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Questions and Answers
Which layer of the skin is avascular?
Which layer of the skin is avascular?
The dermis is located above the epidermis and is avascular.
The dermis is located above the epidermis and is avascular.
False
What is the main function of melanocytes in the skin?
What is the main function of melanocytes in the skin?
To produce melanin, which protects against UV light.
The epidermis is composed largely of _________ stratified squamous epithelium.
The epidermis is composed largely of _________ stratified squamous epithelium.
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Match the following skin functions with their descriptions:
Match the following skin functions with their descriptions:
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What is the primary function of hair in relation to the body?
What is the primary function of hair in relation to the body?
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Basal cell carcinomas are the most common type of skin cancer.
Basal cell carcinomas are the most common type of skin cancer.
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What layer of hair is considered the deepest?
What layer of hair is considered the deepest?
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Hair protects the scalp from _____ radiation.
Hair protects the scalp from _____ radiation.
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Which layer of the hair consists of flat keratinized epithelial cells?
Which layer of the hair consists of flat keratinized epithelial cells?
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Match the type of skin cancer with its description:
Match the type of skin cancer with its description:
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Melanin secretion is responsible for the differential colors of human skin.
Melanin secretion is responsible for the differential colors of human skin.
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What part of the hair allows for hair growth?
What part of the hair allows for hair growth?
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Which layer of skin contains stem cells responsible for replenishing overlying strata?
Which layer of skin contains stem cells responsible for replenishing overlying strata?
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The stratum lucidem is found in all skin types.
The stratum lucidem is found in all skin types.
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What are the two regions of the dermis?
What are the two regions of the dermis?
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The epidermis consists of _____ strata in most body areas.
The epidermis consists of _____ strata in most body areas.
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What is the main function of the stratum corneum?
What is the main function of the stratum corneum?
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Match the layers of skin with their symbolic function:
Match the layers of skin with their symbolic function:
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Melanocytes produce melanin in response to UV exposure.
Melanocytes produce melanin in response to UV exposure.
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Fingerprints are formed by the shape of _____ papillae.
Fingerprints are formed by the shape of _____ papillae.
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What process do cells in the stratum granulosum undergo?
What process do cells in the stratum granulosum undergo?
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What is the main role of keratin in the skin?
What is the main role of keratin in the skin?
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The dermis resists _____ and shear.
The dermis resists _____ and shear.
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The stratum spinosum is comprised of dead cells.
The stratum spinosum is comprised of dead cells.
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What contributes to the variation in skin color among humans?
What contributes to the variation in skin color among humans?
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What role do lamellar granules play in the skin?
What role do lamellar granules play in the skin?
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A tan fades when the skin is replaced by cells that have less _____ production.
A tan fades when the skin is replaced by cells that have less _____ production.
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Study Notes
The Integumentary System
- Includes the skin, hair, nails, associated oil and sweat glands, and sensory receptors
- Skin is the largest organ in the body, constituting approximately 7% of body weight
- Skin thickness varies from 0.5 mm on eyelids to 4 mm on heels
- The epidermis is the superficial layer of the skin and is avascular
- The dermis, found deep to the epidermis, is made of connective tissue and is vascularized
- The subcutaneous layer, or hypodermis, anchors the skin to the fascia and contains pressure receptors
Functions of the Integumentary System
- Regulate body temperature
- Protect the body from external insults
- Sense signals
- Excrete and absorb chemicals
- Store blood and energy
- Synthesize vitamin D
The Epidermis
- The epidermis is composed of keratinized stratified squamous epithelium
- Contains several cell types:
- Keratinocytes: layered cells that produce keratin and lamellar granules (waterproof sealant)
- Melanocytes: contain melanin granules; melanin is a brown-black pigment that absorbs UV light and protects DNA
- Intraepidermal macrophages (Langerhans cells): UV-sensitive phagocytes that engulf and destroy invaders through phagocytosis
- Tactile epithelial cells: sense touch and are in direct contact with tactile discs (nervous tissue)
- The epidermis is subdivided into strata (layers of keratinocytes of differing maturity)
- Most of the body is covered in skin consisting of four strata
- High abrasion areas (palms and soles) have five layers of skin
Strata of the Epidermis
