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Lymphatic System: Components, Functions, and Anatomy, Lecture notes of Anatomy

An overview of the lymphatic system, including its components, functions, and anatomy. It covers the formation and flow of lymph, primary and secondary lymphatic organs and tissues, and disorders of the lymphatic system. The document also describes the anatomy of the thymus, lymph node, and spleen, as well as the lymphatic nodules. It explains the difference between interstitial fluid and lymph and the functions of the lymphatic system, such as removal of excess fluids, transport of dietary lipids, and immune responses.

Typology: Lecture notes

2021/2022

Available from 01/05/2023

Dr_Raihan
Dr_Raihan 🇮🇳

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Lymphatic system
Objectives
At the end of this lecture, student will be able to
• List the components of the lymphatic system
• Explain major functions of the lymphatic system
• Describe the organization of lymphatic vessels
• Explain the formation and flow of lymph
• Differentiate the primary and secondary lymphatic organs and tissues
• Explain the anatomy of thymus and lymph node
• Describe the anatomy of spleen
• List the lymphatic nodules
• Discuss the disorders of Lymphatic system
Content
• Components of lymphatic system
• Lymphatic ducts and trunks
• Formation and flow of lymph
• Primary and secondry lymphatic organs
• Spleen
• Lymphatic nodule
• Disorders
Lymphatic System
• Consists of
– A fluid called lymph
– Vessels - lymphatic vessels
• Lymphatic tissue
– Specialized form of reticular connective tissue
– Contains large numbers of lymphocytes
– B cells and T cells (Adaptive immunity)
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Lymphatic system

Objectives

At the end of this lecture, student will be able to

  • List the components of the lymphatic system
  • Explain major functions of the lymphatic system
  • Describe the organization of lymphatic vessels
  • Explain the formation and flow of lymph
  • Differentiate the primary and secondary lymphatic organs and tissues
  • Explain the anatomy of thymus and lymph node
  • Describe the anatomy of spleen
  • List the lymphatic nodules
  • Discuss the disorders of Lymphatic system

Content

  • Components of lymphatic system
  • Lymphatic ducts and trunks
  • Formation and flow of lymph
  • Primary and secondry lymphatic organs
  • Spleen
  • Lymphatic nodule
  • Disorders

Lymphatic System

  • Consists of
  • A fluid called lymph
  • Vessels - lymphatic vessels
  • Lymphatic tissue
  • Specialized form of reticular connective tissue
  • Contains large numbers of lymphocytes
  • B cells and T cells (Adaptive immunity)

Blood Plasma to Lymph

Difference between interstitial fluid and lymph is location

Functions of Lymphatic System

- Removal of excess fluids

  • Lymphatic vessels drain excess interstitial fluid from tissue spaces
  • Transports dietary lipids
  • Transport lipids and lipid-soluble vitamins (A, D, E, and K) absorbed by GIT
  • Carries out immune responses
  • Initiates high specified responses
  • Directed against particular microbes or abnormal cells

Lymphatic vessels

- Lymphatic Capillaries

  • Located in the spaces between cells
  • Closed at one end
  • Unite to form larger lymphatic vessels
  • Resemble veins in structure
  • Thinner walls and more valves
  • At intervals, lymph flows through lymph nodes

Lymph Trunks and Ducts

Lymph passes from lymphatic capillaries into lymphatic vessels, then through lymph nodes in a particular region of the body Unite to form lymph trunks

The Principal Trunks

  • Lumbar
  • Intestinal
  • bronchomediastinal
  • Subclavian
  • Jugular trunks

Lymph Trunks

  • The lumbar trunks
  • Drain lymph from the lower limbs, viscera of the pelvis
  • Kidneys, adrenal gland abdominal wall
  • The intestinal trunk
  • drains lymph from the stomach, intestines
  • Pancreas, spleen, and part of the liver
  • The bronchomediastinal
  • Trunks drain lymph from the thoracic wall, Lung, heart
  • The subclavian trunks - Drain the upper limbs
  • The jugular trunks - Drain the head and neck

