Chapter 15: The Cardiovascular System: Blood Vessels and Hemodynamics

BIOS 213

Five main types of blood vessels:

arteries, arterioles, capillaries, venules, veins

arteries -

blood vessels that carry blood away from the heart

large diameter arteries have thick walls composed of several layers of tissue: 

endothelium, basement membrane, smooth muscle, fibrous connective tissue, and a high portion of elastic connective tissue

arteries have more ___ than veins

muscle

elastic arteries function:

pressure reservoir

elastic arteries have the most elastic tissue in the ___

tunica media

elastic arteries function as pressure reservoirs that:

stretch during ventriculare systole, momentarily storing some of the pressure generated by the contraction, and then recoil during ventricular relaxation, releasing stored pressure

the largest elastic arteries include:

aorta and pulmonary trunk

Arteries that are closer to the heart:

aorta, pulmonary trunk, iliac

muscular arteries -

medium sized arteries that contain much more smooth muscle and less elastic connective tissue

muscular arteries distribute blood to:

organs of the body

as a muscular artery enters an organ, it branches into many:

arterioles

arterioles -

abundant microscopic vessels that deliver blood to capillaries

arterioles regulate blood flow to:

capillaries

arterioles can:

constrict or dilate

the walls of large arterioles consist of:

endothelium, basement membrane, smooth muscle, small amount of fibrous connective tissue

the walls of smaller arterioles consist of:

endothelium and basement membrane surrounded by an incomplete layer of smooth muscle fibers

arterioles are known as:

resistance vessels

arterioles can affect blood flow resistance by:

changing diameter

vasoconstriction:

increases resistance and blood pressure

vasodilation:

decreases resistance and blood pressure

arterioles, capillaries, and venules are collectively known as:

the microcirculation

capillaries -

microscopic vessels that contain arterioles to venules

capillaries are known as:

exchange vessels

capillaries serve as the main sites of:

nutrient and waste exchange between the blood and tissue cells

capillaries are able to function as sites of nutrient and waste exchange because:

capillary walls are very thin + they contain pores

exchange of materials occurs only through:

walls of capillaries and postcapillary venules

Capillaries form:

extensive branching networks that increase surface area available for rapid exchange of materials → capillary beds

capillary bed -

a network of 10 - 100 capillaries that form at a tissue

capillaries branch directly from a(n) ___ and then rejoin to form a(n) ___

arteriole; postcapillary venule

capillaries can also branch from and reconnect with a:

metarteriole

metarteriole -

branch from a capillary that extends from the arteriole to a venule

metarteriole function:

serves as a shut that allows blood to bypass the capillaries

precapillary sphincters -

rings of smooth muscle fiber at the junctions where a capillary branches from the arteriole or a metarteriole

precapillary sphincter function:

control the flow of blood through the capillaries

Three types of capillaries:

continuous, fenestrated, and sinusoids

continuous capillaries -

continuous tube interrupted by intercellular clefts formed cell plasma

intercellular cleft -

slit-shaped pores that are located between neighboring endothelial cells

continuous capillaries are permeable to:

H₂0, small solutes, glucose

continuous capillaries are found in:

muscle, connective tissue, lungs, and brain

continuous capillaries are:

most abundant

fenestrated capillaries -

capillaries that contain pores called fenestrations

fenestrations -

cylindrical pores that extend through the endothelial cells

fenestrated capillaries are ___ permeable than continuous capillaries

more

fenestrated capillaires have a higher permeability to:

water and small solutes

fenestrated capillaries are found in:

kidneys, small intestine, endocrine organs

sinusoids -

wider and more winding capillaries that contain large fenestrations

sinusoids have the ___ permeability

highest

sinusoids are permeable to:

plasma proteins and bloods cells + water and small solutes

sinusoids are found in:

bone marrow, spleen, and liver

venules -

microscopic veins that drain capillary blood and begin the return of blood back toward the heart

venules consist of:

endothelium surrounds by basement membrane

venules are:

very porous

postcapillary venules function:

sites of exchange of nutrients and wastes and leukocyte emigration

postcapillary venules merge to form large venules, which aquire:

one or two layers of smooth muscle and a thin layer of fibrous connective tissue

veins -

carry blood from tissues back to the heart

veins contain:

endothelium, basement membrane, fibrous connective tissues, less smooth muscle, and less elastic connective tissues

blood return to the heart is aided by:

