Integument Flashcards
Epidermis
Outermost layer of thick and thin skin
Dermis
Connective tissue layer beneath the epidermis that contains specializations like hair. It is connected through the basement membrane.
Hypodermis
Adipose tissue layer that is not part of the integument
Thin skin
Most of the body is covered with thin skin. It contains all layers of the epidermis except the stratum lucidum. The layer of corneum is very thin compared to thick skin.
Thick skin
Thicker layer of skin present in areas of the body like the palms of the hand and soles of the feet. It has a thicker stratum corneum and contains the stratum lucidum layer.
Keratinocytes
Most abundant type of cell in the epidermis that is present within each layer. They contain keratin (intermediate fibers) filaments and are connected to each other by desmosomes.
Langerhan’s cells
Cells within the epidermis that can act as antigen presenting cells and phagocytes. They are derived from monocytes and act as early immunoresponders to bacteria that breaks through the skin.
Merkel cells
Cells within the epidermis that are associated with free nerves and have a sensory role in the skin.
Melanocytes
Cells located within the stratum basale that give rise to pigmentation by synthesizing melanin contained in granules.
Layers of the epidermis
From the bottom up:
- Basale
- Spinosum
- Granulosum
- Lucidum (thick skin)
- Corneum
Stratum basale
Deepest and most active (mitotically) layer that is attached to the basement membrane and separates the epidermis from the dermis. The cells are connected to each other by desmosomes (contains cadherin) and connected to the basement membrane by hemidesmosomes (contains integrin).
Stratum spinosum
Spiny cell layer of the epidermis. It is an artifact of tissue shrinkage during preparation because the cytoplasm shrinks during dehydration of cell prep. Desmosomes hold onto the adjacent cell which gives rise to the spiny appearance.
Stratum granulosum
Layer that contains granules in the cytoplasm. The two types of granules are keratohyalin and lamellar cells.
Stratum lucidum
First dead cell layer of the epidermis that is clear and contains compressed, dead squames. It is present in thick skin, but not thin skin.
Stratum corneum
Outermost layer of the epidermis that contains dead keratinocytes. It acts as a barrier for desiccation and prevents infection from bacteria.
- It is thicker in thick skin, thinner in thin skin
Keratohyalin
Non-membrane bound granules within the stratum granulosum
Lamellar cells
Membrane bound granules within the granulosum. They secrete sheets of lipids (hydrophobic) between cells to act as a barrier to water and as an intracellular cement between the cells.
Dermatoglyphics
Finger prints. Unique to individuals except in identical twins (nature vs. nurture gives slight variations).
Functions of the epidermis
Abrasion resistance, physical-chemical barrier, and water proofing
Tyrosinase
Enzyme that causes melanosomes to convert DOPA into dopaquinone and then into melanin within mature melanocytes
Eumelanin
Most common type of melanin. They are black/brown, ellipsoid shaped granules.
Pheomelanin
They are red/yellow, round shaped melanin granules
3 types of skin cancer
Basal cell carcinoma (basale), squamous (keratinocyte) cell carcinoma, and melanoma
Layers of the dermis
From bottom up
- Reticular layer
- Papillary layer
Papillary layer
Peg and socket layer that locks the dermis into the epidermis to prevent shear force from causing injury. It contains capillaries and Meissner’s corpuscles.
- Smaller than the reticular layer
Reticular layer
Layer of the dermis that is mostly connective tissue, blood vessels, collagen fibers, fibroblast, elastic fibers. It contains arteriovenous shunts.
Meissner’s corpuscles
Gives the papillary layer light touch sensory responses
Arterio-venus shunts
Allow blood to flow into the papillary layer to regulate thermoregulation (facilitate evaporative cooling)
Pacinian corpuscles
Gives the reticular layer deep touch/pressure responses
- They have a cross sectioned onion appearance
Hair
Originates in the epidermis and contains the shaft which grows above the epidermis and the root that is beneath the skin. The root consist mostly of the follicle and the bulb.
Hair bulb
Structure at the bottom of hair that consists of a dermal papilla and cells of the germinal matrix that are rapidly proliferating.
Hair papilla
Structure in hair bulb that gives nutrients to keratinocytes
Hair follicle
Contains cuticles that anchor hair into integument and an external and internal root sheath.
Arrector pili
Smooth muscle connected to hair that controls movement. It can act as partial insulation in the cold when it stands up and is activated during fight or flight.
Sebaceous gland
Simple branched acinar gland that occurs above the internal root sheath.
- Contains lipid droplets
- Holocrine mode of secretion
- Contain sebum
Eccrine swear gland
Glands that open onto all surfaces of body. They contain a secretory portion and excretory portion.
- The have a merocrine mode of secretion
- The secretory portion portion contains dark and clear cells.
- The excretory portion contains ducts that transports fluid and contain stratified cuboidal cells.
Apocrine sweat gland
Glands that are limited to the arm pits and growing areas of body. They secrete by a merocrine mode of secretion.
- Apocrine glands contain dark cells
- Open onto hair shaft
- Larger lumenal diameter than eccrine glands
Sebum
Located within sebaceous cells of the hair that maintain the corneum
Dark cells
Produce mucous, pheromonal function
Clear cells
Produce sweat
Melanin granule movement into keratinocytes
Mature granules are transported to the tips of fingerlike projections of the melanocyte and are injected into adjacent keratinocytes. This leads to the accumulation of melanin at a location within the cytoplasm of keratinocytes between the nucleus and sunlight in order to protect the DNA from UV radiation/damage.