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The Integumentary System: Structure, Functions, and Response to Injury, Slides of Immunology

An in-depth exploration of the integumentary system, the largest organ in the human body. It covers the main structural features of the skin, the mechanisms that produce hair and nails, and the skin's response to injury. The document also discusses the functions of the integument, including protection, temperature regulation, and excretion, as well as the roles of the epidermis, dermis, and subcutaneous layer. Additionally, it explains the production of melanin and its impact on skin color.

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2021/2022

Uploaded on 09/27/2022

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The Integumentary System
Objectives
Describe the main structural features of the skin.
Explain the mechanisms that produce hair and nails.
Describe how skin responds to injury.
The integumentary system or integument is the largest system of the body.
- 16% of body weight
- 1.5 to 2 square meters in area
The integument is made up of 2 parts:
1. the cutaneous membrane, or skin,
2. the accessory structures
The cutaneous membrane is made up of 2 parts:
1. the outer epidermis or superficial epithelium (epithelial tissues) and
2. the inner dermis, composed of connective tissues
The accessory structures include hair, nails, and multicellular exocrine glands. These
structures generally originate in the dermis and extend through the epidermis to the skin’s
surface
Below the dermis is a subcutaneous layer of loose connective tissue, also known as the
superficial fascia or hypodermis (where hypodermic injections are administered). This is
not officially a component of the integument
The functions of skin and its subcutaneous layer include:
1. Protection against, abrasion, fluid loss and infection
2. Excretion of salts, water, and organic wastes by glands
3. Maintenance of body temperature by insulation (heating) and sweat
evaporation (cooling)
4. Synthesis of vitamin
5. Storage of lipids
6. Detection of touch, pressure, pain and temperature
The Epidermis
The most abundant cells in the epidermis are the keratinocytes (so called because they
contain large amounts of the protein keratin).
Most of the body is covered by thin skin, which has only 4 layers of keratinocytes in the
epidermis.
The palms of the hands and soles of the feet are covered with thick skin, which has 5
layers of keratinocytes in its epidermis.
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The Integumentary System

Objectives

  • Describe the main structural features of the skin.
  • Explain the mechanisms that produce hair and nails.
  • Describe how skin responds to injury. The integumentary system or integument is the largest system of the body.
  • 16% of body weight
  • 1.5 to 2 square meters in area The integument is made up of 2 parts:
  1. the cutaneous membrane, or skin,
  2. the accessory structures The cutaneous membrane is made up of 2 parts:
  3. the outer epidermis or superficial epithelium (epithelial tissues) and
  4. the inner dermis, composed of connective tissues The accessory structures include hair, nails, and multicellular exocrine glands. These structures generally originate in the dermis and extend through the epidermis to the skin’s surface Below the dermis is a subcutaneous layer of loose connective tissue, also known as the superficial fascia or hypodermis (where hypodermic injections are administered). This is not officially a component of the integument The functions of skin and its subcutaneous layer include:
  5. Protection against, abrasion, fluid loss and infection
  6. Excretion of salts, water, and organic wastes by glands
  7. Maintenance of body temperature by insulation (heating) and sweat evaporation (cooling)
  8. Synthesis of vitamin
  9. Storage of lipids
  10. Detection of touch, pressure, pain and temperature The Epidermis The most abundant cells in the epidermis are the keratinocytes (so called because they contain large amounts of the protein keratin). Most of the body is covered by thin skin, which has only 4 layers of keratinocytes in the epidermis. The palms of the hands and soles of the feet are covered with thick skin, which has 5 layers of keratinocytes in its epidermis.

Skin color depends on:

  1. pigment - carotene and melanin.
  2. circulation Carotene, an orange-yellow pigment found in carrots and other orange vegetables, accumulates in epidermal cells and in fatty tissues of the dermis. Carotene can be converted to vitamin A. Melanin, a yellow-brown or black pigment, is produced by melanocytes
  • Skin color depends on the rate of melanin production, not the number of melanocytes.
  • Melanin protects the skin from the damaging effects of ultraviolet radiation (DNA mutations and burns, which lead to cancer and wrinkles). Capillaries in the skin, carrying oxygenated red blood, contribute to skin color.
  • When blood vessels dilate from heat, skin turns red.
  • When blood flow decreases, skin pales.
  • Severe reduction in blood flow or oxygenation can give skin a bluish tint called cyanosis. Several diseases can produce changes in skin color:
  • Jaundice, a yellow color resulting from buildup of bile from the liver.
  • Diseases of the pituitary gland that cause skin darkening.
  • Vitiglio, a loss of color (melanocytes). The Dermis The dermis, located between the epidermis and the subcutaneous layer, has 2 components, the outer papillary layer and the deeper reticular layer. The papillary layer:
  • consists of areolar tissue
  • contains smaller capillaries, lymphatics and sensory neurons
  • has dermal papillae projecting between epidermal ridges The reticular layer:
  • consists of dense irregular connective tissue
  • contains larger blood vessels, lymph vessels and nerve fibers
  • contains collagen and elastic fibers
  • contains connective tissue proper The Subcutaneous Layer Below the integument, the subcutaneous layer or hypodermis stabilizes the position of the skin but allows separate movement. Not truly part of integument. The subcutaneous layer is made of elastic areolar and adipose tissues, connected to the reticular layer of the integument by interwoven connective tissue fibers.

Other integumentary glands include:

  • mammary glands, which produce milk, and
  • ceruminous glands, which protect the eardrum by producing cerumen or earwax. Nails
  • Nails are dead cells packed with keratin.
  • Production occurs in a deep epidermal fold near the bone called the nail root. The Response of the Integument to Injury Repair of Localized Injuries to the Skin Because skin has so many active germinative cells, it responds rapidly to changes in health, activity or injuries. There are 4 steps in the regeneration of localized skin injuries. Step 1: Bleeding occurs. Mast cells trigger an inflammatory response. Step 2: Blood clots form a scab that stabilizes and protects the area. Germinative cells migrate around the wound. Macrophages clean the area. Fibroblasts move in and divide, along with endothelial cells of damaged blood vessels, producing granulation tissue. Step 3: Over time, fibroblasts replace damaged tissues with a fibrous repair called scar tissue. Inflammation decreases and the clot begins to disintegrate. Step 4: Fibroblasts continue to strengthen the area until a raised section of scar tissue called a keloid forms. Burns A method of estimating the percentage of integument damaged by burns is the “rule of nines,” which divides the surface area of the adult body into multiples of nine.