Integumentary System Overview

Integumentary System Overview

• The integumentary system is a body system.
• It consists of the skin, sweat/oil glands, hair, and nails.

Skin and Hypodermis

• Skin is the largest organ in the human body.
• It constitutes 7% of body weight.
• Thickness ranges from 1.5 to 4.4 mm.
• Skin is divided into two layers: epidermis and dermis.
• Hypodermis lies beneath the dermis.

Skin Structure

• Key structures in the skin:
  • Hair shaft
  • Epidermis (papillary layer)
  • Dermis (reticular layer)
  • Hypodermis
  • Dermal papillae
  • Subpapillary vascular plexus
  • Pore
  • Appendages of skin (e.g., sweat glands, hair follicles)
  • Nerve endings (e.g., Meissner corpuscles, Pacinian corpuscles)
  • Sensory nerve fibers (root hair plexus)
  • Lamellar (Pacinian) corpuscle
  • Hair follicle receptor (root hair plexus)

Functions of Skin and Hypodermis

• Cushions and insulates deeper organs.
• Protects the body from bumps, scrapes, and cuts.
• Protects the body from chemicals, heat, and cold.
• Acts as a mini-excretory system.
• Produces vitamin D.
• Contains sensory receptors associated with nerve endings.

Epidermis

• Contains four cell types: keratinocytes, melanocytes, tactile epithelial cells, and dendritic cells.
• Keratinocytes are most abundant.
• They arise from the deepest layer of the epidermis.
• They produce keratin (a tough protein).
• They also produce antibodies and enzymes.
• Keratinocytes are dead at the skin's surface.

Layers of Epidermis

• Stratum basale (stratum germinativum): deepest layer, cells actively divide.
• Stratum spinosum (spiny layer): "spiny" appearance from histological preparation, contains keratinocytes and star-shaped dendritic cells.
• Stratum granulosum: consists of keratinocytes, contains keratohyaline granules (help form keratin) and lamellar granules (waterproof glycolipid).
• Stratum lucidum: only found in thick skin, composed of flat, dead keratinocytes.
• Stratum corneum: thick layer of dead keratinocytes and thickened plasma membranes; protects skin against abrasion.

Dermis

• Second major layer of the skin.
• Composed of strong, flexible connective tissue.
• Richly supplied with blood vessels and nerves.
• Two layers: papillary layer (includes dermal papillae) and reticular layer (deeper, 80% of dermis thickness).

Skin Lines and Ridges

• Friction ridges on fingertips, palms
• Cleavage lines in reticular dermis
• Flexion creases

Hypodermis

• Deep to the skin; also called superficial fascia.
• Composed of areolar and adipose connective tissues.
• Anchors skin to underlying structures.
• Helps insulate the body.

Skin Color

• Three pigments contribute to skin color: melanin (most important), carotene, and hemoglobin.
• Melanin is a pigment.
• Carotene is a yellowish pigment from carrots and tomatoes.
• Hemoglobin gives blood its color.
• The amount of melanin in skin affects skin color. Less melanin allows more crimson blood color to show through.

This quiz explores the integumentary system, focusing on the structure and functions of the skin, sweat glands, hair, and nails. It includes details on skin layers, key structures, and protective roles. Test your knowledge of this vital body system!