Vertebrate of the cardiovascular system The closed circulatory

Vertebrate of the cardiovascular system • The closed circulatory system of humans and other vertebrates is often called the cardiovascular system. • The heart consists of one atrium or two atria, the chambers that receive blood returning to the heart, and one or two ventricles, the chambers that pump blood out of the heart.

• Arteries, veins, and capillaries are three main kinds of blood vessels. – Arteries carry blood away from the heart to organs. – Within organs, arteries branch into arterioles, small vessels that convey blood to capillaries. – Capillaries with very thin, porous walls form networks, called capillary beds, that infiltrate each tissue. – Chemicals, including dissolved gases, are exchanged across the thin walls of the capillaries between the blood and interstitial fluid. – At their “downstream” end, capillaries converge into venules, and venules converge into veins, which return blood to the heart.

• Arteries and veins are distinguished by the direction in which they carry blood, not by the characteristics of the blood they carry. – All arteries carry blood from the heart toward capillaries. – Veins return blood to the heart from capillaries.

• Metabolic rate is an important factor in the evolution of cardiovascular systems. – In general, animals with high metabolic rates have more complex circulatory systems and more powerful hearts than animals with low metabolic rates. – Similarly, the complexity and number of blood vessels in a particular organ are correlated with that organ’s metabolic requirements.

Elasmobranches heart • 3 chambers ( atrium, ventricle , conus ). • Thy are situated in pericardium.

Atrial. Contraction -fills the ventricle and the conus -valve prevents blood entering the aorta

• Ventricular Contraction • Decrease in pericardial pressure; • Expands atria; • Assists in filling (suction effect);

Conal Contraction contraction starts near the ventricle valves prevent backflow

Function of the pericardium and pericardioperitoneal canal in elasmobranch fishes • May be inadequate absorption of pericardial fluid. • We conclude that the pericardioperitoneal canal maintains negative pericardial pressure, which is a prerequisite in elasmobranch fishes and may serve to regulate pericardial pressure level to optimize cardiac function in relation to changes in cardiac size. • AJP - Heart and Circulatory Physiology, Vol 248, Issue 2 198 -H 207, Copyright © 1985 by American Physiological Society

Fish Heart (cont. ) • Sinus venosus – Thin walled venous chamber – Receives blood from: coronary veins, hepatic veins • Atrium – Large and thin walled – Dorsal to ventricle

Fish Heart (cont. ) • Ventricle – Dumps into Bulbus artriosus- continuous with aorta • Bulbus arteriosus : a bulb has a wall similar to artery wall. • Except bulpus all are contractile. Chambers separated by valves: sino-atrial , sinoventricular, semi-lunar valve

-Conus - Muscular extension of ventricle. – Bulbus - Elastic, extension of ventral aorta

LINGCOD -Ventricle contraction : BP arise in bulbus but after apart of sec. 45 mm. Hg 38 30 22 -Ventricle relax: backflow preven so blood exist in bulbus so it will mentain high BP -BULBUS DOSN’T COTRACT BUT its elasticity serve to maintain blood flow to ventral aorta during ventral diastolic. But ventral BP here dosnt equal the Bp in ventricle systolic

Fish Heart • A fish heart has two main chambers, one atrium and one ventricle or( 4) if all. • Blood is pumped from the ventricle to the gills (the gill circulation) where it picks upoxygen and disposes ofcarbon dioxide across the capillary walls. • The gill capillaries converge into a vessel that carries oxygenated blood to capillary beds at the other organs (the systemic circulation) and back to the heart.

• In fish, blood must pass through two capillary beds, the gill capillaries and systemic capillaries. – When blood flows through a capillary bed, blood pressure - the motive force for circulation - drops substantially. – Therefore, oxygen-rich blood leaving the gills flows to the systemic circulation quite slowly (although the process is aided by body movements during swimming). – This constrains the delivery of oxygen to body tissues, and hence the maximum aerobic metabolic rate of fishes.

Fish Heart • blood pressure from ventricle is reduced in gills – low pressure in aorta – But it is adequate to meet : – Cold blooded animals – Low circulation in muscle – Bouncy

Fish Circulatory System • African lungfish – exposed to dry conditions or low O 2 water – Out pocketing of gut – air is gulped – blood vessels surrounding the “lung” take up the O 2

Fish Circulatory System – divided atria – partially divided ventricle – left side of atrium receives oxygenated blood (to tissues) – right side receives deoxygenated blood (to lung or gills)

-Lungs to left atrium -Right atrium receive from body system -More oxygenated blood to head and body -Less oxy- blood to gills ( gills are degenerated but few are remain) -Separation is important in air- breathing but not important in water

a spiral valve in the bulbus arteriosus directs oxygenated blood returning from the lungs into arches III and IV

Fig. 19. 9. Aortic arches and circulation of African lungfish.

• Teleost fish • • 4 chambered heart, 1 ventricle • • some mixing of oxygenated and deoxygenated blood. • • Systemic circulation is low pressure after passing through the gills. • Lungfish • • 4 chamber, 1 ventricle • • oxygenated and deoxygenated blood separated by septa.

One or two circulation loop !! • Why divided chambers : (Two loop circulation) ? ? ? • To separate oxy and deoxygenated blood • Blood pressure needed in the two circulation is differ • What about fish: • Has one circulation loop. • But no problem because - it has the separation - Don’t need high BP in systemic circulation.