CH 21 Blood Vessels & Hemodynamics Flashcards
How many layers does a blood vessel have
3
What are the three layers of a blood vessel
Tunica interna, tunica media, tunica externa
Tunica interna
innermost layer, adjacent to lumen
Tunica media
middle layer, smooth muscle and elastic fibers
Tunica externa
outermost layer, adjacent to surrounding tissue
Arteries carry blood away from the BLANK and to the BLANK
heart, tissues
Components of elastic arteries
1- large thick walled arteries with elastin in all 3 tunis 2- aorta is one 3inactive in vasoconstriction 4-act as pressure reservoirs–expand and recoil as blood ejected from heart= smooth pressure downstream
Largest arterie
aorta
Components of muscular arteries
1)distal to elastic arteries 2)deliver blood to organs 3)thick tunic media with more smooth muscle 4) active in vasocontriction
What are the smallest arteries
arterioles
Arterioles lead to
capillary beds
Arterioles control
flow into capillary beds via vasodialation and vasoconstriction
Anastomoses
the union of the branches of 2 or more arteries supplying the same region of the body
Anastomoses components
1)provides an alternate route for blood flow
Arteries that do not form an anastomoses are called
end arteries
Necrosis occurs when
an artery is blocked and blood cannot get to that particular region of the body
Capillaries are
microscopic vessels that usually connect arterioles and venules
capillary walls are composed of
a single layer of cells and a basement membrane
Because their walls are so thin, capillaries permit:
the exchange of nutrients and wastes between blood and tissue cells
Continous capillaries are formed by
endothelial cells
Venules are
the small vessels formed by the union of several capillaries
Venules drain blood from BLANK into BLANK
capillaries into veins
Veins are formed from the union of several
venules
compared to arteries, veins have a thinner BLANK and BLANK and a thicker BLANK
tunica interna and media and a thincker externa
Veins have less blank and blank than arteries
elastic tissue and smooth muscle
veins contain
valves
At rest, the largest portion of the blood is in:
systemic veins and venules (blood reservoirs)
Substances cross capillary walls by (3)
diffusion, transcytosis and bulk flow
Diffusion
(passes through walls easily)substances such as oxygen, carbon dioxide, glucose, amino acids and hormones cross capillary walls via simple diffusion
Transcytosis
(endocytosis on one side and exocitosis on another) large, lipid-insoluble molecules (like insulin) cross capillary walls in vesicles via transcytosis
Bulk Flow
(goes between cells, how most things are moved such as nutrients and gases) a passive process in which large number of ions, molecules or particles in a fluid move together in the same direction
bulk flow is more important for
regulation of the relative volumes of blood and interstitial fluid
Starling’s law of capillaries
under normal conditions, the volume of fluid and solutes reabsorbed is almost as large as the volume filtered
Blood flow is
the volume of blood that flows through any tissue in a given time period
Total blood flow is
cardio output, the volume of blood that circulates through systemic (or pulmonary) blood vessels each minute
Cardio output =
heart rate X stroke volume
What generates BP
contraction of the ventricles
BP is determined by (3)
CO, blood volume and vascular resistance
the higher the BP the greater the
blood flow
systolic pressure
pressure exerted in aorta during ventricular contraction
average systolic pressure
120 mmhg in normal human
diastolic presure
lowest level of aortic pressure
pulse pressure
difference between systolic and diastolic pressure
throwing of arteries =
pulse
Vascular Resistance (R)
is the opposition to blood flow due to friction between blood and the walls of blood vessles
The higher the R (vascular resistance)
the smaller the blood flow
R (vascular resistance) depends on (3)
1) size of the blood vessel lumen 2) blood viscosity 3)total blood vessel length
Blood factors that remain relatively constant (2)
1) viscosity 2)blood vessel length
blood viscosity
the “stickiness” of blood due to formed elements and plasma proteins
Increased viscosity =
increased resistance
Longer blood vessel=
greater resistance encountered
Greatest influence on resistance
blood vessel diameter
Venous Return
the volume of blood flowing back to the heart through the systemic veins, occues due to the pressure generated by contractions of the heart’s left ventricle
Venous return is assisted by
valves, respiratory pump and skeletal muscle pump
Where is the cardiovascular center located
medulla oblongata
what is the cardiovascular center
the group of neurons that regulate heart rate, contractility and blood vessel diameter
Baroreceptors
Important pressure-sensitive sensory neurons that monitor stretching of the walls of blood vessels and the atria
2 types of blood pressure controls
1) short term neural and hormonal controls 2)long-term renal regulation
short term neural and hormonal control of BP
counteract fluctuations in blood pressure by altering peripheral resistance and CO
long-term renal regulation
contracts fluctuations in blood pressure by altering blood volume
Direct renal mechanism
alters blood volume independently of hormones.
arterial system
heart–>elastic arteries –>muscular arteries –> arterioles–> capillaries —> venous system
venous system
capillaries–>post capillary venule–>small veins –>large veins–>heart
Elastic arteries are known as
conducting arteries
muscular arteries are known as
distributing arteries
arterioles are known as
resistance vessles
capillaries
exchange vessels
small and large veins are known as
capacitance veins
largest arteries are known as
elastic arteries
the aorta is located off the
left ventricle
second largest arteries are known as
muscular arteries
the purpose of muscular arteries
to deliver blood to the body
muscular arteries are _____ in vasoconstriction
active
elastic arteries are _______ in vasoconstriction
inactive
elastic arteries act as pressure reservoirs by
expanding and recoiling as blood is filled and ejected from the heart
elastic arteries are associated with which part of BP
ventricular systole
muscular arteries work to get blood to
the head, upper and lower extremities
which are the smallest arteries
arterioles
the control system for vasomotor control (vasodialation and vasoconstriction)
autonomic system response located in the medulla oblogata
when there is sufficient oxygen in the arteries, the precapillar sphinters are
contracted
when there is insufficient oxygen in the arteries precapillaries sphincters are
relaxed
thoroughfare channel
where blood flows when precapillary sphincters are contracted – space between arterioles and venules
3 types of capillaries (3)
continuous, fenestrated, sinusoid
continous capillaries
continuous capillary formed by endothelial cells, tight junctions, commonly found in the brain
fenestrated capillaries
have medium large holes allowing for quicker transfusion of gas and substances, found where we pick up and drop off waste like the liver and kidneys
sinusoid capillaries
large holes called sinusoids, found in places of a lot of dead RBC transport like the spleen
tunica interna is made of
endothelium
tunica media is made of
smooth muscle
veins and venules have a _____ due to ______
valve - low pressure of blood
hydrostatic pressure in capillaries
pushes fluid out of capillaries
osmotic pressure in capillaries
pulls fluid into capillaries
there is more pressure inside the ____ than the ______
blood vessels than the tissue
net filtration occurs at the
arteriolar end of a capillary
NFP =
outward force
NFP in net filtration =
10mmHg
NFP in net reabsorption
-8mmhg
Net reabsorption occurs at the
venous end of a capillary
why does pressure slow in net reabsorption
due to surface area and coming in contact with arterial walls.
vasocontriction does what to resistance
increases
if resistance is doubled
the resistance is 1/16 as much
input to cardiovascular center (nerve impulses) come from
higher brain centers, proprioreceptors (monitor joint movement) and chemoreceptors (measuring blood acidity)
parasympathetic effects of cardiac output
vagus nerves (para) cardiac accelerator nerves (symp) vasomotor nerves (symp)
direct renal mechanism is mainly responsive to
higher BP
the renin-angiotensin-aldosterone mechanism kicks in when BP is
Low
pathway of renin-angiotensin- aldosterone mechanism
renin –>angiotensinogen–>angiotensin 1—>angiotensin 2
angiotensin converting enzyme comes especially from
lungs
where does the conversion of angiotensinogen to angiotensin 1 occur
in the liver
functions of angiotensin II- how it triggers an increase in BP
increases blood volume by stimulating aldosterone (vasoconstriction), causing ADH release, triggering hypothalamic thirst center.
hormone released by vasodialation
atrial nautriuretic peptide - released by heart with high BP
hormone released to increase blood volume
aldosterone, antidiuretic hormone
hormone released to decrease blood volume
atrial natriuretic peptide
