38 - Chapter 38 Circulation Respiration and Excretion in...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 38. Circulation, Respiration, and Excretion in Chickens The comparable life support systems of birds will be described briefly using the domestic chicken as the type species. In general, the requirements of these systems are similar to those for mammals, but considerable structural specialization has attended their evolution. A. Cardiovascular The blood of chickens contains relatively few erythrocytes (about half the concentration found in mammals), the cells are smaller, they retain their nuclei, and they are not biconcave disks. Circulating erythrocytes are capable of continued synthesis of hemoglobin. The lymphocyte is the dominant leukocyte and there are no platelets because thrombocytes are present as intact cells and are not fragmented as in the case of mammals. Blood cell formation is confined to the sparse amount of marrow found in just a few of the bones, as noted in Chapter 7, Section B. Chickens lack definitive lymph nodes equivalent to those of mammals, but there are specialized lymphoid tissues associated with the digestive tract (described later in Chapter 48). Chickens have a high metabolic rate and, because of the low oxygen carrying capacity of the blood, the needs of tissues are met by the cardiovascular system operating at a higher rate of performance than is typical for mammals. High perfusion rates are sustained by increased arterial pressure resulting from elevated cardiac output and, in turn, from elevated heart rate (see Figure 34-1).
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern