Gaseous exchange

1. Circulation and Gas Exchange

2. The Respiratory System
 What is its function? Why is it necessary?
 GETS oxygen for the body
 Needed for cellular respiration
 GETS RID of carbon dioxide
 Produced during cellular respiration
 Characteristics/Requirements of ALL Gas
Exchange Mechanisms:
 MOIST membranes
 High surface area-to-volume ratio
 An animal’s respiratory surfaces must
be large enough to provide oxygen and
expel carbon dioxide for the entire body

3. Respiration in Non-Mammals
 Small animals (earthworms, etc.) exchange
gases by diffusion across its general body
surface
 Gills are outfoldings of the body surface
specialized for gas exchange for aquatic
organisms
 Blood flowing through the capillaries picks up
oxygen from the water

4. Countercurrent Exchange- blood &
water flow in opposite directions

5. Countercurrent Exchange (Aquatic Animals)
 Countercurrent exchange allows for
the efficient transfer of oxygen to
the blood
 As blood flows through the capillary, it
becomes more and more loaded with
oxygen
 Steep concentration gradient allows for
efficient uptake of oxygen

6. Tracheae
 The respiratory
system used by
insects
 Tracheae are air
tubes that branch
throughout the
insect body
 The finest branches
of the tracheae
extend to the
surface of nearly
every cell, where gas
is exchanged by
diffusion

7. Lungs
 Lungs are found in terrestrial vertebrates
 Reptiles, birds, mammals, amphibians
 Lungs of mammals have a large enough
surface area to carry out gas exchange
for the entire body
 How do the gases get from the lungs
throughout the rest of the body, though??
 The circulatory system transports the gases
throughout the body after they’re exchanged in
the lungs

8. Gas Exchange

9. Human Respiratory System

10. Human Respiratory System
 Air enters
the lungs by
a system of
branching
ducts
 Nostrils
 Pharynx
 Larynx
 Trachea (w/
cilia)
 2 bronchi
 Bronchioles
 Alveoli

11. Alveoli
 Alveoli are clusters of air sacs
at the end of bronchioles
 Alveoli have thin epithelium,
which serve as the respiratory
surface
 Oxygen diffuses from the alveoli
into the web of capillaries around
each alveolus
 The capillaries then transfer the
oxygen throughout the body, via
the circulatory system
 ALVEOLI/CAPILLARY DIAGRAM

12. Why is the circulatory system necessary?
 TRANSPORTATION!
 Diffusion is not fast enough to
transport chemicals throughout an
animal’s body
 The circulatory system transports
fluid throughout the body
 This solves the problem of diffusion by
ensuring that no substance had to
diffuse far to enter or leave a cell

13. Open vs. Closed Circulatory Systems
 In open circulatory systems,
hemolymph bathes the internal
organs directly
 Insects, arthropods, mollusks
 In closed circulatory systems, blood
is confined to vessels
 Blood exchanges materials with the ISF
bathing the cells
 Earthworms, squids, octopuses,
vertebrates

14. Open vs. Closed Circulatory Systems

15. Adaptations of the Vertebrate
Circulatory System
 Fish - Heart with 2 chambers (one atrium, one
ventricle)
 Amphibians (frogs)- 3-chambered heart (two atria,
one ventricle)
 Reptiles – (3-chambered with partial septum)
 Birds/Mammals-4-chambered heart (two atria, two
ventricles)

16. FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS
Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries
Lung capillaries Lung capillaries
Lung and skin capillaries
Gill capillaries
Right Left Right Left Right Left
Systemic
circuit
Systemic
circuit
Pulmocutaneous
circuit
Pulmonary
circuit
Pulmonary
circuit
Systemic
circulation
Vein
Atrium (A)
Heart:
ventricle (V)
Artery
Gill
circulation
A
V V
V V
V
A A A
A
A
Left
Systemic
aorta
Right
systemic
aorta
 Vertebrate circulatory systems

17. Double Pump
 Right side pumps to the lungs and
back to left atrium (PULMONARY
CIRCUIT)
 Left side pumps to the entire body
and returns blood to right atrium
(SYSTEMIC CIRCUIT)
 Oxygenated & deoxygenated blood
never mix!

