Integument Flashcards
What is the largest organ of the body?
Integument
What are the multiple different tissue types found in the integument?
- Epithelium
- Connective
- Muscle
- Nervous
What are the three layers of the integument?
- Epidermis
- Dermis
- Hypodermis
Functions of Integument:
- Thermoregulation
- Protection from the environment
- Dehydration prevention
- Excretion of wastes/salts
- Absorption
- Sensation
- Beginning of Vitamin D synthesis
- Mate selection (phermones)
What is the most superficial layer of the integument?
Epidermis
What is the Epidermis made of?
Keratinized stratified squamous epithelium
Epidermis lacks ___ and ____
- Innvervation
- Vascularization
Layer that supports the Epidermis via diffusion:
Deeper dermis layer
What are the 5 layers of thick skin (superficial -> deep)?
“Can Louie Get Sun Burned?”
(1) stratum Corneum
(2) stratum Lucidum
(3) stratum Granulosum
(4) straum Spinosum
(5) stratum Basale
What layer is not found in thin skin but is found in thick skin?
Stratum Lucidum
Stratum Basale
- Deepest layer of the epidermis (next to dermis)
- One cell layer thick
- Composed of mitotically active keratinocytes (helps replace lost/dead cells of layers above), and melanocytes and tactile cells (nervous innervation)
- Microscope: cuboidal to columnar-shaped cells
What type of junction connects the basal layer of cells to the basement membrane at the dermal/epidermal junction?
Hemidesmosomes
What type of junction connects the basal layer of cells to each other?
Desmosomes
Stratum Spinosum
- Present between the stratum granulosum (superficially) and the stratum basale (deep)
- Keratinocytes move up from stratum basal (daughter cells) and begin producing keratin (tonofilaments) here
- Microscope: spiny or polygonal appearance (due to keratin)
- Cells superficial to this layer are no longer mitotically active
What is the name used to describe the stratum spinosum and stratum basale together?
Stratum Germinativum
(b/c mitotically active cells present)
What cells are associated with the Stratum Spinosum?
Dendritic Cells (immunity)
Stratum Granulosum
- Present between the stratum lucidum (thick) or corneum (thin) and stratum spinosum
- Composed of 3-5 layers of flattened cells
- Microscope: cells appear very dark
- Cells undergo keratinization process here and fill with keratin (keratohyalin granules)
- Cells also produce lipids (lamellar granules – released via exocytosis into the ISF) to create dehydration and physical barrier
- Cells begin dying as they are pushed more superficially and their cytoplasm is filled with keratins, and organelles begin degrading
- Cell life also limited by diffusion from the dermis
Stratum Lucidum
- Present between the stratum corneum and granulosum in THICK SKIN ONLY
- Composed of 2-3 cell layers attached via desmosomes (cells have lost their nuclei and organelles)
- Microscope: clear (due to the intermediate product of keratin maturation, eleidin)
Stratum Corneum
- Most superficial layer of epidermis so is exposed to the external environment (cells in this layer do not have nuclei or organelles)
- Can have 20-30 layers of dead keratinocyte sheets that are pushed up from the layers below (eventually will be sloughed off)
- Cells at this level are called Squames and have their cell junctions break apart which allows them to come off independently or in chunks
- Layers often break apart during slide processing thus creating an unnatural separation of the layer
What cells are most abundant within the epidermal layer of the integument?
Keratinocytes
Keratinocytes
- Produce the protein Keratin and lamellar granules (both help with integument protection)
- Stores melanin (melanin surrounds the superficial surface of the nucleus to provide UV protection)
What is the role of Keratin?
Provides strength to tissue
What is the role of Lamellar Granules?
Prevents dehydration by forming a lipid barrier
Melanocytes
- Produces and secretes the pigment melanin (DOES NOT STORE)
- Contains long branching processes called melanosomes that transfer melanin to other cells
- Microscope: cells have a round nucleus and clear cytoplasm
- Present in the bottom layers of the epidermis (stratum basale into stratum spinosum)
What is the function of melanin?
- Provides the integument with color
- Provides UV protection
Langerhans Cell (Dendritic Cell)
- Associated with the immune system
- Mostly found in the stratum spinosum of the epidermis
- Finds invaders and presents antigens to T cells
- Microscope: appears paler in comparison to the surrounding keratinocytes, has long extensions, appearance is similar to melanocytes but is found more superficially within the tissue
Tactile Cell (Merkel Cell)
- Located in the stratum basale
- Associated with a deeper nerve ending to send its information signals
- Shares the same origin as keratinocytes
- Detects light touch and pressure, and can provide information on an object’s texture
- Microscope: appears slightly larger than surrounding cells, looks similar to melanocyte but their nuclei are shifted superiorly
- Superiorly shifted nuclei gives space for neurotransmitters to accumulate along the basal surface and interact with the deeper nerve endings
Thick Skin
- Found in areas of high friction or pressure (i.e palms, soles of feet)
- Contains an extra layer in the epidermis, statrum lucidum, and a thicker stratum corneum
- Contains sweat glands but not hair (and associated muscle) or oil (sebaceous) glands
- Associated with visible ridges due to deep integration between dermis and epidermis, forms fingerprints
- Microscope: stratum corneum appears like thick waves due to ridges
Thin Skin
- Found throughout most of the body
- More flexible than thick skin
- Epidermis has 4 main layers and contains hair, sebaceous glands, and sweat glands
- Microscope: stratum corneum is thinner and usually flakey in appearance