lymphatics Flashcards
what are the functions of the lymphatic system?
- Drains excess interstitial fluid (up to 3L per day) back into venous circulation.
- Involved in transporting dietary lipids from GI tract to blood (as well as hormones0
- Involved in immune responses that protect against invasion
what is the main disadvantage of the lymphatic system?
plays a role in the spread of malignancy
describe the oncotic and hydrostatic pressure at the arterial and venous end of the capillary bed
o Arterial end: high hydrostatic pressure and low oncotic pressure. Fluid moves out of the capillary into the interstitum to form ISF.
o Venous end: low hydrostatic pressure and high oncotic pressure
how much fluid is taken in and out of the capillary bed each day? what is the excess?
excess 3L/day
o 17 litres taken in per day
o 20 litres removed per day
describe the structure of lymphatic capillaries
- Lymphatic capillaries are one-way tubes
- Made of an endothelial tube. Either have a discontinuous basement membrane or no basement membrane at all – v permeable
describe the composition of lymph
same as interstitial fluid
what do lymphatic capillaries join together to form?
join together to form lymphatic collecting ducts
what’s the difference between lymphatic capillaries and ducts?
ducts have valves
what’s the difference between veins and lymphatic ducts?
• Ducts have valves – more than veins bc they’re at a lower pressure than veins and there’s no heart pumping lymph around.
why do ducts need valves?
needed to stop backflow of lymph into the capillary beds
put the lymphatic vessels in order of biggest to smallest
• Lymphatic duct lymphatic trunk lymph nodes lymph collecting vessels lymphatic capillaries
what is elephantitis and what causes it?
• Roundworm infection of lymph nodes blocking the lymphatic drainage so interstitial fluid builds up in the tissues.
what are lymph nodes?
small masses of lymphoid tissue located along the length of the lymphatic vessels through which lymph is filtered
what surrounds each lymph node?
fibrous capsule
what divides lymph nodes into different segments?
trabeculae
what are the 2 different sections of a lymph node?
outer cortex and inner medulla
what cells are found in the cortex of lymph nodes?
lymphocytes
describe the passage of lymph into, through and out of a lymph node
o Afferent vessel cortex medulla efferent vessel
why do lymph nodes swell?
During infection, you get more lymphocytes to the nodes so there’s swelling of the lymph nodes
where does the thoracic duct run?
in the posterior mediastinum
between the descending aorta and azygous vein
what is the cisterna chyli?
the beginning of the thoracic duct in the abdomen
what is the left venous angle?
where the internal jugular vein joins the subclavian vein and they form an angle
what parts of the body drain into the left venous angle?
3/4 - all abdomen, both legs, left side of thorax, left upper limb, left side of the head and neck drain into the left venous angle
what parts of the body drain into the right venous angle?
Remaining ¼ drains via the right lymphatic trunk
what is a chylothorax?
Any sort of laceration or disruption to the thoracic duct, it leaks lymph into the thoracic cavity
what are the superficial lymph nodes?
cervical, axillary and inguinal
where are the superficial cervical lymph nodes found?
gathered around the external jugular vein
found on the superficial surface of the SCM
describe the passage of vessels from the superficial lymph nodes to the deep lymph nodes?
afferent vessels into the superficial lymph nodes
efferent vessels into the deep lymph nodes
where are the deep cervical lymph nodes found?
vertical chain along the IJV
where is the internal jugular vein?
• Underneath the SCM is the IJV in the carotid sheath with the common carotid artery and the vagus nerve
what is the right jugular trunk?
efferent vessels from the deep cervical lymph nodes
when are lymph nodes most readily palpable?
when fighting infection
how do infected lymph nodes feel?
Firm, tender, enlarged and warm.
how do lymph nodes with malignancies feel?
Firm, non-tender, matted (i.e. stuck to each other), fixed (i.e. not freely mobile but rather stuck down to underlying tissue), and increase in size over time.
what are the primary sites of metastatic neck disease?
mucosal areas of the upper digestive tract.
what type of cancer is metastatic neck disease?
squamous cell carcinoma
what does radical neck dissection involve?
removal of SCM, IJV and the spinal accessory nerve and the cervical lymph nodes.
what are the most common procedures for radical neck dissection?
2 procedures in common use today are the modified radical (leave 1+ structure) and the selective neck dissections (leave 1+ LN group).
what drains into the axillary lymph nodes?
- Important bc 75% of lymph from the breasts drain to these
* Other 25% drain to the parasternal lymph nodes
what are the axillary lymph nodes and what drains into them?
- Humeral – close to axillary pulse. Most lymph from the upper limb comes here
- Pectoral – lymph from anterior chest wall (aka breast)
- Subscapular – posterior chest wall.
describe the route of the lymph once it drains out of the axillary lymph nodes
All of these drain towards central apical which are just below the clavicle supraclavicular nodes right venous angle (on the left side they’ll drain towards the left venous angle)
what is a radical mastectomy
removal of all breast tissue, along with the nipple, axillary lymph nodes and a portion of pectoralis major. This is rarely performed today.
what is a modified radical mastectomy?
removal of breast, nipple and most axillary lymph nodes.
what is the sentinel lymph node?
the first lymph node a tumour reaches
how is sentinel lymph node identification carried out?
- Known tumour is injected with radioactive substance or dye
- Allowed to drain and see where the dye goes
- Remove these nodes and the tumour. Less extensive than removing all the nodes
where are the inguinal lymph nodes found?
in the femoral triangle
what drains into the inguinal lymph nodes
• Drain all the lymph from the lower limb and external genitalia
what are the 2 groups of the inguinal lymph nodes
o Horizontal – (run superficial to inguinal ligament). Superficial lymphatics from anterior abdominal wall, the perineum, and the external genitalia (excl. testes)
o Vertical – lie along termination great saphenous vein
where do the testes and ovaries develop?
Both testes and ovaries start development in the posterior abdominal wall and then descend
where do the testicular and ovarian artery come from and why?
as they descend they take their blood supply with them – testicular and ovarian artery come from the abdominal aorta at L2
where does lymph from the testes drain?
Travels back up with the testicular vein to the para-aortic or the lumbar lymph node - lymph nodes around the aorta
where does lymph from the scrotum go?
goes to the superficial inguinal nodes
where does lymph from the internal and external iliac nodes drain?
drains into the common iliac nodes and then the lumbar nodes.
where does lymph from the GI tract drain?
• Lymph from the GI tract drains into the pre-aortic lymph nodes (celiac, superior mesenteric and inferior mesenteric nodes)
where does lymph from intestinal and right and left lumbar trunks drain?
into cisterna chyli
what is the largest lymphoid organ?
spleen
where is the spleen located?
located in the left hypochondrium, deep to the 9th-11th ribs
what happens in the spleen?
o lymphocyte proliferation
o RBC filtration, destruction and storage.
where is the thymus gland found?
superior mediastinum
what happens to the thymus gland after puberty?
• After puberty the thymus gland undergoes progressive atrophy and is replaced by fat.
