Blood Vessels Flashcards
Which vessels carry blood AWAY from the heart?
Arteries
Where do arteries carry blood?
Away from the heart to the capillaries in tissues.
Large arteries that leave the heart divide into medium-sized (______) arteries.
Distributing
Distributing arteries branch to form what?
Arterioles
What is the term for the CONTRACTION of blood vessel walls?
Vasoconstriction
What is the term for the RELAXATION of blood vessel walls?
Vasodilation
Vasoconstriction _________ blood pressure.
Vasoconstriction INCREASES blood pressure.
Vasodilation _________ blood pressure.
Vasodilation DECREASES blood pressure.
Where are arteries more elastic, and why?
Arteries closer to the heart are more elastic, giving resistance to the high blood pressures of the blood leaving the left ventricle.
Where are arteries more muscular?
Arteries further from the heart have more muscle to help them maintain BP.
Define ‘lumen’
(from Latin lumen, meaning “an opening”; plural lumina) LUMEN: the inside space of a tubular structure, such as an artery or intestine.
What is the innermost layer of an artery?
Endothelium - a thin layer of epithelial cells; in contact with blood.
Endo-: internal; within // -thelium: layer of (specified kind of) cellular tissue
What is the middle layer of an artery?
Tunica media - central layer of elastic tissue and smooth muscle that can stretch and contract.
What is the ‘tunica externa’?
The outer layer of the artery; a thick layer of elastic and connective tissue that allows for expansion of the artery.
What is the purpose of smooth muscle in artery walls?
The smooth muscle around arteries helps to regulate blood flow and pressure. By contracting or relaxing it alters the diameter of the artery and adjusts the volume of blood as required.
What is the effect of vasoconstriction on the diameter of an arteriole?
The diameter DECREASES.
What is the effect of vasodilation on blood pressure?
Blood pressure DECREASES.
Where do veins carry blood?
Back from the tissues to the heart.
Where do venules carry blood?
From capillary beds to larger veins.
Which type of blood vessel contains approx 59% of blood in the body?
Veins, and their branches.
When several capillaries unite, they form….
….small veins called VENULES.
Veins are made up of essentially the same 3 layers as arteries but have ____ elastic and muscle tissue and a ______ lumen.
…LESS elastic and muscle tissue and a LARGER lumen.
Venules closest to capillaries are missing which layer?
Tunica media
Blood flowing in the ___ has ____ a lot of pressure because it has passed through the narrow _______ vessels.
Blood flowing in the VEINS has LOST a lot of pressure because it has passed through the narrow CAPILLARY vessels.
What structure in veins is made necessary due to lower blood pressure?
One-way (Jesus) valves
What is another term for the endothelium?
Tunica intima
Which has less elastic and muscle tissue: veins or arteries?
VEINS have less elastic and muscle tissue, but can still expand enough to adapt to changes in pressure and volume of the blood passing through them.
Which has a relatively larger lumen: veins or arteries?
VEINS have a larger lumen, relative to the size of tube layers (which are smaller because blood travels through veins at a lower pressure than arteries).
Why does blood ooze from a venous wound, rather than spurting as from an arterial wound?
Venous blood oozes out in an even flow from a wound because it has lost a lot of pressure after passing through the narrow capillary vessels.
Arterial blood spurts rapidly because it is being pumped directly from the heart and has not yet entered the capillary networks.
What is the purpose of capillaries?
Capillaries allow for efficient exchange of nutrients and wastes between the blood and tissues.
Blood passes from the arterioles into the ______.
Blood passes from the arterioles into the CAPILLARIES.
Capillary walls are formed of…
…a single layer of endothelial cells.
How slow is blood flow in capillaries?
< (less than) 1mm per second
Diameter of a capillary is between
4-10μm (RBCs are 7-8μm and just squeeze through)
_____ _______ causes fluid to leak from capillaries through small gaps where the ________ cells join.
BLOOD PRESSURE causes fluid to leak from capillaries through small gaps where the ENDOTHELIAL cells join.
When fluid from capillaries bathes tissue, it supplies which 2 things and removes what?
Supplies nutrients and oxygen; removes waste.
The density of capillaries in a tissue is an indicator of what?
The tissue’s metabolic activity.
