Lymph heart musculature in birds

Abstract

Development and innervation of the lymph heart musculature of chicken, emu, rhea, and duck was studied by electron microscopy at post-hatch ages from 3 days to adulthood. Development of innervation was monitored by acetylcholinesterase staining. Horseradish peroxidase was used to determine the extent of the transverse tubule network. Chickens were unusual among these birds in that lymph heart myocytes had already undergone a definitive differentiation and degeneration by 3 days. In ducks and ratite birds, lymph heart myocytes more slowly but progressively differentiate a cytomorphology that does not conform in all characteristics to cardiac or skeletal muscle and even resembles in some aspects, smooth muscle. Myofibrils become the dominant cytoplasmic structure, transverse tubules form "internal couplings" with agranular reticulum cisternae, and "external couplings" are formed between myocytes at myomyal junctions. The myomyal junctions also contain AChE-positive reaction product and some subplasmalemmal vesicles that lack a dense core. The lymph heart myocardium of ducks of 2 weeks demonstrated mitotic figures. In adult ducks the myosatellite cell numbers diminish and a characteristic pattern of myocyte degeneration appears. In juvenile ducks and ratites some myocytes differentiate to conductile cells, much as the conductile myocytes and myofibers of the blood heart. The lymph heart innervation is described, and the role of nerve in differentiation and maintenance of myocyte morphology in the lymph heart is discussed.

Lymph heart in chick - somitic origin, development and embryonic oedema

“…Some fibres branch, although they do not anastomose like cardiomyocytes (Rumyantsev and Krylova, 1990). Also present are light-coloured cells with few filaments that resemble conductile bundles of His, found in cardiac tissue (Budras et al, 1987). Furthermore, complete automaticity has been described after denervation in amphibians (Rumyantsev and Krylova, 1990).…”

“…The lymph heart musculature revisited The lymph heart musculature has peculiar properties suggesting it cannot be ascribed to the classical groups -smooth, skeletal striated or cardiac striated muscle (Budras et al, 1987). Despite some species-specific differences, its histological structure is similar to the striated skeletal muscle fibres (multinucleated, with peripherally located nuclei) but thinner in diameter.…”

“…For the first time we described the innervation of this organ as being purely somatic and, moreover, to diminish during the second half of in ovo development. This may, however, be specific to chick as some other bird species retain a specific role of the lymph heart in copulatory organ erection (Budras and Berens von Rautenfeld, 1984) and thus the suggestion of parasympathetic innervation is relevant (Budras et al, 1987). The autonomic innervation of the smooth muscle layer of the lymphatic collectors (Witte et al, 2006) may perhaps develop only postnatally.…”

“…In some birds, e.g. duck and emu, the lymph assists copulatory organ erection of male adults and lymph hearts function postnatally to return lymph from the lymphatic erectile phallus to the venous system (Budras and Berens von Rautenfeld, 1984). Unlike birds, amphibians have several pairs of lymph hearts along the vertebral column which remain functional into adult life.…”

“…Its striated musculature has ultra-structural features of both cardiac and smooth muscle so a separate histological category has been proposed (e.g. Budras et al, 1987). Controversy remains regarding its origin with some researchers suggesting it develops either from local mesenchyme or from myotomes (Waldeyer, 1864;Schipp and Flindt, 1968), or is derived from the embryonic venous system (Fedorowicz, 1913;Jolly and Lieure, 1934).…”