Anatomy · MU Sofia

PNS · 227.228 Skin. Epidermis and dermis. Glands

Covers the skin as the body's largest organ and its three layers: epidermis with its cell types and five strata, including the stratum lucidum in thick skin, then the dermis with its papillary and reticular parts. Goes on to the skin glands (sebaceous, ceruminous, eccrine, apocrine and mammary), the structure of hair and follicle, and the parts of the nail apparatus.

Inside: 7 sections · 6 labelled pictures · 10 flashcards · 8 min

Topic 207 of 264 in the MU Sofia syllabus for Anatomy (Dental Medicine, Year 2). The free AceMed note covers it in 7 sections, about 1,160 words (8 min of reading), with 10 flashcards.

In this note

  1. Introduction
  2. SKIN
  3. Epidermis :
  4. Dermis
  5. Skin Glands :
  6. Hair :
  7. Nails :

Introduction

228 + 229

SKIN

  • The skin is the largest organ (in both surface area & weight !), that covers and protects the external surface of the body.
  • Is compised of 3 layers :
  • Epidermis
  • dermis
  • Hypodermis = subcutaneous layer.

* In adults the weight of the skin 4.5-5 Kg. about 16% of total body weight.

Epidermis :

  • Is the outermost layer of the skin

▶ Cell types:

The epidermis contains several types of cells :

  • Keratinocytes: The most abundant cells in the epidermis, responsible for producing the protein keratin, which provides structural support and waterproofing.
  • Melanocytes: Specialized cells that produce the pigment melanin, which helps protect the skin from UV radiation and determines skin color.
  • Langerhans cells: Immune cells that patrol the epidermis, helping to identify and fight off pathogens and foreign substances.
  • Merkel cells: Touch receptors involved in the sensation of light touch.

▶ Layers : The epidermis is organized into several layers.

  1. 1 Stratum basale (basal layer): The deepest layer where new keratinocytes are produced through cell division.
  2. 2 Stratum spinosum (spinous layer): The layer where keratinocytes begin to flatten and develop spiny projections.
  3. 3 Stratum granulosum (granular layer): The layer where keratinocytes produce keratin and undergo changes in structure.
  4. 4 Stratum corneum (cornified layer): The outermost layer composed of dead keratinocytes (corneocytes) that are continuously shed from the surface of the skin.

→ In thick skin in fingertips, palms, & soles the is an additional layer :

  • Stratum Lucidum (clear layer)
  • ↳ consists of 3-5 layers of flatend, clear dead keratinocytes.

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