Body Membranes and Tissue Repair

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Body Membranes and Tissue Repair

• Ch. 4

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Body Membranes

• Body membranes cover surfaces, line body
  cavities, and form protecting (often lubricating)
  sheets around organs
• TWO major groups
• Epithelial and Connective Membranes

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Epithelial Membranes

• EPITHELIAL membranes include the CUTANEOUS,
  MUCOUS, and SEROUS membranes
• All contain epithelial sheet always combined with
  underlying connective tissue
• These membranes are actually simple organs

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Epithelial Membranes
Skin (Integument)
Wet Exterior Openings
Interior Linings
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Cutaneous Membranes

• Cutaneous membrane is the SKIN
• Its superficial EPIDERMIS is composed of
  keratinizing stratified squamous epithelium
• Underlying DERMIS is mostly dense (irregular)
  connective tissue
• Unlike other epithelial membranes, CUTANEOUS
  membrane is exposed to air and is a DRY MEMBRANE

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Mucous Membranes

• Mucous membrane (mucosa) composed of epithelium
  resting on loose connective tissue membrane
  called LAMINA PROPRIA
• Lines ALL body cavities open to the exterior
• Hollow organs of respiratory, digestive, urinary,
  and reproductive tracts
• Stratified squamous (mouth and esophagus) or
  Simple columnar (rest of digestive tract)

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Mucous Membranes

• WET or moist membranes continually bathed in
  secretions
• Urinary mucosa bathed with urine
• Mucosa epithelium adapted for ABSORPTION/SECRETION
  
• Mucosa of respiratory/digestive tracts secrete
  large amounts of protective, lubricating mucus
• Urinary tract DOES NOT secrete mucus

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Serous Membranes

• Composed of layer of simple squamous resting on
  thin layer of areolar connective tissue
• Line ALL body cavities closed to exterior (except
  for dorsal body cavity and joint cavities)
• SEROUS membranes occur in PAIRS
• PARIETAL LAYER lines specific portion of wall
  of ventral body cavity then folds back on itself
  to form VISCERAL LAYER which covers outside of
  organs in cavity

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Serous membranes

• In body, serous membranes separated by thin,
  clear fluid called SEROUS FLUID that is secreted
  by both membranes
• Allows organs to slide easily across cavity walls
  and one another without friction
• Extremely important when mobile organs such as
  pumping heart and churning stomach are involved

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Whats in a name?

• Specific names of serous membranes depend on
  their locations
• PERITONEUM is serous lining abdominal cavities
  and covering its organs
• PLEURA is serosa lining the lungs
• PERICARDIUM is serosa lining around the heart

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Connective Membranes

• CONNECTIVE tissue membranes represented by
  SYNOVIAL membranes

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Connective Membranes

• Composed of connective tissue and contain NO
  epithelial cells
• Line fibrous capsules surround joints
• Provide smooth surface and secrete lubricating
  fluid called SYNOVIAL FLUID
• Also line small sacs of CT called BURSAE and
  tube-like TENDON SHEATHS
• Both of these cushion organs moving against each
  other during muscle activity (movement of tendon
  across a bones surface)

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Tissue Trauma

• Causes inflammation (non-specific) response,
  characterized by
• Redness
• Heat
• Swelling
• Pain
• Disturbance of function
• Also, causes an immune (specific) response

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Immune Response Mediators of Inflammation

• Histamine, kinins, prostaglandins, and
  leukotrienes are released
• These can cause blood vessels to dilate (which
  causes the redness and heat), but it also brings
  blood cells needed to fight infection and repair
  the injury
• These also increase permeability of blood vessels
  allowing materials to move in and out of the
  tissue can lead to edema and pain
• WBCs like neutrophils arrive to eat bacteria and
  ingest tissue debris leads to pus

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Tissue repair Two phases

• Regeneration new cells are the same type as
  those destroyed normal function is restored
• Replacement loss of normal function as a new
  type of tissue forms dense connective tissue
  usually makes scar tissue (collagen fibers)
• Types of dividing cells
• Labile cells continue to divide throughout life
  (i.e. skin and mucous membranes)
• Stable cells do not actively divide after
  growth stops but divide after an injury (i.e.
  connective tissues like bone, tendons and
  ligaments, and glands)
• Permanent cells little or no ability to divide
  (i.e. cardiac muscle and damaged neurons are
  replaced only with scar tissue)

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Tissue Repair Steps

• Remember Blood Can Get Everywhere
• Bleeding Damage to the epithelium (epidermis)
  and connective tissue (dermis) capillaries leak
  fluid (w/ clotting proteins) into injured area

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Tissue Repair Steps

• Clotting Clotting proteins make a clot to stop
  loss of blood, hold wound together, and wall
  off injured area clot becomes a scab (1 week
  post-injury)

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Tissue Repair Steps

• Granulation Tissue (w/ capillaries) grows into
  damaged area phagocytes eat blood clot and dead
  tissue collagen fibers (scar tissue) bridge the
  gap in damaged area (2 weeks post-injury)

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Tissue Repair Steps

• Epithelium Regenerates across granulation
  tissue beneath scab wound is closed granulation
  tissue is replaced with new connective tissue (1
  month post-injury)

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Tissues and Aging

• Cells divide more slowly as people age, and
  injuries heal more slowly.
• Connective tissues change
• Collagen fibers become irregular in structure,
  even though they may increase in number
• Elastic fibers become less elastic
• Therefore, the skin wrinkles, bones break more
  easily, tendons and ligaments become less
  flexible, blood vessels can be blocked and
  rupture easily.