Question

How are amphibian circulatory and respiratory systems adapted to aquatic environments? Compare amphibian respiratory and circulatory system structure to human respiratory and circulatory system structures.

Answer 1

• In amphibians blood flow is directed in two circuits: one through the lungs and back to the heart, which is called pulmonary circulation, and the other throughout the rest of the body and its organs including the brain (systemic circulation). In amphibians, the gas exchange also occurs through the skin during pulmonary circulation and is referred to as pulmocutaneous circulation. amphibians have a three-chambered heart that has two atria and one ventricle. The two atria (superior heart chambers) receive blood from the two different circuits (the lungs and the systems), and then there is some mixing of the blood in the heart’s ventricle (inferior heart chamber), which reduces the efficiency of oxygenation. The advantage of this arrangement is that high pressure in the vessels pushes blood to the lungs and body. The mixing is mitigated by a ridge within the ventricle that diverts oxygen-rich blood through the systemic circulatory system and deoxygenated blood to the pulmocutaneous circuit. For this reason, amphibians are often described as having double circulation.

• Amphibians have evolved multiple ways of breathing. Young amphibians, like tadpoles, use gills to breathe, and they do not leave the water. As the tadpole grows, the gills disappear and lungs grow. A large surface area to allow as much oxygen to enter the gills as possible because more of the gas comes into contact with the membrane. he other means of breathing for amphibians is diffusion across the skin. To aid this diffusion, amphibian skin must remain moist. It has vascular tissues to make this gaseous exchange possible. This moist skin interface can be a detriment on land but works well underwater.

COMPARISION OF amphibian respiratory and circulatory system structure to human respiratory and circulatory system structures

Circulatory System

Amphibians

• Most have three chambers; two atria and one ventricle.
• The ridge in the ventricle takes most of the oxygen-poor blood from the right atrium to the pulmocutaneous circuit and most of the oxygen-rich blood from the left atrium to the systemic circuit
• When the amphibian submerges in water, they shut off their blood flow to their lungs and continues blood flow to the skin for gas exchange.

Humans

• Have two atria and two completely divided ventricles. The left side of the heart pumps and receives only oxygen-rich blood while the right side of the heart pumps and receives only oxygen-poor blood.
• Humans have typically bigger and take up more energy so their circulatory systems need to deliver more oxygen to their tissues. Humans can do this by their separate and independent systemic and pulmonary circuits.

Respiratory System

Amphibians

Adult amphibians are lung-breathers. The skin acts as an accessory respiratory organ both in water and on land. The skin is highly vascular and specially so in the buccopharyn­geal cavity.

Few urodeles retain external gills as the respiratory organs in adults.

Both external and internal gills are pre­sent in anuran larvae. Ascaphus, living in the mountain stream of U.S.A., has reduced lungs which help the animal to live in water.

In almost all amphi­bians cutaneous respiration is a remarkable supplementary respiratory adaptation.

In caecilians, the tracheal lung may be present but the left one is always rudi­mentary. In aquatic urodeles, the lungs act secondarily as hydrostatic organ. In all these above cases, respiration is exclusively pharyn­geal and/or cutaneous.

Humans

The primary organs of the respiratory system are the lungs, which carry out this exchange of gases as we breathe

As we breathe, oxygen enters the nose or mouth and passes the sinuses, which are hollow spaces in the skull that help regulate the temperature and humidity of the air we breathe.

The alveolar walls are extremely thin (about 0.2 micrometers) and are composed of a single layer of tissues called epithelial cells and tiny blood vessels called pulmonary capillaries. Blood in the capillaries picks up oxygen and drops off carbon dioxide.

The diaphragm, a dome-shaped muscle at the bottom of the lungs, controls breathing and separates the chest cavity from the abdominal cavity.