Skin 1 Flashcards
What terms used to describe epidermal cells?
Keratinocytes
What are the functions of the epidermis?
Prevents water loss by evaporation
Waterproof
Protects the tissues from injury and infection
Functions of the Dermis
Reduces injury risk
Maintains blood flow to the epidermis, it diffuses up through the cells into the epidermis
Permits body cooling by sweat & vasodilation
What are the other functions of the skin?
Uv Protection, energy storage, sensory info, immune surveillance
What is the basic structure of the epidermis
Epithelial Tissue
Forms internal/external compartment boundary
Basic structure of the Dermis
Connective tissue
Gives structural strength
What is the makeup and function of the Hypodermis?
Made of adipose CT layer just below the dermis (i.e. subcutaneous tissue)
It anchors skin to underlying structures but isnt skin itself
What type of epithelial tissue makes up the epidermis?
The Stratum Basale is made up of columnar epithelial cells which are compressed as theyre pushed upward making them stratified squamous cells.
Name the 5 layers of the epidermis:
Stratum Basale Stratum Spinosum Stratum Granulosom Stratum Lucidum Stratum Corneum
Name the 4 types of epidermal cells and theyre functions:
Keratinocytes - most common, they contain keratin to make the epidermis hard and resistant to abrasion. They also extrude lipids to form a “cement” that waterproofs the epidermis.
Melanocytes - Pigment formation
Langerhans Cells - Immune surveillance
Merkel Cells - Sensory Receptors
Describe 4 properties of the Stratum Basale:
- Tall columnar cells intersprersd with melanocyte and merkel cells
- Bound to the basal membrane by hemidesmasomes
- Irregular interface (like interlocking fingers) with the dermis to prevent the epidermis sloughing off
- Continuous cell proliferation
Why is the Stratum Spinosum called that?
Post-mortem the cells shirnk and the desmosomes form spines which were originally thought to be normal
What is the function of the Stratum Spinosum?
Prepares cells for keratinisation
What distinguishes the Stratum Granulosum?
Prescence of keratohyahlin granules
What is the function of Stratum Granulosum?
To produce Keratohyahlin, a precursor to keratin
What is the function of the Stratum Lucidum?
To produce Keratin from keratohyahlin, ejecting all the organelles and lipids from the cells to produce dead keratine cells and an extracellular “lipid cement” to waterproof the epidermis
What is the turnover rate of the stratum Corneum?
15-30 days
Quickly summarise Keratinisation:
1) Stem cells in Stratum Basale divide and specialise to form columnar epithelial cells, specifically keratinocytes
2) As theyre pshed up by new ones beneath they flatten and become stratified squamous epithelial cells
3) They produce kerahtoyahlin in the Stratum granulosom which is converted keratin in the stratum lucidum
4) The cells die as organelles and lipids are pushed outward
5) By the stratum corneum the cells are dead stratified squamous cells, full of keratin.
Why is keratinisation important?
Its vital because keratin forms a mesh like layer that protects the skin from damage or infection, protects hair follicles and ives strength to the nails
How does skin thickness change?
It varies depending on the activies and abrasion to that part of the body.
Generally the palms and soles are thick adn the abdmominal is thin
It can change, the stratum corneum varies the most but the dermis also changes.
What are the functions of the dermis papillary layer?
It forms an irregular interface with the stratum basale to ensure the epidermis doesnt slough off.
It also protects against pathogens
Why dose the papillary layer have its own blood and nerve supple?
for thermoregulation, nutrition, blood flow to the epidermis by diffusion and as a sensory organ.
What makes up the papillarly layer?
Loose connective tissue (cellular)
What makes up the reticular dermis layer?
Dense irreular connective tissue, specifically bundles of collagen (elastic fibrous)
