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Capillary fluid exchange

Capillary fluid exchange. Two factors determine the movement of materials in and out of capillaries: blood pressure and osmotic pressure Because BP decreases as blood travels further from left side of the heart, the BP on the arteriolar and of the capillary is greater than at the venule end.

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Capillary fluid exchange

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  1. Capillary fluid exchange • Two factors determine the movement of materials in and out of capillaries: blood pressure and osmotic pressure • Because BP decreases as blood travels further from left side of the heart, the BP on the arteriolar and of the capillary is greater than at the venule end

  2. Osmotic pressure (OP) results primarily from the presence of plasma proteins and minerals (salts) • OP stays relatively constant • Blood plasma (fluid) contains dissolved solutes that are small (minerals, aa's, glucose, etc) • At capillary end, BP>OP, therefore, fluid with dissolved solutes moves into tissues • In the middle, BP = OP therefore, nutrients and wastes move based on concentration gradients • At venule end, BP<OP, therefore fluid and solutes are drawn into capillary

  3. RBC and plasma proteins too big to pass out of capillaries

  4. Circulatory diseases • Hypertension • High blood pressure caused by increased resistance to blood flow • High BP puts extra strain on heart, so heart must work harder to move blood

  5. Causes of hypertension • Stress: causes stimulation of sympathetic nervous system, which leads to constriction of arteries (vasoconstriction). This causes kidneys to secrete renin, a hormone that brings high BP due to sodium retention (increase blood volume) • Diet: high in salt causes water retention (increased blood volume and BP) • Athersclerosis: build up of plaque in arteries decreases capacity of artery, increases BP

  6. Hypotension • Decreased BP resulting in decreased blood flow to the brain and heart. Body responds by stimulating nervous system (stress reaction) • Causes: • Blood loss • extreme emotion (leads to fainting) • genetic

  7. Athersclerosis vs Arteriosclerosis • Arteriosclerosis means hardening of arteries • Arteries become rigid, may decrease in diameter and lose elasticity • Atherosclerosis is a type of this in which plaque build up is the cause • Can lead to strokes and heart attacks

  8. Stroke and heart attack • A stroke occurs when brain tissue dies as a result of lack of blood flow • Can be result of an embolism blocking the blood flow (piece of plaque) in the brain • A heart attack occurs when heart muscle tissue dies as a result of a lack of blood flow • Caused by a blockage of coronary arteries • Early stages of heart attack results in angina (chest pains)

  9. Aneurysm • Weakened artery wall • Can rupture resulting in hemorrage • Results in lack of blood – oxygen to particular tissues

  10. Varicose veins • Valves in veins become weak and lose function • Decrease of blood flow therefore increased volume stays in the veins

  11. Sympathetic and parasympathetic nervous system The autonomic nervous system directs all activities of the body that occur without a person's conscious control It has two parts: the sympathetic division, which is most active in times of stress, and the parasympathetic division, which controls maintenance activities and helps conserve the body's energy.

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