Integumentary System Flashcards
What is the integumentary system?
The largest and most visible organ in your body
Made of the “cutaneous membrane” + accessory structures
What are the four functions of the integumentary system?
- Acting as a barrier - between outside and inside environment, protecting the inside from pathogens and toxins, keeping the things that should be inside from escaping
- Vitamin D & Calcium2+ Homeostasis
- Thermal Homeostasis - ability to regulate temperature, losing extra heat, cooling off
- Sense Organ - everything in your sin is full of nerves (sense of touch and pain)
What is the cutaneous membrane?
The cutaneous membrane is a tissue membrane
Tissue membrane = epithelial + connective
Cutaneous membrane = epidermis (epithelial) + dermis (connective) + accessory structures (epithelial)
What is the epidermis?
- stratified squamous epithelium
- avascular (no blood vessels)
- receives nutrients from absorption, diffusion, and filtration
- contains 4-5 layers
- outer/top layer of the cutaneous membrane
- epidermis is keratinized
What is the dermis?
The dermis is connective tissue that contains many accessory structures necessary for
skin functions, including sensation, protection and thermo/osmotic regulation
- inner layer beneath the epidermis of the cutaneous membrane
- contains connective tissue and accessory structures that support the epidermis
- extensive vasculature (lots of blood vessels)
- contains many somatosensory (touch) and nociceptive (pain) neurons
- has 2 layers (stratum papillare and stratum reticulare)
What is the hypodermis?
- subcutaneous
- not part of the integument
- composed of connective tissue / separate from the skin
What is thick skin?
- hairless skin
- found on palmar and plantar surfaces
- 5 layers in the epidermis
- one extra layer (stratum lucidum)
- lacks hair, sebaceous glands, and apocrine sweat glands
What is thin skin?
- hairy skin
- more accessory structures
- found everywhere else (other than palmar and plantar surfaces)
- 4 layers in epidermis
- does not have stratum lucidum
- fewer layers of cells in the stratum granulosum, spinosum, corneum
- has thicker dermis and less eccrine glands
What are the five layers of the epidermis?
Come Let’s Grab Some Beer
- Stratum corneum
- Stratum lucidum
- Stratum granulosome
- Stratum spinosum
- Stratum basale
Differentiate thick skin from thin skin
Thick skin is HAIRLESS, while thin skin is HAIRY
Thick skin is found on PALMAR AND PLANTAR SURFACES, while thin skin is FOUND EVERYWHERE ELSE
Thick skin has 5 layers in the epidermis (stratum lucidum), while thin skin only has 4 layers (no stratum lucidum)
Thin skin has MORE ACCESSORY STRUCTURES than thick skin
What are keratinocytes?
Keratinocytes in the epidermis receive melanin from melanocytes and accumulate
keratin through their lifetime, allowing them to form a water-resistant protective barrier that blocks chemical and physical harms.
- basal cells are proliferated/renewed at the basal layer
- they migrate upwards towards the surface of the epidermis and differentiate into keratinocytes
What is keratin?
a touch, cross-linked, stiff, and water-resistant protein
- because keratin is capable of binding cells together very tightly, it limits insensible perspiration and paracellular transport
What is insensible perspiration?
loss of water through the cutaenous membrane/skin
- not through sweat glands
What are melanocytes?
Cells in the stratum basale that make melanosomes/produce melanin pigments
What are melanosomes?
Organelles in melanocytes that are filled with melanin/produce melanin pigments and are transported by vesicular transport
What is melanin?
- an organic molecule synthesized by enzymes within the melanocytes
- variation of melanin that is made is what determines the colour of skin
Debunk myths about dark vs light skin
Darker skin is NOT THICKER than light skin - darker skin is due to melanocytes being more active, transferring more melanosomes more frequently = more pigments
- there are different versions of melanin which contribute to the variety of skin hues
What are the dangers of UV light and what is a solution to combat them?
PROBLEM: UV light damages cells - particularly DNA
SOLUTION: melanin can absorb UV photons and prevent this damage
too much UV light -> too much UV photo absorption -> accumulation of mutations -> damages DNA -> melanin produced by melanocytes absorbs UV photons -> can release the energy safely (so DNA does not absorb it)
Describe the tanning response using the integumentary system
- area that absorbed more sunlight becomes darker
- UV stimulation caused additional production and distribution of melanin (prevent DNA damage)
Is tanning considered homeostasis or allostasis?
Could be both!
- Homeostasis
- DNA is the control variable
- you want to control how much DNA is being damaged
- UV stimulation triggers a response to control DNA damage and restore homeostasis
- sensor: nucleus
- effector: melanocyte - Allostasis
- melanocyte is the control variable
- your body is anticipating more DNA damage because of UV stimulation
- melanocytes are anticipating a future event so they shift their set point to produce more melanosomes
How is the epidermis different from the dermis?
