chapter 18 blood vessels
The microcirculation occurs in two types of vessels:
1. The true capillaries, where materials are exchanged 2. A small, central vessel.
in The sympathetic nervous system, axons release the neurotransmitters norepinephrine and epinephrine on cardiac muscle cells and the smooth muscle cells of blood vessels, to produce two immediate changes:
1. an increase in heart rate and contractility, which increases cardiac output; and 2. vasoconstriction of all types of vessels, but especially arterioles, which increases peripheral resistance. both increase blood pressure
Systolic pressure, which averages about
120 mm Hg at rest
Diastolic pressure, which averages about
80 mm Hg at rest
What is blood pressure
Blood pressure is the outward force that the blood exerts on the walls of the blood vessels.
Resistance is mainly determined by three variables:
Blood vessel radius, blood viscosity, and blood vessel length.
what is cardiac output
Cardiac output (CO) is the product of stroke volume (the amount of blood pumped with each beat) times heart rate (the number of beat per minute).
What are the three mechanisms of capillary exchange
Diffusion and osmosis through gaps and fenestrations Diffusion through the membranes of endothelial cells Transcytosis
whats the treatment for hypertension
Drug therapy, lifestyle modification (no smoking, increased physical activity).
muscular arteries are mostly smooth muscle cells. what is the effect of this
Due to the predominance of smooth muscle cells, the diameter of muscular arteries does change significantly with vasoconstriction and vasodilation. These vessels are the ones most likely to become blocked.
why is Endothelium important in the tunica intima
Endothelial cells provide a smooth surface over which blood can flow with a minimum of friction and turbulence. Endothelial cells also produce many chemicals and proteins, such as Nitric oxide, collagen, and clotting factors.
Tissue Perfusion in Special Circuits- you need to go back and read this
I love you so much and I believe in you so much. This test will be nothing for you
The smallest arterioles are _______, they directly feed _________ in most tissues
Metarterioles,capillary beds
what are the differences between arteries and veins
Most arteries have much thicker tunica media than do veins, which reflects the arteries' role in controlling blood pressure and blood flow to organs. The internal and external elastic laminae are much more extensive in arteries than in veins, which reflects the fact that arteries are under much higher pressure than veins. Veins typically outnumber arteries and their lumens have a larger diameter
The reason for the thinness of the capillary wall can be traced back to capillaries' primary function:
Nutrients, gases, ions, and wastes must be able to cross the wall and travel between the blood in the capillary and the tissue cells OR CAPILLARY EXCHANGE
which cells control blood flow through the capillary
Pericytes
The three main factors that influence blood pressure are
Resistance, cardiac output, and blood volume.
what are the weblike patterns, sometimes visible in pale skin
Smaller veins are often so interconnected by collaterals that they form complex, weblike patterns that are sometimes visible beneath the skin, particularly in individuals with pale skin.
a layer of elastic fibers called the Internal elastic Lamina is important how
The elastic fibers give the vessel the ability to stretch when subjected to increase pressure and the ability to recoil back to original size.
what are two factors that affect blood flow
The magnitude of the blood pressure gradient Resistance, which is defined as any impedance to blood flow.
what are the two divisions of ANS that affect blood pressure
The sympathetic and parasympathetic nervous systems.
which division of ANS is the flight or fight response division
The sympathetic nervous system
what are the tunica media of the elastic arteries like
The tunica media of these arteries contain 40-70 sheets of elastic fibers arranged between the thin layers of smooth muscle cells.
what advantage do Fenestrated capillaries have
These pores allow diffusion to take place much more quickly than it does in continuous capillaries, and fenestrated capillaries are therefore located in places where substances must rapidly enter or exit the blood.
describe structure of Sinusoidal Capillaries
They have a discontinuous sheet of endothelium, an irregular basal lamina, and very large pores in their endothelial cells. larger in diameter irregular shape bc dependent on shape of organ they reside
what do the vasa vasora do
They supply oxygen and nutrients to the outer layer of the larger blood vessels, whose cells are too far away from the lumen to receive oxygen and nutrients by diffusion alone.
why is the structure of the tiny post capillary venules important
This structure enables them to exchange material with the surrounding interstitial fluid in much the same way that materials are exchanged in capillaries.
