ch 20 A & P 2 ||

1. What is the main function of the lymphatic system?

Returns fluid leaked from blood vessels back to the blood.

2. What are the main parts of the lymphatic system?

Lymphatic vessels, lymph, and lymph nodes.

3. What is lymph?

Fluid found inside lymphatic vessels.

4. What is the function of lymphoid organs and tissues?

They support the immune system and help defend against disease.

Examples: lymph nodes, spleen, thymus, and tonsils.

1. How is excess interstitial fluid formed?

Capillary pressure forces fluid out, and most is reabsorbed; up to 3 L per day remains.

2. What do lymphatic vessels collect?

Excess protein-containing interstitial fluid.

3. What happens to the fluid after it enters lymphatic vessels?

It becomes lymph and is returned to the blood.

4. What else do lymphatic vessels transport?

Pathogens to lymph nodes and absorbed fats from the intestines to the blood.

1. What are lymphatic capillaries?

Blind-ended, highly permeable vessels located between tissue cells and blood capillaries.

2. Where are lymphatic capillaries absent?

bones and teeth

3. Why are lymphatic capillaries highly permeable?

Their endothelial cells overlap loosely, forming one-way minivalves.

4. How do minivalves work?

Increased interstitial fluid pressure opens them so fluid enters; increased pressure inside the capillary closes them to prevent backflow.

What keeps lymphatic capillaries from collapsing when interstitial fluid increases?

Collagen anchoring filaments pull the capillaries open, allowing more fluid to enter.

5. What is the glymphatic system?

Channels formed by brain astrocytes that connect with meningeal lymphatics to drain cerebrospinal fluid and waste.

1. Why are lymphatic capillaries more permeable than blood capillaries?

They easily absorb proteins and excess fluid from the interstitial space.

2. What can lymphatic capillaries absorb during inflammation?

Cell debris, pathogens, and even cancer cells.

3. How can cancer spread through the lymphatic system?

Cancer cells can enter lymphatic capillaries and travel through the body if lymph nodes do not capture them.

4. What are lacteals?

Specialized lymphatic capillaries in the small intestine that absorb and transport digested fats.

5. What is chyle?

Fatty, milky lymph formed when lacteals absorb digested fats; it eventually enters the bloodstream.

1. What is the pathway of lymph through lymphatic vessels?

Lymphatic capillaries → collecting vessels → lymphatic trunks → lymphatic ducts.

2. How do collecting lymphatic vessels compare with veins?

They have the same three tunics but have thinner walls, more valves, and more anastomoses.

3. Where do collecting lymphatic vessels travel?

Superficial vessels travel with superficial veins; deep vessels in the trunk travel with deep arteries.

4. What are the nine major lymphatic trunks?

Paired lumbar, bronchomediastinal, subclavian, and jugular trunks, plus one intestinal trunk.

5. What do the lymphatic trunks form?

The largest trunks unite to form the lymphatic ducts.

 Right lymphatic duct

drains right upper limb and right side of head and thorax

▪ Drains into venous circulation at junction of right

internal jugular and right subclavian veins

Larger thoracic duct

drains rest of body

▪ Empties into venous circulation at junction of left

internal jugular and left subclavian veins

▪ In about half of individuals, starts out as enlarged

sac called cisterna chyli

1. What supplies blood to larger lymphatic vessels?

The vasa vasorum, similar to larger blood vessels.

2. What is lymphangitis?

Inflammation of lymphatic vessels, usually during severe inflammation.

3. What are signs of lymphangitis?

Tender red streaks visible along the inflamed lymphatic vessels.

2. What helps move lymph forward?

One-way valves, skeletal muscle contractions, breathing pressure changes, nearby arterial pulses, and smooth muscle contractions in lymphatic walls.

 Lymphedema: 

 insufficient return of lymph to blood resulting in severe localized edema

 May be caused by tumors blocking lymphatics or

removal of lymphatics during cancer surgery

– May improve if some lymphatic pathways remain and

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1. What are lymphoid cells?

Immune cells found in lymphoid tissues along with supporting cells that form the tissue’s scaffolding.

3. What do T lymphocytes do?

They manage the immune response, and some directly destroy infected cells.

4. What do B lymphocytes do?

They become plasma cells, which secrete antibodies that mark antigens for destruction.

5. What do macrophages and dendritic cells do?

Macrophages phagocytize foreign material and activate T cells; dendritic cells carry antigens to lymph nodes to activate T cells.

