Blood flows through a network of ____________, ______________, and ______________.
Blood flows through a network of arteries, capillaries, and veins.
All chemical and gaseous exchange between the blood and interstitial fluid takes place across ________________.
capillary walls.
The walls of arteries and veins contain three layers:
the tunica intima, tunica media, and outermost tunica externa.
The arterial system includes the __________________,__________________, and smaller ______________.
large elastic arteries, medium-sized muscular arteries, and smaller arterioles.
The walls of ______________ are usually thicker than the walls of _____________.
The walls of arteries are usually thicker than the walls of veins.
As blood proceeds toward the capillaries, the number of vessels ____________, but the diameter of the individual vessels __________ and the walls become___________________.
increases, decreases, thinner.
___________________________ are the only blood vessels whose walls permit exchange between blood and interstitial fluid.
Capillaries
Capillaries form interconnected networks called
Capillary beds
A _______________________ (a band of smooth muscle) adjusts blood flow into each capillary.
Precapillary sphincter
The arterial system is a _______-pressure system; blood pressure in veins is much _______.
high, lower
___________________ in veins prevent backflow of blood.
Valves
________________ carry blood away from the heart.
Arteries
Vessel wall innermost layer, Lined by endothelium with basement membrane and Surrounded by layer of connective tissue with elastic fibers
Tunica Intima
Vessel wall middle layer has smooth muscle with loose connective tissue containing collagen and elastic fibers. Controls diameter of vessel.
Tunica media
Vessel wall outer layer is the sheath of connective tissue around vessel.
May stabilize and anchor vessel to other tissues
Tunica Externa
Smaller lumen than veins, thicker tunica media with more elastic fiber and smooth muscle.
Arteries
Contraction of arteries; decrease size of the lumen
Vasoconstriction
relaxation of arteries; increase size of the lumen
Vasodilation
First type of arteries leaving the heart,
Have more elastic fibers than smooth muscle fibers
Large, resilient vessels,
Absorb pressure changes readily,
Stretched during systole, elastic fibers recoil during diastole,
Prevent very high pressure during syst
Elastic Arteries
Also called medium-sized arteries or distribution arteries,
Distribute blood to skeletal muscles and internal organs,
Compared to elastic arteries, tunica media contains:
Higher proportion of smooth muscle
Fewer elastic fibers
Examples: external carotid a
Muscular Arteries
Tunica media has only 1-2 layers of smooth muscle,
Diameter changes in response to various stimuli,
Changing diameter alters blood pressure and flow
Arterioles
Tunica interna only, Endothelial cells with basement membrane
Ideal for diffusion between plasma and interstitial fluid:
Thin walls provide short diffusion distance, Small diameter slows flow to increase diffusion rate, Enormous number of capillaries prov
Capillaries
An interconnected network of capillaries,
Entrance to each capillary is regulated by precapillary sphincter, a band of smooth muscle,
Relaxation of sphincter allows for increased flow,
Constriction of sphincter decreases flow,
Occurs in cycles referred to
Capillary Beds
A joining of blood vessels and
May form alternate routes for blood flow
Anastomosis
Bypasses capillary bed, connecting arteriole to venule
Arteriovenous anastomosis
Occurs where arteries fuse before branching into arterioles,
Ensures delivery of blood to key areas such as brain and heart
Arterial anastomosis
Collect blood from tissues and organs and return it to the heart, thin walls. Low blood pressure inside.
Veins
Medium-sized veins in limbs contain __________ that prevent backflow of blood and improve venous return.
Improper functioning _________________ results in destened vessels.
Ex. Varicouse veins or hemorrhoids.
Valves
Sources of peripheral resistance include
vascular resistance, viscosity, and turbulence
Largest pressure gradient,
Difference between pressure at base of aorta and entrance to right atrium
Divided into three components:
?1.Arterial pressure is blood pressure
?2.Capillary pressure
?3.Venous pressure
Circulatory Pressure
Any force that opposes movement
resistance
Circulatory pressure must be high enough to overcome _______________ _______________ __________________.
total peripheral resistance
Steepest drop in pressure exists in arterial network due to high ______________ ________________.
peripheral resistance
Sources of Peripheral resistance
vascular resistance, viscosity, turbulence
Resistance of blood vessels to blood flow,
Largest component of peripheral resistance,
Caused mostly by friction between blood and vessel walls,
Amount of friction depends on length and diameter of vessel
The longer the vessel, the higher the resistance
T
Vascular Resistance
Resistance to flow as result of interactions between molecules and suspended materials in a liquid
Low-viscosity fluids flow at low pressures
High-viscosity fluids flow only under high pressures
Blood viscosity is normally stable
Changes in plasma protein
Viscosity
blood pressure (BP)
(Also called Arterial Pressure) Is the pressure exerted by the blood upon the walls of the blood vessels, especially arteries.
Peak pressure measured during ventricular contraction/systole
Systolic Pressure
Minimum pressure at the end of ventricular relaxation/diastole
Diastolic pressure
Rhythmic pressure oscillation that accompanies each heartbeat.
Pulse
The difference between systolic and diastolic pressures.
Pulse Pressure
Pressure of blood within a capillary bed,
Cause filtration of water and solutes out of bloodstream and into tissues: Some materials reabsorbed into capillaries and Remainder are picked up by lymphatic vessels
Capillary Pressures
Four functions of Capillary exchange
1. Maintains constant communication between plasma and interstitial fluid
2. Speeds distribution of nutrients, hormones, and gases
3. Assists in transport of insoluble molecules
4. Flushes bacterial toxins and other chemicals to lymphatic tissues for body
Mechanisms of Capillary Exchange
Diffusion: Movement of ions or molecules from area of high concentration to area of low concentration
Filtration: Movement of solute due to "push" of water or hydrostatic pressure down fluid pressure gradients, Water is filtered out of capillary by fluid
Gradient is low compared to arterial system,
Large veins provide low resistance, ensuring increase in flow despite low pressure,
Two factors help blood flow overcome gravity when standing:
Muscular compression pushes on outside of veins
Venous valves prev
Venous Pressure
Femoral
...
Great Saphenous
...
external jugular
...
brachial
...
median cubital
...
radial
...
internal jugular
...
superior vena cava
...
Minimum pressure at the end of ventricular relaxation/diastole
Diastolic pressure