Vascular System 3 Flashcards
What helps exchange molecules between tissues and molecules?
Large surface area and slow rate
Capillaries are so branched that blood passes slowly, but still has the same amount - because many branches
-> slow movement provides time for exchange
What are Starlings forces and what does it affect?
Hydrostatic and osmotic (oncotic) pressure - the presence of protein too big to leave capillary, small enough to be dissolved -> forcing water to come in and dissolve them
It affects bulk flow (water and dissolved substances)
Explain different pressure in and around capillaries!
-Capillary hydrostatic pressure = blood pressure exerted by blood to the capillary wall
-osmotic force (oncotic) in capillary = due to proteins
-osmotic force in interstitial fluid = almost 0, due to proteins in fluid,
-Interstitial fluid: is almost 0 because the fluid is vast and spreaded
What is net filtration?
Factors affecting filtration minus Factors affecting absorption
Pc (capillary) + osmotic force (interst.) minus P(IF) - osmotic force (capillary)
Why does filtration occur at the arterial end?
Because of the capillary hydrostatic pressure, represented by hydrostatic pressure which is greater than the capillary osmotic pressure at the arterial end
Why does absorption occur at the venous end?
Because the capillary pressure at the venous is smaller than the capillary osmotic pressure
9/10 of fluid exiting at the arterial end reenters the capillary at the venous end, and 1/10 goes to lymphatic capillaries because the tissue would swell because of the increasing amount of interstitial fluid
How do veins ensure blood flow, despite low pressure?
-Thinner muscle walls
-Large lumens, helps to provide less resistance to flow
-Constriction of veins to shift blood to other parts of the heart (arteries) f.e. in case of blood loss
-Valves prevent black flow
-Breathing: pressure helps venous return
-constriction of skeletal muscle compress veins: venomotor pump
Where do we find the most amount of blood at any time?
In the veins: Blood reservoir (Capacitance vessels): 61% in veins and venules
How EDV (venous return) can be increased?
Decreasing venous volume (constriction of veins) or increase of total blood volume through hormones controlling the amount of water
Functions of the lymphatic system
Transport excess fluid away from interstitial space and back to the bloodstream (to veins)
Transport fats to the bloodstream
Help to fight diseases
What is lymph?
It is basically the interstitial fluid, formed by the mismatch between filtration and absorption, that enters the lymphatic system and returns via the veins
Explain the direction of flow in the lymphatic system!
branched between systemic and pulmonary circulation
In one direction towards the heart from the pulmonary and systemic circulation, the capillaries are one-site ended
connected to the pulmonary and systemic circulation
Order of lymph transport!
Lymphatic capillaries collecting fluid from systemic circulation -> collecting vessels (one-way valve) -> Lymph nodes -> Lymph trunk ->right lymphatic duct and thoracic ducts -> veins
What are the two major lymphatic ducts?
Right lymphatic duct: below the subclavian vein -> drains the right upper arm and right side of the arm, head, and thorax
Thoracic lymphatic duct: drains the rest of the body
Where do lymph nodes come together?
Behind the neck - cervical: vessel draining face, nasal cavity tissue, pharynx
axillary (armpit): vessels draining upper limbs, abdomen, mammary glands (women)
inguinal: vessel draining lower limbs, external genitalia, lower abdomen
