Anatomy of the skin Flashcards
What are the three main layers of the skin?
Epidermis, Dermis, Hypodermis.
What are the primary cell types found in the epidermis?
Keratinocytes and Melanocytes.
What are the five layers of the epidermis in order?
1) Stratum Germinativum/Basale, 2) Stratum Spinosum, 3) Stratum Granulosum, 4) Stratum Lucidum (only in thick skin), 5) Stratum Corneum.
What is the Stratum Germinativum/Basale composed of?
A single layer of cuboidal or columnar cells.
What is the significance of the Stratum Lucidum?
It is present only in very thick epidermis, like on palms and soles, and lies before the Stratum Corneum.
How many layers of cells make up the Stratum Corneum?
5-50 layers of flattened, dead cells (squames).
What are the key components of the dermis?
Connective tissue, blood vessels, nerves, hair follicles, arrector pili, glands (sweat, sebaceous), and various cells like fibroblasts, histiocytes, mast cells, and lymphocytes.
What are the two layers of the dermis?
Reticular Layer (thick collagen, lower layer) and Papillary Layer (fine collagen, upper layer).
What are the functions of the hypodermis?
Insulates the body and stores energy.
Which skin layer contains fibroblasts, histiocytes, mast cells, and lymphocytes?
The Dermis.
What is the first layer of the epidermis and its characteristics?
Stratum Germinativum/Basale; a single layer of cuboidal/columnar cells that adhere to the basement membrane via hemidesmosomes. Basal cells differentiate into keratinocytes over 14 days.
What is the role of the Stratum Spinosum?
It consists of several layers of polyhedral cells where keratin-tonofibrils insert into desmosomes, and keratinocytes contain lamellar bodies, which form a water barrier and cement cells together.
What function do Langerhans Cells serve?
They are antigen-presenting cells with a macrophage-like function, located in the Stratum Spinosum, and play a role in immune defense.
Describe the Stratum Granulosum.
It consists of 3-5 layers of flattened cells, where keratinocytes lose their nuclei and contain keratohyalin granules, essential for keratinization.
What is the Stratum Lucidum and where is it found?
A clear, lucid layer of flattened cells, found only in very thick layers of epidermis (e.g., palms and soles). Cells here lack nuclei and organelles.
What is the composition and function of the Stratum Corneum?
The Stratum Corneum consists of 5-50 layers of flattened, dead cells (squames) devoid of nuclei and organelles. It serves as a protective barrier and retains moisture.
What are the functions of keratinocytes in the epidermis?
Keratinocytes form the keratinized stratified squamous epithelium, contain keratin proteins, and participate in keratinization, where they differentiate and aggregate keratin filaments into tonofilaments, anchoring desmosomes to the cytoskeleton.
What is the role of Melanocytes in the epidermis?
Melanocytes synthesize melanin pigment, which is transferred to keratinocytes to absorb UV radiation, contributing to skin pigmentation.
What is the function of Merkel Cells in the epidermis?
Merkel Cells, located in the Stratum Basale, are associated with nerve endings and possibly have a neuro-endocrine function, acting as sensory mechanoreceptors.
What is the process of epidermopoiesis and how long does it take?
Epidermopoiesis is the continual renewal of the epidermis through basal cell division. The turnover rate is approximately 6 weeks, with basal cells becoming keratinocytes and reaching the stratum corneum in about 14 days.
What is the Dermal-Epidermal Junction?
It is the area where the Stratum Basale of the epidermis attaches to the basement membrane, connecting the epidermis to the dermis.
What cells are found in the Stratum Basale at the Dermal-Epidermal Junction?
Basal keratinocytes, melanocytes, and Merkel cells.
What is the function of hemidesmosomes in the Dermal-Epidermal Junction
Hemidesmosomes on basal cells attach the epidermis to the basement membrane, maintaining adhesion between the dermis and epidermis.
What are the components of the basement membrane?
The basement membrane consists of the Lamina Lucida, which contains anchoring transmembrane filaments of the hemidesmosomes, and the Lamina Densa, a lattice structure made of type IV collagen.
What is the role of melanocytes at the Dermal-Epidermal Junction?
Melanocytes, interspersed among basal cells, are large dendritic cells responsible for melanin pigment production.
What is the likely function of Merkel cells in the Stratum Basale?
Merkel cells likely have a neuro-endocrine function and contain small, dense granules of catecholamines.
What is the predominant protein in the dermis?
Collagen
What is the function of collagen in the dermis?
Collagen is a very tough, fibrous protein with high tensile strength, providing structural support to the skin.
What role does elastin play in the dermis?
Elastin provides elasticity to the skin, allowing it to deform and return to its original shape (deformity with memory).
What are Glycosaminoglycans (GAGs), and what is their function in the dermis?
GAGs absorb water and provide viscosity to the skin. They consist of a hyaluronan backbone with glycoprotein branches.
What is the primary composition of the hypodermis?
The hypodermis is mostly composed of fat (adipose cells), along with blood vessels and nerves.
Where is the hypodermis thickest in the body?
The hypodermis is thickest in the abdomen.
What are the main functions of the hypodermis?
The hypodermis insulates the body and stores energy.
