Lymphatic system BRookdale

what does lymphatic system maintain

 fluid balance, absorbing fats, and

defending the body against pathogens

Immunity, the body's defense mechanism, comprises two

main branches

innate and adaptive.

The lymphatic system is a network of vessels and organs that work together to drain 

excess fluid

from tissues, transport fats, and support the immune response

Collects excess fluid and proteins from the interstitial spaces and returns them to the bloodstream, preventing edema.

Draining interstitial fluid

Absorbs fats and fat-soluble vitamins from the digestive tract and carries them to the bloodstream.

Transporting dietary lipids

Houses and transports immune cells like lymphocytes and macrophages, playing a vital role in detecting and fighting infections

Involvement with immune response

Components of the Lymphatic System

1.Lymphatic capillaries

2.Lymph vessels

3.Lymph nodes

4.Lymphatic ducts and trunks

5.Primary and secondary lymph organs and tissues

The lymphatic system includes:

Tonsils: Such as the palatine tonsil.

Lymph Nodes:

Lymphatic Vessels:

Thoracic Duct:

Cisterna Chyli:

Spleen:

Peyer's Patches:

Appendix:

Marrow:

1.  Such as the palatine tonsil is part of

2. Including cervical, axillary, mediastinal, intestinal, iliac, and inguinal nodes is part of

3.  A network throughout the body.

4. A major lymphatic vessel that collects lymph from most of the body.

1. Tonsils:

2. Lymph Nodes

3. Lymphatic Vessels

4. Thoracic Duct

1. An enlarged sac that receives lymph from the lower body is part of

2. A large organ that filters blood and houses immune cells is part of

3. Aggregated lymphatic follicles in the small intestine is part of

4. Contains lymphatic tissue is part of

5. Where lymphocytes originate.

1. Cisterna Chyli:

2. Spleen

3. Peyer's Patches:

4. Appendix

5. Red Bone Marrow

is a clear to milky fluid found in the extracellular fluid (ECF) compartment

Lymph 

what does the lymph do

essentially unaltered interstitial fluid that has entered lymphatic vessels

In the gastrointestinal tract, lymph also contains absorbed

dietary lipids

Lymphatic fluid flows from 

periphery towards the central circulation

 general pathway is: for Flow of Lymph

Interstitial fluid → lymphatic capillaries → lymph vessels → regional lymph nodes → thorax →

Right or Left lymphatic duct → Subclavian veins (returning to the bloodstream)

Lymphatic Capillaries;Slightly larger than blood capillaries, with a unique "one-way" valve system that

allows interstitial fluid to enter but prevents it from exiting

Structure:

Specialized lymphatic capillaries in the small intestine responsible for absorbing

dietary lipids.

Lacteals

The term for lymph that contains absorbed lipids.

Chyle:

Lymph movement is driven by

Pressure gradients in the interstitial space.

Skeletal muscle contractions that compress lymph vessels.

Respiratory movements that create pressure differences. Any obstruction or malf

unction in lymph flow can lead to edema (swelling).

Primary Lymph Organs includes

Bone marrow and thymus

Site where stem cells originate and B cells mature.

Bone Marrow

Site where T cells mature. These are the locations where stem cells divide

and develop into immunocompetent cells (cells capable of mounting an immune

response)

Thymus Gland

Secondary Lymph Organs includes

Spleen

Lymph Nodes

Other lymphoid tissues (e.g., tonsils, Peyer's patches) These are the sites where most

immune responses occur.

he thymus is crucial for 

 T cell maturation.

Contains a large number of immature T cells. These cells proliferate andmature with the help of dendritic cells and specialized epithelial cells. Approximately 25% of T cells survive this rigorous maturation process.

Outer Cortex

Contains more mature T cells ready to enter circulation.

Inner Medulla:

Lymph nodes act as 

filters, trapping and destroying foreign substances and pathogens.

