Blood Vessels Flashcards
Define Arteries
carries blood AWAY from the heart, for blood distribution
Define Capillaries
exchange vessels
Define Veins
carry blood TOWARDS the heart, for blood collection and return. (Some veins have valves)
What are the three blood vessel wall layers
- Tunica interna (intima
- Tunica media
- Tunica externa (adventia)
Define Tunica Interna (intima)
innermost layer, conists of endothelium layer, subendothelial layer,
in arteries only- internal elastic layer
Blood Vessel functions (3)
1.transport blood
2.Temperature regulation through 3.vasoconstriction & vasodilation
The cells lining blood vessels make regulatory molecules like nitric oxide
Define Tunica media
middle layer composed of CIRCULAR SMOOTH MUSCLE for VASOCONSTRICTION/DIALATION
in arteries only- external elastic layer
Thickest layer in Arteries
Define Tunica externa (adventia)
outermost layer, mostly of collagen fibers
Thickest layer in Veins
What are the three classes of arteries
- elastic arteries (conducting)
- muscular arteries (distributing)
- Arterioles (resistance)
Elastic Arteries
(conducting arteries) Large lumen and low resistance Includes aorta and its major branches contain thick muscle layer but dont really constrict pressure reservoirs
Muscular Arteries
(distributing arteries)
delivers blood to specific orhans
have the biggest proportion of muscle, tunica media in theses vessels has less elastin, but a bigger proportion of muscle.
EX: brachial, splenic, and femoral
Arterioles Arteries
(resistance arteries)
Too small to be given specific names
lumen rages from 300 um down to 10 um with an average of 37um
determine moment-to-moment blood flow to particular structures by their degree of constriction
control relative blood flow distribution
Capillaries
- location
- thickness
- Located between arterioles and venules connecting them together
- One cell layer thick
- average length of 1 mm long
Capillary Functions
where substances are exchanged between plasma and interstitial fluid
-tendons and ligaments are poorly vascularized, so not capillaries-
3 types of Capillaries
- Continuous capillaries
- Fenestrated capillaries
- sinusoids
Continuous Capillaries
- most capillaries
- Joined by tight junctions
- abundant in skin and muscles
- least permeable
Fenestrated Capillaries
- Pores–leaky
- located in some endocrine glands, the small intestine and the kidneys
Sinusoid Capillaries
- Wide diameter that are more winding with gaps between endothelial cells
- liver spleen, bone marrow and lined with macrophages
- also found in some endocrine glands
Metarteriole
artery side of the capillary bed
thoroughfare channel
vein side of the capillary bed
precapullary sphincters
rings at the start of the capillary (made of smooth muscle) can control blood flow into the capillary bed
True capillary
actual literal legit for real branching capillary
Define Venules
smallest veins
-fuse to form veins which start small and then go large
Venous sinus
thin-walled veins with no muscle, such as the coronary sinus and the dural venous sinuses of the brain
Vein Walls
except for small venules, veins have all 3 layers though they are thinner than arteries
tunica externa is the thickest layer
Vein functions
- low resistance conduits: large diameter and thin distensible walls
- Blood reservoirs: very stretchy so can hold much blood, can constrict sending more blood to the heart. in return EDV, stretch, SV CO and BP all increase
How much blood does the systemic veins contain? %
60%
How much blood does the heart arteries and capillaries contain? %
30%
How much blood does the pulmonary vessels contain? %
10%
Define Portal system
2 capillary beds
Define anastomosis
where 2 blood vessels merge
Arteriovenous anastomosis
no capillary bed, resulting in less heat loss
Venous anastomosis
most common tpe, one vein empties into another
Arterial anastomosis
two arteries merge to provide collateral blood flow
Define Flow
the volume of blood flowing in a given time
-Blood pressure and resistance determine BF
Autoregulation (local control)
regulation by locally produced chemicals does NOT involve nerve enervation or hormones
-tissue has too low of blood supply–> vasodilation occurs which increase flow
Vasoactive chemicals
nitric oxide (NO)
what is doing vasomotion
mainly the job of the arterioles
3 controls of vasomotion
- local controls (auto regulation)
- neural controls (vasomotor center)
- hormonal controls
Tissue perfusion
rate of blood flow through the tissues
3 factors that determine BP
- CO
- PR
- Blood volume
BP regulation is accomplished by..
neural control and hormonal control
Neural Control
Vasomotor Center- cluster of sympathetic neurons in the medulla oblongata
+ cardiac centers (CAC&CIC)—> makes up cardiovascular center
*control BP by altering CO (CAC&CIC) and vasodilatation (VC)
Cardiovascular center is made of
CAC-hear
CIC- heart
VC- Bl. vessels
Define Vasomotor Tone
vessel diameter at rest. Always being moderately constricted by the VS sympathetic fibers(by releasing NE)
lessNE= dilation
moreNE= contraction
3 autonomic reflexes that regulate the vc
- Barroreceptors
- Chemoreceptors
- Medullary Ischemic reflex
Barroreceptors
- location
- function
located in the carotid sinus monitor pressure (stretch) -neg feedback loop that corrects change in bp
Effects of an increase in BP
exciting of the CIC and inhibit th eCAC
Effects f=of an decreasing BP
exciting the CAC inhibit the CIC
Chemoreceptors
- location
- function
Located in the aortic bodies and carotid bodies
monitor changes in O2, CO2 and H+
-stimulate breathing to match increase blood flow. control more of the respiration side rather than bp
Medullary Ischemic relfex
- location
- function
Located in medulla??
kicks in when there is a drop in perfusion (bf) to the brain
immediately VC increase HR and contraction
and causes widespread vasoconstriction
6 Hormones that affect BP
- Angiotensin II
- Aldosterone
- Atrial natriuretic peptide (ANP)
- Antidiuretic hormone (AHD)
- Epinephrine and NE
- Cortisol
Angiotensin II
released when the kidneys release renin
increases BP
Aldosterone
causes NA+ retention, increasing BP
ANP Atrial natiuretic peptide
increases sodium excretion
produced by atria
decreases BP
Antidiuretic hormone ADH
causes kidneys to retain more water
Increases BP
NE
increases vasoconstriction
Epinephrine
Increase CO and Vasoconstriction
Cortisol
increase BP by increasing water and salt retention
4 ways in which substances cross capillaries
- through cell membrane (lipid sol.)
- Intercellular clefts between cells (water sol.)
- Through fenestrations (water sol.)[pore within the cell]
- Via vesicles (large substances)
