1. Circulation and gas transport (continued)IB
3/19/06

2. Blood Clotting A cascade of complex reactions
Converts fibrinogen to fibrin, forming a clot
Platelet plug
Collagen fibers
Platelet releases chemicals that make nearby platelets sticky
Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K)
Prothrombin
Thrombin
Fibrinogen
Fibrin
5 µm
Fibrin clot
Red blood cell
The clotting process begins when the endothelium of a vessel is damaged, exposing connective tissue in the vessel wall to blood. Platelets
adhere to collagen fibers in
the connective tissue and release a substance that
makes nearby platelets sticky. 1
The platelets form a plug that provides
emergency protection
against blood loss. 2
This seal is reinforced by a clot of fibrin when vessel damage is severe. Fibrin is formed via a multistep process: Clotting factors released from the clumped platelets or damaged cells mix with clotting factors in the plasma, forming an activation cascade that converts a plasma protein called 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

3. 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

4. (b) Partly clogged artery
One type of cardiovascular disease, atherosclerosis
Is caused by the buildup of cholesterol within arteries (low density lipoprotein complexes with cholesterol)
Plaques sites of inflammation and can cause a clot to form if plaque splits open! Aspirin!
Figure 42.18a, b
(a) Normal artery
(b) Partly clogged artery
50 µm
250 µm
Smooth muscle
Connective tissue
Endothelium
Plaque
Thrombus!

5. 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).

6. Concept 42.5: Gas exchange occurs across specialized respiratory surfaces
Supplies oxygen for cellular respiration and disposes of carbon dioxide
Figure 42.19
Organismal level
Cellular level
Circulatory system
Cellular respiration
ATP
Energy-rich molecules from food
Respiratory surface
Respiratory medium (air of water) O2
CO2
Oxygen is final electron acceptor in electron transport chain!!

7. 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

8. 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 gill is an extension of the coelom (body cavity). Gas exchange occurs by diffusion across the gill surfaces, and fluid in the coelom circulates in and out of the 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

9. 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 gills and also function in crawling and swimming.
Parapodia
Gill

10. 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 crustaceans have long, feathery gills covered by the exoskeleton. Specialized body appendages drive water over the gill surfaces.
(c) Scallop. The gills of a scallop are long,
flattened plates that project from the
main body mass inside the hard shell.
Cilia on the gills circulate water around the gill surfaces.
Gills

11. 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
Gill filaments
Oxygen-poor blood
Oxygen-rich blood
Water flow over lamellae showing % O2
Blood flow through capillaries in lamellae showing % O2
Lamella
100%
40%
70%
15%
90%
60%
30% 5% O2
Ram jet ventilation!

12. Tracheal Systems in Insects
The tracheal system of insects
Consists of tiny branching tubes that penetrate the body
Figure 42.22a
Tracheae
Air sacs
Spiracle
(a) The respiratory system of an insect consists of branched internal tubes that deliver air directly to body cells. Rings of chitin reinforce the 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 of the fluid is withdrawn into the body. This increases the surface area of air in contact with cells.

13. The tracheal tubes Supply O2 directly to body cells Figure 42.22b
Air sac
Body cell
Trachea
Tracheole
Tracheoles
Mitochondria
Myofibrils
Body wall
(b) This micrograph shows cross sections of tracheoles in a tiny piece of insect flight muscle (TEM). Each of the numerous mitochondria in the muscle cells lies within about 5 µm of a tracheole.
Figure 42.22b
2.5 µm
Air

14. Lungs
Spiders, land snails, and most terrestrial vertebrates have internal lungs.

15. 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 the pulmonary artery (oxygen-poor blood)
Alveoli
Colorized SEM
SEM
50 µm
Heart
Left lung
Nasal cavity
Pharynx
Larynx
Diaphragm
Bronchiole
Bronchus
Right lung
Trachea
Esophagus
Figure 42.23
Capillary web over alveoli

16. 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!

