Download The Cardiovascular System Circulation

The Cardiovascular System Blood Vessels and
Circulation
Blood Vessels Have Two Functions
1. Carry blood to and from the lungs for oxygenation
2. Carry blood to and from every cell in the body
• Blood vessel diameters range from 2.5 cm (at the aorta
of the heart) to microscopic (capillaries) in tissues
Blood Has Two Primary Functions
1. Deliver Oxygen (O2) gas and
nutrients to every cell in the body
2. Remove Carbon Dioxide (CO2) gas
and waste from every cell in the
body
• Blood is made of both cells and liquid
(plasma)
Pulmonary Circuit – Systemic Circuit
• Arteries always carry blood away from the heart and veins always
carry it back to the heart
• Pulmonary Circuit - Right Side of heart
• Arteries to lung carry deoxygenated blood
• Veins back to heart carry oxygenated blood
• Systemic Circuit - Left Side of heart
• Arteries to body carry oxygenated blood
• Veins back to heart carry deoxygenated blood
• 60,000 miles of blood vessels in each person
Layers
1. Smooth lining
2. Smooth muscle
3. Outer covering
Function
1. Smooth flow
2. Vasoconstriction
/dilation
3. Support,
attachment more vessels?
Blood Vessels – Arteries
• Blood moves fast, away from heart
• Thick walls – have more smooth muscle to regulate
vasodilation or vasoconstriction
• Large arteries narrow or branch to smaller arteries
and finally to “arterioles” before becoming
capillaries
• “Elastic” arteries near heart to smooth out the
initial force
• “Muscular” arteries farther out for vasoconstriction
– controlled by hormones, nerves
Blood Vessels – Capillaries
• The goal of the cardiovascular system
occurs here
• Only vessels where fluid, gas, and nutrientexchange occurs with tissue cells
• Microscopic – small diameter – single RBC
file
• Blood slows – lots of branching
• Capillary beds ~ 1 mm. Feed all tissues
• Can be turned on or off depending on need
Leaky Capillaries
• One-cell thin inner wall, occasional smooth
muscle for stabilizing them. Leakiness
depends on the tissue they serve, the size
of the molecules transferred, or how fast
they need to transfer
• A little leaky – small clefts – very tight in
brain
• Leaky – small pores – kidney, digestive tract
• Very leaky – large pores, bigger clefts –
liver, bone marrow, lymphatics. Allow cells
to pass through
Capillary Beds
• Interweaving networks – “Microcirculation”
• Contains 10-100 capillaries
• Contains one bypass shunt vessel
• Has its own control features – sphincters
• Depends on local tissue chemistry or nerve
signals
• Example – digestion and exercise
Blood Vessels – Veins
• From capillaries, blood moves to “venules,” that
merge into small veins, larger veins, then
“dumps” back into heart
• Much less smooth muscle in their walls
• Slower blood flow. Skeletal muscle helps flow
• Have valves to keep blood moving forward
• > 60% of all blood in body is in veins at any time
Control of Blood Flow
Anatomical Features
• Arteries’ Smooth
Muscles (SM)
• Arterioles’ SM
• Capillary SM sphincters
• Veins’ SM
• Valves in veins
• Large diameter of veins
Specific Regulation
• Local tissue chemistry
effects vessels – self
regulation
• Hormones effect
vessels
• Brain signals heart
rate
• Brain signals vessels
External Help
• Squeegee effect
• Breathing
• Skeletal Muscle
movement
Increased blood flow to disease or damage
• Allergies – histamines are vasodilators
• Vasodilators also released during injury or infection
• More fluids and proteins to a site – not RBCs
• Increased tissue fluid pressure causes swelling and pain
•
•
•
•
Cut
Stomach ache
Cold
Injury
Vascular Diseases
• Hypertension
• Hypotension
• Blockage
• Large and medium arteries, thickening of walls, plaque
• Can rupture and form clots their or elsewhere
• Varicose Veins – valve malfunctions
Angiogenesis and Collateral Arteries
• Occurs in some tissues that
experience moderate ischemia
from blockage or increased
demand
• New arteries form at those
sites (angiogenesis)
• Collateral Arteries
• Pre-existing redundancy
• Angiogenesis over weeks and
months
Circulatory Shock
• Organs can’t get enough O2 from loss of blood flow – tissues die
• Massive blood loss outside the body
• Massive fluid loss (plasma volume, not RBC) from vessels into tissues
• Too many blood vessels “open” at one time
• Allergies, anaphylaxis
• Heart Failure