- Stratum basale: deepest layer; contains stem cells capable of dividing to replenish overlying strata; rich in keratin intermediate filaments (IFs) that provide a strong foundation and reinforce cell junctions (desmosomes and hemidesmosomes)
- Stratum spinosum: provides strength to the skin; 8-10 layers of flat keratinocytes with thicker, tougher keratin IFs; reinforced desmosomes; fewer cells capable of division
- Stratum granulosum: seals the epidermis and contains dying cells; 3-5 layers of cells undergoing apoptosis; organelles disintegrate, keratin filaments persist; produces keratohyalin (aids in keratin IF assembly) and lamellar granules (contain lipids that seal the underlying layers from invasion and fluid loss)
- Stratum corneum: most superficial layer; "thin" skin has 4 strata; flat, thin cells stacked in overlapping fashion; cells are dead and slough off with abrasion; replenished by division from the stratum basale
- Stratum lucidum: only found in thick skin; found between the stratum granulosum and the stratum corneum; appears clear; made of dead, flat keratinocytes with thick keratin filaments and plasma membranes; provides additional mechanical support
Growth of the Epidermis
- Takes 4-6 weeks for new cells at the stratum basale to emerge at the stratum corneum
- Keratinization reinforces skin by leading to the accumulation of keratin in cells that die by apoptosis
- Cells farther from the stratum basale have decreased access to nutrients
The Dermis
- The dermis is made of connective tissue and has great tensile strength
- Consists of two regions:
- Papillary region: made of areolar connective tissue with collagen and elastic fibers; dermal papillae are tissue extensions from the dermis into the epidermis containing capillaries and nervous tissue that sense touch and pain; top 20% of the dermis
- Reticular region: made of dense irregular connective tissue; consists of a mesh-like network of thick collagen fibers with fibroblasts and other cells; resists stretching and shear; contains glands, nerves, and blood vessels; anchors the dermis to the subcutaneous layer; bottom 80% of the dermis
Fingerprints
- Formed by epidermal ridges on thick skin
- Unique to each individual and even differ between identical twins
- Actually the shape of the dermal papillae
- Increase friction to aid grip and surface area for touch sensing
- Sweat pores open on the surface
Structural Basis for Human Skin Color
- Human beings exhibit a diverse array of skin colors
- Everyone has approximately the same number of melanocytes but cells secrete different amounts of melanin
- Accumulation of melanin can appear as freckles, age spots, or nevuses (moles)
Tanning
- Melanocytes contain tyrosinase, which assists melanin synthesis
- Tyrosinase activity increases upon UV light exposure
- A tan fades as the skin dies and gets replaced by cells that have less melanin production
Skin Color Depth
- "Dark" skin ranges from yellow to black
- "Light" skin has lower levels of melanin, leading to translucent skin where red/pink from hemoglobin in blood is visible
- The stratum corneum stores carotene, giving an orange hue; excess can be deposited in the skin
Tattoos
- Tattoos use specialized needles to penetrate the dermis and deposit ink
- Tattoo removal works by using laser treatment to destroy pigmented cells, leading to phagocytosis of cell debris
Accessory Structures of the Skin
- Hair, glands, and nails
Hair
- Protects and insulates the body and helps sense stimuli
- Found on the scalp, eyebrows, eyelashes, nasal cavity, axillae, and external genitalia of both sexes
- Protects the scalp from UV radiation, the eyes and nasal cavity from invasion
Functions of Hair
- Traps air close to the skin to minimize heat loss
- Touch receptors connected to hair movement
Anatomy of a Hair
- Consists of a hair root (embedded in the dermis or subcutaneous layer) and a hair shaft (superficial portion)
- Both root and shaft consist of three layers:
- Medulla: deepest layer containing pigmented cells
- Cortex: makes up the bulk of hair
- Cuticle: most superficial layer made of flat keratinized epithelial cells arranged like roof shingles
- Hair follicle surrounds the outside of hair roots:
- External layer is made of epithelial tissue
- Internal layer makes up the hair matrix and divides continuously to permit hair growth
Hair and Associated Structures
- Hairs interact with smooth muscle called arrector pili
- Under specific conditions (cold, fear), arrector pili pull hair upright, causing "goosebumps"
Nails
- Found at the tips of fingers and toes
- Protect the ends of digits
- Aid in grasping and picking up small objects
- Composed of hard, keratinized epithelial cells
Glands
- Sebaceous glands: secrete sebum (oil) to lubricate hair and skin
- Sweat glands: secrete sweat (water, salts, and urea) to regulate body temperature and remove waste
Skin Cancer
- Can result from excessive UV exposure
- Involves uncontrolled proliferation of epithelial cells
- Three major types:
- Basal cell carcinomas: involve cells in the stratum basale; most common type (78%) and generally benign
- Squamous cell carcinomas: involve cells in the stratum spinosum; represent 20% of skin cancers
- Malignant melanomas: cancers of melanocytes; most dangerous type of skin cancer
Wound Healing
- An essential part of maintaining integumentary homeostasis
- Involves various stages:
- Inflammation: characterized by redness, swelling, pain, and heat
- Proliferation: new tissues are formed
- Remodeling: wound contracts and strengthens
Burns
- Can lead to life-threatening complications, including edema and sepsis
- Classified according to depth of tissue damage:
- First degree burns: only the epidermis is damaged
- Second degree burns: damage to the epidermis and dermis
- Third degree burns: damage to all layers of the skin, including subcutaneous tissue
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Description
Explore the intricacies of the integumentary system, including its structures like skin, hair, and nails. Learn about the functions it serves such as temperature regulation and protection. This quiz delves into the various layers of the skin and their respective roles.
