الفهرس 
Effect of ageing on blood vesselsOnly 14 pages are availabe for public view
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Abstract
This research was conducted to study the structure of aortic valve in different age groups of albino rats, and also to clarify the structural change in the valve in the eldery that might be a contributing factor in the valvular heart disease.
In this study thirty male albino rats were used and divided into three groups including juvenile (21 days), adult (3-4 months) and senile (24 months). Animals of all groups were anaesthetized with ether. The thoracic wall was opened and the hearts were extracted and examined by light microscope.
Examination of the aortic valve of juvenile groups revealed that the valve was consisted of 3 semilunar cusps (leaflets). Each cusp attached to sinus wall by area of connective tissue called annulus. The aortic and ventricular surfaces of the leaflet were invested with thin endothelial layer continuous with that of the aortic sinus and heart chambers respectively.
The valve leaflets were consisted of 3 distinct layers (1) lamina fibrosa (2) lamina spongiosa and lamina ventricularis. Each lamina consisted of connective tissue matrix with intersititial spindle shape cells enmeshed in it.
In adult groups the surface of the lamina fibrosa appeared corrugated, covered by endothelial cells. It is formed of dense parallel wavy or circumferential arranged collagen fibers. The lamina spongiosa is consisted of loose arranged collagen and elastic fibers which were widely separated by large spaces. The lamina ventricularis is formed of dense thick compact connective tissue matrix consisted of wavy, dense and parallel elastic fibers with few collagen fibers covered by endothelial cells.
In senile age groups, the surface of lamina fibrosa appeared smooth and the endothelial cells were apparently less numerous than the adult group. Both collagen and elastic fibers were fragmented and disorgnized. The lamina spongiosa appeared thick lost its regular pattern of arrangement, the collagen fibers within this layer appeared illdefined and elastic fibers were fragmented and disorganized. The endothelial surface of lamina ventricularis appeared irregular, the collagen bundles were dense and wavy while in some areas were disorganized. The elastic fibers were disrupted and ill defined. Focal desquamation of endothelial cells with aggregation of RBCs were also noticed.
Chondrocytes cells were observed at the site of attachment of the leaflet to the valve annulus. Empty lacunae were also seen.