Histology of Skin Flashcards
Be able to describe the location, structure, and distinguishing features of the following epidermal layer: stratum germinativum (stratum basal)
a. Single layer of cells adjacent to basal lamina
b. Cells are tall cuboidal or columnar
c. Hemidesmosomes along cell membrane adjacent to basement membrane; other regions of cell membrane have typical desmosomes
d. Cells are mitotically active: cell proliferation is occurring in this layer
e. Cytoplasm of cells contains numerous polyribosomes and intermediate filaments
Be able to identify which epidermal layers are mitotically active.
Stratum germinativum and stratum spinosum (albeit with less activity)
Be able to describe the location, structure, and distinguishing features of the following dermal layer: papillary layer of the dermis
- Superficial layer of dermis
a. immediately beneath basement membrane - Composition
a. Loose connective tissue
(1) Thin bundles of collagen fibers
(2) Some reticular and elastic fibers
(3) More cellular than reticular layer - Vascular papillae
a. Papillae contain capillary loop projections
(1) Only source of nourishment for epithelial cells
(2) Thermoregulatory devices - Nervous papillae
a. Contain special nerve terminations
(1) Meissner’s corpuscles (mechanoreceptors)
(2) Krause end bulbs (mechanoreceptors)
Be able to describe what the hypodermis is and where it is found.
A. Not part of skin
B. Composition
1. Loose connective tissue
a. Frequently contains large accumulations of fat cells
(1) When continuous lobules of fat are present the hypodermis forms a
fat pad, the panniculus adiposus
(2) Abdomen: panniculus adiposus can be 2-3 cm thick
b. Fat is absent in hypodermis of eyelids, penis, and scrotum
Be able to describe the process of keratinization.
a. Synthetic phase
(1) Intermediate filaments, keratohyalin granules, membrane-coating granules and filaggrin and trichohyalin proteins are formed in large numbers
b. Degradative stage
(1) MCGs contents (lipid) discharged into intercellular spaces
(a) Thickened cell envelope is result
(2) Lysosomal enzymes degrade synthetic organelles
(a) Filaments and keratohyalin remain unaffected
(3) Filaments and keratohyalin consolidate into a fibrous-amorphous mass
Be able to describe the formation of melanin, the cells involved in melanin formation, and skin pigmentation.
Melanosome formation
a. Formation of pre-melanosome
(1) Rough endoplasmic reticulum: forms enzymes with tyrosinase activity
(2) Golgi apparatus: packages enzymes in a membrane-bound vesicle: the pre-melanosome
Deposition of melanin in the pre-melanosome
(1) Gradual obliteration of internal structure as melanin is deposited
(2) Gradual decline in tyrosinase activity as pre-melanosome “matures”
Be able to describe the structure and function of the following associated integumentary structures: hair, nails, glands (eccrine or merocrine sweat glands; apocrine sweat glands; and sebaceous glands), arrector pili muscle, and sensory structures.
a
Be able to describe the functions of the following cells: Merkel cells, Langerhans cells, melanocytes, and keratinocytes.
a
Be able to describe the generalized pattern of skin vascularization. Be able to define and describe the function of what an arteriovenous anastomosis is.
a
Be able to distinguish the differences between thick and thin skin.
a
Be able to describe the process of skin wound healing, and the different kinds of skin grafts.
a
Be able to describe the differences in skin damage due to sunburn, first, second, and third degree burns.
Sunburn
- Redness due to injury to capillaries and venules in papillary layer of dermis
o Vessels become widely dilated
o Increased circulation
- Increased production of melanin and epidermal thickening
1st Degree
- only epidermal damage only
- may or may not blister
2nd Degree
- epidermal and dermal damage
- usually good regeneration of tissues occurs
3rd Degree
- Epidermis and dermis destroyed
- Grafts usually necessary to repair wound
Be able to describe the location, structure, and distinguishing features of the following epidermal layer: stratum spinosum
a. Variable thickness; can be several cell layers deep; immediately above stratum germinativum
b. Cells are polygonally shaped
c. Some mitotic activity (but less than that found in stratum germinativum)
d. Numerous desmosomes; during fixation, cells frequently shrink slightly
(a) Cell membranes pull back except at desmosomal contact points
(b) Gives cell a “prickly” appearance
e. Cytoplasm contains many bundles of intermediate filaments (tonofibrils) representing cytokeratins
f. Membrane-coating granules (keratinosomes) appear in cytoplasm
(1) Membrane-bound; contain lipid substance
(2) Tend to accumulate in superficial regions of cell beneath plasma membrane
(3) Thought to deposit a “toughening” layer on the surface of the cell membrane
Be able to describe the location, structure, and distinguishing features of the following epidermal layer: stratum granulosum
a. Three to five layers thick
b. Flattened polygonally-shaped cells (parallel to basement membrane)
c. No mitotic activity
d. Keratohyalin granules appear in cytoplasm
(1) Extremely basophilic
(2) Not membrane bound
(3) Probable precursor to keratin
e. Nucleus becomes pyknotic (starts disappearing)
Be able to describe the location, structure, and distinguishing features of the following epidermal layer: stratum corneum.
a. Outermost layer of epidermis
b. Thickness and numbers of layers of cells varies considerably
c. Cella re clear; dead; flattened, fused
d. Cytoplasm has become completely “keratinized”
(1) Eleidin is apparently transformed to keratin