valves and pumps

valves -

thin folds of endothelium and connective tissue that form flaplike cusps

valves aid movement of venous blood to the heart by:

preventing backflow of blood

leaky venous valves can cause:

veins to become dialted and twisted in appearance → varicose veins (varices)

skeletal muscle pump -

the contraction of skeletal muscles in the lower limbs that helps boost movement of venous blood back to the heart

respiratory pump -

decreased thoracic pressure and increased abdominal pressure pushes blood in abdominal veins into thoracic veins and towards atrium

venules and veins both function as:

blood reservoirs

blood reservoirs -

areas of excess blood volume from which that blood can be diverted quickly if the need arises

at rest, ____ of blood is in veins and venules

60-64%

when exercising or sympathetic response, venous constriction:

forces more blood into arteries and arterioles

Mission of the entire cardiovascular system:

keep blood flowing through capillaries to allow capillary exchange

capillary exchange -

the movement of substances between blood and interstitial fluid

the most important method of capillary exchange is:

simple diffusio

substance(s) exchanged in capillary exchange:

all of the above

These substances can enter and leave capillaries through simple diffusion:

O₂, CO₂, glucose, amino acids, hormones

substances in blood or interstitual fluid can cross the walls of a capillary by diffusion through:

endothelial cells of by diffusing through intercellular clefts or fenestrations

substances that can pass across capillary wall directly through the lipid bilayer of endothelial cell plasma membranes:

lipid-soluble (nonpolar) substances: O₂, CO₂, and steroid hormones

substances that pass through intercellular clefts or fenestrations:

small, water-soluble (polar) substances: ions, glucose, and amino acids

water can diffuse across capillary walls by:

moving through intercellular clefts or fenestrations, or through endothelial cell plasma membranes

erythrocytes and most plasma proteins ___ move through capillary walls

cannot

transcytosis -

small quantity of material crosses capillary walls by being enclosed within tiny vesicles that first enter endothelial cells, by endocytosis and exit by exocytosis

transcytosis exports:

large, lipid-insoluble molecules

bulk flow -

passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction

bulk flow occurs from an area of ___ pressure to an area of ___ pressure

high; low

diffusion is more important for _____ between blood and intestitual fluid, but bulk flow is more important for regulation of the _____ of blood and interstitial fluid

solute exchange; relative volumes

filtration -

pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid

reabsorption -

pressure-driven movement from interstitial fluid into blood capillaries

startling forces -

bulk flow across blood capillary walls is determined by four pressures: capillary hydrostatic pressure, interstitial fluid hydrostatic pressure, plasma colloid osmotic pressure, interstitial fluid colloid osmotic pressure

capillary hydrostatic pressure -

pressure that water in blood exerts against the inner surface of capillary walls

capillary hydrostatic pressure promotes:

filtration by forcing fluid out of capillaries into interstitial fluid

interstitial fluid hydrostatic pressure -

pressure that water in interstitial fluid exerts against the outer surface of capillary walls

interstitial fluid hydrostatic pressure promotes:

reabsorption by forcing fluid from interstitial spaces back into capillaries

plasma colloid osmotic pressure -

pressure due to the colloidal suspension in blood of plasma proteins, which are unable to move across capillary walls

plasma colloid osmotic pressure promotes:

reabsorption by causing osmosis of fluid from the interstitial spaces into the capillaries

interstitial fluid colloid osmotic pressure -

pressure due to the presence of plasma proteins in interstitial fluid

interstitial fluid colloid osmotic pressure promotes:

filtration by causing osmosis of fluid from blood into the interstitial spaces

lymphatic system -

picks up excess fluid filtered by the capillaries

the lymphatic system consists of:

lymph, lymphatic vessels, lymph nodes, bone marrow, thymus, spleen, tonsils, Peyer’s patches of the small intestine, appendix

Lymphatic system functions:

drains excess interstitial fluid, returns filtered plasma proteins back to the blood, carries out immune responses, and transports dietary lipids

increased capillary pressure or an increase of capillary osmotic pressure can cause:

excess fluid to be reabsorbed in interstitial space due to overwhelmed lymphatic system→ edema

a functional lymphatic system prevents edema by:

collecting this excess fluid, including proteins and other macromolecules, and returning it to the bloodstream

Blood flow -

volume of blood that flows through any tissue in a given time

blood flow depends on:

pressure gradient