18.  The mammalian cardiovascular system
Pulmonary
vein
Right atrium
Right ventricle
Posterior
vena cava Capillaries of
abdominal organs
and hind limbs
Aorta
Left ventricle
Left atrium
Pulmonary
vein
Pulmonary
artery
Capillaries
of left lung
Capillaries of
head and
forelimbs
Anterior
vena cava
Pulmonary
artery
Capillaries
of right lung
Aorta
Figure 42.5
1
10
11
5
4
6
2
9
3
3
7
8

19. The Heart
 About the size of a
clenched fist
 Made up of mostly
cardiac muscle
tissue: striated with
branches;
involuntary
 Atria have thin
walls, ventricles
have thicker walls
 Why??
 Ventricles must
pump blood through
the pulmonary &
systemic circuits.
(LONG DISTANCE)

20. The Human Heart

21. Blood Vessels
 Arteries carry blood away from the heart to
organs throughout the body
 Arteries are thicker than veins…why??
 Thick layer of smooth muscle (nonstriated;
involuntary)+ elastic tissue
 Veins return blood to the heart
 Categorized by direction of flow, NOT
whether or not they contain oxygen
 Thinner layer of smooth muscle; VALVES to
prevent back flow of blood; not very elastic
 Capillaries are microscopic vessels with very
thin, porous walls

22. .9
Artery Vein
100 µm
Artery Vein
Arteriole
Venule
Connective
tissue
Smooth
muscle
Endothelium
Connective
tissue
Smooth
muscle
Endothelium
Valve
Endothelium
Basement
membrane
Capillary

23. Venous Transport
 In the thinner-walled veins
 Blood flows back to the heart mainly
as a result of muscle action
Direction of blood flow
in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)

24. Capillary Exchange
 The capillary wall is a single layer of
flattened cells
 The transfer of substances occurs
between the capillaries and the
interstitial fluid (which bathes the
cells)
 This occurs by bulk flow, the movement
of fluid due to pressure
 Water, sugars, salts, oxygen, and urea
pass through the capillary walls

25. Capillary Exchange

26. Velocity, B. Pressure, & Area
 The velocity of
blood flow varies
in the circulatory
system
 And is slowest in the
capillary beds as a
result of the high
resistance and large
total cross-sectional
area
e 42.11
5,000
4,000
3,000
2,000
1,000
0 Aorta
Arteries
Arterioles
Capillaries
Venules
Veins
Venae
cavae
Pressure
(mm
Hg)
Velocity
(cm/sec)
Area
(cm
2
)
Systolic
pressure
Diastolic
pressure
50
40
30
20
10
0
120
100
80
60
40
20
0

27. Blood Pressure
 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
 Measured with sphygmomanometer
 Normal pressure = 120/80 mm Hg

28. Control of the Heart
 Cardiac muscles contract (systole)
and relax (diastole) in a rhythmic
cycle
 The sinoatrial node (SA node), also
known as the pacemaker,
maintains the heart’s pumping
rhythm by setting the rate at which
all cardiac muscles contract

29. Control of the Heart

30. The Structure of Blood
 Blood is made up of plasma, red blood cells, white blood
cells, and platelets
 Plasma, which makes up about 55% of blood volume, is
mostly water
 Plasma also contains antibodies
 Plasma also contains fibrinogens, proteins that act as
clotting factors
 Fibrinogen (inactive) is a protein in blood that is
converted into fibrin (active), when needed
 Thrombin is the enzyme that activates the
fibrinogen. K & Ca are important minerals for
clotting reaction to occur.
 Hemophilia is an inherited disorder, characterized by
excessive bleeding from minor cuts and bruises
 People with hemophilia can die from minor cuts

31. The Structure of Blood
 Red Blood Cells (Erythrocytes)
 The human body contains 25 trillion
red blood cells
 Major function is to transport oxygen
 Contains hemoglobin, an iron-
containing protein that carries oxygen
 Red blood cells are produced in the
bone marrow

32. Hemoglobin Carries Oxygen
 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
O2
Figure 42.28

33. Carbon Dioxide Transport
 Small amount binds to hemoglobin
to form carboxyhemoglobin.
 MOST is transported as bicarbonate
ion:
 CO2 + H2O H2CO3H+ + HCO3
-
 Serves as a buffer to control pH of blood.
 pH = 7.4

34. The Structure of Blood
 White blood cells (leukocytes)
 Major function is to fight infection
 5 major types
 Monocytes, neutrophils, basophils,
eosinophils, lymphocytes
 White blood cells spend most of their
time patrolling through the ISF and the
lymphatic system, where most of the
battles against pathogens are waged

35. The Structure of Blood
 Platelets (Thrombocytes)
 Platelets are fragments of cells
 Platelets enter the blood and function
in the process of blood clotting

36. Blood: An Overview

37. Cardiovascular Disease
 Cardiovascular disease (diseases of the
heart and blood vessels) cause more than
half of all deaths in the US
 Heart attack:
 Death of cardiac muscle tissue as a result of
blockage of a coronary artery
 Stroke:
 Death of nervous tissue in the brain, resulting
from blockage of arteries in the head

38. Artherosclerosis
 Plaque (cholesterol and
triglycerides/fats) deposit in blood
vessels
 Can lead to stroke or heart attack.