Which Of The Following Animals Has A Single-loop Closed Circulatory System?

Chapter 21. The Circulatory Organisation

21.1. Overview of the Circulatory Organisation

Learning Objectives

Past the end of this section, you volition be able to:

Depict an open and closed circulatory system
Describe interstitial fluid and hemolymph
Compare and dissimilarity the organization and development of the vertebrate circulatory system.

In all animals, except a few uncomplicated types, the circulatory organization is used to transport nutrients and gases through the body. Simple improvidence allows some water, nutrient, waste product, and gas substitution into archaic animals that are only a few prison cell layers thick; however, bulk flow is the merely method by which the entire body of larger more than complex organisms is accessed.

Circulatory Arrangement Architecture

The circulatory system is effectively a network of cylindrical vessels: the arteries, veins, and capillaries that emanate from a pump, the eye. In all vertebrate organisms, as well equally some invertebrates, this is a closed-loop system, in which the blood is non gratis in a cavity. In a closed circulatory system, blood is independent inside blood vessels and circulates unidirectionally from the heart around the systemic circulatory route, then returns to the eye again, every bit illustrated in Figure 21.2 a . As opposed to a airtight system, arthropods—including insects, crustaceans, and about mollusks—have an open circulatory system, every bit illustrated in Figure 21.2 b . In an open circulatory system, the blood is not enclosed in the claret vessels only is pumped into a cavity chosen a hemocoel and is chosen hemolymph because the claret mixes with the interstitial fluid. As the middle beats and the animal moves, the hemolymph circulates around the organs within the torso crenel and then reenters the hearts through openings called ostia. This move allows for gas and nutrient commutation. An open circulatory system does not use as much energy as a airtight system to operate or to maintain; nevertheless, there is a trade-off with the amount of claret that tin be moved to metabolically agile organs and tissues that require high levels of oxygen. In fact, one reason that insects with wing spans of up to two feet wide (lxx cm) are not around today is probably because they were outcompeted by the arrival of birds 150 million years ago. Birds, having a closed circulatory system, are thought to take moved more than agilely, allowing them to go food faster and possibly to prey on the insects.

Figure_40_01_01ab — Effigy 21.ii. In (a) airtight circulatory systems, the heart pumps blood through vessels that are separate from the interstitial fluid of the trunk. Most vertebrates and some invertebrates, similar this annelid earthworm, take a closed circulatory system. In (b) open circulatory systems, a fluid chosen hemolymph is pumped through a blood vessel that empties into the torso cavity. Hemolymph returns to the blood vessel through openings called ostia. Arthropods similar this bee and most mollusks take open up circulatory systems.

Circulatory Organization Variation in Animals

The circulatory system varies from simple systems in invertebrates to more complex systems in vertebrates. The simplest animals, such as the sponges (Porifera) and rotifers (Rotifera), practice not need a circulatory arrangement considering diffusion allows acceptable commutation of water, nutrients, and waste, as well equally dissolved gases, as shown in Figure 21.iii a . Organisms that are more complex but still only have two layers of cells in their torso plan, such as jellies (Cnidaria) and comb jellies (Ctenophora) also utilize improvidence through their epidermis and internally through the gastrovascular compartment. Both their internal and external tissues are bathed in an aqueous environment and commutation fluids by diffusion on both sides, every bit illustrated in Figure 21.3 b . Exchange of fluids is assisted by the pulsing of the jellyfish body.

For more complex organisms, diffusion is not efficient for cycling gases, nutrients, and waste matter effectively through the torso; therefore, more complex circulatory systems evolved. Well-nigh arthropods and many mollusks have open circulatory systems. In an open system, an elongated chirapsia heart pushes the hemolymph through the trunk and muscle contractions aid to move fluids. The larger more circuitous crustaceans, including lobsters, have adult arterial-like vessels to push blood through their bodies, and the nearly active mollusks, such as squids, take evolved a closed circulatory organisation and are able to move rapidly to catch prey. Airtight circulatory systems are a feature of vertebrates; however, there are significant differences in the structure of the center and the apportionment of claret between the unlike vertebrate groups due to adaptation during evolution and associated differences in beefcake. Figure 21.4 illustrates the basic circulatory systems of some vertebrates: fish, amphibians, reptiles, and mammals.

