29 - Lymphatic Tissues

Question 1

What does the lymphatic system consist of?

Answer 1

Lymphatic system

• Consists of cells, tissues and organs which collectively form the body’s immune/defense system

Question 2

What is the role of the lymphatic system?

Answer 2

Protects the body from antigens, pathogens, bacteria and viruses

Question 3

Describe lymphocytes

Answer 3

Lymphocytes

• Lymphatic tissues are very cellular and contain large numbers of lymphocytes
• There are two types of lymphocytes
  
  • T lymphocytes
  • B lymphocytes
• You cannot tell the difference between the two types of lymphocytes using conventional staining
• Special stains can differentiate between lymphocyte cell types
  
  • Example: we know there are B lymphocytes in the tonsils because of a special staining technique

Question 4

How do we classify lymphatic tissues?

Answer 4

Classifications

• Primary lymphatic tissues
• Secondary lymphatic tissues

Question 5

Where do you find primary lymphatic tissues? What is the function of these tissues?

Answer 5

There are two types of primary lymphatic tissue

• Bone marrow
• Thymus

The function of these primary lymphatic tissues is to…

• Function as the site of development and maturation of lymphocytes into immunocompetent cells
• These cells “seed” the secondary lymphatic tissues with lymphocytes

Question 6

Where are secondary lymphatic tissues located? What is their function?

Answer 6

Secondary lymphatic tissues - three types:

• Lymph nodes
• MALT - mucosa associated lymphatic tissue
• Spleen

Functions of secondary lymphatic tissues

• Site of formation of the immunological defense against antigens or pathogens
• Confrontation with antigens or pathogens occurs here

Question 7

What is the role of the lymph nodes?

Answer 7

Filter lymph

Question 8

What is the role of MALT? What are the four varieties?

Answer 8

MALT

• Mucosa associated lymphatic tissue
• Functions in **surveillance **
• There are four varieties
  
  1. GALT - gut associated lymphatic tissue
     
     1. Located in the lamina propria of the GI tract
  2. BALT - bronchus associated lymphatic tissue
     
     1. located in the lamina propria of the respiratory tract (i.e. the bronchi)
  3. GU tract
     
     • Found in the lamina propria of the genitourinary tract
  4. Tonsils

Question 9

What is the function of the spleen?

Answer 9

Spleen

• Filters blood
• The spleen is the largest lymphatic organ
• Contains secondary lymphatic tissue

Question 10

What is the lamina propria? Where is it located? What is its function?

Answer 10

Lamina propria

• Latin for “first layer”
• The lamina propria is comprised of loose connective tissue that is located just inside the epithelium
• The lamina propria is the location of lymphatic tissue
  
  • GALT is found in clusters in the lamina propria
  • This protects the body from antigens and microorganisms that present in the lumen of the GI tract

Question 11

What is diffuse lymphatic tissue? What cell types are found in this tissue?

Answer 11

Diffuse lymphatic tissue

• Diffuse lymphatic tissues can be seen infiltrating the lamina propria of the appendix, for example
• Pathogens can penetrate the epithelium of the appendix and end up in the lamina propria
• These lymphatic cells are here to deal with the attachers

Cell types seen in diffuse lymphatic tissues

• Lymphocytes
• Monocytes
• Macrophages (phagocytic)
• Plasma cells

Question 12

What are lymphatic nodules? What are the two types of lymphatic nodules?

Answer 12

Lymphatic nodules

• Lymphatic nodules are a little more complex than diffuse lymphatic tissues, but have a similar purpose
• There are two types
  
  • Primary lymphatic nodules
  • Secondary lymphatic nodules