Capillaries are the smallest blood vessels in the body, connecting arteries to veins. There are approximately 40 billion capillaries in the average human body. Capillaries are extremely thin, measuring approximately 5 micrometers in diameter
Skin is the largest organ, comprising 15% of adult body weight. Contains three main layers: epidermis, dermis, and subcutaneous layer. Thickest skin found on back, palms, and soles (up to 3mm). Thinnest skin located on eyelid (0.05mm)
Capillaries are smallest blood vessels connecting arterioles to venules. Diameter ranges from 3 to 40 micrometers. Composed of epithelial cells and basal lamina (tunica intima). Controlled by precapillary sphincters and pericyte layer
Flow rate (Q) is volume passing through area in time (Q = V/t). SI unit is m³/s, common units include liters (L). Flow rate depends on both velocity and cross-sectional area
Loose connective tissue contains thin collagen fibers with semi-fluid matrix. Ground substance occupies more volume than fibers. Functions in oxygen and nutrient diffusion through capillaries. Most cells are transient wandering cells from blood vessels
Actinic keratosis is a precancerous scaly lesion on sun-damaged skin. Most commonly found on bald scalp, ear, face or back of hand. Multiple lesions often present with white or yellow scaly surface