skin Flashcards
What is the largest organ in the body?
The skin is the largest organ in the body.
Why is the skin so important?
The skin serves several important functions, including protection against external threats, body temperature regulation, sensation, and vitamin D synthesis.
What are primary skin disorders?
Primary skin disorders refer to conditions that primarily affect the skin itself, such as acne, eczema, psoriasis, and dermatitis.
What are cutaneous manifestations of systemic illnesses?
Cutaneous manifestations of systemic illnesses are skin manifestations that occur as a result of underlying systemic conditions. For example, a malar rash or butterfly rash can be a cutaneous manifestation of lupus.
Give an example of a skin manifestation related to a systemic illness.
Generalized intractable pruritus (severe itching) can be a cutaneous manifestation of chronic renal failure.
What are some examples of skin manifestations associated with specific conditions?
Some examples include splinter hemorrhages seen in bacterial endocarditis or vasculitis, half and half nails, which can be indicative of certain systemic disorders, and dermatitis herpetiformis, which is associated with celiac disease (gluten sensitivity).
How are skin disorders diagnosed?
The diagnosis of skin disorders, like all pathology in medicine, can be approached using the surgical sieve or a structure-based approach. These methods involve a systematic examination of the skin, taking into account various factors such as appearance, distribution, and associated symptoms.
What are the three main layers of the skin?
The skin is composed of three main layers: the epidermis, dermis, and subcutis (also known as the hypodermis).
What is the epidermis?
The epidermis is the outermost layer of the skin. It is primarily made up of epithelial cells and serves as a protective barrier against external factors.
What is the dermis?
The dermis is the middle layer of the skin. It contains connective tissue, blood vessels, hair follicles, sweat glands, sebaceous glands, and nerve endings.
What structures can be found within the dermis?
Within the dermis, you can find blood vessels, which supply nutrients and oxygen to the skin, and hair shafts, responsible for hair growth. The dermis also contains arrector pili muscles responsible for causing hair to stand on end (goosebumps).
What is the subcutis or hypodermis?
The subcutis, also known as the hypodermis, is the deepest layer of the skin. It consists of fat cells, connective tissue, and larger blood vessels. It provides insulation and cushioning to the body.
What type of epithelium makes up the epidermis?
The epidermis is composed of keratinizing, stratified squamous epithelium.
How does the epidermis cover the body?
The epidermis forms a continuous layer that covers the surface of the body.
What are the natural openings in the epidermis?
The epidermis has natural openings for hair follicles and sweat ducts, which are collectively known as the acrosyringium.
What are the main cell types found within the epidermis?
Keratinocytes: These are the most abundant cells in the epidermis and produce the protein keratin, which provides strength and protection.
Melanocytes: Melanocytes produce the pigment melanin, which determines skin color and provides protection against UV radiation.
Langerhans cells: Langerhans cells are immune cells that help protect against pathogens and foreign substances.
Merkel cells: Merkel cells are involved in the sensation of touch and are located in the deepest layer of the epidermis.
What is the outermost layer of the epidermis called?
The outermost layer of the epidermis is called the horn cell layer or stratum corneum. It is composed of dead, flattened keratinocytes that are continuously shed and replaced.
Which layer of the epidermis is located just beneath the stratum corneum?
The layer beneath the stratum corneum is known as the granular cell layer or stratum granulosum. It consists of keratinocytes that have begun to produce keratin and undergo changes in their cellular structure.
What is the layer beneath the stratum granulosum called?
The layer beneath the stratum granulosum is called the prickle cell layer or stratum spinosum. It is characterized by cells with spiny projections, which are cell-to-cell connections called desmosomes.
What is the innermost layer of the epidermis?
The innermost layer of the epidermis is called the basal cell layer or stratum basale. It is made up of a single layer of columnar or cuboidal cells that actively divide and produce new keratinocytes.
Describe the characteristics of the cells in the stratum basale.
The stratum basale is composed of a single layer of squamous cells that are columnar or cuboidal in shape. These cells appear basophilic (blue) and can exhibit variable pigmentation due to melanin. They are attached to the basement membrane by hemidesmosomes.
What is the main component of the stratum spinosum?
The stratum spinosum is the thickest layer of the epidermis, consisting of 5-10 cell layers. Its primary cell type is polyhedral squamous cells known as keratinocytes. These cells appear pink (eosinophilic) and become flatter as they move closer to the skin surface.
What is the characteristic feature of the cells in the stratum granulosum?
The stratum granulosum typically consists of 1-3 layers of flattened cells that contain keratohyaline granules. These granules are basophilic and contain lipids, contributing to the waterproofing function of the skin.
Where is the stratum lucidum found, and what are its characteristics?
The stratum lucidum is found exclusively in acral sites, such as the palms and soles, which have a thickened layer of keratin. It is a clear layer of dead keratinocytes.
Describe the characteristics of the cells in the stratum corneum.
The stratum corneum consists of polyhedral eosinophilic keratinocytes that are packed with keratin filaments. These cells lack a nucleus and exhibit a basket weave pattern of keratin arrangement.
