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.
- Sebaceous glands, what do they produce = ?
- Sudoriferous glands, where are they NOT located = ?
- Sebaceous glands: They produce sebum, which lubricates the skin and hair and protects against bacteria.
- Sudoriferous glands: They are found throughout the skin except on the lips and ears, secreting sweat for thermoregulation.
Where do nails originate?
They originate from the basal layer of the epidermis, protecting the tips of digits.
What is the composition of the subcutaneous layer?
It contains adipose tissue, deep blood vessels, and nerve endings.
What is the primary function of adipose tissue in the subcutaneous layer?
It provides insulation, energy storage, and cushioning.
How is the skin connected to muscle?
Through fibers that extend from the dermis into the subcutaneous layer, anchoring it.
What is the function of tendons in relation to skin?
Tendons connect muscles to bones, facilitating movement and supporting skin structure.
How does bone interact with the skin?
Bones provide structural support to which skin and other tissues attach.
How are keratinocytes attracted to wound areas?
They are attracted by neutrophils, macrophages, and the current of injury, advancing in a sheet.
What is the role of the acid mantle in skin?
It creates a barrier against bacteria, supporting skin protection.
What is the role of the cornified envelope in corneocytes?
It provides a physical, chemical, and immunological barrier.
What is eledin, found in the stratum lucidum?
Eledin is a substance that transforms into keratin in the stratum lucidum.
How does the stratum granulosum contribute to skin waterproofing?
It contains keratohyalin, a precursor to keratin, which waterproofs the skin.
What happens in the stratum basale?
New cell production occurs, and it contains Merkel cells and melanocytes.
How does the stratum spinosum maintain skin integrity?
Cells in this layer are connected by desmosomes, providing structural support.
What are Meissner’s corpuscles?
Meissner’s Corpuscles:
- They are light touch mechanoreceptors located in the papillary region of the dermis.
What are…
- Bulbous/Ruffini corpuscles = ?
- Pacinian corpuscles = ?
Bulbous / Ruffini corpuscles: Mechanoreceptors that sense sustained pressure and warmth in the skin.
Pacinian corpuscles: Mechanoreceptors in the reticular region that detect vibration and pressure.
What is the function of sebum?
Sebum lubricates skin and hair, preventing bacterial growth.
What layer do hair follicles originate from?
They originate from the dermal layer, assisting in temperature regulation.
How does the subcutaneous layer aid in vitamin storage?
It stores vitamins A, D, E, and K, serving as a reserve.
What is the appearance of healthy subcutaneous tissue?
It is typically white or pale yellow, indicating healthy fat tissue.
What is the role of the basement membrane?
It attaches the epidermis to the dermis and acts as a scaffold for the epidermis.
What is the significance of the rete ridges?
Rete Ridges: They increase the surface area for nutrient exchange between the dermis and epidermis.
How does the dermis contribute to skin turgor?
The dermis contains collagen and elastin, which provide structure and flexibility.
What is the ground substance in the dermis?
It is an extracellular matrix that supports dermal cells and structures.
Dermis cell types…
- Fibroblasts produce = ?
- Macrophages = ?
- Dendritic cells activate = ?
- Mast cells produce = ?
- Fibroblasts produce collagen and elastin.
- Macrophages scavenge debris and Microorganisms.
- Dendritic cells present antigens, activate T-cells for immune response.
- Mast cells produce histamines.
- Histamine causes vasodilation and increases permeability during inflammation
