Why are the muscles of chickens and fish red and white?

It should be explained that the factors that affect the ratio of red and white muscles are both congenital and acquired. The original chicken can fly, but it will not fly for a long time when it is only "rushing" when it is running away from the enemy. The judgment that "chickens rarely use the muscles to fly" refers not only to the fact that they are bred in captivity and do not need to fly, but also to the fact that they have accumulated genes that encode "muscles that are not good at flying for long periods of time" throughout the evolutionary history of the species.

The ancestors of ducks are migratory birds, and they are very good at endurance flight, although ducks in captivity cannot fly, but it retains the genes of its ancestors, so it also does not fly, ducks still have more myoglobin than chickens, and the color of the breast is also darker. <>

01 Because skeletal muscle has two types of muscle cells. A type of myocyte that supplies more oxygen to the blood, myoglobin, and the muscles made up of this muscle cell are light red in color and are called red muscles. Another type of myocyte has less myoglobin and less blood**, so the muscles that make up it are white and called white muscles.

Both muscles are found in birds and fish, but they vary in location and number.

At the dinner table, when you pick up two pieces of white chopped chicken or steamed fish, you will often find that some muscles are light red and some are grayish-white. The light red muscles are more delicate, while the grayish-white muscles are rougher.

Why do the muscles of the same individual have different colors? This is analyzed in terms of the tissue structure, composition, and physiological function of the muscles.

A muscle is made up of many muscle cells. Skeletal muscle has two types of muscle cells. One type of muscle cell is smaller, contains more sarcoplasm, and has fewer myofibrils; In terms of ingredients, there is more myoglobin, more fat, and less muscle glycogen.

The metabolism of this muscle cell is aerobic metabolism, which can maintain contraction for a long time, and its fat and muscle glycogen are fully oxidized and decomposed into water and carbon dioxide, which is not easy to fatigue. Because myoglobin and blood supply more oxygen, the muscles made up of these muscle cells are light red in color and are called red muscles. The other type has larger muscle cells, less sarcoplasm, and more myofibrils; Low in myoglobin and fat, and high in myoglycogen.

This muscle cell can be anaerobically metabolized, and the contraction is fast and powerful, but because fat and muscle glycogen are not fully oxidized to water and carbon dioxide, there are often intermediate products such as lactic acid and pyruvate phosphate accumulation, which is easy to fatigue, so it cannot maintain contraction for a long time. Because this myocyte has less myoglobin and less blood**, the muscles that make up it are white and called white muscles. Both muscles are found in birds and fish, but they vary in location and number.

Chickens are not good at flying, the ancestors were protochickens, and after domestication, they lost their ability to fly. They spend most of their time on the ground walking with their hind limbs supported by their bodies. Therefore, the red muscles of chickens are mostly concentrated in the legs, and the pectoral muscles and other parts are white muscles.

Birds that are good at flying, such as domestic pigeons and other migratory birds, have red muscles, which can continuously contract in the air, agitate their wings, and propel their bodies forward.

Fish also have a distinction between red and white muscles. Fish that swim constantly with their bodies bent in the water, such as tuna, mackerel, porking sharks and mako sharks, have more developed trunk red muscles. Slow-moving, benthic or reef-dwelling fish, such as carp, have mostly white muscles or only some red muscles on their trunks.

Red and white muscles work together to swim.

In the skeletal muscles of some animals and humans, white muscle cells and red muscle cells are mixed to form one muscle, but there is no obvious distinction between white and red muscles.