Mammals are animals that feed their young with milk. They are the most highly organized. The excretory, reproductive, digestive, respiratory and circulatory systems of mammals are the most complex in comparison with representatives of other systematic units. But special attention should be paid to the structure of the digestive system.
Nutrition and digestion
Food is one of the main signs of living organisms. This process consists in the intake of substances into the body, their transformation and the removal of unprocessed food residues. In specialized organs, digestion occurs - the breakdown of complex organic substances (proteins, lipids, carbohydrates) into simple ones that can be absorbed into the blood. Why do biopolymers break down into their constituent parts? The fact is that their molecules are very large, and they cannot penetrate from the digestive channel into the bloodstream. Digestive systemmammals are no exception. It has a number of features that distinguish them from other chordates.
The structure of the digestive system of mammals
This organ system consists of two parts: the canal and the glands. In the first, food is digested, nutrients are absorbed into the blood, and its unprocessed residues go out. The alimentary canal includes the following sections: oral cavity, pharynx, esophagus, stomach, small and large intestines, ending in the anus. Through it, undigested residues are removed. Features of the structure of the digestive system of mammals are the presence of glands. These are special organs that contain enzymes - biological catalysts that contribute to the process of splitting biopolymers.
Features of digestion in the oral cavity
The organs of the digestive system of mammals, or rather the canal, begin with the oral cavity. The cheeks and lips form the preoral cavity. This is where two types of food processing take place. Mechanical is carried out with the help of differentiated teeth and tongue, chemical - enzymes of the salivary glands. Here they break down only one type of organic matter - complex carbohydrates polysaccharides to simple, monosaccharides.
Differentiation of teeth depends on the type of food and how it is obtained. Carnivores have the most developed incisors, herbivores have flattened molars, and whales have no teeth at all.
Digestion in the stomach
The food bolus from the oral cavity through the esophagus moves into the stomach - the most expanded part of the entire canal. Its muscle walls begin to contract, and the food is mixed. Here it is subjected to chemical treatment. The digestive and circulatory systems of mammals are closely interconnected. Gastric juice breaks down proteins and lipids into monomers - constituent parts. Only in this form will they enter the bloodstream.
Digestion in the gut
The digestive system of mammals continues with the intestines: thin and thick. Partially digested food in the stomach in small portions enters its first section. Here the final breakdown and absorption of substances into the blood and lymph occurs. The first section of the small intestine is called the duodenum. The ducts of the pancreas and liver open into it. The large intestine is the final section of the digestive system. Here most of the water is absorbed and feces are formed, reflexively removed from the rectum.
Digestive glands
The digestive system of mammals is characterized by the presence of glands. These are the organs in which enzymes are located. There are three pairs of salivary glands in the oral cavity. They secrete a colorless mucous substance. The composition of saliva includes water, the enzymes amylase and m altase, and mucus mucin. Each of them performs its function. Water wets food, lysozymeneutralizes microorganisms and heals wounds, amylase and m altase breaks down carbohydrates, mucin has an enveloping effect.
The gastric juice contains hydrochloric acid, which delays putrefactive processes and stimulates physical activity. Additional substances are the enzymes pepsin and lipase, which, respectively, break down proteins and lipids. Hydrochloric acid is a chemically active substance, it is able to corrode the gastric mucosa. It is protected from this action by mucus (mucin).
The pancreas produces digestive juice consisting of the enzymes trypsin, lipase and amylase. They finally break down all organic matter.
The role of the liver is also great. It constantly produces bile. Once in the small intestine, it emulsifies fats. The essence of this process is the breakdown of these biopolymers into small droplets. In this form, they are quickly broken down and absorbed by the body. Activation of enzymes, increased intestinal motility, stopping putrefactive processes are also functions of the liver.
What are enzymes
And now more about the nature and mechanism of action of enzymes. As biological catalysts, they speed up chemical reactions. The mammalian digestive tract is essentially just a site for enzymes to act.
Features of nutrition of mammals
The totality of chemical transformations of substances from the moment they enter the body to excretion is called metabolism. This is a necessary condition for the growth, development and simply existence of any living organism. Different groups of mammals have adapted to foraging in different ways. Predators attack weaker animals. To do this, they have well-developed teeth, namely incisors and canines. There are also many herbivorous and insectivorous species. Ruminants are of particular interest. Their digestive system is especially complex. The incisors are completely absent from above, they are replaced by a transverse tooth roller, and the canines are underdeveloped. This structure of the teeth is necessary to chew grass - chewing gum. Giraffes, cows and deer are typical representatives of this group of animals. Their stomach consists of four sections. They are called scar, mesh, book, abomasum. In the first two, chewed food breaks down into solid and liquid parts. The gum is regurgitated from the stomach back into the mouth and chewed again. Then the already carefully processed food immediately enters the third section - the book, and from there - into the abomasum. In this last section, it is already exposed to the action of gastric juice and finally splits.
Non-ruminant animals such as wild boars, pigs and hippos have simple single-chamber stomachs and a standard digestive system.
Some mammals use their limbs to grab food. So, the elephant puts food in his mouth with the help of his trunk. And nectar-eating bats have a flattened snout and brush-shaped tongue. There is also a special device for food storage. Many rodents store grains in their cheek pouches.
The digestive system of mammals has a complex structure, the features of which depend on the nature of the food and the habitat of the animals.
