Chapter 19 Blood vessels Flashcards
what is a lumen?
hollow space at center of blood vessel
what are the three main layers of most blood vessels?
Tunica intima
tunica media
tunica externa
what is the tunica intima made of?
endothelium made of simple squamous cells
and if vessel is larger than 1mm, subendothelial layer made of loose connective tissue
what is the function of tunica intima?
reduce friction with blood flow
what two things are the tunica media made of?
circular smooth muscle and elastic fibers
In which vessel is the tunica media thicker in, arteries or veins?
arteries
which is the tunica media more rigid and which is it more collapsible?
rigid in arteries
collapsible in veins
what is the function of the tunica media?
vasoconstriction and vasodilation in order to regulate blood pressure
what is the tunica externa made of?
connective tissue
what is the function of the tunica externa?
support and protect
what is the tunica externa made of?
mostly stiff collagen fibers
but some elastic fibers found in larger vessels in order to stretch and receive more blood
what is the vasa vasorum?
small blood vessels that feed larger blood vessels
where can vasa vasorum be found?
large blood vessels within the tunica externa
these characteristics belong to which layer of the blood vessel wall?
false; the tunica media is made of smooth muscle cells
tunica intima
what is the appearance difference between arteries and veins?
arteries have a smaller diameter, thicker-walled vessels
while veins have a larger diameter, thinner-walled vessels
which of the three types of arteries have the largest lumen diameter? what is it?
elastic arteries; 1.5 cm
what is the main function of elastic arteries?
great for stretching ; not meant for vasoconstriction
what characteristic makes elastic arteries stretchy?
they are filled with elastic fibers in all tunicas
where can elastic arteries commonly be found? why?
usually near heart; in order to receive blood and conduct it to major body regions
what is the diameter size of muscular arteries?
6 mm
why is the diameter size of muscular arteries so small?
they have the thickest tunica media
what is the function of muscular arteries?
deliver blood to specific body organs
perform most vasoconstriction/dilation
what is another name for elastic arteries?
conducting arteries
what is another name for muscular arteries?
distributing arteries
what is the lumen diameter of arterioles?
37 micrometers
what are arterioles made of?
mostly smooth muscle
what is the function of arterioles?
feed capillary beds
control minute-to-minute blood flow
vasoconstriction/dilation
describe how the structure of conducting arteries play a role in their function
have larger lumen - to allow more blood flow
have elastic fibers - to be stretchy/ to allow more blood flow
attached to heart - to conduct blood to various body regions
describe how the structure of muscular arteries play a role in their function
contain mostly smooth muscle - to allow for vasoconstriction/dilation
describe how the structure of arterioles play a role in their function
smallest of arteries - to allow for more precise control of vasoconstriction/dilation (which helps with temporarily cutting off blood flow to unnecessary regions)
- arterioles
- muscular arteries
- elastic arteries
- veins
false; elastic arteries is the correct answer
false; capillaries are their own separate category of blood vessel
what is the structure of capillaries?
wall is made only of tunica intima
single layer of endothelial cells and a basement membrane
their lumen is 8-10 micrometers (size of one RBC)
what is the function of capillaries?
site of fluid and nutrient exchange
what are the classifications of capillaries from least porous to most?
continuous
fenestrated
sinusoidal
what physical characteristics do continuous capillaries have?
intercellular clefts (formed by incomplete tight junctions)
pericytes (nonfunctioning tunica media/serves only to provide stabilization of cell wall and filter solutes)
does continuous capillaries have an abundance or limited flow of fluids/solutes between cell wall?
limited
how are some solutes able to leave/enter continuous capillaries?
pinocytosis
where can you commonly find continuous capillaries?
skin and muscles
What are physical characteristics of fenestrated capillaries?
intercellular clefts
pores (fenestrations)
covered by a thin basement membrane
does fenestrated capillaries have an abundance or limited flow of fluids/solutes between cell wall?
has more fluid/solute exchange than continuous capillaries but less than sinusoidal capillaries
where can fenestrated capillaries be found?
small intestine
kidneys
most endocrine glands
what are physical characteristics of sinusoidal capillaries?
endothelial cells have larger fenestrations (pores)
larger intercellular clefts
where can the sinusoidal capillaries be found?
liver
bone marrow
spleen
adrenal medulla
what is the important function sinusoidal capillaries provide besides allowing more solutes/fluid to pass through its membrane?
