Melanin ⮴ Protects against UV
• Thermoregulation ʹ (Varying blood flow ⮴Allows heat Conservation or Evaporative Cooling) •
Sensory organ
Basic Structure of Normal Skin:
- 3 Layers:
o Epidermis (Top Cellular Layer):
③ Keratinocytes
③ Melanocytes
③ The 5 Layers of the Epidermis:
ξ 1. Stratum Germinativum/Basale:
o Single layer of cuboidal/columnar cells
ξ 2. Stratum Spinosum (Prickle Cell layer):
o Several layers of polyhedral cells
ξ 3. Stratum Granulosum:
o 3-5 layers flattened cells
ξ 4. Stratum Lucidum:
o (Present only on very thick layers of epidermis (Eg. Glabrous Skin
[palms/feet]))
o = The Lucid layer of Flattened Cells before Stratum Corneum.
ξ 5. Stratum Corneum:
o 5-50 layers of Flattened, Dead Cells (Squames)
o Protective Barrier; Holds in Moisture
o Cytoplasm is filled with keratin & keratohyalin granules
o Dermis (Middle Fibrous Layer):
③ Connective Tissue
③ Blood Vessels
③ Nerves (Sensory Receptors & Free Nerve Endings)
③ Hair Follicles + Arrector Pili (the Smooth Muscle)
ξ NB: Skin without hair ʹ (Eg. Palms & Soles) = “Glabrous Skin”.
ξ NB: Skin With Hair ʹ (Ie. Rest of the body) = “Non-Glabrous Skin”.
③ Glands (Sweat, Sebaceous)
③ Contains Some Cells:
ξ Fibroblasts: Synthesis and degradation of connective tissue
ξ Histiocytes/Macrophages: Phagocytic cells
ξ Mast cells: Secretory cells ⮴Vasoactive Mediators (histamine) ⮴ Skin Allergies.
ξ Lymphocytes: Small number collect around blood vessels in normal skin
③ 2 Layers:
ξ (R) - Reticular Layer (thick Collagen, lower layer) - much stronger
ξ (P) - Papillary layer (fine Collagen, upper layer) - weaker
, o Hypodermis (Fat Layer):
③ Adipose Tissue
③ Functions:
ξ Insulates the body
ξ Stores Energy
- Glands:
o Sebaceous (Sebum) Glands:
③ Associated with hair follicles (The Pilosebaceous Unit)
ξ (:. Not found on Palms/Soles)(Most found on Face & Scalp)
③ Holocrine Secretion:
ξ (Ie. Secretion via complete destruction of cells)
ξ Produce oily sebum:
③ Stimulated by Androgens:
ξ Very Active at puberty
o Eccrine (Sweat) Glands:
③ On most of the body (Scarce on the back)
③ Simple, Coiled Tubular Glands:
ξ Secretory Coil (deep in Dermis) ʹ Secrete the Water & Electrolytes
ξ Sweat Duct ʹ Reabsorb Na+ Ions from the sweat.
③ Clear watery secretion
ξ Person can perspire several liters per hour
③ Stimulated by High Temperature and Stress
o Apocrine (Pheromone) Glands:
③ Associated with hair follicles
③ Large complex gland:
ξ Located in Dermis
ξ Duct Opens into Hair Follicle.
③ Viscous, Milky Secretion ʹ (protein and cellular debris):
ξ Produces pheromones
o Bacterial action is required for odor production
③ Stimulated by Androgens:
ξ Most Active at puberty
Causes of Skin Injury:
- Physical Agents:
o Mechanical trauma
o Thermal Burns
o Cold
o Electrical
o Radiation (Eg. In Radiotherapy)
- Hypoxia:
• Thermoregulation ʹ (Varying blood flow ⮴Allows heat Conservation or Evaporative Cooling) •
Sensory organ
Basic Structure of Normal Skin:
- 3 Layers:
o Epidermis (Top Cellular Layer):
③ Keratinocytes
③ Melanocytes
③ The 5 Layers of the Epidermis:
ξ 1. Stratum Germinativum/Basale:
o Single layer of cuboidal/columnar cells
ξ 2. Stratum Spinosum (Prickle Cell layer):
o Several layers of polyhedral cells
ξ 3. Stratum Granulosum:
o 3-5 layers flattened cells
ξ 4. Stratum Lucidum:
o (Present only on very thick layers of epidermis (Eg. Glabrous Skin
[palms/feet]))
o = The Lucid layer of Flattened Cells before Stratum Corneum.
ξ 5. Stratum Corneum:
o 5-50 layers of Flattened, Dead Cells (Squames)
o Protective Barrier; Holds in Moisture
o Cytoplasm is filled with keratin & keratohyalin granules
o Dermis (Middle Fibrous Layer):
③ Connective Tissue
③ Blood Vessels
③ Nerves (Sensory Receptors & Free Nerve Endings)
③ Hair Follicles + Arrector Pili (the Smooth Muscle)
ξ NB: Skin without hair ʹ (Eg. Palms & Soles) = “Glabrous Skin”.
ξ NB: Skin With Hair ʹ (Ie. Rest of the body) = “Non-Glabrous Skin”.
③ Glands (Sweat, Sebaceous)
③ Contains Some Cells:
ξ Fibroblasts: Synthesis and degradation of connective tissue
ξ Histiocytes/Macrophages: Phagocytic cells
ξ Mast cells: Secretory cells ⮴Vasoactive Mediators (histamine) ⮴ Skin Allergies.
ξ Lymphocytes: Small number collect around blood vessels in normal skin
③ 2 Layers:
ξ (R) - Reticular Layer (thick Collagen, lower layer) - much stronger
ξ (P) - Papillary layer (fine Collagen, upper layer) - weaker
, o Hypodermis (Fat Layer):
③ Adipose Tissue
③ Functions:
ξ Insulates the body
ξ Stores Energy
- Glands:
o Sebaceous (Sebum) Glands:
③ Associated with hair follicles (The Pilosebaceous Unit)
ξ (:. Not found on Palms/Soles)(Most found on Face & Scalp)
③ Holocrine Secretion:
ξ (Ie. Secretion via complete destruction of cells)
ξ Produce oily sebum:
③ Stimulated by Androgens:
ξ Very Active at puberty
o Eccrine (Sweat) Glands:
③ On most of the body (Scarce on the back)
③ Simple, Coiled Tubular Glands:
ξ Secretory Coil (deep in Dermis) ʹ Secrete the Water & Electrolytes
ξ Sweat Duct ʹ Reabsorb Na+ Ions from the sweat.
③ Clear watery secretion
ξ Person can perspire several liters per hour
③ Stimulated by High Temperature and Stress
o Apocrine (Pheromone) Glands:
③ Associated with hair follicles
③ Large complex gland:
ξ Located in Dermis
ξ Duct Opens into Hair Follicle.
③ Viscous, Milky Secretion ʹ (protein and cellular debris):
ξ Produces pheromones
o Bacterial action is required for odor production
③ Stimulated by Androgens:
ξ Most Active at puberty
Causes of Skin Injury:
- Physical Agents:
o Mechanical trauma
o Thermal Burns
o Cold
o Electrical
o Radiation (Eg. In Radiotherapy)
- Hypoxia:
