Last Day: Blood Vessels

C5-a: Identify & give functions for main arteries & veins

C5-b: Describe & differentiate between the 5 vessel types (size, structure, direction of blood)

C5-c: Differentiate between systemic & pulmonary circulatory systems

Today: Blood Vessels

C5-d: Demonstrate knowledge of path of blood cell throughout body

C5-e: Relate blood pressure & velocity to cross-sectional areas of vessels

C5-f: Describe capillary-tissue fluid exchange

Think About It

What materials are being exchanged at the capillary interface?

What materials leave the capillary into the body tissues?

What materials enter the capillary at the body tissues?

Recall that...

• Solutes in solution go from areas of high CONCENTRATION to low

• Water moves from areas of low SOLUTE CONCENTRATION to high (osmotic pressure)

• Fluids & solutes will go from areas of high PRESSURE to areas of low (blood pressure)

5

Blood ENTERS capillary under pressure Pressure forces some fluid & solutes out of the

blood (not red blood cells or large proteins)

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Most of the fluid is then recaptured by the venule end of the capillary Pressure decreases along the capillary bed Proteins in the blood (ex. albumen) create an osmotic

force that draws fluid back into blood

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Lymphatic system will collect fluid that is not captured and return it to the blood

Think About It

What materials will leave the blood after point X?

Online quizzes + Animations

• http://www.phschool.com/science/biology_place/biocoach/cardio2/endothelium.html

• http://highered.mcgraw-hill.com/classware/ala.do?isbn=0072956208&alaid=ala_996537&showSelfStudyTree=true

• http://www.mhhe.com/biosci/genbio/espv2/data/animals/006/index.html

Think About It

In which vessels is the speed of blood flow the fastest? Why?

In which vessels is the speed of blood flow the slowest? Why?

Think About It

Identify W, X, and Y from the following choices:

Cross sectional area

Blood velocity Blood pressure

• As blood travels further from heart, blood pressure DECREASES

Blood Pressure

• Although capillaries are very tiny in diameter, they are numerous. Therefore, all capillaries together have a far greater cross-sectional area than arteries or veins

Cross-Sectional Area

• Velocity of blood DECREASES with an INCREASE in total cross-sectional area

Blood Velocity

• The velocity of blood flow varies in the vessels– is slowest in the capillary beds as a result of the high

resistance & large total cross-sectional area

Figure 42.11

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C5-e:1) Account for the changes in pressure, velocity, and cross-sectional area

in blood vessels.- pressure in vessels decreases as get further from heart- cross-sectional area is highest in capillaries due to greater number- velocity decreases in arteries as get further away from heart, and is lowest in capillaries (due to a high cross-sectional area) – velocity starts to increase as blood rejoins into veins

2) Explain how pressure and velocity help with tissue fluid exchange at the capillaries.- blood entering capillaries is under high pressure, causing fluids/solutes to diffuse into tissues – as blood continues through capillaries, pressure drops and fluids/solutes diffuse back into blood- velocity slows down in capillaries, allowing more time for exchange

PLO Journal

C5-f: 1) Describe how the capillary is well suited for tissue fluid exchange.

- Capillary walls are only one cell thick- Capillaries are narrow in diameter, keeping RBC’s in close proximity to tissues,

and resistance slows down blood- Capillaries receive blood high in pressure

2) Sketch a diagram at the capillary level to help show how eating salty foods can contribute to high blood pressure.- Diagram should show high concentration of salt in blood (capillaries), which

creates a greater osmotic force to draw water into capillaries, thus increasing blood pressure

3) Describe tissue fluid exchange at the capillary .- Fluids/solutes diffuse out of capillaries due to high blood pressure (which is

greater than the osmotic force to draw fluid into the blood)- As blood pressure decreases, osmotic force is then greater and fluids move

into the capillaries to dilute the high concentration of protein in the blood

PLO Journal