immune function
the large pores and large clefts cause turbulent blood flow which reduces flow speed. Reduced flow speed gives phagocytic cells found within the intercellular clefts more time to eat bacteria in the blood
The characteristics below apply to which type(s) of capillaries?
which type of capillary is most commonly found?
continuous capillaries because they are found all over skin and muscle
Unlike arteries and veins, capillaries can switch between being open and closed off of blood supply. Explain how this process occurs
arterioles that branch off arteries, can vasoconstrict to cut off blood supply to capillary bed
what is the function of the vascular shunt within certain capillary beds?
purpose is not to drop off any nutrients or waste, but just used as a shortcut for blood to flow from arteries to veins
what structure makes the vascular shunt within capillaries possible? How so?
precapillary sphincters;
closed = blood only flows through vascular shunt
open = blood flows through bed
false; sinusoidal capillaries are too leaky and would be dangerous to be found in the brain
which veins carry deoxygenated blood?
systemic veins
which veins carry oxygenated blood?
pulmonary veins
how are veins the lowest pressure vessels?
their large lumens & capillary beds dissipate most of the arterial blood pressure
at any given time, what percentage of blood volume is found in veins?
65%
one of the layers in veins is underdeveloped while the other is very thick, which is which?
tunica media is underdeveloped
tunica externa is thickest of its layers
what are the subtypes of veins?
veins
venules (microscopic)
where would you find venules?
at the point where capillaries within capillary beds unite
describe postcapillary venules
structurally similar to capillaries
only made of endothelium
immune cells can pass in and out easily
describe larger venules, like what are they composed of?
thin tunica media and externa
veins form at what point?
when venules merge
what are veins’ valves made of?
folded flaps of tunica intima
how do vein valves help blood flow in one direction?
when blood flows in the opposite direction, the flaps of the valves fill with blood and force them closed
describe what is physically happening within varicose veins
caused by incompetent venous valves
allows blood backflow to occur
allows blood to pool and swell vessels
What two things make having varicose veins more common?
being on feet for long periods
increased venous pressure
what can cause varicose veins in the anal sphincter? what is this called?
hemorrhoids; can be caused by straining when defecating
examples include:
what are vascular anastomoses?
locations where two vessels converge creating more than one pathway for blood to reach/leave tissues
why are vascular anastomoses important?
if one path is blocked, tissue will still be served via another route
where are arterial anastomoses important?
it protects vital organs from being deprived of blood if you are injured and one route of blood supply is cut off
where are arterial anastomoses most common?
joints
brain
heart
most abdominal organs
where are arterial anastomoses least common to be found in?
kidneys
spleen
retina
what are venous anastomoses
alternating pathways between veins (visible on back of hand)
The volume of blood flowing through a particular vessel per unit time is equal to what in the systemic circuit?
systemically, blood flow = cardiac output
what is the equation for cardiac output?
CO = SV x HR
(stroke volume x heart rate)
true/false; systemic blood flow is constant in a resting body?
true
what exactly does blood pressure describe?
the force exerted on a vessel wall
what is the units of measure for blood pressure?
mmHg
what is resistance of blood flow? what is the letter than indicates resistance?
( R ) = opposition to blood flow caused by friction of RBCs hitting wall
what is the equation for resistance? the un-shortened word for each acronym?
what is blood viscosity?
“mu”; the natural resistance blood has of flowing (due to formed elements)
is blood viscosity constant or not?
in healthy people it is
how does vessel length relate to resistance?
longer vessels have more surface area for resistance to occur
longer vessel = higher resistance
is vessel length constant or not?
in health people it is
how does the vessel radius relate to resistance?
larger vessel radius means more blood is able to freely flow without touching the wall of vessel = less resistance
which factors most affects the value of resistance? why?
radius; because its value is measured to the 4th power (increasing its value 4x)
what does directly proportional mean?
if one variable increases, the other will increase
what does indirectly proportional mean?
if one variable increases, the other will decrease
Your grade is _________ proportional to the amount of studying time you have for exams
directly; higher grades = more time spent studying
Your grade is __________ proportional to the amount of nervousness you are
indirectly; more anxious = lower grade
write equation for Blood flow (F) that is directly proportional to the change in blood pressure (delta P)
write equation for Blood flow (F) that is indirectly proportional to resistance (R)
why do arteries not require valves?
because of the high pressure of blood flow
Write the equation for blood flow and the equation for resistance
what is the definition of artherosclerosis?
