Chapter 5B Flashcards
The 5 main types of blood vessels are arteries, A, capillaries, B, and veins.
A arterioles
B venules
- Arteries carry blood away from the X to other organs. Large, elastic arteries leave the
X and divide into medium-sized, muscular arteries that branch out into the various
regions of the body
heart
heart
Medium-sized arteries then divide into small arteries, which in turn divide into still
smaller arteries called X
arterioles
As the arterioles enter a tissue, they branch into numerous tiny vessels called X
capillaries
The thin walls of capillaries allow the exchange of substances between the blood and
body tissues. Groups of capillaries within a tissue re-unite to form small veins called
X. These in turn merge to form progressively larger blood vessels called veins.
venules
X are the blood vessels that convey blood from the tissues back to the heart
Veins
The wall of a blood vessel consists of three structural layers or tunics:
- Tunica X or intima: epithelial inner lining
- Tunica B: middle layer consisting of smooth muscle and elastic connective tissue
- Tunica C or adventitia: connective tissue outer covering
X interna
B media
C externa
…. membrane (collagen fibers) and an ….. elastic …. (elastic fibers)
separates tunica interna and media.
Basement
internal elastic lamina
Interna: forms the inner lining of a blood vessel and is in direct contact with the blood as it
flows through the lumen. It is a thin layer of flattened cells that lines the inner surface of the
entire cardiovascular system: X
endothelium.
Media: is a muscular and connective tissue layer that displays the greatest variation among the
different vessel types.
Primary role of the smooth muscle cells (SMCs) is to regulate thediameter of the lumen:
SMCs contraction narrows lumen diameter: A
SMCs relaxation increases lumen diameter: B
A vasoconstriction
B vasodilation
Externa: consists of elastic and X fibers. It contains numerous nerves and, especially in
larger vessels, tiny blood vessels that supply the tissue of the vessel wall (vasa vasorum). It also
helps anchor the vessels to surrounding tissues.
collagen
Unlike arteries, veins contain X that ensure blood flows in only one
direction (arteries don’t require valves because pressure from the heart is so
strong that blood is only able to flow in one direction).
valves
True/false: the capillaries are composed of a layer of only two endothelial cells and a basement membrane.
false, single layer of endothelial cells +basement membr
True/false: capillaries lack both a tunica media and a tunica externa
true
Precapillary sphincters regulate the flow of blood through capillary X: when the
precapillary sphincters are relaxed (open), blood flows into the capillaries, when contract
(close or partially close), blood flow through the capillaries ceases or decreases.
beds
Typically, blood flows intermittently through capillaries due to:
- vasomotion: what is this?
- and the precapillary sphincters
alternating contraction and relaxation of the smooth muscle of metarterioles
The body contains three different types of capillaries:
Continuous capillaries
Fenestrated capillaries
Sinusoids capillaries
explain
continous: with a continuous plasma membrane (only interrupted by clefts)
Fenestrated: plasma membrane has many fenestrations (small pores)
Sinusoid: are wider than other capillaries: more fenestrations and clefts
Substances enter and leave capillaries by three basic mechanisms:
- X
- Transcytosis
- Bulk flow
Simple diffusion
Simple diffusion: most important method for solute exchange. It is the
mechanism for many substances: X, CO2, glucose, amino acids, and hormones
O2
Transcytosis: substances in blood plasma become enclosed within tiny pinocytic
X and enter the endothelial cell from the lumen side and exit on the
other side by exocytosis. Mechanims for large, lipid-insoluble molecules
vesicles
Bulk flow: large numbers of ions, molecules, or particles in a fluid move
together in the same direction occurs from an area of higher/lower pressure to an
area of higher/lower pressure, and it continues as long as a pressure difference exists.
higher to lower
Bulk flow is important for regulation of the relative volumes of blood and
interstitial fluid.
