Podcast
Questions and Answers
What role does the skin play in vitamin D synthesis?
What role does the skin play in vitamin D synthesis?
- Only the kidneys have a role in this process.
- The liver and kidneys are involved after the skin. (correct)
- Vitamin D synthesis primarily occurs in the liver.
- The skin completes the vitamin D process.
Which of the following is a function of the skin's thermoreceptors?
Which of the following is a function of the skin's thermoreceptors?
- They respond only to heat.
- They monitor external pressure.
- They cause vasodilation and sweating. (correct)
- They regulate blood pressure.
Which layer of the skin contains dead cells packed with keratin?
Which layer of the skin contains dead cells packed with keratin?
- Stratum basale
- Stratum granulosum
- Stratum spinosum
- Stratum corneum (correct)
What substance do melanocytes produce, and what is its role?
What substance do melanocytes produce, and what is its role?
Which type of skin cells are the primary producers of keratin?
Which type of skin cells are the primary producers of keratin?
Which skin function involves administering drugs through skin patches?
Which skin function involves administering drugs through skin patches?
What is the primary characteristic of the epidermis?
What is the primary characteristic of the epidermis?
Which layer of the skin is the deepest and contains stem cells?
Which layer of the skin is the deepest and contains stem cells?
Which of the following is NOT a component of the integumentary system?
Which of the following is NOT a component of the integumentary system?
What is a significant reason we focus on the integumentary system more than other organ systems?
What is a significant reason we focus on the integumentary system more than other organ systems?
What is the main focus of dermatology?
What is the main focus of dermatology?
Which part of the skin is the most vulnerable due to exposure to various external factors?
Which part of the skin is the most vulnerable due to exposure to various external factors?
Which structure is responsible for detecting touch in the skin?
Which structure is responsible for detecting touch in the skin?
Which gland is commonly associated with the production of sweat?
Which gland is commonly associated with the production of sweat?
Which structure in the integumentary system is primarily responsible for providing insulation and padding?
Which structure in the integumentary system is primarily responsible for providing insulation and padding?
What type of sensory receptor is specifically sensitive to pressure in the skin?
What type of sensory receptor is specifically sensitive to pressure in the skin?
What is a primary cause of jaundice?
What is a primary cause of jaundice?
What factor primarily influences the variation in human skin color?
What factor primarily influences the variation in human skin color?
Why do populations in tropical areas tend to have darker skin?
Why do populations in tropical areas tend to have darker skin?
Which statement about women’s skin color is correct?
Which statement about women’s skin color is correct?
What are the adverse effects of UVR on skin health?
What are the adverse effects of UVR on skin health?
Which layer of the epidermis contains melanocytes and tactile cells among its stem cells?
Which layer of the epidermis contains melanocytes and tactile cells among its stem cells?
What is the main characteristic of the stratum spinosum?
What is the main characteristic of the stratum spinosum?
What is unique about the stratum lucidum?
What is unique about the stratum lucidum?
Which statement correctly describes the role of stem cells in the stratum basale?
Which statement correctly describes the role of stem cells in the stratum basale?
Which layer of the epidermis is typically the thickest in most normal skin?
Which layer of the epidermis is typically the thickest in most normal skin?
What happens to basal cells as they move toward the surface of the skin?
What happens to basal cells as they move toward the surface of the skin?
What type of fibers are found in the dermal papillae?
What type of fibers are found in the dermal papillae?
What is the primary function of keratinocytes in the epidermis?
What is the primary function of keratinocytes in the epidermis?
What characterizes the stratum granulosum layer?
What characterizes the stratum granulosum layer?
Which layer is specifically found only in thick skin?
Which layer is specifically found only in thick skin?
What is the primary function of keratinocytes in the epidermis?
What is the primary function of keratinocytes in the epidermis?
What occurs when keratinocytes migrate more than two or three cells away from the dermis?
What occurs when keratinocytes migrate more than two or three cells away from the dermis?
What happens to keratinocytes during their journey to the skin surface?
What happens to keratinocytes during their journey to the skin surface?
What is the approximate time it takes for a keratinocyte to reach the skin surface?
What is the approximate time it takes for a keratinocyte to reach the skin surface?
Which of the following occurs in the stratum granulosum?
Which of the following occurs in the stratum granulosum?
What causes the keratinocytes to flatten as they move upward in the epidermis?
What causes the keratinocytes to flatten as they move upward in the epidermis?
How do keratinocytes contribute to the waterproof properties of the skin?
How do keratinocytes contribute to the waterproof properties of the skin?
What structure is primarily formed in the stratum corneum?
What structure is primarily formed in the stratum corneum?
Which component is essential for keratinocyte mitosis in the stratum basale?
Which component is essential for keratinocyte mitosis in the stratum basale?
What happens to the nucleus and organelles of keratinocytes as they approach the skin surface?
What happens to the nucleus and organelles of keratinocytes as they approach the skin surface?
What is the role of filaggrin in the stratum granulosum?
What is the role of filaggrin in the stratum granulosum?
