2.0. Integumentary System Flashcards
Epidermis
- Superficial layer of epithelial tissue
- Avascular (nourished by diffusion from capillaries of the papillary layer of the dermis)
- Composed of epithelial cells arranged into layers or strata
- Separated from dermis by basement membrane
Dermis
- Deep layer connective tissue
- Structural strength
Subcutaneous Tissue
- Not part of skin
- Has adipose tissues
- Loose connective tissue that connects skin to underlying structures
Epidermal Cells Types
Keratinocytes
Melanocytes
Langerhans Cells
Merkel Cells
Keratinocytes
- Make up the majority of epidermal cells
- First layer of the epidermis contains the keratinocytes filled with proteins and has died
- Produce and fill themselves with keratin (a hard, waterproof protein) as they move toward the surface
Cornification
Stratum Corneum contains keratinocytes that have completely filled with keratin and died
Keratinization
Aas cells of the epidermis becomes filled with keratin and they move outward through the layers they fill with keratin
Melanocytes
- Produce skin pigments called MELANIN
- Cells stay in the stratum basale
- Keratinocytes take in melanin-filled vesicles called MELANOSOMES by endocytosis
- Melanocytes may not be evenly distributed across the skin, and denser patches of these cells account for freckles and moles
Langerhans Cells
Act as the outermost guard of the cutaneous system and likely to induce the first reaction against pathogens
Merkel Cells
Detect light, sense of touch, and superficial pressure.
Tactile Cells
- Receptors for fine touch
- Found in the stratum basale associated with nerve cells in the underlying dermis
Dendritic Cells
- Immune system cells found in the stratum spinosum and the stratum granulosum
- Alert the body’s immune system to the invasion of pathogens
Epidermal Stratum (deepest to superficial layer)
Stratum Basale (Germinativium) Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Cornelium
Stratum Basale (germinativium)
- Deepest portion of epidermis and single layer
- High mitotic activity and cells become keratinized
- Composed of continuously dividing cells
Stratum Spinosum
- Limited cell division
- Contain desmosomes, lamellar bodies, and additional keratin fibers
Lamellar Bodies
Lipid containing cells and provide the lamellar internal structure, contains enzymes, enzyme inhibitors, and antimicrobial peptides
Stratum Granulosum
Contains keratohyalin
Keratohyalin
Protein structure in the cytoplasmic granules of the keratinocytes of the epidermis
Stratum Lucidum
- Thin, clear zone
- Found only in palms and soles
LUCIDUM - clear
Stratum Corneum
- Most superficial and consists of cornified cells
- Thickest layer of the skin
- Contains the dead keratinized cells
Thick Skin
- Composed of 5 epithelial layers
- Found in areas subject to pressure or friction (palms of hands, fingertips, soles of feet, fingerprints and footprints
- Papillae of underlying dermis in parallel rows
Thin Skin
- Composed of 4 strata (no stratum lucidum since it can only be found in thick skin)
- More flexible than thick skin
- Covers rest of body
- Hair grows here
Callus
- Increase in the number of layers in the stratum corneum
- When this occurs over a bony prominence, a corn forms
Skin Color Factors
Pigments
Blood circulating through the skin
Thickness of stratum corneum
Melanin (Pigment)
- Provides for protection against UV light
- Group of chemicals derived from a tyrosine
- Colored brown to black, may be yellowish or reddish
Albinism (Pigment)
- Deficiency or absence of pigment
- Production determined by genetics, hormones, exposure to light
Carotene (Pigment)
- Yellow pigment from vegetables
- Accumulates in stratum corneum, in adipose cells of dermis, and in subcutaneous tissue
Cyanosis/Cyanotic (Blood Circulating Through Skin)
Blue color caused by decrease in blood oxygen content
Erythema (Blood Circulating Through Skin)
Red color caused by increased blood flow
Thickness of Stratum Corneum
- Impacts color
- Thicker areas can be yellowish
Dermis
- Gives structural strength
- Thicker than the epidermis
- Connective tissue with many fibers, fibroblasts, macrophages
- Contains some adipocytes, nerves, blood vessels, hair follicles, smooth muscles, glands, and lymphatic vessels
- “True skin”
Fibroblasts
Cells that produce collagen
Sensory Functions of Dermis
Pain Itch Tickle Temperature Touch Pressure Two-point Discrimination
Dermis Contains:
- Papillae
- Fibers
- Nerve endings
- Cutaneous glands
- Hair follicles
- Blood vessels
Two Layer of Dermis
PAPILLARY - Superficial
RETICULAR - Deep
Papillary / Superficial (Layers of Dermis)
DERMAL PAPILLAE
(1) Capillary beds
(2) Reason for fingerprints
- Most superficial layer
- Friction ridges form fingerprints
- Whorls of ridges, touch receptors (Meissner, Pacinian, and Ruffini), free nerve endings sensing pain
Meissner Corpuscles
Type of mechanoreceptor that is responsible for sensitivity and light touch
Pacinian Corpuscles / Vater-Pacini / Lamellar Corpuscles
Sensory receptors for vibration and deep pressure; essential for proprioception
Ruffini Corpuscles
- Record the low frequency vibration or pressure
- Adapt to pressure that results to the stretching of the skin
Reticular / Deep (Layers of Dermis)
- Dense irregular
- CONNECTIVE TISSUE: Collagen and elastic fibers
- Some adipose, hair follicles, nerves, oil glands, ducts of sweat glands, heat sensors for thermoregulation
Cleavage (Tension) Lines
- Elastic and collagen fibers oriented in some directions more than in others
- Important in surgery
Subcutaneous Tissue
- Deep to skin.
