M1: Lymphatic System (readings + LO)

components of lymphatic system

• Lymphatic vessels

• lymphatic organs (spleen, bone marrow, tonsils, thymus, lymph nodes

• lymph (water + plasma proteins) 

what other systme is lymphatic system closely associated with

cardiovascular system

how are lymphatic and cardiovascular system similar/different

• Similar 

  • Transport network

  • Fluid balance 

  • Vessel design (thin-wall tubes w endothelial cells and have valves for 1-way flow) 

• Different 

  • Pump: Cardio = has heart acting as a pump to continuously blood throughout body… lymphatic = no pump, relies of skeletal muscle, breathing pressure, Hydrostatic and osmotic pressure

  • Circuit: cardio = closed loop where blood circulates around body 

    • Lymphatic = starts in tissue → lymph nodes to filter → veins  

  • Purpose: cardio = gas exchange and transport of nutrients, 

    • Lymphatic = fitler pathogens, immune cells, absorb fats

functions of the lympahtic system

1. Draining and transporting interstitial fluid – lymphatic vessels drains tissue space of interstitial fluid that escape from blood capillaries and loose connective tissues ⇒ filters it ⇒ returns to bloodstream (fluid balance) 

   1. most important

2. Absorb fats and transport them to the bloodstream

3. Body defense and immunity: self-defence against infectious organisms and foreign bodies (lymphocytes and macrophages)

lymph

Lymph: excessive tissue fluid, composed of 𝓂 water and plasma proteins from capillaries 

⤷ differs from blood = bc lymph doesnt have formed elements

types of lymphatic vessels

• Lymphatic capillaries: found in spaces between cells (interstitial spaces) and everywhere else that is vascularized 

  • Not found in avascular areas (eg. CNS, bone marrow) ⇒ ∴ more permeable for 

• Larger lymphatic vessels: when lymphatic capillaries join together 

  • Resemble veins but have thinner walls and more valves for 1-way flow

  • Will follow veins and arteries and eventually empty into the thoracic duct and/or right lymphatic duct ⇒ flow into the subclavian vein 

lymphatic vessels

• when lymphatic capillaries join together 

  • Resemble veins but have thinner walls and more valves for 1-way flow

  • Will follow veins and arteries and eventually empty into the thoracic duct and/or right lymphatic duct ⇒ flow into the subclavian vein

lymphatic capillaries

• found in spaces between cells (interstitial spaces) and everywhere else that is vascularized 

  • Not found in avascular areas (eg. CNS, bone marrow) ⇒ ∴ more permeable for

how are lymphatic vessels similar to blood vessels

• Both transport fluid throughout the body

• Both have vessel networks extending throughout most body tissues 

• Larger lymphatic vessel resemble veins in structure

How are lymphatic vessels different to blood vessels  

• Carrying lymph vs blood 

• Begin blindly in tissues vs continous circulation 

• Thinner vs thicker walls

• More valves vs fewer valves

• One-way flow only vs circulatory loop 

• Lymph lacks formed elements but blood contains RBC, WBC, platelets

2 major lymphatic ducts + location + where it empties into

2 main lymphatic vessels ~ 

• Thoracic duct: located on the left side of the body, begins at L2 (@ cisterna chyli) 

  • Drains… lower extremities, abdomen, left arm, left side of the head/neck 

  • Empties into the left subclavian vein 

• Right lymphatic duct: located on the right side of the body 

  • Drains… right arm, right side of the head and neck 

  • Empties into the right subclavian vein  

cisterna chyli

Cisterna chyli: enlarged sac-like at the beginning of thoracic duct (anterior to L2). receive lymph from the lower body before it enters the thoracic duct 

where does the lymph go to from teh ducts

Where does the lymph go to from the ducts? Both thoracic and right lymphatic duct empties into the right/left subclavian vein ⇒ superior vena cava ⇒ heart 

flow of lymph

• Tissues: Lymph starts as fluid that leaks out of blood capillaries and into body tissues.

