Transcript The Living World - Chapter 25 - McGraw Hill Higher Education

Essentials of
The Living World
First Edition
GEORGE B. JOHNSON
20
Circulation and
Respiration
PowerPoint® Lectures prepared by Johnny El-Rady
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20.1 Open and Closed
Circulatory Systems
Cnidarians and flatworms
have a gastrovascular cavity
that functions in both
digestion and circulation
Fig. 20.1
Larger animals transport oxygen and nutrients from
the environment and digestive cavity to body cells
via a circulatory system
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Open circulatory system
In mollusks and arthropods
No distinction between
circulating fluid (blood) and
fluid of the body tissues
(lymph)
Hemolymph
Fig. 20.1
Closed circulatory system
In annelids and vertebrates
Circulating fluid (blood) is
always enclosed within
vessels that transport blood
away from, and back to a
pump (heart)
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In vertebrates, blood vessels from a tubular network
Arteries carry blood away from the heart
Veins return blood to the heart
Capillaries connect arteries to veins
As blood plasma passes through capillaries,
pressure forces fluid out of the capillary walls
Some of this interstitial fluid returns directly
to capillaries
Some enters lymph vessels
This lymph is returned to venous blood at
specific sites
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Functions of Vertebrate Circulatory Systems
1. Transportation
Respiratory
Transport O2 to cells for aerobic respiration
Transport CO2 to lungs/gills for elimination
Nutritive
Transport of absorbed products of digestion to cells
Excretory
Metabolic wastes and excessive water are filtered in the
kidney and excreted in urine
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2. Regulation
Fig. 20.2
Hormones are transported
from endocrine glands to
distant target organs
Help maintain a constant
body temperature in
homeotherms
Some vertebrates use
a countercurrent heat
exchange
3. Protection
Warm blood going out heats
cold blood coming in
Blood clotting protects against blood loss
White blood cells provide immunity against manydisease causing agents
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20.2 Architecture of the Vertebrate
Circulatory System
The cardiovascular system of vertebrates consists of
1. Heart
Pump
2. Blood vessels
Network of tubes
3. Blood
Circulating fluid
Fig. 20.8 The flow of blood
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Fig. 20.3 The capillary network connects arteries with veins
Blood loses most of its pressure and velocity as it
passes through the vast capillary network
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Arteries: Highways from the Heart
Blood comes from the
heart in large pulses
Thus the artery must
be able to expand
Arterial walls are made
up of three layers
Fig. 20.4a
Arterioles are smaller in diameter than arteries
Their surrounding muscle layer can be relaxed to
enlarge diameter
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Capillaries: Where Exchange Takes Place
Transport oxygen and
nutrients from blood to
body’s cells and pick up
carbon dioxide
They have thin walls
to allow diffusion to
take place
Fig. 20.4b
Individual capillaries have high resistance to flow
But the total cross-sectional area of capillaries is
greater than that of arteries leading to it
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Veins: Returning Blood to the Heart
Fig. 20.4c
Walls have thinner
layers of muscle and
elastic fiber than arteries
Fig. 20.6
Vein
Artery
When empty, walls
collapse
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Veins: Returning Blood to the Heart
Blood flow back to the
heart is aided by
1. Low pressure
in veins
2. Skeletal
muscles
3. Unidirectional
valves
Fig. 20.7
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20.3 The Lymphatic System:
Recovering Lost Fluid
The cardiovascular
system is very leaky
To collect and recycle
leaked fluid, the body
uses a second
circulatory system called
the lymphatic system
Fig. 20.9
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Blood pressure forces fluid out of capillaries
Most of this interstitial fluid returns by osmosis
Excess fluid is drained into lymphatic capillaries
In the lymphatic system the fluid is called lymph
Fig. 20.10
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Lymphatic vessels contain a series of one-way valves
Permit movement only in the direction of the neck
The lymphatic system has three important functions
1. Returns proteins to circulation
If proteins are not returned to the blood, a condition called
edema (body swelling) results
2. Transports fats absorbed from the intestine
