Chapter 20: Lymphatic System/Lymphoid Organs

Lymphatic System:

(i) Returns fluids that have leaked from the CVS back to blood (ii) Return leaked proteins to the blood.

(iii) Carry absorbed fat from the intestine to the blood (lacteals)

Lymphatic System: lymphatic vessels

Network of BLANK (lymphatics)

Lymphatic System: Lymph

fluid in lymphatic vessels.

Lymphatic System: lymph nodes:

cleanse lymph as it passes through them 

Lymphatic System: Lymphoid Organs and Tissues:

Provide structural basis of immune system.

lymphoid Organs and Tissues Structures are..

lymph nodes, spleen, thymus, tonsils, Mucosa Associated Lymphoid Tissue (MALT). 

the lymphatics vessels form

one-way system in which lymph flows towards the heart.

Lymph vessels (lymphatics); Lymphatic capillaries

1- remarkably permeable (take up proteins, cell debris, pathogens, and cancer cells).

Lymph vessels (lymphatics); Lymphatic capillaries structure

microscopic, blind-ended

From lymphatic capillaries,

1 ½ lymph flows through successively larger and thicker walled channels

Lymph vessels (lymphatics); Collecting lymphatic vessels:

(2) From lymphatic capillaries, lymph flows through larger and thicker walled channels.

Lymph vessels (lymphatics); Lymphatic trunks

(3) Largest collecting vessels unite to form lymphatic trunks

Lymph vessels (lymphatics); Lymphatic ducts:

(4) Lymph is eventually delivered to one of 2 large ducts in thoracic region:

Lymph vessels (lymphatics): Right lymphatic duct

(5) drains right upper arm and right side of head and thorax.

Lymph vessels (lymphatics):Thoracic duct

second (5) drains rest of body;

Thoracic duct and Right lymphatic duct

each empties lymph into venous circulation at junction of internal jugular and subclavian veins on its own side of body 

Lymph Transport:

The lymphatic system lacks an organ that acts as a pump. Lymph propelled by:

(i) Milking action of skeletal muscle.

(ii) Pressure changes in thorax during breathing move blood toward lymphatic ducts by squeezing abdominal lymph vessels as thoracic lymph vessels expand.

(iii) Valves to prevent backflow

Lymphoid cells are..

(lymphocytes, macrophages)

Lymphoid tissue

(loose reticular connective tissue) and have two types

Diffuse lymphoid tissue and Lymphoid follicles

Lymphoid tissue: Lymphoid Follicles:

are solid, spherical bodies of tightly packed lymphoid cells

Lymphoid tissue functions

(i) Houses, and provides proliferation site for, lymphocytes.

(ii) Surveillance vantage point for lymphocytes and macrophages;

Lymph nodes

Cleansing the lymph: Filter lymph. Macrophages destroy microorganisms and debris, preventing them from being delivered to blood

Spleen

Cleanses blood (macrophages remove aged red blood cells, and debris)