Mammal Circulatory System- Some Info
It is believed that mammals first appeared in the Jurassic period which is around 200 million years ago. They are said to have evolved from a reptile group, therapsids. Over time, they diverged in to diverse forms with different habitats and adaptations. One of the oldest mammals groups alive today is monotremes, mammals that lay eggs. The most diverse group is rodents having around 1700 species. Other mammal groups with diverse number of species are primates, marsupials, bats and insectivores. Aardvark, lemurs, manatees and dugongs include fewest species.
One of the important adaption of mammals is their efficient and effective circulatory system. Like any vertebrate, they have a heart that undergoes repeated contractions in order to distribute blood all over the body through blood vessels. The blood contains oxygen which is required for the proper functioning of body cells. All the nutrients from food are absorbed into blood which is then supplied to the cells. It also functions in removing toxins and chemicals in the body.
Heart consists of chambers which differ for different animal groups. In general, the number of chambers ranges from two to four. The types of chambers are two, namely atria and ventricles. The impure blood reaches the heart through atria and the ventricles carry pure blood from the heart to different parts of the body. Mammals have four chambered heart. It consists of two atria and two ventricles. All other vertebrates like reptiles and amphibians have two chambered or three chambered heart.
A four chambered structure separates the oxygenated blood and deoxygenated blood, thereby preventing the mixing up of pure and impure blood. This enhances a sustained growth and helps in regulating their body temperature making the mammal circulatory system efficient. There is no wonder that mammals are a more advanced group in the animal Kingdom.