Brief lesson on mammalian (mostly) circulatory system

1. CHAPTER 42: CIRCULATION &CHAPTER 42: CIRCULATION &
GAS EXCHANGEGAS EXCHANGE

2. What’s the function of a circulatory
system?
• A circulatory system facilitates the exchange
of gases like O2 & CO2, the absorption of
nutrients, and the disposal of wastes between
cells and the environment

3. Invertebrate Circulation
• Some inverts have gastrovascular cavities (GVC), which are not
true circulatory systems
– The cavity is used for both digestion & circulation
– These animals have a 2-cell thick body wall separating the
inside of the animal from the outside
• The inner layer of cells have direct contact with the GVC.
The outer layer of cells exchange nutrients & waste via
diffusion

4. Invertebrate Circulation
Open Vs. Closed circulatory systems
OPEN CLOSED
*Blood
aka circ-
ulatory
fluid
*Vessels
aka tubes
*Heart
aka pump
Blood directly bathes
organs
Blood is mixed with lymph
=hemolymph
One or more hearts pump
fluid into sinuses
EX: arthropods
Blood is in vessels
Blood & lymph are separate
One or more hearts
pump fluid through
smaller vessels which
exchange materials
w/cells
EX: All verts, octopi, &
earthworms

5. The Basics of Mammalian Circulation
Mammals have a cardiovascular
system that’s a double pathway
– The pulmonary circuit cycles
blood between the heart and the
lungs for gas exchange between
blood & lungs
– The systemic circuit delivers
oxygen rich blood throughout the
body in exchange for CO2 waste
which is delivered back to the
lungs for disposal (exhalation)
*Red=oxygenated
Blue =deoxygenated blood
ANIMATION:
http://wps.aw.com/bc_campbell_biology_7/26/6669/1707335.cw/index.html

6. The Mammalian Heart
• The heart pumps in rhythmic cycles of contractions
& relaxation
– When the heart contracts, it’s called systole
– When it relaxes & fills with blood, it’s called diastole
Valves between cavities shut
to prevent the backflow of
blood. Ex: Atrioventricular
valve & semilunar valves
ANIMATION:
http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html

7. Mammalian Heart: Maintaining a Rhythm
• The cardiac muscles of the heart need to be coordinated in order
for the heart to function properly
– The sinoatrial (SA) node is the heart’s pacemaker.
• Electrical impulses are generated at the SA node and then
spread from cell to cell throughout the heart
• There’s a delay at the AV node to allow the atria to empty
completely before the ventricles contract
ANIMATION
http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_electrical.html

8. The Structure of Blood Vessels
• Arteries carry O2-
rich blood away
from the heart
– Capillaries are
small branches that
carry blood to &
from tissues
• Veins carry O2-
deficient blood
back

9. Blood Pressure
• Stroke volume is the amount of blood pumped out
the left ventricle during each contraction
• Blood pressure is the pressure that the flowing
blood exerts on the walls of the blood vessels
http://www.healthcentral.com/high-blood-pressure/introduction-47-115.html

10. Blood is a Connective Tissue with Cells Suspended in
Plasma
• The liquid part of blood = plasma
– Plasma is 90% water
– Human plasma pH is maintained at 7.4
– Plasma carries nutrients, wastes, proteins such as fibrinogen
which aid in blood clotting, and a variety of blood cells
RBCs are the most numerous of the cell
types. They are made of the iron-
containing protein, hemoglobin, which has
a high affinity for O2

11. Gas Exchange
• Gas exchange (not to be confused with cellular
respiration) is the intake of O2 from the environment
and the discharge of CO2 into the environment
– This exchange between the inside of the organism and
the environment is vital for cellular respiration (the
production of ATP)

12. The Role of Pressure Gradients in Gas
Exchange
• Gases diffuse from regions of high pressure to low pressure
• PO2
=the partial pressure
of oxygen
• PCO2
= the partial pressure
of carbon dioxide
In lungs
In tissue

13. Gas Exchange
Red blood cells are used to transport oxygen
– RBCs contain hemoglobin
– Hemoglobin has 4 subunits, each with its own iron which can bind to
an oxygen molecule
• Therefore, 1 hemoglobin molecule can carry 4 oxygen molecules
• Hemoglobin must be able to bind & unbind to oxygen
• When 1 O2 binds to hemoglobin, the shape changes to increase its
affinity for binding to more O2. When 1 O2is unloaded, the shape
of the hemoglobin molecule is changed to facilitate the unloading
of the other 3 O2

14. Gas Exchange
Hemoglobin of RBCs carry oxygen & release it to cells as needed
– The Bohr Shift-when cells are releasing lots of CO2 (such as
during exercise), the CO2 combines with water in the plasma and
forms carbonic acid. Because plasma is mostly water, CO2is
commonly carried in the plasma in the form of carbonic acid
• This decrease in pH changes the shape of hemoglobin protein
& causes it to have less of an affinity for O2, which can then be
used for cell respiration

15. Gas Exchange in Aquatic Animals
• Gills are outfoldings of the body surface that are in contact with the
water.
– They are the organs used for gas exchange in aquatic animals &
worms
– Many organisms with gills have appendages that help ventilate
the gills by propelling water over them. A fish open & closes its
mouth to pump water over the gills. This prevents the
accumulation of O2-deficient water around the gills

16. Gas Exchange in Aquatic Animals
• The efficiency of gas exchange is increased by countercurrent
exchange in the gills
– Water in the environment and blood in the capillaries flow in
opposite directions
– This maintains an O2 concentration gradient that favors the
diffusion of O2 from the water into the capillaries of the gills

17. Gas Exchange in Insects
• Insects have a tracheal system made of tubes
– Air enters the insect through holes, called spiracles, on the
surface of the insect’s body
– The air then travels through tracheae, which can either
branch into smaller tubes (tracheoles) or air sacs
– Gases can then diffuse into/out of the cells

18. Gas Exchange in Mammals
• Air enters through the nostrils where it is filtered & warmed
• Air flows through the larynx & into the trachea which branches
into bronchi leading into each lung
• Bronchi branch into smaller tubes= bronchioles
which then form clusters of alveoli at their tips
• Aveoli are the sites of
gas exchange

19. How a Mammal Breathes
• When the diaphragm & rib cage muscles contract, they open up
the abdominal cavity.
– This creates a negative pressure in the lungs and air rushes in
• When the diaphragm & rib muscles relax, they create a smaller
space in the abdominal cavity & force air out
ANIMATION:
http://teachhealthk-12.uthscsa.edu/studentresources/AnatomyofBreathing3.swf