Lymph Ducts

  • Lymph passes from lymph trunks into two main channels:
  • The thoracic duct
  • The right lymphatic duct The Right Lymphatic Duct
  • Receives lymph from the upper right side of the body The Thoracic Duct
  • Main duct for the return of lymph to blood

Thoracic Duct

  • Begins as a dilation called the cisterna chyli
  • Receives lymph from the left side of the head, neck, and chest, the left upper limb, and the entire body inferior to the ribs
  • Drains lymph into venous blood at the junction of the left internal jugular and left subclavian veins

Flow of Lymph- Respiratory Pump

  • During inhalation - Lymph flows from the abdominal region to thoracic region
  • During exhalation - The valves

Lymphatic Organs and Tissues

Primary lymphatic organs

  • Stem cells divide and become immuno competent - capable of mounting an immune response
  • Organs
  • Red bone marrow
  • Thymus

The secondary lymphatic organs and tissues

  • The sites where most immune responses occur
  • Lymph nodes
  • Spleen
  • Lymphatic nodules (follicles)

Red Bone Marrow

  • Pluripotent stem cells in red bone marrow give rise to mature:
  • immuno competent B cells
  • Pre-T cells

Thymus

Fate of T Cells

  • T cells that leave the thymus via the blood
  • Migrate to:
  • Lymph nodes
  • Spleen
  • Other lymphatic tissues
  • Colonize parts of those organs and tissues

Lymph Nodes

  • Located along lymphatic vessels - 600 bean-shaped lymph nodes
  • Scattered throughout the body superficial and deep (in groups)
  • Large groups of lymph nodes - Near the mammary glands and in the axillae and groin
  • Small, round or oval structures located along the pathways of lymph vessels

Lymph Node - Anatomy

  • Lymph nodes are 1–25 mm long
  • Covered by a capsule of dense connective tissue - Stroma
    • The capsule, trabeculae, reticular fibers, and fibroblasts - Supporting network:
  • Internal to the capsule
  • Reticular fibers, and fibroblasts - Trabeculae:
  • Divide the node into compartments & provide support
  • Provide a route for blood vessels into the interior of a node

The Parenchyma (Functioning Part)

 Superficial cortex  Deep medulla

  • Covered by a serous membrane - the visceral peritoneum
  • Trabeculae extend inward from the capsule.
  • Stroma: The capsule, trabeculae, reticular fibers & fibroblasts

Internal Structure of Spleen

Parenchyma: 2 types of tissue white pulp and red pulp

White Pulp

  • Lymphatic tissue – consisting mostly of lymphocytes and macrophages
  • Arranged around central arteries
  • Blood flow – to the splenic artery enters the central arteries Red Pulp
  • Consists of:
  • Blood-filled venous sinuses
  • Cords of splenic tissue called splenic (Billroth’s) cords
  • Veins are closely associated with the red pulp - Splenic cords Consist of:
  • Red blood cells
  • Macrophages
  • Lymphocytes
  • Plasma cells
  • Granulocytes

Internal Structure of Spleen

  • Within the white pulp
  • B cells and T cells carry out immune responses
  • Macrophages destroy blood-borne pathogens by phagocytosis - Within the red pulp
  • Macrophages: Removed raptured, worn out, or defective blood cells and platelets
  • Storage of platelets
  • Production of blood cells (hemopoiesis) during fetal life

Lymphatic Nodules

  • Egg-shaped masses of lymphatic tissue
  • Not surrounded by a capsule.
  • Scattered throughout the lamina propria of mucous membranes lining:
  • GIT
  • Urinary and reproductive tracts
  • Respiratory airways
  • MALT - Mucosa-associated lymphatic tissue
  • Many lymphatic nodules are small and solitary
  • Some lymphatic nodules occur in multiple large aggregations in specific parts of the body
  • Tonsils in the pharyngeal region strategically positioned to participate in immune responses
  • The aggregated lymphatic follicles (Peyer’s patches) in the ileum

Nonspecific and Specific Defenses

  • Immunity involves nonspecific and specific defenses Nonspecific defenses
  • Include barriers to entry, the inflammatory reaction, NK cells & protective proteins