척추 동물

신경계 및 감각 기관

중추 신경계의 등쪽 위치, 관형 구조 및 표피 기원은 chordates를 결정하지만, 일부는 hemichordates와 유사성을 볼 수 있습니다. 감각 구조는 화구를 구별하며 한 쌍의 코, 시신 및 귀 기관 (강하게 분화 된 머리와 함께)을 포함합니다.

chordate: 일반 기능

척추 동물 은 작은 물고기부터 고래에 이르기까지 크기가 다양하며 여기에는 지금까지 존재 한 가장 큰 동물이 포함됩니다.

비소는 환경에 다양하게 개방되어 있으며, 화학 수용체로서의 감각 세포는 입안의 입안에있는 것과 다릅니다. 눈은 머리의 가장 복잡한 기관이며 뇌관의 앞쪽 끝의 측면 아웃소싱입니다. 나중에 그것은 표피 기원의 렌즈를 얻습니다. 눈에 초점을 맞추는 행위 (숙박)는 척추 동물의 여러 그룹 사이에 광범위한 적응 적 변화를 보여줍니다.

귀 소포는 외배엽 기원 판의 침입에 의해 형성된 간단한 낭으로부터 시작된다. 이러한 발달 변화에는 또한 신경 분포의 변화도 포함됩니다. 원래의 구조는 기본적으로 평형 적응 이었지만, 움직임에 대한 인식 또는 먹이의 근접 감과 같은 다른 기능들이 개발되었습니다.

The lateral-line system of canals and sensory organs is a unique vertebrate feature. The elements of this system are found on the head as well as the body. This system is related to the ear and presumably at its origin served a similar function. This system is lost in terrestrial vertebrate forms.

The digestive system

The digestive system of the vertebrate is distinctive in its structure but not in its function. The mouth and pharynx can be considered as parts of this system; the latter as an expanded cavity in the head is unmatched in any other group. The stomach and gut have been discussed above.

Presumably the original condition of the digestive glands was that of a ventral diverticulum which may have received the food mass into its cavity. This diverticulum, matched by the diverticulum seen in the amphioxus or the “intestine” of the tunicate, produced the secretions (bilelike and enzymes) of both liver and pancreas. Through time, the liver gradually differentiated from the pancreas. The size and separation of the liver from the gut suggest its separate blood and metabolic activities. The most obvious by-product of the liver, bile, necessitated the formation of a gall bladder and a duct connection with the gut. The pancreas, in contrast, continued to produce digestive enzymes, but its secretory cells were no longer in direct contact with the food mass. Because the pancreas was only a partial source of intestinal digestive enzymes, it was sometimes reduced in size and enclosed in the gut wall itself (agnaths) or dispersed as tiny bits of tissue in the mesentary supporting the gut (actinopterygians).

The excretory system

The excretory system is unique in its nephrons, which filter the blood in the glomeruli and remove a variety of wastes from the body through selective secretion and reabsorption. In the shark or the coelacanth Latimeria, urea is used to raise the osmotic pressure of the blood to that of the marine habitat, thus saving these organisms considerable metabolic energy. The large intestine (sometimes centred in a rectal gland) acts as an auxiliary excretory organ, as do also the gills of fishes or the sweat glands of mammals.

Respiration and gas exchange

Respiration, like excretion, involves specialized body structures, such as lungs or gills, but also can involve other areas, such as the skin itself. Respiration involves exchange of gases both between the body of the organism and the environment and between the blood system and the body tissues. It also involves cellular respiration where oxygen is used and carbon dioxide is produced. There is nothing characteristic of the vertebrate in this functional area; even the hemoglobin of the blood is suggested in the respiratory pigments of other animals.

The circulatory system

The circulatory system of vertebrates is closed in that fluids course through vessels, but there is free movement of cells in and out of blood. Some leukocyte (white blood cell) movement out of the capillaries and fluid leakage are observed in all tissues. Blood tissues are distinctive in the range of specialized cells, although these vary in detail among animals. The immune function of the blood is best developed in the vertebrate.

The endocrine system

The endocrine system is characterized by its separate organs. The occurrence of a pituitary or a thyroid gland is suggestive of the evolutionary change and specialization that took place within this group. The relatively unspecialized nature of some parts of this system is seen in certain scattered cells in the gut wall or even the clumps of islet cells of the pancreas.