Dermis and Hypodermis

dermal cells

What cell type of the dermis?

• Connective tissue

  • Collagen and elastin fibers

  • Protect deeper structures

  • Strong foundation for accessory structures

fibroblasts

What cell type of the dermis?

• Most numerous 

• Form collagen and elastin

immune cells

What cell type of the dermis?

• Fight infection

collagen and elastin network

• Provide protection and support

• Strong, dense, flexible connective tissue

• Protection of deep structures

• Support of dermal structures

  • Neurovasculature

  • Accessory structures - fibroblasts, immune cells, sweat glands in meshwork

pilosebaceous apparatus

What accessory structure of the dermis?

• Functions in thermoregulation

• Consists of

  • Hair

  • Sebaceous (oil) glands

sudoriferous (sweat) glands

What accessory structure of the dermis?

• Functions in thermoregulation

• Also excretes wastes

capillary loops

What accessory structure of the dermis?

• Functions in thermoregulation

• In dermal papillae

  • Brings blood as close to surface of body as it can get so it can interact with the surrounding air temperatures

convection

Hair prevents what form of heat exchange

sensory perception

What is the function of all of these?

• Merkel complex

• Free nerve endings

• Meissner corpuscles

  • Encapsulated tactile nerve endings

    • Good at picking up vibrations -> feeling texture due to these

• Hair follicle receptor

  • Change in hair orientation

papillary region

What region of the dermis?

• Thin, fine collagen/elastin

• Irregular arrangement

• Papillae

  • Project into epidermis

  • Taller, denser packed in:

    • Highly sensitive skin

    • Areas with more mechanical stress

    • Hands and feet

• Increase area of contact with epidermis

  • Strengthens integument - especially against shearing forces

    • Strengthens junction between dermis and epidermis

papillary region

What region of the dermis?

• Vascular communication

  • To carry nutrients to stratum basale of epidermis

• Neurovasculature

  • 1. Capillary loops

    • Feed stratum basale

  • 2. Meissner corpuscles

    • Encapsulated tactile nerve endings

  • 3. Free nerve endings

    • Pain

    • Changes in temperature

    • Itching/tickling sensations

dermatoglyphics

• What: patterns formed by epidermal ridges

  • i.e.: fingerprints

  • Typically patterned in arches, loops and whorls

  • Unique to individuals

    • Develop ~3 months in utero

    • Do not change pattern

• How are dermal papillae involved?

  • Influence pattern

  • Ridges line up with papillae

• Functions

  • 1. Tightly bond dermis and epidermis

  • 2. Friction enhancement 

    • Increased surface area increases friction for pliable surfaces

    • Common in climbing mammals

  • 3. Tactile enhancement

    • Ridges act as levers

    • Activate Meissner corpuscles

reticular region

• meaning = net like

  • Network of thick collagen and coarse elastin fibers

  • Support accessory appendages

• Tension lines

  • Most collagen and elastin fibers run parallel to local forces

  • Varies by region

  • Local forces from:

    • Bony projections, muscle orientations, and joint movements

  • Clinical correlation:

    • Incision and suturing

      • Incision parallel to lines -> fine scar

      • Incision perpendicular to lines -> gaping

hypodermis

Dermis or hypodermis?

• Functions

  • 1. Loose binding tissue

    • Deep tissues bound to superficial tissues

    • Superficial tissues can move freely

  • 2. Shock absorption

    • Esp. in hands and feet (because of large amount of fat)

  • 3. Energy storage 

    • Adipose

  • 4. Insulation

    • Slow heat loss

hypodermis

Dermis or hypodermis?

• What: connective tissue layer

  • Composition varies by region

    • Thin/loose

    • Thick/fibrous

  • Houses:

    • Adipose

    • Large vessels

      • Supply and drain skin

    • Pacinian corpuscles - (type of tactile nerve ending)

      • Pressure receptors