True capillaries are drained at the distal end of the capillary bed by a portion of the central vessel called a
Thoroughfare channel
why is tissue perfusion important
Tissue perfusion is largely a function of arterial blood pressure-if the arterial pressure is too low, blood will not be adequately delivered to the tissues and they will be poorly perfused.
what can affect the diameter of arterioles;
Vasomotor nerves and hormones in the blood
The smallest veins are the _____ which drain from the ______-
Venules, capillary beds
what is vasodilation
When sympathetic stimulation of the smooth muscle cells decreases these cells relax and the vessel diameter increases.
if the blood pressure is 40 mm Hg, the pressure in the blood vessel is equal to that generated by _______
a column of mercury 40 mm in height
what are the two components of the tunica media
a layer of smooth muscle cells arranged in a circular manner around the lumen, and another layer of elastic fibers called the External elastic Lamina.
Osmosis involves the movement of water from
a solution with a lower solute concentration to one with a higher solute concentration. Another way to explain osmosis is to say that the solute particles in a solution exert a force, or "pull," on water molecules.
The total volume of blood is directly linked to
amount of water
what is Arteriovenous anastomosis
an artery empties directly into a vein without passing through a capillary bed.
The pressure is highest in the ___
aorta and elastic arteries
What are the five types of blood vessels
arteries, arterioles, capillaries, venules, veins
The myogenic mechanism counters a change in blood flow by altering
arteriolar resistance which inversely affects blood flow
what are the smallest arteries
arterioles
Tissue perfusion is also regulated by local factors within each individual tissue, a phenomenon known
autoregulation
New arterial anastomoses can be formed when
blood flow through an artery is insufficient to meet the tissue's metabolic needs.
where are capillary beds not found
cartilage, the sclera and cornea of the eye, and epithelial tissue.
metabolic controls is mediated by
chemicals present in the interstitial fluid surrounding capillaries
what are the elastic arteries also called
conducting arteries
The majority of capillaries are this type
continuous capillaries
hypertension is associated with
coronary artery disease, stroke, heart failure, certain types of dementia, kidney disease, and vascular disease.
read over page 678 please
curious george
as resistance increases, blood flow ____
decreases
hydrostatic pressure in a capillary changes as we move from its arteriolar end decreases or increases ?
decreases
blood viscosity can be altered by _____
dehydration
Arteries in the pulmonary circuit carry what kind of blood
deoxygenated
In the systemic Circuit, veins transport
deoxygenated blood
what do the smooth muscles control in the tunica media
diameter of the blood vessel and so the amount of blood that flows to organs.
muscular arteries are also called
distributing arteries
the largest diameter arteries are the
elastic arteries
Blood pressure is ____ to hydrostatic pressure.
equal
which hypertension is more common
essential or primary
where are Baroreceptors found and what are they
found in the aorta, as well as in the common carotid artery located in the neck. pressure receptors
_________ are quickly exchanged between tissue cells and the blood through the capillary walls, many of which are only single cell thick.
gases , nutrients, wastes, and other molecules
The longer the blood vessel, the ____ resistance
greater
blood has a low or high viscosity and why
high because of the number of proteins and cells it contains
Hypertension means
high blood pressure
which directions do hydrostatic pressure and osmostic pressure go
hydrostatic goes out of capillary osmotic goes into capillary
There are two basic pressures that drive water movement at work within a capillary:
hydrostatic pressure and osmotic pressure.
explain The Urinary system's control over blood volume
if blood pressure increases, more water flows through the tiny filtering tubes of the kidney, called tubules, than these cells can return to the blood. This water is then lost from the body as urine, and blood volume and blood pressure decrease. \and conversely
Arterial anastomoses exist where
in many organs such as the heart and the brain
AS blood volume increases, blood pressure _____
increases
As peripheral resistance increases, blood pressure _______
increases
When the blood contains more water, blood volume _____
increases
blood flow increases when the pressure gradient _____
increases
Resistance varies _____ with the vessels radius
inversely
Secondary hypertension
is when cause is identifiable
The tiny Postcapillary venules consist of
little more than endothelium and some surrounding connective tissue.
what are Anastomoses
locations where vessels connect via pathways called collateral vessels.
