LYMPHACTIC ORGANS

Lymph Nodes

cluster along the major lymphatic vessels of the body. they are the most numerous of the lymphatic organs

Lymph Node Functions

1. Filtering lymp

• Macrophages in the nodes act to destroy and remove microbes and foreign debris that is carried by lymph

2. Activating the Immune System

• Lymphocytes in the nodes monitor the lymphatic system for foregin invaders and attack such creatures

Lymph Node Structure

• Small, bean-shaped

• Each node is surrounded by a Capsule Trabeculae (connective tissue strands)

• Cortex- outer portion of the node. this area contains follicles where dividing B cells are located

• Medulla - contains medullary cords which are inward experssions of lymphatic tissue

• Lymph synuses - fill central portion. connect lymphcytes and macrophages

Lymph Node Circulation

1. Lymph enters lymph nodes via afferent lymphatic vessels. Lymph moves into a baglike structure known as the subscapular sinus. Lymph moves thru smaller sinuses and exits at its hilus (indention) near efferent lymphatic vessles

2. Fewer efferent lymphatic vessels than afferent lymphatic vessels, lymph flow slows substantially. Lymph has to pass through several lymph nodes before it is completely cleansed

Lymphoma

metastatic caner cells, cancer of lymph node

Lymphadenitis

inflammation of a lymph node. occurs due to some type of infection

Hodgkin’s Disease

malignancy of a lymph node

Spleen

largest lymphoid structure in the body, located in the left side of the abdominal cavity beneath the diaphragm

Spleen functions

• Site of lymphocyte proliferation and immune response. has a role in cleansing the bloody by removing old and worm blood cells and platelets from the body

• Storage of red blood cell breakdown products for future use and processing

• Serving as the site of red blood cell production in the fetus (function ends after birth)

• Storing bloody platelets

Spleen Structure

• surrounded by a capsule. spleen contains trabecule that support large numbers of macrophages and lymphocytes. lymphocytes are primarly stored in a region known as the white pulp

• Red pulp- involved in removing red blood cells. splenic cords make up much of red pulp of the spleen

Splenectomy

surgical removal of a spleen. this usually occurs following trauma to the spleen. the liver often assumes the functions of the removed spleen. suregeons try to leave some of the spleen in the body because in some cases, the spleen can regenerate

Thymus Gland

located in the inferior neck and extending into the superior thorax.

Thymus glad functions

• this gland secretes the hormone thymosin and thymopoietin. these two hormones force T lymphocytes to fight specific pathogens in the immune response (proeprty known as immunocompetence)

• largest and most active during childhood. following adolescence, its growth stops and it gradully starts to atrophy

• thymus gland is primarily composed of densley packed lymphocytes, located in the cortex. thymus gland does not contain B cells

Tonsils

• they are considered to be the simplest of all the lymphoid organs. these form a ring around the phraynx and they are named according to location

2 Types of Tonsils

1. Palatine Tonsils- paired, located on either side at the postier end of the oral cavity

2. Lingual Tonsils - paired, located at the base of the tongue

3. Pharyngeal Tonsils- lo ated at the postierior wall of the naspharynx, referred to as the adenoids if they are enlarged

4. Tubal Tonsils- surrounded the openings of the eustachian tubes into the pharynx

Functions of Tonsils

• The tonsils gather and remove pathogens entering the pharynx via food or inhaled air

• Internally, tonsils contain invaginatation known as Crypts. wallas are covered by epithelial tissue. bacteria and other pathogens are often trapped and destroyed in the epithelial cells covering the crypts

Aggregates of Lymphoid Follicles

1. Peyer’s Patches- similar structure to tonsils, these are located in the small intestine

2. Vermiform Appendix- located in the large intestine, is stuctullary similar to Peyer’s Patches

3. Red Bone Marrow- open spaces of spongy bone