Lymphatics Flashcards
What is an overview of the lymphatic system?
System of thin walled lymph vessels which drain XS ISF fluid from tissues, through a series of lymph nodes, back into circulation (cranial end of thorax, usually thoracic inlet)
What are the roles of the lymphatic system?
- Removal XS water from ISF
- Removal of infectious agents and dead cells
- Antigen presentation- takes infectious agents to lymph nodes
- Movement of lymphatic cells- WBC
- Transport of some proteins
- Transport of dietary lipids from the gut - chylomicrons
How is the lymphatic system arranged?
- Starts with blind ending capillaries- v leaky, discontinuous basement membrane
- these join together and together to form
- larger lymph vessels - larger develop some scarce smooth muscle = some contractile ability.
How is the lymphatic vessel arranged
- thin walled endothelium with some adventitial connective tissue
- other travel with BV
- large vessles have some smooth msucle ans possess valves similar to veins
- Capillaries blind endidn = single endothelial layer with discontinuous BM
What is the different between afferent and efferent lymphvessels
- Afferent blood vessels = coming towards
2. Efferent = going away
What are haemolymph nodes and haemal nodes
haemolymph nodes- lymph nodes with some red blood cells in and look red rather than pale adn beigy
2. Haemal = only found in sheep dorsal abdomen = similar function to spleen, red with lot of vascular tissue!
What are lymphocentres?
- a collection of important lymph nodes in an area
Name the key lymphocentres in the:
- Head
- Neck
- Thorax
- Abdomen
- Hindquarters
- Formelim
- Head - retrioharyngeal, parotid, mandibular
- Neck - superficial and deep cervical
- Thorax - Dorsal and ventral thoracic, mediastinal and bronchial
- Abdomen - lumbar, coeliac, cranial and caudal mesenteric
- Hindquarters - popliteal, ischial, deep inguinal, superficial inguinal, iliosacral
- Forelimb - axillary
What are the palpable LN in a dog?
all potentially palpable if enlarged.
1. mandibular = under chin
2. Parotid = ears
3. pre scapula = infront of shoulder blade
4. Axillary and accessory axillary = armpit
popliteal = behind back knee
What are the palpable lymph nodes in a horse
- normally only the submandibular lymph nodes
What are the palpable lymph nodes in a OX
- Pre scapular and prefemoral lymph nodes are usually palpable in the normal animal
What is the significance between lymph nodes adn lymphatic vessels?
- all lymph nodes are connected up by lymphatic vessels and all have to get to venous circulation
- where does the lymph system develop in the early embryo
2. what are the first few stages
- Develops in mesoderm of embryo
- initially 6 sacs:
a) paired jugular sacs - cranial
b) Cisterna chyli
c) paired iliac sacs - caudal
d) 6th retroperitoneal sac - abdominal cavity - islands join together = lymph vessels. Sacs turn into lymphocentres (except CC)
- lymphatic vessels extend = colonise = lymph vessels
What is the thymus
- a lymphoid tissue, where T lymphocytes come from
- in cranial mediastinum
- once adult = useless = becomes fatty tissue
Explain how the lymphatic system acts to maintain fluid balance in the body
- In most caps, most of time = net filtration of fluid from blood caps: HDS pressure difference outweighs oncotic pressure difference for most of length of cap
- fluid moves into ISF
- BULK flow of fluid (HDS pressure difference) into lymph : greater pressure in ISF than lymph cap
- Lymphatic caps also uptake protein from ISF = lowers oncotic pressure of ISF, inc in lymphatic caps
- Once fluid in lymph, flow within tubes = by bulk flow (HDS pressure differences)
- pressure in venous system must be lower than lymph for lymph to flow down pressure gradient
Do blind ended capillareis favour absorption or filtration?
favour absorption from ISF and oppose filtration
What helps flow within the lymphatic system by bulk flow?
- Overall hydrostatic pressure gradient leading into venous system
- external pressure from skeletal muscle
- SMooth msucle in walls of larger lymph (can constrict to some degree)
- Valves prevent backflow
Why could there be failure of the lymphatic drainage?
- disease of the lymphatic system
- Capacity of lymphatic system overwhelmed = produce so much ISF
- derangement of hydrostatic pressure gradient - no gradient = no lymph flow = no flow = can’t take up more ISF
How could raised vena cava pressure cause fluid in pleural cavity? (pleural effusion)
- VC high pressure = reduced or reversed pressure gradient
2. fluid can’t be removed by lymphatic
Which node drains the deep structures of the forelimb?
- Axillary
When examining a normal horse, which are the only readily palpable lymph nodes?
- Submandibular
A dog presents with a mass on its right dorsal metatarsal area. in addition to a biopsy from the mass, which lymph node should you sample to check for local metastasis?
(top of back foot)
1. popliteal
Where does the thoracic duct originate?
- Cisterna chyli
What causes bulk flow into lymphatic capillaries?
- high hydrostatic pressure in ISF compared to lymphatic capillaries
