BIOL 1050H Lecture Notes - Lecture 7: Common Iliac Artery, Tunica Externa, Loose Connective Tissue
Circulatory System Part 3
General Anatomy of the Blood Vessels
• Arteries:
• Carry blood away from heart
• Resistance vessels
• Veins:
• Carry blood back to heart
• Capacitance vessels (storage)
• Capillaries connect smallest
arteries to smallest veins
The Vessel Wall
Tunica interna • Endothelium: simple squamous epithelium overlying basement
membrane and sparse layer of loose connective tissue
Tunica media • Consists of smooth muscle, collagen, and elastic tissue
Strengthens vessels
• Smooth muscle regulates diameter of the blood vessel
Tunica externa • Consists of loose connective tissue that often merges with that of
neighboring blood vessels, nerves, or other organs
• Anchors the vessel and provides passage for small nerves, lymphatic
vessels
Walls of arteries and veins
have 3 layers (tunics):
Arteries
Conducting (elastic or large) arteries • i.e. Aorta, common carotid, subclavian,
pulmonary trunk, and common iliac
arteries
• Have a layer of elastic tissue, internal
elastic lamina, at border between
interna and media
Distributing (muscular or medium)
arteries • Distributes blood to specific organs (i.e.
Brachial, femoral, renal, and splenic
arteries)
• Smooth muscle layers constitute 3/4 of
wall thickness
