circulatory-system-of-the-vertebrates.

1. Circulatory System of the
Vertebrates

2.  Multicellular animals do not have most of their cells in
contact with the external environment and so have
developed circulatory systems to transport nutrients,
oxygen, carbon dioxide and metabolic wastes.
Components of the circulatory system include
a.blood: a connective tissue of liquid plasma and
cells
b. heart: a muscular pump to move the blood
c.blood vessels: arteries, capillaries and veins that
deliver blood to all tissues

3. There are several types of circulatory
systems.
1. open circulatory system = (evolved in
insects, mollusks and other invertebrates)
= pump blood into a hemocoel with the
blood diffusing back to the circulatory system
between cells. Blood is pumped by a heart
into the body cavities, where tissues are
surrounded by the blood.
= The resulting blood flow is sluggish.

4.  Circulatory systems of an insect (top) and mollusc (middle). Images
from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer
Associates (www.sinauer.com) and WH Freeman (
www.whfreeman.com), used with permission.

5. 2. closed circulatory system = have the blood closed at
all times within vessels of different size and wall
thickness. In this type of system, blood is pumped by
a heart through vessels, and does not normally fill
body cavities.
= Blood flow is not sluggish.
= Hemoglobin causes vertebrate blood to turn red
in the presence of oxygen;
= but more importantly hemoglobin molecules in
blood cells transport oxygen.
= The human closed circulatory system is
sometimes called the cardiovascular system.
= A secondary circulatory system, the
lymphatic circulation, collects fluid and cells and
returns them to the cardiovascular system.

6. Vertebrate Circulatory Systems:
 transport gases, nutrients, waste
products, hormones, heat, &
various other materials
consist of heart, arteries,
capillaries, & veins

Arteries
= carry blood away from the heart
= have muscular, elastic walls
= terminate in capillary beds

7.  Capillaries
= have very thin walls (endothelium only)
= are the site of exchange between the blood
and body cells

8.  Veins
= carry blood back
to the heart
= have less muscle
in their walls than
arteries but the
walls are very
elastic
= begin at the end
of capillary beds

9.  Heart
= a muscular pump
(cardiac muscle)
= contains a
pacemaker to
regulate rate but
rate can also be
influenced by the
Autonomic
Nervous System

10. Hagfish
 open blood vessels,
The heart has two chambers separated by a
cartilaginous rod. When muscles contract to bend
this rod, the volume of each chamber changes; one
side expanding to draw in blood and the other
contracting to expel blood.
Valves prevent backflow of blood.



11. Cartilaginous fishes
 single-circuit heart with 4 chambers: sinus
venosus, atrium, ventricle, & conus
arteriosus



 the sinus venosus receives blood & is filled by
suction when the ventricle contracts & enlarges the
pericardial cavity
the atrium is a thin-walled muscular sac; an A-V
valve regulates flow between atrium & ventricle
the ventricle has thick, muscular walls
the conus arteriosus leads into the ventral aorta
(and a series of conal valves in the conus
arteriosus prevent the backflow of blood)

13. Teleosts
 heart is similar to that of cartilaginous fishes,
except a bulbus arteriosus (a muscular
extension of the ventral aorta) is present
rather than a conus arteriosus (a muscular
extension of the ventricle)
 which is probably why most of them are
"cold-blooded".

15.  Blood collected from throughout the fish's
body enters a thin-walled receiving chamber,
the atrium.
 As the heart relaxes, the blood passes
through a valve into the thick-walled,
muscular ventricle.
Contraction of the ventricle forces the
blood into the capillary networks of the
gills where gas exchange occurs.
The blood then passes on to the capillary
networks that supply the rest of the body
where exchanges with the tissues occur.
Then the blood returns to the atrium.




