Integument Flashcards
What are the 6 essential functions of skin?
Barrier, immunological (antigen processing),homeostatic (body temperature and water loss), endocrine (secrete hormones, growth factors and hormones), excretion (sweat), and conveys sensory information about the external environment to the nervous system (temperature, surface texture)
what are the layers of skin?
Epidermis, dermis, and hypodermics (layer of subcutaneous tissue)
What two epidermal derivative are not found in thick skin?
Hair follicles/hair and sebaceous glands
What determines if skin is thin or thick?
The thickness of the epidermal layer
What are the layers of the epidermis?
Corneum (dead, keratinized cells), lucidium (can only be seen in thick skin), granulosum (cells that about to die), spinosum (maturing and slowly dying cells), basale (can differentiate).
MNEMONIC: Come, let’s get sun burnt
Keratinocytes
Most abundant cell type. Attached to each other via desmosomes and attached to the basal lamina by hemis.
Apoptosis of keratinocytes
They are proteolytically cleaved on the desmosomes, which allows them to move through the layers until they reach the corneum where they are sloughed off
Keratins
Strengthen the keratinocyte, makes up about 85% of it.
Lamellar Bodies
water barrier in keratinocytes
Melanocytes
Derived in the neural crest(dendritic cells with long cytoplasmic extensions). Can replicate throughout life
How do melanocytes appear on an EM?
Clear with a large elongated nucleus and cytoplasm a cytoplasmic extensions.
What is the function of melanocytes cytocrine secretion?
UV protection through the release of melanin
How is melanin produced?
oxidation of tyrosine to DOPA and DOPA gets transformed into melanin
Langerhans Cells
Originate from a common lymphoid progenitor. Present antigens to the T cells in lymph nodes. No desmosomal junctions. Involved in delayed-type hypersensitivity reactions (type of allergic reaction)
How do langerhans look on EM?
Dendritic processed, clear cytoplasm and dark nucleus, nucleus is indented, possess birbeck granules which look like tennis rackets
Merkel’s Cells
Least numerous. Dendritic cells. Detect touch sensations, found where sensory perception is acute (fingertips). Contain desmosomes and keratin. Antigenic markers of both epidermal and neural type cells.
How do Merkels cells look on EM?
Lobed nucleus, neurosecretory granules in the cytoplasm
Merkels Corpuscle
Area that is closely associated with the expanded terminal bulb of afferent myelinated nerve fivers
Stratum Basale
Bottom layer. Single layer of cuboidal cells. Contains keratinocyte stem cells, melanocytes, and Merkel cells. Provides for epidermal cell renewal. Attached to basal lamina by hemidesmosomes, and extensively attached to other cells by desmosomes .
How does the stratum basale look?
Closely packed nuclei with little cytoplasm. Intensely basophilic (dark)m with many melanin granules.
Stratum Germinativum
Keratinocyte stem cells