Types of Capillaries

Types of Capillaries - * Have thinner walls than arteries...

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Cardiovascular System Types of Capillaries Fenestrated capllaries * cells are riddled with holes called fenestrations (filtration pores) * fenestrations are covered by a thin mucoprotein diaphragm * they allow for the rapid passage of small molecules but retain proteins and larger particles in the blood stream * are important in organs that engage in rapid absorption or filtration (kidneys, endocrine glands, small intestine, choroid plexus of brain) Types of Capillaries Sinusoid capillary * irregular bllood filled spaces that serves as passageways that allow blood plasma to come into direct contact with the parivascular cells * Pores allow passage of proteins and blood cells * how albumin, clotting factors, and other large proteins synthesizes by the liver enter the blood * how newly formed blood cells inter the circulation from the bone marrow and lymphatic organs Veins * Blood collects from the capillaries to the venules that are able to exchange fluid with the surrounding tissues * veins have much lower blood pressure than arteries (avg. 10 mmHg vs. 100mmHg)
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Unformatted text preview: * Have thinner walls than arteries with less muscular and elastic tissue * They collapse when empty and look flattened or irregular in histologic sections * Expand more easily and accommodate more blood than do arteries * approx. 54% of the blood is found in the systemic veins at rest (called capacitance vessels ) Veins * Pressure in the veins is not high enough to push blood upward against gravity to the heart * flow of blood back to the heart depends on the * messaging action of skeletal muscle * one-way valves that keep blood from dropping down again when the muscles relax * thoracic (respiratory) pump * cardiac suction-chordae tendeneae pulls AV valves cusps downward, slightly expanding the atrial space, creating a slight suction * gravity-blood flow from head * Valves occur especially in medium sized veins of the arms and legs * They are absent from very small and very large veins of the ventral body cavity and brain...
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