Chapter 20 Lymphatic System

Lymph capillaries can also take up

- Cell debris - Pathogens disease causing agent - Cancer cells - Proteins

Peyer's patches and the appendix:

- Destroy bacteria, preventing them from breaching the intestinal wall - Generate "memory" lymphocytes for long-term immunity

Lymphatic vessels (lymphatics)

- Elaborate network of drainage vessels - Circulates ~ 3L interstitial fluid per day

Lymphoid tissue main functions

- Houses and provides proliferation sites for lymphocytes - Offers surveillance vantage points for lymphocytes and macrophages as they filter through lymph

Size of the THYMUS varies with age:

- In infants, neck and extends the heart - It increases in size and most active during childhood - It stops growing during adolescence - then gradually atrophies

Names of the regions of the body that the LYMPHATIC TRUNK drain

- Lumbar pair - Bronchomediastinal pair - Subclavian pair - Jugular trunk pair -Intestinal trunk single

Lymph vessels (lymphatics) include:

- Lymphatic capillaries (thin walled close ended tubes in capillary bed) - Larger lymphatic vessels (largest are trunks and ducts)

Other Lymphoid Cells

- Macrophages - Dendritic cells - Reticular cells

Medulla

- Medullary cords extend inward from cortex and contain B cells, T cells, and plasma cells - Lymph sinuses contain macrophages

Lymph is propelled by same mechanisms:

- Milking action of skeletal muscle - Pressure changes in thorax during breathing - Valves to prevent backflow - Pulsations of nearby arteries - Contractions of smooth muscle in walls of lymphatics

Lymph is delivered from the TRUNKS into one of two LYMPHATIC DUCTS

- Right lymphatic duct - Thoracic duct

Cortex

- Superficial area of cortex contains follicles with germinal centers that are heavy with dividing B cells - Deep cortex houses T cells in transit * T cells circulate continuously among blood, lymph nodes and lymph - Dendritic cells nearly encapsulate the follicles

Lymphocytes mature into one of two main types

- T cells also called T Lmyphocytes - B cells also called B Lymphocytes

Other lymphoid organs

- Tonsil ( in pharyngeal region) - Thymus ( in thorax; most active during youth) - Spleen (curves around left side of stomach) - Peyer's patches (in intestine) - Appendix

Structure of lymph nodes

- Vary in shape and size but most are bean shaped * Small, less than 2.5 cm (~1 inch) - Surrounded by external fibrous capsule - Capsule fibers extend inward as trabeculae that divide node into compartments - Two histologically distinct regions of node: * Cortex * Medulla

Lymphatic vessels consist of 3 collecting vessels

- Vessels - Trunks - Ducts

Lymphoid cells consist of

1 immune system cells found in lymphoid tissue and 2 supporting cells that form lymphoid tissue structures

2 basic functions of lymph nodes

1. Cleansing the lymph: act as lymph "filters" (Macrophages remove and destroy microorganism and debris that enter lymph) 2. Immune system activation: offers a place for lymphocytes to become activated and mount and attack against antigens

Two main types of lymphoid tissue

1. Diffuse lymphoid tissue 2. Lymphoid follicles

Circulation in the Lymph Nodes

1. Lymph enters convex side of node via afferent lymphatic vessels 2. Travels through large subcapsular sinus and ghen into smaller sinuses found throughout cortex and medulla 3. Exits the node at the hilus via efferent vessels 4. Fewer efferent vessels, causing flow of lymph to stagnate, allowing lymphocytes and macrophages time to carry out functions 5. Lymph passes through several nodes before going back to the blood

Lymphatic system consists of two overlapping divisions

1. Lymphatics 2. Organs and tissues

Three additional functions of spleen

1. Stores breakdown products of RBCs (e.g., iron) for later reuse 2. Stores blood platelets and monocytes for release into blood when needed 3. May be site of fetal erythrocyte production (normally ceases after birth)

Two distinct areas of the spleen:

1. White pulp - contains mostly lymphocytes 2. Red pulp - concerned with disposing of worn-out RBCs and pathogens

The principal lymphoid organs

Aggregations occurs near the body surface in inguinal, axillary, and cervical

Cisterna chyli

An enlarged pouch on the thoracic duct that serves as a storage area for lymph moving toward its point of entry into the venous system

Lymphadenopathy

And disease of the lymph nodes

Lymphoma

Any neoplasm (tumor) of the lymphoid tissue, whether benign or malignant

Lymphedema caused by

Anything that prevents normal return of lymph to blood

________ can enter lymph capillaries

Bacteria, large proteins, and interstitial fluid

What was named after chief clinical feature of this disease

Bubonic plague

Lymphocytes

Cells of the adaptive immune system (main warriors)

Lymph capillaries drain into increasingly larger vessels called

Collecting lymphatic vessels

Lymphangitis is

Condition in which lymphatic vessels appear as painful red lines under the skin

• Internally, tonsils contain invaginations known as

Crypts (trap and destroy bacteria and particulate matter)

___________ have many appendages like tree branches, and collect antigens to deliver to lymph nodes for recognition by immune cells.

