Composite Tissues
• A composite tissue is muscle or nerve tissue
plus areolar tissue.
• Muscle Tissue
– Contractile tissue with elongated muscle fibers with
areolar C.T. Rich blood supply.
– Function: body movement and bracing
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Skeletal (striated or voluntary)
Cardiac
Smooth (involuntary)
Skeletal Muscle
Action is to pull on bones. Appears striated due to arrangements
of myofilaments. a.k.a. striated or voluntary muscle;
Cardiac Muscle
Smooth Muscle
Cannot be consciously stimulated to contract (involuntary muscle).
Found in GI tract, artery walls, bronchioles, uterus. Squeezes tubes.
Nervous Tissue
• Nervous Tissue
– Brain, spinal cord, peripheral nervous system
• Neuron (nerve cell)
– Transport nerve impulses along cytoplasmic extensions
to other neurons, muscles, glands, etc.
– No regeneration after development but some repair is
possible.
• Supporting cells (neuroglia)
– Nonconducting cells that nourish, support and bind, and
insulate nervous tissue.
Neurons
Integumentary
System
Functions
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Cushions and insulates deeper body organs
Protects from mechanical damage
Protects from chemicals, thermal damage and
microorganisms
Prevents water loss
Helps regulate body temperature via capillaries (blood
flow) and sweat glands (evaporation)
Excretory functions – urea, salts, water
Filters UV radiation
Synthesizes Vitamin D in light (w/ liver and kidneys)
Sensation – sense of touch, pressure, temperature, pain
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Largest organ and accounts for 7% of body
weight
1.5 to 4 mm thick
Made up of two layers
1. Superficial epidermis (thick epithelium)
2. Dermis (below epidermis, fibrous C.T.)
– Hypodermis, not part of the I.S. but a fatty
C.T. layer below dermis.
Epidermis
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Keritanized stratified squamous epithelium
Actively dividing tissue
Avascular
4 cell types:
– Keratinocytes (90%)
– Melanocytes (8%)
– Merkel cells
• Assoc. w/ nerve endings
– Langerhans cells
• Star-shaped macrophages
• Keratinocytes
– Most abundant epidermal cell
– Produces keratin (tough fibrous protein)
– Physical and mechanical protection
– Produce antibiotics and enzymes to help
combat infection
• Melanocytes
– Produce melanin (dark pigment)
– Shields cell nuclei from UV radiation
Thick Skin and Thin Skin
Thick Skin
• Hairless skin, palms and feet
• Keratinocytes produce the cells producing the layered
structure of skin
• There are 5 layers in thick skin.
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Stratum corneum, “horny or cornified layer”
Stratum lucidum, “clear layer”
Stratum granulosum, “granular layer”
Stratum spinosum, “spiny layer”
Stratum basale (stratum germanitivum), “basal layer”
• How long does it take to slough off cells?
– 35-45 days
• When is production accelerated?
– After damage
• What does persistent friction cause?
– callus
• What about short term severe friction?
– blister
Dermis
• Primarily irregular dense C.T.
• Binds the body like a stocking,
forming your “hide”
• Cells – fibroblasts, white cells,
mast cells, adipocytes,
macrophages
• Many blood vessels and nerves
• Thickness varies based on need
(e.g. soles and palms vs.
eyelid).
• Rupture(able) – obesity and
childbirth “stretch marks”.
Dermis
(2 layers)
• Papillary layer – areolar C.T.
– Top 20%
– Dermal papillae
• Finger like projections into the
epidermis
• Increases surface area
• Blisters?
• Reticular layer – dense ireg C.T.
– Lower 80%
– Tough due to inter-lacing collagen
fibers
– Reticular layer is patterned invisibly
in set patterns throughout body
– Fast healing?
– Palmar surface of fingers
dermal papillae
• Function:
– Fat storage
– Thickens w/
weight gain
– Anchores skin to
muscles
– Allows skin to
move over muscle
– Good insulator
since fat is a poor
conductor of heat.
• Hypodermis = subcutaneous layer = superficial fascia
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“below the skin”
Just deep to the dermis
Masses of areolar C.T. with adipose tissue usually predominating.
Skin Color
• 3 pigments contribute to skin color:
– Melanin
• Dominant pigment, ranges from yellow to reddish to brown to
black
• Moves into keratinocytes after synthesis by melanocytes.
• Precursor is tyrosine (a.a.), NO tyrosine = albinism
– Carotene
• Yellow to orange pigment derived from plants
• Accumulates in stratum corneum, especially obvious in soles
and hands of feet
– Hemoglobin
• Causes pink hue in lighter skin due to crimson color of
oxygenated blood in capillaries of dermis.
• Cyanosis
– Blue color due to poor oxygenation
– Indicator of poor circulation or respiratory
distress
– Nail beds and mucous membranes allows for
visualization in darker skinned individuals
• Hematoma
– Black and blue marks under the epidermis
where blood has escaped from circulation and
clotted.
Derivatives of the Epidermis
Shaft – above the skin surface
Root – embedded in the skin
Hair follicle – tubular invagination of the epidermis that gives rise to
the hair
Bulb – deep end of the follicle
Dermal papilla – provides nutrients to stratum basale in root bulb
Arrector pili muscle – contracts to erect hair (smooth muscle)
Glands
- Sebaceous glands-sebum
- oil glands derived from specialized epithelium cells
- fatty material that softens and lubricates follicle, also may
have anti-bacterial effects
- manufactured lotions (lanolin…sheep origin)
- acne = inflamed sebaceous gland triggered by hormone
increase in gland
Sweat glands (sudoriferous)
- produces sweat (0.5 – 12 L/day) to cool body
- 99% water w/some salts & wastes
- odorless?
- mammary glands
Nails - Modified epidermis which provides a protective cover for digits and assists in
dexterity. Made up of keratin.
- Free edge of nail = distal edge of nail
- Body = visible area of nail
- Nail root = proximal part embedded in the skin
- Nail bed = bed of epidermis below nail
- Lunula = white crescent formation at base of nail. Too thick for pink dermis to show
through.
- Eponychium (cuticle) = a proximal nail fold projecting onto nail body
Burns
• 1st Degree
– Only epidermis damaged
• 2nd Degree
– Injury to epidermis and upper
dermis, blistering
• 3rd Degree
– Damage to entire thickness of
the skin and underlying tissue
– Fluid loss and infection a high
risk
Rule of Nines:
Estimation of how much body
was affected by burn. 11
regions, each accounting for
9% of body area.
More terms to look up:
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Athlete’s foot
Cold sore
Decubitis ulcers
Dermatitis
Dermatology
Goose bumps
Keloid
Nevus
Skin cancer
– Basal cell
– Malignant melanoma