Blood Vessels Flashcards
Tunica intima
■ Is the innermost layer
■ layer across which all nutrient and gas exchange occurs
■ found in all blood vessels
■ Includes:
■ the endothelial lining
■ connective tissue layer
Tunica media
■ Is the middle layer
■ Contains concentric sheets of smooth muscle in loose connective tissue
■ Binds to inner and outer layers
■ Dominant coat in large arteries
■ rich in Alpha (a1) receptors sensitive to NE
■ responsible for regulating blood vessel diameter.
■ External elastic membrane of the tunica media:
■ separates tunica media from tunica externa
Tunica externa
■ Is outer layer
■ Contains connective tissue sheath
■ Anchors vessel to adjacent tissues
■ In arteries:
■ contain a lot of collagen
■ elastic fibers
■ In veins:
■ contain mostly elastic fibers
■ smooth muscle cells
Differences between veins and arteries struture
1)arteries
-thicker walls
-elastic: w/stand ⬆️BP
-keep blood flowing during diastole
2)veins
-thinner
-walls: less elastic due to low pressure of blood returning to ❤️
-have valves to prevent backflow of blood
Contractility
-arteries change diameter
-controlled by SNS of ANS
-vasomotor of medulla
-uses NE➕ Alpha1 receptors (on smooth muscle of arteries/arterioles) to contract
-responsible for regulating vasoconstriction and BP
Only SNS
Continuous capillaries
■ Have complete endothelial lining
■ Tight junctions connect endothelial cells
■ Intercellular clefts allow passage of fluids and small solutes
■ Most common type
■ Are found in all tissues except epithelia, cartilage, cornea and lens of eye
Functions:
■ Permit diffusion of:
■ water
■ small solutes
■ Lipid-soluble materials
■ Block:
■ blood cells
■ plasma proteins
“Blood-brain barrier”
Vasa vasorum
The walls of arteries and veins are two thick to allow diffusion
■ Small arteries and veins
■ In walls of large arteries and veins
■ Supply cells of tunica media and tunica externa
Fenestrate capillaries
■ Have pores in endothelial lining
■ Permit rapid exchange of water and larger solutes (up to the size of small peptides):
■ between plasma and interstitial fluid
■ Function in absorption or filtrate formation
■ Are found in:
■ choroid plexus
■ endocrine organs
■ kidneys
■ intestinal tract
Circle of Willis
Ex. Of arterial anastomoses
ring-shaped network of arteries at the base of the brain that connects the brain’s two main blood supply systems
1)internal carotid arteries: supply oxygenated blood to front of brain
2)vertebral arteries(basilar): supply oxygenated blood to back of brain
Arterial anastomosis
Connects 2 arteries
Venous anastomoses
Connects 2 veins
Arteriovenous anastomoses
Connects artery to vein
Vascular shunts/false capillaries
-bypass the capillary beds
-blood does not reach the tissues (not site of exchange)
Capillary sphincter
-guards entrance to each capillary
-opens and closes➡️ capillary blood to flow in pulses
True capillaries
Are equipped w/ pre capillary sphincters sensitive to NE
Vasomotion
■ Contraction and relaxation cycle of capillary sphincters
■ Causes blood flow in capillary beds to constantly change routes
Venous reserve
Ability of veins to stretch allow them to act as a reservoir for blood in the body
Most blood in veins
If we lose blood➡️vasoconstriction➡️push 🩸 back into circuit
Cardiovascular regulation
maintaining capillary blood flow in peripheral tissues by controlling the diameter of arterioles, which directly impacts how much blood enters capillary beds, ensuring that tissues receive adequate oxygen and nutrients based on their current needs; this is achieved through mechanisms like neural signals, hormonal influences, and local metabolic factors that trigger vasoconstriction or vasodilation in the arterioles.
