(a) Describe the anatomy of uterus under the following headings: (i) Gross features (ii) Relations of uterus (iii) Ligaments and supports (iv) Blood supply (v) Lymphatic drainage (vi) Applied aspects (15 marks)
(b) Discuss the physiological mechanism

Question

(a) Describe the anatomy of uterus under the following headings: (i) Gross features (ii) Relations of uterus (iii) Ligaments and supports (iv) Blood supply (v) Lymphatic drainage (vi) Applied aspects (15 marks)
(b) Discuss the physiological mechanism of short-term and long-term regulation of arterial blood pressure. (15 marks)
(c) (i) Explain the process of initiation of protein synthesis in eukaryotes. Enumerate any four inhibitors of protein synthesis with their mechanism of action. (6+4=10 marks)
(ii) Explain the principle and applications of radioimmunoassay. (10 marks)

UPSC Answer Check · Accepted Answer

Uterus. The uterus is a thick-walled, pear-shaped muscular organ, about 7.5 cm long, 5 cm wide and 2.5 cm thick, with fundus, body and cervix. It lies in the pelvis between bladder and rectum, anteverted and anteflexed. Peritoneum covers fundus and anterior body, forming the vesicouterine pouch; posteriorly it forms the rectouterine pouch of Douglas. The cervix is partly extraperitoneal and enters the vagina. Its supports are the broad ligament, round ligament, cardinal ligament, uterosacral ligament and pubocervical ligament; the ovarian ligament attaches ovary to uterus but is not a principal support. The uterine artery, a branch of the internal iliac artery, runs in the cardinal ligament and anastomoses with the ovarian artery; venous drainage is through the uterine plexus to internal iliac veins. Lymphatics from the fundus and body drain mainly to external iliac and para-aortic nodes, while those from the cervix drain to internal iliac and sacral nodes. Applied anatomy includes pelvic organ prolapse when cardinal, uterosacral and pubocervical supports fail; hysterectomy requires knowledge of the uterine artery, cardinal ligament and ureter; the pouches collect ascites or haemoperitoneum, and cervical lymphatics guide cancer staging. Estrogen and progesterone regulate uterine growth and secretory changes.

Blood pressure. Short-term regulation is neural. Baroreceptors in the carotid sinus and aortic arch sense stretch; rising pressure increases afferent firing through the glossopharyngeal and vagus nerves to the nucleus tractus solitarius. This increases vagal outflow and reduces sympathetic outflow, lowering heart rate, contractility and total peripheral resistance. Chemoreceptors in the carotid and aortic bodies respond to hypoxia, hypercapnia and acidosis, raising sympathetic tone. In severe hypotension, the central ischemic response causes powerful medullary vasoconstriction. Long-term regulation is renal and humoral, especially the renal-body fluid mechanism. High pressure increases glomerular filtration and natriuresis, reducing extracellular volume; low pressure conserves sodium and water. The renin-angiotensin-aldosterone system is activated by low renal perfusion, sympathetic stimulation or low sodium: renin converts angiotensinogen to angiotensin I, ACE forms angiotensin II, which constricts vessels, stimulates aldosterone, thirst and ADH release. ADH increases water reabsorption. Atrial natriuretic peptide and brain natriuretic peptide oppose this by promoting natriuresis and vasodilation. Capillary fluid shifts also buffer volume changes, as excess interstitial fluid is returned to plasma over time.

Protein synthesis. Eukaryotic initiation begins when the 40S ribosomal subunit, with initiator methionyl-tRNA, eIF2-GTP, eIF1, eIF1A and eIF3, forms the 43S pre-initiation complex. eIF4F (eIF4E, eIF4G, eIF4A) binds the 5′ cap and recruits the 43S complex to mRNA. The complex scans to the first AUG, where start-codon recognition triggers GTP hydrolysis by eIF2, mediated by eIF5, and release of initiation factors. eIF5B then promotes joining of the 60S subunit to form the 80S initiation complex. Elongation then begins. Inhibitors include tetracycline, which blocks aminoacyl-tRNA binding at the 30S site; chloramphenicol, which inhibits 50S peptidyl transferase; erythromycin, which blocks translocation by binding the 50S exit tunnel; and puromycin, which mimics aminoacyl-tRNA and causes premature chain termination. Clinically, such inhibitors are used as antibiotics.

Radioimmunoassay. Radioimmunoassay is a competitive binding assay. A fixed amount of antibody is incubated with a known amount of radiolabeled antigen and a sample containing unlabeled antigen. The two antigens compete for the same antibody-binding sites; as the concentration of unlabeled antigen rises, the proportion of radiolabeled antigen bound falls. Bound radioactivity is measured and compared with a standard curve to quantify the sample. The method is highly sensitive, often detecting picogram per millilitre levels. It is used in Indian diagnostic laboratories for thyroid hormones T3 and T4, insulin, cortisol, hCG in pregnancy, therapeutic drug levels, and tumor markers such as PSA and AFP. Thus, anatomy, homeostasis, molecular biology and immunoassay diagnostics interconnect clinically.

(a) Describe the anatomy of uterus under the following headings: (i) Gross features (ii) Relations of uterus (iii) Ligaments and…

Model answer

What "Describe" is asking you to do

Structure that answers it

Where marks are lost

How this answer will be evaluated

Approach

Key points expected

Evaluation rubric

Must cover

Loses marks

Earns more

Extra mark

Must cover

Loses marks

Earns more

Extra mark

Must cover

Loses marks

Earns more

Extra mark

Must cover

Loses marks

Earns more

Extra mark

Practice this exact question

More from Medical Science 2022 Paper I