Blood Vessels Flashcards
The vascular system is made up of
the vessels that carry either blood or lymph fluid through the body: (1) blood circulatory system and (2) lymphatic circulatory system.
The blood circulatory system is composed of
blood vessels.
The blood vessels consist of
arteries (large & small), veins (large & small), and capillaries.
Blood circulates within the blood vessels to where?
throughout the body (moving from the heart to the tissues, and back to the heart).
Blood circulation delivers
oxygen and nutrients to the tissues and takes away tissue waste.
The lymph vessels carry
lymphatic fluid which is a clear, colorless fluid and made of water and blood cells.
The lymphatic system is part of what system?
the immune system
The lymphatic system (func)
helps rid the body of toxins and waste.
How does the lymphatic system fulfill its function?
It does this by filtering and draining lymph away from each region of the body.
The cardiovascular system has
five general classes of blood vessels:arteries, arterioles, capillaries, venules, and veins.
Arteries carry blood
away from the heart.
As the arteries enter ____________, they ___________, and the ___________ in diameter
peripheral tissues, they branch repeatedly, and the branches decrease in diameter.
The smallest arterial branches are called
arterioles.
From the arterioles, blood moves into
capillaries,
what happens at the capillaries
diffusion between blood and interstitial fluid takes place.
From the capillaries, blood enters
small venules,
small venules, which unite to form
larger veins that return blood to the heart.
Blood leaves the heart through
the pulmonary trunk (which originates at the right ventricle) and the aorta (which originates at the left ventricle).
The pulmonary arteries that branch from the pulmonary trunk carry blood
to the lungs.
The systemic arteries that branch from the aorta distribute
blood to all other organs.
Within these organs, the vessels branch into
several hundred million tiny arterioles that supply blood to more than 10 billion capillaries.
The walls of arteries and veins have _______ layers
3
three distinct layers of veins and arteries are (from deep to superficial)
the tunica intima, tunica media, and tunica externa (AKA adventitia).
The tunica intima is the ______ layer of a blood vessel.
inner
tunica intima includes
the endothelial lining and a surrounding layer of connective tissue with a variable number of elastic fibers.
In arteries, the outer margin of the tunica intima contains
a thick layer of elastic fibers called the internal elastic membrane.
The tunica media is the ______ layer of a blood vessel.
middle
The tunica media contains
contains concentric sheets of smooth muscle tissue in a framework of loose connective tissue.
The collagen fibers bind the tunica media to
the tunica intima and tunica externa.
The tunica media is commonly the _____________ layer of the ____________
thickest, artery
The smooth muscle cells encircle the
endothelium that lines the lumen (interior space) of the blood vessel.
The tunica media is separated from the
surrounding tunica externa by a thin band of elastic fibers called the external elastic membrane
external elastic membrane are only in
arterie
The tunica externa, or tunica adventitia, is the ___________ layer of a blood vessel.
outer
The tunica externa, is a
connective tissue sheath.
In arteries, tunica externa contains
collagen fibers with scattered bands of elastic fibers.
In veins, tunica externa is generally
thicker than the tunica media and contains networks of elastic fibers and bundles of smooth muscle cells.
The connective tissue fibers of the tunica externa typically
blend into those of adjacent tissues, stabilizing and anchoring the blood vessel.
Arteries and veins supplying the same region lie
side by side.
Arteries and veins are distinct by
1) Vessel Lumen
2) Vessel Lumen Lining
3) Vessel Walls
4) Veins
Vessel Lumen (arteries)
When not opposed by blood pressure, the elastic fibers in the arterial walls recoil ➠ lumen constriction; (1) the lumen of an artery looks smaller than that of the corresponding vein. (2) The walls of arteries are relatively thick and strong ➠ lumen circular shape.
Vessel Lumen (veins)
veins tend to collapse and appear flattened.
Vessel Lumen Lining (arteries)
The endothelial lining of an artery cannot contract, so when an artery constricts, its endothelium folds. Therefore, the sectioned arteries have a pleated (folded) appearance.
Vessel Lumen Lining (veins)
The lining of a vein lacks these folds
Vessel Walls (arteries vs veins)
In general, the walls of arteries are thicker than the walls of veins.
The tunica media of an artery contains more smooth muscle and elastic fibers than a vein does. These components help resist/absorb the pressure generated by the ventricles as they pump blood into the pulmonary trunk and aorta.
Valves (arteries vs veins)
Veins typically contain valves - internal structures that prevent the
backflow of blood toward the capillaries.
In a vein, the valve appears as a slight extension/fold of the vessel wall.
Arteries do not have valves
There are three main types of arteries:
elastic, muscular, and arterioles.
