circulatory system 2

Located on the posterior wall of the right atrium; acts as the pacemaker of the heart, initiating impulse conduction.

Located in the floor of the right atrium; action potential propagation slows here to allow ventricles to fill.

Electrical bridge connecting atria to ventricles; travels down the interventricular septum.

Conduct impulses down through the interventricular septum.

Rapidly conduct impulses directly to the ventricular myocardium.

Carry blood away from the heart under high pressure. Characterized by thick walls containing a lumen, tunica intima (endothelium + loose connective tissue), tunica media (smooth muscle + elastic fibers), and tunica externa.

Sites of exchange (diffusion zones) between blood and tissues.

Unbroken endothelial lining with tight junctions.

Contains pores (fenestrations) for increased permeability.

Return blood to the heart under low pressure. Contain thinner walls and valves to prevent the backflow of blood against gravity.

is composed of plasma and formed elements originating from pluripotent stem cells (via myeloid and lymphoid stem cell lines)

Biconcave discs lacking a nucleus (ejected during development); specialized to transport oxygen using hemoglobin.

Immune defense cells

Neutrophils, Eosinophils, Basophils.

Monocytes (macrophages) and Lymphocytes (T cells, B cells, Natural Killer cells).

Cell fragments derived from megakaryocytes; essential for blood clotting and plug formation.

Damage triggers intrinsic and extrinsic pathways to form ______

Prothrombinase converts prothrombin into _____

Thrombin converts soluble fibrinogen into insoluble _____, which reinforce the platelet plug to form a solid gel clot (thrombus).

Has A antigens on RBCs; Anti-B antibodies in plasma

Has B antigens on RBCs; Anti-A antibodies in plasma.

Has both A and B antigens; no antibodies in plasma

Has neither antigen; both anti-A and anti-B antibodies in plasma (Universal donor).

Occurs when an Rh-negative mother carries a second Rh-positive fetus.

Fetal Rh-positive red blood cells enter maternal circulation during the first pregnancy/delivery, causing the mother to produce

In subsequent pregnancies, maternal anti-Rh antibodies cross the placenta and cause agglutination (hemolysis) of fetal RBCs, leading to