Lecture 4 - The Integument: Structure and Function Flashcards
Integument
The largest and most visible organ in the human body. It consists of the cutaneous membrane + accessory structures
4 major functions of the integument
- Provides a barrier against the external environment - immune and osmotic homeostasis
- Vitamin D and Ca2+ homeostasis
- Thermal homeostasis
- Sense organ
True or False: the hypodermis is a part of the integument
False - it is not integumentary
Thin skin vs. thick skin
Thin skin - hairless. Found on palmar and plantar surfaces
Thick skin - hairy. Found everywhere else
Name the 6 layers of stratified squamous epithelium of the epidermis from the most superficial to the deepest layer
Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale
“Come Lets Grab Some Beers”
Describe the process of proliferation/renewal of epidermal cells
Epidermal cells are continuously generated:
In the deepest layers (stratum basale)
Differentiated in the middle layers (basal cells differentiate into keratinocytes in the stratum spinosum)
Shed from superficial layers
What is insensible perspiration and how does the epidermis limit insensible perspiration?
Insensible perspiration is water loss through the cutaneous membrane, not through the sweat glands
The epidermis is keratinized, meaning its cells are filled with keratin (which is a tough, cross-linked, water-resistant protein) and limits insensible perspiration
Melanin function
It can absorb UV photons and prevent DNA damage in cells by releasing the energy safely
Melanocytes
Located in the stratum basale, they produce melanin pigments and transfer them to keratinocytes
Melansomes
Organelles located inside melanocytes that synthesize and store melanin pigments
Explain how melanocytes, melanosomes, and melanin contribute to different skin colours
Darker skin is due to melanocytes bring more active, transferring more melanosomes more frequently. Furthermore, there are different versions of melanin, which contribute to different hues of skin colour
Dermis
Contains connective tissue and accessory structures that support the epidermis or allow for secondary skin functions
Name general examples located inside the dermis layer
Stratum papillare (loose)
Stratum reticulare (dense, irregular, elastic)
Accessory structures (ex. sensory neurons, hairs and glands)
Extensive vasculature
Are neurons present in the dermis?
Yes - the dermis contains somatosensory (touch and nociceptive (pain) neurons. Everyone’s skin has the ~same number of sensory neurons per unit area
Hair and nails function
They are highly keratinized accessory structures and help serve to protect the integumentary system. The hair shaft and nail bodies are made up of dead cells
Glands function
Epithelial structures in the integument that serves to protect and/or maintain homeostasis
Describe the difference in healing process between the epidermis and dermis
The first stage is the same for both - an inflammatory response increases blood flow and there is an attraction of immune pathocytic cells at the site. Then:
Epidermis - undergoes proliferation from basal cells and granulation tissue forms. A scab formed at the surface
Dermis - undegoes recruitment, proliferation, and differentiation. Very high proliferation and secretion from fibroblasts results in keloid scar formation
Significance of skin in thermal homeostasis
It plays an important role in being a sensor and effector in thermal homeostasis through evaporative cooling and radiant cooling (vasodilation allows heat loss across the epidermis)
The redness on people’s face after exercising or consuming alcohol is due to increased blood flow to superficial dermal layers - light skin isn’t thinner, just more transparent
Significance of the epidermis in calcium homeostasis
It synthesizes Vitamin D, which is needed to synthesize calcitriol (a hormone), thereby contributing to calcium homeostasis
Trade-off between melanin and vitamin D synthesis
Less vitamin D results in less cell damage because the upper layers of the epithelium absorb more UV light, meaning less reach the basal layers
More vitamin D results in more cell damage because the upper layers let more UV light through to basal layer
Intensity of UV radiation and latitude
At high altitudes (ex. Canada), there is less UV that can be absorbed. So, sunscreen is more efficient and dietary vitamin D is more necessary. The less UV in the environment, the less gets through the melanin to reach basal layers
How are changes in the skin and other integumentary structures seen?
Most visible signs is ageing. These changes compromise the critical physiological functions of skin
