Integumentary 1 Flashcards
What are the two layers of the integumentary system?
-epidermis and dermis
Epidermis-epithelium + cells
- keratinized stratified squamous epithelium
- derived from ectoderm
Dermis- dense connective tissue
-derived from mesoderm
What is the hypodermis?
Found deep to (beneath). The dermis
-often referred to as the subcutaneous fascia in gross anatomy
What is contained in the hypodermis?
Contains variable amounts of adipose tissue (panniculus adiposus) arranged in lobules and separated by connective tissue septa
Can find hair follicles, glands and mechanireceptors in this layer
In what countries are the hypodermis thick?
Cold countries
What. Are the associated appendages of the hypodermis?
- hair follicles
- sweat glands
- sebaceous glands
- nails
- mammary glands
What are the functions of skin?
Barrier
- immunological role- presents antigens to the lymphatic tissue
- homeostasis-regulation of body temperature and water loss
- Sensory information- samples the external environment and relays this information to the nervous system
- Endocrine functions- secretes hormones, cytokines and growth factors, converts vitamin D into its hormonally active from D3
Excretion- secretes sweat and other products from the body
What is the largest population of cells in the integumentary system?
Keratinocytes
What are the pigments producing cells in the integumentary system?
Pigment producing cells of the epidermis
-makes up about 5% of the cell population
What is the merchankreceptor in the epidermis?
Merkel cells
Merchanoreceptors
- associated with sense nerve endings
- constitutes 6%-10% of cells in the epidermis
What are langerhans cells?
Antigen presenting cells (APC’s)
-plays a role in the immunological function of skin
-accounts fir 2%-5% of cells
What are keratinocytes?
- Constitutes most of the cell types (85%) of the epidermis
- Differentiates. From basal layer, and continues throughout all layers of the epidermis
What are the functions of keratinocytes?
- produces keratin (cytokeratin) - mainly the keratinocytes of stratum basale
- produce keratohylain granules- cells in spinosum & granulosum
- contributes to the formation of the epidermal water barrier
Where are melanocytes located?
Melanocyte to keratinocytes ratio 1:4 to 1:10
-varies according to the region of the body
Where are melanocytes located?
Located in the basal layer (stratum basale)
What are the origins and formations of melanocytes?
Originates from neural crest
- Appear clear with elongated nuclei
- Multiple cytoplasmic processes that extend between keratinocytes
- 1 melanocytes can communicate with up to 40 keratinocytes
- No desmosome connections but are attached to the basal lamina via hemidesmosomes like structures
- lacks keratin filaments
- Cytoplasm contains oval dark staining premelanosomes (responsible for the synthesis of melanin)
What are the functions of melanocytes?
- Produce melanin that is transferred to surrounding keratinocytes (cytocrine secretion)
- UV protection
- Skin color-amount and ratio of melanin types present
- Lighter skinned individuals have increased melanin degradation
-Oxidation of tyrosine to 3,4 dihydroxyphenylalanine (DOPA) and subsequent transformation of DOPA into melanin
How are mature melanosomes formed?
Premelanosomes formed by Golgi-transformed into early melanosomes
Contain tyrosinase molecules and small amounts of melanin
Conversion. Into melanin gradually occurs until the. Mature melanosome is forned
What are the factors associated with skin pigmentation?
-UV Radiation- melanin production is influenced by the surrounding keratinocytes in response to UV radiation
- Melanin distribution- dispersed differently in light vs dark skinned persons
- Light skinned persons- concentrated in stratum basale
- Dark skinned persons- dispersed throughout stratum basale and spinosum
Type of melanin-each type of melanin has a different function and is driven by different genetic factors
- The pigment produced by melanocytes consist of two different forms+eumelanin and pheomelanin
- The ratio between the two determines skin and hair color
Describe eumelanin
Protection against UVR damage
- scatter and absorb UV rays and eliminate UV generated free radicals
- Degrades faster in lighter skinned individuals
Describe pheomelanin
-Allows a greater amount of light to pass through thereby increasing vitamin D production at altitudes where light intensity is low
Found more commonly in atypical nevi and melanomas
Increased oxidative damage
Describe langerhans origins
Originate from common lymphoid progenitor (CLP)
-Present in all epidermal layers but most easily recognized in stratum spinosum
What is the function of langerhans?
Immunological role
- Encounters, processes and expresses antigens (Antigen presenting cell(APC))
- Migrates to the lymph node to present the antigen to T-lymphocytes
- Express both MHC-1 and MHC-2 and receptors for IgG
- Involved in delayed type hypersensitivity reactions
What do Langerhans look like under light microscopes?
Nucleus stain well with hematoxylin (blue)
Cytoplasm is clear
Describe the TEM structure
Nuclear membrane- indented structure making the nuclear profile uneven (“N” On right TEM image)
Possesses tennis racquet shaped granules (Birbeck granules)-
- small linear (rod-like) structure with a bublbous expansion (vesicle) at one end
- regular cross striations
- function unclear but may be part of the endosome system
