Questions and Answers
What percentage of the body weight does the integument account for?
7% to 8%
What is the range of thickness of the integument?
1.5 mm to 4 mm or more
What is the outermost layer of the integument called?
Epidermis
What type of connective tissue is found deep to the epithelium?
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What is the function of the arrector pili muscle?
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What is the layer of tissue deep to the integument called?
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What type of tissue detects and monitors sensory stimuli in the integument?
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What is the area of the skin in square meters?
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What is the term for the epithelium of the integument?
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What is the range of thickness of the entire integument?
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What is the name of the layer of the epidermis that contains dead cells?
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What type of cells are most abundant in the epidermis?
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What is the function of melanin in the epidermis?
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What is the name of the cells sensitive to touch in the stratum basale?
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What is the term for the single layer of cuboidal to low columnar cells in the deepest epidermal layer?
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What is the name of the organelles that transfer melanin pigment to keratinocytes?
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What type of protein do keratinocytes synthesize?
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What is the term for the process of melanocytes producing melanin to block UV light?
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What type of cell does a new cell in the stratum spinosum differentiate into?
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What is the function of desmosomes in the stratum spinosum?
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Why do keratinocytes in the stratum spinosum resemble miniature porcupines?
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What is the role of epidermal dendritic (Langerhans) cells in the epidermis?
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What process begins in the stratum granulosum?
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What is the function of the stratum lucidum?
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What is the composition of the stratum corneum?
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What is the result of keratinization in the stratum corneum?
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How long does the migration of a keratinocyte to the stratum corneum take?
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What is the result of the death of keratinocytes in the stratum corneum?
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What is the function of hemoglobin in red blood cells, and how does it affect the color of blood vessels?
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What are the two types of melanin, and what colors do they produce in the skin?
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How does melanocyte activity affect the color of the entire epidermis?
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What is carotene, and where is it typically found in the skin?
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What is the difference in melanocyte activity between darker-skinned and lighter-skinned individuals?
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How does exposure to UV light affect skin color, and what is the role of melanocytes in this process?
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What are the three forms of ultraviolet radiation, and how do they affect the skin?
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What is the role of vitamin A in the body, and how is it related to carotene?
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How do UVA and UVB rays differ in their effects on the skin, and what is the myth about UVA rays?
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What is the relationship between melanin and skin color, and how is it influenced by heredity and environmental factors?
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What is the purpose of applying sunscreen liberally over all exposed body surfaces, and reapplying after being in the water or perspiring?
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How do sunless tanners produce a tanned, bronzed skin without UV light exposure?
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What is the result of the nonfunctional enzyme needed to produce melanin in individuals with albinism?
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What is the significance of monitoring nevi for changes?
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What is the difference between capillary hemangiomas and cavernous hemangiomas?
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What is the purpose of friction ridges on the palms, fingers, soles, and toes?
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What is the term for the study of friction ridge patterns?
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Why is it important to apply sunscreen when using sunless tanners?
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What determines the degree of pigmentation in freckles?
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What is the significance of the SPF number on sunscreens?
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What purpose does the stratum corneum serve in the integument, and how long do the dead, keratinized cells remain in this layer?
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What is the main difference between thick skin and thin skin, and where is each type typically found?
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What are some exocrine gland secretions that help prevent the growth of microorganisms on the epidermis?
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Why do you think thick skin lacks hair follicles and sebaceous glands?
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What determines the normal skin color, and what are the contributors to this color?
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How can you identify the epidermal strata using light microscopy, and what features should you look for?
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What are the thickness ranges of the epidermis in thick skin and thin skin?
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What are the structures found in thin skin, and how do they differ from those found in thick skin?
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What is the lifespan of individual keratinocytes in the integument, and how long do they remain in the stratum corneum?
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What is the significance of the stratum lucidum in thick skin, and how does it differ from thin skin?
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What is the significance of the interlocking projections in the model of the epidermis and dermis?
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What is the clinical significance of lines of cleavage in the skin?
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How do collagen and elastic fibers contribute to the physical characteristics of the skin?
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What is the significance of friction ridge patterns in dermatoglyphics, and how do they form?
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What causes stretch marks, and how do they affect the skin?
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What layers of the epidermis would be penetrated by a thorn, starting from the surface of the skin?
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How do tattoos become permanent, and why is it difficult to remove them?
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Compare and contrast the papillary and reticular layers of the dermis.
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Briefly describe the process of keratinization. Where does it occur, and why is it important?
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How does hemoglobin contribute to skin color?
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What is the function of the subcutaneous layer, and what type of tissue does it consist of?
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How does the skin produce vitamin D?
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What are the two major regions of the dermis, and what are their characteristics?
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What is the role of dermal papillae in the skin?
