Podcast
Questions and Answers
What is the primary function of Pacinian corpuscles?
What is the primary function of Pacinian corpuscles?
Which phase of hair growth is characterized by a period of arrested growth?
Which phase of hair growth is characterized by a period of arrested growth?
What is the primary function of Langerhans cells in the epidermis?
What is the primary function of Langerhans cells in the epidermis?
What is the composition of Ruffini corpuscles that allows them to respond to skin tensions?
What is the composition of Ruffini corpuscles that allows them to respond to skin tensions?
Signup and view all the answers
Where are Merkel cells predominantly located within the layers of the skin?
Where are Merkel cells predominantly located within the layers of the skin?
Signup and view all the answers
Where are Krause end bulbs primarily located?
Where are Krause end bulbs primarily located?
Signup and view all the answers
What part of the hair structure contains the vasculature that supplies nutrients and oxygen?
What part of the hair structure contains the vasculature that supplies nutrients and oxygen?
Signup and view all the answers
Which component of the dermis binds it to the epidermis?
Which component of the dermis binds it to the epidermis?
Signup and view all the answers
What type of tissue primarily composes the reticular dermis?
What type of tissue primarily composes the reticular dermis?
Signup and view all the answers
What percentage of cells in the epidermis do Langerhans cells account for?
What percentage of cells in the epidermis do Langerhans cells account for?
Signup and view all the answers
What is the primary function of melanin in the skin?
What is the primary function of melanin in the skin?
Signup and view all the answers
Which type of cells in the epidermis are responsible for the production of pigment?
Which type of cells in the epidermis are responsible for the production of pigment?
Signup and view all the answers
What role do dermal papillae play in the skin?
What role do dermal papillae play in the skin?
Signup and view all the answers
Which layer of the skin is primarily responsible for heat loss mechanisms?
Which layer of the skin is primarily responsible for heat loss mechanisms?
Signup and view all the answers
Which function of the skin involves the synthesis of Vitamin D3?
Which function of the skin involves the synthesis of Vitamin D3?
Signup and view all the answers
What type of epithelium primarily composes the epidermis?
What type of epithelium primarily composes the epidermis?
Signup and view all the answers
What kind of receptors in the skin help monitor the surrounding environment?
What kind of receptors in the skin help monitor the surrounding environment?
Signup and view all the answers
What is the primary characteristic of dermal-epidermal interdigitations?
What is the primary characteristic of dermal-epidermal interdigitations?
Signup and view all the answers
What is the primary role of dermatan sulfate in the skin?
What is the primary role of dermatan sulfate in the skin?
Signup and view all the answers
Where is the subpapillary plexus located?
Where is the subpapillary plexus located?
Signup and view all the answers
What is the function of arteriovenous anastomoses in the skin?
What is the function of arteriovenous anastomoses in the skin?
Signup and view all the answers
Which type of nerve fibers is responsible for sensory input in the skin?
Which type of nerve fibers is responsible for sensory input in the skin?
Signup and view all the answers
How does the subcutaneous layer impact drug uptake?
How does the subcutaneous layer impact drug uptake?
Signup and view all the answers
What type of stimuli do free nerve endings in the skin detect?
What type of stimuli do free nerve endings in the skin detect?
Signup and view all the answers
What is a characteristic feature of Meissner corpuscles?
What is a characteristic feature of Meissner corpuscles?
Signup and view all the answers
Which structure is primarily responsible for detecting hair movement?
Which structure is primarily responsible for detecting hair movement?
Signup and view all the answers
What primarily stimulates the increase of sebum production during puberty?
What primarily stimulates the increase of sebum production during puberty?
Signup and view all the answers
Which type of sweat gland is primarily responsible for thermoregulation?
Which type of sweat gland is primarily responsible for thermoregulation?
Signup and view all the answers
Which cell type in the eccrine sweat gland is responsible for contracting to move secretion into the duct?
Which cell type in the eccrine sweat gland is responsible for contracting to move secretion into the duct?
Signup and view all the answers
What characterizes the secretory portion of apocrine sweat glands?
What characterizes the secretory portion of apocrine sweat glands?
Signup and view all the answers
How do eccrine sweat gland ducts contribute to electrolyte balance?
How do eccrine sweat gland ducts contribute to electrolyte balance?
Signup and view all the answers
Where are apocrine sweat glands mainly located in the body?
Where are apocrine sweat glands mainly located in the body?
Signup and view all the answers
What distinguishes the secretion of apocrine sweat glands from that of eccrine sweat glands?
What distinguishes the secretion of apocrine sweat glands from that of eccrine sweat glands?
Signup and view all the answers
Which gland is NOT involved in the secretion of sebum?
