Chapter 22: Lecture 1 - Introduction to the Lymphatic System

Key Concepts

• Resistance and Susceptibility
  • Resistance: Ability to ward off pathogens
  • Susceptibility: Lack of resistance
  • Types of resistance:
    • Nonspecific resistance: Innate defenses present at birth
    • Specific immunity: Activation of specific lymphocytes to combat particular pathogens

Lymphatic System Overview

• Components:
  • Lymph
  • Lymphatic vessels
  • Lymphatic tissues
  • Lymphatic organs
• Functions:
  1. Drains interstitial fluid and returns plasma proteins to blood
  2. Transports dietary fats via lacteals
  3. Protects against invasive threats through immune responses

Lymph

• Similarity to interstitial fluid:
  • Difference lies in location:
    • Lymph: Within lymphatic vessels
    • Interstitial fluid: Between cells

Gross Anatomy of the Lymphatic System

• Lymphatic organs and tissues:
  • Red bone marrow
  • Spleen
  • Thymus
  • Lymph nodes
  • Diffuse lymphatic tissue (tonsils, adenoids, Peyer's patches)
• Lymphatic vessels:
  • Travel alongside veins and arteries
  • Lymphatic capillaries merge into larger vessels, which have valves to prevent backflow

Lymphatic Circulation

• Lymphatic Capillaries:
  • Blind-ended
  • Endothelial cells act as one-way valves
  • Anchored by filaments to prevent collapsing
• Lacteals:
  • Specialized capillaries in the small intestine
  • Transport digested fats

Lymphatic Drainage

• Drainage System:
  • Right lymphatic duct drains a portion of the right side of the body
  • Thoracic duct (left side) drains the majority of the body
  • Lymph drains into subclavian veins

Mechanism of Lymph Movement

• Aids in lymph movement:
  • Skeletal muscle contraction
  • Respiratory movements
  • Valves preventing backflow

Potential Issues

• Edema:
  • Caused by excessive filtration or insufficient reabsorption
  • Indicates possible lymph flow obstruction

Lecture Goals

• Define key terms:
  • Resistance, susceptibility, nonspecific resistance, specific immunity, lacteals, chyle
• Describe lymph composition
• Identify functions of the lymphatic system
• List lymphatic organs and tissues
• Describe lymphatic capillary structure and function
• Trace lymph flow to subclavian veins
• Understand differences in lymph drainage between right and left subclavian veins