17. 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

18. How a Mammal Breathes Mammals ventilate their lungs
By negative pressure breathing, which pulls air into the lungs
Air inhaled
Air exhaled
INHALATION Diaphragm contracts (moves down)
EXHALATION Diaphragm relaxes (moves up)
Diaphragm
Lung
Rib cage expands as rib muscles contract
Rib cage gets smaller as rib muscles relax
Figure 42.24

19. 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
INHALATION Air sacs fill
EXHALATION Air sacs empty; lungs fill
Anterior air sacs
Trachea
Lungs
Posterior air sacs
Air
1 mm
Air tubes (parabronchi) in lung
Figure 42.25

20. Air passes through the lungs Every exhalation
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!)

21. 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
Pons
Breathing control centers
Medulla oblongata
Diaphragm
Carotid arteries
Aorta
Cerebrospinal fluid
Rib muscles
In a person at rest, these nerve impulses result in about 10 to 14 inhalations per minute. Between inhalations, the muscles relax 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 aorta and carotid arteries in the neck detect changes in blood pH and send nerve impulses to the medulla. In response, the medulla’s breathing control center alters the rate and depth of breathing, increasing both to dispose of excess CO2 or decreasing both if CO2 levels are depressed.
The control center in the
medulla sets the basic rhythm, and a control center in the pons moderates it, smoothing out the transitions between
inhalations and exhalations. 1
Nerve impulses trigger muscle contraction. Nerves from a breathing control center in the medulla oblongata of the brain send impulses to the diaphragm and rib muscles, stimulating them to contract and causing inhalation. 2
The sensors in the aorta and carotid arteries also detect changes in O2 levels in the blood and signal the medulla to increase the breathing rate when levels become very low. 6 5 4 3

22. 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

23. 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).

24. 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.

25. 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.

26. 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

27. In the lungs and in the tissues
O2 and CO2 diffuse from where their partial pressures are higher to where they are lower

28. Exhaled air contains a lot of oxygen because of mixing in dead end space!
Inhaled air
Exhaled air
160
0.2 O2
CO2
Alveolar epithelial cells
Pulmonary arteries
Blood entering alveolar capillaries
Blood leaving tissue capillaries
Blood entering tissue capillaries
Blood leaving alveolar capillaries
Tissue capillaries
Heart
Alveolar capillaries of lung
<40 >45
Tissue
cells
Pulmonary veins
Systemic arteries
Systemic veins
Alveolar spaces 2 1
0.5 liter tidal volume
4.8 l vital capacity
1.2 l residual space 3 4
Figure 42.27

29. 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)

30. 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).

31. 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 loaded
in lungs
O2 unloaded
In tissues
Polypeptide chain O2
Figure 42.28

32. 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

33. Cooperative O2 binding and release
Is evident in the dissociation curve for hemoglobin
A drop in pH
Lowers the affinity of hemoglobin for O2

34. (b) pH and Hemoglobin Dissociation
O2 unloaded from
hemoglobin
during normal
metabolism
O2 reserve that can
be unloaded from
hemoglobin to
tissues with high
Tissues during
exercise
Tissues
at rest
100 80 60 40 20
Lungs
PO2 (mm Hg)
O2 saturation of hemoglobin (%)
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

35. Arterial Blood O2 saturation and O2 content20
100 O 80 2
Content 15
Arterial
(vol. %)
(= mL O2
per 100mL
blood)
blood 60
% O2
saturation 10 40 5 20 30 60 90
PO2 (mm Hg)

37. Carbon Dioxide Transport
Hemoglobin also helps transport CO2 and assists in buffering the blood by forming bicarbonate.

38. Carbon from respiring cells
Diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs

39. Figure 42.30
Tissue cell
CO2
Interstitial fluid
CO2 produced
CO2 transport from tissues
Blood plasma within capillary
Capillary wall
H2O
Red blood cell Hb
Carbonic acid
H2CO3
HCO3– H+ +
Bicarbonate
Hemoglobin picks up CO2 and H+
Hemoglobin releases CO2 and H+
CO2 transport to lungs
Alveolar space in lung 2 1 3 4 5 6 7 8 9 10 11
To lungs
Carbon dioxide produced by body 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 by carbonic anhydrase contained. Within red 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 thus preventing the Bohr shift.
CO2 diffuses into the alveolar space, from which it is expelled during exhalation. The reduction of CO2 concentration in the plasma drives the breakdown of H2CO3
Into CO2 and water in the red blood cells (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 unloaded from hemoglobin and diffuses into the interstitial fluid.

40. 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.

41. Weddell seal

42. 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?

43. Dissociation curve for Weddell seal blood of fetus and mother.
100 80 60 40 20
PO2 (mm Hg)
Fetus
Mother
O2 saturation of hemoglobin (%)
Fetus hemoglobin has a greater Bohr effect.

44. The Ultimate Endurance Runner
The extreme O2 consumption of the antelope-like pronghorn underlies its ability to run at high speed (60km/hr) over long distances. Greater lung surface, higher cardiac output and more mitochrondia per unit muscle.
Figure 42.31