Integumentary System Flashcards
Structure and Function of the Integument Epidermis Dermis Hypodermis Accessory Organs
The Integument
INTEGUMENT = Skin
-largest organ (7% to 8% of body weight)
-TWO LAYERS
EPIDERMIS: superficial layer of stratified squamous epithelium
DERMIS: deeper layer of AREOLAR AND DENSE IRREGULAR CONNECTIVE TISSUES
-HYPODERMIS (not part of the skin) lies under dermis, mostly ADIPOSE CONNECTIVE TISSUE
- Skin is also known as the CUTANEOUS MEMBRANE.
- Integumentary System consists of the skin and its derivatives—nails, hair, sweat glands, and sebaceous glands.
The Integument
Is the body’s largest organ.
-Its surface is covered by an EPITHELIUM THAT protects underlying body layers.
- The CONNECTIVE TISSUES contain blood vessels that provide nutrients and PROVIDE STRENGTH AND RESILIENCE TO THE SKIN.
- SMOOTH MUSCLE controls BOTH BLOOD VESSEL DIAMETER AND HAIR POSITION.
- NEURAL TISSUE supports and monitors SENSORY RECEPTORS IN the skin
Integument Functions
- Protection
- Prevention of H2O loss
- Temperature regulation
- Metabolic regulation
- Immune defense
- Sensory reception(markle cells)
- Excretion/Secretion
The Epidermis
- Most superficial layer
- Avascular(no blood vessels)
- KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM
- KERATIN : a water-insoluble protein
- 4 to 5 layers (strata) of distinct cell types
Epidermal cells occupy the STRATUM BASALE
KERATINOCYTES:
- produce keratin which provides its protective properties
- most abundant cell type in epidermis
- Arise from deepest layer of epidermis(stratum Basale)
- PRODUCE KERATIN – A TOUGH FIBROUS PROTEIN
- Undergo almost CONTINUOUS MITOSIS
- Produce antibodies and enzymes
- Keratinocytes are dead at skin’s surface
MELANOCYTES:
–specialized cells that creates the pigment MELANIN, found in deepest layer(stratum basale)
- The darker tones of the skin result from melanin being produced by the melanocytes and from the darkening of melanin already present upon exposure to ultraviolet light.
TACTILE (MERKEL) CELLS :
– located at epidermal-dermal junction, associated with disc like sensory nerve endings
-TACTILE CELLS are sensitive to touch, and when compressed, they release chemicals that stimulate sensory nerve endings, providing information about objects touching the skin
EPIDERMAL DENDRITIC (LANGERHANS) CELLS: -macrophages that help activate our immune system, arise from bone marrow and migrate to epidermis
Epidermal Strata
From deep to superficial (as they grow):
5) STRATUM BASALE(bottom most layer)
4) STRATUM SPINOSUM
3) STRATUM GRANULOSUM
2) STRATUM LUCIDUM (FOUND ONLY IN THICK SKIN)
1) STRATUM CORNEUM
(superficial (1) to deeper layer (5) )
Stratum Basale
The deepest epidermal layer is the STRATUM BASALE
- layer of cells ranges from CUBOIDAL TO LOW COLUMNAR in appearance.
- ONLY LAYER THAT UNDERGOES MITOSIS
- One layer of cells adjacent to the dermis
- KERATINOCYTES: most abundant; produce Keratin To Waterproof The Skin
- MELANOCYTES: cells with long, branched cytoplasmic processes; produce a pigment (black, brown, or yellow) that absorbs UV light to prevent DNA damage, reducing some forms of skin cancer
TACTILE CELLS: sense touch
Stratum Spinosum
spiny layer
- Several Layers Thick
- Each time a keratinocyte stem cell in the stratum basale divides, the daughter cell that will differentiate into the new epidermal cell is pushed toward the external surface from the stratum basale
- Once this new cell enters the stratum spinosum, the cell begins to differentiate into a nondividing, highly specialized keratinocyte
- Epidermal dendritic cells
- phagocytes that engulf invading pathogen
Stratum Granulosum
(granular layer) where Keratinization occurs
- Consists Of THREE TO FIVE layers of flattened keratinocytes superficial to the Stratum Spinosum
- Keratinization occurs at this level
- Cells flatten
- cytoplasm fills with keratin filaments
- organelles begin to degrade
- fully keratinized cells are dead but strong and water-insoluble
Stratum Lucidum(ONLY FOUND IN THICK SKIN) (clear layer)
- THIN, translucent region about TWO TO THREE CELL layers thick
- Superficial to the STRATUM GRANULOSUM
- Present ONLY IN THICK SKIN such as SOLE OF FEET AND PALMS OF HANDS
- Cells lack organelles, filled with ELEIDIN (ele.i.den)
- transparent, intermediate product of keratin maturation
Stratum Corneum
hornlike layer
- THE most SUPERFICIAL LAYER of the epidermis
- The STRATUM CORNEUM consists of about 20 TO 30 LAYERS of dead, scaly, interlocking keratinized cells called CORNEOCYTES (corn.e.ocytes)
- The dead cells are ANUCLEATE (lacking a nucleus) and tightly packed together
- Comprised solely of dead keratinocytes
Thick vs. Thin Skin
THICK EPIDERMIS:(thick skin)
-Found on the PALMS OF HANDS, SOLES OF THE FEET AND corresponding surfaces of FINGERS AND TOES
- All 5 Epidermal Strata Occur In Thick Skin
- thick skin contains sweat glands, but no hair follicles or sebaceous glands
THIN EPIDERMIS:(thin skin)
-Covers most of the body
-LACKS THE STRATUM LUCIDUM(has only four layers)
-Contains the following accessories: HAIR FOLLICLES,
SEBACEOUS GLANDS,
SWEAT GLANDS.
