Bio Circulation And Gas Exchange

Front 1

what does the circulatory system do?

Back 1

transport nutrients, wastes, gases...

*

essential for the maintenance of cell function and homeostasis

*

associated with all tissues

Front 2

capillary beds

Back 2

* ensure that no substance has very far to diffuse

* are the sites of material exchanges between blood plasma and interstital fluid (the extracellular fluid, ECF, between the cells of other tissues)

Front 3

in most tissues...

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• O2 and nutrients diffuse from blood into interstitial fluid and from interstitial fluid into tissue

• CO2 and wastes diffuse from tissue into interstitial fluid and from interstitial fluid into blood

Front 4

The indirect exchange of materials between blood plasma and tissue cells occurs through

Back 4

interstitial fluid

Front 5

the circulatory system also functions in

homeostasis by...

Back 5

• aiding in the exchange of molecules with interstitial fluid

and
• moving blood through organs (eg. liver, kidneys) where the contents of blood are regulated

Front 6

hemolymph

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the fluid that moves through an insect’s open

circulatory system

Front 7

Open Circulatory System

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*

hemolymph is pumped by 1 or more pumps / tubular hearts through open-ended vessels and is released into the spaces between cells

Front 8

blood vessels in a closed circulatory system...

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* arteries

* arterioles

* capillaries

* venules

* veins

Front 9

arteries

Back 9

carry blood away from the heart

Front 10

arterioles

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carry blood from an artery to a capillary bed

Front 11

capillaries

Back 11

sites of exchange with interstitial

fluid

Front 12

venules

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carry blood from a capillary bed to a vein

Front 13

veins

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return blood to the heart

Front 14

what advantages are there to a closed vs. an open circulatory system?

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• rapid delivery
• blood can be directed to specific tissues
• formed elements and large molecules retained in the bloodstream • high levels of metabolic activity can be supported

Front 15

2 chambered heart and a single circuit (single circulation)

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• blood must pass through 2 capillary beds during each circuit ex) fish

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3 chambered heart and two circuits (double circulation)

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* 2 circuits improves the efficiency and capacity of the system
*

both the lungs and the skin are sites of re-oxygenation and so use a pulmocutaneous circuit

*

some mixing occurs in the single ventricle, but channels in the ventricle wall help divert the blood to

the correct circuit

*

Ex) amphibians

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4 chambered heart and double circulation

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• 2 atria and 2 ventricles
• the right side of the heart handles O2-poor blood
• the left side of the heart handles O2-rich blood

Ex) birds and mammals

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arteries Structure & Function

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*

thick-walled... connective tissue & smooth

muscle provide reinforcement

*

smooth muscle constricts to regulate flow

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veins Structure & Function

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• similar in structure to arteries, but have

valves to prevent backflow away from the heart

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capillaries Structure & Function

Back 20

*

thin walls (only 1 cell layer) facilitate

diffusion of substances

*

~80-100,000 kms of capillaries in

your body!

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Smooth Muscle

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Helps to Control the Distribution of Blood

*

blood supply varies in all tissues (except brain & heart)

*

arteriole constriction

*

thoroughfare channel

*

precapillary sphincters

Front 22

arteriole constriction

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(under control of nerves & hormones) can reduce flow to capillaries

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thoroughfare channel

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allows flow through centre of capillary bed

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precapillary sphincters

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control passage of most blood into the bed

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Capillaries Allow Transfer of Some Substances Through Their Walls

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* site where plasma & interstitial fluid exchange materials
*

water & small water-sol molecules can “leak” between endothelial cells

*

lipid-souble molecules can pass through the endothelial cells

*

blood pressure actively forces fluid out of capillaries, & osmosis tends to cause fluids to move in

*

some proteins are exchangeable between the plasma and interstitial fluid via endocytosis and

exocytosis

*

most plasma proteins are retained

Front 26

Lungs

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* highly vascularized internal sacs of the body surface
*

since lungs are localized in the body, the circulatory system must be employed to transport gases

Front 27

why is respiratory medium is air rather than water?

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air is less dense

easier to pump / move than water; less energy needed to ventilate lungs

Front 28

the respiratory surface is

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the moist epithelial lining of the alveoli

Front 29

lungs require less thorough ventilation than gills since

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*

gases diffuse faster in air than in water

*

there is more dissolved O2 in air than in water

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*

water loss is an issue when compared to the use of water as a respiratory medium because

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*

(exhaled air is moist)... breathing air could dry out the respiratory surface

Front 31

oxygen- poor blood is arriving from the

Back 31

pulmonary artery

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oxygen-rich blood is going to the

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pulmonary vein

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Dalton’s Law

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every gas in a mixture contributes to the total pressure of the mixture, each gas has a partial pressure

• the direction of diffusion for any gas at any body site is determined by differences in the partial pressures of that gas at those sites

o differences in partial pressures allow for gas exchange at various sites in the body