Animal organs, organ systems: definition, examples
A living organism is a whole system ofbetween themselves organs and tissues. Thanks to their well-coordinated work, the animal can function normally. And it is not important at what stage of development is the body. The only difference is that representatives of the fauna can be at different stages of evolution, and therefore, the organs of animals, organ systems also differ in terms of structure and work. This is the basis of the principle of phylogenesis.
Structure of animal organs
Most organs have a common structure: connective tissue membrane, muscle layer and inner layer. Depending on work and functions, these layers can be well developed, absent or supplemented with other sites.
Not all animals have organs. For example, coelenterates and sponges, flat worms are still at the tissue level of the organization.
Biology. Animal organs systems
Originally, the body of organisms consisted ofdifferentiated cells. In the process of evolution, animal organs and organ systems were formed. They differ in functions, but their work is aimed only at one thing - maintaining the constancy of the internal environment of the body and normal life activity.
The following systems of organs are distinguished:
1. The circulatory.
2. Digestive.
3. Musculoskeletal.
4. Exclusive.
5. Respiratory.
6. Endocrine.
7. Nervous.
8. Sexual.
9. The system of sense organs.
Animal circulatory system
The circulatory system first appears inringed worms, and they have a closed type. The two main vessels are the dorsal and the ventral. They are connected in the front part of the body of the worm by powerful channels, which are trivially called "hearts," but these are not separate organs, but ordinary vessels whose walls contain a thick layer of muscle tissue.
Further evolution of the organs was as follows:
- in all types of animals to molluscs inclusive, the circulatory system is not closed;
- the system is of a closed type, but there is still no heart;
- beginning with the cyclostomes (myxins, lampreys), a two-chambered heart appears;
- amphibians and reptiles have a three-chambered heart, the blood is mixed;
- birds and mammals have a 4-chambered heart, so they can maintain a constant body temperature (homoiothermal organisms).
Digestive system
The digestive system is first described in flatworms (in the form of closed channels). There is no anal opening. Subsequently, the internal organs of animals evolved as follows:
- Round worms have a through intestinal tube: the hindgut and anus (in the flat there were only two sections of the intestine);
- ringed worms form calcium salivary glands, whose task is the decomposition of detritus;
- in arthropods, the anterior and middle intestines are lined with chitinous covers;
- the lancelet has hepatic growth;
- in cartilaginous fish - a spiral valve in the small intestine, its function is to increase the suction surface;
- further evolution went on lengthening of the intestine, and accordingly, to increase the area of absorption.
Musculoskeletal system
The musculoskeletal system consists of twosystems: the skeleton and muscles. The skeleton plays the role of a support, and the muscles are responsible for movement in space. The evolution of the latter went on a great differentiation and reduction of the metameric arrangement.
- The skeleton appears in the cyclostomes.
- In cartilaginous fish it is cartilaginous, in most bone fishes it is bony.
- With the emergence of land on amphibians appear five-fingered limbs, develop bones of free limbs and there are new departments of the spine.
- Reptiles form a thorax.
- The birds have a lot of changes in the structure of the skeleton in connection with the adaptation to the flight.
- In mammals there is a final differentiation of bones.
Excretory system
What are the animal organs? The organ systems also include a excretory system that is responsible for removing metabolic products, toxins and poisons from the body.
- In the case of flatworms, the excretory system is represented by protonephridia.
"Ringworms are already metanephridia."
- Arthropods have green glands, Malpighian vessels.
"The shellfish have a kidney."
- In all subsequent types (before fish) head buds.
- Fish and amphibians have trunk kidneys.
In all, from reptiles to mammals, these functions are performed by pelvic kidneys.
Respiratory system
Performs the function of assimilating oxygen from the environment. It first appears in arthropods.
- In crustaceans, the respiratory system is represented by gills.
- Insects have trachea.
- Molluscs - light, formed by the mantle cavity.
- In all animals before the fish inclusive, respiratory organs are the gills.
- Frogs have bag-shaped lungs.
- Reptiles have honeycombs.
"Birds are spongy."
- Mammals have alveolar lungs.
Nervous system
The nervous system connects the remaining systems of organs to a single organism, giving signals and regulating the work of each site.
The diffuse type nervous system appears in the coelenterates.
- Flatworms have orthogonas, or a nervous system of a ladder type.
- Round worms have an oclo-spinal nerve ring and nerve trunks.
- Ringed worms have an okolo-gell nerve ring and an abdominal neural chain.
- Arthropods have a head ganglion and the abdominal neural chain remains.
- The mollusks have a nodal nervous system.
- In the cephalothorax, an extension of the neural tube appears at the anterior end of the body.
- In fish, all parts of the brain are isolated.
Next, the reptiles appear rudiments of the cortex of the cerebral hemispheres.
In mammals there are convolutions of the brain.
Sexual system
Reproductive system function - reproductiontheir own kind. The reproductive system can be female or male, there are hermaphrodites (annelids, mollusks). The female system developed gradually. The main organs are the uterus, fallopian tubes, ovaries. Many parasitic worms also have an ootype and additional glands: proteinaceous, yolk.
The male reproductive system consists of the testes and the vas deferens. Further, spermatozoa are ejected through the copulatory organ to the outside or into the sexual organs of the female.
Conclusion
We examined what animal organs are. Systems of organs play an important role in maintaining the normal vital activity of absolutely any individual, whether it be worms or humans. If each of the systems works correctly, the body's homeostasis is maintained.
Children in biology classes study the structure of livingorganisms. Visual material allows you to better remember how the organs of animals look. Tables of different systems can be found in almost any biology classroom.
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