3.1.1. Physical Properties and Histology of the Circ.

Question 1

What do we call the specialized epithelium lining the interior of the heart, blood vessels, and the lymphatics?

Answer 1

The endothelium

Question 2

Which ventricle in the heart contains more muscle and why?

Answer 2

The Left Ventricle (LV) contains more muscle because it pumps against higher pressures.

Question 3

In what manner does the heart contract? (is it like preistalsis, or do the muscles line up to squeeze in a certain way)

What does this accomplish?

Answer 3

The hear contracts in a spiral manner (like wringing out a wet hand towel).

This helps the heart to increase the amount of blood moved with each pump.

Question 4

What do we call the amount of blood actually ejected from the LV?

Answer 4

The ejection fraction (in %)

Question 5

In general, are the atria more or less muscular than the ventricles?

Answer 5

Generally, they are less muscuar

Question 6

What 3 layers of cardiac tissue are present in the heart?

Answer 6

Epicardium (outer most)

Myocardium (central, muscle)

Endocardium (innermost)

Question 7

Do cardiac cells function as a syncytium?

If not, how do they pump synchronously?

Answer 7

They are not a syncytium.

Myocardium pumps as one unit because the cells are connected by gap junctions, allowing chemical and electrical stimuli to travel along a long line of cells as if it were one large cell.

Question 8

Valves in our vasculature contain what material instead of muscle?

Answer 8

Dense Connective Tissue (Dense CT)

Question 9

What are the functions of the SA (sinoatrial) and AV (atrioventricular) nodes?

Answer 9

These are the sites of pacemaker cells in the heart, which tell myocytes when to contract.

Both nodes have a “preset” pace (AV is actually slower than SA)

The SA node sets the basal rhythm

AV node functions to slow the electrical stimulus from the SA node so that the atria and ventricles do not pump at the same time.

Question 10

How is the electrical stimulus sent throughout the heart?

OR

What structures does it go through in what order?

(ECG correlate, from https://www.youtube.com/watch?v=RYZ4daFwMa8)

Answer 10

Starts at SA node

Travels across the atria (P wave)

Hits the AV node and slows (P-R segment)

Moves from AV to the bundle of His in the interventricular septum (Q)

Travels up Purkinje fibers (R and S)

Ventricles repolarize (T wave)

Question 11

What three layers are vessels comprised of in the circulatory system?

Answer 11

Tunica (L. tunic = layer):

Intima (luminal)

Media(middle)

Externa/Adventitia (outside of vessel)

Question 12

The tunica intima of vessels is lined by what cell type?

Answer 12

Endothelium

Properties of endothelium change based upon which vessel you are in

Question 13

What does the tunica media typically contain?

Is the tunica media larger in arteries or veins?

Answer 13

Smooth Muscle (especially in arteries)

This layer is thicker in arteries than in veins because of the extra smooth muscle.

Question 14

What does the tunica adventitia contain?

What is special about the tunica adventitia of the Vena Cava?

Answer 14

Typically connective tissue, along with the nervi vasorum and the vasa vasorum

The tunica adventitia of the Vena Cava contains smooth muscle (it’s the only vessel with smooth muscle in the adventitia)

Source: Mr. Jones (and meee)

Question 15

Histologically, what are two differences between veins and arteries?

Answer 15

Arteries have a thicker wall than veins

Veins will typically appear flattened, whereas arteries will keep their rounded appearance

Question 16

What are two histological differences between arteries and veins in the tunica intima?

Answer 16

The endothelium will appear wavy in arteries due to muscle constriction, where as the vein endothelia will appear smooth

You may find an internal elastic membrane in arteries, but this is absent in veins

Question 17

Name some differences between the Tunica Media of veins and arteries

Answer 17

Tunica Media (TM)

Arteries

• Normally the thickest layer in arteries
• Smooth muscle cells and elastic fibers predominate (the proportions of these vary with distance from the heart)
• External elastic membrane present in larger vessels

Veins

• Normally thinner than the tunica externa
• Smooth muscle cells and collagenous fibers predominate
• Nervi vasorum and vasa vasorum present
• External elastic membrane absent

Question 18

Name some differences between veins and arteries in the tunica adventitia

Answer 18

Tunica Externa (TE) / Adventitia

Arteries

• Normally thinner than the tunica media in all but the largest arteries
• Collagenous and elastic fibers
• Nervi vasorum and vasa vasorum present

​Veins

• Normally the thickest layer in veins
• Collagenous and smooth fibers predominate
• Some smooth muscle fibers
• Nervi vasorum and vasa vasorum present

Question 19

Why are the largest arteries called “elastic arteries”?

Answer 19

Because they contain elastin bundles and layers

Allows for the reboud of these vessels against changes in blood pressure (may expand then contract to translate BP changes)

Question 20

What are the four valves of the heart?

