Exam 2 Flashcards
arteries
carry blood away fro heart
veins
carry blood toward the heart
capillaries
exchange with air sacs in the lungs and system cells
the hearts 4 chambers
left and right atrium
left and right ventricles
left atrium and right atrium
superior chambers that receive blood and send it to ventricles
left and right ventricles
inferior chambers that pump blood away
which side of the heart has oxygenated blood
left
which side of the heart has deoxygenated blood
right
function of heart valves
prevent back flow to ensure one way blood flow
atrioventricular valves
right (tricuspid) and left (mitral, bicuspid) AV valve are between atrium and ventricle
semilunar valves
pulmonary and aortic semilunar valves are between a ventricle and an arterial trunk
entierity of CV system circulations
- right atrium passes deoxygenated blood from head and neck region forcing valve to open entering into right ventricle
- right ventricle contracts, pulmonary semilunar valve opens sending deoxygenated blood to each lung where gas exchange occurs
- oxygenated blood returns through pulmonary veins into left atrium which contracts causing left AV valve to open and send blood into ventricle
- ventricle contracts sending blood to aortic semilunar valve and through to systemic cells and tissues in the body where more gas exchange occurs causing blood to become deoxygenated again and heads back to right atrium
pulmonary circulation
transports blood from right side of heart to the alveoli of the lungs for gas exchange and back to the left side of the heart
steps of pulmonary circulation
- deoxygenated blood enters right atrium from SVC and IVC and coronary sinus
- blood passes through right AV valve
- enters the right ventricle,
- passes through pulmonary semilunar valve, and
- enters the pulmonary trunk
- blood contrinues through the right and left pulmonary arteries to both lungs, and
- enters pulmonary capillaries of both lungs for gas exchange
- blood is now oxygenated, enters right and left pulmonary veins and is returned
- to the left atrium of heart
systemic circulation
transports blood from left side of heart to the systemic cells of the body for nutrient and gas exchange and back to right side of heart
systemic circulation steps
- oxygenated blood enters the left atrium
- blood passes through left AV valve,
- enters the left ventricle,
- passes through aortic semilunar valve, and
- enters the aorta.
- this blood is distributed by the systemic arteries, and
- enters the systemic capillaries for nutrient and gas exchange
- this blood which is now deoxygenated, ultimately drains into the SVC, IVC, and coronary sinus, and
- enters the right atrium
pericardium
refers to the three layer of the heart
fibrous pericardium
outer layer of pericardium
contains fibrous connective tissue
serves for protection, stabilization of heart, prevention of overfilling of ventricles
serous pericardium
internal layers beneath fibrous pericardium that contains visceral layer, parietal layer, and pericardial cavity
visceral layer
innermost layer
lines and covers the viscera
parietal layer
layer beneath fibrous pericardium
pericardial cavity
filled with cardiac fluid
used for lubrication for pumping of blood consistently
heart wall thickness
ventricle have thicker walls than atria
left ventricle has thicker wall than right
- left must generate high pressure to force blood through systemic circulation; right must pump to nearby lungs
three layers of heart wall
epicardium
myocardium - cardiac muscle
endocardium - continuous w endothelial lining
histology of cardiac muscle
striated muscle
short and branching
intercalated discs
why are cardiac muscles striated
due to arrangement of contractile proteins and overlapping nature of thick and thin filaments
intercalated discs
desmosomes:
proteins that serve to connect two adjacent cells
projections of desmosomes become embedded in cell membrane
gap junctions:
rest on folded sarcolemma and function as proteins that have an opening in the center, ions pass through opening and serve an important role in contraction and activation of muscle, provide electrical current
sarcoplasmic reticulum is a
storage site for calcium
metabolism of cardiac muscle
high demand for energy (extensive blood supply, numerous mitochondria, myoglobin and creatine kinase)
able to use different types of fuel molecules (fatty acids, glucose, lactic acid, amino acids, and ketone bodies)
relies mostly on aerobic metabolism (makes it susceptible to failure when O2 is low, interference w blood flow can cause cell death)
