Heart! Trivia Quiz

Answer: Jellyfish

Single-celled animals, such as the amoeba and paramecium, do not have any way of establishing a circulatory system, which requires multiple cells. Jellies (the preferred term at the moment, since they are not fish) have plenty of cells, but they maintain the supply of nutrients for cells and remove waste products through the process of diffusion. Since there are two layers of cells, each cell is in contact with the surrounding water, and can maintain the appropriate balance of materials inside itself through diffusion.

There is no need for a system to transport nutrients and waste around its body. Some other simple animals, such as flatworms, also exchange materials with their environment by means of diffusion. More complex animals, including insects such as the butterfly, have a circulatory system which includes some type of heart.

Answer: Pericardium

The pericardium (a term that means 'around heart', from Latin roots) is usually an independent structure, but can sometimes be part of the peritoneum, the membrane that lines the abdominal cavity. It has two primary layers: the outer layer is fibrous, made of tough connective tissue, while the inner layer is serous, and is itself divided into two layers, the parietal layer (near the fibrous layer) and the visceral layer.

The pericardial cavity, the area between them, is filled with serous fluid that acts like a shock absorber to protect the heart from physical shocks.

Answer: In a linear sequence, although often spatially coiled

The blood enters a fish's heart through the sinus venosus, where blood is collected from the various parts of its body before proceeding to the two true chambers. It then leaves the heart through the outflow tract and proceeds to the gills, where it becomes oxygenated before proceeding around the body to other cells.

In an adult fish, the four compartments do not lie in a straight line, but coil into an S-shaped arrangement.

Answer: Atrium

The word atrium comes from the Latin word for a room through which one entered a house. The atria have thinner walls than the more muscular ventricles, since they only need to collect blood and let it pass through. Contractions of the ventricles is what pushes the blood out again, to travel either to the lungs (where it gains oxygen and loses carbon dioxide) or to the rest of the body (where it loses oxygen, and gains carbon dioxide and other waste products of metabolism, which it transports to the appropriate organs for removal from the blood).

In some regions, the atrium is called the auricle (but not the oracle).

Answer: Two atria, one ventricle

The sinus venosus (not considered a chamber, although it is relatively large) collects blood from the body via the venae cavae, and feeds it into the right atrium. The pulmonary vein (from the lungs) goes into the left atrium. The blood then moves from each atrium to the ventricle, which pushes it out again through blood vessels that branch to go to both the lungs and the rest of the body. Amphibians are said to have a double circulatory system, since there are two separate branches which return to the heart independently, but the two branches are not completely independent, since there is mixing of their contents inside the heart.

Answer: True

Crocodiles (and other crocodilians, such as alligators) have several adaptations that allow this useful diversion of their circulation. One is a small opening that connects their two ventricles, called the foramen of Panizza, which allows blood to move between the two sides of the heart.

They also have two arteries from the same side of the heart, one of which takes blood to the lungs, while the other sends it to the rest of the body. Along with some specialized connective tissue that can act to slow blood flow to the lungs, these adaptations make crocodiles efficient at lurking underwater for long periods of time.

Answer: True

Blood from the lungs enters the left atrium, the upper chamber on the left side of the heart, then moves to the left ventricle, which forces it out through the aorta to proceed to the rest of the body. The blood returns from this circuit by means of the vena cava to the right atrium, then goes to the right ventricle, and is sent out to the lungs.

Answer: Valves

The aortic and pulmonary valves are located at the points where the blood exits the heart to travel through the arteries of the same names. The bicuspid valve, also called the mitral valve because of a resemblance of its two flaps (bicuspid meaning two pointed) to the headdress called a mitre which is worn by bishops, keeps blood moving from the left atrium through to the left ventricle.

The corresponding valve on the right side of the heart is called the tricuspid valve - as its name suggests, it is made up of three flaps.

Answer: Blue-green

The chemical haemocyanin replaces the iron-based haemoglobin found in vertebrate red blood cells as the molecule to which oxygen is attached to be transported around the animal's body. Like many copper compounds, it assumes a blue-green color when combined with oxygen. Deoxygenated haemolymph is grey.

In many arthropods, including most insects, the haemolymph is not actually used for oxygen transport, since the animals gain oxygen directly through their body surface, but it still needs to circulate to carry nutrients to the body cells.

The circulatory system of arthropods is called an open circulatory system, since the liquid fills the entire body, and is not restricted to being contained in specific vessels. The heart is simple - usually, it is just a muscular tube running the length of the body (along the back) from head to tail which contracts to keep the haemolymph moving around.

Answer: Cephalopoda, such as an octopus

Cephalopods (octopuses, squid and cuttlefish) are the only members of the mollusc phylum to have a closed circulatory system, rather than an open one. They have one main heart, which pumps blood through the system, and two small branchial hearts, located at the base of the gills, which give the blood extra impulse to pass through the gills and collect oxygen.

As is the case for most molluscs, cephalopods use haemocyanin to transport oxygen, so their blood is clear when deoxygenated, and blue-green when oxygenated.