narrowing of the arteries
explain the entire process of how exactly atherosclerosis effect the arteries?
an injury to the endothelial lining causes a tear. Cholesterol and fats within the blood stream attract to the tear site and stick within it. Macrophages then try to consume the fats but are unable to digest them. This results in “foam cells” which are lipid filled, non-functioning macrophage cells. numerous foam cells form a fatty streak. The fatty streak gets healed over by tunica media and intima. This creates a fibrous plaque which shrinks the lumen size of the artery = lessens blood flow
where does atherosclerosis occur?
under the tunica intima
after the initial plaque has formed in atherosclerosis, what then occurs?
cells deep to the plaque die and are replaced by non-elastic scar tissue = stiff walls = increased pressure
What are the types of treatment for atherosclerosis?
anti-inflammatory drugs - prevent recruitment of immune cells
aspirin - prevents platelets from initiating thrombus formation
coronary bypass surgery - cut out affected arteries
angioplasty - increases lumen diameter by smashing down fatty deposits
stent - increases lumen diameter by holding vessel open
Of the two options involving increasing the size of the artery (for treating atherosclerosis), which is most commonly used and which is not?
angioplasty - is not commonly used because its typically a temporary fix
stents are more commonly used because they are more permanent
what is the definition of blood pressure?
the FORCE exerted on vessel walls
where is blood pressure most significant? least?
closest to the heart;
vena cava
why does blood pressure decrease as arteries branch?
there is more space for blood to fill
why does blood always flow towards capillaries without much need for help
liquid always moves high to low pressure
what is the normal blood pressure for a healthy person? (systole/ diastole)
what are the factors that contribute to blood pressure?
Cardiac output
resistance
between what two types of vessels would the largest drop in blood pressure occur in?
arteries to arterioles
what is the normal range of blood pressure within capillaries?
20 to 40 mm Hg
what happens if blood pressure in capillaries was too high/low?
rupture of these very thin vessels would occur
plasma (fluid) would excessively leave the intercellular clefts
what is the range of venus blood pressure?
20 mm Hg -> to near close to 0
even though venus blood pressure is so low, how does blood not flow backwards when on its way up to the heart through veins?
valves keep blood from moving backwards
respiratory and muscular pumps squeeze vessels
what does the acronym MAP stand for/mean?
mean arterial pressure - another word for delta P when in reference to systemically
what is the formula for finding MAP?
MAP = CO x R
what are the three basic ways the body works to maintain constant MAP?
neural controls
chemical controls
renal controls
how do neural controls generally act?
primarily by changing vessel diameter
what are baroreceptors? what do they initiate? How?
baro- : pressure
receptors
NERVE cells that monitor pressure and initiate VASODILATION when blood pressure is high by activating parasympathetic and inhibiting sympathetic
where can you find baroreceptors?
carotid sinuses
aortic arch
what are chemoreceptors?
an example of afferent sensors: NERVE cells located near baroreceptors that activate to increase cardiac output and VASOCONSTRICTION when oxygen content or pH is low
what is an example of efferent control within the neural controls for maintaining constant MAP?
vasomotor center
what type of neurons are involved in, and where does the vasomotor center work?
sympathetic neurons in the medulla oblongata
how does the vasomotor center work?
releases norepinephrine to cause vasoconstriction (primarily in arterioles)
what is vasomotor tone?
steady, constant signal to produce constant state of slight vasoconstriction
what are the examples of chemical controls to maintain MAP?
epinephrine/norepinephrine
antidiuretic hormone (ADH)
aldosterone
atrial natriuretic peptide
endothelin
nitric oxide
what secretes epinephrine and norepinephrine?
adrenal medulla
what does epinephrine cause to happen?
increases cardiac output and vasoconstriction
what does norepinephrine cause to happen?
increases resistance by vasoconstriction
where is antidiuretic hormone secreted?
posterior pituitary gland
when is antidiuretic hormone released?
in response to low bp or high blood osmolarity
how does antidiuretic hormone work?
tells kidney to make less urine. Less urine output = more fluid retention which increases blood pressure
also works as a vasoconstrictor
where is aldosterone secreted?
adrenal gland
how does aldosterone work?
tells kidneys to increase salt retention which = water retention = increases blood volume = increases blood pressure
where is atrial natriuretic peptide secreted? when?
by cell walls of the atria in response when bp is high
how does atrial natriuretic peptide work?