Which gland is NOT involved in the secretion of sebum?
Signup and view all the answers
What type of pigment is produced by melanocytes that results in red hair?
What type of pigment is produced by melanocytes that results in red hair?
Signup and view all the answers
What is the primary defect in albinism?
What is the primary defect in albinism?
Signup and view all the answers
Which cells are involved in the epidermal-melanin unit?
Which cells are involved in the epidermal-melanin unit?
Signup and view all the answers
Where are melanocytes primarily located within the skin?
Where are melanocytes primarily located within the skin?
Signup and view all the answers
What role do keratinocytes play in relation to melanocytes?
What role do keratinocytes play in relation to melanocytes?
Signup and view all the answers
What is the primary function of melanin in melanocytes?
What is the primary function of melanin in melanocytes?
Signup and view all the answers
In terms of the ratio, how do melanocytes migrate to the embryonic epidermis?
In terms of the ratio, how do melanocytes migrate to the embryonic epidermis?
Signup and view all the answers
What is vitiligo characterized by?
What is vitiligo characterized by?
Signup and view all the answers
What are melanosomes responsible for in the epidermis?
What are melanosomes responsible for in the epidermis?
Signup and view all the answers
What initiates the synthesis of melanin granules in melanocytes?
What initiates the synthesis of melanin granules in melanocytes?
Signup and view all the answers
Study Notes
Skin Structure and Function
- The skin is the largest organ of the body, accounting for 15-20% of total body weight.
- It consists of three layers: epidermis, dermis, and hypodermis.
- Dermal papillae are projections located at the junction between the dermis and epidermis. They interdigitate with epidermal ridges to strengthen adhesion between dermis and epidermis
Skin Properties
- Dermatoglyphs (fingerprints) are dermal-epidermal interdigitations forming a unique pattern for each individual.
- Skin is elastic and expands rapidly to accommodate swollen areas.
- Skin continually self-renews throughout life.
Skin Functions
-
Protection: Acting as a physical barrier against thermal and mechanical damage (e.g., friction). Protects against potential pathogens and foreign materials through macrophages and antigen-presenting cells. Skin protects against UV rays with melanin, and forms a permeability barrier preventing excessive water loss or uptake. Allows for administration of lipophilic drugs, steroids, hormones, and medications.
-
Sensory: Constantly monitors the surroundings and mechanoreceptors regulate body's interaction with physical objects
-
Thermoregulation: Maintains constant body temperature through skin's insulating components (fatty layer and hair) and mechanisms that accelerate heat loss (sweat production & dense superficial microvasculature).
-
Metabolic: Synthesis of Vitamin D3 through the local action of UV light on vitamin D precursor. Vitamin D3 is needed for calcium metabolism and proper bone formation. Excess electrolytes are removed through sweat. Fat cells store fat.
-
Sexual Signaling: Pheromones produced by apocrine sweat glands.
Epidermis Layers
-
Basal Layer/ Stratum Basale: A single layer of basophilic cuboidal or columnar cells. Hemidesmosomes bind these cells to the basal lamina, and desmosomes bind the cells laterally and apically. High mitotic activity and contains progenitor cells for the epidermal layers. Keratinocytes contain cytoskeletal keratins, with increasing amount and type as the cells move upward.
-
Spinous Layer/ Stratum Spinosum: Thickest layer of cells, especially in epidermal ridges. Consist of polyhedral cells with central nuclei and cytoplasm actively synthesizing keratins. Cells are still dividing here, in stratum germinativum. Intercellular bridges form between cells. "Spines" or prickles are increased in regions of high friction, such as the soles of your feet
-
Granular Layer/ Stratum Granulosum: Three to five layers of flattened cells undergoing keratinization. Cytoplasm filled with keratohyaline granules and filaggrin which forms structures. Lamellar granules undergo exocytosis at the terminal stage of keratinization, producing a lipid-rich, impermeable layer around the cells.
-
Stratum Lucidum: Found only in thick skin (palms, soles of feet), thin, translucent layer of flattened eosinophilic keratinocytes held together by desmosomes. Nuclei and organelles are lost. Cytoplasm consists almost exclusively of packed keratin.
-
Stratum Corneum: Consists of 15-20 layers of keratinized, squamous cells filled with keratin. Fully keratinized cells, called squames, are continuously shed.
Cells of the Epidermis
-
Melanocytes: Specialized cells in the epidermis found among the cells of the basal layer and in hair follicles. Produce eumelanin (brown/black pigments) and pheomelanin (red pigment in red hair). Melanocytes migrate to the stratum basale in a 1:6 ratio. Pale-staining round cell bodies attached to basal lamina by hemidesmosomes. Melanocytes synthesize melanin-containing granules.
