Gaseous Exchane & Tansport In Animals

Deoxygenated blood refers to blood that has no oxygen. This blood has already delivered its oxygen to the body tissues and is returning to the heart and lungs to be reoxygenated. It is typically darker in color, such as a deep red or maroon, compared to oxygenated blood. This distinction is important as oxygenated blood is necessary for the body's vital functions, while deoxygenated blood carries waste products like carbon dioxide.

Oxygenated blood is red in color because it contains a high concentration of oxygen-bound hemoglobin. Hemoglobin is a protein in red blood cells that binds to oxygen molecules, giving blood its red color. Oxygenated blood is typically bright red and is found in arteries, which carry oxygen from the lungs to the body's tissues.

Capillary walls are composed of a single layer of cells because capillaries are the smallest blood vessels in the body and their walls are thin to allow for the exchange of gases, nutrients, and waste products between the blood and surrounding tissues. This single layer of cells, called endothelial cells, allows for easy diffusion of substances and ensures efficient exchange. Multiple layers of cells would hinder this process and make it less effective. Therefore, the statement that capillary walls are composed of a single layer of cells is true.

When thinking about breathing, the gas that is not commonly talked about is hydrogen. This is because hydrogen is not a major component of the air we breathe. Oxygen is the primary gas that we inhale and is essential for our survival. Carbon dioxide is the waste gas that we exhale. While hydrogen can be found in small amounts in the atmosphere, it is not typically discussed in relation to breathing.

Veins actually carry blood at low pressure and carry blood towards the heart. However, they do have valves that prevent the backflow of blood and ensure that it flows in one direction. Therefore, the statement that veins have no valves is incorrect.

The option "take blood to the heart" does not refer to arteries because arteries carry blood away from the heart to various parts of the body, not towards the heart. The other options, such as "lie deep within the body," "high blood pressure," and "thick elastic walls," are characteristics or functions associated with arteries.

Leucocytes, also known as white blood cells, are a type of blood cell that plays a crucial role in the immune system. They help to fight off infections and diseases. Phagocytes are a type of leucocyte that engulf and destroy foreign particles and bacteria. Lymphocytes are another type of leucocyte that are responsible for producing antibodies and coordinating the immune response. Therefore, both phagocytes and lymphocytes fall under the category of leucocytes.