Chapter 5: Skin Flashcards
2 Major layers of the skin
Epidermis and dermis
Hypodermis/Subq layer: location + composition
located deep to dermis and composed of areolar and adipose tissue
4 major types of cells in the epidermis
- keratinocytes
- melanocytes
- dendritic/langerhans cell
- Tactile epithelial cells (merkel cells)
Keratinocytes
- contains intermediate filament called keratin
- provide strength and protection
- are water repellent
- 85% of epidermal cells are keratinocytes
Melanocytes
- produce pigment
- their long slender projections extend between keratinocytes and transfer melanin granules
Dendritic cells
- their role in the immune response is to help other cells of the immune system recognize an invading microbe and destroy it
Tactile epithelial cells (merkel cells)
- detect touch sensations through non-encapsulated sensory corpuscle or merkel disc
- located in the deepest layer of the epidermis
(attached to sensory neuron)
Thin (hairy) skin covers…
all body regions except the palms, palmar surfaces of digits and soles
Thick (hairless) skin covers…
palms, palmar surfaces of digits, and soles. contains more layers of cells
The 4/5 layers of thick/thin skin
- stratum basale - deepest
- stratum spinosum
- stratum granulosum
- stratum lucidum (only present in thick skin)
- stratum corneum (most superficial layer)
Stratum basale
- deepest layer of the epidermis (closest to blood vessels)
- consist of single row of cuboidal or columnar cells
- stem cells undergo cell division to produce new keratinocytes (active mitosis)
- melanocytes and tactile epithelial cells associated with tactile discs are scattered among keratinocytes
connects to basement membrane (hemidesmosomes)
Stratum spinosum
- 8-10 rows of many-sided kertinocytes
- keratinocytes contain coarser bundles of keratin intermediate filaments
- ^ provides strength and flexibility to the skin
- desmosomes connect to cells and to intermediate filaments
- dendritic cells and melanocytes also present
Stratum granulosum
- middle of epidermis
- consists of 3-5 layers of flattened keratinocytes
- undergoing apoptosis (genetically programmed cell death)
- keratohyalin assembles keratin intermediate filaments into keratin
- lamellar granules release lipid rich, water repellant secretion
-transition between active and dead cells
Stratum lucidum
- present only in thick skin
- consists of 4-6 layers of clear, dead keratinocytes
Stratum corneum
- consists of 25-50 layers of flattened dead keratinocytes
- cells are continuously shed and replaced in this layer
- protects deeper layers from injury and microbial invasion
The dermis is composed of…
dense irregular connective tissue containing collagen and elastic fibers
The dermis can be divided into
thin superficial papillary dermis and thick deeper reticular dermis
Papillary dermis
- makes up 1/5th of thickness
- consists of areolar connective tissue with thin collagen and fine elastic fibers
- contains dermal papillae (nipple shaped structures) that contain capillary loops (blood vessels)
contain tactile corpuscles (meissner corpuscles) and nerve endings that are sensitive to touch
Reticular dermis
- deeper portion of the dermis (4/5ths)
- consists of dense irregular connective tissue with bundles of collagen and coarse elastic fibers
- space between fibers contain some adpose cells, hair follicles, nerves, sebaceous glands and sudoriferous glands
Where is melanin produced
in the stratum basale by melanocytes
Pheomelanin
yellow to red pigment
Eumelanin
brown to black pigment
Hair is composed of
dead keratinized epidermal cells
Parts of a hair
- the shaft
- the root
- the follicle
- hair bulb
The shaft of hair and it’s 3 parts
- superficial portion of hair
1. medulla- middle
2. cortex; surround medulla
3. cuticle of hair; hard protective layer
The root of hair and it’s 3 parts
- below the surface of the skin, penetrates dermis
1. medulla
2. cortex
3. cuticle of the hair
The follicle of hair and it’s components
- structure surrounding the root of the hair
1. internal root sheath; surround cuticle
2. external root sheath; surround internal root sheath
Hair bulb composes of
- papilla of the hair; nipple shaped production that provides blood supply
- hair matrix: dividing cells that form hair and
Stages of hair growth
- growth stage
- regression stage
- resting stage
Hair growth;Growth stage:
- cells of the hair matrix divide
- as new cells are added , existing cells of the hair root are pushed up, they become keratinized and die
Hair growth;Regression stage:
- movement of the hair away from the blood supply
- cells of the hair matrix stop dividing
