Anatomy of the lymphatic system

Question 1

What is the lymphatic system?

Answer 1

• 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

Question 2

What are the main functions of the lymphatic system?

Answer 2

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

Question 3

What happens when there is obstruction to lymphatic drainage?

Answer 3

can cause lymphoedema, elephantiasis (filariasis)

• occurs post-mastectomy
• effects are unpredictable (can involve whole arm or just hand)
• affects ~25% of Breast Ca patients

Question 4

How is lymph formed?

Answer 4

‘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

Question 5

What are the main properties of lymphatic vessels?

Answer 5

• 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

Question 6

What are lymph nodes?

Answer 6

• 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

Question 7

What is the lymphatic drainage of the lower limb?

Answer 7

superficial lymphatic vessels converge onto the superficial inguinal LNs

Question 8

How do lymphatic vessels follow the anatomy

Answer 8

• superficial vessels follow the veins (= help protect skin from invasion)
• deep vessels follow the arteries
• deep and superficial ducts converge on the CISTERNA CHYLI

Question 9

What is the cisterns chyli?

Answer 9

• 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

Question 10

What is the thoracic duct?

Answer 10

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

Question 11

Where is the R/L venous angle?

Answer 11

junction of internal jugular and subclavian veins

For RHS, this is the commencement of the brachiocephalic vein

Question 12

What does the right lymphatic duct drain?

Answer 12

right arm, URQ of chest and right side of head and neck

Question 13

What drains into the thoracic duct?

Answer 13

L subclavian trunk
L jugular trunk
L broncho-mediastinal trunk

Question 14

What drains into the R lymphatic duct?

Answer 14

R subclavian trunk
R jugular trunk
R broncho-mediastinal trunk

Question 15

What drains into the Cysterna chyli?

Answer 15

R and L lumbal trunks

intestinal trunk

Question 16

What is a lymphogram?

Answer 16

imaging with contract iodine dye used to visualise the LNs and lymph vessels

Question 17

What is a chylothorax?

Answer 17

= 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)

Question 18

What is the lymphatic drainage of the intestines?

Answer 18

• lacteals in intestinal will absorb dietary fat (in chylomicron form)
• lymph from gut drains in sequential manner:
  intestinal -> mesenteric -> central nodes -> cisterna chyli

Question 19

What are lymphoid organs?

Answer 19

• 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

Question 20

What is the structure of the bone marrow?

Answer 20

red marrow periphery
yellow marrow lumen
All bone marrow is red @ birth
Adulthood: mostly yellow marrow

Question 21

What are secondary lymphoid organs?

Answer 21

sites where lymphocytes interacts with Ag to generate immune response
e.g. spleen, LNs, MALT+GALT+BALT, Peyer’s Patches

Question 22

Where is the spleen located?

Answer 22

between 9th and 11th rib
measures 1x3x5 inch
weighs 9 ounces

functions: stores blood, removes old blood cells and encapsulated bacteria

Question 23

What is the blood supply to the spleen?

What marking allows palpable ID of spleen?

Answer 23

splenic artery (coeliac trunk) 
Notch on anterior wall

Question 24

What can cause splenomegaly?

Answer 24

Infection
Inflammation
Haematological
Portal hypertension

Question 25

What is the lymphatic drainage of the breast?

Answer 25

most of the time

will drain to axilla LNs on ipsilateral side (same side) as breast

Question 26

How are axilla LNs identified in relation to location?

Answer 26

described at 3 levels in relation to pectoralis minor muscle

Question 27

What is Virchow’s node?

Answer 27

• left supraclavicular node
• sited at L venous angle where thoracic duct drains into left subclavian vein
• strong indicator of gastric Ca mets

Question 28

What is MALT?

Answer 28

= 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)

Question 29

What is GALT?

Answer 29

= 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)

Question 30

What is the prevalence of an anomalous R subclavian artery and thoracic duct?

Answer 30

<35% of Down’s syndrome patients

esp. retro-oesophageal R subclavian artery