A&P 2 Test 2 Blood Vessels
1... small lumen (diam)-> greater resistance/ friction
TRUE Ex: arterioles constrict, resistance increases, BP rises
Why is it important that velocity slows down in capillaries?
allow time for diffusion
venules function
collect blood from capillaries
How does blood flow through THOROUGHFARE CHANNELS?
def: it is the distal end of metarteriole- no smooth muscle - direct route for blood from an arteriole to a venule, bypassing capillaries *slide 39
How does blood flow?
from regions of higher pressure to regions of lower pressure; greater the pressure difference, the greater the blood flow
how are portal systems named?
name gives name of 2nd capillary location EX: liver- hepatic portal circulation pituitary gland- hypophyseal portal system
When BP is lower than Blood osmotic pressure
reabsorption occurs; IF PULLED OUT of tissue INTO vessels
arterioles
smallest branches of arteries
Venous Return- Skeletal muscle pump STEP 1
standing @ rest: both valves opened, blood towards heart
myogenic response
stretch response
metarteriole
terminal end of arteriole
anastomoses
when a union of branches of two or more arteries supply the same body region
What conditions increase the viscosity of blood thus increase BP
- Dehydration (more solutes and less plasma) - polycythemia (unusually high number of RBCs)
significance of the structure of sinusoids (related to the function)
- allow FREE EXCHANGE of water and large plasma proteins (mostly from red blood cells) btw blood and interstitial fluid - some cases even blood cells (newly formed blood cells)
What conditions decrease viscosity and thus decreases BP
- anemia - hemorrhage depletion of plasma protein or RBCs
Flow through capillary bed (2 ways) How does blood flow through CAPILLARIES?
- arteriole-> capillaries-> venules - precapillary sphincters control the flow of blood through the capillaries - entrance of every capillary guarded by precapillary sphincter: control contraction of smooth muscle cells, constriction, reduce/stop flow
net filtration pressure
- balances the three basic forces - determines how much plasma moves out of the blood into interstitial fluid of tissues (filtration) - how much interstitial fluid moves into blood (reabsorption)
Function of continuous capillaries (3)
- diffusion of water, small solutes, and lipid-soluble materials into interstitial fluid (only chemicals/ elements are allowed to leave the capillaries-- if red blood cell leaves, something is wrong) - prevent loss of blood cells and plasma proteins** - blood- brain barrier
structure of Sinusoids (sinusoidal capillaries)
- endothelial cells unusually large fenestrations - incomplete or absent basement membrane and very large intercellular clefts
edema results from
- excess filtration (both fluid and plasma proteins) - inadequate reabsorption (liver may not produce enough plasma protein to help reabsorb)
What is the purpose of venous valves?
- folds of tunica intima - prevent blood from flowing backward - pressure Is so low, cannot overcome gravity; skeletal muscles help send blood up the body - any compression of vein pushes blood toward heart--> improves venous return
Where does the CV center receive imput from in order to reg. BP and blood flow? NEG. FEEDBACK
- higher brain: cerebral cortex, limbic system, hypothalamus - sensory receptors: proprioceptors (joints), baroreceptors (BP& stetch), chemoreceptors (concentration of acidity. in blood)
what are the three basic forces important to exchange?
- hydrostatic pressure: blood pressure - osmotic pressure: interstitial fluid - osmotic pressure: blood
Comparison of veins to arteries
- larger diameter - thinner walls - lower blood pressure
What is an aneurysm and what causes it?
- local artery pressure exceeds capacity of elastic components of tunics - bulge in an arterial wall - caused by weak spot in elastic fibers; no longer elastic (wore out) - pressure may rupture vessel EX: brain-stroke, aorta-fatal bleeding in min.
How are muscular arteries (distribution arteries) characterized?
- medium sized (Most arteries) - media contains fewer elastic fibers than elastic; more smooth muscle - vascular tone stiffens vessel wall; important in maintain vessel pressure & efficient blood flow - superficial muscular arteries= pressure points- press down to reduce blood flow and control severe bleeding
how are Arterioles characterized?
- microscopic vessels that regulate blood flow into capillary network -little, no externa -thin/ incomplete media (smooth) - interna is fenestrated
Long term restoration of BP/BV for recovery
- recall fluids from interstitial spaces - aldosterone & ADH promote fluid retention and reabsorption - thirst increases - erythropoietin stimulates red blood cell production
Baroreceptor reflexes- aortic reflex
- receptors in ascending aorta send impules to CV center via vagus (X) nerve - maintain systemic blood pressure
diffusion is fastest when...