- Pressure-driven movement of fluid and solutes from blood capillaries into
interstitial fluid is called filtration. - Pressure-driven movement from interstitial fluid into blood capillaries is
called ….
reabsorption
Blood hydrostatic pressure (BHP): the pressure generated by the pumping action of
the heart “pushes” fluid out of capillaries into interstitial fluid: promotes
filtration/reabsorption.
filtration
Blood colloid osmotic pressure (BCOP): is a force caused by the colloidal suspension
of large proteins. The effect of BCOP is to “pull” fluid from interstitial
spaces into capillaries: promote filtration/reabsorption.
reabsorption
The balance of the Blood hydrostatic pressure (BHP) and the Blood colloid osmotic pressure (BCOP)is called the …. (NFP). This determines
whether the volumes of blood and interstitial fluid remain steady or change.
net filtration pressure
Starling’s law of the capillaries = the volume of fluid and solutes reabsorbed normally is exactly as large as the volume filtered (equilibrium)
true/false
false: the volume of fluid and solutes reabsorbed normally is almost as large as the
volume filtered. Its a near equilibrium
At the arterial end of a capillary, there is a
net inward/outward pressure and
fluid moves in/out of the capillary into
interstitial spaces (filtration).
outward, out
At the venous end of a capillary, there is a net
inward/outward pressure, and fluid moves in/out of the
capillary from tissue spaces (reabsorption)
inward, in
On average, about 85% of the fluid filtered out of capillaries is reabsorbed. (!)
- The excess filtered fluid and the few plasma proteins that do escape from blood into
interstitial fluid enter ….. capillaries.
lymphatic
If filtration greatly excedes reabsorption, the result is X: an abnormal increase
in interstitial fluid volumen.
edema
As lymph drains into the junction
of the jugular and subclavian veins
in the upper thorax, these
materials return to the blood.
ok
Total blood flow is the same as…… : the volume of blood that circulates through
blood vessels each minute.
cardiac output (CO)
Hemodynamics refers to the X involved in circulating blood throughout the body
forces
How the cardiac output becomes distributed into circulatory routes depends on two
more factors:
- the X difference that drives the blood flow through a tissue (high to low, the greater the difference, the greater the flow)
- the resistance to blood flow in specific blood vessels (the higher the resistence, the smaller the blood flow)
pressure
Vascular resistance is the opposition to blood flow due to friction between blood and
the walls of blood vessels.
Vascular resistance depends on:
- Blood viscosity
- Total blood vessel length
- Size of the blood vessel lumen
(vessel radius)
which is the main
determinant of resistance? (!)
- size of the blood vessel lumen
Contraction of the X generates blood pressure
ventricles
true/false
- BP rises and falls with each heartbeat in blood vessels leading to capillaries
true
true/false
BP is lowest in the aorta and large systemic arteries.
false, highest
As blood leaves the aorta and flows through the systemic circulation, its pressure falls
progressively as the distance from the left ventricle increases.
true/false
true
- Systolic blood pressure (SBP): lowest/highest pressure attained in arteries during systole.
- Diastolic blood pressure (DBP): lowest/highest arterial pressure during diastole
Blood pressure is measured with a sphygmomanometer.
highest,
lowest
BP is mainly determined by cardiac output, X, and vascular resistance
blood volume
Several interconnected negative feedback systems
control blood pressure by adjusting:
- heart rate:
+ heart rate, + blood pressure - stroke volume:
+ stroke volumen, + blood pressure - blood volume:
+ blood volume, + blood pressure - systemic vascular resistance:
+ systemic vascular resistance, + blood pressure
mkay
Mechanisms to adjust blood pressure:
Systemic blood pressure:
- Neural regulation
- Hormonal regulation
And Local flux regulation: - Xregulation
Auto
The cardiovascular (CV) center receives input from higher brain centers.
Then, it provides output to the sympathetic and parasympathetic divisions of the
autonomic nervous system (ANS) to regulate heart and X (vasoconstriction)
blood vessels
Xreceptors (pressure-sensitive sensory receptors), are located in the aorta, internal
carotid arteries, and other large arteries in the neck and chest.
