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Blood Clotting• A cascade of complex reactions
– Converts fibrinogen to fibrin, forming a clot
Plateletplug
Collagen fibers
Platelet releases chemicalsthat make nearby platelets sticky
Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)
Prothrombin Thrombin
Fibrinogen Fibrin5 µm
Fibrin clotRed blood cell
The clotting process begins when the endothelium of a vessel is damaged, exposing connective tissue in the vessel wall to blood. Plateletsadhere to collagen fibers in the connective tissue and release a substance thatmakes nearby platelets sticky.
1 The platelets form a plug that providesemergency protectionagainst blood loss.
2 This seal is reinforced by a clot of fibrin when vessel damage is severe. Fibrin is formed via amultistep process: Clotting factors released fromthe clumped platelets or damaged cells mix withclotting factors in the plasma, forming an activation cascade that converts a plasma proteincalled prothrombin to its active form, thrombin.Thrombin itself is an enzyme that catalyzes the final step of the clotting process, the conversion of fibrinogen to fibrin. The threads of fibrin become interwoven into a patch (see colorized SEM).
3
Figure 42.17
A baby aspirin per day makes the platelets lazy!
Hemophiliacs
Cardiovascular Disease• Cardiovascular diseases
– Are disorders of the heart and the blood vessel and account for more than half the deaths in the United States
• One type of cardiovascular disease, atherosclerosis– Is caused by the buildup of cholesterol within arteries (low
density lipoprotein complexes with cholesterol)
Figure 42.18a, b
(a) Normal artery (b) Partly clogged artery50 µm 250 µm
Smooth muscleConnective tissue Endothelium Plaque
Plaques sites of inflammation and can cause a clot to form if plaque splits open! Aspirin!
Thrombus!
• Hypertension, or high blood pressure– Promotes plaque formation and increases the risk of
heart attack and stroke
• A heart attack– Is the death of cardiac muscle tissue resulting from
blockage of one or more coronary arteries– Either by plaque build up or a clot (thrombus) formed
elsewhere and lodging in the vessel. Angina (pain in chest) Nitroglycerin-explosive! Releases nitric oxide relaxe arterioles.
• A stroke– Is the death of nervous tissue in the brain, usually
resulting from rupture or blockage of arteries in the head (clot dissolving enzymes useful if administered immediately).
• Concept 42.5: Gas exchange occurs across specialized respiratory surfaces
• Gas exchange– Supplies oxygen for cellular respiration and
disposes of carbon dioxide
Figure 42.19
Organismal level
Cellular level
Circulatory system
Cellular respiration ATPEnergy-richmoleculesfrom food
Respiratorysurface
Respiratorymedium(air of water)
O2 CO2
Oxygen is final electron acceptor in electron transport chain!!
• Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases– Between their cells and the respiratory medium
which can be either air or water
• Gills are outfoldings of the body surface specialized for gas exchange in aquatic animals
• In some invertebrates– The gills have a simple shape and are
distributed over much of the body
(a) Sea star. The gills of a sea star are simple tubular projections of the skin. The hollow core of each gillis an extension of the coelom(body cavity). Gas exchangeoccurs by diffusion across thegill surfaces, and fluid in thecoelom circulates in and out ofthe gills, aiding gas transport. The surfaces of a sea star’s tube feet also function in gas exchange.
Gills
Tube foot
Coelom
Figure 42.20a
• Many segmented marine worms (Annelids) have flaplike gills
– That extend from each segment of their body
Figure 42.20b
(b) Marine worm. Many polychaetes (marine worms of the phylum Annelida) have a pair of flattened appendages called parapodia on each body segment. The parapodia serve as gillsand also function incrawling and swimming.
Gill
Parapodia
• The gills of clams, crayfish, and many other animals– Are restricted to a local body region
Figure 42.20c, d
(d) Crayfish. Crayfish and other crustaceanshave long, feathery gills covered by the exoskeleton. Specialized body appendagesdrive water over the gill surfaces.
(c) Scallop. The gills of a scallop are long, flattened plates that project from themain body mass inside the hard shell.Cilia on the gills circulate water around the gill surfaces.
