Chapter 20 Flashcards
during pressure gradient, what is the venous pressure gradient?
7-13 mm Hg
7-13 mm HG favoring blood movement to the heart
pressure gradient
the flow of blood back to the heart
venous return
venous return is achieved by 5 mechanisms:
- pressure gradient
- gravity
- skeletal muscle pump
- thoracic pump
- cardiac suction
___ drains blood from the head and neck; large veins of head and neck are collapsed
gravity during venous return
___ is when the massaging of veins by muscle action; venous valves prevent back-flow
the skeletal muscle pump during venous return
___ pulls blood from abdominal to thoracic portion of inferior vena cava
the thoracic (respiratory) pump during venous return
___ expands the right atrium and pulls blood from inferior vena cava
cardiac suction
blood pressure in the veins is so __
low
downward motion of the diaphragm increases pressure in the abdominal cavity
inhale
upward motion of diaphragm increase the pressure in the thoracic cavity
exhale
the accumulation of blood
venous pooling
the accumulation of excess fluid in a tissue
edema
occurs when fluid filters into a tissue faster than it is reabsorbed
edema
CORRECT ESSAY: what do you think will happen to the rate of venous return during lifting when the thoracic cavity pressure decreases and remains when breathing is held?
Initially, it speeds up. But if you continue to hold breath it slows down and possibly even stop.
hypertensions, histamine, old age, inactivity, reduced venous return, right or left ventricular failure
increased capillary filtration
albumin deficiency, liver disease, dietary protein deficiency, kidney disease, severe burns
reduced capillary reabsorption
obstructed lymphatic vessels, surgical removal of lymph nodes
obstructed lymphatic drainage
why is the lymphatic system so important?
because it helps drain extra fluid
Why is it problematic when require to stand for long times?
- CO is reduced
- Profusion to the brain is reduced (hypoxic)
- syncope (fainting)
- varicose veins
what starts to build up in the brain during profusion?
carbon dioxide which leads to hydrogen ions
capillaries in ___ engage almost entirely in filtration
renal glomeruli
capillaries of ___ engage almost entirely in reabsorption
pulmonary alveoli
capillaries in ____ shift from reabsorption to filtration when BOP rises; muscles accumulate fluid
exercising muscles
what do traumatized tissues increase?
permeability and filtration
traumatized tissues release ____, ____, and ____
substance P, bradykinin, and histamine
any state in which cardiac output is insufficient to meet the body’s metabolic needs
circulatory shock
caused by inadequate pumping by the heart
cariogenic shock
what causes cariogenic shock?
myocardial infarction (heart attack)
cardiac output is low because too little blood is returning to the heart
low venous return shock (LVR)
low blood volume due to hemorrhage, trauma, burns, dehydration
hypovolemic shock
blood flow impeded when a vain is comprised by a tumor, aneurysm or other cause
obstructed venous return shock
blood accumulates in the limbs instead of returning to the heart; can be due to inactivity or neurogenic shock
venous pooling (vascular) shock
form of venous pooling shock that results from sudden loss of vasomotor tone, allowing the vessels to dilate
neurogenic shock
bacterial toxins trigger vasodilation and increased capillary permeability
septic shock
results from exposure to an antigen to which a person is allergic, such as bee or venom
anaphylactic shock
septic shock and anaphylactic shock both included:
venous pooling, low venous return, capillary permeability and widespread vasodilation
what do antigen-antibody complexes do?
trigger the release of histamine, causes vasodilation and increased capillary permeability
during this degree of shock, homeostasis brings about spontaneous recovery
compensated shock
during this degree of shock, a life threatening positive feedback loop
decompensated shock
what happens in result of decompensated shock?