Key

regional lymph nodes include:

Submandibular

Cervical (neck)

Axillary (armpit)

Mediastinal (chest)

Inguinal (groin)

Internal structure and cellular components of a lymph node

Capsule:

Sinuses:

Cortex:

Medulla

1. 1.Outer protective layer

2. Spaces within the node where lymph flows (subcapsular, trabecular, medullary).

3. Contains B cells and germinal centers for B cell proliferation.

4. Contains B cells, plasma cells, and macrophages.

5. Rich in T cells and dendritic cells.

1. Capsule:

2. Sinuses:

3. Cortex

4. Medulla:

5. Inner Cortex:

Cells found within lymph nodes

T cells and Dendritic cells 

B cells

Follicular dendritic cells

Macrophages 

Plasma cells

T cells and Dendritic cells are found

B cells found

Follicular dendritic cells 

Macrophages are found in

Plasma cells found

• (inner cortex)

• (around germinal centers and in the medulla)

• germinal centers)

• (germinal centers and medulla)

• (medulla)

Route of lymph flow through a lymph node:

Afferent lymphatic vessel (lymph enters)

↓

Subcapsular sinus

↓

Trabecular sinus

↓

Medullary sinus

↓

Efferent lymphatic vessel (lymph exits via the hilum)

Lymph enters the node via _________  percolates through the sinuses.

afferent lymphatic vessels 

Immune cells within the node (lymphocytes, macrophages)

encounter antigens in the lymph.

carry filtered lymph, antibodies, and activated T cells away from the node.

Efferent vessels

largest lymphatic organ.

The spleen

Composed of lymphatic tissue; this is where lymphocytes and macrophages perform immune functions

unctions.

White Pulp

Consists of venous sinuses and splenic cords; it serves as a reservoir for platelets

and is the primary site for the destruction of old red blood cells.

Red Pulp

immune system has two main branches

 Innate Immunity

Adaptive Immunity

Non-specific, inborn defense mechanisms.

 Specific, acquired defense mechanisms with memory.

Cell-mediated immunity

Antibody-mediated (humoral) immunity

. Innate Immunity

Adaptive Immunity

Innate immunity provides immediate, non-specific protection. Key components include

• Physical Barriers:

• Intact skin with its normal flora.

• Mucous membranes.

1. Chemical Barriers:

2. Stomach acid (low pH).

3. Acidic pH of the urinary tract.

4. Lysozyme in tears and saliva.

• Cellular Defenses:

• Macrophages

• Natural Killer (NK) cells

• Inflammation: A localized response to injury or infection.

• Fever: Elevated body temperature that can inhibit microbial growth.

Chemical Mediators:

Interferons

Complement system

critical process in innate immunity where cells engulf and digest foreign particles

Phagocytosis

five

steps are

Chemotaxis:

Adherence:

Ingestion:

Digestion:

Killing:

Movement of phagocytes towards the site of infection, guided by chemical

signals.

The phagocyte attaches to the surface of the foreign particle.

The phagocyte engulfs the particle, forming a vesicle called a phagosome

The phagosome fuses with a lysosome, forming a phagolysosome, where enzymes break down the particle.

The pathogen is destroyed.

Chemotaxis:

. Adherence

. Ingestion:

. Digestion

. Killing

The four cardinal signs of inflammation are:

1. Redness (Rubor)

2. Pain (Dolor)

3. Swelling (Tumor)

4. Heat (Calor)

Inflammation helps by 

diluting toxins, removing foreign materials and pathogens, and preparing

the tissue for repair

Inflammatory Response Stages

1. Vasodilation: Blood vessels widen, increasing blood flow to the injured area. This brings

antibodies, clotting factors, and other immune cells. Chemical mediators like histamine,

kinins, and prostaglandins are released.

2. Emigration: Phagocytes (neutrophils, then monocytes) move from the blood vessels into the

injured tissue, guided by chemotaxis.

3. Tissue Repair: Damaged tissue is replaced.

Adaptive immunity is characterized by its 

specificity for particular invaders and its ability to develop memory of encountered antigens.

Differentiate into plasma cells that produce antibodies. Associated with antibody-

mediated immunity.

B cells

Coordinate immune responses.

Directly kill infected cells.

Helper T cells (CD4+)

Cytotoxic T cells (CD8+):

B cells and Antibody-Mediated Immunity: B cells undergo ______.  to become

plasma cells (antibody factories) and 

Memory cells are crucial for a 

clonal selection ,memory B cells

 faster and stronger response upon re-exposure to the same antigen.

Play a central role in both cell-mediated and antibody-mediated immunity by activating other immune cells.

T Helper Cells (CD4+)

B and T lymphocytes develop unique antigen receptors on their surface during fetal development. This process is genetic, meaning

immunocompetence is pre-determined, not learned through antigen exposure.

Generation of Immunocompetence:

 Each lymphocyte has many

copies of one specific receptor, capable of binding to a single type of antigen.

 When an immunocompetent lymphocyte encounters its

specific antigen, it completes its differentiation into a fully functional immune cell (e.g., anactivated T cell or a plasma cell)

Antigen Encounter and Activation

Substances that can trigger an adaptive immune response (antigens) typically possess these

characteristics:

Foreign: Originating from outside the host.

