Anatomy and Physiology of Skin

Asha S

Clinical Instructor, Kauvery Hospital, Alwarpet, Chennai, Tamil Nadu

Introduction

The skin is the body’s largest organ, made of water, protein, fats and minerals. The skin protects our body from germs and regulates body temperature. Nerves in the skin helps to feel sensations like hot and cold. The skin, along with the hair, nails, oil glands and sweat glands, is part of the integumentary system. “Integumentary” means a body’s outer covering.

The Integumentary System

Functions of the skin and subcutaneous tissue

  • Epidermis and Dermis
  • Hypodermis
  • Thick and Thin Skin
  • Skin Color
  • Skin Markings
  • Hair and nails
  • Cutaneous glands
  • Skin disorders

Overview

  • Largest organ (15% of body weight)
  • Epidermis: Keratinized stratified squamous epithelium
  • Dermis: Connective tissue layer
  • Hypodermis
  • Thickness variable, normally 1-2 mm
  • Dermis May Thicken, Up To 6 Mm
  • Stratum Corneum Layer Increased
  • Calluses On Hands And Feet

Structure of the Skin

Functions of the Skin

  • Resistance to trauma and infection
  • Packed with keratin and linked by desmosomes
  • Acid mantle (ph 4-6)
  • Barrier to ultraviolet light
  • Vitamin D synthesis
  • Sensory receptors
  • Thermoreceptors through sweating
  • Nonverbal communication

Cells of the Epidermis

  • Stem cells: Undifferentiated cells in deepest layers
  • Keratinocytes – most of the skin cells
  • Melanocytes: Synthesize pigment that shield UV
  • Tactile (merkel) cells: Receptor cells associated with nerve fibers
  • Dendritic (langerhans) cells: Macrophages guard against pathogens

Cell and Layers of the Epidermis

Stratum Basale

Single layer cells on basement membrane

Cell types in this layer

  • Keratinocytes: Undergo mitosis to replace epidermis
  • Melanocytes: Distribute melanin through cell processes, Melanin picked up by keratinocytes
  • Merkel cells are touch receptors: Form merkel disc

Stratum Spinosum

  • Several layers of keratinocytes: Appear spiny due to shrinkage during histological preparation
  • Contains dendritic (Langerhans)cells
    • Macrophages from bone marrow that migrate to the epidermis
    • 800 cells/millimeter2
    • Help protect body against pathogens by “presenting” them to the immune system

Stratum Granulosum

  • 3 to 5 layers Flat keratinocytes
  • Contain keratinohyalin granules: Combine with filaments of cyto skeleton to form keratin
  • Produces lipid-filled vesicles that release a glycolipid by exocytosis to waterproof the skin
    • Forms a barrier between surface cells and deeper layers of the epidermis
    • Cuts off surface strata from nutrient supply

Stratum Lucidum

  • Thin translucent zone seen only in thick skin
  • Keratinocytes are packed with eleidin, a precursor to keratin
    • Does not stain well
  • Cells have no nucleus or organelles

Stratum Corneum

  • Up to 30 layers of dead, scaly, keratinized cells
    • Surface cells flake off (exfoliate)

Skin disorders

Skin disorders, also known as skin conditions, are medical conditions that affect the skin, nails, and related muscles and glands. Some common skin disorders include:

  • Acne: Clogged hair follicles cause pimples, whiteheads, blackheads, and sometimes cysts. Acne can leave scars or darken the skin.
  • Eczema (atopic dermatitis): A common type of skin condition that causes dry, red, itchy skin. Eczema can also lead to swelling, cracking, or scaliness.
  • Psoriasis: Itchy, scaly, red patches of skin that may swell or feel hot.
  • Vitiligo: Loss of pigmentation in the skin that can cause white patches, often in areas exposed to sunlight. People with vitiligo may also lose their hair color early.
  • Rosacea: Flushed, thick skin and pimples, usually on the face.
  • Alopecia areata: Hair loss in small patches.
  • Raynaud’s phenomenon: Reduced blood flow to the fingers, toes, or other body parts, causing numbness or skin color change.

Other skin disorders include

  • Hives, Dandruff, Insect bites, Burns, Cuts and scrapes, and Skin infections.
  • Skin disorders can be caused by a number of factors, including viral infections, bacterial infections, fungal infections, stress, allergens, climate, and certain irritants.

Care of skin

  • Skin care for patients involves keeping skin clean and moisturized, and checking for signs of injury or irritation.
  • Cleaning Wash with warm water and a gentle soap, Avoid scrubbing the skin, Clean skin immediately if it’s wet or soiled, and Use non-drying cleansers.
  • Moisturizing
  • Use a water-based moisturizer daily
  • Use a moisturizer that’s right for your skin type
  • Use a moisturizer with SPF to protect from the sun
  • Checking
  • Check skin daily for signs of pressure injuries, especially on bony areas
  • Look for redness, swelling, soreness, discoloration, or odd texture
  • Let a doctor or nurse know about any changes
  • Other tips
  • Avoid hot water, which can dry out skin
  • Avoid strong soaps and detergents, which can strip oil from the skin
  • Drink plenty of water
  • Protect skin from the sun with sunscreen and protective clothing
  • Avoid tanning beds and sunlamps
  • Reduce stress and get enough sleep
  • Treat minor cuts, scrapes, and burns

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