creatine kinase helps
transfer P to give it to ADP creating ATP to combine with creatine
fibrous skeleton
dense irregular connective tissue
-provides structural support at boundary of atria and ventricles
-forms fibrous rings to anchor valves
-provides framework for attachment of cardiac muscle
-acts as electrical insulator preventing ventricles from contracting at same time as atria
coronary circulation
delivers blood to heart’s thick wall
coronary arteries transport oxygenated blood to heart wall
coronary veins transport deoxygenated blood away from heart wall toward right atrium
arteries involved in coronary circulation
right coronary artery
posterior IV artery
right marginal artery
left coronary artery
circumflex artery
anterior IV artery
conduction system
initiates and conducts electrical events to ensure proper timing of contractions
-specialized cardiac muscle cells that have action potentials but do not contract
-its activity is influenced by autonomic nervous system
sinoatrial nodes
SA or pacemaker
tissue in posterior wall of right atrium that
sets pace for generating action potential
atrioventricular node
AV node
impulse is conducted along IV septum where it reaches AV bundle (bundle of His) and then along bundle it splits into right and left AV bundles and travels down to the apex of heart and follows right and left AV bundles as they become Purkinjie fibers
cardiac center of medulla oblongata
contains cardioacceleratory and cardioinhibitory centers
recieves signals from baroreceptors and chemoreceptors in CV system
sends signals via sympathetic and parasympathetic pathways
modifieds cardiac activity (doesn’t initiate it)
-influences heart rate and force of contraction
parasympathetic innervation and heart rate
decreases
sympathetic innervation and heart rate
increases heart rate and force of contraction
physiologic processes associated with heart contraction
conduction system
1. initiation : SA node initiates action potential
2. spread of action potential : an action potential is propagated throughout the atria and the conduction system
cardiac muscle cells
1. action potential : action potential is propagated across the sarcolemma of cardiac muscle cells
2. muscle contraction : thin filaments slide past thick filaments and sarcomeres shorten within cardiac muscle cells
SA node cellular activity
RMP of -60 mV
Na/K pumps and Ca2+ pumps along membrane of nodal cell help actively transport sodium out of cell and potassium into cell so concentration of sodium is greater outside than inside
activity of SA node
- RMP at -60mV DEPOLARIZATION (becomes more positive)
- increase in mV ^ depolarization
- -40mV for threshold voltage (repolarization)
- when cell is negative enough it causes action potential
steps in generating action potential of SA node
- reaching threshold
- slow voltage gated Na+ channels open, inflow of Na+ changes MP from -60mV to -40mV - depolarization
- fast voltage gated Ca2+ channels open, inflow of Ca2+ changes MP from -40mV to just above 0 - repolarization
- fast voltage gated Ca2+ channels close. voltage gated K+ channels open allowing K+ outflow. MP returns to RMP -60mV and K+ channels close
initiation and spread of action potential through cardiac conduction system
- action potential is generated at SA node. it spreads via gap junctions between cardiac muscle cells throughout the atria to the AV node
- action potential is delayed at AV node before it passes to the AV bundle within the interventricular septum
- the AV bundle conducts the action potential to the left and right bundle branches and then to the purkinje fibers
- the action potential is spread via gap junctions between cardiac muscle cells throughout the ventricles
cardiac muscle cells RMP
-90 mV
at RMP potential in cardiac muscle cells, which pump remains closed
all pumps remain closed so concentration gradient for ions remains stable
electrical events of cardiac muscle cells
- depolarization - starts at -90mV and then has rapid increase to +30mV
- plateau - almost no change for that period of time until cell repolarizes it is refractory to further stimuli, want to delay to prevent hazard from normal synchronous behavior of heart
- repolarization
steps of electrical events of cardiac muscle cells
- depolarization: fast voltage gated Na+ channels open and Na+ rapidly enters the cell, reversing the polarity from negative to positive (-90mV to +30mV). these channels then close.
