Chapter 19 Flashcards
Name 3 vessels in the delivery system that carries blood to and from the heart and describe what they do
arteries, capillaries, veins
Name the 3 layers in the arteries and veins
tunica externa
tunica media
tunica intima
Which layer does the capillaries have?
tunica intima
What is the fluid filled cavity in the centre of the vessels?
lumen
What lines the tunica intima and what is its function?
endothelium simple squamous epithelium; friction free surface
What is the tunica media made of and what is its function?
circular smooth muscle and sheets of elastin; controls diameter of vessel
What controls the vasoconstriction and vasodilation of vessels?
vasomotor nerve fibers
What is the tunica externa made of and what is its function?
loose network of collage fibers; anchors and reinforces vessel
What additionally does the tunica externa contain and what does large veins have and for what purpose?
nerves, lymph vessles and blood vessels; elastin fibers to allow stretch
Name 3 types of arteries
elastic arteries
muscular arteries
arterioles
What is the function of the elastic arteries and where are they located?
provides low resistance pathway; expand and recoil as blood is ejected from the heart
closest to the heart
Where are muscular arteries located and what is their function?
located distal to elastic arteries; vasoconstriction, control blood flow to different parts of the body
deliver blood to body organs
What are the smallest arteries and what is their function?
arterioles; control flow into capillary beds by dilating or constricting
Name the two types of arterioles
terminal arteriole and metarteriole
What are the microscopic bloods vessels that only allow a single RBC to pass?
capillaries
How many layers do the capillaries have and describe? What is the main function of the capillary
one layer of simple squamous epithelial cells
exchanges with tissue cells
What are the smooth muscle like cells that reinforce capillary walls and what is their function?
pericytes; regulate permeability
Name the 3 types of capillaries
continuous capillaries
fenestrated capillaries
sinusoidal capillaries
Where are continuous capillaries most abundant and what allows the passage of fluids and small solutes? What connects the endothelial cells?
skin and muscles; intercellular clefts
tight junctions
What is the difference between fenestrated capillaries and continuous capillaries?
they are more permeable
What is the function of fenestrated capillaries? Where are they located?
absorption of filtrate formation
located: small intestines, endocrine glands and kidneys
Where are sinusoidal capillaries located and what is their function?
found in liver, bone marrow and spleen
blood cells and large molecules to pass
What are capillary beds and what do they do?
interwoven networks of capillaries form the circulation between arterioles and venules
What are the two types of vessels in a capillary bed?
true capillaries
vascular shunt (metarteriole / thoroughfare channel)
What is the function of the precapillary sphincters?
regulate blood flow into true capillaries
What is blood flow regulated by in the capillary beds and why is the blood flow slow?
regulated by local chemicals and vasomotor nerves
slow to allow exchanges of materials with tissue cells (more efficient exchange due to slowness)
What is the function of the arteriovenous shunts?
bypass capillary beds, direct blood to where it is needed
What happens the the size of the vein as blood travels towards the heart?
the diameter growsq
What is the function of the venule?
collect blood from capillary beds
Describe the venule.
very porous: allow fluids and WBC’s into tissues
post capillary venules consist of endothelium and a few pericytes
larger venules have one or two layers of smooth muscle cells
What is the function of the vein?
acts as blood reservoirs; collect blood from venules and carry to heart
contain up to 65% of blood supply
What are the venous valves function and where are they most abundant?
prevent backflow of blood; most abundant in veins of the limbs
What causes varicose veins?
leaky valves
What is the venous sinus?
flattened veins with extremely thin walls of only endothelium
Name the two venous sinus’ and what is their function?
coronary sinus: collects deoxygenated blood from cardiac veins
dural sinus: collects blood draining from brain
What are vascular anastomoses and what do they do?
interconnections of blood vessels
arterial anastomoses provide alternate pathways to a given region (common at joints, abdominal organs, brain, heart)
What are the alternated pathways called formed by anastomoses?
collateral channels
What happens the the size of the vein as blood travels towards the heart?
the diameter growsq
What is the function of the venule?
collect blood from capillary beds
Describe the venule.
very porous: allow fluids and WBC’s into tissues
post capillary venules consist of endothelium and a few pericytes
larger venules have one or two layers of smooth muscle cells
What is the function of the vein?
acts as blood reservoirs; collect blood from venules and carry to heart
contain up to 65% of blood supply
What are the venous valves function and where are they most abundant?
prevent backflow of blood; most abundant in veins of the limbs
What causes varicose veins?
leaky valves
What is the venous sinus?
flattened veins with extremely thin walls of only endothelium
Name the two venous sinus’ and what is their function?
coronary sinus: collects deoxygenated blood from cardiac veins
dural sinus: collects blood draining from brain
What are vascular anastomoses and what do they do?
interconnections of blood vessels
arterial anastomoses provide alternate pathways to a given region (common at joints, abdominal organs, brain, heart)
What are the alternated pathways called formed by anastomoses?
collateral channels
Define blood flow
volume of blood flowing through a vessel, an organ, or the entire circulation in a given period (usually per minute)
How is blood flow measured?
ml/min
Define blood pressure
force per unit area exerted on the wall of a blood vessel by the blood
How is it measured?
mm Hg
What pressure gradient does blood move from?
blood moves from high to low pressure
What is resistance?
opposition to flow; is a measure of the amount of friction blood encounters
What are the 3 important sources of resistance?
- blood viscosity
- total blood vessel length
- blood vessel diameter
What happens if the radius is halved in terms of resistance? What happens to the vessel?
resistance increased by 16 times
What are the major determinants of peripheral resistance?
small diameter arterioles
Blood flow is directly proportional to pressure gradient…if the pressure gradient increases, blood flow…..
speeds up
Blood flow is inversely proportional to resistance - if resistance increases, blood flow…..
decreases
Where is systemic pressure the highest?
in the aorta
Systemic pressure is lowest in which vessels?
the veins
Where does the steepest drop occur with systemic pressure?
arterioles
What does systemic pressure measure as in the right atrium?
0 mm Hg
Where is arterial blood pressure measured?
in the aorta
What is systolic pressure?
pressure exerted during ventricular contraction
What is diastolic pressure?
pressure exerted during ventricular diastole
What is pulse pressure?
systolic pressure minus diastolic pressure
What is mean arterial pressure (MAP)?
average pressure that propels the blood through the body
What is the forumla for MAP?
systolic - diastolic / 3 then…
plus diastolic = MAP
Name 3 main factors influencing blood pressure
- cardiac output (CO = HRxSV)
- blood viscosity and volume
- peripheral resistance
What is the resting heart rate maintained by?
cardioinhibitory center via parasympathetic vagus nerves
What is the function of the neural controls and how do they accomplish this?
controls of peripheral resistance
- maintain MAP by altering blood vessel diameter
- alter blood distribution in response to specific demands (ie. fight or flight response)
What is the function of the vasomotor centre?
cluster of sympathetic neurons in the medulla that oversea changes in vessel diameter
What is vasomotor tone?
moderate constriction of arterioles
