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Questions and Answers
What is the largest organ of the body?
The epidermis is vascularized and contains blood vessels.
False
What are the main functions of the integumentary system?
Regulate body temperature, protect the body, sense signals, excrete and absorb chemicals, store blood and energy, synthesize vitamin D.
The deep layer of skin, which is made of connective tissue, is known as the _________.
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Match the cell types found in the epidermis with their functions:
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What is NOT a function of hair?
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The cuticle is the deepest layer of the hair structure.
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What part of the hair is embedded in the dermis or subcutaneous layer?
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Hair consists of three layers: the _____, cortex, and cuticle.
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Which type of skin cancer is the most common?
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Match the following types of skin cancers with their characteristics:
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The arrector pili muscle is associated with hair and causes it to stand when cold or frightened.
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What is the main pigment responsible for human skin color?
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What is the main function of tactile epithelial cells?
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The epidermis consists of five strata in most areas of the body.
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What layer of the epidermis contains stem cells capable of dividing?
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The stratum granulosum seals the epidermis and contains dying cells undergoing __________.
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In which layer of the skin would you find the most superficial layer with dead cells?
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The dermis consists of only adipose tissue.
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What type of connective tissue is found in the reticular region of the dermis?
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Fingerprints are shaped by the __________ papillae.
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Match the following terms with their descriptions:
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How long does it take for new cells at the stratum basale to emerge at the stratum corneum?
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Everyone has a different number of melanocytes in their skin.
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What causes a tan to fade?
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The top 20% of the dermis is called the __________ region.
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Why don't tattoos fade like tans?
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What is the function of the stratum lucidum?
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Study Notes
Integumentary System Overview
- Includes skin, hair, nails, associated glands and sensory receptors
- Skin is the largest organ, comprising 7% of body weight.
- Skin thickness varies: 0.5 mm on eyelids, 4 mm on heels.
- Skin layers: epidermis (avascular), dermis (vascularized), and subcutaneous layer (hypodermis).
- Subcutaneous layer anchors structures to fascia and contains pressure receptors.
Integumentary System Functions
- Regulates body temperature.
- Protects the body from external insults.
- Senses signals.
- Excretes and absorbs chemicals.
- Stores blood and energy.
- Synthesizes vitamin D.
Epidermis
- Composed of keratinized stratified squamous epithelium.
- Contains various cell types:
- Keratinocytes: layered cells producing keratin and waterproof sealant.
- Melanocytes: contain melanin granules, absorbing UV light to protect DNA.
- Intraepidermal macrophages (Langerhans cells): engulf and destroy invaders through phagocytosis.
- Tactile epithelial cells: sense touch, in contact with tactile discs.
- Subdivided into strata (layers of keratinocytes with varying maturity).
- Most of the body has four strata, while palms and soles have five.
Epidermis Strata
- Stratum basale: deepest layer, contains stem cells replenishing overlying strata, rich in keratin intermediate filaments, provides strong foundation for skin.
- Stratum spinosum: provides strength to skin, contains thicker keratin intermediate filaments, reinforces desmosomes, fewer cells capable of division.
- Stratum granulosum: seals the epidermis and contains dying cells, produces keratohyalin (aids in keratin filament assembly) and lamellar granules (seals underlying layers, prevents fluid loss).
- Stratum corneum: most superficial layer, dead cells slough off with abrasion, replenished by division from the stratum basale.
- Stratum lucidum: found only in thick skin, between stratum granulosum and corneum, made of dead keratinocytes with thick keratin filaments, provides additional mechanical support to thick skin.
Dermis
- Made of connective tissue with great tensile strength.
- Divided into two regions:
- Papillary region: areolar connective tissue with collagen and elastic fibres, contains dermal papillae (tissue extensions from dermis into epidermis) which contain capillaries and nervous tissue for touch and pain sensing.
- Reticular region: dense irregular connective tissue, mesh-like network of thick collagen fibres, resists stretching and shear, contains glands, nerves, and blood vessels.
- Anchors the dermis to the subcutaneous layer.
Fingerprints
- Unique to each individual, even differing between identical twins.
- Formed by epidermal ridges, actually the shape of dermal papillae.
- Increase friction for grip and surface area for touch sensing.
Skin Color
- Caused by melanin secretion from melanocytes.
- Everyone has a similar number of melanocytes, but they secrete different amounts of melanin.
- Tanning: tyrosinase activity increases upon UV light exposure.
- Tanning fades as the skin dies and is replaced by cells with less melanin production.
Accessory Structures of the Skin
Hair
- Protects and insulates the body, assists in sensing stimuli.
- Found on scalp, eyebrows, eyelashes, nasal cavity, axillae, and external genitalia.
- Functions: traps air to minimize heat loss, touch receptors connected to hair movement.
- Hair consists of:
- Root: embedded in dermis or subcutaneous layer.
- Shaft: superficial portion of the hair.
- Root and shaft have three layers:
- Medulla: deepest layer, contains pigmented cells.
- Cortex: middle layer, makes up the bulk of the hair.
- Cuticle: most superficial layer, flat keratinized epithelial cells, arranged like roof shingles.
- Hair follicle surrounds the hair root:
- External layer: epithelial tissue.
- Internal layer: hair matrix, divides continuously for hair growth.
Glands
- Hair is associated with arrector pili (smooth muscle) which contracts in response to cold or fear, pulling hair from the follicle.
- Sweat glands (eccrine and apocrine) produce sweat for thermoregulation and waste excretion.
- Sebaceous glands: connected to hair follicles, produce sebum (oils) to lubricate the skin and hair.
Nails
- Formed from a hardened keratinized structure, produced by specialized epithelial cells.
- Provide protection and aid in grasping objects.
Wound Healing
- Essential for maintaining integumentary homeostasis.
- Involves repair by connective tissue and epithelial cells.
- Stages of wound healing: inflammatory response, migration and proliferation of cells, remodeling of connective tissue.
Burns
- Can lead to life-threatening complications such as edema and sepsis.
- Classified by depth of tissue damage:
- First-degree (superficial): only epidermis is affected.
- Second-degree (partial thickness): epidermis and dermis are affected.
- Third-degree (full thickness): all layers of skin are destroyed.
Skin Cancer
- Can result from excessive UV exposure.
- Types:
- Basal cell carcinomas: most common, cells in stratum basale, usually benign.
- Squamous cell carcinomas: 20% of skin cancers, cells in stratum spinosum, often malignant.
- Malignant melanomas: cancers of melanocytes, highly aggressive, prone to metastasis.
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Description
Explore the comprehensive functions and structures of the integumentary system, which includes the skin, hair, nails, and glands. Learn about the skin's layers, its role in temperature regulation, and its protective mechanisms against external threats.
