- Ideal marker: freely filtered, not reabsorbed or secreted, not metabolised, non-toxic, not protein-bound, easy to measure
- Inulin as gold standard; creatinine as practical (slight secretion)
- Urea: partly reabsorbed (varies with urine flow), so underestimates GFR
Loses marks
- Calling urea freely excreted
Earns more
- Clearance ratio interpretation
Extra mark
- eGFR equations
- (b)(ii) Role of RFLP in DNA fingerprinting. 10 marks
describe— define → structure or process in order → labelled diagram → significance
Must cover
- Restriction digestion of DNA; polymorphic fragment lengths (VNTR-based)
- Electrophoresis, Southern blotting, probe hybridisation
- Individual-specific banding pattern
- Applications: forensics, paternity, genetic mapping; replaced by STR-PCR
Loses marks
- Confusing with PCR sequencing
Earns more
- Alec Jeffreys
Extra mark
- Limitations (DNA amount, time)
- (c)(i) (i) Physiological basis of anaemia in kidney and liver disease. 5 marks
explain— definition/context → points in order → small example → short close
Must cover
- CKD: erythropoietin deficiency (main), iron deficiency, uraemic marrow suppression, shortened RBC life, blood loss
- Hepcidin excess in CKD inflammation
- Liver disease: bleeding (varices, coagulopathy), hypersplenism, folate deficiency/alcohol, haemolysis (spur cells), macrocytosis
- Normocytic normochromic pattern in CKD
Loses marks
- Only nutritional causes
Earns more
- ESA and iron therapy
Extra mark
- Hepatic TPO link to thrombocytopenia
- (c)(ii) (ii) Role of eosinophils in control of allergic reactions. 5 marks
describe— define → structure or process in order → labelled diagram → significance
Must cover
- Recruitment by IL-5, eotaxin
- Granule contents: MBP, ECP, EPO, EDN
- Modulating role: histaminase, arylsulfatase (degrades leukotrienes), inhibition of mast-cell degranulation
- Also pro-inflammatory tissue damage in asthma
Loses marks
- Only antiparasitic role
Earns more
- Anti-IL-5 therapy
Extra mark
- Eosinophilia causes
- (c)(iii) (iii) Role of platelets in haemostasis. 5 marks
describe— define → structure or process in order → labelled diagram → significance
Must cover
- Adhesion via vWF–GPIb to exposed collagen
- Activation and release (ADP, TXA₂, serotonin); shape change
- Aggregation via GPIIb/IIIa–fibrinogen; platelet plug
- Procoagulant surface (phosphatidylserine) and clot retraction; vasoconstriction
Loses marks
- No aggregation step
Earns more
- Antiplatelet drug targets
Extra mark
- Bernard–Soulier/Glanzmann
What "Describe" is asking you to do
Give a full, ordered account of the thing named — its parts, stages or mechanism — in the sequence in which it actually exists or occurs. Most describe questions come from the science optionals, where the marks sit in correct technical detail and, where the stem says so, a labelled diagram.
Structure that answers it
One-line identification of the subject → the parts or stages in their real order, each with its defining detail → labelled diagram where the subject is structural → closing line on function or significance
Where marks are lost
Loose general prose where the examiner is ticking named parts, correct terminology and their sequence; and in the General Studies papers, turning to evaluation before the description is finished.
Practice this exact question
Write your answer and it is marked point by point against the model answer above — what you covered, what you missed, what you got wrong.
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