Histology Integument Aug 25 2014 (Lecture 1) Flashcards
What are the layers of skin?
Epidermis
What are the 5 layers of the Epidermis?
From top layer to the bottom.
C L G S B
◦ stratum corneum
◦ stratum lucidum
◦ statum granulosum
◦ stratum spinosum
◦ stratum basale (germinativum)
What are the 2 layers of the dermal papillae?
What is the difference between thick and thin skin?
◦ thick skin: epidermis is around 5 mm thick
What do the Keratinocytes in the stratum basale look like?
What do the Keratinocytes in the stratum spinosum look like?
What do the Keratinocytes in the stratum granulosum look like?
What do the Keratinocytes in the stratum lucidum look like?
What do the Keratinocytes in the stratum corneum look like?
What are melanocytes?
◦ specialized cells found in the stratum basale
◦ originate as neural crest cells
◦ melanocytes produce melanin (melanosomes) which are transferred to keratinocytes
◦ MITF (microphthalemia-associated transcription factor
What are Langerhans cells?
◦ dendritic cells (derived from bone
marrow) located in stratum
spinosum
◦ clear cytoplasm, irregularly
shaped nucleus, Birbeck granules
◦ involved in immune responses
◦ antigen-presenting cells
◦ monitor foreign antigens that
contact epidermis
◦ phagocytic cells that leave the
epidermis, enter the lymphatic
system; travel to lymph nodes and
there interact with T cells
◦ activated T cells then travel back
to the epidermis through the
blood stream and release proinflammatory
cytokines to
neutralize the antigen
What are Merkel cells?
◦ resemble keratinocytes
◦ develop from neural crest
◦ found in stratum basale of
specialized areas of the
body such as fingertips
and are associated with the
basal lamina
◦ mechanoreceptors
connected to a myelinated
nerve fiber in the dermis
◦ irregularly shaped nucleus
with granular cytoplasm
What are the steps in wound healing?
- formation of a fibrin-platelet clot ◦ platelets are embedded in a fibrous mesh of fibrin ◦ thrombin cleaves fibrinogen to form fibrin ◦ platelets release platelet-derived growth factor
- Leukocyte recruitment ◦ keratinocytes and endothelial cells express CXC and CXC receptor which recruit neutrophils, monocytes and lymphocytes ◦ monocytes become macrophages ◦ neutrophils release pro-inflammatory cytokines and activate fibroblasts and keratinocytes
- Neovascularization and cellular proliferation ◦ new blood vessels form and organize granulation tissue
- Tissue remodeling ◦ keratinocytes from the stratum basale migrate from the edges of the wound ◦ hemidesmosomes detach and allow movement ◦ matrix metalloproteinases are produced by fibroblasts ◦ epidermal growth factors facilitate re-epithelialization ◦ underlying dermis contracts to bring edges of the wound together ◦ fibroblasts infiltrate and produce Type III collagen
What is Psoriasis?
Psoriasis is an inflammatory skin disorder
◦ initiated by Langerhans
cells
What are the of sensory receptors by stimulus?
◦ mechanoreceptors
What are the 3 types of glandular secretions?
Merocrine
◦ releases secretory product by
exocytosis
Holocrine
◦ the entire cell
becomes the
secretion
Apocrine
◦ releases a
portion of the
cell cytoplasm
with secretion
What are Sebaceous glands?
◦ are associated with
hair follicles or
empty directly
onto the skin
◦ produce sebum
which is a lipid rich
substance that
is oily
◦ holocrine secretion
What are the 2 types of sweat glands?