* They send impulses to the cardiovascular center to help regulate blood pressure.
Baro
The two most important baroreceptor reflexes are:
Carotid sinus reflex:
baroreceptors in the wall of the carotid sinuses help regulate blood pressure in the X.
- Aortic reflex:
baroreceptors in the wall of the ascending aorta and arch of the aorta regulate systemic X
brain
blood pressure
When blood pressure falls,
- Increases sympathetic and decreases parasympathetic stimulation (vasoconstriction)
- increased secretion of epinephrine and norepinephrine Consequence: ….
the heart beats faster
When an increase in pressure is detected,
- Decreases sympathetic and increases parasympathetic stimulation
- heart rate and force of contraction decreases
ok
carotid bodies descent from and aortic bodies, (they’re veins? its a bit unclear)
ok
chemoreceptors detect:
hypoxia (Low X)
* High X: hypercapnia
* High X: acidosis
O2
CO2
H+
Chemoreceptors provide input to the vasomotor center in the brain stem, but also to
the X center (also in the brain stem) to adjust the rate of breathing
In response, the CV center increases sympathetic stimulation to arterioles and veins,
producing vasoX and an in/decrease in blood pressure.
respiratory
constriction
increase
Renin secreted by kidney
in/decreases blood pressure through
Angiotensin II and aldosterone.
increases
Antidiuretic hormone (ADH) produced
by the hypothalamus in/decreases blood
pressure
increases
Atrial natriuretic peptide (ANP)
released by cells in the atria of the
heart in/decreases blood pressure.
decreases
Vasodilators produce X
dilation of arterioles and
relaxation of precapillary
sphincters: increases blood
flow into capillary networks.
* Vasoconstrictors have the
opposite effect.
local
Two types of stimuli cause autoregulatory changes:
1. Physical changes: warming promotes vasodilation, cooling vasoconstriction.
2. X: white blood cells, platelets, smooth muscle fibers, macrophages, and
endothelial cells release a wide variety of X that alter blood-vessel diameter
Chemicals
Vasodilating chemicals: K+, H+, lactic
acid, and adenosine, …..
Tissue trauma or inflammation
causes release of kinins and
histamine.
nitric oxide
Vasoconstrictors chemicals:
thromboxane A2, superoxide
radicals, serotonin (from platelets),
and endothelins (from endothelial
cells)
k
Do O2 levels autoregulate blood
pressure too?
yes
In response to low O2:
- The walls of blood vessels in the systemic/pulmonary circulation dilate: restores the normal
O2 level. - The walls of blood vessels in the systemic/pulmonary circulation constrict: ensures that
blood mostly bypasses poorly ventilated alveoli and flows to better-ventilated
areas of the lung.
systemic,
pulmonary
The venous system can accommodate a large volume of blood at relatively low
pressures: high capacitance.
- This feature permits the veins to hold a very high percentage of the blood in circulation:
blood X
(nearly 3/4 of all blood)
reservoir
Venoconstriction reduces/increases the volume of blood in reservoirs and allows a greater
blood volume to flow to skeletal muscles, where it is needed most.
- Venoconstriction is controlled by the cardiovascular center in the brain stem. When
needed, it sends a larger number of sympathetic impulses to veins.
reduces
Several mechanisms ensure venous retourn:
1. Gravity: blood from veins above the heart (head and neck) returns to the heart
simply by “flowing downhill”.
2. Preassure gradient: it occurs due to the pressure generated by contractions of the
heart’s left ventricle: the pressure difference from venules (averaging about 16
mmHg) to the right ventricle (0 mmHg), although small, normally is sufficient to
cause venous return to the heart.
3. X
4. Respiratory pump
Moreover, one-way valves inside veins that allow for
blood flow, toward the heart, in a forward direction.
Skeletal muscle pump
