Ch 22 Lymphatic System

What are the components of the lymphatic system?

Lymph, Lymphatic vessels, lymphatic tissue, and lymphatic organs

What are the functions of the lymphatic system?

- Recover fluid lost from blood capillaries

- Guard against pathogens (immunity)

- Absorb lipids (fats) from small intestine

Lymph

- Clear, colorless fluid

- Similar to blood plasma, but LESS PROTEINS

- It is TISSUE FLUID taken up by lymphatic vessel

- It supplies LYMPHOCYTES to the bloodstream

- Lymph in the intestine is called CHYLE

Lymphatic Capillaries

Loosely connected OVERLAPPING endothelial cells

Elaborate of lymphatic capillaries flow and gaps

- Overlaps act as FLAPS to ensure ONE-WAY FLOW of tissue fluid into lymphatic capillary

- Large gaps allow LARGE SUBSTANCES enter the lymphatic capillary (Like proteins and whole cells)

Lymphatic Vessels

Similar to veins structure-wise; however, lymphatic vessels have thinner walls and closer valves

Flow of lymph

Lymphatic capillaries to collecting vessels to lymphatic trunks to collecting ducts to subclavian vein

Lymphatic Trunks Names

Named by location, like Jugular, subclavian, bronchomediastinal, intercostal, intestinal, and lumbar

Where are the collecting ducts draining lymph into?

Right lymphatic duct and thoracic duct

Right Lymphatic Duct

- Convergence of trunks in right thoracic cavity

- Drains R. Upper limb, R. Side of head, R. Side of thorax into R. SUBCLAVIAN VEIN

Thoracic Duct

- Begins at the cisterna chyli of abdomen

- Drains L. Upper limb, L. Side of head, L. Side of thorax, entire abdomen and both legs into the L. SUBCLAVIAN VEIN

Rhythmic Conctraction

The flow of lymph is aided by the rhythmic contraction of lymphatic vessels

How does flow of lymph resemble venous blood flow?

- Low pressure, low speed

- Valves facilitate one-way flow toward the heart

Lymphatic Tissues

- Made of collections of lymphocytes in connective tissue and mucous membranes

- MALT (muscosa-associated lymphatic tissue)

- Can be loosely or densly distributed

Where is MALT found?

Passages of respiratory, digestive, reproductive, and urinary tracts

Examples of loose and dense distributions of lymphatics

Loose as diffuse lymphatic tissue or densely packed lymphatic nodules, like aggregated lymphoid nodules/Peter patches of the small intestine

Primary Lymphatic Organs

Places where lymphocytes become mature/develop/immunocompetent

- These organs are Red Bone Marrow and Thymus

B Cells

B cells learn to recognize foreign substances/antigens in Red Bone Marrow

T Cells

T cells learn to recognize foreign substances/antigens in the Thymus

Secondary Lymphatic Organs

Lymphocytes already immunocompetent/mature

- Such as the lymph nodes and spleen

Red Bone Marrow

- The site of hematopoeisis (Blood production)

- Supplies lymphocytes and other blood cells

Reticular cells function

Reticular cells stimulate leukocyte production (White Blood Cells production)

Thymus Functions

- Primary because T cells recognize (blank)

- Houses developing lymphocytes and secretes hormones

- Shrinks after age 15

- Thymus is important for newborns for immunity development

Thymus Location and Appearance

- Bilobed (two lobes) organ between sternum and aortic arch

- Has several lobules, each with a cortex and medulla

(In these areas, T cells are developed)

Lymph Nodes Function and Concentrated Locations

- Function to cleanse lymph and act as a sit of T and B cell activation

- Concentrated in certain areas (Cervical, Axillary, thoracic, abdominal, intestinal and mesenteric, inguinal, and popliteal)

Lymph Nodes Appearance:

Numerous, bean-shaped structures less than 3 cm long

Lymph Nodes Structures:

- Has outer cortex (with germinal centers) and inner medulla

- Several afferent vessels lead to node, but usually one efferent vessels leaving at the hilum

Spleen

- The largest lymphatic organ

- Red pulp (Concentration of erythrocytes)

- White pulp (Lymphocytes and macrophages)

Red Pulp

Concentration of erythrocytes

White pulp

Lymphocytes and macrophages

Tonsils

Patches of lymphatic tissue at the entrance of the pharynx:

- Lymphatic nodules, tonsillar crypts (tonsil stones)

Tonsil Types

3 types: pharyngeal, palatine, lingual

Lymphedema

- Swelling (usually in the arms/legs) seen due to obstruction of lymphatic flow

- Examples can be in mastectomy (breast removal) patients; blockage caused by worms (filariasis); anything else that blocks flow of lymph fluid