Fibrous Pericardium- Tough outer layer- Dense Connective Tissue- keeps heart from overfilling with blood, holds heart in place. Serous Pericardium- Double layered closed sac between heart and fibrous pericardium.

Epicardium- Filled with fat, visceral layer of serous pericardium. Myocardium- cardiac muscle tissue, contracts. Endocardium- lines heart chambers and covers heart valves.

Consist of cardiac muscle tissue that is of course striated and contracts. The branching networks of cardiac muscle cells are cardiac myofibers. The junctions are the intercalated disks. There are gap junctions that allow ions to pass between cells. In the intercellular space around each cardiac myofiber is the endomysium.

The right atrioventricular valve with 3 cusps. The left atrioventricular valve with 2 cusps. They open to allow blood flow and close to prevent a back flow of blood.

Initiate each contraction sequence thus setting your heart rate. Specialized cardiac muscle cells that carry impulses through heart muscle signaling the chambers of the heart to contract in sequence.

Elastic Arteries- Largest- large lumen- more elastin than any other vessel. The thickness of these elastin results in weaker surges of blood pressure causing rhythmic contractions. Muscular Arteries- supply organs- "middle-sized"- thicker tunica media. Contains wavy internal elastic membrane in Tunica Intima and external elastic membrane in Tunica Media. Arterioles- smallest- Tunica Media contain 1 or 2 layers of smooth muscle cells

Continuous Capillaries- most common- occur in skeletal muscle, skin, and CNS. Tight junctions and desmosomes hold endothelial cells together. Intercellular clefts are present allowing small molecules to pass through. Fenestrated Capillaries- contain pores that stretch the endothelial cells. Only occur where there are high rates of small molecules being exchanged between blood and tissue fluid. Sinusoid Capillaries- wide, leaky. Follows twisted path with both wide and narrowed regions. Occur where there is exchange in large molecules like proteins or cells. Capillary beds- network of bodies smallest vessels.

Venules-smallest veins-consist of endothelium. The lumen of a vein is larger than that of an artery. In a vein the Tunica externa is thicker than the Tunica media. Have less Elastin in their walls than arteries.