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Circulatory System
FUNCTIONAL
ANATOMY
(ZOO124.1.0)
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Types
¢ Gastrovascular
¢
Open
¢
Closed
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Absence of Circulatory System
—
Very small animals may not need.
—
Small size may permit nutrients and
other substances to reach the body parts
via simple diffusion.
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Larger Animals without a
Separate Circulatory Systems
Sea anemones,
Jelly fish &
earth worms
lack a true
system.
The gastrovascular
cavity extends to most
areas of the body in
these animals and
serves as a circulatory
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system as well as a
Cnidarian
Gastrovascular
Systems
digestive cavity
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Flat Worm Gastrovascular
System
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Circulatory System
—
For large and active animals, more
efficient system is needed for internal
transport
—
Two types of circulatory systems are found
— Open
Circulatory System
— Closed
Circulatory System
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Open Circulatory System
¢ Hemolymph
leaves the
heart in short, branched
arteries that open up into
large spaces called sinuses.
¢ Hemolymph
percolates
around organs, directly
bathing the cells.
¢ Hemolymph
then returns to
the heart directly or
through short veins.
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Open Circulatory System
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Open Circulatory System
¢ Advantage
- Exchange of materials is direct
between the hemolymph and tissues. There
is no diffusion barrier.
¢ Disadvantage -
Little fine control over
distribution of the hemolymph to body
regions. No mechanism for reducing flow to a
specific part of an organ.
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Open Circulatory System
¢ Open
circulatory systems tend to be found in
more inactive animals.
¢ Most
molluscs have an open system, but the
highly active cephalopods (squid and octopus)
have evolved a closed system.
¢ Insects
have circumvented limitation of their
open system by their tracheal system for
oxygen supply.
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Closed Circulatory System
¢ The
blood is contained within a
completely closed system of
vessels.
¢ Vessels
form a closed loop,
usually with some sort of
pumping organ like a heart or
contractile vessels.
¢ Vessels
branch into smaller &
smaller tubes that penetrate
among the cells of tissues.
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Closed Circulatory System
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Closed Circulatory System
Advantages
¢ Fine-scale
control over the distribution of
blood to different body regions is possible.
¢ Muscular
walls of vessels can constrict and
dilate to vary the amount of flow through
specific vessels.
¢ Blood
pressures are fairly high and the
circulation can be vigorous.
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Vertebrate Vascular
System
Arteries and arterioles
have a layer of smooth
muscle tissue which
allows them to contract
(vasoconstrict) &
expand (vasodilate),
altering their diameter
and thus blood flow.
Walls of arteries and arterioles have many
elastic fibers enabling them to withstand high
pressures.
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Vertebrate Circulatory
System
• Arteries
• Carr blood away from the heart
• Have muscular elastic walls
• Terminate in capillary beds
• Capillaries
• Very thin walls (endothelium only)
• Less muscle in their walls than arteries
• Begin at the end of capillary bed
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Vertebrate Circulatory
System
• Veins
• Carry blood back to the heart
• Have less muscle in their walls than arteries
• Begin at the end of capillary beds
• Heart
• A muscular pump
• Contains a pacemaker to regulate rate but
influenced by autonomic nervous system
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Cartilaginous Fishes
• Single circuit heart with 4 chambers
• Sinus Venosus
• Atrium
• Ventricle
• Conus arteriosus
• Sinus Venous
• Receive blood from & filled by suction when
ventricle contracts & enlarges the pericardial
cavity
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Cartilaginous Fishes
• Atrium
• Thin walled
muscular sac
• A-V valve
regulates flow
between atrium &
Ventricle
• Ventricle
• Thick muscular
walls
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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)
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Bulbus & Conus Arteriosus
Cyclostomata: Lamprey
Primitive
Teleost
Chondrichthyes: Shark
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Modern Teleost
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Teleosts
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Amphibians
•Typical
amphibian heart
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Amphibians
• Modifications are aliened with
the presence of the lung
• Partial or complete partition
within atrium (complete in
some anurans)
•Ventricular
(Bullfrog)
trabeculae
• Formation of a spiral valve in
the conus arteriosus
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Amphibians
• Shortening
of ventral
aorta ensures
movement of
oxygenated &
deoxygenated
blood in to the
right vessels.
