Connective Tissue (CT)

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Connective Tissue(CT)
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Diversity of Connective Tissue

• Types and Functions
• Loose Connective Tissue Areolar and fat
• insulation, protection (padding), loosely
  connecting structures
• Dense Connective Tissue Ligaments and tendons
• binding and support
• Cartilage
• protection, support
• Bone
• support
• Blood
• transportation

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Common Characteristics of all CT
3. Composed of different types of cells within
the tissue.
1. Embryonic origin (mesenchyme)
5. All support epithelium
4. Variation in amount of blood supply
(vascularization)
2. Has an extracellular matrix of fibers and
ground substance.
Ground substance
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Loose Connective Tissue

• Ex. 1 Areolar most widely distributed type.
• Gelatinous
• Loosely packed lots of liquid held in ground
  substance
• packing material cushioning organs,
  subcutaneous, attaches skin to muscle.
• Has all three fibers
• Cells fibroblasts, macrophages, mast cells, and
  white blood cells
• Swells during inflammation (edema)

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Areolar (Prototype)
collagen
Ground substance
Mast cell
Elastin
Fibroblast
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Loose Connective Tissue

• Ex. 2 Adipose Fat!
• Loosely packed with sparse matrix
• 90 of tissue is mature adipocyte cell
• Most of each cell is a fat droplet, so nuclei is
  displaced to the side
• Richly vascularized
• Nutrient storage, cushioning in areas like abs,
  hips, around kidneys
• High concentrations subcutaneous (under skin)
  shock absorber, insulation
• Fat deposits act as local nutrient sources around
  active organs (heart, muscles)

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Adipose
Adipose
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Loose Connective Tissue

• Ex. 3 Reticular
• Only contains reticular fibers.
• VERY DELICATE a fine net of fibers that act as
  a soft skeleton
• Supports lympho nodes, bone marrow, spleen, free
  blood cells.

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Dense Connective Tissue

• Ex. 1 Dense Regular Tendons and Ligaments
• Fibers predominate.
• Abundant and crowded fibroblasts make fibers
• Little ground substance
• Regular, parallel bundles of collagen fibers
• Resist tension pull and stretching.
• Ligaments connect bone to bone
• Tendons connect muscle to bone.
• Poorly vascularized

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Dense Connective Tissue

• Ex. 2 Dense Irregular
• Thicker, irregularly arranged collagen.
• Found where tension is applied in different
  directions
• Example Dermis of skin, organs, joints

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Dense Regular
Dense Irregular
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Cartilage

• Characteristics
• Resists tension AND compression
• Lots of collagen (strong) AND elastic fibers
  (flexible)
• No nerves or blood vessels
• High content of proteoglycans ?80 water
• Chondroblasts make matrix until end of human
  adolescence
• Mature Chondrocytes found in cavities called
  lacunae (pit)

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Hyaline Cartilage

• Looks glassy (hyalin glass)
• Few chondrocytes, all found in lacunae
• Mostly matrix lots of collagen
• Reduces friction, absorbs pressure
• Covers ends of long bones, connects ribs to
  sternum, forms rings in trachea and bronchi

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Elastic Cartilage

• Looks almost identical to hyaline BUT more
  elastic fibers ? more flexible!
• Matrix appears more fibrous
• More lacunae, closely spaced.
• Found in ear and epiglottis

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Hyaline Cartilage
Elastic Cartilage
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Fibrocartilage

• Intermediate between dense regular CT and hyaline
• Consists of rows of chondrocytes and collagen
  fibers
• Compressible AND resists tension
• Found in intervertebral discs.

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Bone (Osseous Tissue)

• Most supportive tissue in body.
• Matrix is similar to cartilage, but with morer
  collagen (strong) surrounded by calcium salts
• Osteoblasts make collagen fibers and calcium
  salts deposited between fibers.
• Well vascularized
• Osteocytes stored in lacunae
• Bone marrow stores fat and makes blood cells.

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Blood

• Atypical connective tissue
• Only classified as such because it arises from
  same embryonic tissue
• Blood cells are within a matrix of blood plasma.
• Fibers apparent only when blood clots.

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How do damaged tissues repair?

• Injured cells release hormones and proteins to
  signal need for healthy cells to divide and
  migrate.

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Steps to Tissue Repair

• Inflammation
• Inflammatory chemicals released by injured cells,
  macrophages, mast cells
• Vessels dilate, allowing clotting and plasma
  proteins and wbc to invade injured site.
• Clotting proteins begin clotting.

• 2) Restore Blood Supply
• Granulation tissue replaces clot, digested by
  macrophages
• New capillaries form.
• Fibroblast in granulation tissue make collagen
  and growth factors.

• 3) Regeneration or Fibrosis below scab
• Regeneration replacement w/ same tissue type
• Fibrosis replacement w/ fibrous connective
  tissue (scar)

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Regeneration Capacity

• Fibrosis replaces tissue in non-regenerative
  tissues
• Mostly collagen
• STRONG but lacks flexibility/elasticity
• Cannot perform function of tissue that was
  replaced

• Varies by tissues
• High capacity No capacity

• Cardiac Muscle
• Nervous Tissue

• Epithelial
• Bone
• Areolar CT
• Dense I. CT
• Blood forming tissue

• Dense R. CT

• Cartilage

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Extracellular Matrix

• Embeds cells of connective tissue
• Medium for nutrients and other dissolved
  substances that nourish cells
• Made up of ground substance and fibers.
• Ground substance
• Texture varies
• Can be liquid, gel-like, semi-solid or hard.
• depends on amount of cell adhesion proteins that
  trap water called proteoglycans
• More proteins, more solid ground substance.
• Fibers provide strength and/or flexibility
• Allows for weight bearing, withstanding of
  mechanical abuse, tension protects!!

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Dense connective tissue, lots of fibers, little
open space.
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Loose connective tissue Lots of ground substance
fewer fibers
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Fibers

• Embedded in ground substance
• Adds strength/flexibility.
• Created by undifferentiated blast cells of
  extracellular matrix
• 3 Kinds
• Collagen Strong
• Elastic Flexible
• Reticular Delicate

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Collagen (white fibers)

• Rope-like bundles
• Tough, stronger then steel!
• Tension resistant

Return to fibers
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Elastic (yellow fibers)

• Long, thin
• Branching networks
• Stretch and recoil ability for elasticity
• Highly concentrated in areas like skin, lungs,
  vessels where elasticity is needed

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Reticular network fibers

• Short, fine, delicate
• Collagenous, but with more give due to branching
  network
• Support soft tissue organs, blood vessels
• abundant in boundaries where connective tissue
  lines other tissues (ex. basement membrane)

Blood vessel
Collagen
Reticular fibers
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Cells in Matrix

• Cells of CT make and maintain the ground
  substance and fibers of extracellular matrix
  (ECM).
• Each type of CT have immature and mature forms of
  these cells.
• Immature cells have suffix -blast are
  actively mitotic and produce ECM.
• Fibroblasts make loose and dense CT proper
• Chondroblasts make cartilage
• Osteoblasts make bone
• Hematopoeitic stem cells make blood
• Mature cells have suffix -cyte maintain
  health of matrix
• Ex. Fibrocyte
• Mature cyte cells can reverting to blasts to
  regenerate matrix after injury.

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What other cells are in CT?

• Accessory Cells
• White blood cells (macrophages, plasma cells)
  responsible for immune response
• Mast cells responsible for inflammation
  following injury or infection.
• Fat cells store nutrients

Back to common characteristics of CT