Structure of the Skin Flashcards
Where does the epidermis of the skin originate from?
Ectoderm
Where does the dermis of the skin originate from?
Mesoderm that comes in contact with the inner surface of epidermis
What happens week 5 in skin development?
- Epidermis forms as a single layer of cuboidal cells
- Secondary layer of squamous, non keratinising cuboidal cells (periderm) form
- Periderm generates white, waxy protective substance - vernix caseosa
What is the periderm?
Cells with projecting globules covered with small protusions
What happens around week 11 of skin development?
Basal layer of cuobidal cells (stratum germinativum) proliferates to form multilayered intermediate zone
What happens around week 20 of skin development?
Further differentiation of the cuboidal cells into spinosum, granulosum, lucidum and corneum
Superficial strata: Spinosum
Spinous
Superficial strata: Granulosum
Granular
Superficial strata: Lucidum
Clear, found on palms of hands and sole of feet
Superficial strata: Corneum
horny
What happens between weeks 9-13? (hair follicles)
Development of hair follicles in stratum germinativum and appearance of lanugo hair
What happens weeks 12-14? (dermis)
Epidermal ridges protrude as troughs into developing dermis beneath (rete ridge)
Structure of the skin superficial to deep
Epidermis , Basement membrane, Dermis, Subcutaneous fat
What is called the building blocks of eppidermis in the skin?
Keratinocytes
Division of cells in basal layers (progressive differentiation/flattening towards surface away from basal membrane)
Basement membrane, basal layer, spinous layer, granular layer, stratum corneum
Stratum lucidum found only?
Palms and soles (no nuclei or organelles)
Which cells in basal layer do not have nuclei or organelles?
Stratum lucidum and corneum
Cellular progression from basal layer in how long?
30 days
Filamentous cytoskeleton of keratinocytes comprises of:
Actin- containing microfilaments (7nm)
Tubulin containing microtubules (20-25nm)
Role of Keratins (5)
Structural properties, cell signalling, stress repsonse, apoptosis, wound healing
Role of desmosomes (3)
Major adhesion complex in epidermis
Anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes
Allows cells to withstand trauma
Role of gap junctions (2)
directly form connections between cytoplasm of adjacent keratinocytes
cell synchronization and coordination
Role of adherens junctions (1)
engage with actin skeleton
Role of tight junctions (1)
Role in barrier integrity and cell polarity
Melanocyes function (1)
Distribute melanin pigment to keratinocytes
(dendritic)
Langerhnas cells (1)
Antigen presenting cells
(dendritic)
Merkel cells function (1)
mechanosensory receptor
Structure of the basement membrane (1)
(Aka dermal-epidermal junction)
Proteins and glycoprotiens
Proteins and glycoproteins found in basement membrane
Collagen (IV, VII)
Laminin
Integrins
Role of basement membrane (4)
Cell adhesion
Cell migration
Diffusion of bioactive molecules
Rete ridges
Dermins function (1)
extracellular matrix- provides resilience
Two layers of dermis are …
Papillary dermis
Reticular dermis
Papillary dermis (3)
Superficial
Loose connective tissue
Vascular
Reticular Dermis (3)
Deep
Dense connective tissue
Forms bulk of dermis
Glycoproteins found in dermis (3)
Fibronectin, fibulin, integrins
Role of glycoproteins in dermis (1)
Facilitate cell adhesion and cell motility
Proteins in skin with proportions (2)
Collagen (80-85%)- mianly type I and III
Elatin fibres (2-4%)- fibrillin, elastin
Where is ground substance found in terms of the dermis?
Between dermal collagen and elastic tissue
Primary cells present in dermis:
Fibroblasts
Blood supply of skin
Deep and superficial vascular plexus
Autonomic innervation of skin (2)
Cholinergic- eccrine
Adrenergic- eccrine and apocrine
What’s in a pilosebaceous unit?
The hair follicle itself with an attached sebaceous gland and arrector pili muscle
What three body sites has the highest sensory innervation?
Face
Extremeties
Genitalia
Innervation of dermis
Afferent nerves- Corpuscular – Encapsulated receptor e.g corpuscle (Meissner)
Innervation of epidermis
Afferent nerves — Free — Non encapsulated receptors e.g Merkel cell
Meissner’s corpuscle aka
Tactile corpuscle
Where Meissner’s corpuscle located?
Superficial dermis
Where are Meissner’s corpuscle most concentrated?
Thick hairless skin e.g finger pads and lips
Ruffini Corpuscle aka
Bulbous corpuscle
What is Ruffini Corpuslce?
Slow acting mechanoreceptor
Where is Ruffini Corpuslce located?
Deeper in dermis
HIghest density of Ruffini Corpuscle?
Around fingernails
What is Ruffini Corpuscle sensitive to?
Skin stretch
Role of Ruffini Corpuscle (1)
Monitors slippage of objects
Pacinian corpuscle aka
Lamellar corpuscle
What is Pacinian corpuscle ?
Rapidly adapting (phasic) mechanoreceptor
What are Pacinian corpuscle sensitive to?
Deep pressure and vibration
Where Pacinian corpuscle ?
Dermal papillae of hands and feet
What are Merkel Cells?
Non-encapsulated mechanoreceptors
What are Merkel cells sensitive to?
Light/sustained touch, pressure
Location of Merkel cells
Stratum basale, directly above basement membrane
Area with highest density of Merkel cells
Fingertips
Merkel cells also found in …
Palms, soles, oral and genital mucosa
Fibre of Merkel and Meissner cells
AB
Insert fibres and modality
at some point
Role of microbiota skin (2)
Chronic disease, Immune- modulation and epithelial cell
Function of the skin (6)
Immunological barrier
Physical barrier
Thermoregulation
Sensation
Metabolism
Aesthetic appearance
Continue from skin function