Answer 20

2 groups:

atrioventricular valves

semilunar valves

Or in this order, from R to L:

Tricuspid, Pulmonary, Bicuspid (Mitral), Aortic

Pneumonic: Try (Tri) before you buy (bi/mitral)

Question 21

What is important about the orientation of the valves in the heart?

Answer 21

The orientation of these valves allows blood to flow in one direction, and quickly halts blood flow in the opposite direction.

(Histologially, if it looks like you are looking at a bowl or cup, you are looking at it in the forward direction, or “as the blood flows”)

Question 22

Learn to compare and contrast each type of vessel

Question 23

Which vessels/structures allow for regulation of blood flow around capillaries?

Answer 23

Arterioles

Precapillary Sphincters (The SPHINCTERRRR says what?)

Venules

Question 24

How many layers of muscle cells are present in arteriorles?

In small arteries?

Answer 24

1-2 muscle layers in arterioles

More than 2 in small arteries

Large arteries are…larger

Question 25

What are pericytes and what do they do and where are they?

Answer 25

What they are: specialized cells found w/in the basal lamina What they do: responsive to chemical signals (eg NO, synthesized by the E-NOS gene) give rise to muscle and endothelium during injury can be involved in the Dz process Where they are: sparsely located in/on capillaries & venules

Question 26

\_\_\_\_\_\_\_\_ _______ determines how circulation is regulated.

Answer 26

Local Control

Question 27

Pressure is defined as...

Answer 27

Force exerted over an area P = F/A

Question 28

When talking about pressure in the cardiovascular system, what are we really talking about?

Answer 28

We are really talking about the DIFFERENCE in pressures

Question 29

What are the big three "pressures" seen in the cardiovascular (CV) system?

Answer 29

Driving Pressure: difference in pressure between two points Hydrostatic Pressure: Pressure due to gravity Transmural Pressure: pressure exerted by fluid (blood) on the walls of vessels (Mura = Latin for wall) (BP = Circulatory pressure - atmospheric pressure)

Question 30

What is flow?

Answer 30

The movement of a fluid (blood here) relative to a certain point (In general, slower flow = better diffusion of nutrients, waste, oxygen, etc)

Question 31

What is resistance? What kinds of things create resistance?

Answer 31

Forces that, in general, oppose flow Size of a vessel (both radius and length) Friction (viscosity of fluid, "stickiness" of vessel wall)

Question 32

Is arterial BP dependent or independent of Cardiac Output (CO)?

Answer 32

Typically, it is INDEPENDENT of CO

Question 33

How is resistance related to the following: Vessel Length? Vessel Radius? Blood Viscosity?

Answer 33

Resistance is directly proportional to vessel length and blood viscosity Resistance is indirectly proportional to vessel radius to the fourth power

Question 34

What is Poiseuille's Equation?

Answer 34

R ~ (n)L/(r^4) n = viscosity L = length r = radius R = resistance

Question 35

What are the three requirements of Poiseuille's Equation?

Answer 35

1. Blood is incompressible and newtonian (follows newtonian mechanics, i.e. newton's laws) 2. blood flow is laminar through a tube of constant circular cross-section (radius) and is substantially longer than its diameter 3. There is no acceleration of fluid in the pipe (flow is constant and steady)

Question 36

What kind of factors influence blood viscosity?

Answer 36

hematocrit * positively-related to viscosity (increased # of RBCs → curvilinear increase in viscosity) * strong determinant of viscosity, esp important in polycythemia temperature * inversely-related to viscosity (1 degree C decrease → blood becomes ~2% thicker) flow rate * low flow states w/in microcirculations (arterioles, capillary beds, venules) may promote increased molecular interactions b/w RBCs and plasma proteins clotting * kind of like letting Jell-O cool after you mix the hot water and gelatin…

Question 37

What is laminar flow? Turbulent flow?

Answer 37

Laminar = smooth flow Turbulent flow = "messed up" flow 

Question 38

What are the clinical differences between laminar and turbulent flow?

Answer 38

With auscultation: CANNOT hear laminar flow CAN hear turbulent Turbulent flow occurs in large arteries at branch points, in diseased & stenotic arteries, and across stenotic heart valves

Question 39

What is the importance of a series versus parallel arrangment in blood flow?

Answer 39

Series arrangement * seen in hepatic portal system and pulmonary circulation * pulmonary: heart to lungs, then back to heart * capillary beds lie one after another, but consequently see less pressure (heart, GI tract, liver, back to heart) Parallel arrangement * allows the body to regulate organ systems individually * different organs can draw from the same pool of blood (w/the same BP)

Question 40

What is pulse pressure?

Answer 40

Systolic - diastolic blood pressures

Question 41

What is Total Peripheral Resistance (TPR)?

Answer 41

* R = ΔP / Q * ΔP is the change in pressure across the ENTIRE SYSTEMIC circulation * BP is measured immediately after exiting the left ventricle and within the right atrium * Q is the flow rate through the vasculature (equal to the CO)