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The Venous Vascular System (Small, Medium and Large Veins (Tunica…
The Venous Vascular System
Functions
Collection of blood from the capillary system
Return of blood to the heart for recirculation to the Pulmonary and systemic circulatory systems.
Features
Skeletal muscle assisted blood flow
Inspiration assisted blood flow
Valve assisted blood flow
Larger capacity compared to arteries, hence retains 70% of blood volume.
Low pressure blood flow
Muscular Venules
Tunica Media
Smooth muscle fibres (2 layers)
Tunica Adventitia (Broadest Layer)
Vasa vasorum
Lymphatics
Collegen fibres
Nerve fibres
Connective tissue
Tunica Intima
Basal lamina
Collagen fibres
Endothelium of squamous cells
Small, Medium and Large Veins
LAYER OF INTERNAL ELASTIC LAMINA
Tunica Media
Reticular fibres
Few elastic fibres
Few layers of smooth muscle fibres (circular)
Tunica Intima
Basal lamina
Admixture of reticular, collagen and elastic fibres
Endothelium of squamous cells
Tunica Adventitia (Broadest Layer)
Vasa vasorum
Smooth muscle fibres with longitudinal large veins
Lymphatics
Collagen tissue wuth longitudinal fibres
Nerve fibres
In the Vena cavae, the smooth muscle fibres of the tunica media are longitudinal.
The vena cavae and the pulmonary veins acquire
cardiac muscle fibres in the tunica adventitia
as they approach the heart.