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 most complex compared to representatives of other systematic units. But special attention needs to be paid to the structure of the digestive system.
Nutrition and Digestion
Nutrition is one of the main signs of living organisms. This process consists in the entry into the body of substances, their transformation and removal of unprocessed food residues. Digestion occurs in specialized organs - the breakdown of complex organic substances (proteins, lipids, carbohydrates) into simple ones that can be absorbed into the blood. Why should biopolymers fall apart? The fact is that their molecules are very large, and they cannot penetrate from the digestive canal into the bloodstream. The digestive system of mammals is no exception. It has a number of features that distinguish them from other chordates.
The structure of the digestive system of mammals
This system of organs consists of two parts: the channel and glands. In the first, food is digested, nutrients are absorbed into the bloodstream, and its unprocessed residues go out. The digestive canal includes the following departments: the oral cavity, pharynx, esophagus, stomach, small and large intestines, ending in the anus. Through it, undigested residues are removed. The structural features of the digestive system of mammals are also in the presence of glands. These are special organs in which enzymes are located - biological catalysts that contribute to the process of cleavage of 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. Cheeks and lips form a pre-oral cavity. This is where two types of food processing take place. Mechanical is carried out using differentiated teeth and tongue, chemical - enzymes of the salivary glands. Here they break down only one type of organic substance - complex carbohydrates polysaccharides to simple monosaccharides.
Differentiation of teeth depends on the type of food and the method of extraction. Incisors are most developed in predators, flat-shaped molars are typical for herbivores, and whales have no teeth at all.
Digestion in the stomach
The food lump 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 mixes. Here she is also subjected to chemical treatment. The digestive, circulatory system of mammals is closely interconnected. Gastric juice breaks down proteins and lipids into monomers - components. Only in this form will they enter the bloodstream.
Intestinal digestion
The mammalian digestive system continues with the intestines: thin and thick. Partially digested food in small portions enters the stomach. 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 that are reflexively removed from the rectum.
Digestive glands
The mammalian digestive system is characterized by the presence of glands. These are the organs in which the enzymes are located. Three pairs of salivary glands are located in the oral cavity . They secrete a colorless mucous substance. Saliva contains water, amylase and maltase enzymes, and mucin mucus. Each of them performs its function. Water moistens food, lysozyme neutralizes microorganisms and heals wounds, amylase and maltase breaks down carbohydrates, mucin has an enveloping effect.
The composition of the gastric juice includes hydrochloric acid, which delays putrefactive processes and stimulates motor 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. From this action, it is protected by mucus (mucin).
The pancreas produces digestive juice consisting of the enzymes trypsin, lipase, and amylase. They finally break down all organic matter.
Great is the role of the liver. It constantly forms 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 faster cleaved and absorbed by the body. Activation of enzymes, increased intestinal locomotor activity, stopping putrefactive processes are also liver functions.
What are enzymes
And now more about the nature and mechanism of action of enzymes. Being biological catalysts, they accelerate chemical reactions. The digestive tract of mammals is essentially just the site of action of enzymes.
Features of the nutrition of mammals
The set 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 differently adapted to the extraction of food. Predators attack weaker animals. To do this, they have well-developed teeth, namely incisors and fangs. There are also many herbivorous and insectivorous species. Of particular interest are ruminants. Their digestive system is particularly complex. The incisors from above are completely absent, they are replaced by a transverse tooth roller, and the fangs are underdeveloped. Such a tooth structure 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 tripe, net, book, abomasum. In the first two, chewed food breaks down into solid and liquid parts. Chewing gum burps from the stomach back into the oral cavity and is chewed again. Then, carefully processed food immediately falls into the third section - the book, and from there - into the abomasum. In this last section, it is already exposed to gastric juice and is finally broken down.
Non-ruminant animals, such as wild boars, pigs and hippos, have a simple single-chamber stomach and a standard digestive system.
Some mammals use limbs to grab food. So, an elephant places food in its mouth with the help of a trunk. And bats that feed on nectar have a flattened muzzle and tongue in the shape of a brush. There is a special adaptation for the supply of food. Many rodents store grains in cheek pouches.
The digestive system of mammals has a complex structure, the features of which depend on the nature of food and the habitat of animals.