Chapter 15 Physiology

Blood vessels operate under a _ system

closed

(this means blood does not leave the heart or vessels)

Vessels get progressively _ layers as they progress

less

(arteries have more layers than arterioles, and arterioles have more layers than capillaries, etc)

Layers in the capillary

endothelium

basement membrane

Layers in the arteriole

endothelium

basement membrane

high levels of smooth muscle

Layers in the venule

endothelium

basement membrane

moderate levels of smooth muscle

Layers in the muscular artery

endothelium

basement membrane

high levels of smooth muscle

Elastic connective tissue

All vessels, instead of capillaries, have some amount of _ in them. Muscular arteries and arterioles have a lot of it.

smooth muscle

endothelium

innermost

thin layer of cells

nonstick

do much more than just letting the blood flow

smooth muscle regulates

blood vessel diameter

how does smooth muscle regulate diameter?

vasodilation, if the blood vessel increases in diameter,

vasoconstriction, if it narrows down in diameter.

connective tissue; two types

Elastic

Fibrous

Elastic artery function

also they are also called pressure reservoirs

stretch aorta in response to pressure

arterioles feed blood to the capillaries and are known as resistance vessels because

they have the most smooth muscle and can alter diameter the most

Vasoconstriction _ the resistance by the tube narrowing down and therefore blood pressure _.

increases; increases

Vasodilation _ the resistance and blood pressure because now the tube is wider.

decreases

Capillaries are fit to exchange nutrients for two reasons:

Capillary walls are thin (single cell layer thick)

Capillary walls contain pores

Capillaries form _ at tissue

beds

Flow of blood in capillaries is controlled in two ways:

using the metarteriole and the capillary sphincters.

Microcirculation refers to which vessels?

The arterioles, capillaries, and venules

Metarterioles structure (see image)

branch off of arterioles, ends at the venule

Metarteriole blood flow is controlled by

precapillary sphincters

precapillary sphincters can relax or contract. When they are relaxed,

blood will flow to the capillary bed, where nutrients can be exchanged

(then to the venule, then back to the heart)

When precapillary sphincters are contracted, blood

cannot go to the capillary bed, it passes on through directly to the venule

(in the image, the white part indicates NO blood flow)

Example of precapillary sphincters contracting and relaxing (teacher example)

Let's take the skeletal muscle contracting. Now, during exercise, the requirement for glucose, oxygen, etc. is increased in the skeletal muscle. So, what happens in the skeletal muscle is the precapillary sphincter is relaxed and the muscle tissue is able to get a lot of blood supply. Now, because the amount of blood that is in the body is fixed, you need to remove blood from some other organ system, and bypass or shunted to the skeletal muscle. So the precapillary sphincters in the digestive system in this case will be contracted. That is why the blood bypasses the GI tract and gets straight back to the heart and feeding that muscle that is requiring extra supply.

Three types of capillaries

Continuous

Fenestrated

Sinusoids

the primary difference in the Three types of capillaries is that they have different

permeabilities

in Continuous capillaries, cells form a _ and are interrupted by some _

continuous layer; intercellular clefts

Fenestrated capillaries contain

pores called fenestrations

Fenestrated capillaries have _ than continuous

higher permeability

Fenestrated capillaries main locations

kidneys, small intestine, endocrine organs

Sinusoids structure

wider and more winding

Sinusoids have unusually large

fenestrations

Sinusoids location

bone marrow, spleen, liver

Sinusoids are permeable to

proteins and cells

Veins are helped by a system of

valves and pumps

veins and venules are termed as _ because about _ of the blood when a person is at rest

blood reservoirs; 65%

REVIEW:

arteries are called as _, arterioles are called as _, and venules and veins are called as _.

pressure reservoirs; resistance vessels; blood reservoirs

Which blood vessels drain blood from capillaries

venules

Primary method of capillary exchange

diffusion

diffusion does not need

energy

Substances that are easily exchanged in diffusion

Gases

fluids

nutrients (such as glucose)

