lecture 14 Flashcards
five main types of blood vessels
arteries
arterioles
capillaries
venules
veins
layers of blood vessels are called
tunics
tunica interna
endothelial lining in direct contact with blood
tunica media
intermediate layer of smooth muscle and CT
tunica externa
surrounding CT layer
tunica interna function
facilitates exchange by diffusion
- contains large pores to allow large molecules to diffuse
what surrounds the endothelium of blood vessels and what does it do
basement membrane that anchors it down and provides strength
tunica media function
varies between vessel type
mediates vasoconstriction and vasodilation
- makes vessels extensible and elastic
tunica externa function + facts
contains many nerves
- made of collagen and elastic fibres
vasa vasorum
tiny vessels that service the smooth muscle of big vessels like the aorta
capillary layers
tunica interna
basement membrane
elastic arteries
made of elastic fibres in tunica media/interna and a thin layer of smooth muscle
- push blood from the heart during diastole
near the heart, allows them to maintain constant pressure
pressure reservoir
blood stretches elastic fibres in tunica media and interna
creates potential energy for blood to move
example of elastic arteries
aorta, pulmonary trunk
muscular arteries
thicker layer of smooth muscle
- loose tunica externa (allows constriction/dilation)
- aka distributing arteries
why are muscular arteries aka distributing arteries
because they move blood into smaller arterioles
anastomoses definition
places that vessels of related function joint one another
anastomoses function
provide bypass methods for blood to tissues during collateral circulation
(eg. large intestine, many branches of arteries stemming from the celiac trunk)
end arteries
arteries without anastomoses
necrosis
messy tissue death
example of an end artery
brachial artery
arterioles
microscopic arteries
arteriole make up
50% of diameter is wall
has elastic lamina in tunica interna
- tunica media - 1-2 layers of ring shaped smooth muscle`
metarterioles
narrowed sections of arterioles
precapillary sphincter
can pinch of capillaries
nerves in the tunica externa of metarterioles function to:
regulate vessel diameter
capillary structure
lack tunica externa and media
capillary bed
a branch of metarterioles that lead into 10-100 capillaries
routes for blood to go from metarterioles to venules
- through capillaries
- through a thoroughfare channel
route for blood - through capillaries
(+exit and what teh circulation is called)
blood enters capillary bed
- exits via postcapillary venules
- called microcirculation
vasomotion
contraction and relaxation of precapillary sphincters to regulate blood flow through the beds
route for blood - through a thoroughfare channel
permits direct flow from metarteriole to venule
sphincters are closes, one way passage, blood does not to to extensive branches of capillaries
3 types of capillaries
continuous
fenestrated
sinusoids
continuous capillaries
- smooth continuous epithelium
- no holes, just intercellular clefts
- found in organs of CNS, lungs, muscle, and skin
intercellular clefts
division points in capillaries between adjacent endothelial cells
fenestrated capillaries
- endothelium has pores called fenestrations that permit diffusion of proteins and such
- found in kidneys, small intestine villi, eyes, endocrine glands
sinusoid capillaries
wider and twistier
- little/no basement membrane
- large pores
- where RBCs enter circulation from bone marrow
- found in liver, spleen, and other glands
fenestrations
pores found between endothelial cells in capillaries
fenestrated and sinusoid capillaries only
muscular veins can:
can withstand lots of pressure
veins - facts
10% of diameter is wall
- change shape as they merge
- thick tunica externa that contributes to distensibility
- systemic - act as blood reservoirs
blood reservoirs
places in the body that store large amounts of blood
eg. abdominal veins, skin
capillary exchange
movement of substances between blood and interstitial fluid
3 mechanisms of capillary exchange
diffusion
transcytosis
bulk flow
capillary exchange - diffusion
through fenestrations, cle
capillary exchange - transcytosis
(eg…)
- rare method
eg. insulin entering fetal blood stream
capillary exchange - bulk flow
collective movement of large volumes of molecules from high pressure to low pressure
- regulates volumes of blood and interstitial fluid
- regulated by fluid pressures
filtration
movement from blood into interstitial fluid in bulk flow
reabsorption
movement from interstitial fluid into blood in bulk flow
net filtration pressure (NFP)
difference between filtration and reabsorption
this is what bulk flow is driven by
NFP consists of (2)
hydrostatic and osmotic pressures
Blood hydrostatic pressure (BHP)
pressure of water in blood plasma pushing on endothelium
- caused by forceful ejection of blood from ventricles
- higher at arterial end than venous end in capillaries
biggest force in filtration
interstitial fluid hydrostatic pressure (IFHP)
pressure of water from interstitial fluid pushing on basement membrane of capillaries
- very weak
- constant pressure across all ends
- weak force in reabsorption
Blood colloid osmotic pressure (BCOP)
pressure exerted on solutes and proteins in blood that pulls on water in interstitial fluid
- constant across due to constant protein in blood
- strongest force in reabsorption
interstitial fluid osmotic pressure (IFOP)
pressure exerted by solutes in interstitial fluid that pulls on water in blood plasma
- very weak force in filtration
forces of bulk flow (mmHG)
BHP - 35/16mmHg out
IFHP - 1 mmHg in
BCOP - 26 mmHg in
IFOM - 0 mmHg out
Net filtration pressure equation
NFP = (BHP+IFOP) - (BCOP+IFHP)
NFP = (filtration) - (absorption)
taken at both the arterial and venous ends
what happens to filtered fluid?
