Lymphatic System Chapter 20

Question 1

What does the lymphatic system do?

Answer 1

Returns interstitial fluid and leaked plasma protein to blood

Question 2

What are the three parts in the Lymphatic system?

Answer 2

1. Lymphatic Vessels
2. Lymph: fluid in vessels
3. Lymph nodes: cleanse lymph

Question 3

What structures are included in the Lymphoid organs and what do they do?

Answer 3

Structural basis of immune system and house the phagocytic cells and lymphocytes.
Structures: Spleen, Thymus, Tonsils, Lymph nodes.

Question 4

What is lymph?

Answer 4

Interstitial fluid that enter lymphatics (lymph vessels)

Question 5

What are the characteristics of Lymphatic Capillaries

Answer 5

1. Has blind-ended vessels between tissue cells and blood capillaries.
2. More permeable than blood capillaries, takes up larger molecules due to: Endothelial cells overlapping loosely; mini valves anchored by collagen filaments to matrix which increases ECF level opening mini valves more.
3. Lacteals: present in intestinal mucosa to absorb digested fat and deliver fatty lymph to the blood.

Question 6

What are collecting Lymphatic Vessels?

Answer 6

1. Lymph capillaries drains to them
2. Has collecting vessels, trunks, and ducts
3. Collecting valves in skin travel with superficial veins, deep vessels travel with arteries

Question 7

What are the Five Lymphatic Vessels?

Answer 7

1. Lymphatic Trunks: Union of large collecting vessels, and drain large areas of the body:
   - Paired lumbar, bronchomediastinal, subclavian, jugular trunks.
   - Single Intestinal Trunk
2. Lymphatic ducts (Delivered from trunks):
   - Right lymphatic duct drains right upper arm and right side of head and thorax.
   - Thoracic duct: drains rest of the body.

Question 8

What is Lymphangitis?

Answer 8

Lymphatic vessels appear as painful red lines under skin.

Question 9

What are the five mechanism of Lymph Transport?

Answer 9

It is like the venous (blood) system
1. Milking action of skeletal muscle
2. Pressure changes in thorax during breathing
3. Valves to prevent back flow
4. Pulsation of nearby arteries
5. Contraction of smooth muscle in walls of lymphatics.

Question 10

What are the Lymphoid Cells and what are their functions?

Answer 10

1. Immune System Cells:
   Lymphocytes; T cells (T lymphocytes) and B cells (B lymphocytes)

Function:
- T cells and B cells protect against Antigen (anything the body perceives as foreign)
- T cells manage immune response, and attack/destroy infected cells
- B cells produce plasma which secrete antibodies (mark antigens for destruction by phagocytosis)

Question 11

What function does Macrophages have? (Lymphoid cells)

Answer 11

Phagocytize foreign substances and help activate T cells

Question 12

What function does Dendritic Cells (Lymphoid Cells) have

Answer 12

Capture Antigens and deliver them to lymph nodes, and activate T cells

Question 13

What function does Reticular cells have?

Answer 13

Produces stroma (reticular fibers) in lymphoid organs, which acts as scaffolding for immune cells.

Question 14

What are the functions and structure of Lymphoid Tissues?

Answer 14

1. Provide proliferation sites for lymphocytes
2. Composed of reticular connective tissue, where macrophages live.

Question 15

What are the two types of lymphoid tissues?

Answer 15

1. Diffuse lymphoid tissues.
2. Lymphoid Follicle cells

Question 16

What are the characteristics of Diffuse Lymphoid Tissues?

Answer 16

1. Loose arrangement of lymphoid cells and reticular fibers; larger collection in laminated propria of mucous membranes.

Question 17

What are the characteristics of Lymphoid follicle cells?

Answer 17

1. Tightly packed lymphoid cells and reticular fibers which:
   - Contains germinal centers of proliferating B lymphocytes cells
   - Isolated aggregations of Peyer’s patches and in appendix

Question 18

What are the two Lymphoid Organs?

Answer 18

1. Primary lymphoid organs
2. Secondary lymphoid organs

Question 19

What are the functions/structure of the two lymphoid organs?

Answer 19

1. Primary lymphoid organs are where T cells and B cells mature; B cells mature there while T cells mature in Thymus. (Both originate from bone marrow)
2. Secondary lymphoid organs are where lymphocytes first encounter their antigen and become activated

Question 20

What are the functions of lymph nodes?

Answer 20

1. Contains macrophages that remove and destroy microorganisms that enter lymph.
2. Lymphocytes become activated and attack against antigens.W

Question 21

What is the structure of Lymph Nodes

Answer 21

1. Surrounded by external fibrous capsule
2. Capsule fibers extend inward as trabecular that divide node into compartments
3. has two regions of nodes: Cortex and Medulla.

Question 22

What is the structure of the cortex?

