The document explains the circulatory system, detailing the components, functions, and differences between open and closed systems. It covers the variations in circulatory systems among vertebrates, including single and double circulation, and describes specific features in fish, amphibians, reptiles, birds, and mammals. The document also highlights the four-chambered heart in birds and mammals, emphasizing its role in efficiency and temperature regulation.

1. LESSON 1: PUMP AND
THE FLOW OF LIFE:
THE PARTS OF CIRCULATORY SYSTEM AND THEIR FUNCTIONS

2. CIRCULATORY SYSTEM
• THE CIRCULATORY SYSTEM IS MADE UP OF BLOOD VESSELS THAT CARRY BLOOD AWAY FROM AND
TOWARDS THE HEART. ARTERIES CARRY BLOOD AWAY FROM THE HEART AND VEINS CARRY BLOOD BACK
TO THE HEART. THE CIRCULATORY SYSTEM CARRIES OXYGEN, NUTRIENTS, AND HORMONES TO CELLS, AND
REMOVES WASTE PRODUCTS, LIKE CARBON DIOXIDE.

3. THE TYPES OF CIRCULATORY SYSTEM
• CIRCULATORY SYSTEM IN ANIMALS
• CIRCULATING FLUID
• INTERCONNECTING TUBES
• MUSCULAR PUMP
• INTERSTITIAL FLUID- IS THE FLUID BETWEEN THE TISSUES. IT IS COMPOSED OF WATER, AMINO ACIDS,
SUGARS, FATTY ACIDS, COENZYMES, HORMONES, NEUROTRANSMITTERS, SALTS, AND CELLULAR PRODUCTS. ITS
MAIN FUNCTION IS TO BATHE AND SURROUND THE CELLS OF THE BODY.

5. OPEN AND CLOSE CIRCULATORY SYSTEM
• OPEN CIRCULATORY SYSTEM
• THE CIRCULATING FLUID IS THE HAEMOLYMPH, WHICH ALSO THE INTERSTITIAL FLUID.
• THE BLOOD IS NOT ENCLOSED IN THE BLOOD VESSELS, BUT IS PUMPED INTO A CAVITY CALLED A HEMOCOEL. THE
BLOOD IS CALLED HAEMOLYMPH BECAUSE IT MIXES WITH THE INTERSTITIAL FLUID.
• THE OPEN CIRCULATORY SYSTEM IS COMPOSED OF DUCT SYSTEM (ARTERIES) AND THE BODY SPACES, WHERE
THE BLOOD FLOWS IS VIA DIFFUSION.
• CLOSED CIRCULATORY SYSTEM
• THE CIRCULATING FLUID IS THE BLOOD.
• BLOOD IS CONTAINED INSIDE BLOOD VESSELS, CIRCULATING UNIDIRECTIONAL (IN ONE DIRECTION) FROM THE
HEART AROUND THE SYSTEMIC CIRCULATORY ROUTE, THEN RETURNING TO THE HEART AGAIN.

6. Blood flow open and closed circulatory system
Open circulatory system
Heart  arterial system cell, tissues  sinuses (body spaces)  back to the heart via diffusion
Closed circulatory system
Heart  artery  capillaries cell, tissues  capillaries  veins  back to the heart

7. CIRCULATORY SYSTEM VARIATION IN VERTEBRATES
IN ANIMALS WITH A CLOSED CIRCULATORY SYSTEM, BLOOD PASSES THROUGH THE HEART ONCE OR TWICE IS CALLED
SINGLE AND DOUBLE CIRCULATION, RESPECTIVELY.
SINGLE CIRCULATION
- IS A TYPE OF CIRCULATORY SYSTEM IN WHICH BLOOD ONLY FLOWS THROUGH THE BODY ONCE.
- THE FISH CIRCULATORY SYSTEM
- THE BLOOD OF BONY FISHES, RAYS, AND SHARKS FLOWS THROUGH THE HEARTH ONCE IN EACH COMPLETE
CIRCULATION.

8. These fishes have four structures in their heart- sinus venous, atrium, ventricle, conus arteriosus to
form two pumping chambers.

