p.4
Histologic Characteristics of Skin Layers
What are keratins?
Major structural proteins of the epidermis.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What are the three stages of hair growth?
Anagen, Catagen, and Telogen.
p.1
Histologic Characteristics of Skin Layers
What type of epithelium makes up the epidermis?
Keratinized stratified squamous epithelium.
p.6
Clinical Correlations: Skin Disorders and Cancers
How long does it take for epidermal turnover in psoriasis?
Approximately 8 to 10 days.
p.2
Histologic Characteristics of Skin Layers
What is the Stratum Spinosum also known as?
Spinous layer or prickle cell layer.
p.1
Overview of the Integumentary System
What is the largest organ of the body?
The skin, covering approximately 1.7 m².
p.4
Histologic Characteristics of Skin Layers
What is the primary function of keratinocytes?
Separation of the organism from the external environment.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What is the primary function of the hair cuticle?
To protect the hair from damage and determine its porosity.
p.1
Overview of the Integumentary System
What is the primary function of the skin?
To act as a barrier against physical, chemical, and biological agents.
p.1
Nerve Supply and Sensory Receptors in Skin
What is the function of Merkel cells in the skin?
They provide sensory information.
p.4
Histologic Characteristics of Skin Layers
What is the difference between soft keratin and hard keratin?
Soft keratin is formed in the epidermis, while hard keratin is found in hair and nails.
p.13
Epidermal Appendages: Hair, Glands, and Nails
What type of epithelium lines the duct segment of sweat glands?
Stratified cuboidal epithelium.
p.13
Epidermal Appendages: Hair, Glands, and Nails
Where are apocrine sweat glands primarily located?
In the axilla, areola, nipple of mammary gland, skin around anus, and external genitalia.
p.6
Skin Color and Factors Influencing Pigmentation
What regulates the differentiation of melanocyte stem cells?
The expression of the Pax3 gene.
p.5
Mechanisms of Skin Repair and Regeneration
What role do KLKs play in the stratum corneum?
KLKs degrade desmosomes and cause keratinocyte release as pH decreases.
p.4
Histologic Characteristics of Skin Layers
What are the four different types of cells in the epidermis?
Keratinocytes, Melanocytes, Langerhans’ cells, and Merkel’s cells.
p.2
Histologic Characteristics of Skin Layers
What are the characteristics of the Stratum Basale?
Single layer of small cuboidal to low columnar cells, basophilic cytoplasm, closely spaced nuclei, and contains mitotically active stem cells.
p.1
Adipose Tissue: White and Brown Types
What is the hypodermis primarily composed of?
Variable amounts of adipose tissue.
p.6
Skin Color and Factors Influencing Pigmentation
What is the process of melanin production starting from tyrosine?
Tyrosine -> DOPA -> melanin.
p.13
Epidermal Appendages: Hair, Glands, and Nails
What is the lunula of the nail?
The crescent-shaped white area near the root of the nail, derived from partially keratinized matrix cells.
p.13
Epidermal Appendages: Hair, Glands, and Nails
What are the three types of cells found in the secretory segment of sweat glands?
Clear cells, dark cells, and myoepithelial cells.
p.13
Epidermal Appendages: Hair, Glands, and Nails
What is the primary function of clear cells in sweat glands?
To produce the watery component of sweat.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What are vellus hairs?
Short, fine hairs that may be visible only with a magnifying glass.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What is the role of the hair matrix?
It consists of dividing matrix cells that migrate from the follicular bulge and are responsible for hair growth.
How does the thickness of the epidermis vary?
It varies from 1 mm to 5 mm.
p.4
Histologic Characteristics of Skin Layers
What regulates the desquamation of surface keratinocytes?
Proteolytic degradation of the cells’ desmosomes.
p.5
Clinical Correlations: Skin Disorders and Cancers
What are the main characteristics of Netherton Syndrome?
Decreased skin barrier function, erythroderma, and scaling.
p.8
Clinical Correlations: Skin Disorders and Cancers
What is Langerhans' cell histiocytosis?
A group of immune diseases characterized by an abnormal increase and spread of Langerhans' cells.
p.2
Histologic Characteristics of Skin Layers
What type of epithelium composes the epidermis?
Stratified squamous epithelium.
p.2
Histologic Characteristics of Skin Layers
What is the deepest layer of the epidermis called?
Stratum Basale (also known as Stratum germinativum).
p.13
Epidermal Appendages: Hair, Glands, and Nails
What type of secretion do apocrine sweat glands produce?