Epidermis = epithelial (5 layers)
Dermis = connective (2 layers)
Epidermis = top, thinner, superficial layer
Dermis = middle, thicker, deeper layer
Epidermis = contains both living and dead cells
Dermis = contains accessory structures
What are the two layers in the dermis?
- stratum papillare
- stratum reticulare
What are the two types of neurons found in the dermis?
Somatosensory (touch)
Nociceptive (pain)
What is a nociceptive neuron?
free-nerve ending neuron that senses pain in touch
What are the three accessory structures found in the integumentary?
- hair
- nails
- glands (sebaceous and sweat)
(sensory neurons)
Accessory structures (including sensory neurons, hairs and glands) are embedded within dermal layers.
What do hair and nails have in common as accessory structures?
both are highly keratinized (contain keratin)
- hair shafts and nail bodies are made of dead cells
- act as a barrier
Glands are _____________structures but they are found in the ___________.
Glands are EPITHELIAL structures but they are found in the DERMIS.
What are the two types of glands (accessory structures)?
- sebaceous glands
- sweat glands
What are sebaceous glands?
glands in the dermis that secrete sebum
- produce oil
- may or may not be attached to hair
- protects skin from drying and inhibits harmful bacterial growth
What are sweat glands? What are the two types?
glands in the dermis that secrete sweat
- allows body to regulate temperature
- cools the skin as sweat evaporates (water’s high heat of vaporization)
- apocrine gland - axillary & pubic regions (viscous sweat, produces body odour)
- eccrine gland - found everywhere else (watery sweat)
The integument repairs itself in four phases:
- Inflammation
- Migratory
- Proliferation
- Scarring
What is the inflammatory response?
- mast cell activates inflammatory reaction
- rush of phagocytes to the scene
- attraction of immune phagocytic cells
- increased blood flow
- defensive response
What is the migratory phase?
- epidermis and dermis repair themselves following different mechanisms:
Epidermis: basal cells go into proliferation, stop producing keratinocytes / rapid cell division and migration to replace missing cells
Dermis: recruitment, proliferation, differentiation / formation of granulation tissue (new fibroblasts, blood vessels, etc.)
- blood clot or scab temporarily acts as the epidermis & prevents invasive microorganisms from entering through the injury site
- fibroblasts & mesenchymal cells begin formation of new blood vessels and granulation tissue
What is the proliferation phase?
- fibroblasts continue to produce collagen fibres & ground substance
- not fully restored, but dermis will have lots of collagen fibres and fewer blood vessels/capillaries
Epidermis: normal division
Dermis: fibroblasts produce more collagen
What is the scarring phase?
- scar tissue formation
- damaged accessory structures are repaired & replaced by fibrous tissue
- results in an inflexible, fibrous, noncellular scar tissue
Dermis: activation, enhance collagen secretion to seal up cut
What is a keloid scar?
excess scar tissue formation beyond what is needed for tissue repair
- raised, thickened mass of scar tissue from site of injury growing into dermis
- covered by shiny, smooth epidermal surface
- very high proliferation and secretions from fibroblasts is pushed up
**How does the integument participate in thermal homeostasis?
skin plays a critical role as a sensor and an effector in thermal homeostasis
- evaporative cooling - sweating and water’s high heat of vaporization
- radiant cooling - blood vessels in the dermis can force heat loss across the epidermis
Explain why the face gets red when you exercise or are drunk?
there is an increased blood flow to the superficial layer - only see it in some people with lighter skin, not because lighter skin is thinner, but because its more transparent – you cannot see the blood through melanin
What is calcium homeostasis and vitamin D synthesis?
the epidermis participates in calcium homeostasis through the body by synthesizing vitamin D
- deep layers can synthesize vitamin D from UV wavelengths
- those cells still have nuclei
- vitamin D is needed to synthesize calcitriol (a hormone) which helps you retain calcium
What are trade-offs between melanin and vitamin D synthesis?
dark = less vitamin D but less cell damage
- upper layers absorb more UV, less reaches basal layers
light = more vitamin D but more cell damage
- upper layers let more UV light through to basal layers
How do changes in the skin indicate aging? Provide the physiological explanation for each reasoning listed
Ageing has many effects on the integument, and these can be accelerated through exposure to damaging stimuli such as UV (or chemicals).
Outline (describe or explain) a probable physiological mechanism for why white US women are more likely to experience ‘photoaging
- more exposure/absorption leads to faster rates of aging
- cells in the basal layer are experiencing more damage
- every time you have cell damage in the epidermis, you must proliferate basal cells again
- stem cells do not have infinite capacity
- eventually you’ll get to the point where your basal cells will stop repairing
- more times you force your skin to repair, the less capable it is to repair itself next time
The last epidermal layer to be replaced
after a wound is the:
stratum corneum is the last epidermal layer to be replaced (on the bottom/deepest layer)
The reason you sometimes bleed more after knocking a scab than for the original damage is most likely due to:
Formation of new blood vessels in granulation tissue.
