CH 20 Mastering

lymphatics collect larger materials Lymphatics can collect and carry large materials, even some cellular debris, that cannot penetrate the walls of veins. Inflammation further increases their permeability.

The lymphatic system returns leaked fluid and plasma proteins that escape from the bloodstream to the blood. Hydrostatic and osmotic pressures in capillary beds combine in such a way that some fluid is lost by capillaries that cannot be regained by them. These fluids return to venous circulation through the lymphatic system.

increasing pressure inside the lymph capillary Minivalves will allow fluid in when external pressure exceeds internal pressure but will prevent fluid loss when the pressures are reversed.

thoracic duct It seems like odd plumbing, but lymph from the entire body below the diaphragm (both the right and left sides) enters the venous circulation via the thoracic duct.

the right upper limb, the right side of the head, and the right thorax

cisterna chyli the cisterna chyli passes lymph from the entire body below the diaphragm into the thoracic duct for return to the heart.

the cervical, inguinal, and axillary regions The neck, inguinal area, and armpits have large clusters of lymph nodes to protect major areas of the body. They are located where collecting lymphatic vessels converge to form trunks.

thoracic duct The thoracic duct delivers lymph into the junction of the internal jugular vein and the subclavian vein.

increase permeability The lymph capillaries owe their permeability to the mini-valves formed by the lack of tight junctions between the endothelial cells and the collagen filaments anchoring the endothelial cells to surrounding structures.

It would increase lymph volume.

Thymus The thymus is responsible for the maturation of T lymphocytes, and while it is large in youth, it tends to be reduced in size as the body ages.

Tonsils The tonsils function to protect the throat and surrounding tissues from infection via the mouth and nose.

Spleen The spleen harbors macrophages that ingest and recycle materials from erythrocytes that have aged or become damaged.

MALT (D) MALT (mucosa associated lymphatic tissue) in the intestinal wall destroy bacteria before they can breach the intestinal wall. They also generate "memory" lymphocytes for long-term memory.

The spleen is a large lymphoid organ containing areas of lymphocytes on reticular fibers (white pulp) and areas of reticular connective tissue cords and blood-filled sinuses (red pulp).

Dendritic cells Dendritic cells assist in the immune response by capturing antigens and delivering them to T cells in the lymph nodes.

spleen tonsil `lymph node

thymus gland The thymus gland is the site where T lymphocyte precursors mature to become immunocompetent T lymphocytes.

Lymph is channeled toward the hilum. Trabeculae compartmentalize the node. Nodes can have several efferent and afferent vessels.

cortex

to house immune cells to transport lymph to fight infection

lymphocyte division

cortex

White pulp The white pulp of the spleen contains reticular fibers with suspended lymphocytes. These lymphocytes cleanse blood and are an important part of immunological surveillance and response.

Celiac trunk The splenic artery branches from the celiac truck.

Spleen The spleen provides a site for lymphocyte proliferation, immune surveillance, and extracting aged and defective blood cells.

removal of aged and damaged red blood cells from the blood plasma protein production

the passage from the pharynx to the middle ear The tubal tonsils surround the passages (auditory tubes) from the pharynx to the middle ear. They are used to equalize pressure behind the tympanic membrane.

Capsule Absence of a capsule allows fluids from the throat and mouth to enter crypts and get close to lymphatic tissue. The crypts allow better immune function, but they are prone to infection.

Pharyngeal tonsil The pharyngeal tonsil is located in the posterior wall of the nasopharynx and is referred to as the adenoids if it is enlarged.

Tonsils Tonsils lack a complete capsule. The epithelium overlying tonsils invaginates deeply into their interior to form crypts where bacteria and particulate matter are trapped to be destroyed in the lymphoid tissue of the tonsils.

lymph nodes

distal portion of the small intestine Peyer's patches are large clusters of lymphoid follicles and are located in the wall of the distal portion of the small intestine (the submucosa of the ileum).

red bone marrow

veins Lymph is eventually delivered to one of two large ducts in the thoracic region. Each terminal duct empties its lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein on its own side of the body.

T cell maturation

forms lymphocytes

old RBCs

dendr-

med-

lymph-

chyl-

Bursa of Fabricus (a lymphoid organ of birds, where they were first discovered)

Thymus

White pulp of spleen

deep in the cortex

Peyer's Patches Peyer's patches are located in the small intestine, and they guard against bacteria from the large intestine.

Thymus

destruction of worn-out red blood cells and bloodborne pathogens Red pulp in the spleen contains large numbers of macrophages that engulf and destroy worn-out red blood cells for recycling, or any other foreign material in the blood

along lymph vessels and clustered in the axillary, inguinal, and cervical regions

Likely near the site of infection

reticular fibers Macrophages reside on reticular fibers that span sinuses in order to trap and destroy foreign material in the lymph.