How do calluses form on the skin?
How do calluses form on the skin?
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Study Notes
Integumentary System
- Consists of skin, hair, nails, sweat glands, and sebaceous glands
Importance of Integumentary System
- Plays a central role in self-image and social acceptance
- Appearance of skin can indicate health issues (e.g., anemia)
- Skin is the most vulnerable organ, susceptible to radiation, trauma, infection, and chemical exposure
- Receives more medical treatment than any other organ system
- Dermatology is the scientific study and medical treatment of the integumentary system
Skin Structure
- Composed of epidermis, dermis, and hypodermis (subcutaneous fat)
- Epidermis is composed of stratified squamous epithelium (keratinized)
- Dermis is composed of dense irregular connective tissue
- Hypodermis consists of loose connective tissue and adipose tissue
Epidermis
- Composed of five layers:
- Stratum corneum
- Stratum lucidum (thick skin only)
- Stratum granulosum
- Stratum spinosum
- Stratum basale
- Lacks blood vessels, depends on diffusion of nutrients from underlying connective tissue
Cells of the Epidermis
- Five types of cells:
- Stem cells: Undifferentiated cells that give rise to keratinocytes in the deepest layer of the epidermis (stratum basale)
- Keratinocytes: Synthesize keratin, constitute the majority of epidermal cells
- Melanocytes: Found only in the stratum basale, synthesize melanin that protects DNA from UV radiation
- Tactile (Merkel) cells: Sensory receptors for touch
- Dendritic (Langerhans) cells: Immune cells that help fight infection
Layers of the Epidermis
- Thick skin has five layers, found in high-abrasion areas like hands and feet
- Thin skin only has four layers
- Stratum basale: Single layer of stem cells and keratinocytes resting on the basement membrane, contains melanocytes and tactile cells
- Stratum spinosum: Multiple layers, thicker than stratum basale in most skin, produces more keratin filaments as cells move up
- Stratum granulosum: Contains keratinocytes with keratohyalin granules, which help bind keratin filaments
- Stratum lucidum: Only in thick skin, appears translucent due to densely packed cells with eleidin
- Stratum corneum: 20-30 layers of dead, scaly, keratinized cells forming the durable surface layer, resistant to abrasion, penetration, and water loss
The Life History of a Keratinocyte
- Keratinocytes are produced in the stratum basale by stem cells and deepest cells in stratum spinosum
- Mitosis ceases once keratinocytes move more than two or three cells away from the dermis
- Newly formed keratinocytes push older ones to the surface, taking 30-40 days to reach the skin surface and flake off
- As keratinocytes move upward, they produce more keratin filaments and lipid-filled membrane-coating vesicles
Skin Color and Ultraviolet Radiation (UVR)
- Skin color varies due to multiple factors, primarily differences in UVR exposure
- Melanin shields DNA from UVR
- Populations in tropical areas have darker skin (more melanin) for UVR protection
- Populations in northern or southern latitudes have lighter skin (less melanin) to allow for adequate UVR penetration
- High altitude and dry air can also increase skin pigmentation
- Ancestral skin color is a balance between vitamin D and folic acid requirements
Skin Functions
- Vitamin D Synthesis: Skin is the first step in vitamin D synthesis; the process is completed in the liver and kidneys
- Sensation: Skin is the most extensive sense organ with various nerve endings that respond to heat, cold, touch, texture, pressure, etc.
- Thermoregulation: Thermoreceptors monitor surface temperature, vasconstriction/vasodilation
- Nonverbal Communication: Facial expressions
- Transdermal Absorption: Administration of certain drugs through the skin via adhesive patches
Dermis
- Composed of two layers:
- Papillary layer: Outer layer, contains loose connective tissue, blood vessels, and nerve endings
- Reticular layer: Deeper layer, dense irregular connective tissue, provides strength and elasticity to skin
- Contains blood vessels, nerves, glands, hair follicles, and sensory receptors
- Hair follicles are invaginations of the epidermis that extend into the dermis
Hypodermis (Subcutaneous Fat)
- Consists of loose connective tissue and adipose tissue
- Insulates and cushions the body
- Stores energy
Hair
- Composed of keratin
- Hair follicles are invaginations of the epidermis that extend into the dermis
- Piloerector muscle attached to each hair follicle, causes hair to stand erect (goosebumps)
Nails
- Composed of keratin, located at the dorsal surface of the fingers and toes
- Nail body is the visible part of the nail
- Nail root is the part embedded in the skin
- Nail matrix is responsible for nail growth
Sweat Glands
- Two types:
- Eccrine sweat glands: Produce watery sweat, help regulate body temperature
- Apocrine sweat glands: Found in axillary and genital regions, produce milky sweat that is often odorless
Sebaceous Glands
- Secrete an oily substance called sebum, which lubricates the hair and skin
Disorders/Conditions
- Jaundice: Yellowing of skin and sclera due to excess bilirubin in blood
- Hematoma (bruise): A mass of clotted blood showing through the skin
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