Veterinary Cytology & General Histology: Epithelial, Connective, Muscular & Nervous Tissues - Veterinary Science | Agrigyan

Statement (I) is true: keratinocytes receive melanosomes from melanocytes via cytocrine phagocytosis and store them over their nuclei to protect DNA from UV radiation. Statement (II) is false: melanin is produced by melanocytes (using tyrosinase in melanosomes), NOT by keratinocytes.

All statements (A, B, C, and D) are accurate characteristics of mast cells: they reside abundantly in loose connective tissue around blood vessels, contain prominent basophilic cytoplasmic granules that exhibit metachromasia (staining purple-red with toluidine blue), and store chemical mediators such as histamine, heparin, serotonin, and neutral proteases.

Plicae circulares (valves of Kerckring) are large, permanent circular folds of the intestinal mucosa and submucosa that project into the lumen to increase surface area. They are well-developed and permanent in ruminants, whereas in horses they are less prominent and in carnivores (dog) they are absent or temporary.

In the visceral layer of Bowman's capsule, podocyte secondary processes (pedicels) interdigitate around glomerular capillaries, leaving narrow intercellular clefts called filtration slits (slit pores) of about 25–30 nm width, which are bridged by a thin slit diaphragm.