Questions and Answers
What type of capillary has a permeability somewhere between that of continuous and sinusoidal capillaries?
Which of the following types of capillaries has a basal lamina that is discontinuous?
What is a characteristic of arterioles?
Which type of artery has a thick media composed of sheets of elastic fibers?
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What is a characteristic of venules and veins?
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Which type of capillary is found in the liver, bone marrow, and spleen?
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What is a characteristic of medium-sized veins?
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Which type of artery has a prominent internal and external elastic lamina?
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What is the primary function of the cardiovascular system?
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Which sequence correctly describes the flow of blood through the cardiovascular system?
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What are the three layers of blood vessels known as?
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Which type of capillary is the least permeable?
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What characterizes fenestrated capillaries?
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What structures are generally found in the media layer of blood vessels?
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Where would you expect to find sinusoidal capillaries?
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What is the primary role of the intima layer in blood vessels?
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Study Notes
Cardiovascular System
- The cardiovascular system transports and exchanges nutrients, oxygen, body fluids, waste material, heat, and blood cells around the body.
Blood Vessels
- Basic structure: closed system of plumbing with blood circulating through pipes (blood vessels) and propelled by an in-line pump (the heart)
- Blood flows through the system in the following order: heart → elastic artery → muscular artery → arteriole → capillaries → venules → vein → heart
The Three Layers (Tunics) of Blood Vessels
- Intima: endothelium and subendothelium
- Media: varying compositions in different vessels
- Externa: vasa vasorum and other components
Capillaries
- Smallest diameter of all blood vessels (7-9 μm)
- Function: allow exchange of metabolites and waste between blood and surrounding tissue
- Composed of a single layer of endothelial cells resting on a basal lamina
- Three types:
- Continuous capillaries (least permeable): found in muscle, connective tissue, glands, and nerve tissue
- Fenestrated capillaries: found in places where substances need to move quickly between tissues and blood (e.g. kidney, intestine, and endocrine organs)
- Sinusoidal capillaries (most permeable): found in liver, bone marrow, and spleen
Venules and Arterioles
- Relatively thin wall and big lumen in venules
- Relatively thick wall and small lumen in arterioles
- Media composition differs between venules and arterioles
Arteries
- Muscular arteries: thick media composed of smooth muscle cells, prominent internal and external elastic lamina
- Elastic arteries: thick media composed of sheets of elastic fibers, interspersed with layers of smooth muscle cells
- Examples: aorta and its large branches are elastic arteries, while "named" arteries (e.g. femoral artery) are usually muscular arteries
Veins
- Medium-sized vein: thin intima, may have valves, thin media composed of a few elastic fibers and smooth muscle cells, relatively thick externa
- Large vein: thin intima, may have valves, thin media like medium-sized veins, relatively thick externa composed of longitudinal collagen fibers, elastic fibers, and smooth muscle cells
- Examples: "named" veins (e.g. portal vein) are usually large veins
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Description
Learn about the cardiovascular system, its functions, and the structure of blood vessels, including their order and layers.
