Lab Exercise 7

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Lab Exercise 7

• The Integumentary System

Portland Community College BI 231
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Skin

• Or Cutaneous membrane is an organ.
• (an organ is a structure that contains two or
  more of the primary tissue types)
• Embedded within the skin are various accessory
  structures the combination of both is called the
  integumentary system

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Skin

• Epidermis Superficial layer
• Made of stratified squamous keratinized
  epithelium
• 4-5 Layers
• Dermis Underlying connective tissue layer
• 2 Layers
• Hypodermis Not part of the skin, it is deep to
  the dermis
• Primarily adipose tissue

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Layers of the epidermis

• Stratum basale single row of cells
• Adjacent to the dermis and attached by the
  basement membrane.
• Constantly dividing and pushing up layers
• Melanocytes with melanin protects the skin from
  UV radiation

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Layers of the Epidermis

• Stratum spinosum several cell layers superficial
  to stratum basale.
• Cells also dividing
• Cells contain bundles of intermediate filaments
  made of pre-keratin
• Cells appear star-shaped because the cell
  membrane pulls away from the other cells, except
  in areas where desmosomes are.

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Layers of the Epidermis

• Stratum granulosum
• The upper part of this layer has cells that are
  beginning to die
• Lamellated granules contain a waterproofing
  glycolipid that is secreted into the
  extracellular space
• Keratohyaline granules combine with intermediate
  filaments to form keratin fibrils

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Layers of the Epidermis

• Stratum lucidum Thin translucent layer of dead
  keratinocytes
• Found only in thick skin

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Layers of the Epidermis

• Stratum corneum Outermost layer
• 20-30 cell layers thick
• Cells are dead and flattened
• Full of keratin
• Constantly being rubbed off

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Epidermis cell phases

• Deepest layer (basale) goes through rapid
  division.
• Middle layers undergo a process of producing
  precursor molecules that lead to waterproofing of
  the cells.
• The final phase is the completion of the
  waterproofing process. Cells eventually die,
  providing a tough barrier

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Dermis

• The dermis is the connective tissue layer under
  the epidermis.
• Composed of primarily of fibers
• Irregularly arranged collagen fibers make up the
  majority and provide strength and flexibility to
  skin
• Lesser numbers of elastic fibers which provided
  elasticity to the skin
• There are also reticular fibers found in the
  dermis
• blood vessels, nerves, sensory receptors, hair
  follicles and glands.

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Dermis

• Papillary Layer Superficial dermal region
• Areolar connective tissue
• Contains capillaries, lymphatics and sensory
  neurons
• Dermal Papillae the fingerlike projections from
  the superior surface
• Epidermal ridge The epidermal layer that dips
  down into the dermal papillae
• Create fingerprints

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Epidermis
Epidermal ridge
PapillaryLayer
Dermal Papillae
ReticularLayer
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Finger Prints
Epidermal Ridge
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Dermis

• Reticular Layer Deepest skin layer
• Dense irregular connective tissue
• Contains the arteries, veins, sweat and sebaceous
  glands
• Cleavage lines the deep creases (like in the
  palm) where collagen and elastic fibers are
  arranged in parallel bundles.

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Hypodermis
Dermis

• Subcutaneous layer that is not part of the skin
• Beneath the dermis layer
• Composed of adipose and areolar connective tissue
• Highly vascular

Hypodermis
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Cells of the Epidermis

• Keratinocytes The main cells of the epidermis
• Produce keratin, water proof protein
• As new cells form, they push the older cells
  toward the surface, where they gradually
  accumulate keratin and eventually die
• Melanocytes Spidery black cells
• In stratum basale
• Produce melanin, the pigment that protects skin
  from UV damage

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Cells of the Epidermis
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Meissners (Tactile) Corpuscle

• Located in the dermal papillae
• Receptor for light touch

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Merkel Cells

• Merkel Cells At the junction of the sensory
  nerve endings
• In upper dermis and ll
• lower epidermis
• Light touch (like fly
• walking over cheek)

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Pacinian (Lamellated) Corpuscle

• Lie deep in the dermis
• Respond only when deep pressure is first applied
• Monitor high frequency vibrations

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Other skin receptors

• Warm and cool receptors When you are at
  comportable temperature both of these are firing
• If you increase or decrease the skin temperature
  beyond the range of these receptors, pain
  receptors are stimulated.
• Pain receptors are naked nerve endings in the
  dermis that respond to numerous environmental
  stimuli.

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Integumentary Glands

• Sudoriferous (sweat) glands
• Lactiferous (milk) glands
• Sebaceous (oil) glands
• Ceruminous (earwax) glands

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Eccrine (Merocrine) Sweat Glands

• Eccrine sweat glands
• Ducts open directly on the surface of the
  epidermis
• Produce normal body perspiration.
• Reduces body temperature by evaporative cooling

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Apocrine Sweat Glands

• Apocrine glands secrete a water and a higher
  concentration of organic acids than eccrine
  glands that bacteria can use for nutrients
  (creates body odor)
• Found in the armpits, around nipples and in the
  pubic region
• Secrete products into hair follicles or directly
  onto the surface.
• Begin functioning at puberty

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Apocrine Sweat Glands

• Red arrow - Apocrine Sweat Glands
• Green arrow - Hair follicle

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Sebaceous Glands

• Sebaceous glands
• Produce oily substance called sebum
• Helps waterproof the skin
• Acne infection of the sebaceous gland

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Hair

• Keratinized cells produced in
• Hair follicles tubular compartments that contain
  hair(projections of the epidermis into dermis)

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Hair

• Bulb deepest portion of the hair follicle
• Bulb contains the hair matrix which contains
  actively dividing cells
• The actively dividing cells give rise to the hair
  root.

As hair root approaches the surface of the skin
it becomes the hair shaft. Hard Keratin covers
the hair
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Hair Histology
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Arrector Pili Muscle

• Arrector pili muscle Smooth muscle that pull
  hair upright during fright or cold (goose bumps)

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Hair

• Determinate hair grows to a specific length and
  then stops
• Found in axilla, groin, eyelashes and eyebrows.
• Indeterminate hair grows without regard to
  length.
• Found on scalp and beards

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Hair

• Medulla central portion of the hair which is
  enclosed by an outer cortex.
• The cortex may contain pigments which give the
  hair its color (melanin)
• The cuticle is superficial to the cortex

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Fingernails

• Scale like modification of the epidermis
• Free edge part that grows away from the finger
• Body The nail
• Root Embedded in skin and sticks to the nail bed
• Nail Bed Extension of the stratum basale beneath
  the nail
• Nail Matrix Proximal part of the nail bed
  responsible for nail growth
• Lunula white crescent area Most active growth
  region of nail matrix

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Fingernail Structures
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Muscle Tissue

• Like epithelial tissue, muscular tissue is a
  cellular tissue with the tissue having mostly
  cells and little matrix
• There are three types of muscle skeletal,
  cardiac and smooth

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Skeletal Muscle

• Cells called fibers
• Striated
• Voluntary
• Multinucleate

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Sarcomere
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Cardiac Muscle

• Striated but striations are much less obvious.
• Cardiac muscle cells are called myocytes.
• Branched
• Involuntary
• Intercalated discs, which facilitate the
  transmission of the electrical impulses in the
  heart

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Smooth Muscle

• Nonstriated
• Involuntary
• Cells of smooth muscle are spindle-shaped
• Found in intestine where it propels food along by
  a process known as peristalsis and segmentation

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The End
The End