Rucete ✏ Biology In a Nutshell
1. Types of Circulatory Systems
a) Open Circulatory System
- Found in insects and most mollusks
- Circulatory fluid: hemolymph
- Hemolymph flows through a hemocoel (open cavity between organs)
b) Closed Circulatory System
- Found in annelids, some mollusks (like octopuses and squids), and vertebrates
- Circulatory fluid: blood, which stays within vessels
2. Blood Vessels in Vertebrates
- Arteries: carry oxygenated blood away from the heart
- Veins: carry deoxygenated blood back toward the heart
3. Blood Flow Through the Human Heart
- Deoxygenated blood enters through the superior and inferior vena cava
- → Right atrium
- → Right AV valve (tricuspid)
- → Right ventricle
- → Pulmonary semilunar valve
- → Pulmonary artery to the lungs
- Oxygenated blood returns via pulmonary veins
- → Left atrium
- → Left AV valve (bicuspid/mitral)
- → Left ventricle
- → Aortic semilunar valve
- → Aorta → to the body
4. Circuits of Blood Flow
- Pulmonary Circuit: carries deoxygenated blood to lungs, returns oxygenated blood to heart
- Systemic Circuit: carries oxygenated blood to body, returns deoxygenated blood to heart
5. Heart Conduction System
- SA Node (sinoatrial node): pacemaker; initiates heartbeat
- AV Node (atrioventricular node): relays signal to ventricles
- Bundle of His & Purkinje fibers: spread the signal through ventricles
6. Components of Blood
- Red Blood Cells (Erythrocytes): transport O₂ and hemoglobin, catalyze CO₂ conversion, no nucleus, made in bone marrow, recycled in liver
- White Blood Cells (Leukocytes): fight infection, made in bone marrow
- Platelets: involved in clotting using fibrinogen
- Plasma: liquid part; contains clotting factors, hormones, antibodies, gases, and waste
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Biology in a nutshell