11. Lymphatic system

Question 1

compare antibody vs antigen

Answer 1

• Antigen
  
  • surface market that body can notice as foreign
    
    • bacteria & toxins, virues, mismatched RBCs, cancer cells
• Antibody
  
  • protein released by a plsma cell that binds to antigen
    
    • immunoglobulins are type of antibodies

Question 2

what makes up the circulatory system

Answer 2

• cardiovascular and lymphatic systems

Question 3

what are the parts of the lymphatic system

Answer 3

• Vessels (lymphatics)
  
  • starts @ peripheral tissues
  • End @ venous system
• Fluid (lymph)
  
  • flows thru lymphatics
  • resembels plasma with less proteins
• Organs
  
  • connected to lymphatics
  • contain many lymphocytes

Question 4

what is the function of your lymphatic system

Answer 4

• produce, maintain and dsitribute lymphocyes and fluids
• return fluid & solutes from interstitial fluid to blood to maintain net filrations pressure
• distribute hormones, nutrients and waste products
• filters fluid to remove foreign substances and aged infected and cancerous cells
• provides structural basis of immune system

Question 5

what is the pathway of lymph

Answer 5

Bloodstream Capillaries -> Interstitual space -> lymphatic capillaries -> lymphatic vessels -> lymphatic trunks -> lymphatic ducs -> venus blood

Question 6

how are lymphatic capillaries different then blood capillaries

Answer 6

they are similar but differences are:

• > blind ended (not a loop)
• > very permeable
• > endothelial cells (simple squamous epithelium) overlap to crease one way minivalves
• anchored by collagen filaments (prevents capillary colapse)

*fluid pressure is what pushes the cels

Question 7

Where are lymphatic capillaries absent

Answer 7

bones, bone marrow, teeth and CNS

Question 8

what are lacteals

Answer 8

specialized lymph capillaries in small intestinal mucosa (lining layer in GI tract)

*Absorb digested fat & deliver chyle to bloodstream (goes into lymphatic system not venous sytstem

Question 9

desccribe lymphatic collecting vessels

Answer 9

• lined by simple squamous epithelium (endothelium)
• surrounded by thing layer of connective tissue + small amounts of smooth muscle
• contains internal valves (low pressure system fluids, prevent backflow)
• anastomose frequently (forms mesh, vessels come together)
• travels with blood vessels

Question 10

describe lymphatic trunks

Answer 10

• brains out body of lymph from different regions
• jugular trunk (right and left): drains head
• subclavian
• bronchomediastinal: drains thorax
• lumbar trunk: drains lower limbs

Question 11

drainage of right lymphatic duct vs thoracic duct

Answer 11

• right lymphatic: drians right body superior to diaphragm
• Thoracic duct: drains everything inferior to diaphragm and left body superior to diaphragm

Question 12

how is lymph transported

Answer 12

• lacks pumping organ
• vessels are low pressure conduits so moves very slow
• lymph is propelled by same mechanisms that promtoe venous return:
• > respiratory pump (breathing pressure moved blood and lymph)
• > values (unidirectional flow)
• > skeletal milking (muscle contracts, squeezes lymph)

*if blocked lymph would get accumulation of fluid

Question 13

what are the classes of lymphocytes

Answer 13

t cells: cytotocic, helper and suppressor

B cells: plasma cells

NK cells

Question 14

describe the types of T cells

Answer 14

• Cytotoxic T cells
  
  • attack foreign cells or body cells infected by the virus
  • primary cells involved in cell mediated immunity
• Helper T cells
  
  • stimulate activation and function of both T and B cells
• Supporessor T cells
  
  • inhibit activation and function of T and B cells
  • establish contron and sensitivity of immune response

Question 15

describe B cells

Answer 15

• become plasma cells -> make antibodies
• responsible for antibodiy mediated immunity

Question 16

describe NK cells

Answer 16

• 5-10% of circulating lymphocytes
• do survelliance, attack forgein cells or infected body cells

Question 17

stops of action of NK cells

Answer 17

1. if cell has an unusual Ag in plasma membrane the NK will regognize
   
   • NK cell activated and adheres to target cell
2. NK golgi apparatus moves to points to abnormal cell
   
   • produces secretory vesicles containsing perforins which travel thru cytoplasm towards NK cell surface
3. Perforins released at NK cell surface ia exocytosis
   
   • diffuse and pynch holes in membrane of cells so cant maintain and external and internal env
4. Pores cause cell to quickly disintegrate

Question 18

what are other types of lymphoid cells (not T, B or NK)

