Cardiovascular System: Micrographs

Examine the electron Micrographs so that you understand the ultrastructural equivalents of the structures you have seen under the microscope.

Cardiac Muscle

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Cardiac muscle

Cardiac muscle cells are joined by the interdigitating junction known as the intercalated disk. It consists of three types of membrane-to-membrane contact. The predominant type of contact is the fascia adherens (FA) in which actin filaments at the ends of terminal sarcomeres insert into the fasciae adherentes and thereby transmit contractile forces from cell to cell. Desmosomes (D) provide anchorage for intermediate filaments. Gap (nexus) junctions (N) are present mainly in the longitudinal portions of the interdigitations. These are important for coordinating function among the cardiac muscle cells. There are numerous mitochondria (M) and abundant glycogen (G). Profiles of the sarcoplasmic reticulum (SR) and parts of T tubules (T) can be identified.
Young, B & Heath, JW., Wheaterís Functional Histology, 4th ed., Churchill Livingstone, London, 2000, p. 115.


Types of Capillaries

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Types of capillaries

Three basic types of blood capillaries are illustrated. They are differentiated by the continuity of the endothelial cell and the basal lamina. A, continuous capillary; b, fenestrated capillary; c, discontinuous capillary (sinusoid). Rat diaphragm, pancreas and liver, respectively.
Weiss, L. ed., Cell and Tissue Biology, 6th ed., Urban & Schwarzenberg, Baltimore, 1988, p. 381.


Continuous Capillary (myocardium, cat)

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Continuous capillary

Endothelial cells of continuous capillaries are joined by tight junctions. They contain pinocytotic vesicles (arrows). There is a continuous basal lamina.
Fawcett DW, The Cell: An Atlas of Fine Structure, WB Saunders, Philadelphia, 1966, p. 403.


Fenestrated Capillary (nonglomerular region of kidney)

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Fenestrated capillary (nonglomerular region of kidney)

Arrows indicate fenestrae closed by diaphragms. In this cell the nucleus (N), Golgi complex (G), and centrioles (C ) can be seen. Note the continuous basal lamina on the outer surface of the endothelial cell (double arrows).
Junqueira, LC and Carneiro, J, Basic Histology, 11th ed., McGraw-Hill, New York, 2005. p. 216.


Sinusoidal Capillary

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Liver sinusoid in cross section (rat). Open fenestrae are evident in the endothelial cell cytoplasm. The space of Disse is between the sinusoidal wall and the hepatocytes.
Cormack, D.H. Hamís Histology, 9th ed., Lippincott, Philadelphia, 1987, p. 531.