Chapter 21
PART 1: FUNCTIONS + LYMPH FLOW
Functions of the Lymphatic System ⭐
Drains excess tissue fluid and returns it to bloodstream
Absorbs fats from digestive tract
Protects body from disease
Know this:
The lymphatic system helps maintain fluid balance and immunity.
⸻
Interstitial Fluid ⭐
Fluid found between cells
Comes from blood plasma
Easy way to think:
Blood leaves vessels → becomes interstitial fluid
⸻
Lymph ⭐
Interstitial fluid once it enters lymphatic vessels
Memory trick:
In tissue = interstitial fluid
In lymph vessel = lymph
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How Lymph Moves ⭐
Lymph DOES NOT have a pump.
Lymph moves because of:
Skeletal muscle contractions
Breathing movements
One-way valves
🚨 Teacher trick:
If you see “heart pumping” as an answer → DON’T PICK IT.
⸻
Lymphatic Capillaries ⭐
Tiny vessels that collect interstitial fluid
Made of one cell layer
Function:
Collect excess tissue fluid
⸻
Lacteals ⭐
Specialized lymph capillaries in small intestine
Function: absorb fats
Think:
Lacteals = lipids
⸻
Cisterna Chyli ⭐
Enlarged sac below thoracic duct
Collects lymph from:
✔ legs
✔ pelvis
✔ digestive organs
⸻
Right Lymphatic Duct ⭐
Drains:
Right side of head
Right arm
Right chest
Empties into:
Right subclavian vein
⸻
Thoracic Duct ⭐
Drains:
ALL the rest of the body
Empties into:
Left subclavian vein
🚨 IMPORTANT DIFFERENCE
Right lymphatic duct = right upper body ONLY
Thoracic duct = everything else
Antigen ⭐
* A foreign substance/pathogen marker
* Causes immune response
Examples:
* bacteria
* viruses
* toxins
Easy way to think:
Antigen = enemy/invader
🚨 Teacher trick:
Antigen ≠ antibody
⸻
Antibody ⭐
* Protein made by B cells
* Attacks a specific antigen
Function:
Helps destroy pathogens
Easy way to think:
ANTIbody fights ANTIGEN
⸻
B CELLS VS T CELLS ⭐ (KNOW THIS)
B Cells ⭐
Function:
Produce antibodies
When activated → become:
Plasma Cells ⭐
Secrete/release antibodies
Think:
B = antibodies
🚨 Likely question:
Which cells produce antibodies?
✅ B cells
⸻
T Cells ⭐
Function:
Attack infected cells and help immune response
Think:
T = Takedown
Types of T cells:
Helper T Cells ⭐
* Help activate immune system
* Release cytokines
Cytotoxic T Cells ⭐
* Kill infected cells
Memory T Cells ⭐
* Remember infection for future
Regulatory/Suppressor T Cells ⭐
* Slow/stop immune response
🚨 Teacher trick
B cells = antibodies
T cells = kill/help
⸻
NATURAL KILLER (NK) CELLS ⭐
Function:
Kill virus-infected cells and cancer cells
Uses:
Perforin ⭐
Pokes holes in cell membrane
Granzyme ⭐
Enters cell → kills it
Memory trick:
Perforin = perforates
⸻
INNATE VS ADAPTIVE IMMUNITY ⭐
Innate Immunity ⭐
* Fast
* Nonspecific
* Born with it
Examples:
* skin
* inflammation
* fever
Memory trick:
Innate = immediate
⸻
Adaptive Immunity ⭐
* Specific
* Slower at first
* Builds memory
Involves:
✔ B cells
✔ T cells
Memory trick:
Adaptive = adapts to pathogen
🚨 LIKELY QUESTION:
Which immunity is rapid and nonspecific?
✅ Innate
⸻
HUMORAL VS CELLULAR IMMUNITY ⭐
Humoral Immunity ⭐
= B cells + antibodies
Think:
Humor = body fluids
⸻
Cellular Immunity ⭐
= T cells
Function:
Kills infected cells
🚨 VERY IMPORTANT DIFFERENCE
Humoral = B cells
Cellular = T cells
⸻
THYMUS ⭐
Function:
T cells mature here
🚨 TEACHER TRICK:
Where do T cells mature?
✅ Thymus
❌ Bone marrow
⸻
BONE MARROW ⭐
Function:
Produces blood cells
B cells mature here
Lymph Nodes ⭐
Function:
Filter lymph
Removes:
* pathogens
* debris
* foreign material
Contains:
✔ B cells
✔ T cells
🚨 Teacher trick:
Lymph node = filters LYMPH
NOT blood
⸻
Spleen ⭐
Function:
Filters BLOOD
Removes:
* old RBCs
* bacteria
* debris
Stores:
✔ platelets
✔ blood
🚨 BIG DIFFERENCE:
Lymph node = lymph
Spleen = blood
Likely question:
Which organ filters blood?
✅ Spleen
⸻
Tonsils ⭐
Function:
Protect against inhaled or swallowed pathogens
Types of Tonsils ⭐
Pharyngeal Tonsil (Adenoids)
Location:
Nasopharynx
⸻
Palatine Tonsils
Location:
Back/sides of throat
(Usually what people mean by “tonsils”)
⸻
Lingual Tonsils
Location:
Back of tongue
⸻
Peyer’s Patches ⭐
Location:
Small intestine
Function:
Protect against swallowed pathogens
Think:
Food enters digestive tract → Peyer’s patches help protect
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ANTIBODIES (IMMUNOGLOBULINS) ⭐
IgM ⭐
FIRST antibody made during infection
Memory:
M = made first
⸻
IgG ⭐
Most common antibody
Main antibody in second infection
Can cross placenta
⸻
IgA ⭐
Found in:
* saliva
* tears
* mucus
* breast milk
Function:
Protect body surfaces
⸻
IgE ⭐
ALLERGIES + ANAPHYLAXIS
🚨 MEMORIZE THIS ONE
Likely question:
Which antibody is associated with allergies?
✅ IgE
⸻
IgD ⭐
Found on:
B cell surface
Function:
B cell receptor
⸻
ACTIVE VS PASSIVE IMMUNITY ⭐
Active Immunity ⭐
YOU make antibodies
Examples:
✔ getting sick naturally
✔ vaccines
Memory:
Active = your body takes action
⸻
Passive Immunity ⭐
You receive antibodies from another source
Examples:
✔ breastfeeding
✔ antibody injection/antivenom
Memory:
Passive = antibodies passed to you
⸻
TYPE IV HYPERSENSITIVITY ⭐
Definition:
Delayed allergic reaction (24–72 hours)
Examples:
* poison ivy
* contact dermatitis
* TB skin test
🚨 Teacher trick:
Immediate allergy ≠ Type IV
Type IV is DELAYED
⸻
QUICK DIFFERENCE CHART (MEMORIZE)
Lymph node → filters lymph
Spleen → filters blood
B cells → antibodies
T cells → attack infected cells
Humoral immunity → B cells
Cellular immunity → T cells
Innate → fast + nonspecific
Adaptive → slower + specific
IgM → first antibody
IgE → allergies