In rabbit the melanin is contained in highly specialized stellate cells called-

Correct Answer: B

Rationale: The correct answer is B: Melanocytes. Melanocytes are the cells responsible for producing melanin, the pigment that gives color to skin, hair, and eyes. In rabbits, melanin is contained in these specialized cells, not in chromatophores (A), which are found in fish and amphibians. Melanin granules (C) are the actual pigment produced by melanocytes, not the cells themselves. Carotene granules (D) are unrelated to melanin production and are responsible for the orange color in some animals. Therefore, the correct answer is B as melanocytes are specifically responsible for producing melanin in rabbits.

Correct Answer: A

Rationale: The correct answer is A: Simple tubular. Sweat glands are classified based on their shape and structure. Simple tubular glands have a long, straight tube for secretion, which matches the structure of sweat glands. Simple alveolar glands have a rounded sac shape, not seen in sweat glands. Compound acinar glands have a branched, sac-like structure, and compound tubular glands have a branched, tube-like structure, neither of which matches the structure of sweat glands. Therefore, the correct answer is A as sweat glands are characterized by a simple tubular structure.

Correct Answer: D

Rationale: The correct answer is D: Shrew. Shrews are known to have red-colored sweat due to a pigment called porphyrin. This pigment gives their sweat a reddish hue. Kangaroos, elephants, and rhinoceroses do not have red sweat. Kangaroos sweat is colorless, elephants' sweat is clear, and rhinoceroses sweat may appear red due to mud or dust, not because of any pigment. Therefore, the red-colored sweat is unique to shrews, making choice D the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Cortex. Melanin pigment granules are found in the cortex layer of the hair shaft. This is where the color of the hair is determined. The cortex contains the majority of the hair's melanin, which gives hair its natural color. The other choices, A: Hair follicle, B: Hair papilla, and C: Medulla, do not contain melanin pigment granules. The hair follicle is the root of the hair, the hair papilla is a structure at the base of the follicle, and the medulla is the innermost layer of the hair shaft that may or may not contain pigment depending on the hair color.

Correct Answer: B

Rationale: The correct answer is B: Elasticity of dermis decreases. As people age, the dermis layer of the skin loses collagen and elastin fibers, leading to a decrease in skin elasticity, resulting in loose and wrinkled skin. The other choices are incorrect because A (Stratum germinativum becoming more active) would actually lead to increased cell turnover and potentially smoother skin, C (Stratum corneum becoming thicker) would result in thicker skin but not necessarily loose and wrinkled, and D (poor blood supply to the skin) would affect overall skin health but not directly cause loose and wrinkled skin.