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What is the function of dermal papillae, and how do they interact with epidermal ridges?
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How do surgical procedures take into account lines of cleavage in the skin?
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What type of connective tissue is found in the papillary layer, and what type is found in the reticular layer?
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What is the significance of cleavage lines in the dermis?
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What is the role of dendritic cells in the dermis, and how do they compare to epidermal dendritic cells?
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What structures are found within the dermis, and what is their significance?
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What is the primary function of the seven major types of sensory receptors housed within the skin?
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How does exposure to ultraviolet light affect the dermis?
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What is the significance of the dermis in relation to the skin's functions?
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What are some ways the skin can dissipate excess heat?
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How does the anatomy of the integument support its various functions?
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What is the importance of the skin's immune function?
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What is the significance of the connective tissue fibers in the reticular layer of the dermis and subcutaneous layer?
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Why are drugs often injected into the subcutaneous layer?
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How do sex hormones influence the distribution of subcutaneous fat?
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What is the primary function of the papillary layer of the dermis?
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What are the two main functions of the integument in terms of temperature regulation?
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How does the integumentary system interact with the immune system?
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What is the role of the integument in maintaining blood volume?
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How does the integumentary system aid in the synthesis of vitamin D?
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What is the significance of hairs in the nasal cavity?
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What is the role of the integument in the excretion of nitrogenous waste products?
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What is the main function of the skin in terms of protection from the external environment?
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How does the skin prevent water loss and water gain?
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What is the role of keratinocytes in vitamin D synthesis?
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Why did children during the Industrial Revolution develop rickets?
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What is the skin's role in electrolyte homeostasis?
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What is the significance of melanin in the epidermis?
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How does the skin's secretory function contribute to thermoregulation?
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What is the role of corticosteroids in the skin?
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How does the skin's water-resistant properties affect its role in preventing water gain?
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What is the relationship between vitamin D synthesis and UV light exposure in the skin?
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What is the function of sebaceous glands in the skin?
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How do transdermal patches work to administer drugs?
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What is the effect of vasoconstriction on dermal blood vessels?
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What is the function of epidermal dendritic cells in the immune response?
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What is the effect of vasodilation on dermal blood vessels?
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Why is the skin selectively permeable?
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What is the role of sweat glands in temperature regulation?
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How do dermal blood vessels contribute to body temperature regulation?
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What is the significance of the autonomic motor neurons in controlling skin functions?
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How do transdermal patches release drugs into the bloodstream?
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Study Notes
Integumentary System
- The integument is the body's largest organ, composed of all tissue types that function together to protect internal body structures.
- It consists of two distinct layers: epidermis (stratified squamous epithelium) and dermis (both areolar and dense irregular connective tissue).
Epidermis
- Thickness ranges from 0.075 mm to 0.6 mm
- Composed of five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
- Keratinocytes are the most abundant cell type in the epidermis and are found throughout all epidermal strata
- Keratinocytes synthesize keratin, a protein that strengthens the epidermis considerably
- Melanocytes produce and store melanin, which accumulates around the nucleus of keratinocytes and shields nuclear DNA from ultraviolet (UV) radiation
- Tactile cells (Merkel cells) are sensitive to touch and release chemicals that stimulate sensory nerve endings
Stratum Basale
- Deepest epidermal layer, also known as the stratum germinativum or basal layer
- Consists of cuboidal to low columnar cells tightly attached to an underlying basement membrane
- Contains keratinocyte stem cells, melanocytes, and tactile cells
Stratum Spinosum
- Several layers of polygonal keratinocytes
- Keratinocytes attach to their neighbors by desmosomes, providing structural support between cells
- Also contains Langerhans cells, which are immune cells that help fight infection in the epidermis
Stratum Granulosum
- Consists of three to five layers of keratinocytes superficial to the stratum spinosum
- Keratinocytes begin to synthesize significant amounts of keratin, resulting in the disintegration of their nucleus and organelles
- Contains granules that help aggregate keratin filaments in the stratum corneum
Stratum Lucidum
- Thin, translucent region of about two to three keratinocyte layers
- Found only in thick skin within the palms of the hands and the soles of the feet
- Keratinocytes are flattened, pale cells filled with eleidin, an intermediate product in keratin formation
Stratum Corneum
- Most superficial layer of the epidermis
- Consists of about 20 to 30 layers of dead, scaly, interlocking keratinized cells
- Dead keratinocytes are anucleate and tightly packed together
- Keratinized cells contain large amounts of keratin enclosed in a thickened plasma membrane
Variations in the Epidermis
- Thickness varies between different body regions within one individual
- Classified as either thick or thin based on the number of layers and thickness of the stratified squamous epithelium
- Thick skin lacks hair follicles and sebaceous glands, whereas thin skin contains hair follicles, sebaceous glands, and sweat glands
Skin Color
- Results from a combination of hemoglobin, melanin, and carotene
- Melanin is produced and stored in melanocytes and transferred to keratinocytes
- Carotene is a yellow-orange pigment acquired from yellow-orange vegetables
- Vitamin A is converted from carotene in the liver and plays an important role in vision and reducing free radicals### Malignant Melanomas and Skin Markings
- Malignant melanomas develop due to excessive UV light exposure, and nevi should be monitored for changes that may suggest malignancy.
