Post on 12-Mar-2018
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Fig. 19.1. Spleen.
Spleen • White pulp – macrophages, monocyte storage
• Red pulp - (RBC) storage, and prod’n (in non-mammals)
Vertebrate hearts • Pericardial cavity – division in coelum
• Endocardium = endothelium of blood vessels
smooth
muscle endothelium
elastic tissue elastic tissue
smooth muscle endothelium
endothelium
smooth muscle,
elastic fibers
endothelium
valve
Artery
Arteriole
Capillary
Vein
Arteries contain
connective tissue
with elastin and
collagen
Veins include
valves
Vessel walls
Artery Vein
Vein Artery
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Large arteries
• Elastic recoil from
arteries drives flow of
blood during diastole
• Arteries temporarily
expand and hold
pumped blood
Systole
Diastole
Veins
• Most of the blood volume is in venous system (60-70%) - resevoir
• Blood volume is variable
Vertebrate circulation Vertebrate circulatory systems are either a single circuit (fish) or double circuit (tetrapods) Early circulation - amphibian
26 day old human embryo p. 607
Heart and vessel development
Ventral aorta, aortic arches, dorsal aorta
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Ancestral vertebrate pattern
VI V IV III II I
Heart
Ventral Aorta
Dorsal Aorta
Internal Carotid
1 2 4 3 5 6
Paired dorsal Aortae
Venous development
• Sinous venosus, hepatic portal system
Fish circulation • Heart is below pharynx, near gills
• 4 chambers in sequence
• Stiff tissue around heart allow sinus venosus suction during diastole (no collapse)
Fish circulation – Conus arteriosus – muscular, maintains
pressure during diastole
• Teleosts – bulbus arteriosus – enlarged elastic ventral aorta
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Fish circulation
In fish, the aortic arches (AA) are the afferent and efferent branchial arteries
Aortic arches
Aortic arches in tetrapods • 3rd AA – Carotid
• 4th AA – Systemic arch (dorsal aorta - many branches!)
• 6th AA – Pulmonary arch
Tetrapod hearts
• Sinus venosus and conus arteriosis are lost/reduced
– sinus venosus reduced to junction of vena cava and rt. atrium
• Blood returns from two sources
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Many tetrapods have incomplete separations
• Amphibians
• Dipnoi
• Ancestral crossopterygii
• Reptiles
Often not using lungs!
Most blood in systemic
Shunting a must
A fish with
pulmonary
circulation
In other fish,
swim bladders
supplied from
dorsal aorta
facing
2 3 4 5 6
Lungfish aortic arches
Aquatic
On land
Has incomplete separation of both rt. & lt. atria; and rt. & lt. ventricles
Yet two ‘streams’ are separate
O2 poor to 5th and 6th (back gills and lung).
O2 rich to 3rd and 4th.
Spiral valve in conus spiral
valve
AA 3 and 4
AA 5 and 6
Ventricle septum
Lungfish heart Amphibian circulation
• Metamorphosis – heart moves towards lungs
• AA’s are ‘traditional’ tetrapod: 3,4,6 (frog)
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Amphibian heart • Atria are completely divided, ventricle
division is incomplete
– Yet very little mixing occurs
Amphibian heart
• Ventricle has spongy pockets (trabeculae)
• Trabeculae separate deoxy. and oxygenated blood in ventricle
trabeculae
trabeculae
Frog heart Frog heart
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Frog heart
Ventricle
contraction
Frog heart
Frog spiral valve • Spiral valve in conus arteriosus
Ventral aorta
shortened
to truncus
arteriosus
Reptile circulation • Truncus arteriosus
has three trunks
P
LS RS
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• When not ventilating lungs, pulmonary resistance increases, blood is shunted from rt ventricle to lt systemic
Reptile heart • High CO2, acidity causes Bohr effect and
hemoglobin loses affinity for O2
Reptile heart
Saturation curve shifts to the right
sea snake
Crocodilia heart
• Ventricles divided
• Crocodiles have foramen of Panizza connecting rt. and lf. systemic
• Lf systemic can receive rt. ventricle blood
Crocodilia heart
• Using lungs
– Foramen of Panizza allows Ox. blood into left systemic
Left to right shunt
higher pressure valve
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• Diving-
– F. of P. allows mixed blood to flow into right systemic
Right to left shunt
Cog
lower pressure
Crocodilia heart Bird Mammal
p.618
• Systemic arch is one-sided in endotherms
Human heart development
One-way flow
in early
development
Adult mammal circulation
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Amniote fetus circulation
• Oxygenated blood to fetus coming from outside, not lungs
–developing reptiles, birds, mammals
Fetal circulation • Blood flows through umbilical vein,
through ductus venosus to vena cava
Fetal circulation
• Most blood from lt atrium goes through foramen ovale to rt atrium
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Fetal circulation • Meanwhile....some blood in right atrium
goes instead to right ventricle
Most right ventricle
blood goes through
ductus arteriosus
to aorta
At birth pulmonary pressure reduces below systemic
Foramen ovale Fossa ovalis
After a day or more:
Ductus arteriosus Ligamentum arteriosum
Neonatal circulation
Neonatal problems
Patent foramen ovale (20% of people) chest pressure causes flap to open, strokes
Patent ductus arteriosus Heart can become enlarged
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Portal systems
• With portal system:
Veins branch again into capillaries
portal vein
Hepatic portal system
• Newly absorbed compounds are brought to liver
• Conservative: found in all vertebrates
Renal portal system • From hind limbs to kidney, resorbing
portion of kidney circulation
• All vertebrates except mammals