Figure_40_01_03abcd — Figure 21.4. (a) Fish have the simplest circulatory systems of the vertebrates: blood flows unidirectionally from the 2-chambered heart through the gills then the remainder of the body. (b) Amphibians have two circulatory routes: ane for oxygenation of the claret through the lungs and skin, and the other to take oxygen to the residue of the body. The blood is pumped from a three-chambered heart with ii atria and a single ventricle. (c) Reptiles also accept ii circulatory routes; notwithstanding, blood is only oxygenated through the lungs. The heart is iii chambered, just the ventricles are partially separated so some mixing of oxygenated and deoxygenated blood occurs except in crocodilians and birds. (d) Mammals and birds accept the almost efficient heart with four chambers that completely separate the oxygenated and deoxygenated claret; it pumps just oxygenated blood through the torso and deoxygenated blood to the lungs.

Equally illustrated in Figure 21.iv a Fish have a single circuit for blood period and a 2-chambered heart that has but a single atrium and a single ventricle. The atrium collects claret that has returned from the torso and the ventricle pumps the blood to the gills where gas substitution occurs and the blood is re-oxygenated; this is called gill apportionment. The blood then continues through the residuum of the trunk before arriving dorsum at the atrium; this is chosen systemic apportionment. This unidirectional flow of blood produces a slope of oxygenated to deoxygenated blood around the fish'south systemic circuit. The consequence is a limit in the amount of oxygen that can reach some of the organs and tissues of the body, reducing the overall metabolic chapters of fish.

In amphibians, reptiles, birds, and mammals, claret flow is directed in 2 circuits: i through the lungs and dorsum to the heart, which is called pulmonary circulation, and the other throughout the residue of the body and its organs including the brain (systemic circulation). In amphibians, gas exchange besides occurs through the skin during pulmonary circulation and is referred to equally pulmocutaneous circulation.

As shown in Figure 21.four b , amphibians have a three-chambered heart that has two atria and one ventricle rather than the ii-chambered centre of fish. The two atria (superior heart chambers) receive claret from the ii different circuits (the lungs and the systems), and so in that location is some mixing of the blood in the center'southward ventricle (inferior heart chamber), which reduces the efficiency of oxygenation. The advantage to this arrangement is that high pressure in the vessels pushes blood to the lungs and body. The mixing is mitigated by a ridge within the ventricle that diverts oxygen-rich claret through the systemic circulatory system and deoxygenated claret to the pulmocutaneous circuit. For this reason, amphibians are frequently described every bit having double circulation.

Most reptiles also have a 3-chambered heart like to the amphibian heart that directs blood to the pulmonary and systemic circuits, equally shown in Figure 21.4 c . The ventricle is divided more than effectively by a fractional septum, which results in less mixing of oxygenated and deoxygenated blood. Some reptiles (alligators and crocodiles) are the most primitive animals to exhibit a iv-chambered heart. Crocodilians have a unique circulatory mechanism where the center shunts blood from the lungs toward the tummy and other organs during long periods of submergence, for instance, while the animal waits for casualty or stays underwater waiting for casualty to rot. One adaptation includes two chief arteries that get out the aforementioned part of the centre: ane takes blood to the lungs and the other provides an alternate route to the tum and other parts of the body. Ii other adaptations include a pigsty in the heart between the two ventricles, called the foramen of Panizza, which allows blood to motion from ane side of the eye to the other, and specialized connective tissue that slows the claret menstruum to the lungs. Together these adaptations have made crocodiles and alligators i of the well-nigh evolutionarily successful animal groups on earth.

In mammals and birds, the centre is as well divided into iv chambers: two atria and two ventricles, every bit illustrated in Figure 21.4 d . The oxygenated blood is separated from the deoxygenated blood, which improves the efficiency of double circulation and is probably required for the warm-blooded lifestyle of mammals and birds. The four-chambered heart of birds and mammals evolved independently from a three-chambered eye. The independent evolution of the same or a similar biological trait is referred to as convergent evolution.

