Avian circulatory system

veterinary physiology

1. Avian Circulatory System DR suthar

2. introduction Birds have evolved high performance Cardiovascular system Birds are homeothermic organisms and the cardiovascular system plays a major role in conserving or removing body heat Our knowledge of cardiovascular structure and function is far more limited in birds than mammals

3. Circulatory system Blood, Veins (carry blood from tissue to heart) Arteries ( cary blood from heart to tissues), Capillaries Heart

4. function Supply entire body with Nutrients Gases Hormones Remove metabolic wastes Regulation of body temperature

5. HEART 4- chambered heart, complete double circulation 1.5-2x larger than in comparable mammals Maintain higher metabolism Smaller birds have relatively larger hearts than larger birds Heart size increase with lattitude , altitude for same species

6. HEART CHAMBERS Atria Right Left= slightly than right atrium Ventricales Right Left= much bigger than right ventricals

7. HEART VALVES (4) Valves allow blood to flow in only one direction Right atrioventricular In birds, it is a single flap between right atrium and ventricles In mammals, it is a tricuspid valve (3 triangular flaps) Left atrioventricular valve (tricuspid valve) Three flaps between left atrium and ventricle

8. Continued Pulmonary valve A semilunar valve, tricuspid Origin of pulmonary artery Aortic valve A semilunar valve tricuspid Origin of aorta

9. Heart histology Three tissue layers Endocardium Most interior lining of the atria and vntricles Myocardiunm Middle layer Entirely cardiac muscle Epicardium Outer connective tissue layer Pericardium Connective tissue sac that enclose heart Pericardial space is filled with lymph fluid and termed pericardial fluid

10. MYOCARDIUM Entirely cardiac muscle Lattice-work appearance Striated like skeletal muscle muscle actin and myosin) Intercalated discs Dark area that searate fibers into cells Low impedence to action potentials so contraction can spread rapidly

11. Heart nerves Has its own conduction system Sinoatrial node (SA node) Atrioventricular node (AV node) Right ring of purkinje fibers (AV bundle)

12. blood Plasma Water (~85%) Protein (~9-11%) Glucose (blood glucose levels in birds are greater than in mammals ; about 200-400 mg/dl) Other constituents: amino acids, waste products, hormones, antibodies and electrolytes

13. Red blood cells Elliptical, biconvex and nucleated Red blood cells are about 6*12 microns in size 2.5 to 4 million/cubic mm Lifespan of 28-48 days Contain haemoglobin oxigen affinity is generally lower in birds than in similar size mammals Hematocrit averages about 40% Hemopoietic bone marrow produces rbc blood

14. CONTINUED Thromobocytes Nucleated Similar function with the non-nucleated platelets of mammalian blood White blood cells Defence against foreign pathogens, immune response

15. Types of avian wbc Lymphocytes- most numerous white blood cells. Either T-lymphocytes or B-lymphocytes produce antibodies; T-lymphocytes attack infected or abnormal cells Heterophil- second more numerous in most birds, phagocytic , use their enzyme-containing granules to lyse ingested materials, motile and can leave blood vessels to engulf foreign materials. Monocytes- motile cells that can migrate using ameboid movements. Monocytes are also phagocytic Eosinophils- make up about 2 to 3% of the WBC population of halthy birds

16. Blood vessels Blood pumped by the avian heart enters the blood vessels. The main types are: Arteries  - carry blood away from the heart & toward the body cells Arterioles  - 'distribute' blood (that is, direct blood where needed with more going to active tissues & organs & less to less active tissues & organs) by vasodilating & vasoconstricting Capillaries  - exchange of nutrients, gases, & waste products between the blood & the body cells Venules   (small veins) &  veins - conduct blood back to the heart

17. Thank you