Bio 11 20102011 Human Circulation and Gas Exchange

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

IB Biology 2010/2011

Topic 6.2-Human Circulation & 6.4-Gas Exchange

RNS Science


Circulation, Gas Exchange & Cellular Respiration

Organismal level

Cellular level

Circulatory system

Cellular respiration ATPEnergy-richmoleculesfrom food

Respiratorysurface

Respiratorymedium(air of water)

O2 CO2


Overview: Trading with the Environment

• Every organism must exchange materials with its environment

– And this exchange ultimately occurs at the cellular level

• Transport systems

– Functionally connect the organs of exchange with the body cells


Open and Closed Circulatory Systems• More complex animals

– Have one of two types of circulatory systems: open or closed

• Both of these types of systems have three basic components

– A circulatory fluid (blood)

– A set of tubes (blood vessels)

– A muscular pump (the heart)


• Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.

– Care should be taken to show the relative wall thickness of the four chambers.

• State that the coronary arteries supply heart muscle with oxygen and nutrients.


The Heart of the matter…… (sorry)

• 2 thin-walled atria and 2 thicker-walled ventricles (left ventricle the thickest wall)

• Large artery, smaller arteries, arterioles, capillary bed, venule, veins, large veins

• Pulmonary and Systemic Circulation

• Follow that RBC though the entire ‘double circulation’ pattern (one or two minutes)


• The mammalian cardiovascular system

Pulmonary vein

Right atrium

Right ventricle

Posteriorvena cava Capillaries of

abdominal organsand hind limbs

Aorta

Left ventricle

Left atriumPulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Anteriorvena cava

Pulmonaryartery

Capillariesof right lung

Aorta

Figure 42.5

1

10

11

5

4

6

2

9

33

7

8


The Mammalian Heart: A Closer Look

– http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html

– Provides a better understanding of how double circulation works

Figure 42.6

Aorta

Pulmonaryveins

Semilunarvalve

Atrioventricularvalve

Left ventricleRight ventricle

Anterior vena cava

Pulmonary artery

Semilunarvalve

Atrioventricularvalve

Posterior vena cava

Pulmonaryveins

Right atrium

Pulmonaryartery

Leftatrium


• Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.

• A basic understanding is required, limited to the collection of blood by the atria, which is then pumped out by the ventricles into the arteries.

– The direction of flow is controlled by atrio-ventricular and semilunar valves.


Mammalian Circulation: The Pathway

• Heart valves dictate a one-way flow of blood through the heart

• Blood begins its flow with the right ventricle pumping blood to the lungs

• In the lung the blood loads O2 and unloads CO2

• Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle

• Blood returns to the heart through the right atrium


• The heart contracts and relaxes

– In a rhythmic cycle called the cardiac cycle

• The contraction, or pumping, phase of the cycle

– Is called systole

• The relaxation, or filling, phase of the cycle

– Is called diastole


• The cardiac cycle

Figure 42.7

Semilunarvalvesclosed

AV valvesopen

AV valvesclosed

Semilunarvalvesopen

Atrial and ventricular diastole

1

Atrial systole; ventricular diastole

2

Ventricular systole; atrial diastole

3

0.1 sec

0.3 sec0.4 sec


• The heart rate, also called the pulse

– Is the number of beats per minute

• The cardiac output

– Is the volume of blood pumped into the systemic circulation per minute


• Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).

• Histology of the heart muscle, names of nerves or transmitter substances are not required.


Control of Heart Rate……

• Cardiac muscle spontaneously contracts and relaxes without nervous system control = myogenic muscle contraction (this must be controlled to keep contractions unified)

• Sinoatrial node (SA) in the right atrium – sends out a signal to initiate contraction in the atria

• Atriventricular (AV) node receives impulse from SA node and sends an impulse for the ventricles to contract


More on Maintaining the Heart’s Rhythmic Beat…• Some cardiac muscle cells are self-excitable

– Meaning they contract without any signal from the nervous system

• A region of the heart called the sinoatrial (SA) node, or pacemaker

– Sets the rate and timing at which all cardiac muscle cells contract

• Impulses from the SA node

– Travel to the atrioventricular (AV) node

• At the AV node, the impulses are delayed

– And then travel to the Purkinje fibers that make the ventricles contract


• The control of heart rhythm

Figure 42.8

SA node(pacemaker)

AV node Bundlebranches

Heartapex

Purkinjefibers

2 Signals are delayedat AV node.

1 Pacemaker generates wave of signals to contract.

3 Signals passto heart apex.

4 Signals spreadThroughoutventricles.

ECG


• The pacemaker is influenced by nerves, hormones, and exercise:

– Exercise causes carbon dioxide levels to rise, which is sensed by the medulla area of the brainstem

– The medulla sends a signal through a cranial nerve (the cardiac nerve) to the SA node to increase heart rate

