Exam 2

Where are the smallest veins?

The postcapillary venules

What are the physical characteristics of venules?

Contains Endothelium with pericytes, and is extremely porous

What distinguishes large venules?

have one or two layers of smooth muscle cells (tunica media) and thin tunica externa

What depends on the osmotic pressure in the capillaries?

Perfusion of Tissues

What is the Perfusion of Tissues?

continuous delivery of oxygenated blood through arteries and capillaries to tissues, which removes waste products and sustains cellular function

What dictates whether water will move in capillaries?

The difference in osmotic pressure

What opposes blood pressure in the capillaries?

Osmotic pressure

How does water move between capillaries and interstitial fluid?

Capillaries have higher osmotic
pressure than interstitial fluid
➢ Blood pressure forces water out of
the capillaries
➢ The higher osmotic pressure pulls
water into the capillaries

Where is fluid forced out of the capillaries?

arterial end through intercellular clefts

Where does most of the fluid in capillary exchanges return through?

The venous end

What are the two forces that determine the flow of fluids across capillary walls?

Hydrostatic pressure & Colloid osmotic pressure

What provides Hydrostatic pressure?

Capillaries

What is an equivalent to hydrostatic pressure?

Capillary blood pressure

What pushes fluid out of capillary walls?

Capillary hydrostatic pressure (CHP)

What is the process by which solutes are removed from the fluid leaving capillaries?

Filtration

What is filtration in respects to capillary exchanges?

The process by which solutes are removed from the fluid leaving the capillaries

What’s filtered from entering the intercellular space?

Solutes that are too large to pass through intercellular clefts

What changes as blood flows through the capillary beds?

Blood pressure drops

What is the hydrostatic pressure at the arterial end?

35 mm Hg

What is the hydrostatic pressure at the venous end?

18 mm Hg

What is Colloid Osmotic pressure produced by?

large molecules, such as plasma proteins, that can not cross the capillary wall

What contains a larger concentration of proteins? Blood or interstitial fluid?

Blood

What is the Blood colloid osmotic pressure (BCOP) mm Hg?

25 mm Hg

What does Blood colloid osmotic pressure (BCOP) do?

pulls water into capillaries and opposes the capillary hydrostatic pressure that forces fluid out of the capillaries

What pulls water into capillaries and opposes the capillary hydrostatic pressure that forces fluid out of the capillaries?

Blood colloid osmotic pressure (BCOP)

What is the difference between the capillary hydrostatic pressure (CHP) that forces fluids out of the capillaries and the blood colloid osmotic pressure (BCOP) which pulls water into the capillaries?

Net filtration pressure (NFP)

What is Net filtration pressure (NFP)?

It’s the difference between the capillary hydrostatic pressure (CHP) that forces fluids out of the capillaries and the blood colloid osmotic pressure (BCOP) which pulls water into the capillaries

What is the formula for Net filtration pressure (NFP)

capillary hydrostatic pressure (CHP) - blood colloid osmotic pressure (BCOP)

What does a positive Net filtration pressure (NFP) mean?

Net motion is out of the capillary

What does a negitive Net filtration pressure (NFP) mean?

Net motion is into the capillary

What is Reabsorption in terms of capillary exchange?

The movement of fluid back into capillaries

What is the movement of fluid back into capillaries?

Reabsorption

How many liters of fluid are filtered by the capillaries in a day?

24

How much fluid is reabsorbed at the venous end of a capillary in a day out of the 24 liters?

20.4 (85%)

Where does the fluid lost by the venous system at capillaries go?

Flow though tissues into the lymphatic system

How can you compare the structure of a vein to an artery?

Have thinner walls and larger lumens than arteries

What happens to the structure of veins in histology?

Veins are usually collapsed and lumens appear slit like

Describe the tunica media of a vein

Tunica media is poorly developed and thin with little smooth muscle or elastin

Describe the Tunica externa of a vein

Tunica externa is thickest wall layer with thick longitudinal bundles of collagen fibers and elastic networks

Veins can hols up to what percent of the bodies blood supply?

65%

What precent of blood volume is typically in the veins?

60%

What are two nicknames for veins?

Capacitance vessels, Blood reservoirs

Is blood pressure in the veins high or low?

low

What does a large lumen in the veins provide?

Little resistance to blood flow

What prevents backflow of blood in veins?

Venous valves

Where are venous valves most abundant?

