Integument Flashcards
1
Q
What are the functions of the integument?
What are the epidermal derivatives contained within the integument?
A
- barrier for protection, sensation, excretion, thermoregulation, and vitamin D3 synthesis
- contains hair, nails, sebaceous and sweat glands
2
Q
What are the layers of integument?
A
- epidermis: epithelial layer (ectoderm derived)
- dermis: layer of CT (paraxial mesoderm > dermatome derived)
- hypodermis (subcutaneous): loose CT layer, binds the skin to underlying tissue and corresponds to the superficial fascia
3
Q
What epithelium type is the epidermis?
What are the main types of cells within the epidermis?
A
- epidermis consists mainly of stratified squamous keratinized epithelium
- composed mostly of keratinocytes; less abundant are melanocytes, Langerhands cells, and Merkel cells
4
Q
- irregular projections at epidermal-dermal junction
- interdigitate w/ epidermal ridges to strengthen adhesion = increased anchoring of epidermis to dermis
A
dermal papillae
5
Q
What are the two types of skin?
A
- thick (400-1400 μM): palms and soles, fiver layers (w/ stratum lucidum), fingerprints
- thin (75-150 μM): widespread on body, four layers, glands and hair follicles
6
Q
What are the 4-5 layers of skin?
A
- stratum corneum (SC)
- stratum lucidum (not shown in image)
- stratum granulosum (SGr)
- stratum spinosum (SS)
- stratum basale (SB)
*know these in order, know distinguishing features, be able to identify them individually*
7
Q
- 15-20 layers of squamous, keratinized cells of the epidermis, filled w/ filamentous keratins
- cells are anucleate (more space for keratin) and coated by an extracellular layer of lipids (from granules of SGr)
- fully keratinized “cornified” cells, squames, are continuously shed as desmosomes break down
A
stratum corneum
8
Q
- layer of the epidermis found only in thick skin
- thin, translucent layer of flattened eosinophilic keratinocytes
- held together by desmosomes
- nuclei and organelles have been lost
- cytoplasm is almost exclusively keratin filaments
A
stratum lucidum
9
Q
- three to five layers of flattened cells of the epidermis
- filled w/ keratohyaline granules (granules = tonofibrils + filaggrin (bundling protein)): undergoing terminal differentiation of keratinization, stain intensely basophilic
- also include lamellar granules (small, ovoid structures containing lipids and glycolipids): undergo exocytosis and produce lipid-rich, impermeable layer that protects against water loss
- keratinization + lipid-rich layer = almost impenetrable skin barrier
A
stratum granulosum
10
Q
- typically the thickest layer of epidermis
- polyhedral cells w/ central nuclei and spiny processes
- keratin filaments assemble here into microscopically visible bundles called tonofibrils (a/w desmosomes > result in spiny appearance ‘prickle layer’)
A
stratum spinosum (remember ‘spiny’)
11
Q
- layer of the epidermis
- single-layer of keratinocytes w/ stem cells interspersed
- mitotically active, cuboidal/low columnar cells
- contains melanin and melanocytes
- bound apically by desmosomes
- bound basally by hemidesmosomes
A
stratum basale
12
Q
What does the mnemonic C’mon Let’s Get Sun Burn stand for?
A
(layers of the epidermis from apical to basal)
- Corneum
- Lucidum
- Granulosum
- Spinosum
- Basale
13
Q
- predominant cell type of the epidermis
- produce keratins, 85% of cells within the epidermis
- participate in the epidermal water barrier
- will produce “cornified” cells (full of keratin)
- stratum corneum is when keratinocytes are most mature
- outermost layer of skin, we lose these with abrasion
- undergo keratinization and desquamation (loss of cells)
A
keratinocytes
14
Q
- type of cell within the epidermis
- produce melanin and transfer it to keratinocytes
- melanin: pigment protein that protects nuclei from UV radiation
- neural crest-derived, scattered along stratum basale
- epidermal-melanin unit: one melanocyte maintains an association w/ a specific number of keratinocytes (1:10)
A
melanocytes
15
Q
Describe the process of melanin production:
A
- tyrosinase coverts tyrosine > DOPA (3,4-dihydroxyphenylalanine)
- DOPA is polymerized to melanin
- reactions occur in membrane-bound organelles, premelanosomes
- as melanin increases in premelanosomes, a melanosome is produced
- melanosomes are transferred to keratinocytes (pigment donation)
- creates a melanin umbrella that shields the nucleus
16
Q
Why is melanoma such a dangerous skin cancer?
A
- melanoma is derived from melanocytes, which are derived from neural crest cells
- the transition of melanocytes to cancer and uncontrolled growth, converts the cells to be able to access embryonic genes that are migratory (aka it can migrate anywhere in the body)
17
Q
- antigen presenting cells (APCs) that provide defense against pathogens (develop from monocyte precursor)
- identifiable in stratum spinosum
- pale cytoplasm w/ long processes
- antigen is phagocytized and displayed on the cell surface
- cell migrates to a nearby lymph node to activate lymphocytes
A
Langerhans cells
18
Q
How are epidermal cells differentiated and replaced?
