LECTURE 9: Circulation Among Animals

• Nitrogen gas - not involved in geological or biological processes in its gaseous form
• Oxygen - Required by aerobic organisms for respiration
• Carbon dioxide - By product of animal respiration and burning of fuel
• Aerobic - takes in oxygen (O2)
• Oxygen acts as final electron acceptor in the electron transport chain (ETC) of aerobic animals to produce ATP (source of energy)
• Sponges and rotifers use diffusion to acquire water, oxygen and nutrients, and excrete wastes
• Cnidarians and ctenophorans use diffusion through their epidermis and gastrovascular cavities to exchange water and gases, and to excrete waste products
• Sponges (Porifera) - Excretion and respiration are through diffusion
• Cnidarians (Phylum Cnidaria)

  • No excretory or respiratory systems

  • Use diffusion to exchange water and gases, and to excrete waste materials
• Platyhelminths (Phylum Platyhelminthes)

  • Do not have circulatory and respiratory systems

  • Gas exchange is through diffusion in the tegument
• Extracellular fluid

  • Present in animals with closed system (i.e. vertebrates, annelids and a few invertebrates)

  • Consists of plasma and interstitial/tissue/intercellular fluid
• Intracellular fluid

  • Found inside the cell

  • Principal component of the cytoplasm
• Hemolymph, the circulating fluid or “blood”, is pumped through blood vessels into a hemocoel or body cavity
• Arthropods and most molluscs have open circulatory system
• Blood is confined in vessels and does not mix with interstitial fluid
• Closed circulatory system found in nemerteans, annelids, cephalopods and vertebrates
• Annelids (Phylum Annelida)

  • Circulatory system closed and segmentally arranged

  • Respiratory pigments (i.e. haemoglobin, hemerythrin or chlorocruorin) often present
• Chordates (Phylum Chordata)

  • With ventral heart

  • With dorsal and ventral blood vessels
• Fish Circulatory System

  • Heart has one atrium and one ventricle
• Ventral aorta transports blood to gills where it is oxygenated
• In fish, Atrium collects deoxygenated blood from the sinus venosus
• In fish, Ventricle receives deoxygenated blood from atrium and pumps this to ventral aorta
• Double circulation in Vertebrates - pulmonary, systematic
• Pulmonary Circulation

  • For reptiles, birds and mammals - deoxygenated blood flows from the

  heart to the lungs where it is oxygenated and oxygenated blood is

  returned back to the heart
• Pulmonary Circulation

  • For amphibians - deoxygenated blood flows through the pulmocutaneous circuit (through the lungs and skin)
• Systemic Circulation

  • Oxygenated blood is transported to all parts of the body
• Amphibian Circulatory System

  • Heart has two atria and one ventricle
• Pulmocutaneous circulation allows gas exchange in the lungs as well as in the skin
• In amphibians, Atria receive oxygenated blood from the lungs and deoxygenated blood from systemic circulation
• Non-Crocodilian Reptile Circulatory System

  • have three-chambered heart containing right atrium, left atrium and ventricle
• In non-crocodile reptiles, Right atrium receives deoxygenated blood from systemic circulation
• In non-crocodile reptiles, Left atrium receives oxygenated blood from lungs.
• Ventricle has three cavities: cavum venosum, cavum arteriosum and cavum pulmonale
• Ventricle separated by septum.
• Crocodilian Circulatory System

  • Crocodiles, alligators and caimans are the only reptiles

  with four-chambered heart comparable to mammals
• Two aorta are connected by foramen of Panizza, which allows blood to bypass the pulmonary circulation when necessary
• Avian and Mammalian Circulatory System

  • With four chambered heart, with two atria and two ventricles
• In avians and mammals, Right atrium receives deoxygenated blood and pumps this to right ventricle
• In avians and mammals, Left atrium receives oxygenated blood from the lungs and pumps this to left ventricle
• Arteries

  • Transport blood from the heart to all parts of the body