Veins of limbs

Where are venous valves absent?

Veins of the thoracic and abdominal body cavities

What is the Venous Sinuses?

valveless blood channels located between the periosteal and meningeal layers of the dura mater in the brain

How can you physically describe Venous Sinuses

flattened veins with extremely thin walls composed of endothelium

What are Venous sinuses supported by?

tissues that surround them

What supports Dural venous sinuses?

Dura mater

What are Anastomoses

Special Interconnections Between Blood Vessels

How are arterial anastomoses formed?

When Arteries supplying the same territory merge

What forms when Arteries supplying the same territory merge

arterial anastomoses

What provides collateral channels for blood supply to specific regions

anastomoses

What redundancy in blood supply so that blockage to one artery will not damage tissue?

anastomoses

Where are anastomoses found?

Joints, abdominal organs, heart, brain

What is the anastomoses in the brain called?

Circle of willis

What connect arteries and veins as in capillary beds (not Vascular shunt)

Arteriovenous anastomoses

What connects veins are common

Venous anastomoses

What is the volume of blood circulating in a given period of time

Blood flow / cardiac output

What are the units used for blood flow?

ml/min

What other concept is blood flow equivalent to?

cardiac output

Blood flow is what under resting conditions?

Relatively constant

How can you describe blood flow to individual organs?

It can depend based off of their immediate needs

What is the relationship between blood flow and resistance of blood vessels

They are inversely proportional

As resistance raises what happens to flow?

flow slows

What is resistance in terms of blood flow?

Is a measure of the amount of friction blood encounters as it travels through blood vessels

What is the resistance of the peripheral circulation

Peripheral resistance

What is the measure of the amount of friction blood encounters as it travels through blood vessels

Resistance

What are the three major sources of blood flow resistance?

Blood viscosity, blood vessel length, and blood vessel diameter

What makes blood viscosity change?

the number of red blood cells (anemias and polycythemia) / A shift in hematocrit

What is the relationship between resistance to flow and radius of the blood vessel

Resistance is inversely proportional to 1/ radius^4

Why is resistance important to controlling blood flow

easily be changed by changing blood vessel diameter

What happens when an arteriole dilate

blood flow increases

What is an Irregular fluid motion where blood from the different lamina mixes

Turbulence

What causes turbulence?

Irregular fluid motion where blood from the different lamina mixes

What causes turbulence?

➢ Abrupt changes in blood vessel diameter
➢ Rough or protruding areas of the blood vessel wall - such as those produced by fatty plaques of atherosclerosis

What’s the end effect of turbulence?

Dramatically increases resistance

What is turbulence?

Irregular fluid motion where blood from the different lamina mixes

Blood Flow at Different Points in Vasculature is _______.

Constant

When blood flow is constant what does that mean for the speed in small blood vessels and larger blood vessels?

10 ml/min in 10 small blood vessels = 100 ml/min in one larger blood vessel

What happens to blood pressure as it progresses through the systemic circuit?

Blood pressure decreases

When is systemic blood pressure the highest?

in the aorta peaking at about 120 mm Hg

When is blood pressure the lowest?

At the entrance to the right atrium the pressure reaches a minimum of 2 mm Hg

When is blood pressure at its peak?

Ventricular systole

What’s a fun word you can use to describe how blood pressure moves over time?

Pulsatile

What is the peak pressure called in terms of blood pressure?

systolic pressure

What is The lowest value of the blood pressure occurs during ventricular diastole

Diastolic pressure

What is Diastolic Pressure?

The lowest value of the blood pressure occurs during ventricular diastole

What is the average measurement of diastolic pressure?

70-80 mm Hg

What is the average measurement of systolic pressure?

120 mm Hg

What is the Difference (math) Between the Systolic and Diastolic Pressure

Pulse Pressure

Where can pulse pressure be felt

The pulse of arteries

What is the mean pressure between systole and diastole?

Mean Arterial pressure

Why is Mean Arterial pressure (MAP) not an average?

MAP is not the average of the systolic and diastolic pressure because diastole last longer than systole

How can you calculate Mean Arterial pressure?

Diastolic pressure + (pulse pressure /3)

At rest what percent of vessels has blood flow through them within a typical capillary bed?

25%

What is the Autoregulation of Blood Flow Within Tissues?

Local factors that change the pattern of blood flow within capillary beds

What causes capillary sphincters to relax, increasing blood flow

Vasodilators