How are keratinocytes held together?
Keratinocytes, the most dominant cell type in the epidermis, are held together by desmosomes. Desmosomes are specialized cell junctions that provide strong adhesion between adjacent keratinocytes, contributing to the structural integrity of the epidermis.
How are keratinocytes anchored to the basement membrane?
Keratinocytes are anchored to the basement membrane by hemidesmosomes. Hemidesmosomes are specialized adhesion structures that connect the basal cells of the epidermis to the underlying basement membrane, providing stability and support.
What is the significance of desmosomes in the epidermis?
Desmosomes play a crucial role in maintaining the “spongiotic” nature of the epidermis by highlighting the prickles or spines observed between keratinocytes. These desmosomal connections contribute to the strength and flexibility of the skin.
What role do keratinocytes play in re-epithelization and repair?
Keratinocytes are actively involved in the process of re-epithelization and repair. When the skin is injured or damaged, keratinocytes proliferate and migrate to cover the wound, facilitating the regeneration and healing of the epidermis.
What is the origin of melanocytes?
Melanocytes are dendritic cells that originate from the neural crest during embryonic development. They are not epithelial cells but rather neural crest-derived cells.
Where are melanocytes located within the skin?
Melanocytes are located in the basal layer of the epidermis, which is the innermost layer. They occur approximately every 1 in 4 basal cells (keratinocytes).
How do melanocytes appear under microscopic examination?
Melanocytes are smaller than basal cells and can be identified by their elongated oval nuclei with a surrounding clear space, known as a halo.
What is the role of melanocytes in skin coloration?
Melanocytes produce melanin within melanosomes, which are pigment-containing organelles. The melanin is then transferred to neighboring basal cells, including those in hair follicles, contributing to the coloration of the skin, hair, and eyes.
What is the function of melanin?
Melanin acts as a natural pigment that absorbs harmful ultraviolet (UV) rays from the sun. It helps protect the skin from UV-induced damage, including sunburn and DNA damage.
What are Langerhans cells?
Langerhans cells are dendritic antigen-presenting cells. They play a role in the immune response by capturing antigens and presenting them to other immune cells.
Where are Langerhans cells located?
Langerhans cells are found in the mid to upper spinous layer of the epidermis and also in the dermis. They are also present in various types of squamous epithelium, other epithelial tissues, and lymphoid organs.
What is the significance of Langerhans cells in pathology?
Langerhans cells are involved in various pathological conditions. Dysfunction or abnormal behavior of Langerhans cells has been associated with certain skin diseases and immune disorders.
Can Langerhans cells be easily seen on routine histological staining?
Langerhans cells cannot easily be seen on routine hematoxylin and eosin (H&E) staining. Special staining techniques, such as immunohistochemistry, are often required to visualize and identify these cells.
What is the origin of Merkel cells?
Merkel cells originate from the neural crest, similar to melanocytes. They are specialized cells involved in sensory perception.
Where are Merkel cells located within the skin?
Merkel cells are located in the basal layer of the epidermis, similar to melanocytes and Langerhans cells.
What is the function of Merkel cells?
Merkel cells function as slowly adapting mechanoreceptors responsible for tactile sensation. They are associated with sensory nerve endings and play a role in the perception of touch and pressure.
In which areas of the body are Merkel cells more abundant?
Merkel cells are found in increased numbers in specific regions of the body, such as the digits (fingers, toes), lips, and areas with high tactile sensitivity.
Can Merkel cells be easily visualized on routine histological staining?
Similar to Langerhans cells, Merkel cells cannot be readily seen on routine H&E staining. Special staining techniques, such as immunohistochemistry, are typically employed to identify and visualize these cells.
What is the composition of the basement membrane?
The basement membrane is primarily composed of type IV collagen, which provides structural support and stability.
What is the role of the basement membrane in resisting shearing forces?
The basement membrane possesses the ability to resist shearing forces. This property helps maintain the structural integrity of tissues and prevents the separation of epithelial and connective tissue layers.
What is the structural significance of the basement membrane?
The basement membrane acts as a structural scaffold that provides support and anchorage for epithelial cells. It helps maintain tissue architecture and separates epithelial tissue from underlying connective tissue.
How does the basement membrane control epithelial-mesenchymal interactions?
The basement membrane plays a crucial role in regulating the interactions between epithelial and mesenchymal cells. It acts as a barrier, preventing the invasion of mesenchymal cells into epithelial tissue and maintaining tissue organization.
What is the composition of the dermis?
The dermis is primarily composed of dense connective tissue, which includes collagen, elastin, and extracellular matrix components. These provide strength, elasticity, and support to the skin.
What are the functions of the dermis?
The dermis plays a vital role in supporting the overlying epidermis. It houses various structures, including nerves, blood vessels, lymphatics, and mechanoreceptors/thermoreceptors. It also contains epidermal appendages such as hair follicles, sebaceous glands, and sweat glands.
