Transcript circulation and gas exchange

CIRCULATION AND GAS
EXCHANGE
CHAPTER 42
CIRCULATION
Figure 42.1 Internal transport in the cnidarian Aurelia
SOME TERMS
• Open circulatory system – blood bathes
internal organs directly
• Closed circulatory system – blood is
confined to vessels and is distinct from
interstitial fluid
• Atrium (atria) – chambers of heart that
receive blood
• Ventricle - chambers of heart that pump
blood out of heart
Figure 42.2 Open and closed circulatory systems
• Arteries – carry blood away
from heart
• Arterioles (small arteries)
• Capillaries – microscopic
vessels where gas and
chemical exchanges takes
place
• Venules (small veins)
• Veins – carry blood to heart
• Pulmocutaneous circuit – leads
to gas exchange in tissues
• Systemic circuit – carries oxygen
rich blood to body and oxygen
poor blood to right atrium
• Double circulation – when blood
is pumped a second time after it
loses pressure in capillaries
Figure 42.3 Generalized circulatory schemes of vertebrates
MAMMALIAN HEART
• Atrioventricular valve – valves
between each atrium and
ventricle; prevent back-flow
• Semilunar valves – valves at
two exits of heart (at pulmonary
artery and aorta)
• Heart rate – number of
heartbeats per minute
(measured by taking pulse)
Figure 42.4 The mammalian cardiovascular system
Animations
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Just heart pumping
Basic circulation
Breathing
http://www.smm.org/heart/lessons/lesso
n5.htm
Figure 42.5 The mammalian heart: a closer look
CARDIAC CYCLE
• One complete cycle of pumping
and filling
–Systole – contraction phase
–Diastole – relaxation phase
• Blood pressure is systole over
diastole (For example: 110/80)
Figure 42.6 The cardiac cycle
HEART BEAT
• Sinoatrial (SA) node or
pacemaker – maintains heart beat by
setting rhythm at which all cardiac cells
contract
– Located in wall of right atria
– Generates nerve pulses
– First pulse contracts atria together
– SA node controlled by two nerves,
hormones (ex. Epinephrine), body
temp, exercise
• Hits atrioventricular (AV)
node
–In wall between right atrium
and right ventricle
–Pulse contracts both
ventricles about 0.1 seconds
behind atria’s contractions
• Electrocardiogram (ECG OR
EKG) – currents recorded
Figure 42.7 The control of heart rhythm
STRUCTURE OF VESSELS
• Veins have flaps to prevent
back flow
• Arteries have thicker layers
than veins in order to handle
the higher pressure
• Capillaries thinnest and lack
outer two walls
Figure 42.8 The structure of blood vessels
BLOOD FLOW
• Blood moves fastest in arteries
and slowest in capillaries
–Total diameter of capillaries is
greater than arteries so blood
moves slowest in capillaries
–Speeds up a little in veins
because of a decrease in area
Figure 42.9 Blood flow in veins
Figure 42.12 Blood flow in capillary beds
Figure 42.13 The movement of fluid between capillaries and
the interstitial fluid
BLOOD PRESSURE
• The hydrostatic force that blood
exerts on the wall of a vessel
• Greatest in arteries
–Blood enters arteries faster than
it can leave so arteries stretch
–Heart contracts and send more
blood into arteries before artery
is completely relaxed
–This means there is always at least
some pressure in arteries caused by
the impedance of the arterioles =
peripheral resistance
–Smooth muscles relax, blood flow
increases and pressure decreases
–Almost no pressure in capillaries
–Veins use flaps, smooth muscle
contractions and skeletal muscles
Figure 42.11 Measurement of blood pressure
Figure 42.10 The interrelationship of blood flow velocity, crosssectional area of blood vessels, and blood pressure
LYMPHATIC SYSTEM
• Lost fluid and proteins from capillaries
returns to heart via lymphatic system
• fluid is then called lymph
• vessels like veins (flaps)
• empties back into blood near venae
cavae and right atrium junction
• lymph nodes filter lymph
–filled with white blood cells
BLOOD
• Plasma - liquid matrix; 90%
water; also includes ions,
proteins, gases, and nutrients
• Erythrocytes (red)
–lack nuclei in mammals
–lack mitochondria
–hemoglobin carries oxygen
Figure 42.14 The composition of mammalian blood
Figure 42.14x Blood smear
• Leukocytes (white)
–fight disease
–monocytes, neutrophils,
basophils, esinophils,
lymphocytes
• Platelets
–fragments
–aid in blood clotting
CELL DIFFERENTIATION
• Pluripotent cells in red bone
marrow develop into white and
red cells
• Erythropoietin - stimulates
production of red blood cells if
low oxygen in tissues
Figure 42.15 Differentiation of blood cells
BLOOD CLOTTING
• Inactive fibrinogen is activated
by clotting factors from platelets
to make fibrin
• Fibrin forms thread-like clot
• Hemophiliac cannot make one
of the clotting factors
Figure 42.16a Blood clotting
Figure 42.16x Blood clot
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CARDIOVASCULAR DISEASE
Heart attack- death of cardiac muscle
tissue resulting from blockage of
coronary arteries (supply oxygen to
heart)
Stroke - death of nervous tissue in
brain, usually resulting from blockage
of arteries in head
Thrombus - blood clot
Embolus - transported clot (to brain
or heart)
• Atherosclerosis - chronic
cardiovascular disease where
plaques develop on inner walls of
arteries
–Arteriosclerosis – when
plaque becomes even more
hardened by calcium deposits
–Common sites of thrombus
formation
–Embolus more likely to get
trapped
Figure 42.17 Atherosclerosis: normal artery and artery with
plaque
• Hypertension – high blood
pressure increases risk of heart
attack and stroke
–Possibly because high blood
pressure damages lining and
promotes plaque formation
• Low density lipoproteins –
deposits cholesterol
• High density lipoproteins –
may reduce cholesterol
deposition
GAS EXCHANGE
Figure 42.18 The role of gas exchange in bioenergetics
Figure 42.19 Diversity in the structure of gills, external body
surfaces functioning in gas exchange
OVERVIEW
• Gas exchange can occur
across cell membranes (in
unicellular organisms), moist
skin, gills, tracheae, and lungs
• All respiratory surfaces must be
moist.
