Integumentary System I Flashcards
What is the largest system of the body?
The integumentary system
How much of our body weight is comprised of skin?
16%
How thick is our skin?
0.5-4mm thick
How large is the surface area of our skin?
2m^2
What is the integumentary system divided into?
- Cutaneous Membrane (skin)
2. Accessory structures
What is the integumentary system connected to?
- CVS
2. NVS
What are the functions of skin?
- physical protection from environmental hazards
- storage of lipids
- thermoregulation
- excretion
- sensory info
- production of melanin & keratin
- synthesis of vit D
- coordination of immune response
What does the cutaneous membrane comprise of?
- Outer Epidermis (Superficial Epithelium)
2. Inner Dermis
What do accessory structures comprise of?
- Hair Follicles
- Exocrine Glands
- Nails
Is there an additional layer beneath the cutaneous membrane?
Yes, it is the Superficial Fascia called the Hypodermis (Subcutaneous Layer)
What is the clinical significance of the Hypodermis?
It is the location for hypodermic injections as the hypodermis has blood vessels
What is the Hypodermis made up of?
LOOSE connective tissue
What is the function of the Epidermis?
- Protects dermis
- Prevents water loss & entry of pathogens
- Synthesises Vit D
- Contain Sensory Receptors
What is the function of the Dermis?
- (Papillary) Nourishes & supports epidermis
- (Reticular) Thermoregulation via Blood Vessels
- (Reticular) Contain Sensory Receptors which detect vibration additionally
What is the Epidermis made up of?
Epithelial Tissues
What is the Dermis made up of?
Connective Tissues
Where do accessory structures originate?
Dermis
Why is the Epidermis a Stratified Squamous Epithelium?
Helps diffuse nutrients and oxygen from the capillaries in the dermis
What are the cells of the Epidermis?
Keratinocytes are the most abundant
What is Thin Skin?
It covers MOST of the body and contains 4 layers of keratinocytes (x Stratum Lucidum)
What is Thick Skin?
It covers the palms of then hands and the soles of the feet and contains 5 layers of keratinocytes
What are the strata of Thick Skin?
- Stratum Corneum
- Stratum Lucidum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale
How is the Stratum Basale attached to the basement membrane?
By hemidesmosomes
What are the functions of the Stratum Basale?
- Forms strong bond between epidermis & dermis
2. Contains Epidermal Ridges (Fingerprints)
Where is the Stratum Basale?
Next to Dermal Papillae in Dermis
What are the cells of the Stratum Basale?
- Basal cells (germinative cells)
What are the functions of the Dermal Papillae?
- Strengthen attachment between Epidermis & Dermis
2. Increase area of Basement Membrane
What are the Specialised Cells of the Stratum Basale?
- Tactile Cells (Merkel Cells) - with sensory nerve endings, respond to touch, found in hairless skins
- Melanocytes which contain the pigment melanin
What is the Stratum Spinosum produced by?
Division of the Stratum Basale
How many layers of keratinocytes bound by desmosomes are there in the Stratum Spinosum?
8-10
Why is the Stratum Spinosum called the ‘spiny layer’?
Cells appear spiny
What cells make up the Stratum Spinosum?
Dendritic (Langerhans) cells that are active in immune response
What is characteristic of the cells in the Stratum Spinosum?
They continue dividing to increase the thickness of the epithelium
How many layers of keratinocytes are there in the Stratum Granulosum?
3-5
What is characteristic of the cells in the Stratum Granulosum?
Most cells stop dividing and produce Keratin (tough fibrous protein that makes up hair and nails) and Keratohyalin (dense granules that cross-link keratin). They die upon producing the proteins.
Where is the Stratum Lucidum only found?
In thick skin
What is the function of the Stratum Lucidum?
Covers the Stratum Granulosum
What is the Stratum Corneum?
Exposed surface of skin that is water resistant
How many layers of keratinocytes are there in the Stratum Corneum?
15-30
How long does it take for new cells to move from the Basal layer to the Horn layer?
7-10 days
When do exposed cells shed?
After 2 weeks
What is Keratinisation?
Formation of a layer of dead, protective cells filled with keratin (formation of many tough, waterproof layers)
Where does Keratinisation occur?
On all exposed skin surfaces except the eye
What is Acne?
Disorder in the keratinisation of the skin that leads to the presence of comedones (blackheads & whiteheads)
How is water lost from the skin?
- Insensible perspiration (Diffusion of water across the Stratum Corneum before it evaporates from the skin)
- Sensible perspiration (Water excreted by sweat glands in hot environment or during exercise)
What is Epidermal Growth Factor (EGF)?
Powerful peptide growth factor used in labs for growth of skin grafts
How is EGF produced?
By glands (salivary & duodenum)
What are the functions of EGF?
- Promote division of germinative cells
- Accelerate keratin production
- Stimulate epidermal repair
- Stimulate glandular secretion