Arteries relatively thick, muscular walls RESULTS IN
arteries elastic and contractile
Elasticity allows the vessel diameter
diameter to change passively in response to changes in blood pressure ➠ allows arteries to absorb the surging pressure waves that accompany the contractions of the ventricles.
Contractility (arteries)
Arterial walls can actively change diameter. When arteries are stimulated by the nervous system, the smooth muscles within the artery wall contract ➠ constricting the artery—a process called
vasoconstriction. When these smooth muscles relax, the diameter of the lumen increases—a process called vasodilation.
vasoconstriction
the smooth muscles within the artery wall contract ➠ constricting the artery
vasodilation
When these smooth muscles relax, the diameter of the lumen increases
Vasoconstriction and vasodilation affect (3x)
[1] the afterload on the heart (i.e., the resistance of the arteries) [2] the blood pressure, and [3] capillary blood flow.
Vessel contractility is also important during
the vascular phase of hemostasis, when the contraction of a damaged vessel wall helps reduce bleeding.
In traveling from the heart to peripheral capillaries, blood
passes through
elastic arteries, muscular arteries, and arterioles.
Each type of vessel represents the midpoint in a portion of a
continuum. For example,
largest muscular arteries contain a considerable amount of elastic tissue, and the smallest resemble arterioles.
Elastic arteries carry ___________ volumes of blood away from the heart.
large
Which type of arteries are the largest
Elastic arteries
The pulmonary trunk and aorta, as well as their major branches
are (which type of artery?)
elastic arteries.
elastic arteries (structure)
The walls of elastic arteries are extremely resilient because the tunica media contains a high density of elastic fibers and relatively few smooth muscle cells.
elastic arteries (function)
elastic arteries can tolerate the pressure changes of the cardiac cycle. Their expansion cushions the sudden pressure rise during
ventricular systole, and their recoil slows the drop in pressure during ventricular diastole. In this way, elastic arteries help to make blood flow continuous.
During ventricular systole, (elastic arteries func)
pressures rise rapidly, and the elastic arteries expand as the stroke volume is ejected.
During ventricular diastole, (elastic arteries func)
blood pressure within the arterial system falls and the elastic fibers recoil to their original dimensions.
By the time blood reaches the arterioles, the pressure fluctuations
have disappeared, and blood flow is continuous.
Large Vein is located at
Superior and Inferior Venae cavae and their branches
Large Vein have a
thin tunica media and large lumen
Muscular arteries, or medium-sized arteries, distribute blood to
skeletal muscles and internal organs.
Most of the vessels of the arterial system are
muscular arteries.
muscular arteries are characterized by
a thick tunica media, which contains more smooth muscle cells than the tunica media of elastic arteries.
Medium sized vein are characterized by
thin tunica media and few smooth muscle fibers
Arterioles are considerably _______________ than muscular arteries.
smaller
Arterioles have a ____________ defined tunica externa.
poorly
In larger arterioles, the tunica media consists of ________ layers of smooth muscle cells
one or two layers of smooth muscle cells
In the smallest arterioles, the tunica media contains ________ smooth muscle cells
scattered smooth muscle cells that do not form a complete layer.
The luminal diameters of smaller muscular arteries and arterioles change in response to
local conditions or to neural or endocrine stimulation.
Changes in their luminal diameter affect
the amount of force required to push blood around the cardiovascular system: More pressure is required to push blood
through a constricted vessel than through a dilated one.
The force opposing blood flow is called resistance, so arterioles are also called
resistance vessels.
Venules (func)
collect blood from capillaries
Capillary (desc)
weave throughout all tissues, forming intricate networks that surround muscle fibers, radiate through connective tissues, and branch beneath the basement membrane of epithelia.
A typical capillary consists of
an endothelial tube inside a thin basement membrane. Neither a tunica media nor a tunica externa is present.
The two major types of capillaries are
continuous capillaries and fenestrated capillaries.
What is the third/minor type of capillary?
Sinusoids
Continuous capillaries (func)
supply most regions of the body. Continuous capillaries permit water, small solutes, and lipid-soluble substances to diffuse into the interstitial fluid.
Continuous capillaries (desc)
In a continuous capillary, the endothelium is a complete lining. A cross section through a continuous capillary cuts across several endothelial cells. In a small continuous capillary, a single endothelial cell may completely encircle the lumen.
Fenestrated (fenestra, window) capillaries (func)
rapid exchange of water and solutes between blood and interstitial fluid.
Fenestrated (fenestra, window) capillaries (desc)
contain “windows” or pores that penetrate the endothelial lining. The pores allow rapid exchange of water and solutes between blood and interstitial fluid.
Fenestrated capillaries are found along
absorptive areas of the intestinal tract and at filtration sites in the kidneys.
Sinusoids are related in structure and function to
fenestrated capillaries.