- “Hypodermis”
- Consists of loose connective tissue with collagen and elastic fibers
Types of Cells in Subcutaneous Tissue
FIBROBLASTS - Synthesizes the extracellular matrix and collagen
ADIPOSE CELLS - Provide energy source, insulation and for protection
MACROPHAGES
3 Concentric Layers of Hair
MEDULLA - Central axis; most medial portion of the hair
CORTEX - Forms bulk of hair; lateral to medalla
CUTICLE - Forms hair surface; outermost part of the hair
3 Types of Hair
LANUGO HAIR
(1) Very fine and unpigmented (colorless)
(2) Forms on a fetus during the last three months of its development
VELLUS HAIR
(1) Unpigmented and very fine, replaces lanugo hair around the time of birth
(2) Body hair on most women and children
TERMINAL HAIR
(1) Thick, coarse, and heavily pigmented
(2) Forms eyebrows, eyelashes, and hair on scalp
Hair Follicle
DERMAL ROOT SHEATH - Part of dermis that surrounds the epithelial root sheath
EPITHELIAL ROOT SHEATH WITH INTERNAL AND EXTERNAL PARTS - Internal epithelial root sheath contains stratum basale that may remain after injury and supply source of new epidermis
Hair Bulb
- Internal matrix is the source of hair
- Dermis projects into a bulb as HAIR PAPILLA, serving as blood supply
Hair Growth Cycle
ANAGEN
(1) Growth phase
(2) Hair growth
CATAGEN
(1) Transition phase
(2) Detaches from the nourishing blood
TELOGEN
(1) Resting phase
(2) Hair dies and falls out
Androgenetic Alopecia
Permanent hair loss / pattern baldness
Arrector Pili
- Type of smooth muscle
- Muscle contraction causes hair to “stand on end”
- Skin is pushed up by movement of the
hair follicle - Responsible for goosebumps (muscle contraction which causes the hair to stand)
Sebaceous Glands
- Holocrine (death of secretory cells)
- Oily secretion
- Prevents drying and may inhibit bacteria
- Most empty into the hair follicle
- EXCEPTIONS: lips, meibomian glands of eyelids, genitalia
Sweet (Sudoriferous) Glands’ Two Types
Eccrine (Merocrine) Gland
Apocrine Glands
Eccrine (Merocrine) Gland
- Most common
- Simple coiled tubular glands
- Open directly onto the surface of skin
- Have own pores
- Coiled part in dermis, duct exiting through epidermis
- Produce isotonic fluid (sweat) containing mostly water and some wastes
- Numerous in palms and soles
- In the lower reticular dermis
Apocrine Glands
- Active at puberty
- Compound coiled tubular
- Usually open into hair follicles superficial to opening of sebaceous gland
- SECRETION: organic compounds that are odorless but, when acted upon by bacteria, may become odiferous
- In axillae, genitalia (external labia, scrotum), around anus
Ceruminous Glands
- Modified merocrine sweat glands, external auditory meatus
- Prevent dirt and insects from entry
- Keep eardrum supple
- Earwax (Cerumen)
Mammary Glands
Modified apocrine sweat glands that produce milk
Regeneration
Normal function returns
Fibrosis
Normal functioning tissue is replaced by scar tissue (which leads to scarring)
Burns
PARTIAL-THICKNESS
(1) First-degree - Epidermis
(2) Second-degree - Epidermis & dermis
FULL THICKNESS
(3) Third-degree - Epidermis, dermis, & subcutaneous tissue
FOURTH-DEGREE
(1) Affects deeper structures
(2) Bones can be seen
SKIN GAFTS
(1) Split skin
(2) Artificial skin
(3) Cadavers/pigs
The Rule of Nines
- Used to estimate amount of body that is burned
- Proportions of adult and child differ
System
- Skin is more easily damaged because epidermis thins and amount of collagen decreases
- Wrinkling occurs due to decrease in elastic fibers
- Decrease in blood supply causes poor ability to regulate body temperature
- Functioning melanocytes decrease/increase; age spots
- Sunlight ages skin more rapidly