Dendritic cella

Lymphangiography

Diagnostic procedure in which the lymphatic vessels are injected with radiopaque dye and then visualized with X rays

Right lymphatic duct

Drains right upper arm and right side of head and thorax

Thoracic duct

Drains to the rest of the body

Lymphatic ducts

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

Splenomegaly

Enlargement of the spleen due to accumulation of infectious microorganisms, malaria, or leukemia

MALT - mucosa-associated lymphatic tissue:

Found in mucosa of respiratory tract, genitourinary organs, digestive tract; - tonsils - appendix (digestive tract) - Peyer's patches (digestive tract) - Lymphoid nodules in the walls of the bronchi (respiratory tract)

Thymus secretes

Hormones (thymosin and thymopoietin) that cause T cells to become immunocompetent - Functions strictly in T lymphocyte maturation - Does not directly fight antigens

Nodes and other organs

House phagocytes and function in defense and disease resistance (immune) - Includes: Tonsils, Lymph nodes, Thymus, Bone marrow, and Spleen

Your patient has had her spleen removed after it was ruptured in a motorcycle accident. Which of the following is your greatest concern for her future health status?

Infection

Buboes

Inflames, swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy

Lyphangitis caused by

Inflammation of larger lymphatic vessels that contain vaso vasora

Tonsillitis

Inflammation of the tonsils, typically due to bacterial infection. Tonsils become red, swollen, and sore.

Fluids that was force out of the capillaries by HP (can be 3 liters/day!)

Interstitial fluid

Hodgkin's lymphoma

Is a type of lymphoma in which cancer originates from a specific type of white blood cells called lymphocytes. Symptoms may include fever, night sweats, and weight loss. Often there will be non-painful enlarged lymph nodes in the neck, under the arm, or in the groin

Non-Hodgkin's Lymphoma

Is cancer that originates in your lymphatic system, the disease-fighting network spread throughout your body a tumor develop from lymphocytes

Hypoalbuminemia is a medical condition in which blood plasma levels of albumin are abnormally low. One cause of this disorder is the increased movement of plasma albumin into the interstitial space through leaky blood capillaries. How would this condition affect the volume of lymph that is produced?

It would increase lymph volume.

Spleen

Largest lymphoid organ - Location: LEFT SIDE beneath diaphragm

Pharyngeal tonsils

Located at the posterior wall of the nasopharynx. These are referred to as the adenoids if they are enlarged

Diffuse lymphoid tissue

Loose arrangement of lymphoid cells and some recticular fibers found in virtually every body organ

Once it is picked up by lymph vessels

Lymph

Which statement correctly describes the origin of lymph fluid?

Lymph is excess tissue fluid formed from plasma that has leaked from capillaries

Small organs intimately associated with lymphatic vessels

Lymph nodes

Blind-ended vessels that weave between tissue cells and blood capillaries

Lymphatic capillaries

Offers a one-way system, ensuring lymph flows only toward heart

Lymphatic vessels

Select the correct statement about lymphoid tissue.

Lymphoid tissue is predominantly reticular connective tissue.

T cells mainly

Manage immune response and some also attack and destroy infected cells

Lingual tonsils

Paired, located at the base of the tongue

Palatine tonsils

Paired, located on either side at the posterior end of the oral cavity (largest and most commonly infected tonsils).

Found in the wall of the distal portion of the small intestine

Peyer's patches

Isolated clusters of lymph follicles found in the wall of the small intestine.

Peyer's patches

Macrophages

Phagocytize foreign substances and help activate T cells

Lymph nodes is

Principal secondary lymphoid organs of the body there are 100 of nodes throughout the body

B cells mainly

Produce plasma cells which secrete antibodies - Antibodies mark antigens fro destruction by phagocytosis

Recticular cells

Produce reticular fiber called stroma in lymphoid organs

T cells and B cells

Protect against antigens (anything the body perceives as foreign) - Examples: Bacteria, Virus, Toxins, Fungi, Cancer, Mismatch RBCs, Cancer cells, and Protozoa

MALT

Protects the digestive and respiratory systems from foreign matter

Lymph

Protein-containing fluid within lymphatic vessels.

Lymphoid organs and tissues

Provide structural basis of immune system by housing phagocytic cells and lymphocytes

Lymphoid tissue are largely composed of

Recticular connective tissues ( chicken wire of the lymphatic system) a type of loose connective tissue

Lymphatic System

Returns fluids leaked from blood vessels back to blood

Lymphedema

Severe localized edema

Lymphatic capillaries

Similar to blood capillaries except EXTREMELY PERMEABLE and endothelial cells overlap (like shingles) to form minivalves

Dendritic cells

Spiny-looking cells that capture antigens and deliver them to lymph nodes; also help activate T cells

Stores blood platelets

Spleen

Splenectomy

Surgical removal or ruptured spleen

Tubal tonsils

Surround the openings of the auditory tubes into the pharynx

Structure of the Spleen

Surrounded by a fibrous capsule, it has trabeculae that extend inward and contains lymphocytes, macrophages, and huge numbers of erythrocytes RBCs

Condition of Boboes

Swollen glands and are sometimes pus-filled

The thymus is important for

T lymphocyte maturation

Sentinel node

The first node that receives lymph drainage from a body area suspected of being cancerous

What is the main function of the lymphatic system?

