Skin Anatomy and Physiology Flashcards
The largest organ system = ?
The skin is the largest organ system;
- recieves 1/3 resting cardiac output
- weighs > 4-5 kg
- ranges in thickness from 0.5-6.0 mm.
What are the primary functions of the skin?
- thermoregulation - excretion of sweat
- sensation
- storage & synthesis - vitamin D synthesis, lipid and water storage
- protection - from shear, water loss, and bacteria
- body image, expression
What are the three main layers of the skin?
- epidermis
- dermis
- subcutaneous/hypodermis
Epidermis…
- Main function of the epidermis?
- How often does the epidermis regenerate?
- Thickness?
- It serves as a protective layer, preventing water loss and providing pigmentation and sensation.
- The epidermis repairs/regenerates every 28 days.
- .05 - .6 mm thick
What is the dermis primarily responsible for?
It houses sensory organs, vasculature, and dermal appendages, providing nourishment and thermoregulation.
What is the subcutaneous layer also known as?
It is also known as the hypodermis or endodermal layer.
What structures are found in the dermis?
Sensory organs, vasculature, hair follicles, sweat glands, and sebaceous glands.
What is the primary function of the subcutaneous layer?
It acts as an insulator, energy reserve, and cushion, while also storing vitamins A, D, E, and K.
Cells of the Epidermis
What is the role of keratinocytes?
They accumulate keratin and migrate to resurface injured areas; they make up 90% of epidermal cells.
- Hard keratin is found in hair and nails.
- Soft is found in the stratum corneum.
- Can’t bridge a gap
Cells of the Epidermis
What are corneocytes?
Corneocytes are keratinocytes in their final stage, forming a barrier to physical, chemical, and immunological threats.
Cells of the Epidermis
What is the function of Langerhans cells?
They are dendritic cells that signal T-cells for immune response, but can be necrosed by UV rays.
Cells of the Epidermis
What is the role of melanocytes?
Melanocytes synthesize melanin from tyrosine, contributing to pigmentation in the epidermis.
Cells of the Epidermis
What function do Merkel cells serve?
They are mechanoreceptors that detect light touch and transmit the signal via the Merkel disc in the dermis.
Layers of the epidermis
What is the stratum corneum?
It consists of 25-30 rows of flat, dead cells filled with keratin, acting as a barrier to heat, light, bacteria, and chemicals.
Where is the stratum lucidum found?
It is found in the palms and soles of the feet.
What is the function of the stratum granulosum?
It contains keratohyalin, a precursor to the waterproofing protein keratin.
What cells are found in the stratum spinosum?
Polyhedral keratinocytes and Langerhans cells.
- More mature rows of keratinocytes appear “spiny” due to keratin filament formation
- Attached together by desmosomes
What is the papillary region?
- The upper 1/5 of the dermis
- Containing dermal papillae and Meissner’s corpuscles for light touch.
What is the reticular region?
What senses?
Consists of dense irregular connective tissue with collagen, elastin, and mechanoreceptors.
What are fibroblasts?
Cells in the dermis that produce collagen and elastin for structure and flexibility.
What role do macrophages play in the dermis?
They scavenge debris and microorganisms, aiding in infection control.
What are mast cells?
Dermal cells that produce histamine, which contributes to inflammatory responses.
What is the role of hair follicles?
They help regulate temperature by trapping air and regenerate the epidermis after abrasions.