Gills
Gills
• The effectiveness of gas exchange in some gills, including those of fishes– Is increased by ventilation and
countercurrent flow of blood and water
Countercurrent exchange. Very efficient for extracting oxygen from water!
Figure 42.21
Gill arch
Water flow Operculum
Gill arch
Blood vessel
Gillfilaments
Oxygen-poorblood
Oxygen-richblood
Water flowover lamellaeshowing % O2
Blood flowthrough capillariesin lamellaeshowing % O2
Lamella
100%
40%
70%
15%
90%
60%
30% 5%
O2
Ram jet ventilation!
Figure 42.22a
Tracheae
Air sacs
Spiracle
(a) The respiratory system of an insect consists of branched internaltubes that deliver air directly to body cells. Rings of chitin reinforcethe largest tubes, called tracheae, keeping them from collapsing. Enlarged portions of tracheae form air sacs near organs that require a large supply of oxygen. Air enters the tracheae through openings called spiracles on the insect’s body surface and passes into smaller tubes called tracheoles. The tracheoles are closed and contain fluid(blue-gray). When the animal is active and is using more O2, most ofthe fluid is withdrawn into the body. This increases the surface area of air in contact with cells.
Tracheal Systems in Insects• The tracheal system of insects
– Consists of tiny branching tubes that penetrate the body
• The tracheal tubes– Supply O2 directly to body cells
Airsac
Body cell
Trachea
Tracheole
TracheolesMitochondria
Myofibrils
Body wall
(b) This micrograph shows crosssections of tracheoles in a tinypiece of insect flight muscle (TEM).Each of the numerous mitochondriain the muscle cells lies within about5 µm of a tracheole.
Figure 42.22b 2.5 µm
Air
Spiders, land snails, and most terrestrial vertebrates have internal lungs.
In mammals a system of branching ducts conveys air to the lungs
Branch 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
Capillary web over alveoli
• In mammals, air inhaled through the nostrils– Passes through the pharynx into the trachea,
bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs across a thin layer of water and the plasma membrane!
How an Amphibian Breathes
• An amphibian such as a frog– Ventilates its lungs by positive pressure
breathing, which forces air down the trachea.– Mammals ventilate using negative pressure
breathing.– Reptiles also use negative pressure but have
no diaphragm
How a Mammal Breathes• Mammals ventilate their lungs
– By negative pressure breathing, which pulls air into the lungs
Air inhaled Air exhaled
INHALATIONDiaphragm contracts
(moves down)
EXHALATIONDiaphragm relaxes
(moves up)
Diaphragm
Lung
Rib cage expands asrib muscles contract
Rib cage gets smaller asrib muscles relax
Figure 42.24
How a Bird Breathes• Besides lungs, bird have eight or nine air sacs
– That function as bellows that keep air flowing through the lungs in a one way direction
INHALATIONAir sacs fill
EXHALATIONAir sacs empty; lungs fill
Anteriorair sacs
Trachea
Lungs LungsPosteriorair sacs
Air Air
1 mm
Air tubes(parabronchi)in lung
Figure 42.25
• Air passes through the lungs– In one direction only
• Every exhalation– Completely renews the air in the lungs.– Thus birds are much more efficient in extracting
oxygen from the air and thus can fly at altitudes of 30,000 feet. Humans can barely climb stair at this elevation (Mount Everest climbers need oxygen!)
Control of Breathing in Humans• The main breathing control centers
– Are located in two regions of the brain, the medulla oblongata and the pons
Figure 42.26
PonsBreathing control centers Medulla
oblongata
Diaphragm
Carotidarteries
Aorta
Cerebrospinalfluid
Rib muscles
In a person at rest, these nerve impulses result in
about 10 to 14 inhalationsper minute. Between
inhalations, the musclesrelax and the person exhales.
The medulla’s control center also helps regulate blood CO2 level. Sensors in the medulla detect changes in the pH (reflecting CO2
concentration) of the blood and cerebrospinal fluid bathing the surface of the brain.
Nerve impulses relay changes in
CO2 and O2 concentrations. Other sensors in the walls of the aortaand carotid arteries in the neck detect changes in blood pH andsend nerve impulses to the medulla. In response, the medulla’s breathingcontrol center alters the rate anddepth of breathing, increasing bothto dispose of excess CO2 or decreasingboth if CO2 levels are depressed.
