Connective tissue
• Found everywhere in the body
• Consist of living cells surrounded by a matrix
• Differences = cell type & fiber type & the
amount of the two
• Main classes –
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Connective tissue proper – fat and fibrous tissue
Cartilage
Bone
Blood
• Major functions –
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Binding & support
Protection
Insulation
Transportation
Connective tissue cont.
• Common characteristics –
– Common origin –
• All connective tissues arises from embryonic tissue
called mesenchyme
– Degrees of vascularity –
• Connective tissue ranges from avascular to highly
vascularized
• Cartilage – avascular
• Dense connective tissue – poor vascularization
• All other connective tissue – rich blood supply
– Extracellular matrix –
• Connective tissue is composed mainly of nonliving
extracellular matrix
• Separates the cells of the tissue
• Allows connective tissue to –
– Bear weight
– Withstand tension
– Endure physical trauma
Connective tissue cont.
• Ground substance –
– Unrestricted material that fills the space between
the cells and contains fibers
– Mechanism through which nutrients and other
dissolved substances can diffuse
– Composed of:
• Interstitial fluid
• Cell adhesion proteins
• Proteoglycans – helps determine the stiffness of the
ground substance
• Fibers – makes the fluid less pliable
Connective tissue cont.
• Fibers –
– Provide support
– Collagen fibers –
• Strong
• Provide large amounts of tensile strength (ability to resist
longitudinal strain)
• Composed of fiberous protein: collagen
• Has a glistening appearance; also called white fibers
– Elastic fibers –
• Elastin proteins
• Allows fibers to stretch & recoil
• Skin, lungs, & blood vessels
– Reticular fibers –
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Reticul – “network”
Fine collagenous fibers that form networks
Extensive branching network
Surrounds blood vessels, supports soft tissue organs, & around
basement membranes
Connective tissue cont.
• Fundamental cell types –
– All connective tissues have an immature
and mature cell form
– “blast” – actively forming cells – secrete
ground substance & fibers characteristic of
the matrix
• 4 primary blast cells –
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Osteoblast – bone cells
Fibroblast – connective tissue proper
Chondroblast – cartilage
Hematopoietic stem cell – blood
– “cyte” – inactive mature cells
• Osteocyte – mature bone cells
• Chondrocyte – mature cartilage cells
Types of connective tissue
• Connective tissue proper –
– Loose connective
• Areolar, adipose, & reticular
– Dense connective
• Dense regular, dense irregular
Loose connective tissue
• Areolar –
– “areola” – a small open space
– Binds body parts together while allowing them to
move freely over one another
– Wraps small blood vessels & nerves
– Surrounds glands
– Forms subcutaneous tissue
– Most widely distributed connective tissue
– Contains fibroblasts –actively mitotic fiber cells
– Loose arrangement of tissue – provides a
reservoir of water and salt
Areolar
Loose connective tissue
• Adipose –
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Fat tissue
Contain a pure fat droplet, displaces nucleus
Highly vascularized – high metabolic activity
Closely packed cells – little matrix
Adipocytes –
• Fat cells
• Mature cells are some of the largest cells in the body
• Mature cells can’t divide
– Develops where areolar tissue is plentiful
– Insulation, stores nutrients, & shock absorber
– Brown fat –
• Consumes its stored nutrients to generate heat to warm
the body
• Occurs in babies who lack the ability to produce their
own heat through shivering
Adipose
Loose connective tissue
• Reticular connective tissue –
– Resembles areolar tissue
– Contains only reticular fibers
– Forms stroma • Internal framework
• Supports blood cells
• Lymph system, spleen, & bone marrow
– Limited within the body even though
reticular fibers are numerous
Reticular
Dense connective tissue
• Dense regular –
– Contains closely packed bundles of collagen fibers
running in the same direction
– Run parallel to the direction of pull
– Makes up tendons (attach muscle to bone) and
ligaments (attach bone to other joints)
– Great resistance to tension – exerted in a single
direction
– Poorly vascularized – slow regeneration
Dense regular
Dense connective tissue
• Dense irregular tissue –
– Contains thick bundles of collagen fibers
– Arranged in an irregular (more than one
plane) fashion
– Found in:
• Dermis
• Joint capsules
Dense irregular
Cartilage
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Lacks nerve fibers (not innervated)
Avascular
Withstands tension & compression
Tough but flexible
Ground substance –
– Collagen fibers
– Elastic fibers
– Water (80%)
• Allows cartilage to rebound after being compressed
• Nourishes the cartilage cells
• Chondroblasts – produces new matrix
• Chondrocytes – found in small groups w/in cavities
(lacunae)
Cartilage cont.
• Hyaline –
– Hyalin = glass
– Collagen fibers are not apparent within the matrix
– gives it a glass like appearance
– Gristle
– Most abundant cartilage
– Providing firm support with some pliability
– Covers the ends of long bones
– Absorbs compression
– Supports the tip of the nose & connects ribs to
sternum
– Epiphyseal plates – actively growing regions near
the end of long bones – continued growth in length
Hyaline
Cartilage cont.
• Elastic –
– Found where strength & exceptional
stretch are needed
– Contains large amounts of elastin fibers –
• Allows for repeated bending
– External ear
– Epiglottis – covering the respiratory system
Elastic
Cartilage cont.
• Fibrocartilage –
– Found where strong support & ability to
withstand pressure are required
– Rows of chondrocytes alternating with
rows of thick collagen fibers
– Compresses and resists tension
– Intervertebral disks
– Spongy cartilage of the knee joint
Fibrocartilage
Bone
• Bone –
– Osseous
– Supports & protects the body
– Additional collagen fibers & calcium salts found in
extracellular matrix
– Provides cavities for fat storage & blood cells
– Osteoblasts – produce organic portions of the
matrix – bone salts deposited on & between the
fibers
– Osteocytes – reside in the lacunae
– Highly vascularized
Bone (osseous tissue)
Blood
• Blood –
– Classified as a connective tissue
because...
• Developed from mesenchyme
• Consists of blood cells & plasma proteins
surrounded by plasma
• Fibers – soluble protein molecules that become
visible during clotting
• Transport vehicle for the body
Blood