- Freckles are yellowish or brown spots that represent localized areas of increased melanocyte activity, not an increase in melanocyte numbers.
- Hemangiomas are anomalies that result in skin discoloration due to blood vessels that proliferate to form a benign tumor.
- Capillary hemangiomas, also known as strawberry-colored birthmarks, appear as bright red to deep purple nodules.
- Cavernous hemangiomas, also known as port-wine stains, involve larger dermal blood vessels and may last a lifetime.
- Friction ridges are markings on the skin that follow the contours of the skin, found on palms, fingers, soles, and toes.
- They help increase friction on contact, allowing hands to firmly grasp items and feet to prevent slipping when walking barefoot.
- Friction ridges are a unique identifier, with no two individuals sharing the same set of fingerprints.
Dermis
- The dermis is the layer of the integument deep to the epidermis, ranging in thickness from 0.5 mm to 3.0 mm.
- It is composed of connective tissue proper, primarily containing collagen fibers, as well as elastic and reticular fibers.
- The dermis contains:
- Dendritic cells, which serve an immune function.
- Blood vessels.
- Sweat glands.
- Sebaceous glands.
- Hair follicles.
- Nail roots.
- Sensory nerve endings.
- Smooth muscle tissue associated with hair follicles.
- The dermis has two major regions:
- Papillary layer: a superficial layer of areolar connective tissue with dermal papillae that interdigitate with epidermal ridges.
- Reticular layer: a deeper layer of dense irregular connective tissue with collagen fibers extending in all directions.
Cleavage Lines and Stretch Marks
- Lines of cleavage are areas where collagen fibers are aligned in parallel bundles due to applied stress during routine movement.
- These lines are medically important because incisions made parallel to cleavage lines usually remain closed, whereas those made perpendicular to cleavage lines may result in slow healing and increased scarring.
- Stretch marks, or striae, occur when the skin is stretched beyond its capacity, causing collagen fibers to tear.
Subcutaneous Layer
- The subcutaneous layer, also known as the hypodermis or superficial fascia, is the layer deep to the integument.
- It consists of both areolar connective tissue and adipose connective tissue.
- The subcutaneous layer pads and protects the body, acts as an energy reservoir, and provides thermal insulation.
- It is also where drugs are often injected using hypodermic needles, as its extensive vascular network promotes rapid absorption.
Functions of the Integument
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Protection from the external environment.
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Prevention of water loss and gain.
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Vitamin D synthesis: keratinocytes in the epidermis convert a steroid molecule to vitamin D3, which is then released into the blood.
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Secretion: sweat glands excrete sweat, which helps regulate body temperature, and sebaceous glands excrete sebum, which lubricates the epidermis and hair.
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Absorption: the skin can absorb certain chemicals and drugs, making it selectively permeable.
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Temperature regulation: the dermis helps regulate body temperature through its vast capillary networks and sweat glands.### Thermoregulation and Skin Color
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Vasodilation of dermal blood vessels increases blood flow to the skin surface, resulting in a more reddish/pinkish hue.
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This process helps to release excess heat from the body.
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Conversely, vasoconstriction leads to reduced blood flow, making the skin appear paler.
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Flushing of the face occurs when exercising or moving from a cold to a warm environment due to increased blood flow.
Immune Function
- Epidermal dendritic cells in the stratum spinosum play a crucial role in initiating an immune response against pathogens that penetrate the skin.
- These cells, along with dermal dendritic cells, also attack epidermal cancer cells.
Sensory Reception
- The skin contains a vast number of sensory nerve endings that detect and interpret various stimuli, including touch and pressure.
- Seven major types of sensory receptors are present in the skin to distinguish and respond to different stimuli.
Integument Functions
- The skin's composition, including the epidermis and dermis, enables it to perform several functions, such as:
- Protecting the body from the external environment
- Preventing water loss and gain
- Synthesizing vitamin D
- Secreting and absorbing substances
- Regulating temperature
- Facilitating immune function
- Enabling sensory reception
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Description
Learn about the composition and functions of the integument, the body's largest organ, including its epithelium, connective tissue, and smooth muscle associated with hair follicles.