- short distances - large concentration gradients - small ions or molecules
What is the most unique characteristic of capillaries?
- the fact that they are the smallest vessels allows them to be the only vessels that can exchange materials with interstitial fluid - microscopic capillary network permeate (spread throughout) all active body tissues
venules
- very small veins that lack tunica media - collect blood from capillaries
Structure and Important function of arteries
-Function: elasticity allows arteries to absorb pressure waves that come with each heartbeat -Change in arteries from Heart to capillaries: elastic --> muscular--> arterioles
signs of shock
-Weak, rapid pulse -Skin cool, clammy, pale -Altered mental state -Thirst, nausea
Tunica media
-bulky middle coat -made mainly of smooth muscle and elastin -external elastic membrane (Swiss)in arteries ** much thicker in arteries than in veins-
How are elastic arteries characterized?
-by well-defined internal and external elastic laminae; mostly of elastic fibers - push blood onward as ventricles relax, accommodate large surge of blood out of heart
tunica externa (adventitia)
-outermost tunic -made of fibrous connective tissue -functions as support and protection of the vessels; anchors to adjacent tissues in arteries - in veins, thicker than media
BHP
-pressure that water in blood plasma exerts against blood vessel walls and pushes fluid OUT of the capillary (into tissues) -drops as move from arterial end to venule end of capillary
Blood colloid osmotic pressure (BCOP) is created by
-suspended blood proteins that are too large to cross capillary walls so the effect is to pull fluid from IF into cap - this pressure does NOT change
1. Two ways to calculate Cardiac Output (CO)
1.) CO= heart rate X stroke volume 2.) CO= MAP/ Resistance MAP = CO X R
What are the three different types of capillaries?
1.) Continuous capillaries 2.) Fenestrated capillaries 3.) Sinusoids
three types of short term elevation of BP for recovery
1.) carotid and aortic reflexes- increase CO/ periph. vasoconst. 2.) SNS- venoconst./ arterioles constrictions 3.) hormonal effects that increase CO or periph. vasconst.
Where can you find Fenestrated Capillaries? (4)
1.) choroid plexus (brain ventricles) 2.) endocrine organs 3.) kidneys 4.) Small intestine NOT IN LIVER
What 3 factors affect vascular resistance?
1.) lumen diameter 2.) blood viscosity (thickness) 3.) total blood vessel length
3 layers of the vessel walls
1.) tunica interna (intima) 2.) tunica media 3.) tunica externa
Baroreceptor reflexes- Carotid sinus reflex ~ maintain blood flow to brain
BP stretches the wall of the carotid sinus (on internal carotid) which stimulates baroreceptors to send nerve impules to CV center in medulla via glossopharyngeal (IX) nerve-- CV center decreases CO
What are the largest vessels in the body?
Elastic Arteries (conducting arteries) which include pulmonary trunk and aorta
T/F: Veins are more elastic
FALSE: arteries are more elastic
T/F: Veins have thicker walls and higher BP
FALSE: arteries have a greater force of pressure; stronger; thicker
T/F: there's higher blood pressure in vessels closer to vena cava?
FALSE: higher in venules even though low pressure overall in venous system
T/F: Veins do not have valves
FALSE: veins do have values; need to send blood to the heart from lower extremities and such
T/F: blood pressure is lowest in aorta
FALSE; highest in aorta and lowest in entrance of R. atrium
T/F: Blood from the lower limbs travel to the heart through superficial veins
False because the veins need skeletal muscles to push the blood up, therefore, they travel through deep veins
Where can you find extensive capillary networks?
In body tissues with HIGH metabolic requirements (muscles, brain, liver, kidneys, nervous system)
Where in your body are there fewer capillaries?
In body tissues with lower metabolic requirements (tendons and ligaments) longer time to heal if damaged
vasodilating chemicals that alter blood diameter
K+, H+, lactic acid, NO, histamine
What kind tissues do not have capillaries?
