Lymphatic System Lecture Notes

Overview

• Also known as: Immune System
• Main Functions:
  • Transporting excess tissue fluid back to the bloodstream
  • Defending the body against disease by filtering body fluids
  • Absorbing fats (lipids) from the digestive system

Key Functions

Fluid Transport

• Lymphatic vessels transport excess tissue fluid away from tissues and back to the bloodstream.
• Acts as a backup to capillary exchange, dealing with excess fluid not reabsorbed by blood capillaries.

Immune Defense

• Filters bacteria, viruses, and dead cells from body fluids.
• Lymphocytes (immune cells) play a critical role.

Lipid Absorption

• Absorbs large lipid molecules from the intestines that cannot directly enter blood capillaries.
• Lipids are transported through the lymphatic system and eventually dumped into the bloodstream.

Lymphatic Pathways

• Similarities to cardiovascular system:
  • Pathways and structures resemble blood vessels.
• Thoracic duct: Major lymphatic vessel that dumps lymph into the blood near the left clavicle.
• Lymph vessels: Have dead ends, unlike the circulatory system's closed loop.

Lymphatic Tissues

• Types of Tissue: Loose areolar connective tissue (collagen, elastin, lymphocytes).
• Common Locations: Appendix, tonsils, spleen, lymph nodes.

Lymph Nodes

• Functions:
  • Filtration of lymph to detect and destroy harmful substances.
  • Contain lymphocytes and macrophages.
• Locations: Armpit, groin, mammary glands.
• Importance: Have numerous nodes (600-700 total), can function without some.

Lymph Movement

• No heart pump: Moves via muscle contractions and thoracic pressure differences.
• Key Processes:
  • Skeletal muscle contractions assist lymph movement.
  • Formation of new lymph pushes old lymph through vessels.

Comparison with Blood

• Lymph vs. Blood:
  • Lymph moves slowly (3 liters/day vs. blood's 5 liters/minute).
  • Lymphatic capillaries have larger molecules and one-way valves.

Major Lymphatic Organs

Thymus

• Location: Behind sternum
• Function: Converts lymphocytes into T lymphocytes.

Spleen

• Largest lymphatic organ: Filters blood, stores blood, destroys old red blood cells.
• Functions: Hosts macrophages and lymphocytes.

Tonsils

• Types and Locations:
  • Palatine (back of throat)
  • Pharyngeal (adenoids, nasal area)
  • Lingual (back of tongue)
• Role: Filters inhaled and ingested pathogens.

Appendix

• Function: Unclear, vestigial organ.
• Role in Immunity: Possible historical role in aiding digestion and immunity.

Conditions Related to Lymphatics

Edema

• Causes:
  • Immobility, heat, excess salt intake, heart failure, kidney disease.
• Mechanism:
  • Excess fluid in tissues due to poor reabsorption or fluid transport issues.

Summary

• The lymphatic system is crucial for fluid balance, immune defense, and nutrient absorption.
• It works alongside the cardiovascular system but has unique properties and functions.