Dermatology Flashcards
What is the epidermis?
Outermost layer of skin.
Where does the epidermis originate from?
Ectoderm.
What is the dermis?
Layer of skin inbetween basement membrane and subcutaneous fat.
Where does the dermis originate from?
Mesoderm.
How does skin development start?
Single layer of cuboidal cells form and make up the surface ectoderm. Secondary layer of squamous non keratinising cells form on top and these cells are know as the periderm.
What do the periderm cells do in early skin development?
Secrete vernix caseosa which is a white waxy protective substance.
What happens later on at week 11 of skin development?
Basal layer of cuboidal cells proliferate to form multilayer intermediate zone. Basal layer of cuboidal cells is now know as the stratum basale.
What happens at week 20 of skin development?
Further differentiation forms spinosum, granulosum, lucidium and corneum.
Where do hair follicles develop from?
Stratum basale.
What are the epidermal ridges that protrude into the dermis known as?
Rete ridges.
What is the superficial layer of the dermis known as?
Papillary dermis.
What are the skin layers from top to bottom?
Epidermis, basement membrane, dermis and subcutaenous fat.
What cells make up the epidermis?
Keratinocytes.
Where does cell division occur in the skin?
Stratum basale.
What are the layers of the epidermis from bottom to top?
Stratum basale, stratum spinosum, stratum granulosum, Stratum lucidum and stratum corneum.
What occur as you go up the layers of the epidermis? And why is this a problem in some diseases?
Differentiation and flattening of cells. This process can be accelerated in skin diseases such as psoriasis.
Why is the stratum lucidum different from other epidermal layers?
Only present in palms and soles.
Describe the stratum corneum?
Outermost layer of the epidermis. Contains no nuclei or organelles.
Describe the stratum lucidum?
Only present in palms and soles. No nuclei or organelles.
What does the keratinocyte cytoskeleton contain?
Actin containing microfilaments. Tubulin containing microtubules. Intermediate filaments which are the keratins.
Functions of keratins?
Structural properties. Cell signalling. Wound healing.
What are between keratinocytes?
Tight junctions, adherens junctions, demosomes, gap junctions.
What is the function of desmosomes?
Major adhesion complex. Anchor intermediate filaments to cell membrane and bridge adjacent keratinocytes. Provide strength.
What are gap junctions and what do they do?
Contain intercellular channels. Form connections between cytoplasm of adjacent keratinocytes.
What complex/junction inbetween keratinocytes are essential for cell synchronization and metabolic coordination?
Gap junctions.
What are adherens junctions and what do they do?
Transmembrane structures that engage with the actin skeleton.
What do tight junctions do?
Role in barrier integrity and polarity.
What epidermal cells other than keratinocytes are present?
Melanocytes, langerhans cells, merkel cells and mast cells.
Describe melanocytes
Dendritic cells that distribute melanin pigment to keratinocytes.
What are melanocytes derived from?
Neural crest.
What results in different skin colours?
Amount of melanin produced varies. Number of melanocytes are the same.
What are langerhans cells?
Dendritic antigen presenting cells.
What are merkel cells?
Mechanosensory receptors.
- involved in sensation.
What does the basement membrane contain?
Collagens, laminin and integrins.
What are the most prominent types of collagen in the basement membrane?
IV, VII
What is the function of the basement membrane?
Cell adhesion, gate keeping functions for cell migration and diffusion of molecules. Presence of rete ridges.
Function of rete ridges?
Strength and provides specialised environment for epidermal stem cells.
What is the dermis and what is its function?
Extracellular matrix that provides strength.
What are the two main layers that make up the dermis?
Papillary dermis and reticular dermis.
Describe the papillary dermis
Superficial layer of the dermis that is made up of connective tissue and is highly vascular.
Describe the reticular dermis
Dense connective tissue that forms bulk of dermis.
What proteins does the dermis contain?
Collagen, fibrillin and elastin.
What glycoproteins does the dermis contain?
Fibronectin, fibulin and integrins.
What do the glycoproteins in the dermis do?
Facilitate cell adhesion and cell motility.
Where is the ground substance located in the dermis?
Between dermal collagen and elastic tissue.
What makes up the ground substance?
Glycosaminoglycans and proteoglycans.
What is the primary cell in the dermis?
Fibroblasts.
What other cells apart from fibroblasts are present in the dermis?
Mast cells, neutrophils and lymphocytes.
Where is the skin blood supply present?
Dermis. Does not cross into epidermis.
Eccrine vs apocrine sweat glands?
Eccrine secrete directly onto skin surface while apocrine secrete into hair follicle.