Cardiovascular System - Lymphatic Development
|Embryology - 15 Feb 2019 Expand to Translate|
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- 1 Introduction
- 2 Some Recent Findings
- 3 Lymphatic Vessels
- 4 Lymphatic Vessel Development
- 5 Lymphatic Vessel Contraction
- 6 Molecular Development
- 7 Abnormalities
- 8 References
- 9 Additional Images
- 10 External Links
- 11 Glossary Links
An important part of the cardiovascular system is the lymphatic vasculature, which functions to both return interstitial fluid (lymph) to the bloodstream and also as part of the immune system. In the embryo, lymphatic development begins at the cardinal vein, where venous endothelial cells differentiate (express Prox1) to form lymphatic endothelial cells that out-pocket and bud to form lymph sacs. During development these lymph sacs remodel to form both the lymphatic space within future nodes, formed by engulfed connective tissue, and the associated afferent and efferent vessel network.
This system was first identified by Aselli G. (1627) in a paper "De Lacteibus sive Lacteis Venis", Quarto Vasorum Mesarai corum Genere novo invento. Milan: Mediolani. Then postulated by Sabin (1902) as venous in origin, it required a recent 2007 lineage tracing study to confirm this theory. Only vertebrates possess a true lymphatic vascular system, with primitive fish possessing a lymphatic-like secondary vascular system that also contains blood. Clinically, important for roles in immune surveillance and oncogenic (cancer) processes.
|Cardiovascular Links: cardiovascular | Heart Tutorial | Lecture - Early Vascular | Lecture - Heart | Movies | 2016 Cardiac Review | heart | coronary circulation | heart valve | heart rate | Circulation | blood | blood vessel | blood vessel histology | heart histology | Lymphatic | ductus venosus | spleen | Stage 22 | cardiovascular abnormalities | OMIM | 2012 ECHO Meeting | Category:Cardiovascular|
Some Recent Findings
- Lymph capillaries - begin as blind-ending tubes in connective tissue, larger than blood capillaries, very irregularly shaped.
- Lymph collecting vessels - larger and form valves, morphology similar to lymph capillaries.
- Lymph ducts - 1 or 2 layers of smooth muscle cells in wall.
- (Remember the anatomy acronym NAVL = Nerve, Artery, Vein and Lymph)
- single-cell layer of overlapping endothelial cells
- lack a basement membrane
- lack smooth muscle cells or pericytes (pre-collecting and collecting trunks contain both)
- linked by discontinuous endothelial cell-cell junctions (button-like).
- junctions open in response to increased interstitial fluid pressure.
Lymphatic microvasculature model
Lymphatic Vessel Development
Tunneling model of lymphatic vessel formation.
|The model shown here is from a recent paper and is based on ultrastructural observations performed in in vitro and in vivo models of lymphangiogenesis. Lymphatic endothelial cells (LEC) display tight junctions and interdigitations, and are connected to the surrounding collagen fibers by anchoring filaments.
Note that this postnatal model may differ from developmental lymphatic vessel development.
Lymphatic Vessel Contraction
Lymphatic vessels undergo spontaneous rhythmic contractions which aid lymph flow. This is most easily demonstrated in models based upon mesentry lymphatics of the gastrointestinal tract. Contractile activity is regulated by physical factors (transmural pressure) and neurological (alpha-adrenergic, histamine, bradykinin) acting on lymphatic smooth muscle. Contractility and receptor expression may also be different in different parts of the lymphatic system.
Alpha-adrenergic - alpha 1- and not alpha 2-adrenoceptors.
Histamine - lymphatic smooth muscle via stimulation of H(1) (and in some vessels H(2)) receptors.
Bradykinin - chronotropic but not inotropic effects on lymphatic pump activity via stimulation of B1 receptors.
Lymphatic Vasculature Organization
Notch probably mediates choice of fate between arterial and venous.
Prox1 Prospero-related Homeobox 1 - expressed in a subpopulation of blood endothelial cells that then generate, by both budding and sprouting, cells of the lymphatic vascular system. Triggers the molecular program leading to the formation of the lymphatic system. (OMIM - PROSPERO-RELATED HOMEOBOX 1; PROX1)
Tie (Tie1 and Tie2) tyrosine kinase receptors.
Vascular endothelial growth factor (VEGF) family of proteins and angiopoietin/Tie, Notch, and ephrin/Eph pathways play major roles in eary vessel development. (VEGFR-3)
Dysplasia of childhood form lymphatic capillaries or collectors, which form fluid-filled cysts.
- lymphatic spaces lined by endothelium
- smooth muscle fascicles in the septa between the lymphatic spaces
- lymphoid aggregates in the delicate collagenous stroma
- Sabin, F. R. On the origin of the lymphatic system from the veins and the development of the lymph hearts and thoracic duct in the pig. (1902) Am. J. Anat. 1, 367-389.
- <pubmed>14581448</pubmed>| JCB
- <pubmed>21702933</pubmed>| PMC3141733 | BMC Cell Biol.
- <pubmed>21576390</pubmed>| PMC3166860 | J Cell Biol.
- Lymphology - Journal Homepage
<pubmed>18519960</pubmed> <pubmed>17036631</pubmed> <pubmed>16212503</pubmed> <pubmed>15293565</pubmed> <pubmed>14704766</pubmed> <pubmed>12543725</pubmed>
<pubmed>19056883</pubmed> <pubmed>17908929</pubmed> <pubmed>17202268</pubmed> <pubmed>16291864</pubmed> <pubmed>16877368</pubmed> <pubmed>11937485</pubmed>
Lymphatic endothelial cell identity is reversible and its maintenance requires Prox1 activity Nicole C. Johnson, Miriam E. Dillard, Peter Baluk, Donald M. McDonald, Natasha L. Harvey, Sharon L. Frase, and Guillermo Oliver Genes Dev. 2008;22 3282-3291
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Cite this page: Hill, M.A. (2019, February 15) Embryology Cardiovascular System - Lymphatic Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Cardiovascular_System_-_Lymphatic_Development
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G