16.  Lungfish & amphibians
- modifications are
correlated with the
presence of lungs &
enable oxygenated blood
returning from the lungs
to be separated from
deoxygenated blood
returning from elsewhere

17.  Partial or complete
partition within atrium
(complete in anurans
and some urodeles)
 Partial interventricular
septum (lungfish) or
ventricular trabeculae
(amphibians) to
maintain separation of
oxygenated &
unoxygenated blood

18.  Formation of a
spiral valve in the conus
arteriosus of many
dipnoans and amphibians.
The spiral valve alternately
blocks & unblocks the
entrances to the left and
right pulmonary arches
(sending unoxygenated
blood to the skin & lungs).
 Shortening of ventral aorta,
which helps ensure that the
oxygenated &
unoxygenated block kept
separate in the heart
moves directly into the
appropriate vessels

19. The Frog Heart
 The frog heart has 3 chambers: two atria
and a single ventricle.
 The atrium receives deoxygenated blood
from the blood vessels (veins) that drain the
various organs of the body.
 The left atrium receives oxygenated blood
from the lungs and skin (which also serves as
a gas exchange organ in most amphibians).
 Both atria empty into the single ventricle.

21.  While this might appear to waste the
opportunity to keep oxygenated and
deoxygenated bloods separate, the ventricle
is divided into narrow chambers that reduce
the mixing of the two blood.
 So when the ventricle contracts,
 oxygenated blood from the left atrium is sent,
relatively pure, into the carotid arteries
taking blood to the head (and brain);

23.  deoxygenated blood from the
right atrium is sent, relatively
pure, to the
pulmocutaneous arteries
taking blood to the skin and
lungs where fresh oxygen
can be picked up.
Only the blood passing into
the aortic arches has been
thoroughly mixed, but even
so it contains enough oxygen
to supply the needs of the
rest of the body.


24. The Lizard Heart
Lizards have a muscular septum which
partially divides the ventricle.
 When the ventricle contracts, the opening in
the septum closes and the ventricle is
momentarily divided into two separate
chambers.
 This prevents mixing of the two bloods.

 The left half of the ventricle pumps oxygenated
blood (received from the left atrium) to the body.
The right half pumps deoxygenated blood (received
from the right atrium) to the lungs.

26. Amniotes:
1. Heart consists of 2 atria & 2 ventricles &, except in
adult birds & mammals, a sinus venosus
2 - Complete interatrial septum
3 - Complete interventricular septum only in
crocodilians, birds, & mammals; partial septum in
other amniotes

27. Four Chambers: Birds and Mammals
 The septum is complete in the hearts of birds
and mammals providing two separate
circulatory systems:
 pulmonary for gas exchange with the
environment and
 systemic for gas exchange (and all other
exchange needs) of the rest of the body.

28.  Arterial channels - supply most tissues
with oxygenated blood (but carry
deoxygenated blood to respiratory organs).
In the basic pattern:
1 - the ventral aorta emerges from heart &
passes forward beneath the pharynx
2 - the dorsal aorta (paired above the
pharynx) passes caudally above the
digestive tract
3 - six pairs of aortic arches connect the
ventral aorta with the dorsal aortas

29. Aortic arches of fishes -
general pattern of development of arches in cartilagi
:
1 - Ventral aorta extends forward below pharynx &
connects developing aortic arches. The first pair of
arches develop first.
2 - Segments of first pair are lost & remaining
sections become efferent pseudobranchial arteries
3 - Other pairs of arches (2 - 6) give rise to pre- &
posttrematic arteries
4 - Arches 2 - 6 become occluded; dorsal
segments = efferent branchial arteries & ventral
segments = afferent branchial arteries
5 - Capillary beds develop within nine
demibranchs

31.  Teleosts:
 the same changes convert
6 pairs of embryonic aortic
arches into afferent &
efferent branchial arteries
arches 1 & 2 are usually los


32.  Lungfish:
 the pulmonary
artery branches off
the 6th aortic arch
and supplies the
swim bladder (&
this is the same
way that tetrapod
lungs are
supplied)

33.  Aortic arches of tetrapods - embryos
have 6 pairs of aortic arches:




 but the 1st & 2nd arches are temporary
& not found in adults
the 3rd aortic arches & the paired dorsal
aortas anterior to arch 3 are called the
internal carotid arteries
the 4th aortic arches are called the
systemic arches
the 5th aortic arch is usually lost
the pulmonary arteries branch off the 6th
arches & supply blood to the lungs

36.  Birds & mammals - no mixing of
oxygenated & unoxygenated blood; complete
interventricular septum + division of ventral
aorta into 2 trunks:
 Pulmonary trunk that takes blood to the lungs
 Aortic trunk that takes blood to the rest of the
body
 Result of modifications: All blood returning
to right side of heart goes to the lungs; blood
returning from lungs to the left side of heart
goes to systemic circulation.