- plateau: voltage gated K+ channels open and K+ flows out of cardiac muscle cells. Slow voltage gated Ca2+ channels open and Ca2+ enters the cell with no electrical change and the depolarized state is maintained
- repolarization: voltage gated Ca2+ channels close, voltage gated K+ channels remain open and K+ moves out of the cardiac muscle cell, and polarity is reversed from positive to negative (+30mV - -90mV)
electrocardiogram
ECG/EKG
skin electrodes detect electrical signals of cardiac mucles cells
common diagnostic tool
p wave
reflects electrical changes of atrial depolarization originating in SA node
QRS complex
electrical changes associated with ventricular depolarization
atria simultaneously repolarizing
t wave
electrical change associated with ventricular repolarization
what two segments of ECG correspond to plateau phase of cardiac action potentials
P-Q segment and S-T segment
p-q segment
associated with atrial cell’s plateau
atria are contracting
s-t segment
associated with ventricular plateau
ventricles are contracting
P-R interval
time from beginning of P wave to beginning of QRS deflection
from atrial depolarization to beginning of ventricular depolarization
time to transmit action potential through entire conduction system
Q-T interval
time from beginning of QRS to end of T wave
reflects the time of ventricular action potentials
length depends upon heart rate
cardiac cycle
all events in heart from the start of one heart beat to start of the next
- systole (contraction) and diastole (relaxation)
contraction _______ pressure; relaxation _______ it
increases;decreases
blood moves down pressure gradient (high to low)
valves ensure blood flow is forward (closes to prevent backflow)
what is the most important driving force in cardiac cycle
ventricular activity
ventricular contraction
raises ventricular pressure
AV valves pushed closed
semilunar valves pushed open and blood ejected to artery
ventricular relaxation
lowers ventricular pressure
semilunar valves close (no pressure from below keeping them open)
AV valves open (no pressure pushing them closed)
phases of cardiac cycle
- atrial contraction and ventricular filling
- isovolumetric contraction
- ventricular ejection
- isovolumetric relaxation
- atrial relaxation and ventricular filling
atrial contraction and ventricular filling (1)
atria CONTRACT , ventricles RELAX
ventricular pressure is less than BOTH atrial pressure and arterial trunk pressure
AV valves OPEN , semilunar valves CLOSED
isovolumetric contraction (2)
atria RELAX , ventricles RELAX
ventricular pressure is greater than atrial pressure but NOT greater than arterial pressure
AV valves CLOSED , semilunar valves CLOSED
ventricular ejection (3)
atria RELAX , ventricles CONTRACT
ventricular pressure is greater than BOTH atrial pressure and arterial pressure
AV valves CLOSED , semilunar valves OPEN
isovolumetric relaxation (4)
atria RELAX , ventricles RELAX
ventricular pressure greater than atrial pressure but NOT arterial trunk pressure
AV valves CLOSED , semilunar valves CLOSED
atrial relaxation and ventricular filling (5)
atria RELAX , ventricles RELAX
ventricular pressure is LESS than BOTH atrial pressure and arterial trunk pressure
AV valves OPEN , semilunar valves CLOSED
cardiac output
amount of blood pumped by a SINGLE ventricle in one minute (L/min)
measure of effectiveness of CV system
increases in healthy individuals during exercise
determined by HR (bpm) and stroke volume (SV - amount of blood ejected per beat)
HR x SV = CO
stroke volume
amount of blood ejected in one beat from ONE ventricle
influenced by venous return, inotropic agents, and afterload
venous return
volume of blood returned to the heart
directly related to stroke volume
determines amount of ventricular blood prior to contraction (end-diastolic volume (EDV))
volume determines preload
- pressure stretching heart wall before shortening
frank starling law (starlings law)
as EDV increases, the greater stretch of heart wall results in more optimal overlap of thick and thin filaments
heart contracts more forcefully when filled with more blood so SV increases
venous return may be increased by
increased venous pressure or increased time to fill
-venous pressure increases during exercise as muscles squeeze veins
