chapter 20: lymphatic system Flashcards
What is the main role of the lymphatic system?
Returns leaked fluids from the vascular system back to the blood and provides the structural basis of the immune system.
What are the four main functions of the lymphatic system?
- Drains fluid from tissues back to the bloodstream.
- Houses immune cells that clean the fluid before returning it to circulation.
- Protects the body against foreign and non-foreign invaders.
- Transports fats from the digestive tract back into the bloodstream.
What is lymph?
The fluid inside the vessels of the lymphatic system.
What are lymphatic vessels?
A network of tubes that transport lymph throughout the body.
What are immune system cells?
Cells that help defend against invaders, including:
- Macrophages
- Neutrophils
- Natural killer (NK) cells
- Mast cells
What are lymphoid organs?
Organs where immune cells develop and respond to infections.
What is the thymus and its function?
Small organ located behind the breastbone that plays a crucial role in the immune system by maturing T cells before release into circulation.
Shrinks with age (involution).
What is the red bone marrow and its function?
Found in spongy bone.
Matures B cells before release into circulation.
Produces all blood cells, including lymphocytes.
What are lymph nodes and its function?
Small bean-shaped structures that filter lymph before it returns to circulation.
Lymph flow: Afferent vessels → Subcapsular sinus → Medullary sinus → Efferent vessels.
What are tonsils and its function?
Located in the throat and nasal cavity.
First line of defense against airborne/ingested pathogens.
What is the spleen and its function?
Largest lymphoid organ.
Filters blood by removing old red blood cells and platelets.
Stores platelets, white blood cells, and 250mL of RBCs (10% of total blood volume).
Detects pathogens in blood and triggers an immune response.
What are Peyer’s Patches and its function?
Clusters of lymphoid tissue in the small intestine.
Monitor and defend against harmful gut bacteria.
What is the appendix and its function?
Tube-like structure attached to the large intestine.
Stores lymphoid tissue and beneficial gut bacteria for digestion.
Can become inflamed (appendicitis).
What is capillary exchange?
The process of delivering oxygen and nutrients to cells while picking up waste.
Why is capillary exchange not a 1:1 exchange?
More fluid is pushed out than reabsorbed—this is where the lymphatic system helps.
What is capillary hydrostatic pressure (CHP) and where is it higher?
The pressure of blood against capillary walls that forces fluid out into surrounding tissues.
Higher near the arterial end of the capillary.
What is blood colloid osmotic pressure (BCOP) and where is it higher?
The pressure created by plasma proteins pulling water back into the capillary.
Higher at the venous end.
What happens during filtration at the arterial end?
Nutrients and oxygen are pushed out into tissues.
CHP > BCOP
What happens at the midpoint of the capillary?
There is no net movement of fluid.
CHP = BCOP
What happens during reabsorption at the venous end?
Waste products move back into the bloodstream.
BCOP > CHP
What happens to excess fluid that isn’t reabsorbed?
It is collected by lymphatic capillaries to prevent swelling (edema).
How does lymph return to the bloodstream?
Lymph is drained into the right lymphatic duct (upper right body) or the thoracic duct (rest of the body), then into the subclavian veins.
How does lymph flow through the body?
The lymphatic system has no central pump like the heart, so it relies on:
- Muscle contractions (skeletal muscle pump)
- Breathing movements (respiratory pump)
- Smooth muscle contractions in larger lymphatic vessels
- One-way valves preventing backflow.
What is innate immunity?
- Speed
- Specificity
- Localized / Wide-Spred
- Memory / No Memory
The immune system you are born with.
Fast, non-specific, localized, no memory.
