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)
What are the functions of the reticular dermis?
- Gives the skin strength and elasticity
- Supports other appendages like hair follicles, sweat glands and subaceous glands
How is the epidermis water proofed?
Epidermal cells have their lipids forced out by keratin production
These lipids form a “cement” in the ECM, water proofing the tissue.
What determines skin colour?
- blood
- carotene
- melanin
How is melanin formed and used?
Melanocytes in the stratum basale form “inject” melanin into the spaces between cells to form a layer of it. which is mostly found on the “sun” side of cells.
How are hair follicles formed?
The epithelial cells in the stratum basale downgrow into the dermis through the papillary layer and into the reticular layer.
The cell is invaded by blood vessels
The hair follicles grows through the epithelial while still being in the dense irrefular connective tissue of the reticular layer.
How do arrector Pili muscles work?
Acetylcholine activates the muscles to perform piloerection
The muscle is attatched to the follicle root and the epidermis, when it contracts it pulls the follicle upright (straight)
Where are sebaceous glands, what do they secrete and what does it do?
Between the hair follicle and the pili arector muscle.
They secrete an oily substance called sebum
It lubricates the skin and follicle.
What are apocrine sweat glands?
They are a form of sweat gland which secretes protein rich sweat that cause the body odour.
They secrete sweat in vesicles which travel to the surface.
What makes up an eccrine sweat gland?
A simple tubular gland in the dermis made up of:
A coiled secretory portion in the dermis
A coiled and straight duct in the dermis
A spiral channel in the epidermis
Where do eccrine glands secrete?
directly to the surface of the skin
What is the function of eccrine sweat gland?
Thermoregulation
Name two types of corpuscles and what they sense?
Paccinian corpuscles sense vibration and pressure
Meissners corpuscles sense light touch
Name two other receptors in the skin
Pain receptors and thermoreceptors
Describe the four steps of skin repair:
- A clot forms blocking blood flow out the wound
- A scab forms to block infection above an inflammatory response
- Granulation tissue forms and the scab falls off
- A scar forms, containing no appendages (follicles, glands etc)
