Department of General HistolgyDepartment of General Histolgy

Practical lessonPractical lesson

TopicTopic: : The cardiovascular system

This transverse section of the subendocardial portion of the myocardium shows Purkinje fibers and adjacent myocardium. Purkinje fibers are modified myofibers that conduct electrical impulses from the atrioventricular bundle to the myocardium.

Purkinje fibersPurkinje fibers Cardiac muscle cellsCardiac muscle cells Loose connective tissueLoose connective tissue

Cardiac muscleCardiac muscle fiber nucleifiber nuclei Capillary w/ red Capillary w/ red blood cellsblood cells Intercalated diskIntercalated disk

The wall of the aorta consists of three layers or tunics: 1. tunica intima The wall of the aorta consists of three layers or tunics: 1. tunica intima (innermost layer) includes the endothelium and subendothelial connective tissue (innermost layer) includes the endothelium and subendothelial connective tissue 2. tunica media (middle layer) consists of smooth muscle cells and elastic tissue 2. tunica media (middle layer) consists of smooth muscle cells and elastic tissue 3. tunica adventitia (outermost layer) is composed of loose connective tissue 3. tunica adventitia (outermost layer) is composed of loose connective tissue which gradually merges with the surrounding connective tissue.which gradually merges with the surrounding connective tissue.

The aorta (elastic or conducting artery) has a thick tunica media that contains The aorta (elastic or conducting artery) has a thick tunica media that contains both smooth muscle cells and elastic fibers. The boundary between the tunica both smooth muscle cells and elastic fibers. The boundary between the tunica media and the tunica intima (also thicker in elastic than other arteries) is not well media and the tunica intima (also thicker in elastic than other arteries) is not well delineated. There is no distinct internal elastic lamina, because of the presence of delineated. There is no distinct internal elastic lamina, because of the presence of many other elastic layers in the media.many other elastic layers in the media.

LumenLumen Tunica intimiaTunica intimia Tunica mediaTunica media Tunica adventitiaTunica adventitia

This slide shows cross-sections of a muscular artery and an adjacent This slide shows cross-sections of a muscular artery and an adjacent vein. Note the prominent internal elastic lamina of the muscular artery, vein. Note the prominent internal elastic lamina of the muscular artery, and the smaller wall-to-lumen size ratio of the vein compared to the and the smaller wall-to-lumen size ratio of the vein compared to the muscular artery. Muscular arteries have a thicker wall than veins of muscular artery. Muscular arteries have a thicker wall than veins of similar size, reflecting the higher pressure of the arterial circuit.similar size, reflecting the higher pressure of the arterial circuit.

In comparison to elastic arteries characteristic features of muscular In comparison to elastic arteries characteristic features of muscular arteries are the presence of more abundant smooth muscle cells and less arteries are the presence of more abundant smooth muscle cells and less elastin in the media, a thinner tunica intima and a prominent internal elastin in the media, a thinner tunica intima and a prominent internal elastic lamina. Compared to muscular arteries, veins have a thinner wall elastic lamina. Compared to muscular arteries, veins have a thinner wall for the size of their lumen, they show no distinct internal elastic lamina, for the size of their lumen, they show no distinct internal elastic lamina, and they have a thinner tunica media and a thick tunica adventitiaand they have a thinner tunica media and a thick tunica adventitia

Internal elastic lamina Tunica media (artery) Tunica media (vein) Tunica adventitia (artery) Tunica adventitia (vein) Adipocytes