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
Hair
Columns of keratinocytes growing from follicles deep in dermis or hypodermis
Regions of a hair from deep to surface:
Hair bulb
Hair root
Hair shaft
Hair
THREE CONCENTRIC LAYERS KERATINIZED CELLS
MATRIX/MEDULLA – central core
CORTEX – surrounds medulla
CUTICLE – outermost layer
FUNCTIONS OF HAIR: Protection Heat retention Facial expression Sensory reception Visual identification Chemical signal dispersal
3 KINDS OF HAIR:
During our lives, we produce three kinds of hair:
LANUGO (lan.ugo)=baby hair
VELLUS(vel.lus)=normal body hair
TERMINAL HAIR= thicker, pubic hair, eyebrows, eyelashes, armpits, etc.
HAIR STRUCTURE:
From deep to superficial
HAIR PAPILLA: connective tissue, nerves, and blood vessels below follicle that support the keratinocytes
-HAIR BULB: a swelling at bottom of follicle filled with dividing keratinocytes; increase in hair matrix causes hair growth
ARRECTOR PILI: involuntary smooth muscle attached to hair shaft; responds to emotional states (fear or rage) and cold temperatures by contracting, standing hair up, and producing “goose bumps”
HAIR COLOR:
Result of the synthesis of melanin in the matrix adjacent to the papillae.
Variations in hair color reflect genetically determined differences in the structure of the melanin.
Environmental and hormonal factors
Age
Gray hair. What causes it?
Skin Exocrine Glands
Two most common types:
SWEAT GLANDS: PRODUCE watery solution
-MEROCRINE
Distributed throughout body, except external genitalia, nipples, and lips; especially prevalent on palms, soles, and forehead
Produce nonviscous, watery secretion; controlled by nervous system; provide some antibacterial protection; function in thermoregulation and excretion; flush surface of epidermis
- APOCRINE
- Distributed in axillary, anal, areolar, and pubic regions
-Produces viscous, complex secretion; secretion influenced by hormones; may act in signaling/communication
SEBACEOUS GLANDS: produce OILY secretions
Secrete oily SEBUM INTO hair follicles
lubricates hair and skin
relatively inactive during childhood; sex hormones at puberty cause secretions to increase significantly
Two rarer types:
CERUMINOUS GLANDS: produce ear wax
MAMMARY GLANDS: produce milk