Lining epithelia, the cornea and lens of the eye, and cartilage
STEP 3
Muscle relaxes: BP falls causing proximal valve to close; distal valve opens- BP higher in foot; eventually prox. valve reopens
What does it mean to have a positive NFP and neg. NFP
Positive NFP= filter out Negative NFP= reabsorption
Hormonal Reg. of BP: RAA system
Stim: BV falls or blood flow to kidney falls; effect: Kidneys secrete renin into blood stream; Angiotensin II activated- raises BP by acting as a vasoconstrictor or stimulates secretion of aldosterone
3. vascular resistance opposes blood flow due to friction btw blood & vessel walls? true or false
TRUE
CO decrease causes a decrease in MAP, if R does not change
TRUE
During exhalation valves in veins prevent backflow of blood from thoracic to abdominal veins (T/F)
TRUE
If CO rises, then MAP (or BP) rises as long as R stays the same
TRUE
T/F: Body contains more veins than arteries?
TRUE
T/F: IFHP and IFOP are basically zero so we do not need to consider under normal conditions
TRUE
T/F: When an artery constricts, the endothelial lining folds
TRUE
T/F: arterial end of capillary has a positive NFP (filtration) while venous end of capillary has a neg NFP (reabsorption)
TRUE
T/F: arteries and veins run side by side
TRUE
T/F: arterioles are referred to as resistance vessels
TRUE
T/F: resistance and BP are directly proportional
TRUE
True /false: veins have a wider lumen than arteries?
TRUE
During inhalation there's an increase in pressure in abdominal cavity and decrease in thoracic cavity (T/F)
TRUE due to downward movement of diaphragm
T/F: BHP and IFOP both push fluid out of cap into IF
TRUE: filtering
T/F: 15% filtered fluid move from IF enter lymphatic capillaries, lymph nodes
TRUE; lymph drains into junction of jugular and subclavian vein & return to the blood
T/F: BCOP and IFHP both pull fluid out of IF into cap
TRUE; reabsorbing
2... Higher the blood viscosity, higher the vascular resistance
True
T/F: postcapillary venules initially receive blood from capillaries
True
name the major factor that creates osmotic pressure in the blood stream and it should never leave the blood stream
albumin
end arteries
arteries that do not anastomose; obstruction of end artery interrupts blood supply to a whole segment of an organ, producing necrosis
What are the 5 classes of Blood vessels
arteries, arterioles, capillaries, venules, and veins
which vessels contribute the most resistance due to small diameters?
arterioles, capillaries , and venules - they have a low velocity of blood flow
Mean arterial pressure (MAP)
avg blood pressure in arteries MAP= diastolic pressure + (pulse pressure/3)
under normal conditions of hemodynamics, the heart must provide enough pressure to overcome resistance to...
blood flow
what are the 2 pressures that promote filtration?
blood hydrostatic pressure (BHP) interstitial fluid osmotic pressure (IFOP)
Venous Return- Respiratory Pump
blood moves from compressed abdominal veins into decompressed thoracic veins and into right atrium
smallest blood vessels
capillaries
Arteries function
carry blood AWAY from the heart
portal system
circulation of blood through the portal vein, where blood passes from one capillary network into another - connecting two capillary beds
capillary exchange: diffusion
concentration driven; high to low
significance of resistance when pertaining to arteries
constricted arteries oppose blood flow; -smaller diameter, more resistance, blood flow slows down
Which type of capillary is the most abundant
continuous capillaries
definition of vasomotion
contraction and relaxation cycle of capillary sphincters ~ blood flows in pulses through beds which causes blood flow in capillary beds to constantly change routes
Function of anastomoic veins
cross/ connect the accompanying artery to form ladderlike rungs btw the paired veins
What increases CO2 levels
decrease in O2 or pH (acidic)
function of chemoreceptors
detect changes in pH, O2, CO2 concentrations
pulse pressure
difference btw systolic pressure and diastolic pressure
what does the portal venous system do?
direct blood from parts of gastrointestinal tract to the liver for metabolism before going to the heart
shock
failure of CV system to deliver enough O2 and nutrients to meet cellular metabolic needs
When BP is greater than blood osmotic pressure
filtration occurs; plasma (fluid) PUSHED OUT of vessels into IF
what are intercellular clefts?
gaps btw neighboring endothelial cells
Fenestrated means...
have pores in the endothelial lining
What are the conditions of high CO2 levels?
hypoxia, acidosis, hypercapnia
Hormonal Reg: epinephrine, norepinephrine
increase CO
sig of aldosterone
increases reabsorption of Na and water by kidneys, which increases total BV and BP
vasoconstriction
increases resistance, decreases blood flow and increases blood pressure; diameter of lumen decreases
tunica intima
lines the lumen of a vessel and is a thin single layer of endothelium that is continuous with the endocardium of the heart
where are sinusoids found in the body?