In contrast to continuous and fenestrated capillaries, sinusoidal capillaries have
a discontinuous endothelium. sinusoids commonly have gaps between adjacent endothelial cells, and the basement membrane is either thinner or absent.
Pro of sinusoids are
sinusoids allow maximally free exchange of water
and solutes, such as plasma proteins, between blood and interstitial fluid.
Blood moves through sinusoids very slowly,
maximizing the exchange across the sinusoidal walls.
Sinusoids occur in
the liver, bone marrow, spleen, and many endocrine organs. At liver sinusoids, plasma proteins secreted by liver cells enter the bloodstream.
The specialized capillaries in the central nervous system is where the
endothelial cells of the capillaries are bound together by tight junctions.
These specialized capillaries have very _____________ permeability and form the ____________________________ (BBB).
restricted, blood-brain barrier
Which type of capillary are the capillaries in the nervous system?
Continuous
What are Capillary Beds?
Capillaries function as part of an interconnected collective network called a capillary bed.
A single arteriole generally gives rise to _______________capillaries, which empty into _____________
dozen of, several venules
What surrounds the entrance of the capillary?
precapillary sphincter
What is the function of precapillary sphincter?
controls arterial blood flow to the tissues. Contraction of the smooth muscle cells of this sphincter narrows the capillary entrance, reducing or stopping the flow of blood.
When one precapillary sphincter constricts, blood is _____________
diverted into other branches of the network.
When a precapillary sphincter relaxes, _____________
the entrance dilates, and blood flows into the capillary.
The central passageway in the capillary system is called
the thoroughfare channel
What is Angiogenesis?
Angiogenesis (angio-, blood vessel + genesis, production) is the formation of new blood vessels from pre-existing vessels
What stimulates Angiogenesis?
occurs under the direction of vascular endothelial growth factor (VEGF).
When does Angiogenesis occur?
occurs during embryonic and fetal development as tissues and organs develop.
When else does Angiogenesis occur?
It may also occur at other times in any tissue in response to factors released by oxygen-
starved cells.
Why is Angiogenesis important?
Angiogenesis is important in cardiac muscle, where it occurs in response to hypoxia/ischemia due to chronically constricted or occluded vessels.
(Vascular Endothelial Growth Factor) can be utilized by which cells?
Tumor cells
How do tumor cells utilize VEGF?
To promote angiogenesis, to gain blood supply to reproduce
Veins ________blood from all _________________ and _______ to the heart.
collect, tissues and organs, return it
Why are veins thinner than arteries?
there are less smooth muscle cells in the tunica media
is the blood pressure in the veins higher or lower than in the arteries?
The blood pressure is lower in the veins than in the arteries.
How do we classify veins? And what are they?
By size:
1. Venules
2. Medium Veins
3. Large Veins
Even though their walls are thinner, in veins have __________ luminal diameters than their corresponding arteries.
larger
What do the smallest venules resemble?
expanded capillaries
Which veins are comparable in size with muscular arteries?
Medium and Large veins
Which vein has all 3 layers?
Large veins
Which system (arterial or venous) produces the most blood pressure?
Arterial
Which system has the blood pressure fall?
Venous
Why do veins require valves?
The blood pressure in venules and medium-sized veins is so low that it cannot overcome the force of gravity. Veins in the limbs contain valves, which are folds of the tunica intima projecting from the vessel wall into the lumen and pointing in the direction of blood flow.
How do venous valves function?
any movement that compresses a vein and pushes blood toward the heart. (opens the valve)
What are varicose veins?
When the walls of the veins near the valves weaken or become stretched, the valves may not close properly. Blood pools in the veins ➠ vein becomes grossly distended and swollen.
What occurs across capillary walls?
all chemical and gaseous exchange between blood and interstitial fluid occurs across capillary walls - capillary exchange.
What do cells rely on the capillary exchange to obtain and remove?
to obtain nutrients and oxygen and to remove metabolic wastes, CO2 and urea.
At what rate does capillary exchange occur? Why?
occurs rapidly, because the distances involved are very short.
Blood flow through capillaries at what rate? Why?
Blood flows through capillaries very slowly, allowing diffusion or active transport of materials across the capillary walls to occur.
Which blood vessel permits substance exchange?
Capillaries
The most important processes that move materials across capillary walls are
Diffusion, Filtration, and Reabsorption
What is diffusion?
Diffusion is the net movement of ions or molecules from an area where their concentration is higher to an area where their concentration is lower.
What is filtration?
Filtration is the separation process that separates solid matter from fluid within a mixture using a filter membrane that only the fluid can pass.
What is the reabsorption?
Reabsorption is water flowing from the tissue back to the capillary beds with dissolved waste, CO2 ,etc.
The difference between the high and low concentrations results in?
concentration gradient ➠ diffusion ➠ eliminate that gradient (concentration difference).
