the skin and its derivatives (sweat and oil glands, hairs, and nails) that make up a complex set of organs that serve several functions, mostly protective.
The five things that make up the integumentary system
skin, glands, nails, hair, cancer
Functions of the Integumentary system
1. Protection- chemical, physical, and mechanical barrier 2. body temperature- a. regulated by dilation (cooling) and constriction (warming) of dermal vessels b. sweat glands increase secretions to cool the body 3. metabolic functions- synthesis of vitamin D in dermal blood vessels 4. blood reservoir- skin blood vessels store up to 5% of the body's blood volume 5. excretion- limited amounts of nitrogenous wastes are eliminated from the body in sweat
What are cutaneous sensations
exoreceptors that sense touch and pain
What is another name for the skin?
What are the three major regions that the skin consists of?
What are the main things that the epidermis is composed of?
Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers.
What are the cell types of the epidermis?
keratinocytes, melanocytes, Merkel cells, and Langerhans' cells
The purpose of the epidermis that is exposed to the external environment is?
functions in protection
produce the fibrous protein keratin
produce the brown pigment melanin
epidermal macrophages that help activate the immune system
function as touch receptors in association with sensory nerve endings
Stratum Basale (Basal Layer of the epidermis)
deepest epidermal layer firmly attached to the dermis, consists of a single row of the youngest keratinocytes, cells undergo rapid division, hence its alternate name, stratum germinativum
Stratum Spinosum (Prickly Layer of the epidermis)
cells contain a weblike system of intermediate filaments attached to desmosomes, melanin granules and Langerhans' cells are abundant in this layer
junctions between the cells)
Stratum Granulosum (Granular Layer of the epidermis)
flattened; three to five cell layers in which drastic changes in keratinocyte appearance occurs. Organelles deteriorate. Keratohyaline and lamellated granules accumulate in the cells of this layer
Stratum Lucidium (Clear Layer of the epidermis)
thin, transparent band superficial to the stratum granulosum, consists of a few rows of flat, dead keratinocytes. ONLY PRESENT IN THICK SKIN!
Stratum Corneum (Horny Layer of the epidermis)
Outermost layer of keratinized cells, accounts for three quarters of the epidermal thickness, functions- waterproofing, protection from abrasion and penetration, renders the body relatively insensitive to biological, chemical, and physical assaults
Dermis region of the epidermis
contains areolar connective tissue, composed of two layers- papillary and reticular
Papillary layer of the dermis
its superior surface contains peg-like projections called dermal papillae
accounts for approximately 80% of the thickness of the skin, collagen fibers in this layer add strength and resiliency to the skin, elastin fibers provide stretch-recoil properties
Subcutaneous layer deep to the skin, composed of adipose and areolar connective tissue
What are the three pigments that contribute to skin color?
1. melanin, 2. carotene, 3. hemoglobin
yellow to reddish-brown to black pigment, responsible for dark skin colors; freckles and pigmented moles, result from local accumulations of melanin
yellow to orange pigment, most obvious in the palms and soles of the feet
reddish pigment responsible for the pinkish hue of the skin
What are the four appendages of the skin?
(derive from the epidermis) 1. sweat (sudoriferous) glands, 2. Sebaceous (oil), 3. Nails, 4. Hair
Four types of Sweat Glands: 1. eccrine (merocrine) 2. apocrine 3. ceruminous 4. mammary
Eccrine (merocrine) sweat glands
found in palms, soles of the feet, and forehead.
Apocrine sweat glands
found in axillary (armpits) and anogenital areas. Scent glands
modified apocrine glands in external ear canal and secrete cerumen
Mammary glands: specialized sweat glands that secrete milk
simple alveolar glands found all over the body
What do sebaceous glands secrete
secrete an oily secretion called sebum
What do sebaceous glands do?
soften skin when stimulated by hormones (androgens). It prevents water loss from the skin and acts as bactericidal
What does hair do?
helps maintain warmth, alters the body to presence of insects on the skin, and guards the scalp against physical trauma, heat loss, and sunlight
What is produced by hair follicles?
filamentous strands of dead keratinized cells
What does hair contain?
contains hard keratin, which is tougher and more durable than the soft keratin of the skin
What is hair made of?
made up of the shaft projecting from the skin and the root embedded in the skin
What does hair consist of
consists of a core called the medulla, a cortex, and an outermost cuticle
What gives hair its color?
pigmented by melanocytes at the base
Structure of a hair follicle
root sheath extending from the epidermal surface into the dermis, deep end forms a hair bulb, a knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb, bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors
Structure of a nail
scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes
Basal Cell Carcinoma
least malignant and most common skin cancer
What causes basal cell carcinoma?
Stratum basale cells proliferate and invade the dermis and hypodermis, slow growing and do not often metastasize
How can basal cell carcinoma be cured?
can be cured by surgical excision in 99% of the cases
Squamous cell Carcinoma
arises from keratinocytes of stratum spinosum
Where does squamous cell carcinoma most often occur? arise most often on scalp, ears, and lower lip
How does squamous cell carcinoma react?
grows rapidly and metastasizes if not removed
How is squamous cell carcinoma treated?
prognosis is good if treated by radiation therapy or removed surgically
cancer of melanocytes is the most dangerous type of skin cancer
What are the characteristics of melanoma?
(ABCD rule) A. asymmetry; the two sides of the pigmented area do not match, B. border is irregular and exhibits indentations C. Color (pigmented area) is black, brown, tan, and sometimes red or blue D. Diameter is larger than 6 mm (size of a pencil eraser)
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