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Circulatory System FUNCTIONAL ANATOMY (ZOO124.1.0) 1 Types ¢ Gastrovascular ¢ Open ¢ Closed 2 1 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. 3 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 4 system as well as a Cnidarian Gastrovascular Systems digestive cavity 2 Flat Worm Gastrovascular System 5 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 6 3 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. 7 Open Circulatory System 8 4 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. 9 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. 10 5 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. 11 Closed Circulatory System 12 6 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. 13 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. 14 7 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 15 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 16 8 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 17 Cartilaginous Fishes • Atrium • Thin walled muscular sac • A-V valve regulates flow between atrium & Ventricle • Ventricle • Thick muscular walls 18 9 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) 19 Bulbus & Conus Arteriosus Cyclostomata: Lamprey Primitive Teleost Chondrichthyes: Shark 20 Modern Teleost 10 Teleosts 21 Amphibians •Typical amphibian heart 22 11 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 23 Amphibians • Shortening of ventral aorta ensures movement of oxygenated & deoxygenated blood in to the right vessels. 24 12 Amphibians 25 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 26 13 Amniotes • Ventral aorta emerges from heart & passes forward beneath the pharynx • Dorsal aorta passes caudally above the digestive system • 27 Reptiles Blood flow 28 14 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) 29 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? 30 15 Reptiles Chelonian & Squamate heart 31 Reptiles Chelonian & Squamate heart 32 16 Reptiles Turtle heart flow during air breathing (R) & diving (L) 33 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. 34 17 Crocodilians •Ventricular septum is complete. Foramen of Panizza connects the base of the R & L systemic arches Left Systemic can receive R. ventricle blood 35 Crocodilians 36 18 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 37 (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. 38 19 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). 39 Role of Foramen of Panizza 40 20 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 41 lungs to the left side of heart goes to systemic circulation. AORTIC ARCHES 42 21 Typical Aortic Arches 43 Aortic Arches of Sharks 44 22 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 45 Result: Blood entering an aortic arch from ventral aorta must pass through gill capillaries before proceeding to dorsal aorta Teleosts 46 23 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 47 Amphibians 48 24 Amphibians 49 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 50 • Dorsal aorta between arches 3 & 4 is lost. Therefore, from arch 3 blood goes to head 25 Reptiles 51 Birds & Mammals 52 26 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 53 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 54 27 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 55 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 28 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 57 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 58 29 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 60 30 Mammalian Fetus 4. blood that does enter the right ventricle largely bypasses the pulmonary circulation via the ductus arteriosus 61 Changes at Birth 1. Ductus arteriosus closes 2. Foramen ovale sealed off 3. Blood no longer flows through umbilical vein 62 31 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 • 63 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 32