Skin System Flashcards
What are the three main layers involved in the integumentary system
Epidermis
Dermis
Hypodermis
Describe hypodermis?
- not classified as a layer of skin but a layer of adipose tissue
- bottom layer
Function of hypodermis?
Protection
Insulation
Connects dermis to muscle and bone
Describe dermis?
middle layer
- Contains many structures including; elastic and reticular fibres, collagen, hair follicles, sweat glands, nerve endings, sebaceous glands and blood vessels
Function of Dermis
Epidermal nutrition - the blood vessels carry nutrients to epidermis and remove waste products
Provides strength - due to collagen
Provides flexibility - due to elastic fibres
Describe Epidermis?
- most superficial layer
- can vary in thickness e.g. 0.1mm on eyelids whereas 1mm on palms of hands
- avascular = lack of its own blood supply
What are the four main cells found in the epidermis?
Keratinocytes = for protection by forming a barrier
Melanocyetes = skin pigmentation
Langerhans cells = for immune response
Merkel Cells = form sensory structures
How many layers can epidermis be sub-divided to?
5 layers;
- stratum corneum
- stratum lucidum = only on fingertips, soles and palms
- stratum granulosum = granular cell layer
- stratum spinosum = spinous layer
- stratum basale = basal layer
What are the main functions of the skin?
Regulation of temperature:
- Vasoconstriction/ vasodilation = narrowing/widening of blood vessels
-sweating
-piloerection e.g. goosebumps
Protection
- physical barrier
- prevents water loss
Cutaneous sensation
- receptors within skin respond to temperature, touch, pressure and pain
Synthesis of Vitamin D
Excretion of waste products and sebum
Describe the skin response when warm?
Hair erector muscles relax
Sweat glands excrete sweat
Vessels dilate
Describe the skin response when cold?
Hair erector muscles contract
Sweat glands do not excrete sweat
Vessels constrict
What are the two cells involved in Immunity and protection?
Langerhans cells
Keratinocytes
Describe Langerhans cells?
- Formed in bone marrow and migrate to epidermis
- Engulf and breaks down pathogens
Describe Keratinocytes?
- Make up 90% of epidermal cell in humans
- Form a barrier against environmental damage
- Re - epithelialisation = wound healing
- Express cytokines to immune cells
- Prevent water loss at skin surface
- Apoptosis occurs at stratum granulosum layer
Describe Melanocytes?
- described as spider shaped cells
- located within the bottom layer of the epidermis
- synthesise melanin, the absorbed by keratinocytes
- keratin and melanin combined protect the skin from harmful effect of UV damage
Describe Merkel cells?
- contains mechanoreceptors = essential for touch sensation
- abundant in highly sensitive skin e.g. fingertips
- exist in the basal layer of the epidermis
- the development of merkel cells and other functions still have unanswered questions
Describe cutaneous sensation?
- 31 pairs of spinal nerves
- single nerve roots:
-supply a specific area of skin
-detecting pressure
-pain
-temperature
-texture
-send signals via the spinal cord to the brain - each of the specific areas of skin supplied by a single nerve root is called dermatome
- 30 dermatomes across body - C1 does not have sensory root
Give an overview of hair
- covers almost every surface of the human body
- babies born with approx. 5 million hair follicles on their body = most human will ever have
- follicle = where hair grows and held in position
- shape of hair strands determines whether hair is curly or straight
- amount of melanin in hair follicles dictates the colour; the more melanin , the darker the hair.
List the stages of the hair growth cycle in order.
- Anagen
- Catagen
- Telogen
- Return to anagen
- Early anagen
Functions of Hair
Heat Preservation
Sebum Production
Friction Prevention
Protection
Communication
Give an overview of nails
- main exterior of nail = nail plate and formed by layers of keratin
- nail folds = lateral and proximal
- surround and protect margins of nail plate
- nail bed (sterile matrix) = provides a smooth surface for nail to grow over
- germinal matrix = cells within this continually divide and become keratinised to form the nail plate
- eponychium (cuticle) = layer of skin that extends from the finger over the nail plate
- lunula = distal edge of the nail matrix
What is the purpose of fingers?
allows us to perform tasks with our hands due to its flexibility