-time available to fill increases with slower heart rate (high-caliber athletes w strong hearts)
venous return steps
volume of blood return to heart per unit time
1. increased venous return (occurs w greater venous pressure or slower heart rate)
2. increases stretch of heart wall (preload), which results in greater overlap of thick and thin filaments within the sarcomeres of the myocardium
3. additional corssbridges form, and ventricles contract with greater force
4. stroke volume increases
opposite occurs in smaller venous return (rapid heart rate , hemorrhage
what variable influence stroke volume
venous return
inotropic agents
afterload
inotropic agents
substances that act on myocardium to alter contractility
1. positive inotropic agents (e.g., stimulation by sympathetic nervous system)
2. increased Ca2+ levels in sarcoplasm results in greater binding of Ca2+ to troponin of thin filaments within sarcomeres of myocardium
3. additional crossbridges form, and ventricles contract with greater force
4. stroke volume increases
oppositive is seen w negative inotropic agents (e.g. calcium channel blockers)
afterload
resistance in arteries to ejection of blood
1. atherosclerosis, which is deposition of plaque on the inner lining of arteries, is typically only a factor as we age
2. arteries become more narrow in diameter
3. increases the resistance to pump blood into the arteries
4. stroke volume DECREASES
chronotropic agents
alter SA node and AV node activity
positive and negative agents
positive -increase HR
negative - decrease HR
increase or decrease in HR directly impacts cardiac output
venous return is directly correlated with
stroke volume which directly affects cardiac output
inotropic agents contain
positive agents - increase SV
negative agents - decrease SV
increase or decrease in stroke volume impacts CO
afterload is INVERSELY correlated with
stroke volume which is directly correlated with CO
fetal vs neonatal circulation
foramen ovale passes most of blood through right atrium to left
some falls into right ventricle and then oxygenated blood will go to pulmonary trunk and pass through ductus arterioles
ductus arteriosis connects aorta and pulmonary trunk
deliver oxygen to developing lung tissue
three types of blood vessels
arteries
capillaries
veins
tunica intima
consists of endothelium and subendothelial layer
endothelium- single layer of endothelial cells
subendothelial - loose connectie tissue containing collagen fibers
tunica media
composed of smooth muscle (thick layer)
as they contract, it influences diameter of lumen
contains elastic laminae, and elastic fiber to stretch and recoil
tunica externa
primarily loose connective tissue
small network of vessels is called vasa vasorum with represent blood supply to components of the vessel
artery branching
brnach into smaller vessels extending from heart
decrease in lumen diamter
decrease in elastic fibers
increase in relative amount of smooth muscle
composed of : elastic arteries, muscualr arteries, arterioles
capillary characteristics
small vessels connecting arterioles to venules
average length = 1mm; diameter = 8 to 10 micrometers
rouleau
wall consists of endothelial layer on basement membrane
thin wall and small diameter are optimal for exchange between blood and tissue fluid
three types: continuous, fenestrated, and sinusoid
continuous cappilaries
endothelial cells form a continuous lining
tight junctions connect cells but don’t form a complete seal
-intercellular clefts are gaps between endothelial cells of capillary wall
-large particles (cells and proteins) cannot pass but smaller molecules (glucose) can
where are continous capillaries found
muscle, skin, lungs, CNS
fenestrated capillaries
endothelial cells form a continuous lining but the cells have fenestrations (pores)
- allow movement of smaller plasma proteins
found in areas where much fluid transport happens
where are fenestrated capillaries found
intestinal capillaries absorbing nutrients
kidney capillaries filtering blood to form urine
sinusoids (discontinuous capillaries
endothelial cells form an incomplete lining with large gaps
basement mebmrane is incomplete or absent
openings allow transport of large substances (formed elements, large proteins)
where are sinusoid capillaries found
