Chapter 21 Flashcards
Blood Vessel Types
Arteries
- large elastic
- medium muscular
- arterioles
Capillaries
Veins
- venules
Blood Reservoir
Systemic veins & venules
Arteries
carry blood away from heart
Veins
carry blood **toward **heart
Largest arteries
**conducting arteries (elastic arteries) **
- wall are thin compared to overall size
Elastic Arteries
- function?
storing mech E during ventricular systole & then transmitting E to keep blood moving after aortic & pulmonary valves
Muscular (distributing) arteries
more smooth muscle in tunica media
- help maintain **vascular tone **to ensure efficient blood flow to distal tissue beds
- ***brachial & radial **artery *
Anastomosis
union of vessels supplying blood to same body tissue
*should vessel be occluded, **vascular anastomosis **provides **collateral circulation **(alternative route) for blood to reach tissue *
Arterioles
deliver blood to capillaries
have greatest collective influence on local blood flow & overall BP
- **primary adjustable nozzles **across which greatest drop in pressure occurs
Capillaries
only site in entire **vasculature **where **gases/water/nutrients **are exchanged
Venule/vein walls vs. artery walls
thinner walls
Veins
thinner walls, less muscle & elastic tissue, designed to operate at **lower pressure **
Intravenous pressure in venules vs. arterioles
intrav P in venules = less than half (16 mmHg) of intrav P in arterioles (**35 mmHg) **
**- **drops to just **1-2 mmHg **in some larger veins
Bc intravenous pressure is **so low, **how does blood keep flowing in one direction?
**valves **
What happens when veins are exposed to higher than normal pressure?
can become incompetant (varicose veins)
What determines how much fluid leaves arterial end of **capillary **& how much is **reabsorbed **at **venous end **
**hydrostatic & osmotic forces **at capillaries
(Starling Forces)
filtration
movement of fluid through walls of capillary into interstitial fluid
Reabsorption
movement of fluid from interstitial fluid **back into capillary **
Substances enter & leave capillaries by **(3) **basic mechanisms
diffusion
transcytosis
bulk flow
Bulk Flow
passive process in which **large numbers **of ions/molecules/particles in fluid move together in same direction
(2) pressure promote **filtration **
Blood hydrostatic pressure **(BHP) **
Interstitial fluid osmotic pressure **(IFOP) **
Blood hydrostatic pressure (BHP)
generated by **pumpinh action of heart **
Interstitial fluid osmotic pressure (IFOP)
constant at about 1 mmHg
(2) pressures promote **reabsorption **
blood colloid osmotic pressure **(BCOP) **
interstitial fluid** **hydrostatic pressure **(IFHP) **
blood colloid osmotic pressure (BCOP)
force caused by colloidal suspension of large proteins in plasma (averages 26 mmHg)
Interstitial fluid osmotic pressure (IFOP)
pulls fluid out of capillaries into interstitial fluid
- very small (.1-5 mmHg)