Integumentary System Flashcards
What are the functions of the integumentary system?
- Protect against physical, chemical & biological insults (e.g. bacteria/virus)
- Water proof barrier (both ways - in & out)
- Absorb UV radiation (lessen impact)
- Excretion & thermoregulation
- Sense the external environment (external stimulus)
- Synthesis of vitamin (esp. Vit D) & pigments (e.g. melanin)
What % of adult body weight is skin?
15%
Largest organ in body
What is skin?
Cutaneous membrane the forms the external body surface
What are the two main layers of skin?
- Epidermis
- Dermis
What is Epidermis?
Ectodermally derived epithelial tissue
Outer layer
What is Dermis?
Mesodermally derived connective tissue
Inner layer
What is the basement membrane?
AKA Epidermo-dermal junction
Separates epidermis from dermis
What is the hypodermis?
Subcutaneous layer of fascia (superficial fascia - loose connective tissue) & fat
Below the Dermis
What are some accessories found in skin?
In the Epidermis: Glands, Hair, Nails
In the Dermis: Smooth muscle, Bld. vessels, lymphatics, sensory organs
What accessories are found in the epidermis?
Glands
Hair
Nails
What accessories are found mainly in the dermis and some in the hypodermis?
Blood vessels
Smooth muscle
Lymphatics
Sensory organs
What are the two types of skin?
Hairy skin (aka ‘thin’ skin)
Glabrous skin (aka ‘thick’ skin)
What is present in hairy skin?
Hair & certain types of glands
(‘thin’ skin)
What is NOT present in hairy skin?
Encapsulated sense organs in the dermis X present
(‘thin’ skin)
BUT have free nerve endings
Where is hairy skin usually found?
Most regions of the body EXCEPT palms & soles
(‘thin’ skin)
Is the epidermis in the hairy skin or in the glabrous skin thinner?
Epidermis in hairy skin is thinner
Where is glabrous skin usually found?
Confined to palms & soles; fingertips & toes
(‘thick’ skin)
What is present in glabrous skin?
Encapsulated sense organs in the dermis are present (more sensitive)
(‘thick’ skin)
What is not present in the glabrous skin?
Lack of hair & certain types of glands
(‘thick’ skin)
What characteristic does glabrous skin have?
Furrows & ridges
Caused by the basement membrane - very wavy & causes the indentions that make up our fingerprints (e.g.)
= Dermatoglyphics (study of ridges on our skin - e.g. fingerprints for forensic science)
Are there blood vessels in the epidermis?
No bld vessels but have nerve endings
O2 & nutrients diffuses from bld vessels in the dermis through the basement mbn (vv thin)
Is hair derived from the epidermis, the dermis or the hypodermis?
Derived from the epidermis (even though it dips into the dermis & hypodermis)
What is the stratum basale?
Single layer of cuboidal/columnar epithelium
Cells attached to (sitting on) the basement mbn
What are the cells that make up the stratum basale?
Keratinocytes
Stem cells
Melanocytes
Merkel cells
What is the stratum spinosum?
Thickest layer of the epidermis
Several layers of spiny keratinocytes
In each layer, cells attached to each other by desmosomes (cellular ‘cement’)
What are the individual layers of the epidermis? (5 layers)
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- [Stratum lucidum - only in ‘thick’ skin]
- Stratum corneum
What do the keratinocytes in the stratum spinosum produce?
Keratin
Keratin filaments are called tonofilaments = very tightly bound tgt (bundles of filaments)
What is the stratum granulosum?
A few layers of keratinocytes containing granulosomes
Basically keratin becomes dominant component & cells start to lose organelles)
Lamellar Granules: contain lipid-like substances
Cells start to die
What happens when the cells start to die in the stratum granulosum? (with regards to the lamellar granules)
Lamellar granules secrete the lipid-like substances within = these substances are deposited = act like the waterproof barrier (prevents H2O from evaporating from deeper layers & H2O enter)
What is the stratum corneum?
Thick layers of dead keratinocytes
Cross-linked keratins dominate these layers
What is the stratum luciderm?
It is only found in ‘thick’ skin!
Located between the stratum granulosum & stratum corneum
A few layers of keratinocytes that appear ‘clear’ (therefore named luciderm)
This clear appearance is due to the protein eleidin
What is hair made of?
Dead epidermal cells that have been converted to keratin
How does hair growth occur?
When cells in the hair matrix (base of bulb) divide & push upwards
When the cells reach the surface (shaft), they have been completely converted to keratin
What are always seen with hair?
Sebaceous gland
Smooth muscle (sebaceous gland sits on the smooth muscle - arrector pili muscle)
How is acne caused?
Sex hormones (esp androgen) stimulates the sebaceous gland
Overstimulation (hyperstimulation) can lead to blockage of outlet in hair follicle
What are nails made of?
Dead epidermal cells that have been converted into keratin
Derived from the epidermis