Skin Flashcards
What makes the skin an organ?
The skin is an organ because it is made up of all four types of primary tissue (epithelium, connective tissue, muscle, nerve).
What is the largest organ in the body?
The skin
Name some pathologies of the skin
sunburn, acne, eczema, psoriasis, melanoma
Name the 4 primary functions of the skin
- Immune surveillance
- UV protection
- Energy storage
- Sensory function
Name the two layers of the skin
- Epidermis
2. Dermis
What is the epidermis made from?
Stratified squamous keratinising epithelial cells
How many layers are fund within the epidermis?
5 Strata (layers)
What is the main role of the epidermis?
Prevents water loss through evaporation
What is the dermis made from?
Connective tissue
What does the dermis provide?
Structural strength
How does the dermis help to maintain the epidermis?
The dermal blood flow helps to maintain the epidermis
What does the dermis permit?
Body cooling
What is the hypodermis?
The adipose layer found underneath the skin
What is the function of the hypodermis?
The hypodermis anchors skin to underlying structures
What is the main cell type found in the epidermis?
Keratinocytes
What do keratinocytes contain and why?
Keratinocytes contain keratin which is a hard substance that is resistant to abrasion
What makes the epidermis waterproof?
Keratinocytes extrude lipids in order to make the epidermis waterproof
What kind of organisation are epidermal cells in?
Stratified squamous
Aside from keratinocytes, what other cells are found in the epidermis (3)
- Melanocytes
- Langerhans cells
- Merkel Cells
Name the 5 layers of the epidermis
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale (germinativum)
What gives the stratum corneum it’s strength?
The high number of disulphide bonds
What binds the cells of the stratum corneum together?
Desmosomes
What happens in the keratinocytes of the stratum corneum?
Keratohyalin is converted into keratin.
Keratinocytes flatten out and die and get sloughed off (15-30 day turnover).
Which player of the epidermis contains high levels of keratohyalin?
stratum granulosum
Hw do the cells look in the stratum spinosum?
Cells look spiny
In which leader of the epidermis does keratinisation begin?
Stratum spinosum
Why do the cells of the stratum spinosum look spiny?
The spiny appearance is created by cells shrinking but desmosome junctions create the spiny appearance
Describe the cells of the stratum basale
Tall columnar cells interspersed with melanocytes and Merkel cells
What are the cells of the stratum basale bound to? what binds the two structures together?
hemidesmosomes bind the stratum basale to the basement membrane
What helps to knit the epidermis and the dermis together?
There is an irregular interface between the stratum basale of the epidermis and the dermis. Dermal papillae help to knit the two layers together
Explain the process of keratinisation in the epidermis
- Stem cell division in the stratum basale
- Incorporation of keratin
- Cell flattening
- Loss of nuclei and protoplasm
- Dead cells in the stratum corneum are sloughed off
What is meant by “keratinisation”?
Keratinisation = Organic process whereby keratin is deposited in cells and these become horny as in dead skin, nails, hair
Name a condition caused by a malfunction in keratinisation
Psoriasis
Where in the body would you find think epidermis and which layer of the epidermis is thickened?
Palms of the hands and soles of the feet (stratum corneum is thickened)
Where would you find thin skin and which layer of the epidermis is thinned?
Abdominal skin is thin skin (caused by a thin Stratum corneum)
Name the two layers of the dermis
- Papillary layer
2. Reticular layer
Describe the structure and function of the papillary layer
This is a layer of lose connective tissue but it is highly cellular.
- It forms the papillae that anchor the dermis and the epidermis together.
- Filled with macrophages (protective against infection)
- Highly vascular (facilitates
thermoregulation and nutritional functions) - Sensory (filled with nerve endings)
What is the reticular layer made up of?
Dense irregular connective tissue
What provides elasticity in the reticular layer of the dermis?
collagen bundles
What three things give skin it’s colour?
- Blood
- Carotene
- Melanin
Where is melanin produced?
Melanin is produced by melanocytes in the stratum germinativum
describe the origin of hair follicles
- In utero, the epithelia invaginates and grows downwards to create a hair follicle
- A knot of blood vessels supply the follicle and facilitate the growth of hair.
- Growth of hair
What makes up a hair follicle?
Hair + Hair sheath
what attaches the follicle root and the base epidermis?
Arrector pilling muscles
What happens to the hair follicle when the arrestor pilli muscle contracts?
The follicle sits at an angle when the muscle is relaxed and straightens when muscle contracts
Where would you expect to find a sebaceous gland?
Sebaceous glands can be found between the hair follicle and the arrector pili muscle
What do sebaceous glands secrete?
Sebum
Name the two different types of skin gland
- sebaceous
2. Sweat (apocrine and eccrine)
What is an apocrine sweat gland?
A sweat gland that is usually associated with a hair follicle
Where are you likely to find an apocrine sweat gland?
In axilla body regions
What do apocrine sweat glands secrete?
Thick, protein rich fluid (this is boy odour)
Describe the morphology of eccrine sweat glands
simple tubular with a coiled secretory portion. There is a coiled and straight duct in dermis and a spiral channel in epidermis
What do eccrine sweat glands secrete?
Watery secretion (sweat)
Why do eccrine glands produce sweat?
Thermoregulation
Name the sensory receptors found in he skin
- Meissner’s corpuscles
- Paccinian corpuscles
- Pain receptors
- Thermoregulation
What do meissner’s corpuscles detect?
Light touch
What do Paccinian corpuscles detect?
Vibration and pressure
List the 6 stages of skin repair
- Skin is cut
- Blood clot forms
- Blood clot coagulates to a scab in order to plug gap
- Dermis produces granulation tissue to permanently plug the gap
- Scab falls out
- Granulation tissue takes it place (this is scar tissue)
The nail grows from the nail plate which is a specialised form of epidermis. What layer of the epidermis is replaced by the nail?
Stratum corneum
What is the function of the cuticle?
to protect the area between the nail and epidermis from exposure to bacteria.
What is the scientific name for a nail bed?
Eponychium
What is the name given to the area of epithelium right at the tip of your finger where the nail overhangs
Hyponychium
