The circulatory system transports nutrients, gases, wastes, antibodies, hormones and enzymes throughout the body. Invertebrates use diffusion, gastrovascular cavities or open circulatory systems. Vertebrates have closed circulatory systems with hearts and blood vessels. Fish have single circulation hearts while amphibians, reptiles, birds and mammals have increasingly divided multi-chambered hearts to separate oxygenated and deoxygenated blood.

2. 1. Functions of a c. Reptiles
transport/circulatory d. Birds
system
e. Mammals
2. Invertebrate circulation
1) Pathway of blood
a. Diffusion
2) Cardiac cycle
b. Aided by gastrovascular cavity
c. Water vascular system 3) Maintenance of heartbeat
d. Open circulatory system 4) Principles governing blood
circulation
e. Closed circulatory system
5) Lymphatic system
3. Vertebrate circulation 6) Blood composition and
a. Fishes function
b. Amphibians 7) Cardiovascular disease

3.  Transports materials
 Nutrients from digested food
 Respiratory gases: CO2 and O2
 Waste materials: toxins and nitrogenous wastes
 Antibodies
 Hormones
 Enzymes
 Immune functions
 Maintains homeostasis
 Blood pH
 Heat transport

5. Gastrovascular cavity in
simple invertebrates
 Cnidarians (e.g. Hydra)
and flatworms (e.g.
planarians)
 No system required
 Single opening: exchange
of materials with the
environment
 Central cavity for
digestion and
distribution of
substances throughout
the body
 Body walls two cell
layers thick  materials
undergo diffusion

6. Water vascular system in
echinoderms
 multi-purpose:
locomotion, food and
waste
transport, respiration
 movement of muscles
pump water into canals
 closed system of canals
connecting tube feet
 madreporite  ring
canal  radial and
lateral canal  tube feet
 ampullae

7. Open circulatory system
 Phylum
Arthropoda, Phylum
Mollusca (with one
exception)
 hemolymph
 heart(s)  sinuses 
ostia  heart(s)
 diffusion from sinuses to
organs
 often serve a support
purpose
 disadvantage: loss of
pressure in sinuses
 insects: well-developed
respiratory systems, O2
not transported through
the blood

8. Closed circulatory system
or cardiovascular system
 cephalopods, annelids, vertebr
ates
 presence of blood vessels
 advantages
1. rapid flow
2. may direct blood to
specific tissues
3. blood cells and large
molecules remain within
vessels
4. can support higher levels
of metabolic activity

9.  Heart
 Atrium
 Ventricle
 Blood vessels
 Arteries
 Arterioles
 Capillaries and
capillary beds
 Venules
 Veins
 Blood

10. FISHES
 Single-circulation
 Fish heart
 2-chambered
 atrium and ventricle
 African lungfish heart
 3-chambered
 2 atria
 LA: O2-rich blood
 RA: O2-poor blood
 spiral fold
 partially divided
ventricle

11. Amphibians
 Pulmocutaneous and
systemic circulation are
partly separated
 Amphibian heart
 1 ventricle
 2 atria:
 LA: O2-rich blood
 RA: O2-poor blood
 advantage: oxygen-rich
blood reaches the
body’s organs faster
 disadvantage: some
mixing of O2-rich and
poor blood occurs

12. Reptiles
 Reptilian heart
 3-chambers
(crocodilians have 4)
 2 atria
 1 ventricle (2 in
crocodiles and
alligators)
 partially
divided, decreases
mixing

13. Birds and Mammals
 4 chambered heart:
 2 atria
 2 ventricles
 full separation of
pulmonary and systemic
circuits
 Advantages
1. no mixing of oxygenated and
deoxygenated blood
2. gas exchange is maximized
3. pulmonary and systemic circuits
operate at different pressures
 Importance
1. Endothermic  high nutrient and
O2 demands in tissues
2. Numerous vessels  great deal of
resistance, so requires high
pressure

14.  R side of heart:
 pulmonary circuit
 L side of heart:
 systemic circuit
 one way valves:
 atrioventricular
valves
 semilunar valves

15. 1. right atrium receives O2-
poor blood from superior
and inferior venae cavae
2. from right atrium into the
right ventricle through the
tricuspid valve
3. pumped into the
pulmonary artery through
the pulmonary semilunar
valve to lungs
4. O2-rich blood from lungs is
returned to the left atrium
via the pulmonary veins
5. enters the left ventricle via
the mitral or bicuspid valve
6. exits the left ventricle into
the aorta via the aortic
semilunar valve
7. circulated to body tissues