Larger substances in capillaries are transported via

transcytosis

Bulk flow is a _ process

passive

bulk flow moves large volumes of solutes and fluid moved in the

same direction

For filtration and absorption, the reference point is the

capillary

Bulk movement from capillaries into interstitial fluid is

Filtration

Bulk movement from interstitial fluid into capillaries is

Absorption

Starling forces determine the

direction of flow

starling forces include

capillary hydrostatic pressure,

interstitial fluid hydrostatic pressure,

plasma colloid osmotic pressure, and

interstitial fluid colloid osmotic pressure

starling forces

Main Function of the lymphatic system

picks up EXCESS FLUID filtered by the capillaries

Misc functions of the lymphatic system

Returns filtered plasma proteins back to the blood

Carries out immune responses

transporting dietary lipids

fluid inside the lymphatic vessels is referred to as

lymph

lymphatic vessels will begin as

capillaries

NOT BLOOD CAPILLARIES; they start as lymphatic capillaries

lymphatic capillaries are closed

at one end

(contrast this to blood capillaries, which have two ends)

Lymph drainage is done through a _ network that runs excess fluid back to the cardiovascular system

parallel

Definition of blood flow

volume of blood that flows through the tissue at any given time

two factors that will impact blood flow

pressure gradient

resistance

Blood flow equation

F = ΔP/R

F is blood flow

ΔP is pressure gradient

R is resistance to blood flow

Based off the blood flow equation, flow is directly proportional to the _ and inversely proportional to the _ offered.

pressure gradient; resistance

Resistance is the opposition to

blood flow

All of the resistances of the vessels is referred to as

total peripheral resistance (TPR)

total peripheral resistance (TPR) equation

Need to know equation so you know if, say, a certain value, like blood viscosity, increased, would TPR increase or decrease? By how much? Exponentially or not?

Laminar

No noise and the inner sides of the tubes are uniform and smooth

turbulent flow 

creates sound, insides of the tube are not uniform, then it creates turbulence and it is called as turbulent flow.

Which flow used to measure blood pressure

turbulent flow 

(b/c it creates sound)

and is the _ measured pressure in the system

highest

and is the _ measured pressure in the system

lowest

MAP drives

Graph of MAP: See avg pressure, and how pressure changes depending on vessels

avg is 90 millimeters mercury pressure, pressure is highest in the aorta and decreases when going to arterioles, capillaries, venules, and veins

Maximum drop in blood pressure occurs in the

arterioles

(b/c of smooth muscle that controls the diameter; see last flashcard)

MAP =

Cardiac output (CO) * Total peripheral resistance (TPR)

Modified MAP equation

MAP = Heart rate * Stroke volume * TPR

Vessel compliance 

measure of the ability for a hollow object to stretch

Vessel compliance equation

Veins have high compliance so they can _, whereas arteries have less compliance.

easily expand

Venous return (blood coming back to the heart) is largely determined by the

venous pressure gradient 

mechanisms that are also responsible for venous return

(maybe not as prominent as the venous pressure gradient, but still need to know)

the valves in the veins, the skeletal muscle pump, vasoconstriction, and the respiratory pump

Blood flow is dependent on _

Blood flow from organ to organ _

varies

When flow of blood is parallel,

flow of blood to an organ does not affect flow of blood to other organs

(e.g. flow to the kidney does not affect flow of blood to the heart)

Baseline for constriction and dilation

Vascular tone

Vascular tone can be _ based off of _ or _ factors

changed; intrinsic; extrinsic

Examples of intrinsic factors

Examples of extrinsic factors

Metabolic control and hyperemia refers to

blood flow to a specific tissue is increased (hyperemia) to meet elevated metabolic demands or compensate for a temporary lack of oxygen

Definition of shock 

4 types of shock

Hypovolemic shock

reduced volume of blood

Hypovolemic shock usually happens after a

hemorrhage

Cardiogenic shock

Heart is not able to pump

(therefore less delivery of blood to tissues)

in vascular shock, blood vessels undergo massive

vasodilation

massive vasodilation causes sudden drops of

pressure and delivery of materials is not possible

obstructive shock

something wrong obstructing the flow of blood

Homeostatic response to shock:

_ of the renin-angiotensin-aldosterone system

activation

Homeostatic response to shock:

Secretion of

antidiuretic hormone

Homeostatic response to shock:

activation of the _ division of the ANS

sympathetic

Homeostatic response to shock:

Release of

local vasodilators

Unlike arterioles in most tissues of the body, the arterioles in the heart and skeletal muscle have an abundance of

β2-adrenergic receptors (beta receptors)

Activation of the β2 receptors causes

arterioles to vasodilate