How are melanin and UV related to the integument?
tanning response: - area that absorbed more sunlight becomes darker
- UV stimulation caused additional production and distribution of melanin (prevent DNA damage)
Describe how scar formation is associated with the integumentary system?
Explain the four major functions of the integument using specific examples of how the properties of the dermis, epidermis or accessory structures contribute to each function
- Barrier
- Vitamin D and Calcium2+ Homeostasis
- Thermal Homeostasis
- Sensory sensations
Explain the general function of melanin and how melanocytes contribute to skin colour at baseline and analyze the physiological response of melanocytes following UV exposure
Identify at least three examples of accessory structures within the integument.
- hair
- glands (sebaceous and sweat glands - apocrine and eccrine)
- nail
Compare and contrast the processes of tissue repair in the dermis and epidermis, and describe the origin of both granulation tissue and scar tissue in the integument.
Describe the roles of the skin as a key effector organ in thermal homeostasis
evaporative cooling - sweat can be released onto the surface of the skin and water’s high heat of vaporization would cause the skin to cool down significantly
radiant cooling - heat loss from the blood vessels radiating across the epidermis
**Explain how skin and UV exposure are linked to Vitamin D and calcium homeostasis, and analyze
the trade-offs between melanin and vitamin D synthesis.
Although too much sunlight can damage epithelial cells and deeper tissues, limited exposure to sunlight is beneficial because UV radiation plays a vital role in the synthesis of an important vitamin: cholecalciferol, or vitamin D3.
When exposed to ultraviolet radiation,
epidermal cells in the stratum spinosum and stratum basale convert a cholesterol-related steroid into cholecalciferol.
The liver then converts cholecalciferol into an intermediary product used by the kidneys to synthesize the hormone calcitriol
Calcitriol helps with retaining calcium
**Identify key effects of ageing on the integument and discuss how this interacts with UV exposure.
- more exposure/absorption leads to faster rates of aging
- cells in the basal layer are experiencing more damage
- every time you have cell damage in the epidermis, you must proliferate basal cells again
- stem cells do not have infinite capacity
- eventually you’ll get to the point where your basal cells will stop repairing
- more times you force your skin to repair, the less capable it is to repair itself next time
What happens in the stratum basale?
the deepest layer of the epidermis (1)
- inner most, epidermal layer
- made of stem cells, Merkel cells, and melanocytes
- single layer of cells
- site of keratinocyte production
What happens in the stratum spinosum?
- on top of the stratum basale (2)
- keratinocytes produced in the stratum basale are pushed up and differentiate in the stratum spinosum
- forms several layers of cells containing keratin
What happens in the stratum granulosome?
- on top of the stratum spinosum (3)
- forms 3-5 layers of flattened cells
- nuclei and organelles begin to disintegrate from the cells
What happens in the stratum lucidum?
- on top of the stratum granulosome
- only found in thick skin, NOT THIN SKIN
- contains dead cells
- skin sheds from these superficial layers
What happens in the stratum corneum?
- outer most epidermal layer, on top of the stratum lucidum/granulosome
- cells in this superficial layer are already dead
What is the stratum papillare?
- top, thinner layer of the dermis, connected to the stratum basale
- layer of FAT (made of areolar tissue)
- contains touch receptors called Meissner corpuscles
What is the stratum reticulare?
- bottom layer of the dermis, beneath the stratum papillare
- thicker than the stratum papillare
- layer of tissue (composed of dense irregular connective tissue)
- contains sebaceous glands, sweat glands, nerves, and hair follicles
What are the 5 skin cells and where are they found?
Epidermis:
1. Keratinocytes - produce keratin (producing skin barrier)
2. Langerhans cells - involved in immune responses
3. Melanocytes - produce melanin (skin pigment and UV absorption)
4. Merkel cells - detects touch, pain, sense
Dermis:
5. Fibroblasts - produces collagen
Describe the features and functions of hair as an accessory structure
- found in thin skin
- found in the dermis
- made of dead epidermal cells, only alive at the bulb
- by the time hair reaches the skin surface, they have been converted completely to keratin (so they’re dead xx)
Describe the structure of hair
- hair follicle - site of new hair cell development
- hair root
- shaft - as hair is pushed out of their cells, they become keratinized and form the shaft
by the time hair reaches the skin surface, it is completely dead already
smooth muscle called the arrector pili is attached to hair and can contract to pull the hair upright when you get “Goosebumps”
