Blood Vessels Flashcards
Arteries
Blood vessels carrying blood away from the heart
Arteries tend to be __________ to the heart and ____________ in diameter
- Closer
- Larger
The farther away from the heart the smaller the _____________.
Arteries
Arterioles are ________
Smaller than arteries and lead to capillary beds and control blood flow via smooth muscle constriction
Capillary beds are __________ . Why?
- Leaky
- To allow for exchange of materials between plasma, interstitial fluid and cells
What are capillaries made of and why?
- Capillaries consist of a single layer of epithelial cells, the endothelium tunic (tunica intima).
- To allow for gas exchange
Gas exchange at the capillaries
- Oxygen is diffusing from the blood in the capillaries to the tissue
- Carbondioxide is diffusing out of tissues and into the blood
- RBCs must move slowly to allow gas exchange to happen
Veins
Blood vessels carrying blood back to the heart
Which are more numerous in your body veins or arteries?
Veins
Veins have _____________ than arteries.
lower pressure
Venules
- Are formed when capillaries come togther
- They are porus which allows WBCs and fluids into the tissues
How do veins work under low pressure since your feet do not have a heart?
veins use:
- Muscular pump
- Respiratory pump
- Sympathetic Venoconstriction
- These adaptations helpto increase venous return (blood returning back to the heart)
There is a ___________ between veins and arteries
- Pressure gradient
- Arteries work under high pressure while veins work under extremely low pressure.
Veins work __________ with __________.
- Low pressure
- Valves
Which layer of the blood vessel controls the diameter of the lumen?
Tunica media; contains smooth muscle, controls blood pressure and blood flow.
Vasoconstriction
- Lumen gets smaller (Tunica media contracts)
- Blood pressure rises as vessel becomes constricted
- Caused by more frequent APs from sympatheic Nervous system
Vasodilation
- Lumen’s diameter becomes larger (Tunica media relaxes)
- Blood pressure lowers as vessel dilates
- Less frequent APs from sympatheic nervous system causes this
Vasoconstriction and vasodilation are both controlled by ___________.
Sympathetic nervous system fibers and many chemicals
Vericose veins
are caused by too much pressure comming from the upper half of the body causes veins to collapse and valves to weaken allowing blood to pool.
What are the layers of a blood vessel?
- Tunica intima
- Tunica Media
- Tunica Externia
Tunica intima
Contains:
- Endothelium
- subendothelial layer
- internal elastic membrane
Tunica Media contains
- smooth muscle and elastic fibers
- external elastic membrane
Tunica externa contains
- Collogen fibers
- Vasa vasorum
Endothelium
epithelial cells that line the blood vessels
A capillary contains
- A basement membrane
- endothelial cells
What is the diameter of a capillary?
~8-10 micrometers (um)
What is the diameter of a RBC?
~ 6-8 um (micrometers)
7 um
What is being exchanged in the capillary beds?
Oxygen and carbondioxide
Nutrients and wastes
how thick are capillaries?
one cell layer thick
Blood flow is slowest in the capillaries why?
To allow gas exchange between RBCs and tissues to occur
Tissues that are metabollically active will have _______________.
a large amount of capillaries
Most gase exchange takesplace using _________________.
diffusion
how is blood flow controlled in capillaries?
by capillary sphincters
Blood flow
•volume of blood flowing through a vessel or organ in a given time period (ml/min)
Resistance
Opposition to flow
Viscosity
thickness of a fluid
Resistance is affected by 3 things
- Blood viscosity
- Length of blood vessel
- Blood vessel diameter
How does blood viscosity increase resistance in blood vessels?
More RBCs are bumping into eachother in the blood vessel.
what is another thing that may affect resistance in blood vessles?
atherosclerosis
What control’s blood flow?
- Pressure gradient
- Resistance
Blood flow is directly proportional to…
blood pressure gradient; high to low pressure
Blood flow is inversely proportional to _____________.
resistance
Blood flows down a _____________.
Pressure gradient
Blood pressure is highest where? Where is it lowest?
- Aorta
- Vena Cavae
Blood pressure
force exerted on the walls of the vessels -measured in mmHg
What is normal blood pressure?
120/80 mmHg
Systolic Pressure
- peak pressure generated by ventricle contracting
Diastolic Pressure
lowest pressure
Pulse pressure
•difference between systolic and diastolic pressure
What maintains blood pressure?
Requires cooperation between heart, blood vessels and kidney, while being supervised by the brain
What are the main factors influencing BP?
- Cardiac output CO= HRxSV; L/min
- resistance
- Blood volume
if one variable influencing/controlling BP changes then…
the other variables will quickly change in order to compensate
Who carries out short term bp regulation?
- The brain and hormones
- They alter blood vessel (low blood volume) diameter to suppy specific organs
medulla oblongata
- stimulates and inhibits heart activity
- Brain’s cardiovascular center
Vasomotor center
part of brain that controls diameter of blood vessels
Baroreceptors
special strech receptors in carotid arteries which “sense” BP changes.
What is the over all goal of short term blood pressure regulation?
to change cardiac output and resistance
How is blood pressure lowered back to homeostatic range?
- Stimulus: Bp rises; arterial blood pressure rises above normal range.
- Baroreceptors in carotid sinuses and aortic arch are stimulated
- Increased impulses from baroreceptors stimulate cardioinhibitory center and inhibit cardioacceletory center and inhibit vasomotor center
- a decrease in vasomotor impulses allows vasodilation, causing decreased resistance
- decrease in sympathetic impulses to heart cause decreased heart rate, decreased contractility, and decreased cardiac output
- decreased cardiac output and decreased resistance return BP to homeostatic range
How is BP raised to Homeostatic range?
- stimulus: low blood pressure; arterial blood pressure falls under normal homeostatic range
- Baroreceptores in carotid sinuses and aortic arch are inhibited
- Decreased impulses from baroreceptors activate cardioacceletory center and inhibit cardioinhibitory center and stimulate vasomotor center
- increase in sympathetic impulses to the heart cause heart rate to go up, contractility to go up and cardiac output to go up.
- Vasomotor fibers stimulate vaso constriction causing resistance to go up.
- increased cardiac output and resistance return bp to homeostatic range
The lymphatic system picks up leaked fluid from the cardiovascular system and returns it to ___________.
the heart
what is the fluid found in the lyphatic system called?
Lymph
Lymphnodes contain lyphocytes, why?
Lymphocytes are formed in the lymph nodes.
What is hypertension?
- High blood pressure over 140/90 mmHg
What are thetypes of hypertension?
- Primary; no one identifable cause (90%)
- Secondary; Due to a condition, kidney disease, endocrine disorders (10%)
Atherosclerosis
fatty build-up clogs arteries, impairs blood flow, affects BP, oxygen delivery, etc.
Congestive heart failure
heart becomes an ineffecient pump that weakens over time.
