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Section VII: Integumentary

Anatomy

Skin

The most superficial, and thinnest, layer of skin is the epidermis, which lies on top of the dermis. The dermis is thicker than the epidermis and contains many glands and nerve endings. Below the dermis is subcutaneous tissue, which is the thickest layer and is composed primarily of fat. Collectively, the skin functions to provide protection from the outside world, regulate temperature, provide tactile input, absorb ultraviolet radiation, and metabolize vitamin D. Skin is also a major component of appearance.

Complete skin section.

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TABLE 7.1Types of Cells and Location in Skin
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TABLE 7.1 Types of Cells and Location in Skin
Layer of Skin Cell Type Function
Epidermis Keratinocytes (squamous cells) Synthesis of keratin
  Melanocytes Synthesis of melanin
  Langerhan's cells Immune response
  Basal cells Epidermal production
  Eccrine unit Thermoregulation by perspiration
  Apocrine unit Sweat production
  Hair follicle Protection
  Nails Protection
  Sebaceous glands Produces sebum (oil for lubrication of skin)
Dermis Fibroblasts Collagen synthesis
  Collagen Insoluble connective tissue protein
  Elastin Primary protein in elastic tissue
  Macrophages Phagocytosis; initiate growth and repair through growth factor production
  Mast cells Provide histamine for vasodilation
  Lymphatic glands Removal of microbes and interstitial waste
  Blood vessels Thermoregulation; provides metabolic skin requirements
  Nerve fibers Sensory perception
Subcutaneous tissue Adipose Protection from trauma, energy storage, thermoregulation

Wound Healing

Normal wound healing.

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TABLE 7.2Stages of Wound Healing
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TABLE 7.2 Stages of Wound Healing
Stage of Healing (time after injury) Major Cellular Component Description
Hemostasis (0–2 days) Platelets Platelets are the first cells to arrive at the site of injury. They attach to exposed collagen at the area of injury and release chemicals that attract more platelets, ultimately forming a platelet plug to temporarily stop bleeding. Platelets are also vital to the healing process because of the growth factors they release.
Inflammation (4–6 days) Leukocytes White blood cells arrive at the wound site in response to the coagulation cascade. Leukocytes are divided into granulocytes and monocytes. Granulocytes are more abundant, and include neutrophils, basophils, and eosinophils, with neutrophils being the most common of the three. Neutrophils arrive first and are phagocytic, as are eosinophils. They are only necessary for wound healing in the presence of infection. Basophils release histamine, which increases the vascular permeability at the wound site. The most important inflammatory cells are the macrophages, which are monocytes. Macrophages are also phagocytic, but unlike neutrophils their presence is crucial to wound healing in all wounds. In addition to phagocytosis, the macrophages play a critical role in stimulating the proliferative phase of healing.
Proliferation ...

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