5circulatory systemMulticellular animals do not have most of their cells in contact with the external environment and so have developed circulatory systems to transport nutrients, O2 , CO2 and metabolic wastes. Components of the circulatory system includeblood : a connective tissue of liquid plasma and cellsheart : a muscular pump to move the bloodblood vessels : arteries, capillaries and veins that deliver blood to all tissues
6Function is Circulatory System The circulatory system has a variety of functions :it regulates osmotic balanceit regulates pHit transports nutrients and gasesit carries hormonesit regulates temperatureit is part of the immune system
7การลำเลียงสารในสัตว์ชั้นต่ำ Lower organisms (sponges, worms) have a simple cell-to-cell circulation. Its efficiency is limited by surface-to-volume ratio.การลำเลียงในสัตว์ชั้นต่ำ เช่น ไฮดรา พลานาเรีย อาศัยการแพร่ของสารอาหารผ่านไปยังเซลล์ถัดไป
8Structures that serve some of the functions of the circulatory system in animals that lack the system.
10There are several types of circulatory systems. 1. Open circulatory systems (evolved in insects, mollusks and other invertebrates)pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells.2. Closed circulatory systems (evolved in echinoderms and vertebrates)have the blood closed at all times within vessels of different size and wall thickness.
11Open circulatory systems Insects developed a more complex system:an open system in which blood sloshes about in a body cavity and is pumped by a heart.The heart is a long vessel whose systolic contractions propel the blood through the body cavity.
17Arthropods: peristaltic hearts, open circulatory system
18Closed circulatory systems Higher organisms have a closed system, in which blood is always in the circulatory vessels.A typical route in a closed system would take blood along this route : heart -- arteries -- arterioles -- capillaries -- venules -- veins and back to heart.
23Fish: single circulation Fishes have a simple, single circulation system in which blood from the heart goes to the gills to get oxygenated and from there to body capillaries before returning to the heart.The heart is equally simple, consisting of two chambers: an atrium and a ventricle separated by an atrio-ventricular valve, which prevents back-flow from ventricle to atrium.The problem with such a system is that the heart must pump blood through two capillary beds, gills and body, necessitating high pressure.
32Mammals: double circulation In order to split the work, a double circulation evolved that has one pump for each capillary bed.The heart servicing such a system is a two-cylinder engine. It consists of a double pump :the right atrium/ventricle combination pumps deoxygenated blood to the lungs;the left atrium/ventricle pumps oxygenated blood through the body capillaries.In the double system, deoxygenated and oxygenated blood take separate routes through the heart: