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What are the three major regions of the integumentary system?
Epidermis
Dermis
Hypodermis
Describe the epidermis
Outermost superficial region, made of stratified squamous
Describe the dermis
Middle region, made of connective areolar/dense irregular
Describe the hypodermis. What is its function?
Deepest region, made of adipose tissue, provides protection
Is the epidermis keratinized or non-keratinized?
Keratinized (stratified squamous)
How many layers is the epidermis made of?
4-5 layers
What 4 cell types make up the epidermis?
Keratinocytes
Melanocytes
Merkel cells
Langerhans’ cells
Describe the function of keratinocytes
Produce the fibrous protein keratin
Describe the function of melanocytes
Produce the brown pigment melanin
Describe the function of Langerhans’ cells
Macrophages that help activate the immune system, can travel along the skin
Describe the function of Merkel cells
Act as touch receptors in association with sensory nerve endings
List the layers of the epidermis from bottom to top.
Stratum germinativum (stratum basale)
Stratum spinosum
Stratum granulosum
Stratum corneum
Describe the stratum germinativum
Deepest level of the epidermis, attached to the dermis, single row of keratinocytes that undergoes rapid division
Describe the stratum granulosum
Second highest level of the epidermis, produce keratin, drastic changes in the keratinocytes occur
Describe the stratum spinosum
Second lowest level of the epidermis, where the nucleus of the disintegrates, and a chain forms, webs begin to attach to desmosomes
Describe the stratum corneum
Top layer of the epidermis, comprised of dead cells joined by tight junctions, and desmosomes; waterproof, protect, insensitive
Describe the stratum lucidum
Thick layer of skin apart of the epidermis only found in the palms and soles
What are the two layers of the dermis?
Top: papillary
Bottom: reticular
What is the papillary layer comprised of?
Areolar connective tissue (elastic and collagen)
What are dermal papillae?
Peg-like projections on its superior surface
What can the dermal papillae contain?
Capillary loops
Meissner’s corpuscles
Free nerve endings
What are Meissner’s corpuscles responsible for?
Sensing gentle touch
What is the reticular layer comprised of?
Dense irregular, adds stretchiness, strength and resiliency to skin
What layer makes up 80% of the skin?
The reticular layer
What is the hypodermis also known as?
The subcutaneous layer
What is the hypodermis composed of?
Adipose and areolar connective tissue
What are the three types of pigments that contribute to skin color?
Melanin
Carotene
Hemoglobin
Describe melanin
Yellow to reddish-black pigment, freckles and moles result from local accumulations of melanin
Describe carotene
Yellow to orange pigment, most obvious in the palms and soles of feet
Describe hemoglobin
Reddish pigment responsible for the pinkish hue of the skin
What are merocrine glands?
Gland responsible for electrolyte secretion (sweat), cools body to maintain a certain temperature
What are eccrine glands?
Sweat glands found in palms, soles of feet, and forehead
What are apocrine glands?
Sweat glands found in the armpits and groin responsible for release of sexual hormones
What are ceruminous glands?
Modified apocrine glands in the external ear canal and secrete cerumen
What are mammary glands?
Specialized sweat glands that secrete milk
What is a nociceptor?
A sensory nerve the detects pain
What are Pacinian corpuscles?
A sensory nerve responsible for sensing deep pressure
What are sebaceous glands?
Oil producing glands typically attached to hair follicles, secrete sebum, also known as holocrine glands
What is a hair follicle?
The lumen where hair strands grows out of
What is the hair bulb?
The base of the hair strand where cells divide, has a blood supply to provide oxygen
What kind of skin layers make up a hair follicle?
Stratum corneum transitions into stratum germinativum as it enters the lumen
What is the hair strand made of?
Near the bulb it is made of non-keratinized squamous and transitions to keratinized squamous into dead cells