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What are the three layers of the blood vessel wall?
Tunica intima, Tunica Media, Tunica Adventitia
What is the main function of capillaries?
Veins carry blood that is high in oxygen.
False
Arterioles are the smallest branches of the arterial system and deliver blood to the smallest blood vessels, the ___.
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Match the following blood vessels with their characteristics:
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What are the three layers of the blood vessel wall?
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Which type of vessel carries blood back to the heart?
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______ prevents blood from flowing backwards in veins.
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Capillaries have fenestrae in their walls covered by a diaphragm.
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Match the following blood vessels with their characteristics:
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Study Notes
Blood Vessels
- Blood vessels include arteries, veins, and connections between them
- The wall of a blood vessel is formed of three layers: tunica intima, tunica media, and tunica adventitia
Layers of Blood Vessel Wall
- Tunica intima: simple squamous epithelium, connective tissue, and internal elastic lamina
- Tunica media: smooth muscle, other fibers, and external elastic lamina
- Tunica adventitia: connective tissue
Order of Blood Vessels
- Large arteries
- Medium-sized arteries
- Arterioles
- Capillaries
- Venules
- Medium-sized veins
- Large veins
Large Arteries (Elastic Arteries)
- Wide lumen and thick wall
- Thin tunica intima
- Tunica media is very thick with muscle, collagen, reticular fibers, and elastic membranes
- Tunica adventitia is relatively thin
- Connects blood from the heart (e.g., Aorta)
Medium-Sized Arteries (Muscular Arteries)
- Narrow lumen and thick wall
- Thin tunica intima
- Tunica media is equal to adventitia in thickness with well-developed smooth muscle and some elastic fibers
- Tunica adventitia is present
- Distributes blood from large arteries (e.g., Femoral artery)
Arterioles
- Small arteries and smallest branches of the arterial system
- Deliver blood to capillaries
- Tunica intima: endothelium with no subendothelial layer or internal elastic lamina
- Tunica media: 1-5 layers of circularly arranged smooth muscle cells
- Tunica adventitia: thin and poorly developed with a thin network of collagen fibers
Capillaries
- Formed of endothelium on basement membrane and pericytes
- Two types: continuous type (tight junction between endothelial cells, e.g., in the brain) and fenestrated type (have fenestrae or pores covered by a diaphragm)
Veins
- Carry deoxygenated blood (high in carbon dioxide) back to the heart
- Have one-way valves to prevent blood from flowing backwards
- Thin-walled with large irregular lumen
- Have valves to prevent backflow
Types of Veins
- Large veins (e.g., Inferior Vena Cava)
- Medium-sized veins
- Small veins (venules)
Large Veins
- Very wide lumen
- Thin tunica intima
- Thin media with smooth muscle fibers only
- Much thicker adventitia with smooth muscle fibers longitudinally arranged
Medium-Sized Veins
- Large irregular lumen
- Thin wall
- Tunica intima: endothelium and thin layer of connective tissue
- Tunica media: few circularly arranged smooth muscle fibers, collagen fibers, and less elastic fibers
- Tunica adventitia: thicker than media, loose fibroelastic connective tissue
Venules
- Thin wall and large collapsed lumen
- Tunica intima: endothelium
- Tunica media: 1-2 layers of smooth muscle fibers
- Tunica adventitia: thick and composed of connective tissue rich in collagen fibers
Blood Vessels
- Blood vessels include arteries, veins, and connections between them
- The wall of a blood vessel is formed of three layers: tunica intima, tunica media, and tunica adventitia
Layers of Blood Vessel Wall
- Tunica intima: simple squamous epithelium, connective tissue, and internal elastic lamina
- Tunica media: smooth muscle, other fibers, and external elastic lamina
- Tunica adventitia: connective tissue
Order of Blood Vessels
- Large arteries
- Medium-sized arteries
- Arterioles
- Capillaries
- Venules
- Medium-sized veins
- Large veins
Large Arteries (Elastic Arteries)
- Wide lumen and thick wall
- Thin tunica intima
- Tunica media is very thick with muscle, collagen, reticular fibers, and elastic membranes
- Tunica adventitia is relatively thin
- Connects blood from the heart (e.g., Aorta)
Medium-Sized Arteries (Muscular Arteries)
- Narrow lumen and thick wall
- Thin tunica intima
- Tunica media is equal to adventitia in thickness with well-developed smooth muscle and some elastic fibers
- Tunica adventitia is present
- Distributes blood from large arteries (e.g., Femoral artery)
Arterioles
- Small arteries and smallest branches of the arterial system
- Deliver blood to capillaries
- Tunica intima: endothelium with no subendothelial layer or internal elastic lamina
- Tunica media: 1-5 layers of circularly arranged smooth muscle cells
- Tunica adventitia: thin and poorly developed with a thin network of collagen fibers
Capillaries
- Formed of endothelium on basement membrane and pericytes
- Two types: continuous type (tight junction between endothelial cells, e.g., in the brain) and fenestrated type (have fenestrae or pores covered by a diaphragm)
Veins
- Carry deoxygenated blood (high in carbon dioxide) back to the heart
- Have one-way valves to prevent blood from flowing backwards
- Thin-walled with large irregular lumen
- Have valves to prevent backflow
Types of Veins
- Large veins (e.g., Inferior Vena Cava)
- Medium-sized veins
- Small veins (venules)
Large Veins
- Very wide lumen
- Thin tunica intima
- Thin media with smooth muscle fibers only
- Much thicker adventitia with smooth muscle fibers longitudinally arranged
Medium-Sized Veins
- Large irregular lumen
- Thin wall
- Tunica intima: endothelium and thin layer of connective tissue
- Tunica media: few circularly arranged smooth muscle fibers, collagen fibers, and less elastic fibers
- Tunica adventitia: thicker than media, loose fibroelastic connective tissue
Venules
- Thin wall and large collapsed lumen
- Tunica intima: endothelium
- Tunica media: 1-2 layers of smooth muscle fibers
- Tunica adventitia: thick and composed of connective tissue rich in collagen fibers
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Description
Learn about the structure and components of blood vessels, including arteries, veins, and their connections. Understand the general characteristics of the blood vessel wall and its layers.
