Human A&PHuman A&P

Chapter 20 – Lymphatic Chapter 20 – Lymphatic SystemSystem

The Lymphatic SystemThe Lymphatic System

What is the lymphatic system?What is the lymphatic system? It’s composed of:It’s composed of:

Lymphatic vessels and Lymphatic vessels and Lymphoid organsLymphoid organs

The Lymphatic SystemThe Lymphatic System

Functions:Functions:Return tissue fluid to the blood streamReturn tissue fluid to the blood stream

Why is this necessary?Why is this necessary?Example (~30L out of capillaries, 27L in)Example (~30L out of capillaries, 27L in)That extra 3L moves through the That extra 3L moves through the

lymphatic system to the blood streamlymphatic system to the blood streamFat transportation - lactealsFat transportation - lactealsImmunity – defense against Immunity – defense against

pathogens and other foreign materialpathogens and other foreign material

Lymphatic VesselsLymphatic Vessels

Lymph capillaries – very permeable Lymph capillaries – very permeable to interstitial fluidto interstitial fluid

Overlapping simple squamous epitheliumOverlapping simple squamous epitheliumOnce interstitial fluid has entered a lymph Once interstitial fluid has entered a lymph

capillary, it is called capillary, it is called lymphlymphFigure 20.1 and othersFigure 20.1 and others

Lymphatic VesselsLymphatic Vessels

Lymph vessels – have one-way Lymph vessels – have one-way valves like the veinsvalves like the veinsLymph movement is similar to venous Lymph movement is similar to venous

blood movementblood movementFigureFigure

Lymphatic VesselsLymphatic Vessels

The lymph vessels eventually converge The lymph vessels eventually converge to form:to form:the the right lymphatic ductright lymphatic duct – drains the right – drains the right

arm and the right side of the head and arm and the right side of the head and thoraxthorax

the the thoracic ductthoracic duct – drains the rest of the – drains the rest of the bodybody

These then dump lymph into the right These then dump lymph into the right and left subclavian veinsand left subclavian veins

Figure 20.2Figure 20.2

Lymphatic VesselsLymphatic Vessels

Lymphangitis – red lines on the Lymphangitis – red lines on the skinskin

As the lymph travels back to the As the lymph travels back to the blood stream it passes through blood stream it passes through many many lymph nodeslymph nodes

Figure 20.2Figure 20.2

Lymph NodesLymph Nodes

Function as filtering stations for Function as filtering stations for the lymphthe lymph

MacrophagesMacrophages are in the lymph are in the lymph nodesnodesWhat do they do?What do they do?

B-cells and T-cells are also in the B-cells and T-cells are also in the lymph nodeslymph nodesWhat do they do?What do they do?Figure 20.4Figure 20.4

Lymph Nodes (cont.)Lymph Nodes (cont.)

As B-cells and T-cells are activated As B-cells and T-cells are activated by pathogensby pathogensthe lymph node becomes swollenthe lymph node becomes swollen

Sometimes the lymph nodes can get Sometimes the lymph nodes can get overwhelmed – buboesoverwhelmed – buboes

CD animationCD animation

Other Lymphoid TissuesOther Lymphoid Tissues

Other lymphoid tissue/organs:Other lymphoid tissue/organs:SpleenSpleen - the filtering site for the blood - the filtering site for the blood

splenectomysplenectomyMALTMALT - contains macrophages, B-cells, and T- - contains macrophages, B-cells, and T-

cellscellsNo lymph filteringNo lymph filteringPeyer’s patchesPeyer’s patches, also around appendix and , also around appendix and

respiratory passagewaysrespiratory passagewaysTonsilsTonsils are accumulations of lymphoid tissue are accumulations of lymphoid tissue

Function?Function?swollen tonsils are a sign of a throat infectionswollen tonsils are a sign of a throat infection

Figure 20.5Figure 20.5