Anatomy Bones and Muscles · MU Pleven

195. Skin – structure. Hairs and nails.

Covers the skin as the body's largest organ and its three layers: epidermis, dermis and hypodermis. It then goes through the epidermal cell types and strata, the dermal composition, the skin glands including sweat and mammary types, the structure of the hair and follicle, and the parts of the nail.

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

Topic 194 of 236 in the MU Pleven syllabus for Anatomy Bones and Muscles (Medicine, Year 2). The free AceMed note covers it in 7 sections, about 1,156 words (8 min of reading), with 10 flashcards.

In this note

  1. Introduction
  2. S K I N
  3. Epidermis :
  4. Dermis
  5. Skin Glands :
  6. Hair :
  7. Nails :

Introduction

228 + 229

S K I N

  • The skin is the largest organ (in both surface area & weight !), that covers and protects the external surface of the body.
  • Is composed 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 flattened, clear dead keratinocytes.

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