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