Circulatory system

Spleen White pulp – macrophages, monocyte storage Red pulp - (RBC) storage, and prod’n (in non-mammals)

Vertebrate hearts Pericardial cavity – division in coelum Endocardium continuous w/endothelium of blood vessels

Blood vessels

Artery Arteriole Capillary Vein Arteries contain connective tissue with elastin and collagen smooth muscle Artery endothelium elastic tissue elastic tissue Arteriole smooth muscle endothelium Capillary endothelium endothelium Vein Veins include valves smooth muscle, elastic fibers valve

Vessel walls Artery Vein Artery Vein

Large arteries Systole Elastic recoil from arteries drives flow of blood during diastole Arteries temporarily expand and hold pumped blood 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)

Heart and vessel development 26 day old human embryo Early circulation - amphibian Ventral aorta, aortic arches, dorsal aorta

Ancestral vertebrate pattern Dorsal Aorta Paired dorsal Aortae Internal Carotid 6 5 4 3 2 VI V IV III II 1 I Ventral Aorta Heart

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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

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

Many tetrapods have incomplete separations Amphibians Dipnoi Ancestral crossopterygii Reptiles

Many tetrapods have incomplete separations Amphibians Dipnoi Ancestral crossopterygii Reptiles Often not using lungs! Most blood in systemic Shunting a must

Lungfish aortic arches facing A fish with pulmonary circulation In other fish, swim bladders supplied from dorsal aorta Aquatic 2 3 4 5 6 On land

Lungfish heart 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 AA 3 and 4 AA 5 and 6 spiral valve Ventricle septum

Amphibian circulation Metamorphosis – heart moves towards lungs AA’s are ‘traditional’ tetrapod: 3,4,6 (frog) Heart moves caudally to lungs

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

Frog heart

Frog heart

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 RS LS P

Reptile heart 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 sea snake Saturation curve shifts to the right

Early ventricle contraction

Late ventricle contraction

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 higher pressure valve Using lungs Foramen of Panizza allows Ox. blood into left systemic

Crocodilia heart Diving- lower pressure Diving- F. of P. allows mixed blood to flow into right systemic Cog

Bird Mammal Systemic arch is one-sided in endotherms p.618

Dinosaur heart – endothermic! N.C. Museum of Natural Science

Human development

Human heart development One-way flow in early development

Adult mammal circulation

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 right atrium goes through foramen ovale to left atrium

Fetal circulation Meanwhile....some blood in right atrium goes instead to right ventricle Most right ventricle blood goes through ductus arteriosus to aorta

Neonatal circulation At birth pulmonary pressure reduces below systemic Foramen ovale Fossa ovalis After a day or more: Ductus arteriosus Ligamentum arteriosum

Neonatal problems Patent foramen ovale Patent ductus arteriosus (20% of people) chest pressure causes flap to open, strokes Patent ductus arteriosus Heart can become enlarged

Venous systems Normally: Arteries Capillaries Veins Heart

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