Define smooth muscle
Muscle tissue in which the contractile fibrils are not highly ordered, occurring in the gut and other internal organs, and not under voluntary control.
Cardiac muscle is highly active and therefor requires a high amount of blood supply and is well supplied with ______.
…CAPILLARIES.
Cardiac muscle relies heavily on oxidative metabolism [a chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also called aerobic metabolism, aerobic respiration, and cell respiration.] and thus has a high demand for blood flow.
Microscopic blood vessels in some dense organs (e.g. liver) are called…
…SINUSOIDS.
Instead of endothelial cells, SINUSOIDS are lined with…
…PHAGOCYTIC CELLS.
Which is wider: capillaries or sinusoids?
Sinusoids
Compared to capillaries, sinusoids follow a more _____ path through tissue.
Compared to capillaries, sinusoids follow a more CONVOLUTED/ COILED/TWISTED path through tissue.
The endothelium is made of what type of cells?
Squamous epithelial cells.
Squamous: relating to, consisting of, or denoting a layer of epithelium that consists of very thin flattened cells
Which blood vessels are made of a thin epithelium, a central layer of elastic tissue and smooth muscle, and a thick outer layer of elastic and connective tissue?
Arteries
Which blood vessels are made of a thin epithelium, a central layer of elastic and muscle tissue and a thin outer layer of elastic connective tissue; as well as having valves?
Veins
In what way are capillaries and sinusoids similar?
They both transport blood from arterioles to venules.
Capillaries form _________ networks where exchanges between the b_____ and t______ take place.
Capillaries form BRANCHING networks where exchanges between the BLOOD and TISSUES take place.
What is the term for the flow of blood through a capillary bed?
Microcirculation
What is the name of the vessel that connects the arteriole and the venule (which are at either end of the capillary bed)?
Vascular shunt
When would blood need to bypass the true capillaries via the vascular shunt?
When the tissue activity (and therefore metabolic demand) is low.
What structures direct blood flow between arterioles and venules?
Smooth muscle sphincters (close to channel blood through vascular shunt; open to allow blood into true capillaries).
What vascular response would occur if the body were to need to conserve heat?
Smooth sphincter muscles would contract, channeling blood through the vascular shunt, to keep blood away from the extremities.
What is the full name of the arteriole where blood enters a capillary bed?
Terminal arteriole
What is the full name of the venule where blood is collected from a capillary network?
Postcapillary venule
What is special about gut capillaries and liver sinusoids?
They form a portal venous system.
How does a portal venous system differ from other capillary systems?
A portal venous system drains blood from one capillary network into another.
An example is the hepatic portal system which drains blood from the capillary network in the gut to the capillary (technically sinusoid) network in the liver.
Normally capillary networks drain into veins that return directly to the heart.
What is the role of tissue fluid?
Provides oxygen and nutrients; removes wastes.
What does the extensive capillary network ensure? (In relation to diffusion and delivery of oxygen and nutrients to cells).
That no substance has to diffuse far to enter or leave a cell.
By what 3 ways do substances move in and out of capillary networks? (Other than through connected vessels).
- Diffusion
- Cytosis (endo-, exo-, trans-)
- Through gaps where the membranes are not joined by tight junctions.
Lymph is similar to tissue fluid but has more…
Lymphocytes (a form of small leucocyte (white blood cell) with a single round nucleus, occurring especially in the lymphatic system).
What 2 factors together determine whether fluid moves in or out of a capillary?
Blood pressure & concentration of solutes
At which end is hydrostatic pressure (HP) highest? Arteriolar or venular?
Arteriolar (where blood enters the capillary network).
Approximately how much of the leaked fluid re-enters the capillary?
90%
What happens to the tissue fluid that doesn’t re-enter the capillary?
It is collected by lymphatic vessels to be returned to the subclavian vein near the heart. (Sub-: below, -clavian: refers to the clavicle which is the anotomical term for collar bone.)
What two things are higher toward the arteriolar end of a capillary network?
Hydrostatic pressure & solute (dissolved substances) concentration
In what 2 ways is tissue fluid returned to general circulation?
- re-entering the capillaries (as a result of net inward pressure at the venule end of the capillary bed)
- lymph vessels (which parallel the bloodtsream and drain tissue fluid [as lymph] back to the heart, thereby returning it to main circulation).
