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Questions and Answers
What is the average time it takes for a Keratinocyte to move from the stratum germinativum to the stratum corneum?
What is the average time it takes for a Keratinocyte to move from the stratum germinativum to the stratum corneum?
What is the primary characteristic of insensible perspiration?
What is the primary characteristic of insensible perspiration?
Which pigment primarily gives skin its brown-black color?
Which pigment primarily gives skin its brown-black color?
Which skin condition is characterized by a yellowish tint due to bilirubin buildup?
Which skin condition is characterized by a yellowish tint due to bilirubin buildup?
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What result would immersion in a hypotonic solution have on the skin?
What result would immersion in a hypotonic solution have on the skin?
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What is the result of vasoconstriction as it relates to skin color?
What is the result of vasoconstriction as it relates to skin color?
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What protects the skin from sun damage by UV rays?
What protects the skin from sun damage by UV rays?
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What condition results from a deficiency of vitamin D in children?
What condition results from a deficiency of vitamin D in children?
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What role does the epidermal ridges and dermal papillae serve in the skin?
What role does the epidermal ridges and dermal papillae serve in the skin?
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What is a common characteristic of malignant melanoma?
What is a common characteristic of malignant melanoma?
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What is the primary role of keratinocytes in the epidermis?
What is the primary role of keratinocytes in the epidermis?
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How does the epidermis receive nutrients and oxygen?
How does the epidermis receive nutrients and oxygen?
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Which layer of the epidermis is known for being the 'grainy layer'?
Which layer of the epidermis is known for being the 'grainy layer'?
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What layer is ONLY found in thick skin?
What layer is ONLY found in thick skin?
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What percentage of body weight does the integumentary system represent?
What percentage of body weight does the integumentary system represent?
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What is the main function of the stratum germinativum?
What is the main function of the stratum germinativum?
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What type of cells are Langerhans cells?
What type of cells are Langerhans cells?
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What function do mammary glands have in the integumentary system?
What function do mammary glands have in the integumentary system?
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What is keratinization?
What is keratinization?
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Which skin type has a greater number of layers in the stratum corneum?
Which skin type has a greater number of layers in the stratum corneum?
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Which layer of the epidermis is made up of dead, flat keratinocytes filled with keratin?
Which layer of the epidermis is made up of dead, flat keratinocytes filled with keratin?
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What is the role of sensory receptors in the dermis?
What is the role of sensory receptors in the dermis?
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Which is a characteristic of the stratum spinosum?
Which is a characteristic of the stratum spinosum?
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Which of the following is NOT a function of the integumentary system?
Which of the following is NOT a function of the integumentary system?
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Study Notes
Integumentary System
- Largest system of the body, comprises 16% of body weight and 1.5 to 2 m2 of surface area
- Contains cutaneous membrane (skin) and accessory structures
Cutaneous Membrane
- Composed of outer epidermis (epithelium) and inner dermis (connective tissue)
- Epidermis lacks blood vessels and receives nutrients and oxygen from the dermis
Accessory Structures
- Derived from the embryonic epidermis.
- Include hair, mammary glands, ceruminous glands, and nails.
- Located in the dermis and project through the skin surface.
Blood & Nerve Supply
- Blood supply provided by blood vessels in the dermis.
- Nerve supply includes sensory receptors for pain, temperature, touch, and pressure.
Functions of the Integument
- Protects underlying tissues and organs
- Maintains body temperature through insulation and evaporation
- Excretes water, salts, and organic wastes
- Synthesizes vitamin D3
- Stores lipids
- Responsible for sensing pain, temperature, touch, and pressure
Epidermis
- Stratified squamous epithelium
- Avascular, receiving nutrients and oxygen through diffusion from dermal capillaries
- Contains keratinocytes, the most abundant cells, organized in layers and rich in keratin
Skin Types
- Thin skin: Found on most of the body, contains four layers.
- Thick skin: Found on palms and soles, contains five layers, including stratum lucidum.
