Integumentary System Histology Flashcards
(54 cards)
What are the 2 Main Components of the Integumentary System?
- Skin
2. Epidermal Derivatives
List the epidermal derivatives
- Hair follicles and hair
- Sweat (sudoriferous) glands
- Sebaceous (oil) glands
- Nails
What are the 6 major functions of the Integumentary System?
- protective (barrier against external factors / forces / biological agents)
- immunologic (antigen presenting cells that alert effector cells)
- homeostasis (body temperature and water loss)
- sensory (convey information about the external environment)
- endocrine
- exocrine
What are the 2 principle layers of the skin?
& an additional notable layer
- Epidermis
- Dermis
(additionally, the hypodermis or subcutaneous layer / subcutaneous fascia is deep to the skin)
Epidermis
1 of the 2 principle layers of the skin
- superficial layer
- keratinized stratified squamous epithelium
- embryologically derived from: ectoderm
- avascular (receives nourishment from dermis)
Dermis
1 of the 2 principle layers of the skin
- deep layer
- connective tissue
- derived from mesoderm
- highly vascularized
Hypodermis
Otherwise known as the subcutaneous layer / subcutaneous fascia
- deep to the skin (not a principle layer - the “3rd smaller layer”)
- made of adipose tissue
- vascularized
What are the histological terms for skin?
- Thick Skin
- Thin Skin
(these terms really aren’t accurate, because only the epidermis is being considered, while skin really consists of epidermis and dermis)
Thick Skin
(only referring to epidermal layer)
- found on palms of hands and soles of feet (areas that encounter and high degree of abrasive forces)
- skin is hairless
- much thicker epidermal layer than skin anywhere else
-5 layers/strata
Thin Skin
(only referring to epidermal layer)
- found everywhere except palms of hands and soles of feet
- much thinner epidermis
- hair follicles present in most locations
-4 layers/strata
When considering gross anatomy, where can you find the “thickest skin?”
The upper back (thin epidermis, very thick dermis)
List the Layers/Strata of the Epidermis
(from deep to superficial)
- Stratum Basale (basal layer)
- Stratum Spinosum (spinous layer)
- Stratum Granulosum (granular layer)
- Stratum Lucidum (thick skin only)
- Stratum Corneum
mnemonic: Bad Sprinters Get Leg Cramps
List the Cells of the Epidermis
- Keratinocytes (85%)
- Melanocytes (5%)
- Langerhans’ Cells (2-5%)
- Merkel’s Cells (6-10%)
Keratinocytes
epidermis cell (1/4)
- principle cell type of the epidermis
- produce keratins
- participate in the formation of epidermal water barrier via production of the lamellar bodies
Keratins
produced by keratinocytes
- a major structural protein of the epidermis
- form keratin filaments (intermediate filaments, commonly referred to as tonofilaments)
Lamellar Bodies
- produced by keratinocytes in order to form the epidermal water barrier
- tubular / ovoid-shaped membrane-bound organelle that contain lipids
- these are extorted into the extracellular space between the stratum granulosum and the stratum Corneum
- the epidermal water barrier is important for homeostasis and having dry epithelia)
Melanocytes
epidermis cell (2/4)
function: produce and secrete the pigment, melanin (synthesized and stored in melanosomes)
- have elongated nuclei surrounded by clear cytoplasm
- dendritic cells (rounded cell bodies in the stratum basle with long dendritic processes that extend upward and between keratinocytes in the stratum spinosum)
- Melanosomes will be transferred into adjacent keratinocytes (when they mature, they travel to the ends of dendritic process, accumulate, then go to the adjacent keratinocytes)
Langerhans’ Cells
epidermis cell (3/4)
antigen-presenting cells of the immune system
typically found within stratum spinosum
derived from bone marrow (originate from common lymphoid progenitor cells), then enter the blood stream and migrate into the epidermis, where they encounter and process antigens that enter through the skin
travel through the epidermis through regional lymph nodes where they present processed antigens to the T lymphocytes
in order to ID, must use immunostaining
Merkel’s Cells
epidermis cell (4/4)
mechanoreceptor cells associated with sensory nerve endings
location: stratum basale
contains neurosecretory granules (within cytoplasm)
base of these cells associate with expanded, plate-like terminal of afferent nerve fibers (Merkel’s Corpuscle)
have lobed nuclei
most abundant in areas of acute perception (fingertips)
Stratum Basale
deepest later of epidermis (located adjacent and superior to dermis)
- single layer of basophilic cells
- cells are small and cuboidal / low columnar
- mitotically active later that contains stem cells that give rise to keratinocytes (note that keratinocytes will migrate upwards and differentiate from here)
- this is where the production of intermediate (keratin) filaments begins
Stratum Spinosum
- keratinocytes exhibit numerous cytoplasmic processes (“spines”)
- cell processes are attached to those of adjacent cells via desmosomes (macula adherens)
Intermediate filaments (tonofilaments) are grouped into bundles (tonofibrils)
We see that keratohyalin granules and lamellar bodies will start to be produced here
Cytoplasmic Processes & Histological Prep
during histological prep, cells shrink which leaves expanded intercellular space between spines
this is what contributes to the spiny / prickly appearence
Keratohyalin Granules
Contain proteins that support the aggregation of tonofilaments into tonofibrils
These are produced in Stratum Spinosum, but are also found in other layers
Stratum Granulosum
- intensely basophilic
- varies in thickness (1-3 cell layers)
- keratinocytes contian keratohyalin granules, which will bundle tonofuilaments into tonofibrils
- keratinization is happening here (conversion of granular cells into cornfield cells)
- lamellar bodies are released in the intercellular space b/w stratum granulosum and stratum corneum