bone marrow, spleen, liver, and some endocrine glands
venules
smallest veins - diameters of 8-100 micrometers
companion vessels w arterioles
smallest venules are postcapillary venules
largest venules have all three tunics
merge to form veins
small and medium sized veins
companion vessels with muscular arteries
largest veins
travel with elastic arteries
most veins of these sizes have
numerous valves that help prevent blood from pooling in limbs; ensure blood flow toward the heart
valves made of tunica intima and elastic and collagen fibers
what is similar to the valves of veins
semilunar valves of heart
elastic arteries function
stretch to accomodate the pulses of blood ejected from the heart and recoil to propel blood through the arteries
muscular arteries function
regulate distribution of blood through vasoconstriction and vasodilation
arterioles function
regulate blood distribution through vasoconstriction and vasodilation
capillaries function
recieve blood from arterioles and allow for exchange between the blood and cells
precapillary sphincters
regulate blood flow through capillary beds
when contracted, it closes blood flow
when relaxed, it allows blood flow
least to most permeable capillaries
continuous
fenestrated
sinusoid
veins function
systemic veins transport deoxygenated blood towards the heart
large veins function
serve as a blood reservoir (55% of blood)
small/medium veins
receive blood from venules; blood drains into small/medium veins and then into large veins
venules function
receive blood from capillaries
what is unique about veins
they carry valves that help one way blood flow
bulk flow
fluids flow down pressure gradient
large amounts of fluids and dissolved substances
movement direction depends on net pressure of opposing forces (hydrostatic vs osmotic pressure)
filtration
fluid moves out of blood
small solutes flow easily through capillary’s openings
large solutes blocked
occurs on ARTERIAL end of capillary
reabsorption
fluid moves back into blood
occurs on venous end
hydrostatic pressure
force exerted by a fluid
blood hydrostatic pressure (HPb)
force exerted per unit area by blood vessel on wall
promotes filtration from capillary
colloid osmotic pressure
the pull on water due to presence of protein solutes
blood colloid osmotic pressure (COPb)
draws fluid into blood due to blood proteins (albumins)
promotes reabsorption (opposes the dominant hydrostatic pressure)
clinically called oncotic pressure
arterial end
filtration
blood hydrostatic pressure is GREATER (>) than osmotic pressure
net pressure out
fluid is forced out of the blood vessel
venous end
reabsorption
osmotic pressure is GREATER (>) than blood hydrostatic pressure
net pressure in
fluid drawn into the blood vessel
net filtration pressure during filtration
net hydrostatic (HP) (35 mm Hg) - net colloid (COP) (21 mm Hg) = net filtration (NFP) (14 mm Hg)
net filtration pressure during reabsorption
net hydrostatic (HP) (16 mm Hg) - net colloid (COP) (21 mm Hg) = net filtration (NFP) (-5 mm Hg)
blood pressure
force of blood against vessel wall
blood pressure gradient
change in pressure from one end of vessel to other
propels blood through vessels
pressure is highest in arteries and lowest in veins
arterial blood pressure
blood flow in arteries pulses with cardiac cycle
systolic pressure
occurs when ventricles contract (systole)
highest pressure generated in arteries (they are stretched)
recorded as the upper number of blood pressure ratio
120 in 120/80
diastolic pressure
occurs when ventricles relax (diastole)
lowest pressure generated in arteries (they recoil)
recorded as lower number of blood pressure ratio
80 in 120/80 mm Hg
pulse pressure
pressure in arteries added by heart contraction
equals the difference between systolic and diastolic pressure
(120 -80 = 40 mmHg)
allows for palpation of a throbbing pulse in elastic and muscular arteries
influenced by elasticity and recoil of arteries (tend to decline with age and disease
blood pressure gradient in the systemic circulation
systemic gradient is difference between pressure in arteries near heart and IVC
mean blood pressure in arteries = 93 mm Hg
blood pressure in vena cava = 0
blood pressure gradient 93
driving force to move blood through vasculature (increase in gradient increases total blood flow)
what increases blood pressure gradient
cardiac output
resistance
friction blood encounters
due to contact between blood and vessel wall
opposes blood flow
peripheral resistance - resistance of blood in blood vessels
what affects resistance of blood
viscosity, vessel length, lumen size
total blood flow approximately equals
pressure gradient (established by the heart) / resistance (experienced by blood as it moves through the vessels)
factors that increase total blood flow
increase in cardiac output
less resistance caused by vasodialation
reduction in vessel length
decrease in blood viscosity
factors that decrease total blood flow
decrease in cardiac output
increased resistance due to vasoconstriction
increase in vessel length
increase in blood viscosity
anything that increases pressure gradient …
increases blood flow
anything that increases resistance …
decreases blood flow
skeletal muscle pump
there is issues with propelling blood back to heart because there isn’t enough pressure to beat the force of gravity
so the skeletal muscle pump compresses venous walls and blood is going to go in both direction where the valves on one side is going to close and build pressure for the valve on the other end to open, pushing blood towards the heart
respiratory pump
aids in increasing venous pressure and propelling it through the heart
promotes the return o venous blood to abdominopelivc and thoracic cavity
has to do with pressure changes in inspiration and expiration
inspiration
thoracic pressure decreases
atrial pressure decreases
venous return increases
stroke volume decreases
expiration
thoracic pressure increases
right atrial pressure increases
venous return decreases
stroke volume increases
blood pressure depends on
cardiac output, resistance, blood volume ( regulated by nervous and endocrine systems )
-must be kept in proper range to be high enough to maintain tissue perfusion but not so high as to damage vessels
autonomic reflexes regulate blood pressure …
short term
involves nuclei in medulla oblongata
quickly adjust cardiac output, resistance, or both
meet momentary pressure needs (standing up from supine position)
cardiovascular center of medulla
contains two autonomic nuclei
- cardiac center
- vasomotor center
cardiac center
influences blood pressure by influencing cardiac output
vasomotor center
influences blood pressure by influencing vessel diameter (vessel constriction influences resistance)
baroreceptors
nerve endings that respond to stretch of vessel wall
-firing rate changes with blood pressure changes
-located in tunica externa of aortic arch and carotid sinuses
aortic arch baroreceptors
transmit signals to cardiovascular center through vagus nerve (CN X)
-important in regulating systemic blood pressure
carotid sinuses baroreceptors
transmit nerve signals to cardiovascular center via glossopharyngeal nerve (CN IX)
-monitor blood pressure in head, neck (vessels that serve the brain)
-more sensitive to blood pressure changes than aortic arch receptors
autonomic reflexes for blood pressure
are baroreceptor reflexes initiated by decrease or increase in blood pressure
if blood pressure decreases…
vessel stretch declines and baroreceptor firing rate DECREASES
this activates the cardioacceleratory center to stimulate the sympathetic pathways to increase cardiac output
it inhibits the cardioinhibitory center to minimize parasympathetic activity
activates the vasomotor center to stimulate sympathetic pathways to increase vasoconstriction; parasympathetic stimulation inhibited
the increase in cardiac output and resistance raises blood pressure
if blood pressure increases
vessel stretch and baroreceptor firing rate increase
causes the cardioacceleratory center to send fewer signals along sympathetic pathways
it stimulates the cardioinhibitory center to activate parasympathetic pathways to SA and AV nodes of the heart
causes vasomotor center to send fewer signals along the sympathetic pathways to blood vessels (vasodilation); parasympathetic output is enhanced
the decrease in cardiac output and resistance lowers blood pressure
baroreceptor reflexes are best for
quick changes in BP, but are ineffective for long-term BP regulation
chemoreceptor reflexes also..