A secretion containing protein, carbohydrate, ammonia, lipid, and certain organic compounds.
p.6
Skin Color and Factors Influencing Pigmentation
What is the primary function of melanin?
To protect against the damaging effects of ultraviolet irradiation.
p.2
Histologic Characteristics of Skin Layers
What is the Stratum Corneum known for?
It is the horny layer, varies in thickness, and is the thickest in thick skin.
p.3
Histologic Characteristics of Skin Layers
What is the appearance of keratinized cells under light microscopy?
They often have a refractile appearance and may stain poorly.
p.7
Skin Color and Factors Influencing Pigmentation
How are developing melanosomes transferred to neighboring keratinocytes?
Through pigment donation involving phagocytosis.
p.10
Skin Color and Factors Influencing Pigmentation
What are the two distinct forms of melanin pigment?
Eumelanin (brownish-black) and pheomelanin (reddish-yellow).
p.10
Clinical Correlations: Skin Disorders and Cancers
What is Addison’s Disease and its effect on skin pigmentation?
An adrenal hormone imbalance that causes increased pigmentation of the skin.
p.8
Clinical Correlations: Skin Disorders and Cancers
What type of skin cancer is associated with uncontrolled proliferation of Merkel's cells?
Merkel cell carcinoma (MCC).
p.6
Clinical Correlations: Skin Disorders and Cancers
What condition leads to increased permeability to water in the epidermis?
Essential fatty acid deficiency.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What is the route for the discharge of sebum in hair follicles?
Isthmus, extending from the infundibulum to the level of insertion of the arrector pili muscle.
p.4
Histologic Characteristics of Skin Layers
What is the role of keratohyalin granules?
They aid in the aggregation of keratin filaments.
p.2
Histologic Characteristics of Skin Layers
What happens to the cells in the Stratum Corneum?
They lose cytoplasmic organelles and are filled with keratin filaments, becoming anucleate.
p.10
Skin Color and Factors Influencing Pigmentation
What is the primary factor that differs among races regarding melanin?
The fate of melanin, not the number of melanocytes.
p.3
Components and Functions of the Dermis
What enhances the attachment between the epidermis and dermis?
The epidermal-dermal junction, which is an uneven boundary.
p.9
Nerve Supply and Sensory Receptors in Skin
What do Meissner’s corpuscles serve as?
Touch receptors, particularly responsive to low-frequency stimuli.
p.9
Nerve Supply and Sensory Receptors in Skin
What is the structural characteristic of Ruffini's corpuscles?
They have an elongated fusiform shape and a thin connective tissue capsule.
p.13
Epidermal Appendages: Hair, Glands, and Nails
What is the main difference between eccrine and apocrine sweat glands in terms of stimulation?
Eccrine glands are stimulated by cholinergic transmitters, while apocrine glands are stimulated by adrenergic transmitters.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What are the three layers of the internal root sheath?
Henle’s Layer, Huxley’s Layer, and Internal Root Sheath Cuticle.
p.11
Epidermal Appendages: Hair, Glands, and Nails
Where does keratinization occur in the hair follicle?
In the keratogenous zone, which is the lower third of the follicle.
p.8
Nerve Supply and Sensory Receptors in Skin
What is the function of Merkel's cells?
They function in cutaneous sensation.
p.10
Clinical Correlations: Skin Disorders and Cancers
What is albinism?
A hereditary condition involving lack of pigmentation in hair and skin due to absence of tyrosinase.
p.8
Nerve Supply and Sensory Receptors in Skin
What are free nerve endings responsible for?
They serve multiple sensory modalities including fine touch, heat, cold, and pain.
p.2
Overview of the Integumentary System
What is the primary difference between thick skin and thin skin?
Thick skin has a thicker epidermal layer and is hairless, found on the palms of hands and soles of feet.
p.1
Components and Functions of the Dermis
What role do Langerhans cells play in the skin?
They provide immunologic information during antigen processing.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What is the role of sebaceous glands?
To produce sebum, which coats the hair and skin surface.
p.2
Histologic Characteristics of Skin Layers
What is the primary function of the Stratum Granulosum?
Keratinocytes in this layer contain keratohyaline granules, which are precursors for filaggrin that aggregates keratin filaments.
p.7
Skin Color and Factors Influencing Pigmentation
What happens to the internal structure of premelanosomes as melanin is produced?