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Amphibians
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Amniotes
• Heart consists of 2 atria and 2 ventricles,
except for birds & mammals – Sinus Venosus
• Complete inter-atrial septum
• Complete inter-ventricular septum (Crocodiles
birds, & mammals) & partial septum in other
amniotes
• Supply the body with oxygenated blood but
carry deoxygenated blood to the lungs
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Amniotes
• Ventral aorta emerges from heart & passes
forward beneath the pharynx
• Dorsal aorta passes caudally above the
digestive system
•
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Reptiles
Blood flow
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Reptiles
• 3 aortic arches in adults (III, IV, V)
• Ventral aorta - conus arteriosus is split into 3
separate passages: 2 aortic trunks & a
pulmonary trunk.
As a result
• Pulmonary trunk emerges from the right
ventricle & connects with 6th aortic arches.
(Deoxygenated blood from right atrium goes
to lungs)
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Reptiles
• One aortic trunk comes out of left ventricle &
carries oxygenated blood to the right 4th aortic
arch & to carotid arches
• The other aortic trunk appears to come out of
right ventricle & leads to left 4th aortic arch. So,
does the left 4th arch carry oxygenated blood?
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Reptiles
Chelonian
&
Squamate
heart
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Reptiles
Chelonian
&
Squamate
heart
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Reptiles
Turtle heart
flow during
air
breathing
(R) &
diving (L)
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Reptiles
• In turtles, snakes, & lizards – the inter-ventricular
septum is incomplete.
• Right & left systemic arches leave the ventricle, &
trabeculae in that region of the heart form a pocket
called Cavum Venosum
• Oxygenated blood from the left ventricle is
directed into cavum venosum, which leads to the
systemic arches.
• Therefore, both left & right systemic arches
receive oxygenated blood.
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Crocodilians
•Ventricular septum
is complete.
Foramen of
Panizza connects
the base of the R &
L systemic arches
Left Systemic
can receive
R. ventricle
blood
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Crocodilians
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Role of Foramen of Panizza
• When a crocodilian is above water and
breathing air, the semilunar valve in the right
aorta remains closed because of higher
pressure in the left & right aorta (higher than in
the right ventricle).
• As a result, the right aorta receives blood from
the left aorta (so both aortas carry oxygenated
blood) and blood from the right ventricle (low in
oxygen) passes only into the pulmonary artery
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(and goes to the lungs).
Role of Foramen of Panizza
• When a crocodilian is under water and not
breathing, right ventricular pressure increases due
to pulmonary resistance (vasoconstriction of blood
vessels supplying the lungs).
• As a result, the semilunar valve in the right aorta is
now forced open so some of the blood from the right
ventricle now enters the right aorta rather than the
pulmonary artery.
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Role of Foramen of Panizza
• Rather than going to the lungs (where there is little
or no oxygen), some of the blood enters the systemic
(body) circulation.
• Vital organs & tissues (such as skeletal muscles
and the central nervous system) will get an increased
blood supply and additional oxygen. This, in turn,
allows a crocodilian to stay underwater longer
(important because many crocodilians hunt by
remaining underwater & 'ambushing' prey that
come for a drink or to cool off).
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Role of Foramen of Panizza
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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
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lungs to the left side of heart goes to systemic
circulation.
AORTIC ARCHES
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Typical Aortic Arches
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Aortic Arches of Sharks
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Aortic Arches of Fishes
• Ventral aorta extends beyond the pharynx and
connects developing aortic arches. Ist pair of arches
reduces to a small Spriacle in the embryo.
• Other pairs (III-VI) give rise to pre & post-trematic
arteries
• Arches III-VI become occluded &
• Dorsal segments = efferent branchial arteries
• Ventral segments = afferent branchial arteries
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Result: Blood entering an aortic arch from ventral aorta must
pass through gill capillaries before proceeding to dorsal aorta
Teleosts
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Teleosts
• The same changes convert 6 pairs of embryonic
aortic arches into afferent & efferent branchial
arteries.
• Arches I & II - lost
• III – VI are functional Arches
• Dorsal segments = efferent branchial arteries
• Ventral segments = afferent branchial arteries
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Amphibians
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Amphibians
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Amphibians
• Urodeles
(Salamanders)- most terrestrial
urodeles have 4 pairs of arches; aquatic urodeles
typically have 3 pairs (III, IV, & V).
• Anurans – Have 4 arches early in development
(larval stage); arch VI develops a pulmonary artery
(to lungs) while arches III, IV, & V supply larval gills.
