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Lymphatic system consists of three parts.

1) A network of three parts
2) Lymph
3) Lymph nodes

Functions of the Lymphatic system.

Returns interstitial fluid and leaked plasma proteins back to the blood.

Together with lymphoid organs and tissues, provide the structural basis of the ______ _______.

immune system.

One way system,lymph flows toward the heart.

Lymphatic vessels.

what are the types of lymphatic vessels.

Lymphatic capillaries
Lymphatic collecting vessels
Lymphatic trunks and ducts.

Similar to blood capillaries, except
Very permeable
Endothelial cells overlap to form one-way minivalves.

Lymphatic capillaries.

Absent from bones, teeth bone marrow and the CNS

lymphatic capillaries

Specialized lymph capillaries present in intestinal mucosa.

Lacteals

Lymphatic collecting vessels

Similar to veins, except Have thinner walls, with more internal valves.

Lymphatic trunks

Formed by the union of the largest collection ducts.

Lymph

is delivered into one of two large ducts

Right Lymphatic duct

Drains the right upper arm and the right side of the head and thorax.

Thoracic duct

arises from the cisterna chyli and drains the rest of the body.

Right Lymphatic and Thoracic duct

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

What is lymph propelled by

Pulsations of nearby arteries and Contractions of smooth muscle in the walls of the lymphatics.

Lymphocytes

The main warriors of the immune system

Two main types of Lymphocytes

T Cells And B Cells

What protects against antigens?

T cells and b cells protect against antigens.

Macrophages

Phagocytize foreign substances and help activate T-cells

Dendritic cells

Cells that capture antigens and deliver them to lymph nodes.

Reticular cells

produce stroma that supports other cells in lymphoid organs.

Lymphoid tissue

Houses and provides a proliferation site for lymphocytes.

Two main types of Lymphatic tissue.

Diffuse Lymphatic tissue and Lymphatic follicles

Diffuse lymphatic tissue

comprises scattered reticular tissue.

Lymphatic follicles

nodules are solid, spherical bodies of tightly packed reticular elements and cells.

Germinal center

composed of dendritic and B cells

Lymph nodes

Principal lymphoid organs of the body

Functions of lymph nodes

Filter lymph and Immune system

Immune system

Lymphocytes are activated and mount an attack against antigens.

What are the two Histologically distinct regions

Cortex and medulla

Structure of a lymph node

Cortex contains follicles with germinal centers, heavy with dividing B cells
Deep cortex houses T cells in transit
T cells circulate continuously among the blood,lymph nodes, and lymphatic stream.

Spleen

Largest lymphoid organs

functions of the spleen

Site of lymphocyte proliferation and immune surveillance and response.
Cleanses the blood of aged cells and platelets and debris.

Structure of the spleen two distinct areas

white and red pulp

White pulp

around central arteries Mostly lymphocytes on reticular fibers and involved in immune functions

Red Pulp

in venous sinuses and splenic cords Rich in macrophages for disposal of worn-out RBCs and bloodborne pathogens

Thymus

Increases in size and is most active during childhood. Stops growing durning adolescence and then gradually atrophies.

Differs from other lymphoid organs in important ways.

Thymus

Functions of the Thymus

It functions strictly in T lymphocyte maturation.
It does not directly fight antigens.

Thymocytes

Provide the environment in which T lymphocytes become immunocompetent

Tonsils

Simplest lymphoid organs

Crypts trap and destroy bacteria and particulate matter

Tonsils

Aggregates of lymphoid follicles

Peyer's patches and Peyer's patches and the appendix

clusters of lymphoid follicles
In the wall of the distal portion of teh small intestine.

Clusters of lymphoid follicles

Peyers patches and the appendix

Destroys bacteria preventing them from breaching the intestinal wall
Generate "memory" lymphocytes

Except for the spleen and tonsils ____________ _________ are poorly developed at birth

Lymphoid organs

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