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Lecture 24
Capillaries-Lymph-Veins
Term | Definition |
---|---|
Capillary Blood Flow | Very slow-many capillaries spread flow out and reduce speed |
Capillary Pressure | 37 mmHg at arteriolar and down to 17mmHg at venous end |
Capillary Fluid Exchange | Balance of BP forcing fluid out and osmotic pressure from plasma proteins drawing fluid in. Fluid moves through capillary pores |
Filtration | Domainates at high pressure and (arteriolar) BP>osmotic pressure-fluid forced out. |
Reabsorption | At venous end lower BP, BP<osmotic pressure,fluid reenters. Net fluid sweeps volume around capillary, slightly more fluid filtered than reabsorbed. |
Lymph Flow | Return of excess filtered fluid to circulation |
Return of Filtered Fluid | Fluid enters closed-ended lymph vessels, which merge w/ others.Lymph nodes are sites of large lymph vessel merger. Large lymph vessels have valves lymph enters vena cava (BP=0) at the thoracic duct in chest. |
Edema | Swelling. Excess filtration (broken capillaries). Low blood protein (starvation,alcoholism). Bacteria presence and destruction draws fluid osmotically. Parasites-filariasis-black lymph flow-fatal. |
Venous Flow | Capacitance vessels, hold largest blood volume |
Venous Pressure | 17 mmHg at capillary end to 0 at vena cava. During inspiration, vessels in thorax may have negative pressure. BP needs help getting blood up to heart. |
Venous Valves | Prevent backflow. Every 1-2 in. in large veins. Valves can be demonstrated on veins on back of hand. |
Skeletal Pump | Muscle concentration squeezes veins-forces blood to heart. |
Varicose Veins | Ruptured valves-column of blood,slow return. Clots may form. Blood bypasses varicosites through other veins. |