BIOL 1050H Lecture Notes - Lecture 3: Stratum Granulosum, Stratum Spinosum, Tactile Corpuscle
Integumentary system
Functions of the integumentary system
• 1) Thermoregulation (vasoconstriction/vasodilation, fat of
hypodermis)
• 2) Vitamin D synthesis (UVB)
• 3) Protection from abrasion, infection (epidermis)
• 4) Barrier to damage from UV (melanin), chemicals (but permeable to
some, lead, pesticides; topical medication)
• 5) Non-verbal communication (blushing, facial expression, apocrine
sweat glands)
• 6) Sensation – touch receptor (tactile corpuscle); pressure receptor
(lamellar (pacinian) corpuscle)
Integument Layers
1. Epidermis
2. Dermis
3. Hypodermis
Cell types in epidermis
• Stem cells – produce keratinocytes
• Keratinocytes – dominant cell type making up bulk of epidermis. Become
more flattened near the superficial
surface
• Dendritic cells – immune cells. In
stratum spinosum and stratum
granulosum
• Tactile/merkel cells – stratum basale
• Melanocytes – produce melanin, releasing bits of it that are
phagocytized by keratinocytes.
Melanin granules shield DNA from UV
Damage
Life cycle of keratinocytes
• 30-40 days (accelerated with mechanical stress and injury)
• Calluses, corns –thickening corneum, response to mechanical
Stress