Diffusion occurs most rapidly when?
(1) the distances involved are short, (2) the concentration gradient is steep, and (3) the ions or molecules involved are small.
How does water diffuse through?
between endothelial cells/pores
How do ions diffuse through?
Ions (sodium, potassium, calcium, and chloride) diffuse through membrane ion channels/pores
How do Small organic molecules diffuse through?
Small organic molecules (glucose, amino acids, and urea) diffuse through pores
How does Lipids (fatty acids and steroids), and lipid-soluble substances, and soluble gases (O2 and CO2) diffuse through?
Lipids (fatty acids and steroids), lipid-soluble substances, and soluble gases (O2
and CO2) diffuse across endothelial cell membrane
Why can’t ions and small organic molecules diffuse through the membrane?
Because they are too polar
How does filtration work?
Solid particles that are oversize are stopped by one side of the membrane or “filtered out”, and the fluid that passes through is called the filtrate.
What is the driving force for filtration?
hydrostatic pressure - it pushes water from an area of higher pressure to an area of lower pressure.
What happens in capillary filtration?
water and small solutes are forced across a capillary wall, leaving larger solutes and plasma proteins remained in the capillaries
Where does filtration primarily occur?
Filtration takes place primarily at the arterial end of a capillary, where capillary hydrostatic pressure (CHP) is highest.
What is the result of capillary filtration?
less water, less pressure, so reabsorption can occur later
Why does reabsorption occur?
Reabsorption occurs as the result of osmosis.
what is osmosis?
Osmosis is the diffusion of water across a selectively permeable membrane that separates two solutions of differing solute concentrations.
Water molecules tend to diffuse toward the solution of the _____ solute concentration.
higher
The higher the solute concentration of a solution the _______ the solution’s osmotic pressure
greater
after filtration, there are a lot of large molecules and plasma proteins that are trapped in the capillary lumen as a result _____________
creates an osmotic pressure called blood colloid osmotic pressure (BCOP) ➠ drives water from interstitial fluid/tissue back to the capillaries ➠ reabsorption
What is Capillary Exchange?
Filtration & Reabsorption
_____ and ____________ function together along the
length of a typical capillary.
Filtration & Reabsorption
what is bulk flow?
The continuous movement of water out of capillaries, flowing through peripheral tissues, and then back to the bloodstream is known as bulk flow.
what cause Edema?
A disruption in the balance between filtration and reabsorption results in edema
What is edema?
An abnormal accumulation of interstitial fluid.
What is the underlying problem in edema?
The underlying problem in edema is a disturbance in the balance between hydrostatic and osmotic forces at the capillary level.
The swelling at a bruise is localized edema, which is caused?
When a capillary is damaged, plasma proteins come out of the capillary and enter the interstitial fluid. This increase the interstitial fluid colloid osmotic pressure (ICOP) ➠ water retention, reduced reabsorption ➠ localized edema.
In the U.S., most serious cases of edema result
from?
increases in arterial blood pressure, venous pressure, or total circulatory pressure ➠ increase in capillary hydrostatic pressure (CHP) ➠ accelerates fluid movement into the tissues.
Homeostatic mechanisms regulate cardiovascular activity to ensure that
the amount of blood flow through tissues, called tissue perfusion, is adequate to meet the demand for oxygen and nutrients.
Factors that affect tissue perfusion are (3x)
(1) cardiac output, (2) peripheral resistance, and (3) blood pressure.
When a group of cells/tissue becomes active, blood supply to that region must __________ to bring the necessary oxygen and nutrients, and to carry away the wastes and carbon dioxide they generate.
increase
Homeostatic regulation must ensure that blood flow changes occur (3x)
(1) at the right time, (2) in the right area, and (3) without drastically changing blood pressure and blood flow to vital organs (brain, heart, and lungs).
Autoregulation employs local factors to change
the pattern of blood flow within capillary beds.
An example of autoregulation at the tissue level is
precapillary sphincters open and close in response to chemical changes in interstitial fluids.
Autoregulation causes immediate, localized adjustments to
meet the demands and maintain tissue homeostasis.
If autoregulation fails to normalize conditions at the tissue level,
central regulation, involving both neural and endocrine mechanisms, is activated.
These central regulation mechanisms focus on controlling cardiac output and blood pressure to
restore adequate blood flow after blood pressure decreases.
Neural mechanisms respond to changes in ____________________ sensed at specific sites.
arterial pressure or blood gas levels
When these changes occur, the cardiovascular center of the autonomic nervous system makes short- term adjustments to
cardiac output and peripheral resistance to maintain blood pressure and ensure adequate blood flow.
Endocrine Mechanisms
The endocrine system releases hormones to enhance short-term adjustments and to direct long-term changes in cardiovascular performance.