The control center in themedulla sets the basic
rhythm, and a control centerin the pons moderates it,
smoothing out thetransitions between
inhalations and exhalations.
1
Nerve impulses trigger muscle contraction. Nerves
from a breathing control centerin the medulla oblongata of the
brain send impulses to thediaphragm and rib muscles, stimulating them to contract
and causing inhalation.
2
The sensors in the aorta andcarotid arteries also detect changesin O2 levels in the blood and signal the medulla to increase the breathing rate when levels become very low.
6
5
3
4
• The centers in the medulla– Regulate the rate and depth of breathing in
response to pH changes in the cerebrospinal fluid
• The medulla adjusts breathing rate and depth– To match metabolic demands
• Sensors in the aorta and carotid arteries– Monitor O2 and CO2 concentrations in the blood– Exert secondary control over breathing– At high altitudes the oxygen sensors kick in and
causes deep rapid breathing. This “blows” off excess carbon dioxide making ones blood alkaline and gives one head aches (don’t feel well either). Some people more susceptible to altitude sickness than others (10,000 ft for some).
Respiratory pigments bind and transport gases
• The metabolic demands of many organisms require that the blood transport large quantities of O2 and CO2. The amount is more than can be physically dissolved in solution! Thus the need for respiratory pigments.
Composition of air and solubility of gases in water
• Air pressure at sea level =760 mmHg• Air is 78% Nitrogen, 21% Oxygen and .2%
Carbon dioxide. Each gas exerts it pressure independently of the other.
• Thus the partial pressure of O2 =.21 X 760= ~160 mmHg, N2 600 mmHg and CO2 .23mmHg
• Solubility of pure gas in one liter of water. O2 = 49 ml/l, N2 =24 ml/l,CO2 = 1713 ml/l
• Temperature decreases, increase solubility• Salt decreases solubility• Thus, an aquatic animal living in a tropical tide
pool doesn’t have access to much oxygen in the water.
• A gas always diffuses from a region of higher partial pressure too a region of lower partial pressure
• Gases diffuse down pressure gradients in the lungs and other organs
• In the lungs and in the tissues– O2 and CO2 diffuse from where their partial
pressures are higher to where they are lower
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
Exhaled air contains a lot of oxygen because of mixing in dead end space!
0.5 liter tidal volume
4.8 l vital capacity
1.2 l residual space
Need for Respiratory Pigments
• Respiratory pigments are proteins that bind and transport oxygen
• Can only dissolve 4.5 ml of oxygen in a liter of blood without Hb. – Greatly increase the amount of oxygen that
blood can carry (200 ml of oxygen /liter)
Oxygen Transport
• The respiratory pigment of almost all vertebrates is the protein hemoglobin, contained in the erythrocytes
• In invertebrates that have pigments they are hemocyanin, a large copper containing protein that circulates free in solution ( not housed in cells like hemoglobin).
Hemoglobin a tetrameric molecule• Like all respiratory pigments
– Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body
Heme group Iron atom
O2 loadedin lungs
O2 unloadedIn tissues
Polypeptide chain
O2
O2
Figure 42.28
• Loading and unloading of O2
– Depend on cooperation between the subunits of the hemoglobin molecule
• The binding of O2 to one subunit induces the other subunits to bind O2 with more affinity
• Cooperative O2 binding and release
– Is evident in the dissociation curve for hemoglobin
• A drop in pH– Lowers the affinity of hemoglobin for O2
O2 unloaded fromhemoglobinduring normalmetabolism
O2 reserve that canbe unloaded fromhemoglobin totissues with highmetabolism
Tissues duringexercise
Tissuesat rest
100
80
60
40
20
0
100
80
60
40
20
0
100806040200
100806040200
Lungs
PO2 (mm Hg)
PO2 (mm Hg)
O2 s
atur
atio
n of
hem
oglo
bin
(%)
O2 s
atur
atio
n of
hem
oglo
bin
(%)
Bohr shift:Additional O2
released from hemoglobin at lower pH(higher CO2
concentration)
pH 7.4
pH 7.2
(a) PO2 and Hemoglobin Dissociation at 37°C and pH 7.4
(b) pH and Hemoglobin Dissociation
Figure 42.29a, b
Arterial Blood O2 saturation and O2 content
0
20
40
60
Arterial blood
% O2saturation
PO2 (mm Hg)
OContent
(vol. %)(= mL O2
per 100mL blood)
2 80
100
30 60 90
0
10
20
5
15
O2 content vs PO2 for different animals
50 100
10
20
30
mL O2
per100 mLblood
(vol %)
PO2 (mm Hg)0
Human20 vol %
Mackerel 14 vol %
Bullfrog6 vol%
Dissolved O20.3vol%
Mud flatworm
Weddell seal~32 vol %
(diver)
(see also WSJ Fig. 7.23)
Carbon Dioxide Transport
• Hemoglobin also helps transport CO2 and assists in buffering the blood by forming bicarbonate.
