The internal structure of reptiles. Vital activity of reptiles

Reptiles are a highly organized class of vertebrate animals, which includes 9400 species that lead a terrestrial, less often semi-aquatic way of life. In this article, we will study the internal structure and activity of reptiles, and also consider some of their features associated with environmental adaptations.

Skeleton and Reptile Muscles

Unlike amphibians, the reptile spine has a more complex structure and consists of the cervical, thoracic, lumbar, sacral and caudal sections. The thoracic vertebrae are connected to the ribs and form the rib cage. It is absent in snakes, but their spine contains up to 500 vertebrae. The lizard, unlike snakes, has a well-developed chest, and the tail section of the spine has its own characteristics: the vertebrae of the tail section have a layer of cartilaginous tissue and they can easily be destroyed. This process is called autotomy. It has a protective value: the animal is saved from the teeth of the predator, losing part of the tail. The muscle system of reptiles is quite complex.

This applies primarily to the pectoral intercostal muscles involved in the breathing process. The mandibular muscles, as well as the muscles of the hind limbs in reptiles such as lizards and crocodiles, received significant development. The anatomically complex internal structure of reptiles (table below) is the result of aromorphoses and adaptations that have arisen in these organisms during evolution.

Circulatory system

Complications in the organization of reptiles also affected the cardiovascular system. Continuing to study the internal and external structure of reptiles, we dwell on its features and metabolic processes related to blood circulation. Metabolism in reptiles is less dependent on ambient temperature than amphibians. Nevertheless, reptiles, like amphibians, are poikilothermic organisms and their temperature optimum lies in the range - + 22- + 38 degrees. The energy consumption of reptiles is lower than that of amphibians. This is due to a complication of the structure of the heart, as well as a partial separation in it of the circulation of arterial and venous blood. The features of the internal structure of reptiles, the table of which is given below, indicate that reptiles have two circles of blood circulation. Their circulatory system is closed, in the heart there is an incomplete septum, which is completely overgrown with crocodiles, maintaining a hole between the left and right side.

The main organ of blood circulation consists of two atria and ventricle. Arterial blood is collected in the upper part of the ventricle, entering it from the left atrium, and venous from the right. Thus, in the lower right side of the ventricle, the blood mixes. During systole, oxygen-enriched blood is pushed into the right aortic arch. Mixed blood from the right side of the ventricle enters the left aortic arch, and venous blood from its lower half into the pulmonary artery. Although, considering the internal structure of reptiles, they talk about two circles of blood circulation, it must be taken into account that they cannot be considered independent, since arterial and venous blood mix in the spinal aorta.

Reptile Pelvic Kidneys

The internal structure of reptiles is characterized by a complication in the structure of one of the leading systems - excretory, which consists in the development of methanephros - pelvic kidneys. They are located on the ventral side of the pelvis on either side of the cloaca, connecting with it through the ureters. The bladder is also located there. In snakes and crocodiles, it is anatomically weakly expressed. Unlike mammals, reptile metabolism products do not contain urea, but uric acid.

How digestion occurs

Most reptiles are carnivores, although reptiles such as the fast lizard and the steppe tortoise also feed on plants. Studying the internal structure of reptiles, it becomes clear that the digestive tube has a number of morphological features associated with the general complication of the organization. So, they form a secondary palate. It is formed by bones and separates the oral cavity from the nasopharyngeal passages that open into the throat with funnel-shaped formations - secondary choanas. In the large intestine, for the first time, the cecum appears in reptiles. Digestive glands: the liver and pancreas produce enzymes, and bile emulsifies lipids. The walls of the esophagus and stomach are muscular and dense, which is especially important for species that swallow food whole (for example, snakes) or large pieces (crocodiles). The school biology textbooks studying the internal structure of reptiles (Grade 7) contain many interesting facts regarding the nutrition of reptiles. For example, crocodiles and turtles can do without food longer than any other vertebrate animals, starving for up to six months. For normal digestion in snakes, an ambient temperature of at least 22 - 25 ° C is necessary, otherwise the digestive glands cease to produce enzymes, and the food, swallowed whole, is not digested, but begins to rot in the stomach, which leads to poisoning and death of the animal.

Life cycle

Continuing to study the internal structure and life of reptiles, we consider the seasonal changes that occur in their ontogenesis. They are due to idioadaptation to temperature fluctuations (daily and seasonal cycles). For example, in mid-spring, reptiles lead an active lifestyle from noon, when the soil and air are warm enough.

In July - early August, most animals are most active in the morning or evening hours, and at noon they fall into a state of rest. In winter, reptiles of temperate latitudes hibernate, hiding in rock crevices, in burrows or under tree roots. Summer hibernation is characteristic of those species of reptiles that at this time of the year lack food.

Shedding at reptiles

The process of molting occurs cyclically in animals - the change of dry skin covered with shields or horny scales. It also depends on the temperature of the environment. Snakes and lizards have full molt, in this case the entire skin, called the creep, changes. In crocodiles, individual scales are periodically sloughed - osteoderm. In land turtles, areas of the skin that are not protected by carapace are exfoliated, and in aquatic shedding, molting is hardly noticeable.

Breeding reptiles

The reproductive function, which is also regulated by the temperature of the external environment, also belongs to cyclic processes in the life of animals. Pay attention to the features of the internal structure of reptiles. The table below confirms the fact that reptiles are dioecious animals, which are characterized by internal fertilization.

After it, the females lay eggs covered in lizards, turtles and snakes with a leathery shell, and in crocodiles it is calcareous. Some reptiles, such as the common viper, carry eggs inside the body. Up to 12 cubs are born who immediately begin to molt. The reproductive system of males is represented by paired testes, vas deferens and the wolf channel, which flows into the cloaca. Females have paired ovaries. Oviducts having funnel-shaped openings also enter the cloaca.

Nervous system and sensory organs

The internal structure of reptiles will be incomplete without studying the innervation of the organs and functions of the analyzers. The brain has a complex structure.

Associative centers of the cortex provide the development of a system of conditioned reflexes. The organs of vision, hearing, smell, touch are well developed. Snakes and some lizards, for example, hatteria, have a parietal eye, which is a photosensitive organ.