Answer 18

• mecrophages
  
  • phagocytize foreign substances and help activate T cells
• Dendritic cells
  
  • capture antigens and deliver to lymph nodes
• Reticular cells
  
  • produce stroma that supports other cells in lymphoid organs

Question 19

primary lymphoid organs vs seconary

Answer 19

Primary: where B and T cells mature

Secondary: where B & T cells encounter Ag

Question 20

how do lymphocytes develop, mature and activate

Answer 20

1. Origin
   
   • ​​B&T lymphocyte precursors originate in red bone marrow
2. Maturation
   
   • ​​precursors destined to beocme T cells -> thymus to mature
   • precurors destined to become B cells -> bone marrow
3. Seeding secondary lymphoid organs & circulation
   
   • ​​immunocompetent but naive lymphocytes leave thymus & bone marrow
   • “seed” secondary lymphoid orangs and cirulte thru blood and lymph until can recognize antigen
4. Antigen encounter and activation
   
   • lymphocytes are activated when Ag receptor binds to its specific Ag
5. Proliferation & differentiation
   
   • ​​immune response
   • activated lymphocytes proliferate (multiply) and differentiate into effector cells & memory cells
   • memory cells & efector T cells circulate continuously in blood & lymph & thoughout secondary lymphoid organs

Question 21

describe what happens to lymphocytes in the thymus

Answer 21

*Site of Lymphocytes immunocompetence & self-tolerance

1. Positive selctions
   
   • T cells must recognize self major histocomatability proteins
   • if fails to recognize self NHC results in apoptosis
   • if does recognize goes onto engative selection
2. Negative selection
   
   • T cells must not recgonize self antigen
   • if it does get apoptosis
   • failure to recognize (bind tightly) results in survival and continued maturation

*99% of T cells fail thymic eucation test and are eliminated via apoptosis

Question 23

Describe lymphoid tissue

Answer 23

• houses and provides a site for proliferation of lymphocytes
• furnishes a surveillance vantage point (check pt that everything moving throuhg belongs to self)

Types:

• diffuse lymphatic tissue:
  
  • lymphoid calls & reticular fibers found in almost every body organ
• Lymphoid folicles (lymphoid nodules)
  
  • solid spherical bodies of tightly packed lymphoid cells & reticular elements
    
    • germinal center of proliferating B cells
    • may be isolated aggregation or form part of larger lymphoid organs
    • *found in palces w/ lots of potential foregn invaders

Question 24

what are lymph nodes

Answer 24

• principal lyphoid organs of body
• clusters embedded in connective tissue along lymphatics

Functions

1. Filter lymph: macrophages destroy microorganisms & debris
2. Activate immune system: lymphocytes are activated and mount attach against antigen

Question 25

describe the structure of a lymph node

Answer 25

* Cortex * surrounded by capsule with inward extensions (trabeculae) * contains follicles with germinal centers (dendritic cells nearly encapsulate follicles) * medulla * medullary chords; inward extenstions from cortex (containing B and T cells) * Medullary sinuses: large lymph capillaries containing marcophages

Question 26

describe circulation in lymph nodes

Answer 26

- lymph (with T cells) enter via afferent lymphatic vessels - travel through cortex, large subcapsular & medullary sinuses - exist node at hilum vai efferet vessels \*have more afferent to slow movemnt so you encounter more foreign things

Question 27

describe the spleen

Answer 27

- largest lymphoid organ - on left side of body between stomach, kidney and diaphragm - has a fibrous capsule and trabeculae - contains lymphocytes, macrophages and lots of RBC

Question 28

two pats of the spleen

Answer 28

* White pulp * mostly lymphocytes and reticular fibers * allows B and T cells to interact with substances in blood and mount an immune response * Red pulp * rich in macrophages * disposal of worn out RBCs and bloodborne pathogens

Question 29

what is the function of the spleen

Answer 29

\*can live wihtout - site of lymphocyte proliferation, immune surveillance and repsonse - cleanses blood of aged blod cells/ platelets and debris - stores breakdown products of RBCs (iron) for later reuse - releases others into blood for processing by liver - stores blood paltelets and monocytes for release when needed - site of fetal RBC production

Question 30

what is the thymus

Answer 30

- located iferior neck & extends into mediastinum - biggest in childhood then atrophies - stoma of thymus has star shaped epothelial cells - thymocytes provide environemnt where T lymphocytes become **immunocompetent thru pos and neg selection** - function : T lymphocyte maturation (does not fight antigen directly)

Question 31

What is MALT, and its role

Answer 31

- mucosa associated lymphatic tissue - protects digestive and respiratory systems from foreign matter - in tonsils, peyers patches (intestines) and appendix