2 Circulation The circulatory system I.General plan II.Blood III.Heart 3
3 Circulation Movement of blood results from: Force imparted from contractions of the heart Elastic recoil of the arteries following filling by cardiac contraction Squeezing of blood vessels during body movements Peristaltic contractions of the smooth muscle surrounding the blood vessels 4
8 Circulation I.General plan Two main types of circulatory systems 1.Open circulatory system Present in many invertebrates Blood pumped by heart empties into a hemocoel Hemolymph bathes tissues directly Large volume (20-40% of body volume) Low pressure (4.5-9.7 mm Hg) Limited ability to alter velocity and distribution of blood flow 5
9 Open Circulatory System Artery Veins There is no distinction between blood and interstitial fluid, collectively called hemolymph. Fig 42.2
10 In insects, other arthropods, and most mollusks, blood bathes organs directly in an open circulatory system. One or more hearts pump the hemolymph into interconnected sinuses surrounding the organs, allowing exchange between hemolymph and body cells.
11 In insects and other arthropods, the heart is an elongated dorsal tube. –When the heart contracts, it pumps hemolymph through vessels out into sinuses. –When the heart relaxes, it draws hemolymph into the circulatory through pores called ostia. –Body movements that squeeze the sinuses help circulate the hemolymph.
12 Circulation 2.Closed circulatory system Vertebrates and some invertebrates (e.g. cephalopods) Blood flows in a continuous circuit Small volume (5-10% of body volume) High pressure (can attain pressures of > 100 mm Hg) Permits high O 2 uptake Allows for ultrafiltration at the kidneys 7
13 Closed Circulatory System Interstitial Fluid: fluid directly bathing cells of the body – distinct from blood. Artery Veins Capillaries Blood Fig 42.2
14 Circulation Basic components of a closed circulatory system A main propulsive organ (heart)- forces blood through the body An arterial system- distributes blood and serves as a pressure reservoir Capillaries- transfer of materials between blood and tissues Venous system- returns blood to the heart and serves as a storage reservoir 8
15 In a closed circulatory system, as found in earthworms, squid, octopuses, and vertebrates, blood is confined to vessels and is distinct from the interstitial fluid. –One or more hearts pump blood into large vessels that branch into smaller ones cursing through organs. –Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.
16 Closed Circulatory System In a closed circulatory system –Blood is confined to vessels and is distinct from the interstitial fluid Figure 42.3b Interstitial fluid Heart Small branch vessels in each organ Dorsal vessel (main heart) Ventral vessels Auxiliary hearts (b) A closed circulatory system Closed systems are more efficient at transporting circulatory fluids to tissues and cells. Earthworm an annelid is the first time we see a closed circulatory system!
17 Blood capacity The higher oxygen capacity of blood, the less volume needs to be pumped. See figure 3.25- p(122). Invertebrate 30% B.W Vertebrate 5-10% B.W Control by : PUMPING FREQUENCY STROK VOLUME
19 The body plan of a hydra and other cnidarians makes a circulatory system unnecessary. –A body wall only two cells thick encloses a central gastrovascular cavity that serves for both digestion and for diffusion of substances throughout the body. The fluid inside the cavity is continuous with the water outside through a single opening, the mouth. Thus, both the inner and outer tissue layers are bathed in fluid. Many invertebrates have a gastrovascular cavity (or) / a circulatory system for internal transport
20 Phylum Cnidaria gastrovascular cavity is fluid filled and ciliated may branch into tentacles
21 In cnidarians like Aurelia, the mouth leads to an elaborate gastrovascular cavity that has branches radiating to and from the circular canal. –The products of digestion in the gastrovascular cavity are directly available to the cells of the inner layer, and it is only a short distance to diffuse to the cells of the outer layer.
22 Planarians and most other flatworms also have gastrovascular cavities that exchange materials with the environment through a single opening. –The flat shape of the body and the branching of the gastrovascular cavity throughout the animal ensure that are cells are bathed by a suitable medium and diffusion distances are short.
25 Several blood vesel have dilations ( contractile) These connection blood vessels act as accessory heart
26 - Annelids Figure 17.19 Mouth Brain Accessory hearts Main heart Coelom Nerve cord Digestive tract Blood vessels Segment walls Excretory organ Anus
27 Giant earth worm Dorsal B.V contract ( peristaltic) 6-8/min BP= 20 mm.Hg Five pairs lateral hearts contract after dorsal to give 75mm.Hg Largest animal without respiratory system 120cm length, 2-3cm dim 500g wight its Hb po 2 50%= 7mm.Hg
28 Echinoderms Star fish, sea urchins, sea cucumber … Has three fluid system : a- Coelomic, b- Hemal (blood), c- Water Coelomic between skin and digestive system For transport nutrients
45 -Closed circulatory ( arteries and veins) -It might be related to respiratory gills and to Form a renal pressure 75mm.Hg. -Blood 6% separated about interstitial fluids15%. -Other mollusks ( open 50%) because mixed of both blood and fluid -Blood distributes according to O 2 consuming what about closed mollusks, cephalopods (octopus and squid)
51 These are from groups of arthropods Arachnids, such as spiders, scorpions, ticks, and mites Arachnids Figure 17.22
52 In many invertebrates ( open) Heart pumps blood into hemocoel – open fluid space- either called blastocoel The fluid in hemocoel called hemolymph or blood and reach tissue by bathing not by vessels
53 Spider and scorpion -similar to insect but have respiratory role Hemocyanin in scorpion With respiratory organs ( lung books) Blood pressure --- hydraulic for foot expansion In jumping spider has BP=400mm.Hg
55 Crustaceans, such as crabs, lobsters, crayfish, shrimps, and barnacles Figure 17.23 Crustaceans
56 Open, and partially open circulatory system. The smallest one without developed circulation Lobster, crabs, Cray fish ------(decapods) Good circulation + respiratory pigment ( hemocyanin) Has gills Dorsal heart in pericardial sinus with ostia
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