inhibits aldosterone = excretion of sodium = excretion of water = decrease blood pressure and blood volume
also causes vasodilation
where is endothelin excreted?
endothelial cells
how does endothelin work?
is released in response to ADH and Angiotensin II + more
communicates with tunica media to vasoconstrict in order to increase blood pressure
what does the overproduction of endothelin lead to?
pulmonary arterial hypertension
where is nitric oxide secreted?
released by endothelial cells
how does nitric oxide work?
little bit is always being secreted in blood vessels in order to be the major form of vasodilation
which are the chemical signals that contribute to raising blood pressure vs lowering it?
how are renal controls different than neural or chemical controls in order to maintain MAP?
they are slower and more long-term adjustments instead of fast
they also work specifically to adjust blood volume?
what is an example of indirect renal control vs direct renal control?
explain the long process of Renin-angiotensin hormone cascade
when blood pressure drops, Renin is released by the kidneys. Angiotensinogen is found abundantly in the blood. Renin breaks down angiotensinogen into angiotensin I. Blood then travels to the lungs where ACE converts angiotensin I to angiotensin II. Angiotensin II causes the release of ADH and aldosterone. Both these hormones initial water retention which increase blood pressure. Angiotensin II also causes to be thirsty and vasoconstriction.
How does urine formation directly effect the blood pressure?
high blood pressure causes more urine production =low blood volume = low bp = less urine = high blood volume = high blood pressure
How do we know someone has hypotension?
systolic pressure is less than 100 mm HG
(healthy is 120)
what is the danger of hypotension?
inadequate delivery of blood to vital organs
what are the causes of hypotension?
poor nutrition (causing low RBC)
sow sympathetic nervous system (age or disease)
pregnancy (blood needs to serve more tissues as the body is making baby)
how do you know if someone has hypertension?
have a bp of 140 mm Hg or greater
what is the danger of hypertension?
heart works harder
blood vessels could rupture (creating atherosclerosis)
what are the common causes for hypertension?
obesity
high stress
smoking
old age
heredity
what are the three types of circulatory shock?
hypovolemic
vascular
cardiogenic
what is circulatory shock?
any condition resulting in inadequate filling of blood vessels
what is hypovolemic shock?
hypo-: insufficient
-volemic: volume of blood
major blood volume loss
what is hypovolemic shock caused by?
hemorrhage
severe vomiting
diarrhea
extensive burns
what does the body do to try to counteract hypovolemic shock? what does this produce?
heart rate increases to compensate for lack of cardiac output
pulse is WEAK but rapid
what is vascular shock?
extreme case of vasodilation = dramatic drop in bp
what are common causes of vascular shock?
anaphylactic shock
neurogenic shock
septic shock
viagra overdose
how does anaphylactic shock = vascular shock?
autoimmune response causing all blood vessels to dilate throughout the body = low bp
how does neurogenic shock = vascular shock?
neurogenic shock creates an inactive sympathetic nervous system = low bp
how does spetic shock = vascular shock?
bacterial products IN BLOOD = low bp
how does viagra overdose = vascular shock?
makes ALL vessels vasodilate, not just the ones in penis = low bp
what is cardiogenic shock?
heart is unable to deliver an adequate blood supply = cardiac output decreases
what is cardiogenic shock caused by?
heart failure due to myocardial infarction or heart block
vascular shock
what does the term perfusion mean?
the delivery of blood to tissues and organs
what is the goal of the two ways our bodies autoregulate perfusion?
keeps the blood flow constant
what are the two ways our bodies regulate perfusion?
myogenic autoregulation
metabolic regulation
how does myogenic autoregulation work?
smooth muscle in tunica media of arterioles resists changes in diameter.
Automatic vasoconstriction when expansion (increased pressure) of the vessel occurs.
automatic vasodilation when blood pressure lessens through vessel
how does metabolic regulation work?
accumulation of local waste (such as abundance of CO2) causes an increase of blood flow
in order to do this, vasodilation occurs and relaxation of precapillary sphincters occurs in order to increase blood flow and wash away waste products
what are some metabolic waste examples that would cash metabolic regulation to initiate action?
- accumulation of CO2, Hydrogen, potassium, lactic acid, adenosine, or nitric oxide
- decrease in O2
for autoregulation of perfusion to occur, which nervous system is used?
no neural input is used, just happens automatically
where does the pituitary gland rest?
within a hollowed out area of the sphenoid bone called the sella turcica.