• At metamorphosis:
• Aortic arch 5 is lost
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• Dorsal aorta between arches 3 & 4 is lost.
Therefore, from arch 3 blood goes to head
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Reptiles
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Birds & Mammals
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Circulatory Systems
FISHES
AMPHIBIANS
REPTILES (EXCEPT BIRDS)
MAMMALS AND BIRDS
Gill capillaries
Lung and skin capillaries
Lung capillaries
Lung capillaries
Artery
Pulmocutaneous
circuit
Gill
circulation
Heart:
ventricle (V)
A
A
Atrium (A)
Systemic
Vein circulation
Systemic capillaries
V
Right
Left
Right
systemic
aorta
Pulmonary
circuit
A
V
Right
Left
A
Systemic
V aorta
Left
A
A
V
Right
V
Left
Systemic
circuit
Systemic
circuit
Systemic capillaries
Pulmonary
circuit
Systemic capillaries
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Systemic capillaries
Venous System
• In early vertebrate embryos, venous channels
conform to a single basic pattern. As development
proceeds, these channels are modified by deletion of
some vessels & addition of others. The primary
venous pathways include.
• Cardinal
• Renal Portal
• Lateral abdominal
• Hepatic Portal
• Coronary
• Pulmonary
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Venous Channels - Sharks
• Cardinal
• Sinus venosus receives all blood returning to the
heart.
• Renal Portal
• All the caudal end blood goes through kidney
• Lateral abdominal
• Starts at pelvic fin & passes along lateral body
wall
• Hepatic Portal
• Among 1st vessels to appear in embryos are Vitelline
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veins. One Vitelline vein joins with embryonic
Subintestinal vein & becomes the Hepatic Portal System
Venous Channels – Other
Animals
• Cyclostomes have no renal portals In most bony
fishes the lateral abdominals are absent & the
pelvic fins are drained by post-cardinals
• Urodeles - posterior cardinals persist between
caudal vein & common cardinals in adults
• Anurans, most reptiles, & birds - posterior
cardinals are lost anterior to kidneys
• Mammals - right posterior cardinal persists; part56
of left posterior cardinal persists
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Renal Portal System
• Amphibians & some reptiles - carries some blood
from the hind limbs to the renal portal vein. This
channel provides an alternate route from the hind
limbs to the heart.
• Crocodilians & birds - some blood passing from
hind limbs go straight through the kidneys
• Mammals - renal portal system not present in
adults
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Hepatic Portal System
• Similar in all vertebrates; drains stomach,
pancreas, intestine, & spleen & terminates in
capillaries of liver
• Pulmonary veins - carry blood from lungs to
left atrium in lungfish & tetrapods
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Mammalian Fetus
• Circulation in mammalian fetus changes at
birth -In a developing fetus, blood obtains
oxygen via the placenta.
• As a result, blood flow must largely bypass the
lungs so that oxygentated blood can get to other
developing tissues.
• Getting oxygenated blood from the placenta
back to the heart & out to the body as quickly
and efficiently as possible involves a series of
vessels & openings found only in a mammalian 59
fetus:
Mammalian Fetus
1. blood (with oxygen & nutrients acquired in
placenta) passes into umbilical vein
2. blood largely bypasses the liver via the
ductus venosus
3. blood returns to the heart & enters right
atrium, but much of the blood then
bypasses the right ventricle & enters the
left atrium via the foramen ovale
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Mammalian Fetus
4. blood that does enter the right ventricle
largely
bypasses
the
pulmonary
circulation via the ductus arteriosus
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Changes at Birth
1. Ductus arteriosus closes
2. Foramen ovale sealed off
3. Blood no longer flows through umbilical vein
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Lymph System
• Found in all vertebrates; consists of
lymph vessels, lymph nodes, &, in some
species, lymph hearts, Lymph vessels
• Found in most soft tissues of the body &
begin as blind-end lymph capillaries that
collect interstitial fluid
•
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Lymph System
• valves present (in birds & mammals) that prevent
back flow to empty into 1 or more veins (e.g.,
caudal, iliac, sub-clavian, & posterior cardinal)
• Lymph nodes - located along lymph vessels;
contain lots of lymphocytes & macrophages
(phagocytic cells)
•Lymph hearts - consist of pulsating smooth
muscle that propels lymph fluid through lymph64
vessels; found in fish, amphibians, & reptiles
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