Organic: Usually proteins or large polysaccharides.

Structurally complex.

Large molecular weight.

Antigens can have multiple unique regions called ________ that are recognized by immune cells.

epitopes 

primarily macrophages and dendritic cells, are essential

for initiating adaptive immunity. They engulf pathogens, process their antigens, and "present"

these antigens to T helper cells.

Antigen-Presenting Cells (APCs),

Adaptive Immunity: Activation Cascade

An APC engulfs and processes an antigen.

2. The APC presents the antigen fragments on its surface via MHC molecules to a helper T cell

(CD4+).

3. This antigen presentation activates the helper T cell.

4. Activated helper T cells then:

Activate cytotoxic T cells (CD8+) for cell-mediated immunity.

Activate B cells to produce antibodies for antibody-mediated immunity.

Cytotoxic T cells are the primary effectors of 

They directly recognize

 cell-mediated immunity

and kill infected cells, cancerous cells, or foreign cells (like transplanted tissue) that display

specific antigens

help regulate the immune response, and memory T cells

provide long-term immunity.

Suppressor T cells

are small proteins secreted by immune cells that regulate cellular activities

Cytokines

Examples

include:

Interferon: Primarily inhibits viral replication.

Interleukins: Influence lymphocyte and stem cell growth and differentiation.

Erythropoietin: Involved in red blood cell production (though its role in inflammation is

complex).

Tumor Necrosis Factor (TNF): Induces fever, apoptosis (programmed cell death), and

inhibits tumor growth and viral replication

Structure of Antibodies

Composed of two heavy chains and two light chains linked by disulfide bonds

 variable region at the tips of the "arms" is responsible for

 stem region (Fc region) determines

 antigen binding specificity.

antibody's class and f

unction.

Binding to and blocking the active sites of toxins or pathogens. This can also

lead to agglutination (clumping of cells) and precipitation (clumping of soluble antigens).

Triggering the complement system, a cascade of

that can lead to vasodilation, inflammation, and lysis (bursting) of the target cell.

blood proteins

Coating pathogens to enhance their recognition and engulfment by

phagocytes.

Neutralization:

Complement Activation

Opsonization

A key part of the complement system the MAC forms a pore in the plasma membrane of target

cells, leading 

cytolysis.

Cascade leading to C3b coating for opsonization and C5b-C9

forming the MAC.

Complement Activation:

Opsonization by C3b.

Phagocytosis Enhancement

Mast cell degranulation releasing histamine, increasing vascular permeability.

Inflammation

Pore formation by MAC leading to cell lysis.

Cytolysis:

the only class that crosses the placenta. Monomer with 2 binding

sites.

. IgG:Long-term immunity

The first antibody produced during a primary immune response. Activates complement

strongly. Pentamer with 10 binding sites.

IgM:

 Found in body secretions (saliva, tears, milk, GI fluids). Dimer.

 IgA: 

Primarily involved in allergic reactions and defense against parasitic worms.

 IgE:

Found on the surface of B cells; function is still being fully elucidated, likely involved in B

cell activation.

. IgD:

 the ability of the adaptive immune system to "remember" previous

encounters with specific antigens, leading to a faster and more potent response upon

subsequent exposures.

Immunological memory 

The body actively produces its own antibodies.

 Occurs after contracting a disease.

The body receives antibodies from an external source.

Active Immunity:

Natural Active

The body receives antibodies from an external source.

Passive Immunity:

 Antibodies transferred from mother to fetus/infant (placenta, breast

milk)

Natural Passive:

Administration of pre-formed antibodies (e.g., antivenom).

Artificial Passive

 Primarily targets intracellular pathogens, cancer cells, and

tissue transplants.

Cell-Mediated Immunity

Targets extracellular pathogens and toxins in body fluids.

Antibody-Mediated Immunity: 

 Found on the surface of almost all nucleated body cells.

They present fragments of intracellular proteins (including viral or bacterial antigens if the cell

is infected) to cytotoxic T cells. If a cytotoxic T cell recognizes a foreign antigen on MHC-I, it

triggers the destruction of the infected cell.

Class I MHC molecules (MHC-I)

Found primarily on Antigen-Presenting Cells (APCs)

like macrophages and dendritic cells. They present antigens derived from extracellular

pathogens to helper T cells (CD4+).

Class II MHC molecules (MHC-II)