Answer 22

1. Contains follicles with germinal centers that contain proliferating B cells.
2. Deep cortex houses T cells in transit.
3. Abundant numbers of dendritic cells that are associated with both T and B cells

Question 23

What is the structure of the Medulla?

Answer 23

1. Contains B cells, T cells, and plasma
2. Medulla Lymph sinuses are found which:
   - contains lymphatic capillaries by crisscrossing reticular fibers.
   - Macrophages reside on fibers to check and phagocytize any foreign matter.

Question 24

What is the 5 step circulation in the Lymph Nodes?

Answer 24

1. Lymph enters convex side of node via afferent lymphatic vessels
2. Travels through large sub scapular sinus and into smaller throughout the cortex and medulla.
3. Lymph enters medullary sinuses
4. Exits concave side at HILUM via efferent lymphatic vessels.

Question 25

Why are there fewer efferent vessels?

Answer 25

To allow lymphocytes and macrophages time to function.

Question 26

What are buboes?

Answer 26

Swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy.

Question 27

What are the characteristics of the Spleen?

Answer 27

1. Largest lymphoid organ served by splenic artery and vein, which enter and exit at the hilum 2. Encased by fibrous capsule and has trabeculae.

Question 28

What are the functions of the Spleen?

Answer 28

1. Site of Lymphocyte proliferation and immune response 2. Cleanses blood of aged blood cells and platelets; macrophages remove debris 2. Stores breakdown products of RBCs such as iron for later use 3. Stores blood platelets and monocytes for release into blood 4. Site of fetal erythrocytes production

Question 29

What is the White Pulp of the spleen?

Answer 29

1. Site of immune function occurs 2. Contains lymphocytes on reticular fibers. 3. Found around central arteries

Question 30

What is the Red Pulp of the spleen

Answer 30

1. Site where old blood cells and blood borne pathogens are destroyed. 2. Rich in RBCs and macrophages that engulf them. 3. Composed of Splenic cords that separate blood-filled splenic sinusoids.

Question 31

What is Mucosa-Associated Lymphoid Tissues, and where are they found?

Answer 31

Lymphoid tissues in mucous membranes throughout body, which protects from pathogens to enter the body. Found in: 1.Respiratory tract 2. Digestive tract 3. Genitourinary organs 4. Tonsil's, Peyer's patches, Appendix

Question 32

What are the characteristics of Tonsils?

Answer 32

Includes: 1. Palatine Tonsils: Posterior end of oral cavity 2. Lingual Tonsils: Collection of follicles at base of tongue 3. Pharyngeal Tonsil: Posterior wall of nasopharynx 4. Tubal Tonsils: Surrounds auditory tubes into pharynx

Question 33

What are the functions of Tonsils?

Answer 33

1. Gather and remove pathogens in food or air 2. Contains follicles with germinal centers and scattered lymphocytes 3. Overlies epithelium invaginates, forming tonsillar crypts; bacteria are trapped and destroyed, allows immune cells to become activated and build memory cells against pathogens.

Question 34

What are the characteristics and function of Peyer's Patches?

Answer 34

1. Clusters of lymphoid follicles in wall of distal portion of small intestine Function: 1. Destroy bacteria, preventing them from breaching intestinal wall. 2. Generate memory lymphocytesW

Question 35

What are the characteristics and function of the Appendix?

Answer 35

1. Contains large number of lymphoid follicles. Function: 1. Destroy bacteria, preventing them from breaching intestinal wall. 2. General memory lymphocyte.

Question 36

What are the function of the Thymus?

Answer 36

1. Lymphoid organs where T cells mature - Active and largest during childhood - Stops growing during adolescence, then gradually atrophies - Produces immunocompetent cells

Question 37

What does the Outer Cortex of the Thymus and inner medulla do?

Answer 37

Outer Cortex: Contains rapidly dividing lymphocytes and macrophages Inner Medulla: Contains fewer lymphocytes and thymus corpuscles - Thymic Corpuscles are where regulatory T cells develop which helps to prevent autoimmunity.

Question 38

What is the EXCEPTION of Thymus from Lymphoid Organs?

Answer 38

1. Has no follicles because it lacks B cells 2. Does not fight antigens and only mature T lymphocytes: Contains blood thymus barrier to keep immature T lymphocyte isolated 3. Stroma is made up of epithelial cells not reticular fibers

Question 39

How is the Lymphatic System developed?

Answer 39

Can be seen by week 5 of embryonic development 1. Arise as lymph sacs from developing veins. 2. Jugular lymph sacs arise to form right lymphatic duct and thoracic duct 3. Lymphatic organs (except thymus) arise from mesoderm.

Question 40

Where are the Lymphoid Organs developed?

Answer 40

Lymphoid Organs: Mesodermal mesenchymal cells Thymus: Endodermal Origin, forms as an outgrowth of Pharynx