-
Langerhans Cells: Antigen-presenting cells derived from monocytes. Make up 2-8% of epidermal cells and are primarily in the spinous layer. Cytoplasmic processes extend between keratinocytes to bind, process, and present antigens to T-lymphocytes.
-
Merkel Cells: Epithelial tactile cells (mechanoreceptors) specialized in gentle touch. Abundant in areas with high sensitivity. Located in the stratum basale, attached to keratinocytes by desmosomes. Have few melanocytes but abundant Golgi-derived dense-core granules and make synaptic contacts with nerves located at the basal lamina.
Dermis
-
A layer of connective tissue supporting the epidermis and binding it to hypodermis.
-
Dermal papillae extend into epidermis to form dermal-epidermal junction.
-
Dermis provides nutrients through its rich vasculature to epidermis through basement membrane.
-
Consists of two layers: papillary and reticular.
-
Papillary Dermis: Includes the dermal papillae. Composed of loose connective tissue with type I and III collagen fibers, fibroblasts, mast cells, dendritic cells, and leukocytes. Anchoring fibrils of type IV collagen attach the dermis to the epidermis.
-
Reticular Dermis: Composed of dense irregular connective tissue. Denser fibers than papillary dermis. Contains network of elastic fibers, providing elasticity, and rich in dermatan sulfate (a proteoglycan of connective tissue)
Skin Nutrition and Innervation
- Subpapillary Plexus: Network of blood vessels and nerves located between the papillary and reticular dermis.
- Larger Plexus: Location between the reticular dermis and subcutaneous tissue. Thermoregulatory function and arterivorenous anastomoses/shunts
- Sensory Afferent Nerve Fibers: Forms a network in the papillary dermis and around hair follicles (responding to stimuli)
- Autonomic Efferent Nerve Fibers: Regulate sweat glands and smooth muscles in the skin.
Hypodermis
- Sometimes called subcutaneous layer or superficial fascia, loose adipose connective tissue. Binds skin loosely to underlying muscle tissue. Contains adipocytes and thin connective tissue fibers. Extensive blood vessels supply support rapid uptake injected drugs.
Cutaneous Sensory Receptors
-
Skin functions as an extensive receiver of stimuli from the environment. Diverse encapsulated and unencapsulated receptors are present.
-
Unencapsulated Receptors: Include Merkel cells (light touch and texture), free nerve endings (temperature, pain, itch), and root hair plexuses (hair movement).
-
Encapsulated Receptors: Include Meissner's corpuscles (light touch, low-frequency stimuli), Pacinian corpuscles (pressure, vibrations), Ruffini corpuscles (stretch, tension, twisting), and Krause end bulbs (low-frequency vibrations).
Epidermal Appendages
-
Hair: Keratinized structures within epidermal invaginations (hair follicles). Grows discontinuously with phases of growth and rest.
-
Parts: Hair bulb, hair root, and hair shaft
-
Hair Papilla: Consists of dermal hair papilla penetrating the base of the hair bulb, containing a vascular supply for cells.
-
Hair Follicle: Connective tissue root sheath, glassy membrane, epithelial tissue root sheath, internal and external root sheaths.
-
Medulla, Cortex, Cuticle: Parts of hair follicle structure
-
Arrector pili muscle: A smooth muscle bundle extending from the midpoint of the hair sheath to dermal papillary layer. Contractions of arrector pili muscle causes hair to raise, providing insulation.
-
Nails: Keratinized hard plates formed on dorsal surface of distal phalanx. Nail root, cuticle, nail bed and nail matrix parts
-
Sebaceous glands: Branched acinar glands in the dermis, except palms/soles, empty into hair follicles. Contain sebocytes producing sebum and a mixture of lipids and components. Maintain stratum corneum, hair shaft, function as a weak antibacterial / antifungal agent.
-
Sweat glands: Long epidermal invaginations in the dermis. Eccrine sweat glands: widely distributed across the body, produce sweat as a physiological response to temperature change. Coiled secretory and duct structures. Secretion of watery sweat and composed of clear (basal lamina), dark (eosinophilic granules) and myoepithelial cells (move sweat to duct). Duct contains two layers of acidophilic cells and has cell membranes rich in Na-K-ATPase to absorb Na+ from secreted water.
-
Apocrine sweat glands: Confined to axillary and perineal regions, develop functionally after puberty. More viscous secretion which often gains odor due to bacterial activity. May contain pheromones.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the functions and structures in skin biology, including the roles of various cells and layers within the skin. This quiz covers key concepts that are essential for understanding human anatomy and dermatology.
