Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
BIO 102 Dr. Ely Chapter 49 Notes – The Circulatory System Part 1 I. Function and Composition of Blood a. Functions of blood i. Transportation and Exchange of substances 1. Oxygen, monomers, and ions are delivered to cells 2. Carbon dioxide and organic wastes are removed from cells ii. Regulation of homeostasis 1. Hormones are circulated throughout the body to deliver signals to tissues and organs 2. Heat can be conserved or dissipated by the constriction and dilation, respectively, of capillaries just below the epidermis iii. Protection 1. The clotting mechanism of blood prevents blood loss due to injury 2. White blood cells detect and disable foreign invaders such as bacteria and viruses b. Composition of blood i. Blood is a connective tissue with two major components 1. Plasma (55%) a. The fluid matrix in which dissolved chemicals, large proteins, and cells (see Formed elements) are suspended b. Plasma is 92% water, 7% plasma proteins, and 1% dissolved ions, gases, nutrients, wastes, and hormones 2. Formed elements (45%) a. Erythrocytes – red blood cells; biconcave discs that carry hemoglobin – the respiratory pigment that delivers oxygen to cells b. Leukocytes – white blood cells; larger, round cells that may leave the capillaries to mount an immune response c. Thrombocytes – platelets; fragments of blood cells that are part of the clotting mechanism i. Blood clotting is the result of an enzyme cascade where the circulating peptide fibrinogen (inactive form) is converted into strong protein threads of fibrin by the enzyme thrombin ii. Fibrin threads trap platelets and even erythrocytes to form the blood clot – a plug that prevents blood loss BIO 102 Dr. Ely II. Animal Circulatory Systems a. Invertebrates may have open or closed circulatory systems i. An open circulatory system consists of a circulating fluid called hemolymph that travels through vessels, but at some point leaves these vessels to mix directly with extracellular fluid outside of tissues. ii. A closed circulatory system consists of blood that is always enclosed within blood vessels; all vertebrates have a closed circulatory system. b. Vertebrate circulatory systems i. The selective advantage of each circulatory system to evolve from lancelet fish amphibian reptile mammals + birds is increased efficiency in circulation and oxygen delivery ii. The lancelet heart is only a more muscular portion of the artery iii. Fish evolved a true chambered heart 1. The capillary beds that developed inside gills reduce blood pressure significantly, this was a selective pressure for the coevolving heart 2. A chambered heart is a stronger pump that could more efficiently circulate blood around the fish body; the fish heart consists of two chambers: an atrium and a ventricle. 3. Blood travels in a single-loop circulation pattern: from the heart, blood travels through the gills to be oxygenated and then continues through the body to deliver oxygen before returning to the heart for another pump iv. Amphibians and reptiles evolved more chambers and double circulation 1. The co-evolution of lungs (tremendous capillary network) and larger body sizes put a premium on more efficient means of oxygen delivery 2. Double circulation evolved to restore the blood pressure lost over the lungs before continuing through the body a. The pulmonary circuit pumps oxygen-poor blood from the heart to the lungs to pick up oxygen, and then returns the blood to the heart. b. The systemic circuit pumps oxygen-rich blood from the heart throughout the body to deliver oxygen, and then returns the blood to the heart. 3. Amphibians and most reptiles have a three-chambered heart a. The right atrium receives oxygen-poor blood from the body b. The left atrium receives oxygen-rich blood from the lungs c. A single, muscular ventricle contracts to push blood out of the heart BIO 102 Dr. Ely i. Both O2-rich and O2-poor blood mix in the single ventricle; recesses in the ventricular wall reduces the extent of this mixing. ii. In some reptiles, mixing is further reduced by an incomplete septum, a dividing wall that extends into the ventricle. 4. Mammals and birds have a completely-divided, four-chambered heart a. Convergent evolution: the four-chambered heart arose independently in both birds and mammals because it provided a selective advantage associated with endothermy (be able to explain why) b. Two atria and two ventricles are completely divided between the left and right halves of the heart (left atrium and ventricle, right atrium and ventricle) i. The right side of the heart receives oxygen-poor blood from the body and pumps it to the lungs ii. The left side of the heart receives oxygen-rich blood from the lungs and pumps it to the body