influence blood pressure
stimulation of chemoreceptors bring about negative feedback reflexes to return blood chemistry to normal
-responses in respiratory and CV systems
main peripheral chemoreceptors are in
aortic and carotid bodies
both send input into cardiovascular center
aortic bodies are
in aortic arch and send signals via vagus nerve
carotid bodies are
at bifurcation of common carotid artery and send signals via glossopharyngeal nerve
what stimulates chemoreceptors
high carbon dioxide, low pH, and very low oxygen
chemoreceptor firing stimulates
vasomotor center which
-increases nerve signals along sympathetic pathways to vessels
-shifts blood from venous reservoirs to increase venous return
-raises BP and increases blood flow (including pulmonary)
allows for increased respiratory gas exchange in lunsg
hormones also
regulate BP
-epinephrine and norepinephrine work w sympathetic nervous system
-angiotensin II, antidiuretic hormone, aldosterone, and atrial natriuretic peptide also have effects
influence pressure through effects on resistance, blood volume or both
renin - angiotensin system
- kidney receptors detect low blood pressure or are stimulated by the sympathetic division; renin enzyme is released
- renin converts angiotensinogen into angiotensin I
- ACE converts angiotensin I into angiotensin II
- angiotensin II increases blood pressure by
- causing vasoconstriction
-stimulating thirst center
- decreasing urine formation
angiotensin-converting enzyme (ACE) is
anchored into the internal walls in capillaries especially capillaries in lungs
angiotensinogen is
a plasma protein that is continuously produced by the liver and circulates within the blood
aldosterone helps
maintain blood volume and pressure
-released from adrenal cortex
-release triggered by several stimuli including angiotensin II
-increased absorption of sodium ions and water in the kidney
Decreases urine output
antidiuretic hormone (ADH) helps maintain and elevate
blood pressure
released from posterior pituitary
release triggered by nerve signals from hypothalamus
- stimulated by increased blood concentration or angiotensin II
adh effects
increases water reabsorption in kidney (less fluid loss, maintaining blood volume)
simtulates thirst center to increase fluid intake (raising blood volume)
in large amounts it causes vasoconstriction (increasing resistance and pressure)
- the reason ADH sometimes termed vasopressin
atrial natiuretic peptide (ANP) decreases
blood pressure
released from atria of heart when walls are stretched by high blood volume
stimulates vasodilation (decreases peripheral resistance)
increases urine output (lowers blood volume)
mechanisms for blood pressure homeostasis involve
-cardiac output
-resistance
- blood volume
these variable directly relate to pressure: increasing any of them will raise blood pressure
factors that regulate blood pressure
cardiac output
peripheral resistance
blood volume
cardiac output on regulate blood pressure
cardiac output is the volume of blood pumped per minute
CO is a function of heart rate (HR) and stroke volume (SV) : CO= HR x SV
heart rate and cardiac output
increased heart rate increases cardiac output and blood pressure
decreased heart rate decreases cardiac output and blood pressure
stroke volume and heart rate
increased stroke volume increases cardiac output and blood pressure
decreased stroke volume decreases cardiac output and blood pressure
peripheral resistance and blood pressure
peripheral resistance is the opposition to flow of blood in vessels, and is a function of vessel radius, vessel length, and blood viscosity
vessel radius and blood pressure
vasoconstriction narrows vessel and forces blood through a narrower lumen increasing peripheral resistance and blood pressure
vasodilation widens vessel, decreasing peripheral resistance and blood pressure
vessel length and blood pressure
longer vessels increase peripheral resistance, which raises blood pressure
shorter vessels decrease peripheral resistance, which lowers blood pressure
blood viscosity and blood pressure
increased blood viscosity increases peripheral resistance and blood pressure
decreased blood viscosity decreases peripheral resistance and blood pressure
functions of lymphatic system
transport and house lymphocytes and other immune cells
return excess fluid in body tissues to blood to maintain blood volume
components of lymphatic system
lymph vessels, lymphatic tissues and organs, lymph
lymph
fluid transported within lymph vessels
characteristics of lymph
some fluid leaves blood capillaries and is not reabsorbed by them which is moved into lymphatic capillaries
components of lymph
water
dissolved solutes
small amounts of protein
(sometimes cell debris, pathogens, or cancer cells)
lymphatic capillaries
contain anchoring filaments that are attached to outside wall of capillary that anchors and stabilizes position of lymphatic capillary