liver spleen bone marrow endocrine organs- adrenal glands, parathyroid and ant. pituitary
What are the three principal blood reservoirs?
liver, spleen, and skin
STEP 2
muscles contract: veins compressed pushing blood through proximal valve; distal valve closes
Reabsorption (osmotic pressure) results from
osmosis- water diffuses into a solution with higher solute concentration
Function of fenestrated capillaries
permit RAPID exchange of water and larger solutes btw plasma and interstitial fluid
structure of continuous capillaries
plasma membranes of endothelial cells form a continuous tube
What is the name of the capillary junction at a metarteriole?
precapillary sphincter- monitors blood flow into capillary bed
capillary exchange: reabsorption (osmotic pressure)
pressure- driven movement from interstitial fluid into blood capillaries
capillary exchange: filtration (hydrostatic pressure)
pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid (tissues)
IFOP
pulls fluid out of the capillary and into the interstitial fluid; really not a "force". IFOP very small- only tiny amounts of protein present in IF. Small protein amount that leaks from plasma into IF, does not accumulate, passes into lymph.
What are the largest blood vessels attached to the heart
pulmonary trunk (Pulmonary circulation) and aorta (systemic circulation)
Hemorrhaging and dehydration increase...
reabsorption; decrease in the NFP
significance of vessel walls
resilient enough to withstand pressure changes, flexible enough to move with tissues and organs
veins function
return blood TO the heart
capillaries function
smallest blood vessels (DIFFUSION) location of exchange btw blood & interstitial fluid; they are the only vessels that directly serve body cells
vasodilation
smooth muscles relax
Hormonal Reg: ADH (vasopressin)
stim: dehydration (high osmotic pressure in blood), or low BV response: vasoconstriction and reduces water loss at kidneys (back to bloodstream)-- increased BV and decrease in urine output
Hormonal Reg: atrial natriuretic peptide (ANP)- from cells in R atrium
stim: excessive diastolic stretching response: lowers BV & BP & stress on heart by promoting loss of Na and water in urine
What changes the small muscular arteries and arterioles' diameter?
sympathetic or endocrine stimulation
Where is the largest portion blood volume located?
systemic veins and venules (blood reservoirs)
Venoconstriction in liver, skin, and lungs redistribute venous reserve to...
the brian
what constricts and essentially increases the blood pressure in the Media?
the sympathetic stimulation of smooth muscle to contract
3... increasing vessel length increases friction because
there's a larger surface area in contact with blood (great resistance in blood flow bc more to get through- greater BP)
If there's an increase in blood vol (water retention), then..
there's an increase of blood pressure; water enters the tissue
Where do excess fluid go?
they enter into lymphatic vessels to flush out tissues
2. BP depends on volume so if there's a decrease in vol (hemorrhage) then...
this decreases amt of blood circulated through the arteries each min thus BP drops
vasoconstricting chemicals that alter blood diameter
thromboxane A2, superoxide radicals
T/F: Most of the blood that travels from the upper limbs travel back to the heart through superficial veins
true
cooling means
vasoconstriction
In response Chem.re send pulses to CV to increase sympathetic stimulation to arterioles and veins producing...
vasoconstriction, increased BP, breathing rate adjustment
warming means
vasodilation
What is the venous response to blood loss?
vasomotor centers stimulate sympathetic nerves and venoconstriction causes an increase in blood volume in arteries and capillaries
vascular (venous) sinus
vein with thin endothelial wall, no smooth muscle to alter its diameter EX: Dural venous sinuses, coronary sinus-heart
varicose veins
walls of veins near valves weaken or become stretched, valves do not work properly and blood pools
NFP=
(BHP + IFOP)- (BCOP+ IFHP)
Large veins
- all 3 tunica layers - thick tunica externa - thin tunica media - include superior/inferior vena cava
What 3 factors affect blood pressure?
- cardiac output - blood volume - vascular resistance
Capillary Function
- location of all exchange of cardiovascular system - allow materials to diffuse btw blood and interstitial fluid
what are capillary beds (capillary plexus)
- network of 10-100 capillaries that arise from a single metarteriole - connect arterioles to venules
medium veins
- thin tunica media and few smooth muscle cells - tunica externa with longitudinal bundles of elastic fibers
What are the three types of veins?
1.) venules 2.) medium veins 3.) large veins
What dilates the media?
NO, H+, and lactic acid
What monitors blood at sinusoids
Phagocytic cells
