Ch.5 Skin Flashcards
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Skin
- last for life
- Waterproof,
- stretchable
- washable
- if damaged can repair itself
- Largest organ
- Weighs 9 -11 pounds
- Average 1-2 mm thick (ranges 1.5 – 4 mm)
What are the four ways that skin is a barrier?
- Protection barrier
- chemical barrier
-melanin prevents UV light from damaging DNA
- bacteriocides & acids inhibit microbial growth
- lipids prevent dehydration & make us waterproof d. keratin prevent abrasions, resists chemicals - physical barrier
- tight junctions inhibit microbial entry - biological barrier
- contains immune cells
Skin Functions
-Temperature regulation= sweat & dermal blood flow
- Sensory reception
- Vitamin D production= UV light converts cholesterol to a form of vitamin D
- Blood reservoir= 5% of blood
- Excretion= waste products with sweat
Epidermis
- top layer of skin
- keratinized stratified squamous epithelium
Four types of cells: - Keratinocytes
- Melanocytes
- Langerhans
- Merkel cells
4-5 distinct layers: - strantum corneum
- stratum lucidum
- stratum granulosum
- strantum spinosum
- stratum basale
Keratinocytes
Epidermis cell
- most abundant
- produce keratin (fibrous protein, that protects from heat,
microbes, and chemicals) - produce lamellar granules (waterproofing)
- arise by mitosis from basal layer and pushed to apical surface
- at apical surface they are dead cells full of keratin
- shape changes from cubodial to squamous
- life span ~ 40 days
Melanocytes
Epidermis cell
- reside in the basal layer
- have projections (processes) that are in contact with
surrounding keratinocytes - produce melanin and ship it to keratinocytes (keratinocytes cap their nucleus to shield DNA from UV light
- Note: melanin + carotene (vit.A) + hemoglobin contribute to skin color
Langerhans
Epidermis cell
- Reside primarily in middle layers
- WBC’s (migrate from bone marrow to skin)
- Function in phagocytosis & initiation of immune reactions
Merkel cells
Epidermis cell
- Reside in basal layer
- Involved in touch reception
stratum corneum (horny layer)
- top layer of epidermis
- Many layers (20-30)
- Dead, flat keratinocytes full of keratin
- Glycolipids between cells for waterproofing
- Continuously sloughed off
stratum lucidum (clear layer)
second top layer of epidermis
- Extra layers of keratinocytes in thick skin
stratum granulosum (granular layer)
- middle layer of epidermis
- keratinocytes
- Flattening
- Organelles disintegrating, cells dying
- Pre-keratin converting to keratin
- Lamellar granules accumulate (secrete waterproofing lipids into spaces between cells)
- Some Langerhans cells
stratum spinosum (prickly layer)
- second to last bottom layer of epiderms
- Several layers of cells
- Keratinocytes with pre- keratin filaments
- Langerhans (epidermal dendritic cells)
stratum basale (basal layer)
- bottom layer of epidermis
- 1 layer of cells:
- Cubiodial, mitotic keratinocytes
- Melanocytes
- Merkel cells
- some Langerhans
Dermis
- second layer of the skin under the epidermis
- Strong, flexible connective tissue
- Cells include fibroblasts, macrophages, mast cells and white blood cells
- “Hide” (animal hides used to make leather products)
Two sublayers: - Papillary
- Reticular
Papillary region
- top sublayer of the dermis
- Areolar connective tissue
- Contains dermal papillae with capillary loops and touch receptors
- On palms and soles deeper dermal ridges cause overlying epidermal ridges
Reticular region
- bottom sublayer of dermis
- Dense irregular connective tissue
- Adipose, glands, receptors
- Provides the skin’s extensibility and elasticity
Hypodermis
- underneath dermis
- (subcutaneous layer)
- Not part of skin –> Anchors skin to underlying tissue
- Areolar & adipose connective tissue
- Stores fat to insulate the body from heat loss
Hair
- Color= melanocytes at follicle base
- Functions= protection (heat loss and initiate reflexes)
- Found on all skin except palmar and plantar surfaces, lips, and genitals
- Dead keratinized cells
- Tough, durable, cells do not flake off
Nails
- Function = protection, scratching, grasping
- Structure = body, free edge, root
3 types of skin glands
- sudoriferous
- ceruminous
- sebaceous
Sudoriferous Glands
Type of skin gland
- sweat glands
- simple,tubular glands
- sweat = water, ions, waste
- Two Types: eccrine & apocrine
eccrine
Skin Gland –> Sudoriferous Glands –> Eccrine gland
- Located over most of body, especially on forehead, palms, soles
- Duct opens into skin surface
Apocrine
Skin Gland –> Sudoriferous Glands –> apocrine
- Primarily in axilla, groin
- Duct opens into hair follicle
- Sweat contains lipids & proteins
Ceruminous
Type of skin gland
- wax glands
- modified apocrine sweat glands located in ear canal
- secretion is waxy
- Function: protection
Sebaceous Glands
Type of skin gland
- oil gland
- simple alveolar glands
- holocrine
- duct into hair follicles
- found all over except on soles and palms
- Function = soften & lubricates hair and skin, antibacterial
Burns
- first degree = only epidermis is affected should heal on own
- second degree = epidermis + upper dermis is affected blisters, painful
- third degree = epidermis + whole dermis affected may look white, red, or black not painful (receptors are gone)
f luid loss & infection are a major concern
Types of Skin Cancer
- Basal cell carcinoma
- Squamous cell carcinoma
- Malignant melanoma
Basal cell carcinoma
basal layer keratinocytes divide and invade dermis, usually not malignant
Squamous cell carcinoma
spiny layer keratinocytes divide tends to metastasize (spreads) to lymph nodes
Malignant melanoma
cancer of melanocytes often develops at
the site of moles rapidly metastasize to lymph nodes and blood vessels,
use the ABCD rule
Melanoma ABCD Rule
- A = Asymetry
- B = Border irregularity
- C = Color
- D = Diameter