The lymphatic system returns leaked fluid and plasma proteins that escape from the bloodstream to the blood.

Which of the statements best explains the presence of red streaks on Andrew's forearm?

The lymphatic vessels of his forearm are inflamed.

A patient's deep hand laceration was sutured at your clinic yesterday. When you make a follow-up call today, the patient reports "some red streaks on my forearm." Why are you concerned?

The red streaks suggest lymphangitis, which occurs when the blood vessels that supply inflamed lymphatic vessels (vasa vasorum) become congested with blood. You are concerned that the patient's wound is infected by bacteria.

Which lymphoid organ extracts aged and defective blood cells and platelets from the blood in addition to storing some of the breakdown products for later reuse?

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

Which of these lymphoid organs is part of a collection of tissues called the mucosa-associated lymphoid tissues (MALT) and removes pathogens entering the pharynx (throat)?

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

Lymphatic trunks are formed by

The union of the largest collecting vessels and drain to the large areas of the body

Which of the following is a role of lymph nodes?

They filter lymph.

The day after Andrew's surgery, the lymph nodes in his right armpit become enlarged and tender. This was most likely caused by which of the following?

This is due to infection of his lymph nodes by bacteria.

The thymus is the only lymphoid organ that does not DIRECTLY fight antigens.

True

When tissues are inflamed, lymphatic capillaries permit uptake of large particles such as cell debris, pathogens, and cancer cells.

True

Elephantiasis

Typically a disease in which the lymphatics become clogged with parasitic roundworms, an infectious condition called filariasis

Types of Tonsils:

a. Palatine b. Lingual c. Pharyngeal d. Tubal

Lymphangitis is caused by ______.

an infection

Which of the following represents a logical sequence of structure that contribute to return of fluid to the blood via the lymph

arteries; blood capillaries; lymphatic vessels; subclavian vein

Which of the following would the body perceive as an antigen

bacteria, virus, and mismatched red blood cell

Red pulp of the spleen is most concerned with ___________ while white pulp is most concerned with ________

blood filtering..... immunity

Lymphatic capillaries are NOT found in __________.

bone marrow

The prefix _____ means juice.

chyl-

Liquefied fat, called _________, is carried by lacteals from the small intestine to the blood stream.

chyle

Lymphatic vessels

collect leaked fluids from interstitial spaces

The prefix _____ means resembling a tree

dendr-

Which of the following lymphoid cells trap antigens and transport them to lymph nodes?

dendritic cells

Where are Peyer's patches located?

distal portion of the small intestine

Lymph vessels do NOT transport ________.

erythrocytes

Lymph tends to stall inside lymph nodes this is due to

fewer efferent lymphatic vessels than afferent lymphatic vessels

The highest density of lymph node can be found

guarding the trunk of the body

Peyer's patches

isolated clusters of lymphoid tissue, similar to tonsils - Similar structures are also found in the appendix

Fats absorbed from the small intestine are transported to the bloodstream via ________.

lacteals

The prefix _____ means lymph, lymphatic

lymph-

Vessels that collect excess tissue fluid and return it to the blood stream are called ___________.

lymphatics

Within buboes, bacteria are directly attacked by ______.

macrophages

The prefix ______ means middle

med-

Both types of lymphocytes are found in the __________, which are inward extensions of cortical lymphoid tissue in lymph nodes.

medullary cord

Which of the following contributes to flow of lymph through vessels

milking action of skeletal muscle and pressure changes in the thorax

Lymphatic capillaries owe their permeability to the presence of

minivalves in their walls

Which lymphoid cells produce antibodies?

plasma cells

Which of these is not a function of the lymph node

produce red blood cells in special cases

Lacteals

specialized lymph capillaries present in intestinal mucosa and absorb digested fat and deliver fatty lymph (chyle) to the blood

Largest lymphatic organ.

spleen

Which of the following lymphoid tissues removes defective red blood cells from the blood

spleen

What anatomical area(s) is/are protected by the tubal tonsils?

the passage from the pharynx to the middle ear

Receives lymph from most of the body

thoracic duct

Which lymphoid organ atrophies as we age?

thymus

Which lymphoid organ(s) serve(s) as the site where T lymphocytes become immunocompetent T cells?

thymus gland

Tonsils promote memory of pathogens by

trapping pathogens to develop immune cells with memory.

Thymus

• A bilobed lymphoid organ

Lymphatics system consists of 3 parts

• Network of Lymphatic vessels (lymphatics) pipes • Lymph (fluid in vessels) • Lymph nodes (organs associated with vessels and cleanse lymph)

Main function of SPLEEN

• Site of lymphocyte proliferation and immune surveillance and response • Cleanses the blood of aged cells and platelets, and debris; macrophages remove debris

Organs and Tissues consists of

• Spleen • Tonsils • Thymus • Organs throughout body

Tonsils

• The tonsils gather and remove pathogens entering the pharynx via food or inhaled air. - Simplest lymphiod organ