1 to 3 layers of fusiform shaped basophilic cells Containes granules (Keratohyalin granules) contain profilaggrin and Loricrin proteins .
Stratum corneum: * Superifical keratinized layer Cells * Almost filled with keratin * Flattened, non nucleate * Coated with extra-cellular lipids that form water barrier of skin
* Provide Mechanical protection, barrier for water loss *Layer that varies most in thickness thick palm & sole (20-30 cell layers thin other area ( 3-4 cell layers)
EPIDERMAL CELLS: KERATINOCYTES: *80-85% of epidermis *Ectoderm in origin *For keratin
formation *They are arranged In many layers that continuously shed * regenerate every 4 weeks *Psoriasis 4days
MELANOCYTES: *Found in between cells of the basal layer & At the basal part of the hair follicles. *Origin neural crest *Branched cells with centeral nuclei *They produce the Melanin to keratinocytes color to the skin
*No. of melanocytes for the same site is same in white and black skin. *Provide protection from UV light LANGERHANS CELLS: *Found in upper layers of st.spinosum *Have branched shape
& central nuclei *Represent 3-8%of epid. Cells *Bone marrow in origin. *Phagocytic & antigen presenting cells (Immune response)
MERKELS CELLS: *Found in basal cell layer *Are modified epidermal cells *Sensory nerve fibers *form terminal disk
under Merkels cells *Function as touch receptors The Dermis The DERMIS: Connective tissue layer
composed of collagen & elastic fibers, fibroblasts, macrophages & mast cells. Contains hair follicles, glands, nerves & blood vessels Two major regions of dermis
papillary region reticular region PAPILLARY DERMIS: Upper part of dermis Top 20% of dermis Contain finer collagen compared to reticular dermis
Finger like projections are called dermal papillae anchors epidermis to dermis contains capillaries that feed epidermis contains Meissners corpuscles (touch) & free nerve endings for sensations of heat, cold, pain, tickle, and itch Meissners (Tactile) Corpuscle:
RETICULAR DERMIS: The thicker deep layer Dense irregular connective tissue Contains interlacing collagen and elastic fibers contain sweat glands , fat & hair follicles Provides strength, extensibility & elasticity to skin
Contain many nerve receptors: Ruffini corpuscles pressure touch. Pacinian corpuscles vibratory pressure & touch Basement membrane zone
(BMZ) It forms the interface between the epidermis and the dermis. It is continuous along the epidermis and skin
appendages. Its width ranges between 50-90 nm. It is divided into: 1- Plasma membrane and hemidesmosomes of basal keratinocytes.
2- Lamina lucida 3- Lamina densa 4- Sublamina densa fibrillar zone Basement Membrane Zone: Main functions: 1- Attach the epidermis to the dermis.
2- Separate components of the epidermis and dermis. 3- Provide resistance against external shearing forces. 4- Maintain tissue architecture during remodeling and repair. Subcutaneous fat tissue
the layer between the dermis and the fascia The fat tissue acts as a cushion against external physical pressure, retain moisture . The thickness of the subcutaneous tissue depends on the body site, age and other factors Fat cells separated by the connective fibroid fat septum are called fat lobules.
Vascular channels and nerves: Subcutaneous plexus Deep Dermal-subcutis interface Large blood vessels
Subpapillary plexus superficial Parallel to epidermis Thank You
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