Dermis

Dermis Overview

• The dermis is composed of dense collagenous connective tissue, containing:

  • Fibroblasts

  • Adipocytes

  • Macrophages

• Structures in the dermis include:

  • Nerves

  • Hair Follicles

  • Smooth Muscles

  • Glands

  • Lymphatic Vessels

Key Components

• Collagen and Elastic Fibers: Provide strength and resist stretch.

  • Collagen fibers are oriented in different directions, leading to cleavage lines (tension lines) in the skin.

  • Surgical Importance: Incisions parallel to cleavage lines gap less and produce less scar tissue.

• Stretch Marks: Occur when skin is overstretched (e.g., during pregnancy or rapid muscle growth).

Dermal Papillae

• Projections in the upper dermis extending towards the epidermis.

  • Function:

    • Supply epidermis with nutrients

    • Remove waste products

    • Help regulate body temperature

• Arranged in parallel, curving ridges; create Friction Ridges.

  • Responsible for fingerprints and footprints.

  • Increase friction, improving grip.

Injections

• Different injection types deliver substances at varying skin depths:

  1. Intradermal Injection: Slow delivery (e.g., tuberculin skin test)

     • Skin is drawn taut, and a shallow angle needle is used.

  2. Subcutaneous Injection: Moderate speed (e.g., insulin injection)

     • Skin is pinched, and a short needle is inserted into adipose tissue.

  3. Intramuscular Injection: Fast delivery (e.g., vaccines, antibiotics)

     • Long needle at a 90-degree angle into a muscle deep to the subcutaneous tissue.