(a) Write salient Histological Features of Basic tissues of the Body. (10 marks) (b) Location of superficial lymph nodes of ox…

(a) Histological Features of Basic Tissues

The four basic tissues exhibit distinct histological characteristics. Epithelial tissue is characterized by closely packed cells resting on a basement membrane, classified as simple (single layer) or stratified (multiple layers) and further as squamous, cuboidal, or columnar based on cell shape. Connective tissue is defined by an abundant extracellular matrix containing collagen, elastic, and reticular fibers, housing fibroblasts, macrophages, and adipocytes. Muscular tissue consists of contractile cells; skeletal and cardiac muscles are striated with sarcomere structures, while smooth muscle lacks striations and has spindle-shaped cells. Nervous tissue comprises neurons with Nissl bodies in the cytoplasm (cell body) and dendrites, supported by neuroglia cells that provide structural and metabolic support.

(b) Superficial Lymph Nodes of the Ox

Superficial lymph nodes in the ox are palpable and drain specific regions. The parotid node lies ventral to the temporomandibular joint at the caudal border of the masseter, draining the face and lips. The mandibular node is located in the intermandibular space, draining the tongue and oral cavity. The prescapular node is situated on the cranial aspect of the shoulder, draining the forelimb and thoracic wall. The prefemoral (subiliac) node is found above the stifle on the cranial border of the tensor fasciae latae, in the flank fold, draining the hindlimb. The popliteal node lies in the popliteal fossa, caudal to the stifle, between the biceps femoris and semitendinosus muscles, superficial to the gastrocnemius, draining the hock and distal hindlimb. The supramammary nodes are located dorsal to the caudal part (base) of the udder, draining the mammary gland. These nodes are critical for diagnosing systemic infections and localizing disease processes in veterinary practice.

(c) Drugs Acting on Fluid Balance

Fluid balance is regulated by diuretics, antidiuretics, and fluid replacers. Diuretics increase urine output; loop diuretics like furosemide act on the ascending loop of Henle, while thiazides act on the distal convoluted tubule. Potassium-sparing diuretics reduce sodium-potassium exchange in the collecting duct, either as aldosterone antagonists (spironolactone) or by blocking epithelial sodium channels (amiloride, triamterene), and osmotic diuretics like mannitol increase osmotic pressure in the tubule. Antidiuretics, such as desmopressin (DDAVP), mimic ADH to promote water reabsorption in the collecting ducts, treating diabetes insipidus. Fluid replacers include crystalloids like normal saline and Ringer’s lactate for volume expansion, and colloids like dextran or albumin for oncotic pressure maintenance. Hypertonic saline is used for severe hyponatremia. Sodium bicarbonate is an alkalinizing agent used to correct metabolic acidosis, distinct from balanced electrolyte solutions. Proper selection depends on the specific electrolyte deficit or excess.

(d) Types of Pollution and Water Quality

Pollution types include air, water, soil, noise, and thermal. Water pollution sources are point sources like industrial effluents and sewage, and non-point sources like agricultural runoff. Signs include algal blooms, elevated biochemical oxygen demand (BOD), and fish kills. Water quality is measured via physicochemical parameters: pH, dissolved oxygen (DO), BOD, chemical oxygen demand (COD), total dissolved solids (TDS), and heavy metals. Biological indicators include most probable number (MPN) of coliforms and plankton indices. The Water Quality Index (WQI) integrates these parameters to assess suitability for drinking or irrigation. In India, the Central Pollution Control Board (CPCB), through the National Water Quality Monitoring Programme, assesses surface and ground water against its designated-best-use criteria, while drinking water is judged against the BIS standard IS 10500:2012.

(e) Rabies Sample Collection and Dispatch

For suspected rabid dogs, brain tissue is the primary sample. Only trained staff who have received pre-exposure rabies vaccination should handle the carcass, wearing gloves, apron, face shield or goggles and a mask. If the laboratory is close, the intact head can be sent chilled (on ice, not frozen) in a leak-proof container. Otherwise, the preferred safe method is the occipital foramen route, in which a drinking straw or disposable pipette is pushed through the foramen magnum to collect brainstem, cerebellum and hippocampus without opening the skull; the skull is opened with a saw only in a necropsy room with full precautions. The brainstem is the most important part, and samples from more than one region improve sensitivity. Fresh chilled tissue, or tissue in 50% glycerol-saline when refrigeration is not available, is used for the direct fluorescent antibody test (DFA) and RT-PCR; formalin-fixed tissue (10% formalin) is suitable only for histopathology and immunohistochemistry, not for DFA. Cold chain maintenance at 2–8°C is critical during transport. Samples are packed in triple packaging: primary container, secondary container, and outer carton, with absorbent material. Dispatch follows standard triple-packaging rules for biological substances (UN 3373), accompanied by a forwarding letter detailing animal history and clinical signs.