85% is reabsorbed
15% taken up by lymph vessels and returned to circulation
edema
increase in interstitial fluid volume
lymph edema
failed of lymphatic vessels to filter properly
how can protein deficiency lead to edema
lack of protein will cause a decrease in BCOP, meaning a decrease in reabsorption, leaving a higher chance for fluid buildup
hemodynamics
the study of the forces that affect blood flow in the body
blood flow
volume of blood flowing through a given tissue at a given time in mL/min
total blood flow = CO
perfusion
extent of blood flow to a particular area
what modulates blood flow? (2)
blood pressure
vascular resistance
blood pressure
hydrostatic pressure that blood exerts on blood vessel walls
- highest in aorta
- generated by contraction of the ventricles
systolic blood pressure
highest BP in arteries during cardiac systole
diastolic BP
lower BP in arteries during cardiac diastole
units for blood pressure
millimetres of mercery
mmHg
arterial end of capillaries mmHg
35
venous end of capillaries mmHg
16
entry into the right atrium mmHg
0
factors that affect blood pressure
changes of blood volume over 10%
if you are retaining a lot of water, what happens to BP
increases
resistance
forces of friction that oppose blood flow through a vessel
vascular resistance is affected by: (3)
diameter of vessel lumen
blood viscosity
total vessel length
how does lumen diameter affect vascular resistance?
if the lumen is smaller, there is more surface area, more blood touches the lumen walls, increasing resistance
increased VR =
increase BP
how could the body increase the rate of venous return?
it could pump blood more forcefully from the heart
- exercise
- if BP increased at right atrium, rate of venous return would DROP
how does blood return to the heart when we sleep?
the respiratory pump
what increases venous return? (4)
increases blood volume
skeletal pump
respiratory pump
vasoconstriction
what increases heart rate (2)
decreased parasympathetic impulses
- increased sympathetic impulses and hormone release (fight of flight)
what increases stroke volume (2)
increased venous return
- increased parasympathetic impulses (decreased HR)
what increases cardiac output (2)
heart rate
stroke volume
what increases blood viscosity
increased number of red blood cells
what increases total blood vessel length
increased body size as in obesity
what increases systemic vascular resistance (3)
increased blood viscosity
increased vessel length
decreased vessel radius (vasoconstriction)
what increases mean arterial pressure (2)
increased cardiac output
increase vascular resistance
blood velocity
the speed at which blood flows
what influences blood velocity
vascular resistance
why is blood flow slow in capillaries
greater surface area = increases resistance
cardiovascular centre can signal for increased or decreased: (2+1)
heart rate
heart contractility
can also stimulate vaso dilation/constriction
RAA (renin-angiotensis-aldosterone system) affect on blood pressure
increases BP by decreasing urination
epinephrine/norepinephrine affect on BP
increase BP by increasing calcium in cytosol of cells
ADH (anti-diuretic hormone) affect on BP
increases BP by vasoconstriction
ANP (atrial natriuretic peptide) affect on BP
decreases BP by vasodilation and decrease reabsorption in kidneys
autoregulation of flow
blood vessels can change their own physiology to meet metabolic demand
2 inputs of autoregulation
physical changes
vasoconstrictors/dilators
physical constrictors - input of autoregulation
stretching of an elastic artery or vein
increased organ activity = more blood to that organ
vasodilators/constrictors - input of autoregulation
substances that increase/decrease vessel diameter (NO, K+)
systemic vs pulmonary - response to low O2
systemic - dilates to increase tissue perfusion
pulmonary - constricts to ensure only undamaged alveoli are used to oxygenate blood
shock
lack of o2 and nutrients to meet the bodies needs
must affect whole body
different kinds of shock (6)
hypovolemic shock
cardiogenic shock
anaphylatic
neurogenic
septic
obstructive
hypovolemic shock
cause by excessive dehydration
output - decrease blood vol
cardiogenic shock
damage to the heart
output - inability to pump
anaphylactic shock
excessive histamine production and vasodilators
output - decreased BP
neurogenic shock
head trauma
output - inability to sense and respond to BP changes
septic shock
bacterial toxins cause excessive vasodilation
output - decreased BP
obstructive shock
block to circulation
physiological responses to shock (4)
stimulate RAA pathway (increase blood vol)
release ADH (increase blood vol)
stimulate sympathetic nervous responses (vasoconstriction/dilation)
release local vasodilators (increase blood flow to specific tissues)
hypertension and its risks
persistently elevated BP
increased risk of heart failure, kidney disease, strokes
90-95% of cases are untraceable
circulatory routes (2)
systemic
pulmonary
function of systemic circulation
distribute O2 blood from left ventricle to all the bodys tissues
returns deoxy blood to the right atrium
4 arteries that service the head
vertebral arteries (2)
carotid arteries (2)
what ensures the brain is perfused properly
the great number of anastomoses in the brain
carotid-basilar artery anastomosis
joining of the posterior cerebral arteries and the posterior communicating arteries to the basilar artery
hepatic portal circulation
carries blood from GI tract to liver
hepatic capillaries are mostly
sinusoids
proper hepatic artery
brings oxy blood to the liver
pulmonary circulation function
brings deoxy blood from right ventricle to the alveoli for oxygenation
routes oxy blood to the left atrium
DOES NOT provide oxygen to the lung tissues
bronchial circulation
oxygenates lung tissues
the placenta is formed from both:
maternal and fetal tissues
