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How many chambers does the human heart have?
4 chambers (2 atria and 2 ventricles)
Which reptiles have 4 heart chambers?
Crocodiles and alligators
What connects the right atrium to the right ventricle?
Tricuspid valve
What connects the left atrium to the left ventricle?
Bicuspid (mitral) valve
What connects the right ventricle to the pulmonary artery?
Pulmonary semilunar valve
What connects the left ventricle to the aorta?
Aortic semilunar valve
What is the function of the sinoatrial (SA) node?
Acts as pacemaker, initiates contraction of the atria and stimulates AV node
Where is the SA node located?
Upper right atrium
What is the function of the atrioventricular (AV) node?
Passes impulse from atria to Bundle of His
Where is the Bundle of His located?
Between the ventricles
What is the function of the Bundle of His?
Passes signal to Purkinje fibers for ventricular contraction
What is the function of Purkinje fibers?
Cause contraction of both ventricles
What is systole?
Contraction of atria and ventricles
What is diastole?
Relaxation of atria and ventricles
What determines human blood type (A, B, AB, O)?
Specific antigens on the surface of erythrocytes
What antibodies does a person with type A blood produce?
Anti-B antibodies
What happens if incompatible blood types mix?
Erythrocyte agglutination (antibodies attack foreign antigens, forming clumps)
What is agglutination?
Clumping of blood cells due to antibody-antigen reaction
Why is AB+ the universal recipient blood type?
Has no antibodies against any blood type
Why is O- the universal donor blood type?
Has no antigens to trigger immune response
What is the Rh factor?
Another example of a blood surface antigen (+ or -)
What is the sequence of the pulmonary circuit?
Right heart → lungs → left heart
What is the path of blood through the pulmonary circuit?
Which vessel has the lowest oxygen concentration in the body?
Pulmonary artery
Which vessel has the highest oxygen concentration in the body?
Pulmonary vein
Do arteries always carry oxygenated blood?
No, pulmonary artery carries deoxygenated blood to lungs
Do veins always carry deoxygenated blood?
No, pulmonary vein carries oxygenated blood to heart
What are arterioles?
Small arteries wrapped in smooth muscle; major determinants of blood pressure
What are veins?
Vessels carrying blood toward the heart
What are venules?
Small vessels that collect blood from capillaries into veins
What are capillaries?
Smallest blood vessels with a single layer of endothelial cells for gas, nutrient, and waste exchange
What are precapillary sphincters?
Rings of muscle that regulate blood flow into capillaries
What happens when precapillary sphincters are relaxed?
Increased blood flow and nutrient delivery to tissues
What happens when precapillary sphincters are tightened?
Reduced blood flow and nutrient delivery to tissues
What is the sequence of the systemic circuit?
Left heart → body → right heart
What is the path of blood through the systemic circuit?
Left atrium contracts, sending blood through bicuspid valve to left ventricle
How does blood go from the arteries to the tissues?
The blood goes through the arterioles
How does deoxygenated blood return to the right atrium?
Blood returns through venules → veins → superior and inferior vena cava to right atrium.
What is plasma?
Aqueous mixture of proteins, salts, gases, and nutrients in the blood
What is serum?
Plasma without clotting proteins
What are platelets?
Cell fragments involved in blood clotting
What are erythrocytes?
Red blood cells that transport oxygen using hemoglobin
What are leukocytes?
White blood cells that function as phagocytes to engulf foreign particles