Blood flow
Blood flow= CO
-determined by pressure and resistance in cardiovascular system
Factors effecting blood flow
1) ⬆️BP➡️⬆️Blood flow
2) ⬆️resistance➡️⬇️blood flow
3)⬆️BV➡️blood flow
4)⬆️viscosity➡️⬇️blood flow
5)⬆️blood vessel length➡️⬇️blood flow
6)⬆️blood vessels diameter➡️⬆️blood flow
Factors effecting peripheral resistance
1)⬆️blood vessel diameter➡️⬇️R
2)⬆️blood viscosity➡️⬆️R
3)⬆️blood vessel length➡️⬆️R
TPR
Resistance in entire body that the ❤️ has to overcome to get blood from aorta➡️vena cava
Circulatory pressure
Change in pressure across system circuit (100mmHg)
Elastic rebound
Arterial walls:
-stretch during systole
-rebound during diastole
-keep blood movies during diastole
allows large arteries, like the aorta, to store energy during ventricular contraction (systole) and then release it during relaxation (diastole), maintaining a consistent blood flow throughout the cardiac cycle, preventing drastic pressure fluctuations and ensuring efficient blood delivery to the body; essentially acting like a “pressure reservoir” due to the elastic properties of their walls
Respiratory pump
-thoracic cavity action
-inhaling➡️⬇️thoracic pressure and sucks blood into blood vessels (boyles law)
-and pressure in vena cava
-fills vena cava➡️♥️
Cardiac output
CO=SVx HR
Measure of blood flow(determines normal BP)
⬆️CO➡️⬆️flow➡️⬆️BP
-⬆️SV
-⬆️ventricular BPM by⬆️NE from CAC
-⬇️cholinergics (ACh)
-⬆️(+) isopropics ➡️⬆️CO
-NE
-epi
-dopamine
-digitalis glycosides
-isoproterenol
Vessel diameter
⬇️vessel diameter➡️⬆️R➡️⬆️BO
⬇️vessel diameter can be due to:
-⬆️NE from vasomotor center
-arteriosclerosis- general thickening and loss of arterial elasticity
-focal calcification-deposistion of calcium salts and degeneration of tunica media- diabetes mellitus
Blood hydrostatic pressure
Pushing fluid out of capillaries
Blood osmotic pressure
Pushing fluid back in
NFP
NFP= filtration pressures- reabsorption pressure
NFP= (BHP+ IFOP) - (IFHP + BOP)
Arteriole end: 10mmHg (net filtration)
Venous end: -1mmHg (net reabsorption- b/c ⬇️BP)
As fluid accumulated in IF picked up by lymphatic vessels constantly➡️bloodstream
Myogenic control
■ Myogenic responses keep tissue perfusion constant despite most fluctuations in systemic pressure
■ Vascular smooth muscle responds to stretch
■ Passive stretch (increased intravascular pressure) promotes increased tone and vasoconstriction
■ Reduced stretch promotes vasodilation and increases blood flow to the tissue
Baroreceptor reflex
■ Stretch receptors in walls of:
■ carotid sinuses:
■ maintain blood flow to brain
■ aortic sinuses:
■ monitor start of systemic circuit
■ right atrium:
■ monitor end of systemic circuit
■ When blood pressure rises, CV centers:
■ decrease cardiac output
■ cause peripheral vasodilation
■ When blood pressure falls, CV centers:
■ increase cardiac output
■ cause peripheral vasoconstriction
Chemoreceptors reflex
Cartoid and aortic bodies monitor pH, O2, CO2
■ Changes in pH, O2, and CO2 concentrations
■ Produced by coordinating cardiovascular and respiratory activities
■ Example; A ß in pH and O2 levels w/ Ý in CO2 produce:
■ Cardioacceleratory and vasomotor center stimulation
■ Cardioinhibitory center ➖
■ Respiratory center stimulation
■ Increased O2 intake
■ Increased Respiratory pump activity
⬆️CO2➡️⬇️pH
EPO
causing vasoconstriction by increasing calcium influx in vascular smooth muscle cells, which can lead to elevated blood pressure
-released by kidneys
-responds to ⬇️BP
-➕RBC production
Shock
-results from loss of 30% or BV
-failure to restore BP
Fetal circulation
■ Embryonic lungs and digestive tract nonfunctional
■ Respiratory functions and nutrition provided by placenta
Before birth:
■ Fetal lungs are collapsed
■ O2 provided by placental circulation
After birth circulation
■ Newborn breathes fast
■ Lungs expand
■ Pulmonary circulation provides O2
2 fetal pulmonary circulation bypasses
• Foramen ovale:
■ interatrial opening
■ covered by valve-like flap
■ directs blood from right to left atrium only
• Ductus arteriosus:
■ short vessel
■ connects pulmonary and aortic trunks
Cardiovascular changes at birth
■ Pulmonary vessels open
■ Reduced resistance allows blood flow
■ Rising O2 causes ductus arteriosus constriction
■ Rising left atrium pressure closes foramen ovale (flap)
