Fish Circulatory System
Mohammed Sulaiman
Introduction
• Because fishes live in environment that is
oxygen poor compare to the atmosphere,
their simpler heart must force blood past an
oxygenating surface before its distribution to
the tissue.
• Thus, special adaptations to many situation
have involved the composition of the blood,
and the circulatory apparatus of the fish
Blood of the Fishes
• Fishes generally have less blood volume than
other vertebrates.
• The volume usually ranging between 2 and 4 mg/
100g in bony fishes
• The higher bony fishes possess a more perfected
vascular system , and thus need less blood for
transport of oxygen and other materials
• The blood transports a variety of materials such
as hormones, vitamins, plasma proteins that may
make up from 2-6g/ 100ml
Osmotic Concentration of the blood
• The osmotic conc of the fish blood varies
according to the habitat and means of
osmoregulation developed in the species
involved
• Sodium and chlorine are the main contributors to
the osmotic concentration
• The osmoconcentration of bony fish blood
ranges from somewhat below 200 milliosmoles
(mOsm) in fresh water to more than 400 mOsm
in marine species
Cellular constituent
• Cellular constituent of the blood are the red
blood cells or erythrocytes and the white or
leucocytes
• RBC obtain their characteristic colour from
haemoglobin, which is made up of colourless
protein globulin and the red-yellow pigment
haeme, which contains iron
• Haemoglobin transport oxygen in combination
with ferrous iron of the haeme
Erythrocyte
• The erythrocytes of fishes are nucleated and
usually oval in shape, with relatively few species
having cells with a nearly round shaped.
• Lampreys have round erythrocyte abut 9
micron.
• Elasmobranchs have large erythrocyte , the
length ranging from 20- 27 microns and width
from around 12-14 microns
• Erythrocyte of bony fishes generally range from
12-14 micron in length and 8.5 to 9.5 in diameter
Leukocytes
• The wbc are not as numerous as the rbc.
• The wbc includes the granulocytes, thrombocytes,
lymphocytes and monocytes
• Thrombocytes are involve in blood clotting through
the conversion of prothrombin to thrombin
• Granulocytes include 3 types of cells based on staining
properties, neutrophils, eosinophils and basophils.
Granulocytes are phagocytic
• Lymphocytes include the phagocytic macrophages,
plasma cells and small lymphocytes that are active in
protein production
Leukocytes
• Monocytesare
sometimes
called
macrophages. They phagocytize bacteria and
parasitic larvae in the blood
• Granulocytes, they specially attack bacteria
and are believe to have a role in controlling
stress.
• Non specific cytotoxic cells, these cells
attacked tumours and protozoan parasites
Site of Blood formation
• Blood formation occurs at different site in the fishes
• Erythrocytes are mainly produce in the kidney and
spleen in most fishes.
• In elasmobranchs, the organ of Leydig is the site of
production of rbc
• This is usually associated with the walls of the
alimentary canal, commonly seen along the
esophagus
• Similar tissues may occur in various places
(mesenteries, the orbit, base of cranium) in other
fishes
Circulation in fish
The heart of a teleost fish
• In teleost, the heart is
normally situated below
the
pharynx
and
immediately
behind the
gills
• A fish heart has 4 chambers,
but
unlike
in
other
mammals, the chambers of
the heart are not all
muscular, and are not built
into a single organ, rather
they are arranged one
behind the other
The Fish Heart
• The pump.
• The heart is the pump that
generates the driving pressure
for the circulation of the
blood.
• The fish heart has one atrium
and one ventricle; this is in
contrast to the human heart
(mammalian) which has two
separate atriums and two
separate ventricles.
• In the fish heart, two other
chambers can also be found,
the sinus venous and the
bulbous arteriosus.
Blood Circulation
•
•
•
•
•
•
•
The blood from the body, which is low in
oxygen, enters the atrium via the sinus
venous, which contains the pacemaker
cells that initiate contractions .
The blood is pumped into the ventricle by
the atrium, which is a thin walled
muscular chamber.
Then the blood is pumped into the bulbus
arteriosus by the ventricle: a thick-walled
chamber with lots of cardiac muscle.
The ventricle is responsible for the
generation of blood pressure .
The last chamber, the bulbus arteriosus, is
a unique structure and one of its functions
is to dampen the pressure pulse generated
by the ventricle. Why?
The next organ after the bulbus arteriosus
are the gills, and they are thin walled and
may be damaged if the pulse pressure/
absolute pressure become too high.
The bulbus arteriosus contains the elastic
components but not many muscle fibres.
Heart components
• Sinus venosus, (SV) this is the
first chamber of the heart.
• Preliminary
collecting
chamber
• In teleost, it is filled by 2 major
veins- hepatic veins and the
left and right branches of the
Curvierian ducts, which in turn
collect blood from the paired
(left and right) lateral veins,
inferior jugulars, anterior
cardinals
and
posterior
cardinals.
• Note in elasmobranchs, only
one hepatic vein empty into
the sinus venosus
Atrium
• The
atrium
collect
blood from the SV
• This is the largest
chamber of the heart
and weakly muscular
• Pushes blood with weak
contractions
towards
the ventricle
Ventricle
• This is the only well
muscled chamber of the
heart.
• Nearly as large as the
atrium
• The work horse of the
heart
• Its contraction push
blood around the body
Bulbus arteriosus
• The last chamber of the
fish heart is called bulbus
arteriosus in teleost.
• In elasmobranchs, it is
called cornus arteriosus
• The difference between
this chambers is that the
cornus arteriosus of
sharks and rays contain
many valves while the
bulbus arteriosus of bony
fish contain none
Circulation in fish
•
•
•
•
•
The fish heart needs to generate the driving
pressure for both the gills (lungs in mammals) and
the body since they are connected in series, as seen
in the figure to the right.
In mammals both sides of the heart pump the same
volume per time unit, but the pressure generation
is very different in the right and left side. The right
ventricle only generates a fraction of the pressure
compared to the left ventricle (which is the
pressure you measure during a physical exam.
To optimize the gas exchange in the lungs, the
diffusion distance needs to me minimized. A small
diffusion distance means thin membranes.
In fish, the heart pumps blood first to the gills
where the gas exchange takes places, and then the
blood continues to the rest of the body. This is a
fine balance, since the fish's gills (like the mammal's
lungs) have to be thin walled to facilitate gas
exchange ,and thus cannot tolerate high blood
pressure.
At the same time, the blood pressure will drop
when the blood cells squeeze through the lamellae ,
and the blood pressure that remains after the blood
had passed through the gills has to be high enough
to drive the blood around the body.
The Coronary system- fish and human
• The mammalian heart is supplied
with oxygen by the coronary
circulation.
• Some fishes such as salmons have
coronary circulation with some
difference
• Since the blood is oxygenated in
the gills, the first source that can
be used to supply the heart with
oxygenated blood is found after
the gills. This is where the
coronay circulation start in fish
• Coversely, in human the coronary
circulation start just at the base
of aorta that received oxygenated
blood from the left ventricle
Composition of the myocardium
• This is divided into compact and spongy muscle
• In mammals, the compact myocardium make of
about 99% of the total muscle mass, while in the
salmons, only about 40% is compact while the
rest is spongy
• It is only the compact myocardium that is
supplied by coronary circulation
• The spongy myocardium takes up oxygen from
the deoxygenated blood in the lumen of the
heart
THANKS FOR LISTENING