- low cardiac output - myocardial ischemia & infarction disseminated intravascular coagulation (DIC)
- brainstem ischemica - depressed cardiac & vasomotor centers
brief episodes of cerebral ischemia characterized by temporary dizziness, loss of vision, weakness, paralysis, headache and aphasia
transient ischemia attacks (TIA)
sudden death of brain tissue caused by ischemia
stroke / cerebrovascular accident
myocardial infarction can lead to __ shock
cariogenic
vessels that carry blood away from the heart
arteries
afferent vessels that carry blood back to the heart
veins
vessels that connect the smallest arteries to the smallest veins
capillaries
the walls of arteries and veins are composed of layers called what?
tunics
why are arteries called “resistance vessels”?
because they are are a strong resilient structure
distal to conducting arteries; lead to more specific organs or body regions
distributing artereis
most distal; too variable to be named
small arteries
microscopic, thin-walled vessels that connect the smallest arteriole to the smallest veins; endothelium only
capillaries
these capillaries are endothelial cells joined by tight junctions and separated by intercellular clefts
continous capillaries
continuous capillaries often have ___, cells with elongated tendrils that wrap around the capillary and contract consequently regulating blood flow
pericytes
fenestrated capillaries have ___, which allow for the rapid passage of small molecules but still retain most proteins and larger particles in the blood stream
filtration pores
endothelial cells riddle with patches of filtration pores
fenestrated capillaries
are important in organs that engage in rapid absorption or filtration in the kidneys, endocrine glands, small intestine, and choroid plexuses of the brain
fenestrated capillaries
which capillary conforms to the shape of the surrounding tissue?
sinusoids
which capillaries have large gaps between endothelial cells?
sinusoids
irregular blood filled spaces in the liver, bone marrow, and spleen
sinusoids
capillaries are organized into weblike networks called
capillary beds
in capillary beds supplied with met arterioles, there is a single smooth muscle cell that wraps like a cuff around the opening to each capillary; it acts as a ____ regulating blood flow
pre capillary sphincter
what happens if the pre capillary sphincter is constricted?
capillary bed shuts down
veins are subjected to really ____ blood pressure
low
what happens to veins in a pulmonary circuit?
blood is freshly oxygenated & pulmonary veins traditionally illustrated in red
what happens to veins in systemic circuit?
blood is relatively deoxygenated & systemic veins traditionally illustrated blue
the smallest of the veins
post-capillary venules
receive blood from the post capillary venules
muscular venules
most veins with individual names are in this category of veins
medium veins
many medium veins, especially in the limbs, exhibit inholdings of the tunica internal that meet in the middle of the lumen, forming ___, directed toward the heart.
venous valves
these prevent back flow of blood (vascular incompetence and varicose veins)
venous valves
innermost layer of a vessel wall
tunica interna
middle layer of a vessel wall
tunica media
the outermost layer of a vessel wall
tunica externa
tunica externa contain, __ __, small blood vessels found in the walls of larger vessels; these provide nourishment and waster removal services for the tissue of the larger vessels
vasa vasorum
biggest arteries that are closest to the heart
conducting arteries
blood flows through 2 consecutive capillary networks before returning to the heart
portal system
point of convergence between two blood vessels other than capillaries; bypass capillaries
anastomosis
blood flows from an artery directly into a vein and bypasses capillaries
arteriovenous anastomosis aka shunt
point where one vein empties directly into another
venous anastomoses
point where 2 arteries merge; provides collateral routes of blood supply to the tissue
arterial anastomoses
amount of blood flowing through an organ, tissue, or blood vessel in a given time
flow
flow per given volume or mass of tissue
perfusion
physical principles of blood flow, based mainly on pressure and resistance
hemodynamics
- flow is a matter of pressure vs. resistance: the greater the pressure difference between two points, the greater the flow; the greater the resistance, the less the flow
F=△P/R
how can blood flow be increased?
blood flow can be increased by increasing the pressure gradient or decreasing the resistance
force that the blood exerts against a vessel wall
blood pressure
peak arterial BP attained during ventricular contraction; minimum needed to force brachial artery open against cuff pressure
systolic pressure
minimum arterial BP occurring during ventricular relaxation between heartbeats; recorded at point when brachial artery remains patent between heartbeats
diastolic pressure
what is normal blood pressure?
120/75 mm Hg
the difference between systolic and diastolic pressure; measure of the amount of stress places on smaller vessels by each heartbeat
pulse pressure
the mean pressure you would obtain if you took measurements at several intervals throughout the cardiac cycle; measure of amount of stress placed on the blood vessels throughout the cardiac cycle
mean arterial pressure (MAP)
the increasing stiffness of arteries
arteriosclerosis
the growth of lipid deposits in the arterial walls
atherosclerosis
high blood pressure; chronic resting blood pressure higher than 140/90
hypertension
chronic low blood pressure
hypotension
