Lymphatics Flashcards
Name the components of lymphatic nodes
Afferent lymphatics, cortex with germinal centres (b lymphocytes) surrounded by T cells, lymph accumulates in subscapular sinuses, macrophages are surrounded throughout, capsule is elastic and smooth mm, blends with fine fibrous trabeculae, medullary sinuses lined by antibody secreting mature B cells ‘plasma cells’
What are the exceptions to the lymph nodes
In the pig everything is reversed and turned inside out
Describe the lymphatic development
Develop later than blood vessels, 6 sacs (outgrowths of veins), plexi of vessels grow from these
Development of lymphatics in embryo
Jugular vein, 2 jugular sacs, 2 interconnecting throacic ducts > final duct formed from caudal Right and cranial Left, 1 retroperitoneal, 1 cisterna chyli, 2 iliac sacs, common iliac vein, caudal vena cava
What drains into the right lymphatic duct next to right jugular vein
Right head, neck, forelimb and thorax
Cisterna
Irregular cavity between caudal vena cava, aorta and spine
Describe the lymphatic system
Drains and filters interstitial fluid called lymph
Drains fatty acids from intestine via lacteals chyle
Transports and houses immune cells: lymphocytes and monocytes/macrophages
Contains lymphatic aggregations including MALT = mucosa-associated lymphoid tissue
What are the lymphatic vessels
2 forces in blood capillaries: HP driving water into intersittum, OP drives water into capillaries
Pressure out is greater at arterial but less at venous end
Describe lymphatic capillaries
Blind ending, endothelium lined, permeable collecting chambers. Permeability is greater than in blood capillaries due to overlapping anchoring filaments,
Describe lymphatic vessels
Not present in CNS, bone marrow, cartilage, epidermis, alveoli or placenta. Thinner walled than veins but contain more valves.
Describe the transport of lymphatic vessels
Skeletal muscle pump, nearby arterial pulsing, intrinsic smooth muscle contractility (sympathetic innervation, constriction if BP decreases)
What is the pathology
Inadequate lymph drainage may lead to oedema
Rupture of thoracic duct > chylothorax (cavity filled with milky fluid, duct eventually heals)
Describe lymph nodes
All lymph passes through one or more lymphocytes, often located where interference is minimal with other organs
Name three infectious spreads associated with the nodes
Lymphadenitis, lymphoma, secondary tumours
What are mononuclear phagocytes
Reticuloendothelial system, present as macrophages in connective tissue around the body, liver kupfer cells, CNS miroglia and in the spleen, phagocyte pathogens/debris/blood cells store fe
What is the lymphoid system
Lymphocytes made in bone marrow, T cells (thymidine) coordinate response and kill infected cells , B cells make antibodies, also in spleen
What is MUCOSA ASSOCIATED
Found in larynx, nose, 3d eyelid, intestine (esp Peyers patches), prepuce, vagina and mammory glands
These are starting points for efferent ducts only, no capsule
Give an account of the spleen
LHS of stomach - develops as mesodermal swelling in gastric mesentery
Various positions in carnivores
Parietal and visceral surfaces, latter receives 25 splenic aa along hilus
What is the outermost internal layer
Capsule, muscular trabeculae
What is red pulp in spleen
Complex reticuloendothelial meswork and blood filled sinus, has many myocytes, break down RBC: iron>haem>biliverdin>bilirubin>bile and urine
Stores rbc
Makes rbc in fetus, platelets in adults
What is white pulp
Lymphoid nodules or cylinders, b lymph. A lymph node for the blood = sinusoids
Describe miscellany of the spleen
Receives sympathetic innervation, few vagal fibres and some myelinated sensory fibres. Haemal nodes found in sheep and deer. Accessory spleens on occasional finding in dogs
What is the thymus
Primary lymphoid organ like bone marrow (where lymphocytes form and mature)
Develop from gill like regions of the throat
Descend into mediastinum to lie ventral to trachea, dorsal to sternum, cranial to the heart
Describe the structure of the thymus
Lobulated.
Cortex = weakly binding thymocytes are eliminated.
Medulla = exposed to HASSALS CORPUSCLES that are epithelial whorls of endo/meso/ectoderm
Express many proteins - allows detection of self reacting cells
