nurs 210: chapter 19 - cardiovascular system, blood vessels

systemic circuit

transports oxygenated blood from the left ventricle of heart through aorta and arteries to capillaries

pulmonary circuit

transports deoxygenated blood from right ventricle of heart to the lungs

order of blood flow through each circuit:

pulmonary circuit exchanges CO2 for O2, then returns oxygenated blood to the left atrium to be distributed by systemic circuit

types of blood vessels:

arteries, arterioles, capillaries, venules, veins

blood vessel structures:

tunica interna, tunica media, tunica externa

tunica interna

innermost layer, adjacent to lumen

tunica media

middle layer, smooth muscle, elastic fibers

tunica externa

outermost layer, adjacent to surrounding tissue

arteries

carry blood away from the heart to tissues

walls of arteries are:

elastic, allowing them to absorb pressure created by ventricles of heart as they pump blood into arteries

due to smooth muscle in tunica media:

arteries can regulate their diameter

picture of blood vessel structure:

types of arteries:

elastic, muscular

elastic arteries (conducting arteries)

large diameter, more elastic fibers, less smooth muscle, function as pressure reservoirs

muscular arteries (distributing arteries)

medium diameter, more smooth muscle, fewer elastic fibers, distribute blood to various parts of body

picture of arteries pressure reservoirs:

capillaries

microscopic vessels that usually connect arterioles and venules

capillary walls are composed of:

a single layer of cells and a basement membrane

due to the walls of capillaries being thin:

capillaries permit the exchange of nutrients and wastes between blood and tissue cells

types of capillaries:

continous, fenestrated, sinusoid

continuous capillaries

most common

fenestrated capillaries

filter small molecules (kidneys)

sinusoid capillaries

leaky, allow passage of large molecules and recycled RBC components (liver)

venules

smallest veins that are formed by the union of several capillaries; drain blood from capillaries into veins

veins

formed from the union of several venules and they have thinner tuninca interna and media and thicker tunica externa; veins have less elastic tissue and less smooth muscle than arteries

veins have:

valves, which keep blood moving toward the heart

blood distribution

largest portion of blood is in systemic veins and venules, which are considered blood reservoirs

capillary exchange

substances cross capillary walls by diffusion transcytosis, bulk flow

bulk flow

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

bulk flow occurs from an area of:

higher pressure to an area of lower pressure, which continues as long as pressure difference exist

bulk flow is important for:

regulation of relative volumes of blood and interstitial fluid

filtration is a:

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

blood hydrostastic pressure (BHP) and interstitial fluid osmotic pressure (IFOP) promote:

filtration

reabsorption is a:

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

interstitial fluid hydrostatic pressure (IFHP) and blood colloid osmotic pressure (BCOP) promote:

reabsorption

picture of dynamics of capillary exchange

blood flow

volume of blood that flows through the tissues within period of time (in mL/min)

total blood flow

is cardiac output (CO), the volume of blood that circulates through systemic (or pulmonary) blood vessels each minute; CO = heart rate (HR) x stroke volume (SV)

stroke volume (SV)

amount of blood pumped out of ventricle in one beat

vascular resistance (R)

opposite to blood flow due to friction between blood and walls of blood vessles; higher the R, smaller the blood flow

R is affected by:

size of blood vessel lumen, blood viscosity, and total blood vessel length

size of blood vessel lumen

smaller diameter, higher R

blood viscosity

flowability, thickness of blood; blood is more viscous than water because it contains formed elements (primarily RBCs) and plasma proteins

total blood vessel length

longer the vessel, greater the resistance

resistance opposes:

flow, with small changes in radius having a large effect on resistance to blood flow

vasoconstriction

a decrease blood vessel diameter and decreases blood flow

vasodilation

an increase in blood vessel diameter and increases blood flow

venous return (VR)

volume of blood flowing back to heart through systemic veins

VR is assisted by:

valves, respiratory pump, and skeletal muscle pump

respiratory pump

thoracic cavity action, which inhaling decreases thoracic pressure, and exhaling raises thoracic pressure

skeletal muscle pump

contraction and relaxation of skeletal muscles

contraction of ventricles generates:

BP

BP is influenced by:

cardiac output, blood volume, and vascular resistance

blood flows from:

high pressure (arteries) to low pressure (veins)

larger the pressure gradient:

the greater is blood flow

medulla oblongata contains:

a cardiovascular center, which is a group of neurons that regulate heart rate, contractility, and blood vessel diameter

baroreceptors

important pressure-sensitive sensory neurons that monitor stretching of walls of blood vessels and atria

blood pressure (BP)

measured indirectly by auscultatory methods using sphygmomanometer

systolic pressure

normally less than 120 mm HG; pressure sounds first occur as blood starts to spurt through artery

diastolic pressure

normally less than 80 mm HG; pressure when sounds disappear because artery no longer constrictred, blood flows freely

systolic blood pressure (SBP)

highest pressure during systole (contraction)

diastolic blood pressure (DBP)

lowest pressure during diastole (relaxation)

picture of systolic blood pressure and diastolic blood pressure