age related connective tissue changes

what is connective tissue

1 of the 4 basic tissue types of the body

1. nervous (communication)

2. muscle (movement)

3. epithelial (barriers and boundaries)

4. connective tissue

purpose of connective tissue

1. protect (skeletal system protecting organs)

2. support (skeletal system providing structure)

3. bind (holds and anchors in body, GI tissue holding SI and LI)

4. transport (blood -O2, CO2, nutrients, waste)

5. immunity (lymphatic system, WBCs)

specialized connective tissue includes

1. bone

2. adipose

3. cartilage

4. blood

5. reticular tissue (structure→bone marrow, internal organs)

solid-bone

semisolid-adipose, cartilage

liquid-blood

what 3 things make up connective tissues

1. cells (workers, give function)

2. fibers

3. extracellular matrix/ground substance (gel, fluid rich environment)

cells of connective tissue

1. chondrocytes

2. osteocytes

3. fibroblasts

cytes=mature cell

blasts=immature cell

fibers of connective tissue

1. collagen -strong/rigid

2. elastin- soft/stretchy

3. reticular- feather like (filter)

extracellular matrix/ground substance of connective tissue

1. proteoglycans

2. glycoproteins

3. glycosaminoglycans (GAGS)

4. fluid

1-3 are combos of proteins and sugars, bind with water

construction of connective tissue is determined by

amount, type and arrangement of extracellular matrix

mechanical properties of connective tissue are determined by:

1. relative proportions of collagens and proteoglycans

connective tissue to resist high tensile forces are

high in collagen and low in total proteoglycans content

connective tissue subjected to compressive forces have

lower collagen and greater proteoglycans content (ex:articular cartilage)

fiber arrangement determines function:

1. nearly parallel fibers resist high stretching force in one direction (ex: tendon)

2. randomly laid fibers resist stretching force in multiple directions (ex: skin)

the alteration of the balance between synthesis and degradation influences…

normal tissue, architecture, impairs organ function, and changes the mechanical properties of tissues

net degradation of matrix components occurs in

osteoarthritis

rheumatoid arthritis

pulmonary emphysema

osteoporosis

net increases in the accumulation of fibers will cause

fibrotic conditions:

interstitial pulmonary fibrosis

sclerodermas

what 4 aspects of connective tissue change with age

1. collagen

2. elastin

3. water

4. proteoglycan

age related changes in collagen of CT

-fibers become smaller in diameter (less stable)

-increased cross-bridge formation (less flexible)

age related changes of elastin in CT

decreased →leads to decreased stretch and recoil

age related changes of water in CT

decreased

age related changes of proteoglycan in CT

decreased

due to age related changes of CT what happens

1. increased stiffness

2. viscoelastic properties decrease

3. decreased tensile strength (more likely to rip/tear)

what happens to the ligament/tendon connective tissue with aging

1. collagen degradation: more disorganized/less parallel fibers =less force absorption

2. glycation (waste accumulation) and stiffening: abnormal bonds between collagen, more brittle

3. matrix alterations: more GAGS, stiffness

4. decreased cellularity: less production of collagen, less regeneration

5. vascular changes: even more hypovascular

intramuscular CT is

layers of non-contractile connective tissue

cannot provide active contractile tension, but can provide passive tension or resistance to stretch

layers of intramuscular CT and what happens with age

1. endomysium -surrounds muscle cell

   1. thickness increases with age

2. perimysium- surround bundle of muscle fibers/cells

   1. thickness remains unchanged until old age when it also increases

3. epimysium -surrounds entire muscle belly

   1. follows perimysium pattern

muscle fibers alone can be easily torn, and fibrous CT provides

support and resists tension forces

hyaline articular cartilage

lines the articular ends of bone and reduces wear

-lubricates and absorbs shock

-protects from transarticular forces (shearing)

elastic quality of tissue dissipates high loads

decreases rate of compression on joint surfaces

hyaline (articular) cartilage with aging

1. shortened proteoglycans can lose their ability to hold water

2. ability to dissipate forces reduced

3. susceptible to mechanical failure

bone cells

osteocytes, osteoblasts, osteoclasts

bone organic matrix

collagen and proteoglycans

-contributes to bone flexibility and resistance `

bone inorganic matrix

calcium

-contributes to exceptional hardness of bone and resists compressive forces

bone aging

-bone shape and density depends on mechanical and physiological mechanisms

-loss of bone mass

behavior of bone in response to force is affected by:

1. mechanical properties of bone

2. geometry of particular bone

3. rate and frequency of loading

4. type of loading (compression, tension, bending, shear, torsion)

ultraviolet light damages to skin

initiates inflammatory response, increases production of the enzyme that breaks down collagen

skin aging is associated with

1. progressive increase in extensibility and reduction in elasticity

2. increased fragility and susceptibility to trauma (lacerations and bruising)

strong correlation between skin collagen loss and ___ ___

estrogen deficiency caused by menopause

pulmonary connective tissue

elastin fibers are extensible elements of the extracellular matrix

they are found throughout the tracheobronchial tree of lung

elastin fibers in the tracheobronchial tree of lung are largely responsible for

accommodating pressure changes

-the potential energy stored in the elastic fiber at the end of inspiration is released during expiration with the consequent assisted recoil of the lung tissue

lung tissue is the gas exchanging organ

-alveolar elastic tissue pulling in

-thoracic cage and muscular attachments pulling out

airway and lung changes resulting in uneven ventilation and circulation

rearrangement and fragmentation of elastic fibers

-generally confines to alveolar ducts and alveoli

-decreased recoil

-increased compliance of lung tissue

-increased closing volume

functional changes of lung from CT changes

1. air trapping

2. reduced gas exchange

3. increased work of breathing

   1. stiffening of chest wall, thinning of rib bones, weakening of respiratory muscles (diaphragm)