Anatomy and physiology of lymphatic systems

thoracic duct drains lymph from

whole body except right side of head & neck, right upper limb, right side of thorax

origin of thoracic duct

upper end of cisterna chyli

cisterna chyli location

in front of LV1–2 vertebrae

cisterna chyli formed by

union of intestinal, lumbar, descending intercostal trunks

termination of thoracic duct

left venous angle (junction of left internal jugular & subclavian veins)

right lymphatic duct drains lymph from

right side of head, neck, thorax, right upper limb

termination of right lymphatic duct

junction of right internal jugular & right subclavian veins

lymph definition

transparent watery fluid, slightly yellow, similar to plasma

rate of lymph flow per hour

120 ml/hr

rate of lymph flow per day

~3 L/day

major organ contributing to lymph

liver (~2/3 of lymph formed)

protein concentration in liver lymph

5–6 g/dL

protein concentration in thoracic duct lymph

3–5 g/dL

composition of lymph

water, electrolytes, proteins, cell debris, metabolic products

lymphatic capillary structure

endothelial cells overlap forming minute valves

factor opening lymphatic valves

increased interstitial fluid pressure

lymphatic pump mechanism

smooth muscle contraction propels lymph one way via valves

external aids to lymphatic flow

skeletal muscle contraction, arterial pulsation, body movements

primary lymphatic organs

thymus and red bone marrow

secondary lymphatic organs

lymph nodes and spleen

lymphatic follicles definition

masses of lymphatic tissue without capsule, scattered in mucosa

MALT stands for

mucosa-associated lymphatic tissue

examples of MALT

respiratory, gastrointestinal, urinary, reproductive tract mucosa

functions of lymph nodes

filter lymph, activate immune system, produce T & B lymphocytes, destroy pathogens

histology of lymph node cortex

lymph follicles (primary and secondary)

histology of lymph node medulla

cords or plates

histology of lymph node sinuses

subcapsular, corticotrabecular, medullary sinuses

regional lymph nodes cervical

head & neck infections, thyroid cancer spread

regional lymph nodes supraclavicular

Virchow’s node, gastric carcinoma metastasis

regional lymph nodes axillary

breast cancer drainage

regional lymph nodes inguinal/femoral

lower limb infections, STDs

regional lymph nodes pre/para-aortic

abdominal malignancies

regional lymph nodes mediastinal

lung cancer, TB

thymus location

superior mediastinum

thymus size in infants

~70 g, large

thymus after puberty

atrophies

histology of thymus cortex

thymocytes, reticular cells, plasma cells, macrophages, monocytes, eosinophils

histology of thymus medulla

large pale epithelial reticular cells, Hassal’s corpuscles

spleen location

left hypochondrium, in contact with ribs 9–11

spleen is

largest single mass of lymphatic tissue

functions of spleen

immunologic blood filter, defense, destruction of old RBC/WBC/platelets, antibody production

histology of spleen white pulp

Malpighian corpuscles, central arteriole

histology of spleen red pulp

venous sinuses, erythrocytes, lymphocytes, monocytes, granulocytes

tonsils definition

lymphoid organs covered by mucous membrane forming ring around pharynx

types of tonsils

pharyngeal (adenoids), tubal, palatine, lingual

function of tonsils

first line of defense

peyer’s patches location

ileum

appendix contains

lymphoid tissue aggregates

clinical correlation lymphadenopathy

enlarged lymph nodes

clinical correlation lymphangitis

inflammation of lymphatic vessels

clinical correlation tonsillitis

infection of tonsils

clinical correlation lymphatic filariasis

parasitic blockage causing elephantiasis

clinical correlation lymphoma

malignant lymphoid tumor

functions of lymphatic system protein balance

removes leaked proteins from interstitium

functions of lymphatic system fluid balance

prevents edema by draining excess interstitial fluid

functions of lymphatic system waste clearance

returns waste products to bloodstream for excretion

functions of lymphatic system fat absorption

lacteals transport dietary fats (chyle)

functions of lymphatic system immune

transports leukocytes, activates immune responses

formation of lymph

from interstitial fluid via Starling’s forces

factors increasing lymph formation

↑ interstitial fluid pressure, ↓ plasma colloid osmotic pressure, ↑ capillary hydrostatic pressure, ↑ capillary permeability

lymphatic pump importance

propels lymph forward, aided by valves and external compression

flow of lymph sequence

blood capillaries → interstitial spaces → lymphatic capillaries → lymphatic vessels → lymph nodes → lymphatic vessels → lymphatic ducts → venous junctions

lymph trunks lumbar

drains lower limb, pelvis, kidneys, adrenal glands, abdominal wall

lymph trunks intestinal

drains stomach, intestines, pancreas, spleen, liver

lymph trunks bronchomediastinal

drains thoracic wall, lungs, heart

lymph trunks subclavian

drains upper limb

lymph trunks jugular

drains head and neck

thoracic duct origin

cisterna chyli

cisterna chyli ascends in

posterior mediastinum

thoracic duct ends in

left brachiocephalic vein origin or left venous angle

right lymphatic duct drains

right upper quadrant of body

lymphatic endothelial cells role

valve formation and contraction aiding lymph flow

lymphatic flow during exercise

increased due to skeletal muscle compression and arterial pulsation

low interstitial pressure effect

low lymph flow rates

high interstitial pressure effect

increased lymph flow rates

lymphatic system components

lymph, lymphatic vessels, lymphatic cells/tissues, lymph organs

lymph node principle role

filter lymph before blood entry

spleen framework

capsule, trabeculae, reticulum

tonsils protective role

immune surveillance at pharyngeal entrance

clinical importance of supraclavicular node

indicator of abdominal malignancy

lymphatic filariasis consequence

elephantiasis due to lymphatic obstruction

lymphoma definition

malignant proliferation of lymphoid tissue

lymphatic capillary valves

prevent backflow, allow one-way entry of fluid

lymphatic pump contraction

triggered by filling of lymphatic segment

external compression examples

skeletal muscle, arterial pulsation, body movements

lymphatic system overall role

maintains fluid balance, protein concentration, fat absorption, immune defense