It becomes obscured until mature melanin granules (melanosomes) are formed.
p.2
Histologic Characteristics of Skin Layers
What is the Stratum Lucidum?
A subdivision of the Stratum Corneum, only well seen in thick skin.
p.5
Components and Functions of the Dermis
What is the function of lamellar bodies in the epidermis?
They contribute to the formation of the intercellular epidermal water barrier.
p.10
Skin Color and Factors Influencing Pigmentation
What triggers tanning in the skin?
Exposure to ultraviolet radiation, which increases melanocyte numbers and accelerates melanin production.
p.8
Nerve Supply and Sensory Receptors in Skin
What is a Merkel's corpuscle?
A sensitive mechanoreceptor formed by the combination of a neuron and a Merkel's cell.
p.10
Skin Color and Factors Influencing Pigmentation
How does aging affect melanocyte levels and skin color?
Melanocyte depletion occurs with age, leading to lighter skin and increased skin cancer incidence.
p.8
Nerve Supply and Sensory Receptors in Skin
What is the role of Meissner's corpuscles?
They are responsible for sensitivity to light touch.
p.6
Components and Functions of the Dermis
What is the most important component of the epidermal barrier?
The monomolecular layer of acylglucosylceramide.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What are terminal hairs?
Long and coarse hairs produced by large-diameter follicles.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What is the follicular bulge?
A protrusion from the hair follicle near the insertion of the arrector pili muscle that contains a niche of epidermal stem cells.
p.1
Epidermal Appendages: Hair, Glands, and Nails
What are the epidermal appendages?
Hair follicles, sweat glands, sebaceous glands, nails, and mammary glands.
p.7
Skin Color and Factors Influencing Pigmentation
Where are premelanosomes concentrated?
Near the Golgi apparatus.
p.10
Skin Color and Factors Influencing Pigmentation
How does melanin distribution differ in light skin compared to dark skin?
In light skin, melanosomes are concentrated near the basal layer; in dark skin, they are found throughout the epidermis.
p.3
Components and Functions of the Dermis
What are dermal papillae?
Projections from the dermis into the epidermis.
p.3
Components and Functions of the Dermis
What is the significance of dermal ridges and papillae?
They create a distinctive pattern unique to each individual, forming the basis of dermatoglyphics.
p.3
Components and Functions of the Dermis
What is the predominant collagen type in the papillary layer?
Type I and Type III collagen.
p.10
Epidermal Appendages: Hair, Glands, and Nails
What are the four regions of the hair follicle's growing phase?
Infundibulum, isthmus, follicular bulge, and inferior segment.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What occurs during the Anagen phase of hair growth?
It is the period of hair growth where new hair develops.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What happens during the Telogen phase?
The follicle atrophies, and the hair is eventually lost.
p.2
Histologic Characteristics of Skin Layers
What distinct feature is observed in the Stratum Spinosum during preparation?
Cells shrink, creating expanded intercellular spaces between the spines.
p.13
Epidermal Appendages: Hair, Glands, and Nails
What is the function of the nail matrix?
Contains stem cells that regularly divide and produce keratin for the nail.
p.1
Overview of the Integumentary System
What is the role of the skin in thermoregulation?
It regulates body temperature and water loss.
p.8
Clinical Correlations: Skin Disorders and Cancers
What role do Langerhans' cells play in the immune system?
They are Antigen Presenting Cells (APCs) involved in delayed-type hypersensitivity reactions.
p.9
Nerve Supply and Sensory Receptors in Skin
What is the structure of Pacinian corpuscles?
Composed of a myelinated nerve ending surrounded by a capsule structure.
p.7
Skin Color and Factors Influencing Pigmentation
What are some factors influencing skin pigmentation?
Age, ethnicity, gender differences, hormone levels, genetic defects, UV radiation, climate, and chemical exposure.
p.10
Epidermal Appendages: Hair, Glands, and Nails
What is the function of the arrector pili muscle?
It is attached near the follicular bulge and causes hair to stand up.
p.12
Epidermal Appendages: Hair, Glands, and Nails
What is the function of eccrine sweat glands?
To regulate temperature through the evaporation of sweat.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What are the three layers of hair?
Medulla, Cortex, and Cuticle.
p.9
Nerve Supply and Sensory Receptors in Skin
Where are Pacinian corpuscles primarily located?
In the deeper dermis and hypodermis, especially in the fingertips.
p.7
Skin Color and Factors Influencing Pigmentation
How does melanin degradation differ in darker vs. lighter skin individuals?
