Animal Physiology
Topic: Blood Circulation
Chong Yee Ling
BSc.(UPM), MSc.(UNIMAS),PhD(PennState) – Wildlife Virology and Evolution
Department of Zoology
Faculty of Resource Science & Technology
Universiti Malaysia Sarawak
This OpenCourseWare@UNIMAS and its related course materials are licensed under a Crea<ve Commons A>ribu<on-­‐NonCommercial-­‐ShareAlike 4.0 Interna<onal License. At the end of the unit, you should be able to: 1. Discuss the importance of blood circulation & transportation.
2. Compare different circulation systems in different
invertebrates.
- gastrovascular, open versus closed circulatory system.
3.
Compare different circulatory systems in different
vertebrates.
- open versus closed circulatory system (2-chamber, 3-chamber and 4chamber hearts).
The importance of blood circula8on and transporta8on: • The circulatory system transport gases (i.e. O2 & CO2) and nutrients ( such as glucose and amino acids) throughout the body cells. • Transport metabolites and hormones. • Remove wastes (i.e. excretory products) from the body via the lungs or kidneys. • For the maintenance of homeosta<c mechanisms; e.g. involved in thermoregula8on (i.e. transport heat). • Transmit force (e.g. earth worms locomo<on; ultra-­‐filtra<on in kidneys capillaries). • Etc. Invertebrates that do not have a circulatory system but gastrovascular cavity Key Features:  Circula<on system is not so important.  Diffusion via gastrovascular cavity or direct contact with water.  Low metabolic rate.  High body surface area/volume ra<o.  Small in body size with simple body structure. Invertebrates that do not have a circulatory system but gastrovascular cavity Examples: Cnidarians (i.e. hydra, jellies)  Almost all cells are part of the external layer that are in direct contact with water or in the gastrovascular cavity that are close to the external environment.  Food and dissolved oxygen are transported by water currents with flagella movements of endoderm <ssues.  Contrac<le fibers in jellyfish help in circula<on. Invertebrates that do not have a circulatory system but gastrovascular cavity Flatworms (i.e. planarian)  Trilobed gastrovascular cavity  Cells are close to the diges<ve branches  Nutrient, gaseous and wastes can diffusion from one cell to another.  Muscles contrac<on in flatworms assist in circula<on. Other invertebrates have an OPEN or a CLOSED circulatory system Open circulatory system -­‐ found in arthropods and some molluscs. Circulatory fluid: Hemolymph (blood and inters<<al fluid mixture that flow in the body cavity). The body cavity of these animals is named as hemocoel. It contains copper-­‐based hemocyanin (gives blue-­‐green colour when oxygenated and grey when non-­‐oxygenated). Closed circulatory system -­‐ found in annelids (earthworms). Circulatory fluid: Blood that is contained within blood vessel. It carries iron-­‐based hemoglobin (gives red colour). Invertebrates: Open circulatory system Inters88al 8ssues  Hemolymph carrying nutrients and/or gaseous will be pumped by heart via blood vessels into <ssue spaces and eventually drained back to the heart.  Contrac<on of the heart creates nega<ve pressure and draws the blood from the heamocoel into the heart via the os8a.  Slow circula8on; only suitable for smaller size invertebrates.  Not suitable for large animals because lots of energy is required to pump hemolymph throughout the large open body cavity.  Insects require tracheal respiratory system to transport gaseous. Invertebrates: Closed circulatory system  Rhythmic pulsa<le movements of the heart pump and circulate the blood in the body.  Blood will be pumped by heart into blood vessels, moved into capillaries for nutrients, gaseous and etc. exchanges with the <ssue fluid.  Blood will be returned to the heart via dorsal blood vessel and re-­‐pumped.  In this close circula<on system, fast circula8on with blood retaining in the blood vessels allows blood to be pumped and traveled to far reaching areas of the body part. Vertebrates with CLOSED circulatory system Two different circulatory pathways in vertebrates: Single-­‐loop: Heart pumps blood to gills and back to heart. Two-­‐loop (circuit): Systemic circuit -­‐ heart pumps blood to all parts of the body <ssues except for the lungs. Pulmonary circuit -­‐ heart pumps blood to the lungs only. A Single-­‐loop circulatory pathway Example: fishes  Heart has two chambers (a single atrium and a single ventricle) with one loop .  Atrium receives deoxygenated blood (oxygen-­‐poor) and enters into ventricle.  Ventricle pumps deoxygenated blood into gill.  Gill is the respiratory organ for aqua<c organism.  Oxygenated (oxygen-­‐rich) bloods leave gills and circulate to other part of the body (systemic). Two-­‐circuit circula8on pathway Example: amphibians and most rep8les  Heart has three chambers (two atria but a single ventricle) with two loops.  Deoxygenated bloods entered from the body into the right atrium while oxygenated bloods entered from the lungs/skin into the le_ atrium concurrently.  Deoxygenated bloods pumped out from the ventricle, entered the pulmonary circuit to the lung or skin. Oxygenated bloods are also pumped out from the ventricle, entered the systemic circuit to the rest of the body.  Thus, bloods are pumped twice; be>er circula<on system compared to single loop.  Although both oxygenated and deoxygenated bloods enter the single ventricle, they are kept separated. Complete separa8on of pulmonary and systemic circuits Example: mammals, birds, some rep8les.  Heart is divided into four chambers (two atria and two ventricles) with two loops that are separated by ventricular septum to ensure no mixing of oxygenated and deoxygenated bloods.  Both pulmonary and systemic circuits are completely separated.  Right ventricle pumps blood under pressure to the lungs.  The larger leW ventricle (with thicker <ssues) pumps blood under higher pressure to the rest of the body. Further Reading: Rastogi, S.C. (2007). Essen<als of Animal Physiology, 4th Edi<on. New Delhi: New Age Interna<onal Publishers. Campbell and Reece (2005). Biology, 7th Edi<on. Benjamin Cummings. Moyer, C.D. & Schulte, P.M. (2005). Principles of Animal Physiology. California: Benjamin Cummings Publishers. Prosser, C.L. (1950). Compara<ve Animal Physiology. Philadelphia: W.B. Saunders Company.