Skin Overview Flashcards
What is the dermis?
Under the epidermis, consisting mostly of dense connective tissue. Two sublayers.
What is the epidermis?
The most superficial layer of skin and is stratified keratinized squamous epithelium. Non-vascularized.
What is the papillary layer of dermis?
Just beneath the epidermis and is the interface between the dermis and epidermis. Takes the form of small bumps or papillae.
What is the reticular layer of dermis?
Just below the papllilary layer and is made mostly of dense bundles of collagen fibers and vascular serving the skin. Specialized sensory cells are here, also hair cells, sebaceous glands, and sweat glands.
What is the hypodermis?
Found beneath the dermis. Also known as the superficial fascia. Technically not part of the skin, but because hair follicles, sweat glands and other structures are associated with the layer it is often included in discussion. Loose connective tissue with varying amounts of fat. Major blood vessels are here
Appearance of the epidermis
Very dense and composed of mostly keratinocytes and multiple epidermal sublayers. Superficial layers are less stained (missing nuclei and organelles)
Appearance of dermis
Stains well with eosin because of collagen fibers.
Appearance of the papillary dermis
Thin collagen and elastic fibers and fibroblasts and a dense layer of capillaries to feed the epidermis and regulate temperature.
Appearance of reticular dermis
More thick collagen and elastic fibers, fibroblasts.
Contains glands, hair follicles, and smooth muscle
Appearance of hypodermis
Large accumulations of adipose and some profiles of sweat glands.
5 layers of the epidermis from bottom to superficial
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Describe the stratum basale
Single cell layer, most mitotically active
Mainly responsible for keratinocyte turn over. When new cells are formed vi mitosis, the previous layer is pushed surface ward to join the next layer
Sits on top of the basement membrane and stains dark purple (hematoxylin)
Describe the stratum spinosum
Superficial to the stratum basale. Several layers thick and has many mitotically active cells. Thickest epidermal layer. Adjacent cells are connected by strong adhering junctions and when dehydrated have a somewhat spiny appearance. Keratinocytes with numerous processes are responsible for this spiny appearance.
What is the stratum granulosum?
Superficial to the stratum spinosum. Usually 3-5 cell layers thick and is darkly stained with basophilic granules. These granules are secretory and contribute to the water tight features of this epithelium. Most superficial cell layer of the epidermis in which cell nuclei and organelles are found.
What is the stratum lucidum?
Present only in thick skin (palms of hands and soles of feet), cells devoid of nuclei and organelles. Densely packed keratin filaments and eleidin
What is the stratum corneum?
Most superficial layer which consists of essentially dead cells, but still retain their plasma lemmae with intercellular junctions and cytoplasmic keratin.
Several layers of flattened, keratinized dead cells.
Continually being sloughed off, producing dandruff, and dust
Mitotically active layers of the epidermis
Stratum basale ad stratum spinosum
What are keratinocytes?
Stratified squamous epithelial cells. All layers of the epidermis produce keratin, a fibrous protein. Basal layer is mostly cuboidal to columnar and become more cuboidal as they move toward the surface. Eventually become flattened to look squamous
What is the most plentiful cell type in the epidermis?
Keratinocytes
What are melanocytes?
Located in the basal layer and partially the spiny layer and produce and release melanin
What are Merkel’s cells?
Differntiated epithelial cells that serve as sensory in sense of touch. Contacted by sensory axons known as afferent axons.
What are Langerhans cells?
Located in the stratum spinosum. Mesodermally derived cells that are part of the immune system. Are mobile and serve as antigen detecting and antigen presenting cells.
Two components of barrier function in the skin?
Formation of keratin
Formation of glycolipids
What is the barrier function of skin?
Keratin is an intermediate intracellular tonofilament.
Start to form the precursor keratin proteins in the stratum spinosum.
In the stratum granulosum, large keratohyaline granules and membrane coating granules of glycolipids join to form hydrophobic layer.
Glycolipid is mortar between keratin structural support