In darker skin, melanin is degraded slowly; in lighter skin, it is degraded more rapidly.
p.7
Nerve Supply and Sensory Receptors in Skin
What type of cells are Langerhans' cells?
Antigen-presenting cells in the epidermis.
p.5
Components and Functions of the Dermis
What are the major lipid components of the lipid envelope?
Ceramides, cholesterol, and free fatty acids.
p.7
Nerve Supply and Sensory Receptors in Skin
What distinctive feature do Langerhans' cells have under TEM?
Their nucleus is characteristically indented and uneven.
p.6
Skin Color and Factors Influencing Pigmentation
How is melanin synthesis regulated?
By melanocyte-stimulating hormone (MSH) binding to the melanocortin 1 receptor (MC1R).
p.5
Clinical Correlations: Skin Disorders and Cancers
What is Netherton Syndrome associated with?
The gene encoding LEKTI, specifically SPINK5.
p.3
Histologic Characteristics of Skin Layers
What happens to the nucleus and cytoplasmic organelles during keratinization?
They become disrupted and disappear as the cell fills with keratin.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What is the composition of the medulla in hair?
It contains a column of large, loosely connected keratinized cells with soft keratin, present only in thick hairs.
p.5
Components and Functions of the Dermis
What is the major structural protein of the cell envelope in the epidermis?
Loricrin, accounting for almost 80% of the total cell envelope protein mass.
p.9
Nerve Supply and Sensory Receptors in Skin
What do Ruffini's corpuscles respond to?
Displacement of adjacent collagen fibers induced by sustained mechanical stress.
p.3
Components and Functions of the Dermis
What are Langer's lines?
Regular lines of tension in the skin that affect healing and scarring.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What is keratinization in hair?
The process where hair cells differentiate, extrude organelles, and become tightly packed with keratin intermediate filaments shortly after leaving the matrix.
p.11
Epidermal Appendages: Hair, Glands, and Nails
What determines the elasticity, texture, and color of hair?
The cortex, which is the largest layer of hair and contains melanocytes responsible for melanin pigment.
p.5
Components and Functions of the Dermis
What two factors primarily establish the epidermal water barrier?
Deposition of insoluble proteins and a lipid layer on the plasma membrane.
p.8
Nerve Supply and Sensory Receptors in Skin
Where are Merkel's cells most abundant?
In areas of skin where sensory perception is acute, such as the fingertips.
p.10
Skin Color and Factors Influencing Pigmentation
What role do the Bcl2 and Mitf genes play in hair graying?
They are responsible for the maintenance of melanocyte stem cells, and their deficiency can lead to hair graying.
p.8
Nerve Supply and Sensory Receptors in Skin
What do Pacinian corpuscles detect?
Pressure changes and vibrations applied on the skin surface.
p.9
Nerve Supply and Sensory Receptors in Skin
What type of receptors are Pacinian corpuscles?
Deep pressure receptors for mechanical and vibratory pressure.
p.9
Nerve Supply and Sensory Receptors in Skin
How do Pacinian corpuscles respond to pressure and vibration?
Through the displacement of the capsule lamellae, causing depolarization of the axon.
p.9
Nerve Supply and Sensory Receptors in Skin
Where are Meissner’s corpuscles located?
In the dermal papillae just beneath the epidermal basal lamina.
p.5
Components and Functions of the Dermis
What do keratinocytes produce in the stratum spinosum?
Keratohyalin granules and membrane-bound lamellar bodies.
p.7
Nerve Supply and Sensory Receptors in Skin
Where do Langerhans' cells originate?
From common lymphoid progenitor (CLP) cells in bone marrow.
p.5
Components and Functions of the Dermis
What is the role of ceramides in the lipid envelope?
They play an important role in cell signaling and inducing cell differentiation.
p.3
Adipose Tissue: White and Brown Types
What is the panniculus adiposus?
A layer of adipose tissue beneath the reticular layer that serves as a major energy storage site.
p.3
Components and Functions of the Dermis
What characterizes the reticular layer of the dermis?
Thick, irregular bundles of mostly Type I collagen and coarser elastic fibers.
p.3
Components and Functions of the Dermis
What is the function of arrector pili muscles?
They connect hair follicles to the dermis and cause hair erection and skin puckering.
p.10
Epidermal Appendages: Hair, Glands, and Nails
What is the role of the hair follicle?
It represents an invagination of the epidermis responsible for the production and growth of hair.
