Lymphatic System and Immunity Overview

Overview of Immunity

• Immunity is the ability to defend against damage or disease; susceptibility refers to vulnerability.
• Two primary types of immunity:
  • Innate (nonspecific) immunity is present at birth and does not target specific microbes.
  • Adaptive (specific) immunity involves specific recognition and response to particular pathogens with the involvement of lymphocytes (T cells and B cells).

Innate Immunity

• First line of defense includes physical and chemical barriers like skin and mucous membranes.
• Second line involves antimicrobial substances, natural killer cells, phagocytes, inflammation, and fever.
• Functions as an early warning system to prevent microbial invasion.

Adaptive Immunity

• Engages after innate defenses are breached.
• Involves a tailored response to specific pathogens, adapting based on prior exposure.

Lymphatic System Overview

• Lymphatic system plays a crucial role in homeostasis by draining interstitial fluid and providing disease defense mechanisms.
• Lymph plasma is the fluid found within lymphatic vessels, while interstitial fluid exists between cells.

Lymphatic Vessels

• Lymphatic capillaries begin the lymphatic vessel network, closed at one end; unique one-way structure allows fluid entry but prevents backflow.
• Lymphatic vessels are similar to veins but have thinner walls and more valves.
• Certain tissues like cartilage, epidermis, and cornea lack lymphatic capillaries.

Lymphatic Trunks and Ducts

• Lymph flows from lymphatic vessels, merging into lymphatic trunks, then into larger ducts.
• Major lymphatic trunks include:
  • Lumbar Trunks (lower limbs, pelvic viscera).
  • Intestinal Trunk (abdominal organs).
  • Bronchomediastinal Trunk (thoracic wall, lungs, heart).
  • Subclavian Trunk (upper limbs).
  • Jugular Trunk (head and neck).

Thoracic Duct and Right Lymphatic Duct

• Thoracic duct is the primary vessel for lymphatic return on the left side, measuring 38–45 cm.
• Right side lymphatic trunks typically open individually into the venous system.

Thymus

• Bilobed organ in the mediastinum, between sternum and aorta, with high lymphoid tissue content.
• Ages, it undergoes fatty infiltration, changing from red to yellowish appearance.

Lymph Nodes

• Approximately 600 lymph nodes around lymphatic vessels, functioning as filters for foreign substances.
• Each node has lymphoid nodules that contribute to immune responses.
• Tonsils are specialized lymphoid masses that also help in defense against ingested or inhaled pathogens.

Spleen

• Largest lymphatic tissue mass in the body, located in the left hypochondriac region.
• White pulp in the spleen carries out immune functions similar to lymph nodes.
• Red pulp has three main functions: removal of defective blood cells, storage of platelets, and hemopoiesis during fetal development.

Lymphatic Circulation

• Begins in closed-ended lymphatic capillaries, where interstitial fluid becomes lymph plasma.
• Lymphatic flow follows a route from capillaries to vessels, trunks, ducts, and finally to subclavian veins.
• Skeletal muscle contractions, respiratory movements, and valves facilitate lymph plasma flow.

This quiz explores the basics of the lymphatic system and the concept of immunity. It covers the definitions of immunity and susceptibility, along with the two types of immunity: innate and adaptive. Enhance your understanding of how the body defends against diseases.