• Lymphatic Capillaries: Tiny tubes collect this excess fluid, which is now called lymph.

• Lymphatic Vessels: The fluid moves through a network of larger tubes. One-way valves keep the lymph flowing forward.

• Lymph Nodes: Lymph passes through bean-shaped nodes along the way. These nodes filter out germs, waste, and abnormal cells.

• Collecting Ducts: Cleaned lymph flows into two main ducts in the upper chest: the thoracic duct and the right lymphatic duct.

• Subclavian Veins: These ducts empty the lymph directly into the large subclavian veins near your collarbones. [1, 2, 3, 4, 5, 6]

how does lymph move through vessels

• One-way valves (prevents backwards flow) 

• Skeletal muscle contraction (contracting muscles squeeze lymph through vessels) 

• Hydrostatic and osmotic pressure changes (high-low pressure) 

• Respiratory movement (create pressure gradient, moving from high abdominal areas → low-pressure thoracic areas during inhalation 

lymph node

Lymph node: small lymphatic structure found along lymphatic vessels (2-30mm) and found often in groups 

purpose of lymph nodes

Purpose of lymph nodes – filter lymph and slow flow down so contaminants can be removed 

• Has macrophages and endothelial cells that engulf foreign substances, destroy pathogens, remove debris via phagocytosis

afferent vs efferent lymphatic vessels

Afferent lymph vessels: (arrives) carry lymph into a lymph node, has 1-way valves to redirect flow into the node 

Efferent lymphatic vessels: (exit) carries lymph out of a lymph node, valves open away from the node (1-way flow) 

• ⤷ smaller in diameter than afferent 

lymphedema

Lymphedema: build up of excessive lymphatic fluid when lymphatic system is block/damaged  

scenarios when edema occurs (lymphedema)

• During cold/flu where lymph nodes swell and get tender bc of ↑ phagocytic activity 

• Post-mastectomy (breast cancer surgery) – removal of axillary nodes disrupt normal lymph drainage, and cause arm swelling

spleen + purpose

spleen: largest mass of lymphatic tissue in the body (does not filter lymph bc no afferent lymph vessel) 

• Filters blood 

• Removes old RBC

• Support immunity 

• Produce lymphocytes 

• Store blood

major lymphatic regions of the body

1. Cervical lymph nodes (head and neck) 

   1. Drains head, face, scalp, neck, oral, nasal cavities 

2. Axillary lymph notes (armpit) 

   1. Drawings upper limbs, breast tissue, upper chest walls 

3. medistinal/thoracic lymph nodes (chest) 

   1. Drains from lungs, heart, esophagus 

4. Abdominal lymph nodes 

   1. Drains from stomach, liver, pancreas, instines 

5. Inguinal lymph nodes (going) 

   1. Drains from lower limbs, external genitalia, lower abdominal wall

cervical lymph nodes + drains ___

1. Cervical lymph nodes (head and neck) 

   1. Drains head, face, scalp, neck, oral, nasal cavities 

axillary lymph notes

1. Axillary lymph notes (armpit) 

   1. Drawings upper limbs, breast tissue, upper chest walls 

medistinal/thoracic lymph notes + drains

1. medistinal/thoracic lymph nodes (chest) 

   1. Drains from lungs, heart, esophagus

abdominal lymph nodes drains

1. Abdominal lymph nodes 

   1. Drains from stomach, liver, pancreas, instines 

inguinal lymph nodes + drains

1. Inguinal lymph nodes (groin) 

   1. Drains from lower limbs, external genitalia, lower abdominal wall 

where are lymphatics absent in body

• CNS

• eyebals

• internal ear

• cartilage

• bone marrow

• epidermis

why is knowledge of lymphatics important to oncology

• direct impact on natural history

• affects staging and prognosis — ∴ affects intents of treatment (radical and pallative)

• contributes to factors when deciding treatment modality (info about lymphatics in RT = tells u the volume that needs irradiation)