Go over types of blood vessels
love Sovanny
The flow of blood that take place within the body's capillary beds is collectively called
microcirculation
continuous capillaries are located where
muscles, skin, and most nervous and connective tissue.
whats a common cause of secondary hypertension
narrowing of the arteries serving the kidneys.
what is Vasoconstriction
nerves stimulate the smooth muscle cells to contract, an action knowns as Vasoconstriction, which narrows the diameters of the vessel.
essential (or primary ) hypertension is when
no cause is identifiable
whats another factor that can influence peripheral resistance
obstructions within the blood vessels. Obstructions in the vessel, such as tumors, the fatty plaques seen with atherosclerosis, or blood clots, affect the way in which blood flows through the vessel.
arteries of the systemic circuit carry what kind of blood
oxygenated
In the pulmonary circuit, veins transport
oxygenated blood
the smooth muscle cells of metarterioles are confined mostly to a circular _____ that encircles the metarteriole capillary junction.
precapillary sphincter
because the elastic arteries are closest to the heart, the undergo the most ____
pressure
The myogenic mechanism relies on
properties inherent in the vascular smooth muscle cells in the arterioles supply capillary bed.
The difference between the systolic and diastolic pressures- about 40 mm Hg- is known as the
pulse pressure
blood vessel radius is ____ to change while vessel length is _______
quickest, slowest
pressure gradient _____ during ventricular systole and ______ during ventricular diastole.
rises, declines
what surrounds the lumen
several tissue layers, or tunics
The endocrine system is somewhat _____ than the nervous system in responding to changes in blood pressure
slower
The axons of the parasympathetic system, via the vagus nerve, release acetylcholine primarily onto certain cardiac pacemaker cells and atrial cardiac muscle cells. what does this do?
slows the heart rate, which decreases cardiac output and so blood pressure.
what are fenestrations
small pores within their endothelial cells (capillaries)
what is compliance
the ability of the vessels to stretch
The MAP is ____________
the black line on the graph which shows the mean arterial pressure. THis is the average pressure in the systemic arteries during a entire cardiac cycle.
Blood Viscosity is
the inherent resistance that all liquids have to flow. The more viscous a liquid is , the more its molecules resist being put into motion and staying in motion.
There are two types of autoregulatory :
the myogenic mechanism and metabolic controls.
Short-term control of blood pressure, such as that needed when you stand up from a sitting position, is primarily accomplished by
the nervous system and certain hormones of the endocrine system.
what is blood flow
the volume of blood that flows per minute`
why do continuous capillaries permit the fewest substances to enter or exit by para-cellular
their endothelial cells are joined together by tight junctions. majority of substances move into or out of the capillaries by diffusion through the endothelial cells or by transcytosis.
The blood flow to a tissue through a capillary bed is known as
tissue perfusion
Peripheral resistance is increased by conditions that increase blood viscosity and is decreased by conditions that decrease blood viscosity. true or false
true
what is the outermost layer of the blood vessels
tunica externa
The innermost layer of blood vessel is
tunica intima
the middle layer of the blood vessel is
tunica media
what are the tiny vessels that supply the tunica media and tunica externa
vasa vasora
arteries are the distribution of the
vasculature
______ are the most compliant vessels
veins
many veins contain _____ valves
venous
The most common type of anastomosis is
venous anastomosis, in which neighboring veins are connected by small collaterals
what happens when blood pressure rises
when the veins cannot stretch further to the accommodate additional increases in blood volume, the extra blood shifts to the arteries. Arteries are much less compliant vessels, and when blood volume increases in arteries, overall blood pressure rises.
