Vessels Flashcards
-What are the 3 types of blood vessels
veins arteries and capillaries
What is the Lumen
Lumen is the space within the vessels
Rank tunics from innermost to outermost
Tunica intima
Tunica media
Tunica externa
Characteristics of the tunica media
◦ Contains smooth muscle cells
◦ Vasoconstriction / vasodilation
◦ Numerous elastic fibers to allow for stretch
Characteristics of the tunica externa
◦ Helps anchor vessels to surrounding structures
◦ Can contain vaso vasorum – network of small arteries
Companion vessels
vessels that lie next to eachother
Arteries compared to other vessels…
Have more collagen and elastic fibers
Additionally they have thicker tunica media and narrower lumen than veins
Veins compared to other vessels…
less elastic and collagen fibers
Have thicker tunica externa and larger lumen than arteries
Walls collapse if empty
Capillaries compared to other vessels…
thin layer of tunica intima only
What is artery branching?
◦ Branch into smaller vessels extending from heart
◦ Decrease in lumen diameter
◦ Decrease in elastic fibers
◦ More smooth muscle in arteries farther away from heart
Elastic arteries (conducting)
Largest type of artery
Conduct blood from heart to muscular arteries
◦ Many elastic fibers allowing stretch and recoil
◦ Aorta, pulmonary trunk, common carotid, common
iliac arteries
Muscular arteries (distributing)
Medium in size
Most arteries: brachial artery, coronary arteries
◦ Distribute blood to specific body regions
◦ Muscle allows vasoconstriction (and dilation)
◦ Elastic tissue in two layers
2 Layers of muscular arteries that have elastic tissue
◦ Internal elastic lamina between intima and media
◦ External elastic lamina between media and externa
Arterioles
Smallest
◦ Smooth muscle usually somewhat constricted
◦ Called vasomotor tone (brainstem input)
◦ Regulate systemic blood pressure and blood flow
Capillary characteristics
– Small vessels connecting arterioles to venules
o Erythrocytes travel single file (rouleau)
– Optimal thinness for exchange between blood and tissue
Continuous Capillaries
◦ Endothelial cells form a continuous lining
◦ Tight junctions connect cells but don’t form
a complete seal
◦ Intercellular clefts are gaps between cells
◦ Large particles (e.g., cells, proteins) cannot
pass, but smaller molecules (e.g., glucose)
can pass through wall
◦ Muscle, skin, lungs
Fenestrated capillaries
◦ Endothelial cells have a continuous lining but cells
have fenestrations (pores)
◦ Allows movement of smaller plasma proteins
◦ Found in filtering areas
◦ Intestine, kidney, etc.
Sinusoid capillaries
◦ Endothelial cells form an incomplete lining with
large sinusoids (holes)
◦ No basement membrane
◦ Transport of large substances (formed elements,
large proteins)
◦ Bone marrow, spleen, endocrine organs
Capillary beds
Group of capillaries that work together
Capillary beds are fed by..
metarteriole—a vessel branch of an arteriole
The distal part ___________ connects to ___________
thoroughfare channel; postcapillary venule
True capillaries
Branches from metarteriole
Precapillary sphincter
Smooth muscle ring at true capillary origin
Vasomotion
cycle of contracting and relaxing of precapillary sphincters
Perfusion
◦ Amount of blood entering capillaries per unit time per gram of tissue
◦ Units are mL/min/g
Venules
◦ Companion vessels with arterioles
◦ Merge to form veins
very small
Small and medium size veins are companion vessels with…
muscular arteries
Large veins travel with _______ most veins of this size have ______ preventing _______
elastic arterie; valves; backflow
At rest what % of blood is in circulation?
70%
What Is the breakdown of systemic circulation at rest
◦ Systemic veins, 55%
◦ Systemic arteries, 10%
◦ Systemic capillaries, 5%
additionally
◦ Pulmonary circulation has 18% of blood
◦ Heart has 12% of blood
Blood is moved from the veins into circulation via…
vasoconstriction
blood is shifted back to the reservoirs by…
vasodilation
Simple pathway of blood vessels
◦ One major artery delivers blood to organ or region
◦ Arterioles -> capillary bed -> venule -> major vein ->
heart
Arterial anastomosis
Two or more arteries converge to supply same
region
Venous anastomosis
Two or more veins drain same body region
Arteriovenous anastomosis
Transports blood from artery directly to vein
Portal system
Path: artery -> capillary bed > portal vein >
capillary bed > vein
Diffusion
substances leave or enter blood according to their concentration gradient
(high to low concentration)
What is the route diffusion takes place based upon?
Particle size
Small solutes diffuse…
through endothelial cells or intercellular clefts
Larger solutes pass through…
fenestrations or gaps in sinusoids
Vesicular transport
Endothelial cells use pinocytosis and exocytosis
◦ Take substances in by pinocytosis - “cell drinking”
◦ Form fluid-filled vesicles at plasma membrane
◦ Secrete substance from other side by exocytosis
Bulk flow
fluids flow down pressure gradient
◦ Large amounts of fluids and dissolved substances move
Filtration
fluid moves out of blood (arteriole end)
◦ Fluid and small solutes flow easily through capillary’s openings
◦ Large solutes blocked
Reabsorption
fluid moves back into blood
◦ Venule end
Bulk flow is driven by:
Hydrostatic pressure and Colloid osmotic pressure
Blood hydrostatic pressure (HPb)
◦ Force exerted per unit area by blood on vessel wall
◦ Pressure of blood pushing out of vessel
Interstitial fluid hydrostatic pressure
(HBif)
◦ Force of interstitial fluid on outside of blood vessel
◦ Pressure of fluid outside of vessel pushing back in
Blood colloid osmotic pressure (COPb)
◦ Draws fluid into blood due to blood proteins (e.g., albumins)
◦ Pull of fluid in to vessel
Interstitial fluid colloid osmotic pressure (COPif)
◦ Draws fluid into interstitial fluid (usually very low)
◦ Pull of fluid out of vessel
Net filtration pressure (NFP)
NFP is the difference between net hydrostatic pressure and net colloid osmotic pressure;
that is:
NFP = (HPb - Hpif) - (COPb - COPif)
(Blood’s push out – Interstitial fluid’s push in) - (Blood’s pull in – Interstitial fluid’s pull out)
Net hydrostatic pressure
Difference between blood and interstitial fluid hydrostatic pressures
Net colloid osmotic pressure
Difference between blood and interstitial fluid osmotic pressures