Lymph capillaries, called lacteals, absorb fats from the
small intestine
3. Aids in the body’s defense
Lymph nodes are filled with white blood cells
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20.4 Blood
Blood comprises about 5% of body mass
It is composed of
A fluid called plasma
Several different kinds of cells
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Blood Plasma: The Body’s Fluid
Blood plasma is a complex solution of water and
1. Metabolites and wastes
Glucose, vitamins, hormones and wastes
2. Salts and ions
Chief plasma ions: sodium, chloride, bicarbonate
Minor ions: calcium, magnesium, copper
3. Proteins
Act as an osmotic counterforce
Major protein: serum albumin
Other proteins: fibrinogen and antibodies
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Blood Cells Circulate Through the Body
The fraction of blood volume that is occupied by
cells is termed the blood’s hematocrit
In humans it is usually about 45%
The three principal types of blood cells are
Erythrocytes
Leukocytes
Platelets
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Erythrocytes (red blood cells)
Carry hemoglobin, and therefore, oxygen to cells
Do not contain a nucleus
Leukocytes (white blood cells)
Defend the body against microbes and foreign
substance
Neutrophils
Monocytes/Macrophages
Lymphocytes
B cells – Produce antibodies
T cells – Drill holes in invading bacteria
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Platelets
Cell fragments that are bits of the cytoplasm of
large bone marrow cells called megakaryocytes
Do not contain a
nucleus
Play a key role in
blood clotting
Stimulate the
formation of
fibrin from
fibrinogen
Fibrin
Fig. 20.11
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Fig. 20.12
Types of
blood cells
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Fig. 20.12
Types of
blood cells
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20.5 Fish Circulation
The fish heart is a tube consisting of four chambers
Sinus venosus
and atrium, are
collection
chambers
Ventricle and
conus arteriosus,
are pumping
chambers
Fig. 20.13a
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The heart beat in fishes has a peristaltic sequence
Starts at the rear (SV) and moves to the front
Gill respiration provides
fully oxygenated blood
to the body
However, circulation
is sluggish
This limits rate of
oxygen delivery to
rest of body
Fig. 20.13b
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20.6 Amphibian and Reptile
Circulation
The advent of lungs resulted in two circulations
1. Pulmonary circulation
Delivers blood to the lungs
2. Systemic circulation
Delivers blood to the rest of the body
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The amphibian heart has two structural features that
reduce mixing of oxygenated & deoxygenated blood
1. The atrium is
divided into two
chambers by a
septum
2. Conus
arteriosus is
partially separated
by another septum
Fig. 20.14a
Amphibians in water supplement the oxygenation of
blood by a process called cutaneous respiration
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Among reptiles, additional modifications have further
reduced the mixing of blood in the heart
The ventricle is
partially divided
into two chambers
by a septum
The separation
is complete in
the crocodiles
Fig. 20.14b
They thus have completely divided
pulmonary and systemic circulation
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20.7 Mammalian and Bird
Circulation
Mammals and birds have a four-chambered heart
that is really two separate pumping systems
One pumps blood to the lungs
The other pumps blood to the rest of the body
The two pumps operate together within a single
unit
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Circulation Through the Heart
Oxygenated blood from lungs empties into the left
atrium through the pulmonary veins
Then from the atrium to the left ventricle
Ventricle contracts forcing blood out in a single
strong pulse
Bicuspid (mitral) valve prevents backflow
Blood then moves into the aorta
Aortic valve prevents backflow into ventricle
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Circulation Through the Heart
Blood eventually returns to the heart
The superior vena cava drains the upper body
The inferior vena cava drains the lower body
Blood passes from the right atrium into the right
ventricle through the one-way tricuspid valve
Ventricle contracts forcing blood through the
pulmonary valve into the pulmonary arteries
Oxygenated blood eventually returns to the
heart
It is then pumped to the rest of the body
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Fig. 20.15 The heart and circulation of mammals and birds
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How the Heart Contracts