• Gills – outfoldings of body
surface specialized for gas
exchange
–Advantage – cells always
moist
–Disadvantage – lower oxygen
in water than air and
saltier/warmer water has less
oxygen
–Ventilation – increases flow
of water over cells
Figure 42.0 External gills of a salmon
–Countercurrent exchange –
as blood flows through
capillaries it becomes loaded
with more oxygen, but also
encounters water that has
higher oxygen levels
• This allows diffusion of
oxygen into blood for entire
length of capillary
Figure 42.20 The structure and function of fish gills
Figure 42.21 Countercurrent exchange
TRACHEAL SYSTEMS
• In insects, made up of air tubes
throughout body
• Largest tubes (tracheae) open
to outside
–Diffusion
–Larger insects’ body
movements contract tubes
(move air through)
Figure 42.22 Tracheal systems
LUNGS
• Restricted to one location
• Must be connected to
circulatory system
–Frogs supplement lungs with
moist skin
–Turtles supplement lungs with
moist mouth and anus
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MAMMALIAN RESPIRATORY
SYSTEM
Larynx – upper part of trachea
–Vocal cords
Trachea, bronchi, bronchioles, alveoli
(air sacs)
Beating cilia and mucas trap
contaminants
Alveoli (air sacs) – millions of single
cells where gas exchange occurs
between the sacs and the blood
Figure 42.23ab The mammalian respiratory system
Figure 42.23c Alveoli
Figure 42.23cx1 Alveolar structure of mouse lung
Figure 42.23cx2 Alveolar structure of mouse lung
BREATHING
• Positive pressure breathing –
air pushed down trachea
• Negative pressure breathing
– air pulled down trachea
–Diaphragm – skeletal muscle
at bottom of rib cage
Figure 42.24 Negative pressure breathing
• Tidal volume – normal breath volume
• Vital capacity – maximum volume of
air that can be exhaled and inhaled
• Residual volume – air remains in
alveoli even after we exhale
• Birds
–Air sacs that help keep air flowing
through lungs and trim density of
bird
Figure 42.25 The avian respiratory system
CONTROL OF BREATHING
• Medulla oblongata and pons
are two control centers
• Medulla monitors CO2 levels by
monitoring pH level and
increases breathing if CO2
levels are too high
• Carotid arteries monitor O2 and
CO2 levels and report to brain
Figure 42.26 Automatic control of breathing
DIFFUSION OF GASES
• Gas always move from region
of higher partial pressure to
lower pressure
• Partial pressure of oxygen in
atmosphere at sea level is
160 mm Hg
Figure 42.27 Loading and unloading of respiratory gases
Figure 42.28 Oxygen dissociation curves for hemoglobin
OXYGEN TRANSPORT
• Protein pigments with metal
ions that carry oxygen
• Hemocyanin – in many
mollusks and arthropods; has
copper
• Hemoglobin – in most
vertebrates; has Fe; can carry 4
oxygen molecules
• Hemoglobin unloads its oxygen
when the partial pressure of
oxygen surrounding the red
blood cell decreases.
• disassociation curve
• Bohr shift – slight drop in pH
causes hemoglobin to give up
more oxygen
CARBON DIOXIDE
• 7% dissolved in blood
• 23% binds to hemoglobin
• 70% transported in blood as
bicarbonate ions
–Buffers blood – can release
and add H+ as needed
thereby changing pH of blood
Figure 42.29 Carbon dioxide transport in the blood
Figure 42.30 The Weddell seal, Leptonychotes weddelli, a
deep-diving mammal
Dissociation curves for two hemoglobins