Layers of the Epidermis
- Five layers of keratinocytes in thick skin, from basal lamina to free surface:
- Stratum germinativum (basale)
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
- Four layers of keratinocytes in thin skin:
- Stratum germinativum (basale)
- Stratum spinosum
- Stratum granulosum
- Stratum corneum
Stratum Germinativum (Basale)
- The "germinative layer", the most basal layer
- Consists of 1 - 3 layers of cells
- Contains numerous germinative (stem - basal) cells
- Attached to the basement membrane through hemidesmosomes
Cells of Stratum Germinativum
- Basal (germinative) keratinocytes: Dominant cells, responsible for replacing lost cells
- Merkel cells: Found in hairless skin, function as touch receptors
- Melanocytes: Produce melanin pigment and migrate from the dermis to the stratum germinativum of the epidermis
Stratum Spinosum
- The "spiny layer", produced through division of the stratum germinativum
- Contains 8-10 layers of keratinocytes bound by desmosomes
Cells of Stratum Spinosum
- Keratinocytes: Some divide, increasing epithelial thickness, appear spiny due to shrinking
- Langerhans cells: Dendritic cells acting as skin macrophages, involved in immune response as antigen-presenting cells
Stratum Granulosum
- The "grainy layer", contains 3-5 layers of keratinocytes
- Cells stop dividing and begin producing:
- Keratin: Tough, fibrous protein that covers the epidermis and forms hair and nails
- Keratohyalin: Dense protein granules that cross-link keratin fibers
Cells of Stratum Granulosum
- Keratinocytes: Do not divide, produce protein fibers, lose their nuclei and organelles, dehydrate and die, create tightly interlocked layer of keratin surrounded by keratohyalin
Stratum Lucidum
- The "clear layer", present ONLY in thick skin
- Contains 3-5 layers of keratinocytes
- Keratinocytes: Dead, flat, dense, and filled with keratin
Stratum Corneum
- The "horny layer", exposed surface of the skin
- 15 to 30 layers of keratinized dead cells
- Signficantly thicker in thick skin
- Water resistant
- Sheds and is replaced every two weeks
Keratinization (Cornification)
- Formation of a protective layer of dead cells filled with keratin
- Occurs on all exposed skin surfaces except the eyes
Skin Life Cycle
- It takes 15-30 days for a keratinocyte to move from the stratum germinativum to the stratum corneum.
Perspiration
- Elimination of fluid through skin pores
- Insensible perspiration: Interstitial fluid lost by evaporation through the stratum corneum, around 500 ml/day
- Sensible perspiration: Water (sweat) excreted by sweat glands, variable amount
Water Loss Through Skin
- Dehydration results from:
- Damage to the stratum corneum, such as burns and blisters (insensible perspiration)
- Immersion in hypertonic solutions, such as seawater (osmosis)
- Xerosis refers to dry skin
Water Gain Through Skin
- Hydration:
- Results from immersion in hypotonic solutions, such as freshwater (osmosis)
- Causes stretching and wrinkling of skin (e.g., when washing hands)
Skin Color (Complexion)
- Dependent on:
- Pigments:
- Carotene
- Melanin
- Blood circulation:
- Red blood cells
- Pigments:
Carotene
- Orange-yellow pigment
- Found in orange vegetables (carrots)
- Accumulates in epidermal cells and fatty tissues of the dermis
- Precursor of vitamin A
Melanin
- Brown-black pigment
- Produced by melanocytes in the stratum germinativum
- Stored in transport vesicles (melanosomes)
- Transferred to keratinocytes
- Skin color depends on melanin production, not the number of melanocytes
- Protects the skin from sun damage by UV rays
Freckles & Nevi
- Freckles: Small pigmented areas, mainly on the face, increase with sun exposure
- Nevus (mole): Benign melanoma
Capillaries & Skin Color
- Hemoglobin pigment in red blood cells contributes to skin color:
- Vasodilation: Red skin
- Vasoconstriction: Pale skin
- Pallor: Pale skin and mucous membranes, usually associated with anemia (low hemoglobin concentration)
Cyanosis
- Bluish skin discoloration
- Due to severe hypoxia (low blood oxygen)
- Causes:
- Extreme cold
- Cardiovascular disease
- Respiratory disease
Common Abnormal Skin Colors
- Jaundice: Yellow color, buildup of bilirubin pigment (hyperbilirubinemia)
- Vitiligo: Autoimmune disease, loss of melanocytes, resulting in loss of skin color
Skin & Vitamin D
- Epidermal cells produce cholecalciferol (vitamin D3) through exposure to UV radiation from sunlight
- The liver and kidneys activate vitamin D (calcitriol)
- Function: Enhances absorption of calcium and phosphorus from the intestine
Vitamin D Deficiency
- Children: Rickets
- Adults: Osteomalacia
Malignant Skin Tumors
- Basal cell carcinoma
- Squamous cell carcinoma
- Malignant melanoma
Epidermal Ridges & Dermal Papillae
- Strengthen the bond between epidermis and dermis
- Epidermal ridges: Formed by the stratum germinativum, create fingerprints
- Dermal papillae: Project through epidermal ridges, increase the area of basal lamina
Ridges, Ducts & Fingerprints
- Pores of sweat gland ducts open on the surface of epidermal ridges.
- Identical twins do not have identical fingerprints.
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Description
Test your knowledge of the integumentary system, comprising the skin and its accessory structures, including hair and nails. This quiz covers the functions, anatomy, and blood supply of the skin. Understand how the integument protects the body and maintains homeostasis.
