III Blood Vessels Flashcards
General Function of Arteries
- Carry blood AWAY from the heart - continuously
General Function of Veins
Carry blood TO the heart
Structure of Large Arteries
- Smooth muscle & elastic tissue
Function of Large Arteries
Store pressure from the heart
(ventricles contract, and arteries stretch)
Ventricles relax and ELASTIC arteries RECOIL, pushing blood onward
Structure of Medium-sized Arteries
Mostly muscle, less elastic
Function of Medium-sized arteries
Distribute blood to various regions
Aneurysm
Weak point in an artery or heart wall
Structure of Arterioles
Small
Muscle + endothelium + connective tissue
Function of Arterioles
Regulate flow to tissues and pressure
Arterioles Vasoconstriction
Flow DECREASES
Pressure INCREASES
Arterioles Vasodilate
Flow INCREASES
Pressure DECREASES
Metarterioles
Like arteries to capillaries. Have sphincters
Structure of Capillaries
thin-walled
Single layer of endothelial cells
in all tissues of body
Function of capilaries
Permit exchange of: nutrients, waste, O2, CO2
Precapillary Sphincters
Open and close to allow blood to get to areas of need. Only around 1/4 open at a time
Veins General info
Hold more blood than areteries
Lower pressure 10 mm Hg
54% of blood
Venules Structure
Small vessels, little muscle and no elastic tissue
Structure of Veins (and difference with arteries)
Same layers as arteries but: Thinner walls Less elastic tissue One-way Valves Larger Lumens
Blood pressure changes through body
Drops as it goes. (smaller vessels offer more resistance)
Aorta 100 mm Hg Arteries 85 mm Hg Arterioles 35 mm Hg Capillaries 20 mm Hg Venous System 0 mmHg
Where is largest drop in pressure?
Arteries –> Arterioles
3 main factors affecting blood pressure
- Cardiac Output
- Blood Volume
- Peripheral Resistance
Any increase in these 3 increases blood pressure
Factors influencing blood volume
concentration of solutes in body fluids, blood
Regulation of blood volume
Fluid consumption and excretion through the kidneys
Peripheral Resistance
Any force the opposes movement
Factors that influence Peripheral Resistance
blood viscosity
blood vessel length
blood vessel diameter
total cross section area of vessels
Speed of flow in different parts
Fastest in Aorta
Slow in Capillaries
Moderate in Veins
Factors that impact flow
Friction
Resistance to flow in small vessels
Which two systems regulate blood pressure?
Nervous System
Endocrine System
Endocrine System impact on blood pressure during stress
Epinephrine & Norepinephrine
vasoconstriction on most vessels (pressure ++)
vasodilation on cardiac and skeletal muscles - more blood to limbs and heart
Antidiuretic hormone -> blood pressure impact
Causes fluid retention
Increases blood pressure
Aldosterone -> blood pressure
response to low blood pressure
causes vasoconstriction
Nitric Acid & Prostagalandis –> blood pressure
Response to trauma, inflammation, and local oxygen depletion
vasodilation
Capillary Exchange
Exchange of nutrients, wastes, and gasses between blood and interstitial fluids
Main forces of capillary exchange
Osmotic Pressure (OP) Hydrostatic Pressure
Factors that impact venous return
- Muscle contraction
- Decreased venous compliance
- Respiratory inspiration/expiration
- Vena cava compressoin
- Gravity
END Arteries
an artery that is the only supply of oxygenated blood to a portion of tissue
3 examples of END arteries
Arteries of:
Spleen, kidney, lungs, metaphyses of longbones