hydrostatic pressure is directing fluid from intertwined blood vessels into the capillary wall
what role do the SMP and RP take with lymphatic vessels
SMP and RP both cause compression of thin lymphatic vessels and drive fluid back towards the chest
right lymphatic duct
drains right arm right side of chest and neck
what lymphatic duct drains most of the body
thoracic duct
primary lymphatic structures are
red bone marrow and the thymus
involved in formation and maturation of lymphocytes
secondary lymphatic structures
include lymph nodes, spleen, tonsils, and lymphatic nodules, includes MALT (mucosa-associated lymphatic tissue)
do not form lymphocytes but house them and other immune cells
sites of immune response initiation
red bone marrow
located between trabeculae of spongy bone
site of homeopoiesis : production of blood’s formed elements (T and B lymphocytes)
where is red bone marrow found in adults
in flat bones of skull, ribs, and sternum, vertebrae, ossa coxae, heads of humerus and femur
all formed elements except ______ leave the bone marrow and _________________
T lymphocytes ; directly enter and circulate the blood
T-lymphocytes mature in the
thymus prior to circulating in the blood
thymus
involved in T- lymphocyte maturation
located in mediastinum
larger in children than adults (grows until puberty, then regresses: replaced by adipose tissue)
consists of 2 thymic lobes surrounded by connective tissue capsule
trabeculae of capsules within thymus are subdivided into
lobules
each lobule has outer cortex and inner medulla regions
both regions contain lymphatic cells and epithelial tissue
cortex of thymus contains
immature T lymphocytes
medulla of thymus contains
mature t lymphocytes
lymph nodes
filter lymph and remove unwanted substances
small oval encapsulated structures located along deep and superficial pathways of lymph vessels
occur in clusters receiving lymph from body regions
what are the 3 clusters of lymph nodes
cervical
axillary
inguinal
cervical lymph nodes
receive lymph from head and neck
axillary lymph nodes
receive lymph from breast, axilla, and arms
inguinal lymph nodes
receive lymph from legs, and pelvis
components of lymph node
afferent and efferent vessels
capsule
outer cortex
inner medulla
hilum
afferent lymphatic vessicles
bring lymph to node
efferent vessel
drains a lymph node
efferent vessels are located
at hilum (involuted portion of node)
what encloses the lymph node
dense connective tissue capsule
trabeculae of capsule subdivides node into compartments
lymph flow through lymph nodes
lymph enters through several afferent vessels which creates pressure to push it through node to the single exit vessel
lymph is monitored for presence of foreign material
-macrophages remove foreign debris
-lymphocytes may initiate immune response (proliferate especially germinal centers, can cause enlarged nodes that can be palpated in neck and axilla)
lymph exists node through effect vessel
** may enter nearby lymph node within the cluster of nodes **
spleen
largest lymphatic organ
located in upper left abdominal quadrant
contains white pulp and red pulp tissues
white pulp
clusters of T and B lymphocytes and macrophages around central artery
red pulp
contains erythrocytes platelets macrophages and B lymphocytes
storage site for eryhtrocytes and platelets
what percentage of platelets are not actively circulating
30%
they are stored in spleen
hypoxia (low blood oxygen) stimulates the spleen to
secrete erythrocytes to increase blood oxygen levels
each region of white pulp contains
a central artery
the spleen…
filters and monitors blood (not lymph)
white pulp monitors for
foreign materials and bacteria
macrophages lining sinusoids of red pulp…
remove particles, phagocytize bacteria, debris, defective erythrocytes, and platelets
summary of functions of spleen
remove foreign particles
clear defective erythrocytes and platelets
store erythrocytes and platelets
in first 5 months of fetal life the spleen makes
blood cells
this can be reactivated under certain conditions (extramedullary hemopoiesis, some hematologic disorders)
tonsils
immune surveillance of inhaled and ingested substances
contain lymphatic nodules (some w germinal centers)
tonsillar crypts (invaginations that trap material)
types of tonsils
pharyngeal
palatine
lingual
pharyngeal tonsil
in nasopharynx
called adenoids when enlarged
palatine tonsils
in posterolateral oral cavity
lingual tonsils
along posterior 1/3 of tongue
lymphatic nodules summary
clusters of lymphatic cells w some ECM (not completely surrounded by connective tissue capsule
scattered nodules termed diffuse lymphatic tissue
found in every body organ
help defend against infection
in some areas, they group together to form larger structures (MALT)
MALT
mucosa-associated lymphatic tissue
located in GI, respiratory, genital, and urinary tracts
help defend against foreign substances
