12C.3 –Know the structure and function of capillaries and how blood flows through them (eg. Velocity of blood flow through capillaries ). Capillaries are only a few cells thick and there are 25000 miles of them in a human. They are so small that the diffusion distance is very short which makes this transfer very effiecient. The capillairies are where all of the exchange of nutrients, end porducts and metabolic things happen. The velocity of blood through the capillaries is very slow to allow for more diffusion to occur Know the three ways that materials can move in and out of capillaries (diffusion, vesicle transport, bulk flow) and how each works. Diffusion- There are water channels in the capillary that allow water soluable things to be transferred without help. Diffusion of certain materials is more prominent in certain areas where the materials are more readily used. Vesicle Transport- the use of endocytosis or exocytosis Bulk Flow- this is used to even out the distribution of extracellular fluid. This is affected by the blood pressure in the capillary and the interstitial fluid pressure. The blood pressure is much greater then the interstitial fluid so much plasma empties into the interstitial space. It does not all empty there though because the interstitial fluid is pushing back. How does the filtration rate vary from the arteriole end of a capillary to the venule end? 12C.4 – Know the structure and functions of veins. The function of veins are to take deoxygenated blood back into the heart. Veins have a much larger diameter then arteries do but their diameter can change do to a change in blood volume so that the blood getting back to the heart remains constant. Know what factors influence venous pressure and the forces that make blood flow back to the heart. Factors determining venous pressure: volume of fluid within, compliance of its walls; Factors that make blood flow back to the heart: Release of NorE: causes contraction on the veins which increases the pressure within them Skeletal muscle pump: when the muscles contract it causes the veins to contract sending blood to the heart Respiratory Pump- When the diaphragm descends pushing on abdominal muscles which increases abdominal pressure. This pressure is pushed onto the adominal veins which increases return to the heart What proportion of the total blood volume is in veins vs. arteries? 60% Understand the relationship between venous pressure and cardiac output. Any change in venous pressure is directly linked to cardiac output. 12C.5 – understand the structure and function of the lymphatic system and the mechanism of flow of lymph through the vessels. The function of the lymphatic system is to drain interstitial fluid from the blood, also it is an easy route for fat that is absorbed from the GI tract to return to the blood. The lymphatic system is only made out of capillaries and lymph nodes. Interstitial fluid flows into the capillaries by bulk flow. Eventually the whole lymphatic network combines into two main ducts that drain into the veins near the heart. The lymphatic vessels are made out of
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- Winter '15
- Jacques Hill