Anatomy of the lymphatic system Flashcards
What is the lymphatic system?
- circulatory system
- carries excess interstitial fluid from tissues to heart (unidirectional flow)
- Lymph fluid is clear similar in composition to blood plasma
- Lymph system includes lymphoid organs such as Los, tonsils and thymus
What are the main functions of the lymphatic system?
draining tissue spaces of excess interstitial fluid
transporting digested lipids and lipid-soluble vitamins from the gut to the blood stream
immune response
particulate filtration
What happens when there is obstruction to lymphatic drainage?
can cause lymphoedema, elephantiasis (filariasis)
- occurs post-mastectomy
- effects are unpredictable (can involve whole arm or just hand)
- affects ~25% of Breast Ca patients
How is lymph formed?
‘drainage’
- interstitial fluid drains into blind-ended lymphatic capillaries
- flow aided by skeletal muscular contractions and lymph vessels also contain smooth muscle within walls
- Valves prevent back flow
- ~ 3L of fluid are returned to venous system per day
- return occurs mostly via the THORACIC DUCT
What are the main properties of lymphatic vessels?
- contain smooth muscle
- numerous valves (seen as indentations in lymphogram)
- anastomose freely
- communicate across the midline
- accompany superficial veins and deep arteries/veins
- unite to form larger and more organised system of lymphatic trunks
Superficial vessels will converge and then travel deeper
What are lymph nodes?
- small, bean-shaped aggregations of lymphoid tissue
- found where lymphatic vessels converge
- form part of a network that filters Ag from interstitial fluid and lymph from periphery (venous system)
- node clusters are found at strategic locations
What is the lymphatic drainage of the lower limb?
superficial lymphatic vessels converge onto the superficial inguinal LNs
How do lymphatic vessels follow the anatomy
- superficial vessels follow the veins (= help protect skin from invasion)
- deep vessels follow the arteries
- deep and superficial ducts converge on the CISTERNA CHYLI
What is the cisterns chyli?
- Located between RHS Crus of diaphragm and aortic hiatus
- Crus = muscular part of diaphragm that attached to the posterior wall
- Dilated sac inferior of thoracic duct
- Thoracid duct travels superiorly up to T5-6
- It then enters the venous system at the left venous angle
What is the thoracic duct?
commences @ T12 (aortic artery hiatus) at the superior end of cysterna chyli
- ascends through diaphragm @ aortic hiatus
- lies between aorta and azygos vein
- @ T5, crosses to left to ascent fo the LHS of oesophagus
Where is the R/L venous angle?
junction of internal jugular and subclavian veins
For RHS, this is the commencement of the brachiocephalic vein
What does the right lymphatic duct drain?
right arm, URQ of chest and right side of head and neck
What drains into the thoracic duct?
L subclavian trunk
L jugular trunk
L broncho-mediastinal trunk
What drains into the R lymphatic duct?
R subclavian trunk
R jugular trunk
R broncho-mediastinal trunk
What drains into the Cysterna chyli?
R and L lumbal trunks
intestinal trunk
What is a lymphogram?
imaging with contract iodine dye used to visualise the LNs and lymph vessels
What is a chylothorax?
= presence of lymph fluid (chyle) in the pleural space
- occurs secondary to leakage from thoracic duct
- due to trauma or iatrogenic (e.g/ thorax surgery)
What is the lymphatic drainage of the intestines?
- lacteals in intestinal will absorb dietary fat (in chylomicron form)
- lymph from gut drains in sequential manner:
intestinal -> mesenteric -> central nodes -> cisterna chyli
What are lymphoid organs?
- aggregations of tissues active in immune response of body
- primary lymphoid organs = thymus and bone marrow
- primary lymphoid organs involved in lymphocyte production
- B and T cells made in BM, B cells also educated/mature in BM
- T cells migrate to thymus where they mature
What is the structure of the bone marrow?
red marrow periphery
yellow marrow lumen
All bone marrow is red @ birth
Adulthood: mostly yellow marrow
What are secondary lymphoid organs?
sites where lymphocytes interacts with Ag to generate immune response
e.g. spleen, LNs, MALT+GALT+BALT, Peyer’s Patches
Where is the spleen located?
between 9th and 11th rib
measures 1x3x5 inch
weighs 9 ounces
functions: stores blood, removes old blood cells and encapsulated bacteria
What is the blood supply to the spleen?
What marking allows palpable ID of spleen?
splenic artery (coeliac trunk) Notch on anterior wall
What can cause splenomegaly?
Infection
Inflammation
Haematological
Portal hypertension
What is the lymphatic drainage of the breast?
most of the time
will drain to axilla LNs on ipsilateral side (same side) as breast
How are axilla LNs identified in relation to location?
described at 3 levels in relation to pectoralis minor muscle
What is Virchow’s node?
- left supraclavicular node
- sited at L venous angle where thoracic duct drains into left subclavian vein
- strong indicator of gastric Ca mets
What is MALT?
= mucosa-associated lymphoid tissue
in nasopharynx, comprised of palatine tonsils, lingual tonsils, pharyngeal/adenoids and Waldeyer’s ring
The arch of MALT tissue at back of mouth is comprised of:
- anterior arch (palatoglossus)
- posterior arch (palatopharyngeal)
What is GALT?
= gut-associated lymphoid tissue
contained within appendix structure
70% of appendices are retro-caecal
Long appendix can perforate into superior structures
blood supply to appendix: appendicular branch of ileocolic artery (SMA)
What is the prevalence of an anomalous R subclavian artery and thoracic duct?
<35% of Down’s syndrome patients
esp. retro-oesophageal R subclavian artery
