Lymph Node

Introduction:

• Shape

• Location

• What occurs to it during infection

Shape: Round, oval or bean shaped

Location: Along the course of blood vessels

During an infection: It enlarges making it easily palpated

What is the 4 functions of the lymph nodes?

• Produces lymphocytes and antibodies

• Filter the lymph

• Serve as a defense mechanism to prevent spread of malignant cells

• Represent potential haemopoetic organs (produce blood cells)

What is lymph?

Clear/yellowish fluid that circulates through the lymphatic system and contains:

• Water

• Proteins

• Lymphocytes (WBC)

• Fats

Describe the flow of lymph through a lymph node

Afferent lymph vessel:

• Lymph enters the lymph node through the afferent lymph vessels

• Where it carries antigens, pathogens and etc

Inward flowing lymph:

• Once inside, lymph flows through network of sinuses (subcapsular, trabecular and medullary sinuses)

• This allows immune cells to screen for harmful substances

Filtering process:

• Lymph passes through the cortex (where B cell are) and paracortex (where T cells are)

• Foreign substances are processed by immune cells

Efferent lymph vessel:

• Cleansed lymph exits the lymph node through efferent lymphatic vessel

• Where it is led to larger lymphatic trunks and eventually return lymph to bloodstream

What does the lymph node contain?

• Capsule #ff7000

• Afferent lymph node

• Subcapsular sinus #ffcc2a

• Hilus #00c2ef

• Efferent lymph vessels

• Trabeculae

• Petritrabecular sinuses

• Cortex #ae00ff

• Medulla #ff00ac

• Medullary cords

• Medullary sinuses

Structure of Lymph Node: Capsule

• What is it made of

• Function

Made of: Dense irregular CT such as

• Collagenous fibers

• Elastic fibers

• Fibroblast

• Smooth muscle fiber (sometimes)

Function: Provides structure and protection

Structure of Lymph Node: Afferent Lymph Vessels

• Function

• Lined by

• Surrounded by

• Contain valves?

Function: Carry lymph to the lymph node

Lined by: Epithelium

Surrounded by: Thin layer of CT

Contain: Valves

Structure of Lymph Node: Subcapsular sinus

• What

• Location

• Function

• What extends across the sinus?

What: Lymphatic sinus

Location: Below the capsule

Function: Represents the site of termination of the afferent lymph vessels

What extends across the sinus: Loose network of cells and fibers

Structures of Lymph Node: Hilus

• What

• Contains

What: Slight indentation on one side of node

Contains: Blood vessels, nerves and efferent lymph vessels

Structure of Lymph Node: Efferent Lymph Vessels

• What

• Function

• Distribution compared to afferent lymph vessels

• Diameter compared to afferent lymph vessels

• As they leave the node, what does it pierce

• Do they have valves?

What: Open-ended thin walled tubes within lymph node

Function: Carry lymph out from the lymph node

Distribution compared to afferent lymph vessels: Fewer in number

Diameter compared to afferent lymph vessels: Larger

As they leave the node, what does it pierce: Hilus

Do they have valves: Yes

Structure of Lymph Nodes: Trabeculae

• What

• Location

• Function

• Contain

What: Projections of CT which extend from the capsule

Location: Straight in the cortex and branched in the medulla

Function: Separate the cortex into incomplete compartments

Contain: Blood vessels

Structure of Lymph Nodes: Peritrabecular Sinuses

• AKA

• Identified as

• Location

AKA: Trabecular sinuses

Identified as: Areas of diffuse lymphatic tissue

Location: Next to trabeculae

Structure of Lymph Node: Cortex

• What

• Contain

  • Types

What: Outer zone of the lymph zone

Contain: Lymphatic nodules that are either

• Active (posses a corona and a germinal center)

• Inactive

Structure of Lymph Node: Medulla

• What

• Are there lymphatic nodules present?

What: Inner zone

Are there lymphatic nodules present: No

Structure of Lymph Node: Medullary Cords

• What

What: Strands of dense lymphatic tissue

Location: Which extend from lymphatic nodules of the cortex into the medulla

Structure of Lymph Nodes: Medullary Cords

• What

What: Areas of loose lymphatic tissue in the medulla which lie between the medullary cords and trabecular