lymphatic/ immune metacognition

What is the lymphatic system?

• a network of conduits that carry a clear fluid 

called lymph

What is lymph?

the fluid that has escaped from the blood vessels

Where does lymph get returned?

Returns back to the bloodstream

What are 3 roles of the lymphatic vessels?

• Provide a means by which disease organisms and diseased cells travel throughout the body 

• Which transport fluid and proteins that has escaped from capillaries back to the heart

• Carries absorbed fat from the intestine to blood

What are 5 lymphoid organs?

spleen, thymus, lymph nodes, tonsils, and appendix

List the correct order of lymphatic vessels in order going towards the heart.

• Lymph capillaries: smallest; first receive lymph

- Lymphatic collecting vessels: collect lymph from capillaries; have valves

- Lymph nodes: scattered along collecting vessels

- Lymph trunks: collect lymph from collecting vessels

- Lymph ducts: empty into veins of the neck

What are lymph capillaries?

they are closed-end vessels whose walls consist of single layer of endothelial cells

 Where do lymph capillaries receive tissue fluid from?

Receive tissue fluid from C.T. and are extremely permeable

What does an increased volume of tissue fluid cause? 

Increased volume of tissue fluid causes leaked blood (lymph fluid) to enter lymph capillaries through minivalve flaps that open and allow fluid to enter

What does high permeability of lymph capillaries allow?

Uptake of tissue fluid and entrance of bacteria, viruses, and cancer cells

1. What are lacteals?

specialized lymphatic capillaries located in the villi of the small intestines that receive digested fats (fatty lymph) called chyle

What directs the flow of lymph?

Valves

What are 3 mechanisms that propel lymph?

Lymph propelled by a series of mechanisms: 

a) Bulging of skeletal muscles 

b) Pulsing of nearby arteries

c) Tunica media of the lymph vessels

Describe lymph nodes. How many are there in the body?

• bean-shaped organs located along lymphatic collecting vessels that cleanse the lymph of pathogens.

• Human body contains approximately 500 

• Lymph nodes are organized in clusters: cervical, axillary, and inguinal regions

What is the flow of lymph through a lymph node?

Afferent lymphatic vessels -> lymph sinuses->efferent lymphatic vessels

 The lymph sinuses are spanned by what?

-by a network of reticular fibers covered by 

endothelial cells

What houses macrophages?

The lymph sinuses are spanned by a network of reticular fibers covered by endothelial cells, which house many macrophages that consume pathogens and foreign particles in the lymph.

What is the difference between the thoracic duct and the right lymphatic duct?

• Thoracic duct: Ascends along vertebral bodies and empties into venous circulation at the junction of left internal jugular and left subclavian veins; drains three quarters of the body/ Found in all people

•  Right lymphatic duct: Empties into right internal jugular and subclavian veins-Present in ~ 20% of people

What are 3 functions of lymphatic vessels? In addition, lymph nodes also fight what?

1) Return excess tissue fluid to the bloodstream

2) Return leaked proteins to the blood

3) Carry absorbed fat from the intestine to the blood (though the lacteals)

• lymph nodes fight disease in their roles as lymphoid organs of the immune system

20. What do T cells attack? How?

• T cells (killer T-lymphocytes): attack foreign eukaryotic cells directly; bind to antigen-bearing cells and punch holes in its membrane…which triggers apoptosis

What do B cells become? What do they then secrete? What do they attack?

• B cells: multiply to become plasma cells that secrete antibodies (proteins that mark specific antigens for destruction by macrophages); mostly attack bacteria and bacterial toxins

Where is lymphoid tissue found?

Two general locations:

1) Mucous membranes of digestive, urinary, respiratory, and reproductive tracts, where it is called Mucosa-associated lymphoid tissue (MALT)

2). In all lymphoid organs except the thymus

What white blood cells are housed in lymphoid tissue?

lymphocytes

What are the primary and secondary lymphoid organs?

-Primary lymphoid organs: bone marrow (where B lymphocytes mature), and thymus (where T  lymphocytes mature)

-Secondary lymphoid organs: lymph nodes, spleen, tonsils, lymphoid nodules in small intestine, and appendix

What are 2 things that happen in the thymus?

• Where immature lymphocytes develop into T lymphocytes

•  Secretes thymic hormones (cause immunocompetence)

When is the thymus active?

• Most active in childhood and the functional tissue atrophies with age and is replaced with fibrous and fatty tissue

What is happening in the cortex of the thymus?

• The cortex is packed with rapidly dividing T lymphocytes gaining immunocompetence.

What challenges happen in lymph nodes?

• Most antigenic challenges occur in lymph nodes, where not only are antigens destroyed but also activate B and T lymphocytes

What are 2 functions of the spleen? What is the spleen the site of?

• Two main functions:

1) Removal of blood-borne antigens

2) Removal and destruction of old/defective blood cells by macrophages

Also…site of hematopoiesis in the fetus and stores platelets throughout life

What is the function of the appendix?

Functions: destroys microorganisms that enter them; generate a wide variety of memory lymphocytes to protect the body