Detailed Notes on Dermis and Hypodermis

Dermis

• The dermis is connective tissue located deep to the epidermis.
• It is vascular, providing nutrition to the avascular epidermis.
• Contains flexible proteins:
  • Elastin: Provides elasticity.
  • Collagen: Provides strength.
• Leather products (shoes, furniture, belts) are made from the dermis of animals after the epidermis is scraped away.
• Thickness: Up to 3 mm.
• Elastic fibers are made of elastin.
• Elastic fibers give elasticity to the skin, allowing it to stretch and return to its original shape.
• Fibroblasts are cells needed to make these fibers.
• Skin accessories (hair follicles, glands) are found in the dermis.
• Dermal papillae:
  • Finger-like projections extending into the epidermis.
  • Provide nutritive support to the epidermis.
  • The source of ridges on fingerprints.

Layers of the Dermis

• Papillary Layer:

  • The upper layer of the dermis.
  • Contains dermal papillae that project into the epidermis.

• Reticular Layer:

  • The deepest and thickest layer of the dermis.
  • Appears complex and maze-like due to the presence of glands, receptors, blood vessels, and fibers.
  • Contains hair follicles and shafts, oil and sweat glands, nerves, and blood vessels.

Microscopic Appearance

• Epidermis typically stains purple, while the dermis appears pinkish.
• The dermal papillae of the papillary layer extend into the epidermis to provide nutrition.
• The reticular layer constitutes the majority of the dermis and contains various structures.

Hypodermis

• Located deep to the skin and is not part of the skin itself.

• Also known as the subcutaneous layer or tissue or superficial fascia.

• Composed of adipose tissue (fat cells/adipocytes), which is a connective tissue.

• Functions:

  • Energy storage
  • Thermo-insulation: Helps to avoid heat loss.

• Overweight individuals may struggle with overheating due to increased thermal insulation from subcutaneous fat.