The Lymphatic System can be compared to the sewer system of the body.
Drains excess fluids and discards unwanted substances.
Serves as a navigation route for defense forces (immune cells) aside from the bloodstream.
Main components:
Lymphatic Vessels
Lymphatic Organs: Includes lymph nodes, spleen, and thymus.
Lymphatic Tissue: Includes tonsils, appendix, and Peyer’s patches.
Regulation of Interstitial Fluid Volume
Interstitial fluid accumulates due to unequal hydrostatic and osmotic pressure leading to about 2-4 liters lost daily.
Lymphatic vessels collect excess interstitial fluid, which becomes lymph.
Lymph and interstitial fluid share a similar composition.
Lymphatic vessels transport excess fluid back to circulation, thereby preventing hypotonic blood.
Absorption of Dietary Fats
Fats from the small intestine, broken down during digestion, are unable to pass through capillaries.
They enter lymphatic vessels called lacteals and eventually get returned to the bloodstream.
Immune Functions
Lymphoid organs filter pathogens and house leukocytes for immune response.
Lymphatic vessels aid in mobilizing the immune system through pathways that complement the bloodstream.
Lymph nodes serve as sites where white blood cells (especially lymphocytes) reside before activation in response to infections.
Structures are similar to blood vessels serving a network for lymph circulation.
Lymph is formed from excess interstitial fluid and has various components including water, proteins, fats, leukocytes, waste, and pathogens.
Composition of Lymph:
Made from water, proteins, fats, leukocytes, waste products, and damaged cells gathered from tissues.
Vessel Structure:
Lined by endothelium (simple squamous).
Walls allow flaps for larger fluid and cell entry, therefore functioning as a one-way system toward lymph nodes.
Afferent vs. Efferent Lymphatic Vessels:
Afferent: Carry lymph from tissues to lymph nodes.
Efferent: Carry lymph away from lymph nodes to major vein junctions returning lymph to the bloodstream.
Function as checkpoint stations in the lymphatic system.
Key clusters found in axillae, neck, groin, and abdominal cavity.
Rich in lymphocytes (B-cells in cortex, T-cells in the middle, and macrophages in the medulla).
Serve as filtering points for pathogens and sources of lymphocyte activation.
Lymph-collecting vessels form larger trunks:
Nine Major Trunks include lumbar, jugular, and broncho-mediastinal trunks.
Two Primary Ducts: Thoracic Duct (drains left upper and lower body) and Right Lymphatic Duct (drains right upper body).
Movement of Lymph:
Circulation relies on the contraction of surrounding muscles and the pressure of nearby arteries, lacking direct pumping force.
Skeletal muscle movements aid lymph propulsion, underscoring the importance of physical activity in maintaining flow.
Normal Flow: Ensures tissue hydration and nutrient delivery through lymphatic vessels.
Obstructed Flow: Results in conditions like lymphedema characterized by fluid retention in tissues.
Commonly signify infection; lymphocyte proliferation causes node swelling indicating immune activation.
Primarily composed of reticular tissue, lymphocytes (B-cells, T-cells), phagocytes, and reticular cells.
Found in mucous membranes of the body, helping trap pathogens.
Key Locations include:
Gastrointestinal Tract: Peyer’s patches, tonsils, and appendix.
Genitourinary Tract: Limited presence in kidney and urethra areas.
Respiratory Passages.
Tonsils and Peyer's Patches are significant components of MALT and respond to oral and nasal pathogens through lymphocyte production.
Largest lymphoid organ located in abdominal cavity.
Functions in filtering blood, removing old erythrocytes, and pathogen filtering.
Contains:
Red Pulp: Destroys erythrocytes.
White Pulp: Contains leukocytes for pathogen clearance.
Located in the superior mediastinum, crucial for T-cell maturation.
Undergoes positive and negative selection processes ensuring proper immune function.
Maximal size around ages 12-14; reduces and replaces with fat over time, though it does not compromise overall immunity significantly.
The Lymphatic System plays essential roles in fluid regulation, fat absorption, and immune function, essential for general health.