FHA - Lymphatic System

Two Major Systems Lymphatic System Takes Part In

Circulatory system and immune system

Type of Connective Tissue of Lymph

Fluid connective tissue

Lymph Comes From

Interstitial fluid

Specialized Cells in Lymph

Lymphocytes and macrophages

Three Main Components of Lymphatic System

Lymph, lymphatic vessels, lymphatic tissues/organs

Lymphatic Vessels

A network of vessels that transport lymph through tissues and back to venous circulation

Lymph Nodes

Small nodules containing lymphocytes; act as filters for lymph

Lymph Nodes in Human Body

~600.

Major Lymphatic Organs

Tonsils, thymus, spleen, MALT, appendix, red bone marrow

MALT

Mucosa‑associated lymphatic tissue lining digestive, respiratory, urinary, and reproductive tracts

Largest Lymphatic Organ

Spleen

Spleen Function

Filters blood, removes old RBCs, removes pathogens, regulates blood cell levels

Appendix Function

Lymphatic organ; may be vestigial

Red Bone Marrow Produces

RBCs, WBCs, platelets; produces B cells and T cell precursors

Two primary Lymphatic Organs

Thymus and red bone marrow

Thymus Produces (what hormone)

Thymosin

Thymosin

Helps T cells mature

Thymus Most Active

Childhood → puberty

Thymus After Puberty

Shrinks and becomes fatty tissue

Major Functions of Lymphatic System

Produce/maintain/distribute lymphocytes; maintain blood volume; return excess fluid; absorb fats; provide alternate transport route

Primary Transporter of Hormones/Nutrients/Waste

Circulatory system (blood)

Cause of Fluid Leaving Blood Capillaries

Systemic capillary pressure (~35 mmHg).

State of Fluid After Leaving Blood Capillaries

Becomes interstitial fluid → enters lymphatic capillaries

Lymphatic Capillaries vs. Blood Capillaries

Larger diameter, thinner walls, irregular outline, overlapping endothelial cells, anchoring filaments

Lymphatic Capillaries Permeability

Overlapping endothelial cells create openings

Lymphatic Capillaries Not Found In

CNS, bone marrow, epidermis

Cause of Lymph to Move in One Direction

One‑way valves

Lymph Flow Similarity

Venous return (low pressure + valves)

Two Major Lymphatic Ducts

Thoracic duct and right lymphatic duct

Thoracic Duct Drains Lymph From

Both sides below diaphragm + left side above diaphragm

Right Lymphatic Duct Drains Lymph From

Right side of head/neck, right thorax, right upper extremity

Location Both Ducts Empty Lymph

Into the superior vena cava → right atrium

Cisterna Chyli

Enlarged sac collecting lymph from abdomen → drains into thoracic duct

Primary Cells of Lymphatic System

Lymphocytes

Lymphocytes Respond To

Bacteria, viruses, cancer cells, foreign proteins, toxins

Lymphocytes Origination

Red bone marrow

Lymphopoiesis

Formation of lymphocytes

T Cells Reason For Being Called T Cells

They mature in the thymus

Four Types of T Cells

Cytotoxic T cells, helper T cells, regulatory T cells, memory T cells

T Cells Function

Directly attack infected or abnormal cells

Cell Mediated Immunity

T cells directly attack pathogens or abnormal cells

Location B Cells Mature

Bone marrow

B Cells Mature Into

Plasma cells and memory B cells.

Plasma Cells Produce

Antibodies (immunoglobulins)

Antibody Mediated Immunity

B cells produce antibodies that bind and deactivate antigens

Immunizations Reason For Working

Memory B cells remember antigens for future immunity

NK Cells Function

Attack foreign cells, virus‑infected cells, and cancer cells.

Cell Mediated Immunity Effective Against

Cancer cells, infected cells, transplanted cells

Antibody Mediated Immunity Effective Against

• Cannot fight against cancer

• Extracellular pathogens

Lymphoma

Cancer of the lymphatic system (Hodgkin’s & non‑Hodgkin’s)

Leukemia

Cancer of blood‑forming tissues affecting lymphatic function

Reason Cancers Spread Via Lymph Nodes

Lymph nodes filter fluid and can carry metastasizing cells

Autoimmune Disease

Immune system attacks healthy cells

Examples of Autoimmune Disease

Lupus, rheumatoid arthritis

Lymphedema

Localized swelling due to blocked or damaged lymph vessels/nodes

Causes of Lymphedema

Compression/blockage of lymph vessels, node removal, injury

Edema

Swelling due to trapped fluid in tissues

Treatment to Help Lymphedema

Kinesio taping + therapeutic drainage

T and B Cells with Age

Decrease in number and function

Thymus with Age

Shrinks → becomes fatty tissue by age 75–80

Elderly Individuals More Susceptible To

Disease, weaker vaccine response, increased cancer incidence