A
- replacement is initiated by the division of stem cells in the stratum basale
- new cells undergo divisions in the stratum basale
- move upward as they differentiate into keratinized cells
- eventually are lost by exfoliation on skin surface
19
Q
- uneven boundary with finger-like dermal papillae that project into epidermis
- complemented by epidermal protrusions, epidermal ridges
- increased in size/number at sites of mechanical stress
- hemidesmosomes provide tight interface
- focal adhesions are also present
A
dermal-epidermal junction
20
Q
What are the 2 layers of the dermis?
A
- papillary layer: loose CT immediately beneath epidermis, vasculature and nerve endings present
- reticular layer: deep to papillary layer, dense irregular CT w/ coarse elastic fibers, form regular lines of tension (Langer’s lines) that are important for surgical purposes
21
Q
What are the 2 plexuses of the dermis?
A
- subpapillary plexus: rich, nutritive capillary network located between papillary and reticular layers
- deep plexus: lies near dermis-subcutaneous layer interface
22
Q
- loose CT that binds the skin loosely to the subjacent organs
- adipocytes vary in number and size based on body regions/nutritional state
- extensive vasculature promotes rapid uptake of insulin or drugs injected into this tissue
A
hypodermis (subcutaneous fascia)
23
Q
- epithelial tactile cells that function as low threshold mechanoreceptors essential for sensing gentle touch
- abundant in highly sensitive skin (fingertips, hair follicles)
- resemble surrounding keratinocytes but lack melanosomes
- contain small, golgi-derived granules concentrated near basolateral surface
A
Merkel cells
24
Q
- rare, aggressive and difficult to treat form of skin cancer
- 40x less common than malignant melanoma, but 2x mortality rate
A
Merkel cell carcinoma
25
- located in the papillary dermis and extending into lower epidermal layers
- respond primarily to high and low temperatures, pain, and itching
- may also function as tactile receptors
free nerve endings
26
- encapsulated receptors responsive to light touch or low frequency stimuli
- perpendicular to the epidermis (located in the tip) in the dermal papillae
- numerous in fingertips, palms, and soles
Meissner's capsule
27
- large, encapsulated, oval structures found deep in the reticular dermis and hypodermis
- specialized for sensing coarse touch, pressure (sustained touch), and vibration
- also found in CT of visceral organs (wall of rectum and urinary bladder) to produce pressure sensations when distorted
lamellated (pacinian) corpuscle
28
- type of gland
- secretion delivered via membrane bound vesicles and undergo exocytosis
merocrine gland
29
- type of gland
- secretion accumulates within cell, apoptosis secretion and cell debris released
holocrine gland
30
- type of gland
- release of apical portion of the cell, surrounded by cytoplasm within a plasma membrane
apocrine gland
31
- several glands per follicle
- abundant on face and scalp
- produce a lipid mixture, **sebum** via **holocrine secretion**
- waxy mix of trigs and cholesterol (lubricates and softens skin, waterproofs skin)
- sebum discharged into hair follicle
sebaceous glands
32
- simple, coiled glands found extensively throughout skin
- duct is stratified cuboidal
- **myoepithelial cells** facilitate expulsion of secretions via **merocrine glands**
- temperature regulation via cooling (evaporation of H2O from sweat on body surface)
- sweat components: H20, salt, ammonia, uric acid, and mucinogen granules
eccrine sweat glands
33
- large lumen, tubular glands
- duct is stratified cuboidal
- **myoepithelial cells** facilitate expulsion of secretions via **merocrine secretion**
- protein, carbohydrates, and ammonia rich secretion
- odorless until mixed w/ bacteria
- become functional at puberty and is what makes pubescent kids smelly
apocrine sweat glands
34
What is the structure of hair follicles?
- hair follicle has a terminal dilation called a **hair bulb**
- dermal papilla inserts into hair bulb, provides nutrients via capillaries
- keratinocytes form the **hair matrix**: continuous w/ epidermis, divide and differentiate which creates hair growth
- **follicular bridge**: contains epidermal stem cells, near insertion of arrector pilli M.
- arrector pilli M.: small bundle of smooth muscle that extends from midpoint of hair root to papillary layer (dermis); goose bumps = contracting muscle distorts attached dermis
35
What is the structure of nails?
- highly keratinized cells on a bed of epidermis (nail bed)
- **nail root**: most proximal region, covers the nail matrix
- **nail matrix**: stem cells divide and form keratinocytes (nail plate remains attached to nail bed, pushed forward by continuous growth)
- **lunula**: crescent-shaped white area near nail matrix
- **cuticle** (eponychium): extension of skin covering nail root
36
What is the concern of black or dark purple striping/coloring of the nail w/o associated injury/damage?
melanoma of nail
