Introduction to the Lymphatic System

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Questions and Answers

What is the primary function of lymph nodes in the lymphatic system?

To initiate blood clotting

To serve as filters for foreign substances (correct)

To produce antibodies

To transport lymph to the bloodstream

What type of cells are primarily produced by the lymphatic system to help fight infections?

Lymphocytes (correct)

Neutrophils

Platelets

Erythrocytes

Which statement about lymphatic vessels is true?

Lymphatic vessels have thick walls to withstand high pressure.

Lymphatic vessels transport lymph in multiple directions.

Lymphatic vessels contain numerous valves to prevent backflow. (correct)

Lymphatic vessels are primarily made up of smooth muscle.

What distinguishes the spleen as a secondary lymphoid organ?

It filters blood and stores lymphocytes. Signup and view all the answers

Which feature is NOT characteristic of lymphatic vessels?

They transport blood under high pressure. Signup and view all the answers

Which of the following best describes the role of macrophages within lymph nodes?

They engulf and destroy foreign particles. Signup and view all the answers

What is the primary role of antigen-presenting cells within the lymphatic system?

To present antigens to lymphocytes Signup and view all the answers

What are the primary functions of the lymph nodes?

Filtration of lymph and proliferation of lymphocytes Signup and view all the answers

What type of tissue does the spleen contain that is vital for its function?

Lymphatic tissue Signup and view all the answers

Which structure primarily contains T-lymphocytes in the spleen?

White pulp Signup and view all the answers

What type of lymphocyte is predominantly found in the germinal centers within lymph nodes?

Rapidly dividing B-lymphocytes Signup and view all the answers

What is the role of medullary cords in lymph nodes?

Arrangement of macrophages and plasma cells Signup and view all the answers

Which of the following describes the structure of the spleen?

Has a thick capsule and aggregates of lymphocytes Signup and view all the answers

What is the primary function of the red pulp in the spleen?

Removal of old red blood cells Signup and view all the answers

During which phase does the thymus regress?

Up to puberty Signup and view all the answers

What component of the thymus is involved in the maturation of lymphocytes?

Cortex Signup and view all the answers

Study Notes

Introduction to the Lymphatic System

The lymphatic system is made up of lymphatic vessels, lymphocytes, and lymphatic organs
It protects against invading pathogens by producing immune responses
The lymphatic capillaries, which form networks in most tissues, collect tissue fluid called lymph
The lymphatic capillaries unite to form larger vessels that drain into veins

Lymphatic System Components

Lymphatic Vessels: Body-wide network of thin-walled vessels with abundant lymphatic valves; walls made up of attenuated endothelium; drain into lymph nodes.
Cells:
- Lymphocytes: B Cells, T Cells, and natural killer cells
- Antigen-presenting cells: Dendritic cells, Langerhans’ cells, and macrophages
Lymphatic “Tissue”: Diffuse and nodular
Lymphatic “Organs”: Lymph nodes, spleen, and thymus

Functions of the Lymphatic System

Drains fluid into the bloodstream
Filters lymph
Filters blood
Helps fight infection by:
- Producing lymphocytes that create antibodies
- Housing macrophages in lymph nodes that engulf and kill foreign particles

Lymphoid Tissue

Primary Lymphoid Tissue/Organ: Where lymphocytes develop from lymphoid stem cells (e.g., thymus and bone marrow)
Secondary Lymphoid Tissue/Organ: Where formed lymphocytes are most active (e.g., spleen and lymph nodes)

Lymphatic Organs

Lymph Nodes

Small, bean-shaped structures along the path of lymph vessels that serve as filters for bacteria and other foreign substances
Several lymph vessels enter (afferents) the node on its convex aspect and a single or a few lymph vessels leave (efferents) the node through its hilum with blood capillaries
Structure:
- Outer fibrous capsule with trabaculae extending inward
- Subcapsular Sinus
- Cortex: Contains lymphoid follicles with pale staining germinal centers (containing rapidly dividing B-lymphocytes) and a rim of inactive B-lymphocytes
- Medulla: Lymphocytes arranged in branching cords along the sinuses (medullary cords); primarily composed of macrophages and plasma cells
Function:
- Filtration of lymph
- Proliferation of lymphocytes, contributing to the immune system

Spleen

Contains a significant amount of lymphatic tissue that filters blood, not lymph
Structure:
- Thick capsule that sends septa into the spleen
- White Pulp: Aggregation of lymphocytes around the central artery, composed of T-lymphocytes and lymphatic nodules with germinal centers (Malpighian bodies) containing B-lymphocytes
- Red Pulp: Major part of the spleen; contains lymphocytes arranged in branching and anastomosing cords along the sinusoids
Function:
- Removes old RBCs
- Produces lymphocytes
- Removes blood-borne antigens
- In fetal life, also serves as a site of erythrocyte production

Thymus

Primary lymphoid organ
Grows up to puberty and regresses in adulthood
Structure:
- Capsule sends incomplete septa into the parenchyma, dividing it into lobules
- Cortex: Contains densely packed small lymphocytes and macrophages for phagocytosis
- Medulla: Contains sparsely arranged larger lymphocytes and epitheliocytes; degenerated epitheliocyte cell aggregations appear as concentric eosinophilic masses called Hassall's corpuscles

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Description

This quiz covers the essential components and functions of the lymphatic system. Learn about lymphatic vessels, lymphocytes, and organs like lymph nodes and the spleen. Test your knowledge on how the lymphatic system helps protect the body against pathogens.