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