Lymphoid System Basics & Lymph Flow

What is the lymphoid system

system of organs and network of vessels that recover fluid from body , inspects it , activates immune responses, and returns fluid to bloodstream

Basic map/process of lymphoid system (4 steps)

1. Some fluid from plasma leaves blood capillaries entering space between tissue cells (interstitual fluid)

2. Intersitutal fluid enters lymphatic vessel → fluid = lymph

3. lymphoid system inspects and activates immune response

4. lymph is returned to blood streams

Interstitual fluid vs lymph

interstitual fluid = fluid between tissue cells

lymph = fluid after entering lymphatic vessel

What are the three major functions of the lymphoid system

Fluid recovery, immune surveillance, lipid absorption

Lymphoid system function - fluid recovery - what happens if this doesn’t happen

returns interstitial fluid back to blood stream → if this drainage is bad or not enough → lymphedema

Lymphedema

bad drainage/ fluid recovery → interstitial fluid doesn’t return to blood stream and buildup between tissue cells → swelling

Lymphoid system function - immune surveillance

Excess filtered fluid picks up foreign cells & chemicals while moving through tissues → brings it to lymph nodes, which activates immune response

Lymphoid system function - lipid absorption (use the image)

Inside small intestines → tiny projections called villi → contains blood capillaries and lacteals (the green)

lacteals = lymphatic capillary that absorbs fat/lipids

when fat is absorbed into lacteals →the lymph inside the lacteal becomes lipid-rich = chyle

What are the 4 components of the lymphoid system

Lymph, lymphatic vessels, lymphoid tissue, lymphoid organs

What is lymph + where does it originate + appearance

Lymph is the fluid that gets recovered by lymphatic vessels

originates from body tissue, and before that, filtered out of blood capillaries

clear and colorless

What does Chemical composition of lymph depend on

location

Lymphatic vessels

Also called lymphatics → network/ system that lymph flows through

Pathway of vessels (4)

Lymphatic capillaries → collecting vessels → lymphatic trunk → collecting duct of bloodstream

smallest → largest

Lymphatic capillaries - also called what

terminal lymphatics → where interstitial fluid initially enters lymphatic system

Intercellular clefts

openings in lymphatic capillaries that allow surrounding tissue fluid to enter

Anchoring filament

Help attach lymphatic capillary to surrounding tissue

Collecting vessels - and what do they contain

Bigger lymphatics than capillaries and where the lymph from lymphatic capillaries go

They contain valves (one way door) → prevents lymph from going backwards → only one direction

Lymphatic trunk

Larger than collecting vessels → where the lymph from collecting vessels get drained into

drain major regions of the body → empty towards collecting ducts

• jugular trunks

• subclavian trunks

• bronchomediastinal trunks

• intestinal trunk

• lumbar trunks

where are these located/ the area that they drain from

• jugular trunks → head/ neck

• subclavian trunks → upper limbs

• bronchomediastinal trunks → thoracic/ chest

• intestinal trunk → digestive organs

• lumbar trunks → lower body/ abdominopelvic

Collecting ducts and what are they divided into

largest lymphatic vessels

right lymphatic duct & thoracic duct

Right lymphatic duct vs thoracic duct

right lymphatic duct drains upper right quadrant

thoracic duct drains remainder of body

Cisterna chyli

beginning of thoracic duct that sends lymph from lower body into thoracic duct

Where does lymph ultimately end up

Back to the blood stream through venous angles (subclavian vein/ internal jugular vein)

Fluid Exchange Between the Circulatory & Lymphoid Systems

Circulatory system → blood capillaries → interstitial fluid → lymphatic capillaries → collecting vessels → lymphatic trunks → collecting ducts → subclavian vein → back to cardiovascular system & repeat

How does lymph move / the flow of lymph

similar to venous return but slower and lower pressure

Forward flow of lymph is reliant on ________ , which comes from (what 5)

Forward flow of lymph is reliant of vessel stretching, which comes from

• Lymphatic vessel contractions

• squeezing of skeletal muscles

• pulsations from nearby arteries

• Thoracic pump

• Pull of subclavian veins

Lymphatic vessel contractions

Lymphatic vessels can contract → squeeze the lymph forward while the valves prevent the lymph from going backwards

Skeletal muscle pump

When skeletal muscles contract, it compresses lymphatic vessels which pushes the lymph forward

Pulsation from nearby arteries

arteries expand and recoil as blood pulses through them

this pulsation compresses lymphatic vessels nearby which pushes lymph forward

Thoracic pump

changes in pressure from breathing helps move lymph

Pull of subclavian vein

subclavian vein = where the fluid returns back into the bloodstream

glymphatic system

brain’s drainage system using Cerebral spinal fluid and interstitial fluid around brain blood vessels to remove waste and fluid with help of astrocytes

veins drain CSF and ISF into lymphatic vessels in meninges