Which layer of the skin contains immune cells that help protect against pathogens?

Correct Answer: A

Rationale: The epidermis contains Langerhans cells, dendritic immune cells in the stratum spinosum, which detect pathogens and initiate immune responses, aiding protection. The dermis has macrophages and mast cells, but the question emphasizes the layer with these cells as a primary feature, pointing to the epidermis's barrier role. The hypodermis (subcutaneous tissue) lacks significant immune cells. The epidermis's immune function, via Langerhans cells, makes it the correct layer.

Correct Answer: C

Rationale: The integumentary system protects against infection via the skin's barrier (stratum corneum) and immune cells (Langerhans), blocking pathogens. Blood clotting is a circulatory function, digestion is gastrointestinal, and respiration is pulmonary, none integumentary roles. Infection prevention, a core protective task, makes this the correct external factor.

Correct Answer: B

Rationale: Edema is assessed by pressing on the skin and noting how long the depression (pitting) takes to resolve. A depression resolving in 10-15 seconds corresponds to +2 edema on the pitting edema scale. The scale is: +1 (slight pitting, resolves quickly, about 0-2 mm), +2 (moderate pitting, resolves in 10-15 seconds, about 4 mm), +3 (deeper pitting, resolves in 30 seconds, about 6 mm), and +4 (very deep pitting, resolves in over 2 minutes, about 8 mm). The 10-15 second resolution time aligns directly with the +2 level, indicating moderate edema that takes a noticeable but not excessively long time to rebound, making it the correct answer.

Correct Answer: D

Rationale: The stratum basale is the deepest layer of the epidermis, located just above the dermis, where cell division occurs to replenish the skin. The stratum spinosum is above it, adding structural support. The stratum granulosum is higher, where keratinization begins, and the stratum corneum is the outermost layer of dead cells. The stratum basale's position at the base of the epidermis makes it the deepest, responsible for regenerating the layers above it, confirming it as the correct choice.

Correct Answer: A

Rationale: Sebaceous glands produce sebum, an oily substance that lubricates skin and hair, preventing dryness and aiding waterproofing. Impetigo is a bacterial infection, not a secretion. Serous refers to a watery fluid from serous glands, not sebaceous ones. 'Sirius' seems to be a typo or distractor (possibly meant 'serous'), but it's not relevant. Sebum is the specific secretion of sebaceous glands, tied to their role in skin health, making it the correct answer.