 Reticular cells

fibroblast-like cells that produce

reticular fiber stroma (network that supports other cell

types) in lymphoid organs and tissues

3. What type of tissue forms most lymphoid tissue?

Loose reticular connective tissue.

EXCEPT THYMUSSSSS

5. Where are macrophages and lymphocytes located in lymphoid tissue?

Macrophages sit on reticular fibers, while lymphocytes occupy the spaces between the fibers.

1. What is the main function of lymphoid tissue?

It houses lymphocytes and provides sites where they can be activated and multiply.

1. What are the two main forms of lymphoid tissue?

Diffuse lymphoid tissue and lymphoid follicles.

2. What is diffuse lymphoid tissue?

A loose arrangement of lymphoid cells and reticular fibers found throughout the body, especially in the lamina propria of mucous membranes.

3. What are lymphoid follicles?

Solid, spherical clusters of tightly packed lymphoid cells and reticular fibers.

4. What is a germinal center?

A lighter-staining area inside a lymphoid follicle where B cells rapidly multiply.

5. Where are isolated lymphoid follicles found?

in the ilieum as peyer’s patches in appendix

2. What happens in primary lymphoid organs?

T and B lymphocytes mature there.

3. Where do B cells and T cells mature?

B cells mature in red bone marrow; T cells mature in the thymus.

4. What happens in secondary lymphoid organs?

Mature lymphocytes encounter antigens and become activated.

5. What are examples of secondary lymphoid organs?

Lymph nodes, spleen, MALT, tonsils, Peyer’s patches, appendix, and diffuse lymphoid tissue.

3. How do lymph nodes cleanse lymph?

Macrophages remove and destroy microorganisms, debris, and other harmful substances before lymph returns to the blood.

5. What role do dendritic cells play in lymph nodes?

They carry antigens from entry sites to lymph nodes and present them to T cells.

2. What is found in the cortex of a lymph node?

The superficial cortex contains lymphoid follicles with dividing B cells, while the deep cortex mainly contains T cells.

3. What is found in the medulla?

Medullary cords containing B cells, T cells, and plasma cells.

4. What are lymph sinuses?

Large lymphatic spaces throughout the node where lymph flows through reticular fibers.

5. How is lymph cleaned inside a lymph node?

Macrophages attached to reticular fibers phagocytize pathogens and foreign material.

1. How does lymph enter and leave a lymph node?

It enters through afferent lymphatic vessels on the convex side and exits through efferent lymphatic vessels at the hilum.

4. Why is slow lymph flow important?

It gives macrophages and lymphocytes time to remove pathogens and activate immune responses.

2. What path does lymph follow through a lymph node?

Afferent vessels → subcapsular sinus → cortical sinuses → medullary sinuses → efferent vessels.

 Buboes:

 infected lymph nodes (often pus-filled); bubonic

plague named for them

– Overwhelmed by bacteria they are trying to destroy

– Results in inflamed, swollen, and tender nodes—a

condition often referred to (erroneously) as swollen

“glands”—but correctly called lymphadenopathy

1. What is the spleen? main immune functions?

The largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm.

It supports lymphocyte proliferation, immune surveillance, and responses against bloodborne pathogens.

5. What role can the spleen have before birth?

It may produce red blood cells during fetal development.

White pulp

where immune function occurs

▪ Mostly lymphocytes on reticular fibers, forming “cuffs” around

central arteries; appear as islands of white in sea of red

Red pulp

where old blood cells and bloodborne pathogens are destroyed

▪ Lots of RBCs and macrophages that engulf them

▪ Composed of splenic cords (reticular tissue) that separate blood-filled splenic sinusoids (venous sinuses)

Mucosa-associated lymphoid tissue (MALT)

– Lymphoid tissues in mucous membranes throughout body

▪ Lining the respiratory, genitourinary, and digestive tracts

▪ Protects us from pathogens trying to enter body

– Largest collections include:

▪ Tonsils

▪ Peyer’s patches

▪ Appendix

2. What are the four types of tonsils?

Palatine, lingual, pharyngeal, and tubal tonsils.

3. Where are the tonsils located?

Palatine: back of oral cavity;

lingual: base of tongue;

pharyngeal: nasopharynx;

tubal: near auditory tube openings.

4. Which tonsils are largest and most often infected?

The paired palatine tonsils.

5. What are tonsillar crypts?

Deep epithelial folds that trap bacteria and debris so immune cells can respond and develop memory.