Hair growth;Resting stage:
- old hair root falls out and regrowth begins
Lanugo
hair that covers the fetus
Terminal hair
long, course, heavily pigmented hairs (regular)
Vellus
short, fine, pale hairs. ex: on the arm
4 types of skin glands
- sebaceous (oil) glands
- Eccrine sweat glands
- Apocrine sweat glands
- Ceruminous glands
Sebaceous glands
- attached to hair follicles
- absent in palms
- secretes sebum
- prevents hairs and skin from drying out, prevents water loss from skin, inhibits growth of some bacteria
- located in lips, glans penis, labia minora, and tarsal glands; small in trunk and limbs
- activated during puberty
Eccrine sweat glands
- located throughout most skin regions; forehead, palms, and soles. Not present in lips, nail beds, glans penis and glans clitoris
- mostly in deep dermis excreted from epidermis
- secretes sweat (perspiration) - water, ions, urea, glucose, lactic acid
- regulates body temperature, waste removal, stimulated during emotional stress
- activated soon after birth
Apocrine sweat glands
- distributed at axilla, groin, bearded regions, labia minora
- mostly in deep dermis and upper subcutaneous layer
- excreted through hair follicles
- secretes perspiration which consists of same things as eccrine sweat glands plus lipids and proteins
- stimulated during emotional stress and sexual excitement
- activated at puberty
Ceruminous glands
- comes from external acoustic meatus
- located in subq layer and excretes at surface of auditory canal or into ducts of sebaceous glands
- secretes cerumen
- present soon after birth
- impedes entrance of foreign bodies and insects into external ear canal
What type of cells are nails made out of
keratinized epidermal cells
Components of nails
- free edge
- hyponychium
- nail plate/ body
- nail bed
- lunula
- eponychium (cuticle)
- nail root
- nail matrix
The skin attaches to the nail at the…
cuticle
Compare and contrast thick/thin skin
- thin lacks while thick has epidermal ridges
- thin has while thick lacks hair follicles
- thin has while thick lacks sebaceous glands
- thick has more numerous sudoriferous glands while thin lacks
- sensory receptors sparser on thin and denser in thick
Functions of the skin
- thermoregulation
- blood reservoir
- protection against microbes and abrasion
- cutaneous sensations
- excretion and absorption
- synthesis of vitamin D
The skin can hold what % of bloodflow while resting
8-10%
What components are responsible for protection of the skin
- keratin; protects from microbes, abraision, heat and chemicals
- lipids released prevent loss of water
- sebum: reduces bacteria
- melanin: protects against UV
- macrophages: eat bacteria by phagocytosis
Cutaneous sensations
- tactile sensations: touch, pressure, vibration, tickle
- thermal sensations: warm, cool
- pain
How is vitamin D synthesized in the skin
UV rays activate vitamin d to the active form (calcitriol)
What further modified vitamin d
enzymes in the liver and kidneys
Why is vitamin D important for our body
aids in the absorption of calcium and phosphorus from foods in the GI tract
Epidermal wound healing only occurs when…
superficial wounds affect only the epidermis. (no significant bleeding)
4 phases of deep wound healing
- inflammatory phase
- migratory phase
- proliferative phase
- maturation phase
Inflammatory phase
- clot forms
- inflammation: redness, swelling, heat, pain, immobility
- vasodilation occurs to allow wbcs to reach surface of wound
Migratory phase
- clot becomes a scab
- fibroblasts migrate and synthesize scar tissue
- damaged blood vessels begin to regrow
Proliferative phase
- growth of epithelial cells beneath scab
Maturation phase
scab sloughs off once epidermis restored
Age associated changes in skin
- wrinkles
- dry brittle nails
- decreased number of melanocytes, therefore white hair
- subq fat loss, skin thickness decreases
- sweat production decreases
- dehydrated and cracking skin
Warning signs of malignant melanoma
A: assymetry
B: border irregular
C: color uneven
D: diameter is greater than 6mm
E: evolving shape and size
What is a burn and it’s 3 severities
tissue damage caused by heat, electricity, radioactivity, or corrosive chemicals
1. first degree burn
2. second degree burn
3. third degree burn
First degree burn
- involves epidermis only
- mild pain and redness
- example: sunburn
Second degree burn
- destroys epidermis and part of dermis
- some skin functions are lost
- redness, blister, edema and pain
Third degree burn
- destroys epidermis, dermis and subq layers
- most skin functions are lost
- marked edema, numbness due to lost of sensory nerve endings
