Definition: The dermis contains dense irregular connective tissue, housing blood vessels, nerves, and glands.

Highlight: Lines of cleavage in the reticular layer are crucial for surgical procedures, with incisions made parallel to these lines for optimal healing.

Example: During exercise, blood vessels in the dermis dilate, causing skin redness as part of temperature regulation.

Vocabulary: Decubitus ulcers, commonly known as bed sores, develop when blood flow to an area is restricted for extended periods.

Definition: Hair and nails consist of hard keratin and serve multiple protective functions.

Vocabulary: Sebaceous glands are holocrine glands that produce sebum, an oily substance that lubricates skin and hair.

Highlight: Sweat glands come in two types: eccrine (producing mostly water and salts) and apocrine $producing protein-rich sweat in specific areas$.

Example: Body odor primarily originates from apocrine gland secretions in the armpits and genital areas.

Definition: The nail matrix contains highly keratinized cells that form the nail body.

Vocabulary: The eponychium (cuticle) creates a protective seal to prevent infection of the nail bed.

Highlight: The lunula appears white due to its thickness, which obscures underlying blood vessels.

Example: The nail body grows continuously from the matrix, pushing forward over the nail bed.

Definition: The stratum corneum is the outermost layer consisting of 20-30 layers of dead, keratinized cells that are regularly shed.

Vocabulary: Keratinization refers to the process where cells fill with keratin protein, creating a tough protective barrier.

Highlight: Melanocytes in the stratum basale produce melanin, which is crucial for UV protection and preventing skin cancer development.

Example: Three main types of skin cancer can develop from UV damage: melanoma, basal cell carcinoma, and squamous cell carcinoma.