Epidermal Variation: Skin Color
Skin Color is determined by 3 pigments:
-HEMOGLOBIN: Blood Pigment; causes light complexions to look pink (or blue)
MELANIN: pigment produced and stored in cells called melanocytes.
-the two types of melanin occur in various yellow, reddish, tan, brown, and black shades
CAROTENE: YELLOW-orange pigment from food
Epidermal Variation: Skin Markings
NEVUS: (ne.vus)
-localized overgrowth of melanocytes
A.K.A. MOLE
HEMANGIOMA:(he.man.gioma) proliferation of blood vessels
-may disappear (strawberry) in childhood or may persist (port-wine) through adulthood
FRICTION RIDGES:
folds of epidermis/dermis on fingers, palms, soles, and toes for grasping
cause us to leave fingerprints
The Dermis
- lies deep to the epidermis
- The dermis consists of two types of connective tissue: AREOLAR AND DENSE IRREGULAR
PAPILLARY: superficial
-AREOLAR Connective tissue
RETICULAR: deeper
-DENSE IRREGULAR Connective Tissue
- mainly collagen fibers
- contains blood vessels, glands, hair follicles, nail roots, sensory nerve endings, and smooth muscle
Papillary Layer of the Dermis
(top layer of the dermis)
(pa.piL.Lary)
- Directly below stratum basale cells of epidermis
- It is composed of AREOLAR CONNECTIVE TISSUE,
- DERMAL PAPILLAE AND EPIDERMAL RIDGES interlock, increasing the surface area between epidermis and dermis
- DERMAL PAPILLAE contain capillaries that supply nutrients to the avascular epidermal cells
The Reticular Layer
forms majority of the dermis
- forms the deeper, major portion of the dermis
- The RETICULAR LAYER CONSISTS primarily of DENSE IRREGULAR CONNECTIVE tissue through which large bundles of collagen fibers project in all directions.
- These fibers are interwoven into a meshwork that surrounds the structures in the dermis, such as hair follicles, sebaceous glands, sweat glands, nerves, and blood vessels
- collagen bundles help connect dermis to underlying hypodermis
Lines of Cleavage
- Lines in the deep dermis formed by the orientation of collagen bundles
- importance to surgeons: incisions across these lines heal more slowly than incisions along the lines
Innervation
Nerve fibers are present in dermis
Functions:
tactile (touch) receptors
control blood flow
control glandular secretion
Blood Supply
EPIDERMIS: Avascular(no blood supply)
DERMIS: vascularize (contains blood vessels)
-important in controlling body temperature
VASOCONSTRICTION (vaso.constriction): narrowing blood vessels PRESERVES CORE BODY HEAT
VASODILATION (vaso.dialation): widening blood vessels releases body heat, lowering body temperature
Hypodermis(Subcutaneous Layer)
- A.K.A. subcutaneous layer
- deep to, not really part of, the integument
-AREOLAR AND ADIPOSE CONNECTIVE TISSUES
FUNCTIONS:
- protects underlying structures
- stores energy
- thermal insulation
Epidermal Derivatives
Structures that grow from the epidermis:
Nails
Hairs
Glands
Nails
- DERIVED FROM THE STRATUM CORNEUM
- Cells densely packed together filled with parallel FIBERS OF HARD KERATIN
- The NAIL PLATE has a whitish free edge, A PINKISH NAIL BODY, and a NAIL ROOT
- The NAIL BODY COVERS A LAYER OF EPIDERMIS CALLED THE “NAIL BED”
- The nail bed appears pink because of the underlying capillaries
Nails
Protective structures on digits(fingers)
PARTS:
NAIL BODY: flat keratinized cells protecting digit
NAIL BED: live epidermal cells under nail body
nail root: region hidden by cuticle
NAIL MATRIX: thickened growing part of the nail bed
LUNULA(“little moon”): white semilunar proximal area of nail body caused by thickened underlying stratum
PARTS OF THE NAIL Free edge Body Root Nail folds Lunula-“little moon” Eponychium – cuticle