Summary

In virtually animals, the circulatory organization is used to transport blood through the torso. Some primitive animals apply diffusion for the exchange of h2o, nutrients, and gases. Nonetheless, complex organisms use the circulatory arrangement to carry gases, nutrients, and waste through the body. Circulatory systems may be open (mixed with the interstitial fluid) or airtight (separated from the interstitial fluid). Closed circulatory systems are a characteristic of vertebrates; nonetheless, there are significant differences in the structure of the heart and the circulation of blood between the different vertebrate groups due to adaptions during evolution and associated differences in beefcake. Fish take a ii-chambered center with unidirectional circulation. Amphibians have a three-chambered heart, which has some mixing of the blood, and they have double apportionment. Most non-avian reptiles accept a 3-chambered centre, just have lilliputian mixing of the claret; they take double circulation. Mammals and birds have a four-chambered center with no mixing of the blood and double circulation.

Exercises

Which of the following statements about the circulatory organisation is false?
1. Blood in the pulmonary vein is deoxygenated.
2. Blood in the inferior vena cava is deoxygenated.
3. Blood in the pulmonary artery is deoxygenated.
4. Blood in the aorta is oxygenated.
Which of the post-obit statements nigh the heart is false?
1. The mitral valve separates the left ventricle from the left atrium.
2. Claret travels through the bicuspid valve to the left atrium.
3. Both the aortic and the pulmonary valves are semilunar valves.
4. The mitral valve is an atrioventricular valve.
Varicose veins are veins that go enlarged because the valves no longer shut properly, allowing blood to flow astern. Varicose veins are often most prominent on the legs. Why do yous think this is the example?
Why are open circulatory systems advantageous to some animals?
1. They use less metabolic energy.
2. They assistance the animal move faster.
3. They do non demand a heart.
4. They help large insects develop.
Some animals apply diffusion instead of a circulatory organisation. Examples include:
1. birds and jellyfish
2. flatworms and arthropods
3. mollusks and jellyfish
4. None of the above
Blood flow that is directed through the lungs and dorsum to the heart is called ________.
1. unidirectional circulation
2. gill circulation
3. pulmonary circulation
4. pulmocutaneous circulation
Describe a closed circulatory arrangement.
Depict systemic apportionment.

Answers

C
B
Blood in the legs is farthest away from the heart and has to flow up to reach it.
A
D
C
A closed circulatory system is a closed-loop system, in which blood is non free in a crenel. Blood is separate from the actual interstitial fluid and independent within blood vessels. In this blazon of system, blood circulates unidirectionally from the heart effectually the systemic circulatory road, and and then returns to the centre.
Systemic circulation flows through the systems of the body. The blood flows away from the heart to the brain, liver, kidneys, tum, and other organs, the limbs, and the muscles of the body; it and then returns to the heart.

Glossary

atrium: (plural: atria) bedchamber of the eye that receives claret from the veins and sends claret to the ventricles
closed circulatory organization: organisation in which the blood is separated from the bodily interstitial fluid and contained in blood vessels
double circulation: catamenia of blood in ii circuits: the pulmonary circuit through the lungs and the systemic circuit through the organs and body
gill apportionment: circulatory organisation that is specific to animals with gills for gas substitution; the blood flows through the gills for oxygenation
hemocoel: cavity into which blood is pumped in an open circulatory organization
hemolymph: mixture of blood and interstitial fluid that is found in insects and other arthropods every bit well as virtually mollusks
interstitial fluid: fluid between cells
ostium: (plural: ostia) holes between blood vessels that allow the movement of hemolymph through the torso of insects, arthropods, and mollusks with open circulatory systems
pulmonary circulation: menstruation of claret abroad from the heart through the lungs where oxygenation occurs and and so returns to the heart again
systemic apportionment: menstruation of blood away from the heart to the encephalon, liver, kidneys, stomach, and other organs, the limbs, and the muscles of the body, so the return of this blood to the heart
unidirectional circulation: flow of blood in a single circuit; occurs in fish where the blood flows through the gills, then past the organs and the rest of the torso, before returning to the center
ventricle: (center) large inferior chamber of the heart that pumps blood into arteries