Integument (Ch. 5) Flashcards
Skin
An organ (diff. tissues working together)
Largest organ in the human body system
7% of total body weight
What are the 6 functions of the skin?
- protect against mechanical damage
- barrier to fluid loss and pathogens
- vitamin D production
- sensory reception
- body temp regulation (sweating)
- excretion of salt/wastes
Epidermis
Keratinized stratified squamous epithelium
How many cell types are in the epidermis?
4 cell types
Does the epidermis have a blood supply?
No, it’s avascular
How often does the epidermis regenerate?
every 35-45 days
How many cell layers are in the epidermis?
4-5 layers (thin vs thick skin)
Epidermis: cells
- Keratinocytes: produce keratin, most abundant
- Melanocytes: produce melanin (helps shield nuclei of keratinocytes from UV radiation)
- Merkel cells: sensation
4: Dendritic cells: immune cells
Name all the layers of the Epidermis (from superficial to deep)
- Stratum Corneum
- Stratum Lucidum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale
Stratum Corneum
most superficial
dead cells full of keratin, shed regularly
Stratum Lucidum
“clear layer”
ONLY IN THICK SKIN
Consists of a few rows of flat, dead keratinocytes
Stratum Granulosum
1-5 layers of cells. Granules in this layer help waterproof skin
Stratum Spinosum
Multiple cell layers of keratinocytes.
ONLY LAYER WITH DENDRITIC CELLS
Stratum Basale
deepest layer, attached to dermis. Mostly keratinocytes w/ rapid division. Melanocytes and merkel cells
Dermis
Underlies epidermis Strong, flexible CT Highly vascularized Innervated (sensation) 2 cell layers - papillary (20%) and reticular (80%)
Does the Dermis have a blood supply?
Yes, it’s highly vascularized
Dermis: Papillary Layer
Papillary Layer ~ superficial 20%
Areolar CT
Provides nutrients to epidermis
Dermal Papillae increase surface area for transport of materials into epidermis
Dermis: Reticular Layer
80% of dermis
Mostly dense irregular [CT]
Network of collagen and elastic fibers provide stretch, strength
Hypodermis
Supports skin (epidermis and dermis)
Areolar and Adipose loose CT (mostly adipose)
–stores fat, provides insulation, anchors skin to muscles
Allows movement of skin over muscle and bones
List the 3 layers of the skin from superficial to deep
- Epidermis
- Dermis
- Hypodermis
Fingerprints
Dermal papillae push up and elevate the overlying epidermis (create epidermal ridges). Patterns are unique
Hair
flexible strands made of keratin
Pigment comes from melanocytes
Fxns: sensation (light touch), protection, insulation
Hair Structure:
Basic:
- -shaft (exposed)
- -root (embedded portion)
Hair Follicle:
- -bulb (innervation)
- -papilla (blood supply)
Arrector Pili Muscle
–contraction raises (erects hair), causes “goosebumps”
Sweat Glands
Can be eccrine (a form of merocrine gland) or apocrine
Eccrine Sweat glands
Secreted ONTO skin surface. Allows evaporative cooling
Development: invaginate from skin surface
Product: 99% water, 1% salts/wastes
Acidic; antibacterial properties
Apocrine Sweat glands
Discharge into hair follicles and NOT body surface
Development: outgrowths from hair follicles
Product: complex molecules, odorous
Found in armpits/genitals
Modified Sweat glands
Ceruminous: line external ear canal, produce earwax
Mammary: secrete milk
Sebaceous Glands
Multicellular exocrine glands
Open into hair follicles
Secrete sebum (oil):
–Holocrine secretion: cells accumulate sebum and burst to release product
Moisturize hair and skin
Blocked hair follicle –> acne
Skin Color - Melanin
Melanin acts as a natural sunblock, determines skin tone
Number of melanocytes does NOT vary among individuals; activity of melanocytes does
Not much melanin = decrease in folate levels
Skin Color and UV Rays
Some exposure to sunlight is essential
- -UV rays cause epidermis to produce vitamin D
- ->needed for calcium absorption
- ->light skin in northern climates (low sun) facilitates this)
But excessive exposure is dangerous
- -reduces folate levels needed for embryonic development
- -promotes skin cancer
Skin color affects amount of UV absorbed
–darker skin in tropical (high sun) environments reduces UV absorption, protects folic acid levels
Skin Cancer
Most common form of cancer
Basal cell carcinoma originates in the stratum basale (germinativum). Metastasis is rare
Melanoma is potentially life-threatening, because cancerous melanocytes grow rapidly and spread through the lymphatic system
ABCDE of Skin Cancer
A. Asymmetry: irregular shape B. Border: indistinct C. Color: mottled D. Diameter: > 5mm is dangerous E. Elevation: not flat
What’s the mnemonic for the 5 layers of the epidermis?
Come [Stratum Corneum] *Let's [Stratum Lucidum] Get [Stratum Granulosum] Sun [Stratum Spinosum] Burned [Stratum Basale]
*Only in thick skin
