lymphatics Flashcards
what is the lymphatic drainage pathway
tracheal ducts receive drainage from the head, neck and proximal forelimb.
left duct joins thoracic duct - right becomes the right lymphatic duct and enters the venous circulation at the thoracic inlet.
right lymphatic duct drains the right thorax and receives the right tracheal duct.
cisterna chyli (between aorta and vertebrae thoracolumbar junction) receives the drainage from the abdominal lymphocentres and from hindlimbs and pelvis via lumbar ducts.
lumbar ducts form a plexus on roof of abdomen and drains into cisterna chyli
thoracic duct originates from cisterna chyli and passes cranially through the aortic hiatus to the mediastinum where it runs cranioventrally to drain the cranial vena cava.
what are the functions of the lymphatic system
maintains fluid balance between body compartments.
remove excess water from interstitial fluid.
transports infectious agents and dead cells. taking antigenic material for presentation to the immune system in the lymph nodes.
enables movement of lymphoid cells
transports dietary lipids and some proteins.
where are the palpable lymph nodes in the dog
parotid
mandibular
superficial cervical (prescapular)
axillary
accessory axillary (sometimes)
retropharyngeal (sometimes)
superficial inguinal
popliteal
femoral
what is the development of the lymphatic system in the foetus
lymphoid vessels form in the mesoderm after CV system established.
6 lymph sacs initially - paired jugular sacs, cisterna chyli and retroperitoneal sacs and the paired iliac cells.
communicating vessels arise between lymph sacs
vessels between the jugular sacs and cisterna chyli form a plexus which develops into thoracic duct.
lymph sacs (except CC) develop into lymph nodes as lymphoid tissue aggregates around them.
mesenchymal cells infiltrate to form lymph channels and other lymph nodes develop along lymphatic vessels.
nodes then seeded with B lymphocytes from the bone marrow and T lymphocytes from the thymus.
how does the lymphatic system act to maintain fluid balance in the body
hydrostatic pressure gradient leads from ISF into the lymphatic capillaries so water is absorbed.
blind ending lymphatic capillaries allow water to enter easily but oppose it moving out.
lymphatic capillaries remove protein from the ISF thereby raising the oncotic pressure inside the lymphatic capillary and favouring the further water uptake from the ISF.
increased flow of lymph favours increased protein uptake which means that when ISF volume is increased the lymphatic system takes up increased amount of protein which both increases the lymphatic absorption of water and reduces the the oncotic pressure in the ISF thereby reducing filtration of water out of the plasma.
where are the palpable lymph nodes in the cat
retropharyngeal
caudal epigastric
accessory axillary
axillary
dorsal superficial cervical
mandibular
superficial inguinal
popliteal
palpable lymph nodes in horse
submandibular nodes
palpable lymph nodes in cattle
prefemoral node and the superficial cervical (prescapular)
what is chyle
the fluid in the thoracic duct that is white in colour with a larger proportion of chylomicrons.
what is the development of the spleen in the foetus
develops from mesoderm in the dorsal mesogastrium.
what is the development of the thymus in the foetus
arises from the pharyngeal pouch from endoderm, mesoderm and ectoderm
paired organ initially which gives off buds that grow down the neck to invade the mediastinum where they form a single organ which extends to the pericardium.
what is movement of lymph within lymphatic vessels due to
bulk flow - hydrostatic pressure differences
what are the other factors that allow movement of lymph
external pressure from skeletal muscles propels lymph along the vessels and also smooth muscle wall of larger lymphatic vessels enables them to contract.
lymphatic vessels contain valves - prevents backflow of lymph
what is drainage of lymph into the venous system reliant on
venous pressure being less than hydrostatic pressure in the lymphatic vessels.
what does failure of lymphatic drainage lead to
formation of oedema (fluid in interstitial space)
effusions (free fluid within a cavity)