Heartbeat originates in the sinoatrial (SA) node
Its membranes spontaneously depolarize
This wave of depolarization spreads to the atria,
causing them to contract
The wave reaches the atrioventricular (AV) node
It passes to the ventricles via the Bundle of His
It is then conducted rapidly over the surface
of the ventricles by Purkinje fibers
Ventricular contraction empties the heart
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Fig. 20.16 How the mammalian heart contracts
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Electrocardiogram (ECG or EKG)
Shows how heart cells depolarize and repolarize
Depolarization causes contraction of the heart
Repolarization causes relaxation of the heart
Depolarization of
the ventricles
Depolarization
of the atria
Repolarization
of the ventricles
Fig. 20.16
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Monitoring the Heart’s Performance
Simplest way is to listen to the heart at work using a
stethoscope
If valves are not fully opening or closing,
turbulence is created
This can be heard as a heart murmur
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Another way is to monitor blood pressure
A sphygmomanometer is used to record two measurements
Systolic pressure – High point
Diastolic pressure – Low point
Fig. 20.17
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20.8 Cardiovascular Diseases
The leading cause of deaths in the US
Heart attacks
Caused by an insufficient supply of blood to one or more
parts of the heart muscle
Also called myocardial infarctions
Angina pectoris (“Chest pain”)
Warning sign of a potential heart attack
Strokes
Caused by interference with blood flow to brain
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Atheroscleroris
Accumulation of fatty materials on inner surfaces of artery
The lumen (interior) becomes narrower
Fig. 20.18
Arterioscleroris
Hardening of the arteries
Occurs when calcium is deposited in arterial walls
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Treatment of Blocked Coronary Arteries
Atherosclerosis is treated with
1. Medications
Enzymes
Anticoagulants
Nitroglycerin
2. Invasive procedures
Heart transplants
Coronary bypass surgery
Angioplasty
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20.9 Types of Respiratory Systems
Respiration is the uptake of oxygen and the
simultaneous release of carbon dioxide
Most of the primitive phyla of organisms obtain
oxygen by direct diffusion from seawater
Fig. 20.19
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Aquatic animals
possess special
respiratory organs
called gills
Fig. 20.19
Terrestrial
arthropods use a
network of air ducts
called trachea
Terrestrial
vertebrates use
respiratory organs
called lungs
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20.10 Respiration in
Aquatic Vertebrates
A fish continuously opens and closes its mouth
It pushes water through mouth and out of gills
This permits countercurrent flow
Oxygenated water flows through the gills in a
direction opposite blood flow in the capillaries
The higher oxygen concentration in water
drives the diffusion of oxygen into blood
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Fig. 20.20 Structure of a fish gill
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Diffusion
continues
Fig. 20.21
Countercurrent
flow
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No further
net diffusion
20.11 Respiration in
Terrestrial Vertebrates
Amphibians on land are able to respire through moist
skin
However, the main respiration route is the lung
A sac with a convoluted internal membrane
Reptiles are more active so they need more oxygen
But they cannot respire through skin
Instead, their lungs contain many more small
chambers, greatly increasing the surface area
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20.11 Respiration in
Terrestrial Vertebrates
Mammals have an even greater oxygen demand
because they maintain a constant body temperature
They increase the lung surface area even more
Alveoli
Small chambers in interior of lung
Bronchioles
Short passageways connecting clusters of
alveoli
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Fig. 20.22 Evolution of the vertebrate lung
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Birds Perfect the Lung
Flying creates a very large oxygen demand
Therefore, birds must possess very efficient lungs
Air flows through the lungs in one direction
This one-way air flow results in
1. No dead volume
Air is always fully oxygenated
2. A crosscurrent flow
Blood leaving the lung can still
contain more oxygen than exhaled air
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Fig. 20.23 How a bird breathes
Most efficient
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20.12 The Mammalian