– As carbon dioxide level decreases with less activity, the medulla sends a signal through the vagus cranial nerve to the SA to slow the rate

– Adrenalin from the adrenal gland during ‘stress’ can also signal the SA node to pick up the heart rate


Blood Vessel Structure and Function

• Explain the relationship between the structure and function of arteries, capillaries and veins:

• The “infrastructure” of the circulatory system is its network of blood vessels

• Structural differences in arteries, veins, and capillaries correlate with their different functions

• Arteries have thicker walls to accommodate the high pressure of blood pumped from the heart


• All blood vessels

– Are built of similar tissues

– Have three similar layers

Figure 42.9

Artery Vein

100 µm

Artery Vein

ArterioleVenule

Connectivetissue

Smoothmuscle

Endothelium

Connectivetissue

Smoothmuscle

EndotheliumValve

Endothelium

Basementmembrane

Capillary


• In the thinner-walled veins

– Blood flows back to the heart mainly as a result of muscle action

Figure 42.10

Direction of blood flowin vein (toward heart)

Valve (open)

Skeletal muscle

Valve (closed)


Quick Comparison of Arteries, Capillaries, & Veins

Artery Capillary Vein

Carries blood away from heart

Connects arterioles and venules

Carries blood toward the heart

Thick walled Wall is 1 cell thick Thin walled

No exchanges All exchanges occur No exchanges

No internal valves No internal valves Have internal valves

Internal pressure high Internal pressure low Internal pressure low


Blood Pressure

• Blood pressure

– Is the hydrostatic pressure that blood exerts against the wall of a vessel

• Systolic pressure

– Is the pressure in the arteries during ventricular systole

– Is the highest pressure in the arteries

• Diastolic pressure

– Is the pressure in the arteries during diastole

– Is lower than systolic pressure


• Blood pressure

– Can be easily measured in humans

Figure 42.12

Artery

Rubber cuffinflatedwith air

Arteryclosed

120 120

Pressurein cuff above 120

Pressurein cuff below 120

Pressurein cuff below 70

Sounds audible instethoscope

Sounds stop

Blood pressurereading: 120/70

A typical blood pressure reading for a 20-year-oldis 120/70. The units for these numbers are mm of mercury (Hg); a blood pressure of 120 is a force that can support a column of mercury 120 mm high.

1

A sphygmomanometer, an inflatable cuff attached to apressure gauge, measures blood pressure in an artery.The cuff is wrapped around the upper arm and inflated until the pressure closes the artery, so that no blood flows past the cuff. When this occurs, the pressure exerted by the cuff exceeds the pressure in the artery.

2 A stethoscope is used to listen for sounds of blood flow below the cuff. If the artery is closed, there is no pulse below the cuff. The cuff is gradually deflated until blood begins to flow into the forearm, and sounds from blood pulsing into the artery below the cuff can be heard with the stethoscope. This occurs when the blood pressure is greater than the pressure exerted by the cuff. The pressure at this point is the systolic pressure.

3

The cuff is loosened further until the blood flows freely through the artery and the sounds below the cuff disappear. The pressure at this point is the diastolic pressure remaining in the artery when the heart is relaxed.

4

70


• Blood pressure is determined partly by cardiac output

– And partly by peripheral resistance due to variable constriction of the arterioles


Capillary Function

• Capillaries in major organs are usually filled to capacity

– But in many other sites, the blood supply varies


• Two mechanisms

– Regulate the distribution of blood in capillary beds

• In one mechanism

– Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel


• In a second mechanism

– Precapillary sphincters control the flow of blood between arterioles and venules

Figure 42.13 a–c

Precapillary sphincters Thoroughfarechannel

ArterioleCapillaries

Venule(a) Sphincters relaxed

(b) Sphincters contractedVenuleArteriole

(c) Capillaries and larger vessels (SEM)

20 m


• The critical exchange of substances between the blood and interstitial fluid

– Takes place across the thin endothelial walls of the capillaries


• State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets.

• State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.


Blood Composition and Function

• Blood consists of several kinds of cells

– Suspended in a liquid matrix called plasma

• The cellular elements (hematocrit)

– Occupy about 45% of the volume of blood


Plasma

• Blood plasma is about 90% water

• Among its many solutes are

– Inorganic salts in the form of dissolved ions, sometimes referred to as electrolytes


• The composition of mammalian plasmaPlasma 55%

Constituent Major functions

Water Solvent forcarrying othersubstances

SodiumPotassiumCalciumMagnesiumChlorideBicarbonate

Osmotic balancepH buffering, andregulation of membranepermeability

Albumin

Fibrinogen

Immunoglobulins(antibodies)

Plasma proteins

Ions (blood electrolytes)

Osmotic balance,pH buffering

Substances transported by bloodNutrients (such as glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones

Defense

Figure 42.15

Separatedbloodelements

Clotting


• Another important class of solutes is the plasma proteins

– Which influence blood pH, osmotic pressure, and viscosity

• Various types of plasma proteins

– Function in lipid transport, immunity, and blood clotting


Cellular Elements

• Suspended in blood plasma are two classes of cells

– Red blood cells, which transport oxygen

– White blood cells, which function in defense

• A third cellular element, platelets

– Are fragments of cells that are involved in clotting


Figure 42.15

Cellular elements 45%

Cell type Numberper L (mm3) of blood

Functions

Erythrocytes(red blood cells) 5–6 million Transport oxygen

and help transportcarbon dioxide

Leukocytes(white blood cells)

5,000–10,000 Defense andimmunity

Eosinophil

Basophil

Platelets

NeutrophilMonocyte

Lymphocyte

250,000400,000

Blood clotting

• The cellular elements of mammalian blood

Separatedbloodelements


Erythrocytes

• Red blood cells, or erythrocytes

– Are by far the most numerous blood cells

– Transport oxygen throughout the body


Leukocytes & Platelets

• The blood contains five major types of white blood cells, or leukocytes

– Monocytes, neutrophils, basophils, eosinophils, and lymphocytes, which function in defense by phagocytizing bacteria and debris or by producing antibodies

• Platelets function in blood clotting


Bloody Summary…..• Components of Blood

• Transport by Blood

Component Description

plasma Liquid portion of blood

erythrocytes Red blood cells(carry oxygen and carbon dioxide)

leukocytes White blood cells (phagocytes and lymphocytes)

platelets Cell fragments (assist in blood clotting

What is transported What it is or does

Nutrients Glucose, amino acids, etc

Oxygen Reactant for cell respiration

Carbon dioxide Waste product of cell respiration

Hormones Transported from gland to target cell

Antibodies Protein molecules involved in immunity

Urea Nitrogenous waste (filtered out of blood by kidneys)

Heat Skin arterioles – vasodilation or vasoconstriction


Gas Exchange

• Occurs across specialized respiratory surfaces

• Supplies oxygen for cellular respiration and disposes of carbon dioxide

Organismal level

Cellular level

Circulatory system

Cellular respiration ATPEnergy-richmoleculesfrom food

Respiratorysurface

Respiratorymedium(air of water)

O2 CO2


Gas Exchange

• Distinguish between ventilation, gas exchange and cell respiration.

– Ventilation – drawing air in and out of the lungs

– Gas Exchange – occurs at capillary beds

– Cell Respiration – see earlier stuff on mitochondrion

•


• Explain the need for a ventilation system.

– A ventilation system is needed to maintain high concentration gradients in the alveoli.

– Humans are too thick….

• In mammals, air inhaled through the nostrils

– Passes through the pharynx into the trachea, bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs


• Concept 42.6: Breathing ventilates the lungs

• The process that ventilates the lungs is breathing

– The alternate inhalation and exhalation of air

– Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the intercostal muscles, the diaphragm and abdominal muscles.


Tidal Ventilation in Humans

• Lung volume increases

– As the rib muscles (external intercostals) and diaphragm contract

• Lung Volume decreases due to

either

– Relaxation of diaphragm and external intercostals and the natural elasticity of lung tissue

or– Forced out by contraction of the internal

intercostals (and abdominal muscles)


• Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli.

– Students should draw the alveoli in an inset diagram at a higher magnification.


Mammalian Respiratory Systems: A Closer Look

• A system of branching ducts

– Conveys air to the lungsBranch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole

Branch from thepulmonaryartery(oxygen-poor blood)

Alveoli

Colorized SEMSEM

50 µ

m

50 µ

m

Heart

Left lung

Nasalcavity

Pharynx

Larynx

Diaphragm

Bronchiole

Bronchus

Right lung

Trachea

Esophagus

Figure 42.23


• Describe the features of alveoli that adapt them to gas exchange.

– This should include a large total surface area,

– a wall consisting of a single layer of flattened cells,

– a film of moisture and a dense network of capillaries.


Inhaled air Exhaled air

160 0.2O2 CO2

O2 CO2

O2 CO2

O2 CO2 O2 CO2

O2 CO2 O2 CO2

O2 CO2

40 45

40 45

100 40

104 40

104 40

120 27

CO2O2

Alveolarepithelialcells

Pulmonaryarteries

Blood enteringalveolar

capillaries

Blood leavingtissue

capillaries

Blood enteringtissue

capillaries

Blood leaving

alveolar capillaries

CO2O2

Tissue capillaries

Heart

Alveolar capillaries

of lung

<40 >45

Tissue cells

Pulmonaryveins

Systemic arteriesSystemic

veinsO2

CO2

O2

CO 2

Alveolar spaces

12

43

Figure 42.27

Bio 11 20102011 Human Circulation and Gas Exchange

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