• Carbon from respiring cells– Diffuses into the blood plasma and then into
erythrocytes and is ultimately released in the lungs
Figure 42.30
Tissue cell
CO2Interstitialfluid
CO2 producedCO2 transportfrom tissues
CO2
CO2
Blood plasmawithin capillary Capillary
wall
H2O
Redbloodcell
HbCarbonic acidH2CO3
HCO3–
H++Bicarbonate
HCO3–
Hemoglobinpicks up
CO2 and H+
HCO3–
HCO3– H++
H2CO3Hb
Hemoglobinreleases
CO2 and H+
CO2 transportto lungs
H2O
CO2
CO2
CO2
CO2
Alveolar space in lung
2
1
34
5 6
7
8
9
10
11
To lungs
Carbon dioxide produced bybody tissues diffuses into the interstitial fluid and the plasma.
Over 90% of the CO2 diffuses into red blood cells, leaving only 7%in the plasma as dissolved CO2.
Some CO2 is picked up and transported by hemoglobin.
However, most CO2 reacts with water in red blood cells, forming carbonic acid (H2CO3), a reaction catalyzed bycarbonic anhydrase contained. Withinred blood cells.
Carbonic acid dissociates into a biocarbonate ion (HCO3
–) and a hydrogen ion (H+).
Hemoglobin binds most of the H+ from H2CO3 preventing the H+ from acidifying the blood and thuspreventing the Bohr shift.
CO2 diffuses into the alveolarspace, from which it is expelledduring exhalation. The reductionof CO2 concentration in the plasmadrives the breakdown of H2CO3 Into CO2 and water in the red bloodcells (see step 9), a reversal of the reaction that occurs in the tissues (see step 4).
Most of the HCO3– diffuse
into the plasma where it is carried in the bloodstream to the lungs.
In the lungs HCO3– diffuses
from the plasma into red blood cells, combining with H+ released from hemoglobin and forming H2CO3.
Carbonic acid is converted back into CO2 and water.
CO2 formed from H2CO3 is unloadedfrom hemoglobin and diffuses into the interstitial fluid.
1
2
3
4
5
6
7
8
9
10
11
Elite Animal Athletes
• Migratory and diving mammals– Have evolutionary adaptations that allow them to
perform extraordinary feats.– Weddell seals dive to 600 meters repeatedly during
a 20 minute dive and rest and breath for only about 10 minutes. There is no anaerobic metabolism during this dive pattern.
– If a very long dive then they can utilize anaerobic metabolism which provides energy, but then they need to rest for hours to get rid of lactic acid build up.
Adaptations for deep diving
• Stores twice as much oxygen as humans—in greater volume of RBCs (twice as much blood as a human) and myoglobin in the muscles. RBCs also stored in spleen.
• During dive the heart rate slows to 10 beats /min and blood flow is maintained to brain, eyes, spinal cord, adrenal glands and placenta if pregnant
• How does the mother ensure that the fetus gets an adequate supply of oxygen during a dive?
Dissociation curve for Weddell seal blood of fetus and mother.
100
80
60
40
20
0
0 10080
604020
PO2 (mm Hg)
Fetus
Mother
O2
satu
ratio
n of
he
mog
lobi
n (%
)
Fetus hemoglobin has a greater Bohr effect.