Respiratory System
A pair of lungs hang free in the thoracic cavity
An air tube called bronchus connects each lung to
a trachea
Air normally enters through the nostrils
It passes to the larynx (voice box) and then the
trachea
And then through the bronchus to the lungs
Lungs contain millions of alveoli
Sites of gas exchange between air and blood
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Fig. 20.24
The human
respiratory
system
Each lung is
covered by a
pleural membrane
The thoracic cavity is bounded on the bottom by a thick layer
of muscle called the diaphragm
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The Mechanics of Breathing
Breathing – Active pumping of air in and out of lungs
During inhalation
Diaphragm contracts and flattens
Chest cavity expands downwards and outwards
This creates negative pressure in lungs and air rushes in
During exhalation
Diaphragm relaxes
Volume of chest cavity decreases
Pressure in lungs increases and air is forced out
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Fig. 20.25 How breathing works
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The Mechanics of Breathing
In a human, a typical breath at rest moves about 0.5
liters of air called the tidal volume
When each breath is completed, the lung still contains
a volume of air (~ 1.2 liters) called the residual volume
Each inhalation adds from 500 milliliters (resting) to
3,000 milliliters (exercising) of additional air
Each exhalation removes approximately the
same volume as inhalation added
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20.13 How Respiration Works:
Gas Exchange
Oxygen moves
within the
circulatory system
carried piggyback
on the protein
hemoglobin
Hemoglobin
contains iron,
which combines
with oxygen in a
reversible way
Fig. 20.26
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O2 Transport
Hemoglobin bind O2 within red blood cells (RBCs)
This causes more to diffuse in from blood
plasma
In the lungs, most hemoglobin molecules carry a
full load of O2
The presence of carbon dioxide (CO2) in tissues
speeds up the unloading of O2
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CO2 Transport
As red blood cells are unloading O2 they are also
absorbing CO2 from the tissue
The enzyme carbonic anhydrase combines CO2
and H2O to form carbonic acid (H2CO3–)
This acid dissociates into bicarbonate (HCO3–)
and hydrogen (H+)
A transporter protein moves one bicarbonate
out of the RBC and brings in one chloride ion
This “chloride shift” facilitates the diffusion
of more CO2 into the RBC
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CO2 Transport
RBC carry the bicarbonate ions back to the lungs
There, the lower CO2 concentration causes the
carbonic anhydrase reaction to occur in reverse
CO2 is released from RBC and ultimately
exhaled
Hemoglobin can now pick up O2 again
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Fig. 20.27
How
respiratory
gas
exchange
works
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NO Transport
Hemoglobin also has the ability to hold and release
the gas nitric oxide (NO)
NO causes dilates blood vessels
Thus, it regulates blood flow and blood pressure
Hemoglobin picks up NO in the lungs and releases it
in the tissues
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20.14 The Nature of Lung Cancer
One of the leading causes of deaths among adults
in the world
Fig. 20.28
The incidence of
cancer is not
uniform throughout
the US
This suggests
environmental factors
Most carcinogens
are also mutagens
High incidence in
cities and
Mississippi Delta
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Cancer-causing genes are involved in regulating
cell growth and division
Tumor suppressor genes actively prevent tumors
from forming
Rb
Encodes the Rb protein
Slows down cell division by inhibiting DNA replication
p53
Encodes the p53 protein
Inspects the DNA for damage before
If DNA repair is unsuccessful, the cell is destroyed
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Fig. 20.29 The roles Rb and p53 play in controlling cell division
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Smoking Causes Lung Cancer
After the incidence of smoking began to increase in
the US, so did the incidence of lung cancer
Fig. 20.30
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Smoking Causes Lung Cancer
Cigarette smoke contains many powerful mutagens
Benzo[a]pyrene binds to three sites in the p53
gene
Mutations at these sites inactivate the gene
Research found that the p53 gene is inactivated in
70% of all lung cancers
Moreover, the inactivating mutations occurred at
the binding sites of benzo[a]pyrene!
Nicotine in cigarette smoke is an addictive drug!
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