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 Two factors determine the movement of materials in and out of capillaries: blood pressure and osmotic pressure Because BP decreases.
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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
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
RBC and plasma proteins too big to pass out of capillaries
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
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
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
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
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)
Aneurysm
Weakened artery wall Can rupture resulting in hemorrage Results in lack of blood – oxygen to particular
tissues
Varicose veins
Valves in veins become weak and lose function Decrease of blood flow therefore increased
volume stays in the veins
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.