Circulatory System Flashcards
How does the vasculature of the CVS change as it goes from the heart to the body?
from the heart, large arteries branch into progressively smaller arteries that deliver blood to various parts of the body
What do arteries branch into when reaching an organ?
when a small artery reaches an organ, it branches into smaller arterioles , which branch into capillaries
What do capillary networks do and what do they rejoin to form?
capillary networks exchange
substances between the blood and cells, then rejoin to form small venules
What do small rejoin to form?
small veins progressively join to form larger veins that eventually become the veins that enter the heart
What is the general structure of arteries? Why do they need this structure?
arteries have relatively large diameters to deal with higher blood pressures
What are the three major layers of arteries?
(Describe what type of cells are in each layer)
artery walls consist of three major tissue layers
-an outer layer of connective tissue containing collagen and elastin fibers, which gives the vessel recoil ability
-a relatively thick middle layer of vascular smooth muscle cells, also mixed with elastin fibers
-a thin inner layer of flattened cells ( endothelium )
What is the structure of capillaries? Why does it have this structure?
capillary walls consist of a single layer of endothelial cells through which gases, nutrients, and wastes are exchanged with the interstitial fluid
How is blood flow through capillaries regulated?
blood flow through the capillary networks is controlled by contraction of smooth muscle in the arterioles
a small ring of smooth muscle (precapillary sphincter) at the junction between an arteriole and a capillary adjusts the rate of flow through the capillary network
a small ring of smooth muscle (____ ____) at the junction between an arteriole and a capillary adjusts the rate of flow through the capillary networks
precapillary sphincter
How is the flow of blood through and organ regulated?
the volume of blood flowing through an organ is adjusted by regulating the internal diameter of the arterioles of the organ
How small is a capillary?
the diameter of capillaries is so small that red blood cells must squeeze through in single file
What can pass through during vasoendothelial exchange?
narrow spaces between capillary endothelial cells allow water, ions, and small molecules such as glucose to pass freely between the blood and interstitial fluid
resistance to blood flow in capillaries is ____?
High
resistance to blood flow in capillaries is high. What does this cause and why is this necessary?
resistance to blood flow in capillaries is high, so blood slows down – rate of flow increases when blood returns to veins
slow movement of blood through capillaries maximizes the time for exchange of substances between blood and tissues
What can pass through during vasoendothelial exchange and by what means does this occur?
narrow spaces between capillary endothelial cells allow water, ions, and small molecules such as glucose to pass freely between the blood and interstitial fluid
leukocytes are able to squeeze actively between the cells and pass from the blood to the interstitial fluid
What drives exchange between capillaries and interstitial fluid?
two major mechanisms drive exchange of molecules and ions between capillaries and interstitial fluid: (1) diffusion along concentration gradients, and (2) bulk flow
What is unable to pass through in vasoendothelial exchange?
erythrocytes, platelets, and plasma proteins are too large to pass between cells, and are retained inside the capillaries – except for molecules transported by specific carriers
How does glucose, O2, and CO2 pass through endothelial cells plasma membrane?
O2 and CO2 diffuse directly through the lipid bilayer of endothelial cell plasma membranes – glucose passes by facilitated diffusion through transport proteins
What does bulk flow do?
bulk flow carries water, ions, and molecules out of the capillaries through spaces between capillary endothelial cells
Where is total diffusion in capillaries the greatest and why?
total diffusion is greatest near the arterioles, where the concentration differences between blood plasma and interstitial fluid are highest
What is bulk flow driven by?
bulk flow is driven by blood pressure, which is higher than the pressure of the interstitial fluid
Where is bulk flow the greatest?
like diffusion, bulk flow is greatest near the arterioles, where the pressure difference is highest
What is the structure of veins?
What can they act as?
the walls of venules and veins are thinner than those of arteries and contain little elastin
many veins have interior flaps of connective tissue that form one-way valves that keep blood flowing toward the heart
the thin walls expand and contract over a relatively wide range, allowing venules and veins to act as blood reservoirs
What is deep vein thrombosis?
lack of skeletal muscle activity can lead to blood clots ( deep vein thrombosis ) and cause serious medical problems
[Blood clot in deep veins of legs]
Where atherosclerotic plaques form?
What can they cause?
atherosclerotic plaques may form at damaged sites, reducing blood vessel diameter and impeding blood flow
damaged endothelial lining may trigger formation of blood clots, which may break loose and block other blood vessels
What can cause heart attacks and strokes?
atherosclerosis in the coronary arteries can reduce or block the flow of blood to heart muscle cells, causing a heart attack
blockage of arteries in the brain is a common cause of stroke (cerebrovascular disease), causing a loss of critical brain functions
How atherosclerosis prevented?
risk of heart attacks and stroke can be reduced by avoiding conditions that damage blood vessel endothelium (regular exercise, for eg.)
Why is lymphatic system important (3)?
under normal conditions, more fluid (from plasma) moves out of capillaries than into them
the lymphatic system collects excess interstitial fluid (lymph) and returns it to the venous blood
this system also collects fats that have been absorbed from the small intestine and delivers them to the blood circulation
the lymphatic system is a key component of the immune system
Where do lymphatic vessels dump lymph?
lymphatic vessels collect lymph and transport it to lymph ducts that empty into veins of the circulatory system
What are lymph capillaries?
lymph capillaries are thin walled vessels that are distributed throughout the body, associated with capillaries of the circulatory system (but slightly larger than blood capillaries)
What is the relation between lymph and interstitial fluid?
How does this related to the structure of lymph capillaries?
interstitial fluid enters lymph capillaries (becoming lymph) where the endothelial cells overlap, forming a flap
What does large opening in lymph capillaries allow?
the large openings admit all components of interstitial fluid, including bacteria, damaged cells, debris, and lymphocytes
What is the path of lymphatic flow?
lymph capillaries merge into lymph vessels with one-way valves that prevent lymph from flowing backward
lymph vessels lead to the thoracic duct and the right lymphatic duct, which empty the lymph into a vein beneath the clavicles (collarbones)
What prevents backflow of lymph?
One-way valves
What helps move lymph?
movements of skeletal muscles and breathing movements help move the lymph through the vessels
What are 5 lymphatic tissues/organs?
tissues and organs of the lymphatic system include the lymph nodes, spleen, thymus, and tonsils
patches of lymphoid tissue are also scattered in other regions of the body, such as the small intestine and appendix
What do does lymph tissue/organs do?
filters viruses, bacteria, damaged cells, and cellular debris from the lymph and bloodstream, and help defend the body against infection and cancer
Where lymph nodes located?
lymph nodes are clustered along the sides of the neck, in the armpits and groin, and in the abdomen and chest cavity
What do lymph nodes contain?
the nodes contain macrophages that engulf and destroy cellular debris, infecting bacteria and viruses in the lymph
other leukocytes in lymph nodes produce antibodies that aid in the destruction of invading pathogens
What happens to cancer cells in lymph nodes?
cancer cells in the nodes may be destroyed or may remain to grow and divide, forming new tumors within the nodes
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