Blood Vessels
delivery system of dynamic structures that begins & ends at the heart
blood vessels
arteries
carry blood away from heart
_____ arteries carry deoxygenated blood
pulmonary
arterioles
small arteries that empty into capillary beds
capillaries
contact tissue cells + directly serve cellular needs
*exchange vessels
veins
carry blood towards heart
venules
small veins that drain capillary beds
Arteries + veins have 3 layers (tunics)
intima, media, + externa
lumen
central blood containing space
capillaries
endothelium (layer of simple epethelium) with sparse basal lamina
tunica intima
elastic
inner lining of tunica intima
has direct contact with blood as it flows through the lumen
*lined with endothelium
basement membrane of tunica intima
deep to the endothelium that provides physical support for the epithelial layer
*contains collagen fibers + provides tensile strength
elastic lamina of tunica intima
elastic fibers that give vessels stretch + recoil properties
tunica media
smooth muscle + sheets of elastin
sympathetic vasomotor nerve fibers control vascoconsrtiction + vasodilation of vessels
most variable of the tunics
tunica externa (tunica adventitia)
consists of collagen + elastic fibers
larger vessels contain vasa vasorum to nourish the external layer
vaso vasorum
small vessels that supply blood to the tissues of the cells
tunica intima consists of
endothelium
subendothelial layer
internal elastic lamina
tunica media consists of
smooth muscles + elastic fibers
tunica externa
collagen fibers
elastic arteries
*conducting arteries
act as pressure reservoirs- expand and recoil as blood is ejected from the heart
propel blood onward while ventricles are relaxing
elastic arteries have ____ luman which offer ___-resistance
large; low
muscular arteries
lie distal to elastic arteries
*deliver blood to body organs
***aka distributing arteries
muscular arteries have thick ____ ____ with more smooth muscle
tunica media
Anastomoses
union of 2+ arteries supplying the same body region
provide alternate routes for blood to reach a tissue/organ
referred to as collateral circulation
arterioles
smallest arteries that lead to capillary beds
plays a key role in blood flow regulation from arteries into capillaries by regulating resistance
changes in diameter causes changes in blood pressure
the tunica media of _______ consists of a layer of smooth muscle which controls flow into capillary beds via ____ + ____
artioles; vasodilation + vascoconstriction
capillaries
has thin tunica intima
its large surface area provides rapid exchange of material
found in all tissues except cartiledge, epithelia, and the cornea + lens of the eye
the thin tunica _____ of the ____ allows passage of only a single RBC at a time
intima; capillary
3 structural types of capillaries
continuous, fenestrated, sinusoidal
continuous capillares
most; abundant in skin + muscles
fenestrated capillaries
porous; found in kidneys, villi of s. intestine, choroid plexuses of brain ventricles, ciliary processes of the eyes & most endocrine glands
continuous capillary
fenestrated capillary
sinusoidal
venules
formed when capillary beds unite
very porous; allow fluids + WBC's into tissues
post-capillary venules consist of endothelium and a few pericytes
converge to form veins
larger venules have 1-2 layers of
smooth muscle cells
veins
serve as blood reservoirs- contain up to 65% of the blood supply at rest
structural features of veins
thinner walls + larger lumens than arteries
thin tunica media and thick tunica externa consisting of collagen fibers and elastic networks
valves
valves
structural modifications of the endothelial lining that aid venous return
varicose veins
leaky venous valves that cause veins to become dilated & torturous
capillary exchange: substances enter and leave capillaries in 3 ways
1. simple diffusion
2. trancytosis
3. bulk flow
simple diffusion
*solute exchange between blood + tissues;
molecules and solutes move from an area of high to low concentration
trancytosis
vesicular transport for large, lipid-insoluble molecules that can't diffuse simply
bulk flow
large #'s of ions, molecules, particles in a fluid move together in the same direction
pressure driven filteration + reabsorption
regulates relative volumes of blood & interstitial
filtration
pressure-driven movement of fluid + solutes from blood capillaries into interstitial spaces
pressures promoting filtration
blood hydrostatic (pumping action of the heart)
interstitial fluid osmotic pressure
reabsorption
pressure-driven movement of fluid + solutes from interstitial spaces to blood capillaries
pressure promoting reabsorption
blood colloid osmotic pressure
net filteration pressure
balances filtration + reabsorption
starling's law of the capillaries
equilibrium maintained between pressure driven filtration + pressure driven reabsorption
*determines whether volume of fluid & solutes reabsorbed matches the filtered-volume
Net Filtration Pressure =
NFP= (BHP + IFOP) - (BCOP + IFHP)
Blood hydrostatic pressure (BHP)
result of pressure that water in blood plasma exerts against vessel walls
*35 mmHg
-pushes fluid out of the capillaries into interstitial fluid
interstitial fluid hydrostatic pressure (IFOP)
opposes BHP
* close to 0 mmHg
-pushes fluid from interstitial spaces back into capillaries
blood colloid osmotic pressure (BCOP)
force caused by colloidal suspension of large plasma proteins
*26 mmHg
-Pulls fluid out of the interstitial fluid into capillaries
Interstitial fluid osmotic pressure (IFOP)
Opposes BCOP
Approximately 0.1-5 mmHg
Pulls fluid out of capillaries into interstitial fluid
*Usually only a small amount of protein here because most of it is taken up by the lymphatic system
Filtration: NFP
NFP = about 10 mmHg at the arterial end of a capillary so that there is a net outward pressure and fluid moves out of the capillary and into interstitial spaces
Reabsorption: NFP
NFP = -9 mmHg at the venous end of the capillary so that there is a net inward pressure and fluid moves into the capillary from the tissue spaces
85% of fluid filtered out of the capillaries is reabsorbed
NFP: Excess enters ______ and is returned to the jugular and subclavian veins in the
lymphatic system; upper thorax
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