9. DOUBLE CIRCULATION
• IT INVOLVES TWO PUMPING CIRCUITS- THE PULMONARY CIRCUIT AND THE SYSTEMIC CIRCUIT.
• PULMONARY CIRCUIT
• PULMONARY CIRCULATION TRANSPORTS OXYGEN-POOR BLOOD FROM THE RIGHT VENTRICLE TO THE
LUNGS, WHERE BLOOD PICKS UP A NEW BLOOD SUPPLY. THEN IT RETURNS THE OXYGEN-RICH BLOOD TO
THE LEFT ATRIUM.
• PULMONARY CIRCUIT
• PULMONARY CIRCULATION TRANSPORTS OXYGEN-POOR BLOOD FROM THE RIGHT VENTRICLE TO THE
LUNGS, WHERE BLOOD PICKS UP A NEW BLOOD SUPPLY. THEN IT RETURNS THE OXYGEN-RICH BLOOD TO
THE LEFT ATRIUM.

10. • ALL ARTERIES CARRY OXYGENATED BLOOD AWAY FROM THE HEART EXCEPT FOR THE PULMONARY
ARTERIES, WHICH CARRY DEOXYGENATED BLOOD TOWARD THE HEART EXCEPT FOR THE PULMONARY
VEINS, WHICH CARRY OXYGENATED BLOOD FROM THE LUNGS TO THE HEART.

11. AMPHIBIAN CIRCULATORY SYSTEM
• AMPHIBIANS HAVE TWO CIRCULATORY ROUTES: ONE FOR OXYGENATION OF THE BLOOD THROUGH THE
LUNGS AND SKIN, AND THE OTHER TO TAKE OXYGEN TO THE REST OF THE BODY. THE BLOOD IS PUMPED
FROM A THREE-CHAMBERED HEART WITH TWO ATRIA AND A SINGLE VENTRICLE.
• AMPHIBIANS ARE UNIQUE IN THAT THE PULMOCUTANEOUS CIRCUIT IS PART OF THEIR CIRCULATORY
SYSTEM. THIS CIRCUIT IS RESPONSIBLE FOR BRINGING BLOOD TO THE SKIN FOR GAS EXCHANGE TO
OCCUR, CALLED AS PULMOCUTANEOUS CIRCULATION.

13. REPTILE CIRCULATORY SYSTEM
• GROUP OF REPTILES SUCH AS LIZARDS, SNAKE, CROCODILE, AND TURTLE HAVE DEVELOPED STRUCTURES
THAT REDUCE BLOOD MIXING.
• REPTILES HAVE CLOSED CIRCULATORY SYSTEMS AND EITHER THREE OR FOUR-CHAMBERED HEARTS.
MOST REPTILES HAVE THREE-CHAMBERED HEARTS, EXCEPT FOR THE CROCODILIANS (ALLIGATORS,
CROCODILES, AND CAIMAN), WHICH HAVE FOUR-CHAMBERED HEARTS. THREE-CHAMBERED HEARTS
ALLOW FOR THE MIXING OF OXYGENATED AND DEOXYGENATED BLOOD.

15. CIRCULATORY SYSTEM OF BIRD AND MAMMALS
• BIRDS AND MAMMALS HAVE DEVELOPED FOUR-CHAMBERED HEART.
• IN MAMMALS AND BIRDS, THE HEART IS DIVIDED COMPLETELY INTO FOUR CHAMBERS: TWO ATRIA AND TWO
VENTRICLES. OXYGENATED BLOOD IS FULLY SEPARATED FROM DEOXYGENATED BLOOD, WHICH IMPROVES THE
EFFICIENCY OF DOUBLE CIRCULATION AND IS PROBABLY REQUIRED FOR SUPPORTING THE WARM-BLOODED LIFESTYLE
OF MAMMALS AND BIRDS.
• THE LEFT ATRIUM AND THE LEFT VENTRICLE RECEIVE AND PUMP OXYGENATED BLOOD, RESPECTIVELY, AND THE RIGHT
ATRIUM AND RIGHT VENTRICLE RECEIVE AND PUMP DEOXYGENATED BLOOD, RESPECTIVELY. THESE STRUCTURE
PREVENT MIXING OF OXYGEN-RICH AND OXYGEN-POOR BLOOD.

16. • THE SA (SINOATRIAL) NODE GENERATES AN ELECTRICAL SIGNAL THAT CAUSES THE UPPER HEART
CHAMBERS (ATRIA) TO CONTRACT. THE SIGNAL THEN PASSES THROUGH THE AV (ATRIOVENTRICULAR)
NODE TO THE LOWER HEART CHAMBERS (VENTRICLES), CAUSING THEM TO CONTRACT, OR PUMP. THE SA
NODE IS CONSIDERED THE PACEMAKER OF THE HEART.
• , HAVE THE ABILITY TO MAINTAIN THEIR INTERNAL BODY TEMPERATURE INDEPENDENT OF THE
ENVIRONMENT.

18. •END OF THE LESSON.