Ch 20 - Lymphatic system

Question 1

General function of the lymphatic system

Answer 1

Return Interstitial fluid and leaked proteins back to the blood
A one-way system that carries lymph towards the heart

Question 2

Structure of lymphatic capillaries

Answer 2

• Like blood capillaries except blind-ended and more permeable
• lined by leaky endothelium that takes up cell debris and pathogens
• contain overlapping edges of cells form tiny valve which open or close in response to fluid pressure

Question 3

Function of the lymphatic capillaries

Answer 3

• to collect excess interstitial fluid
• cell flaps are forced opened or closed by inside and outside interstitial pressure
  NOTE: Lacteals - specialized lymph capillaries of small intestine that absorb digested fats and deliver fatty lymph (CHYLE) to the blood

Question 4

lymphatic collecting vessels

Answer 4

• Usually parallel to blood vessels
• Have walls like veins except thinner, more valves, many anastomoses.
• vasa vasorum to supply nutrients
• join to form the lymphatic trunk

Question 5

Lymphatic trunk

Answer 5

• larger vessels, drain large areas, formed by joining of collecting vessels
• R&L Lumbar trunks (legs), and intestinal trunk (abdomen) drain into CISTERNA CHYLI
• R&L bronchomediastinals, subclavian and jugulars drian upper body and head
• they join to form right and left lymphatic ducts

Question 6

2 Lymphatic ducts

Answer 6

Right lymphatic
-collects from right upper arm, right side of head and thorax (drains into R subclavian vein)

Thoracic duct
-collects from the rest of the body (drains into junction of L subclavian vein

Question 7

lymph transport

Answer 7

• like blood but slower. 3 L of fluid returned her day
• no pump and vessels have valves to prevent back flow
• movement of lymph caused by contraction of skeletal muscles and Paul stations nearby arteries
  LYMPHEDEMA - results from blockage of flow, lymph accumulates distally in lymph vessels

Question 8

Types of lymphoid cells

Answer 8

1. Lymphocytes - formed on red bone marrow and mature into 2 types of cells (B & T-cells) to defend against antigens
2. Macrophages - phagocytize foreign antigens (help activate T-cells)
3. Dendritic cells - activate defense (early warning system) by capturing antigens and delivering them to lymph nodes
4. Reticular cells - form the internal skeleton of lymphoid organs and produce the stroma to support other cells

Question 9

describe B-Cells and T-Cells

Answer 9

B-Cells: mature in bone marrow and produce plasma cells that form antibodies
T-Cells: mature in the thymus and manage immune response. some can attack and destroy infected cells directly

Question 10

Lymphoid tissues - reticular connective tissue - 2 types

Answer 10

diffuse follicles - small scattered clusters found in most organs
lymphoid follicles (nodules) - solid spheres that contain germinal centres where B cells multiply to form plasma cells. (Eg. Peyer's patches in the small intestine)

Question 11

function of a lymph node

Answer 11

Macrophages filter and remove foreign particles and prevents spread of pathogens onto blood
Lymphocytes monitor and attack antigens, and help activate the immune system

Question 12

structure of lymph nodes (EXAM)

Answer 12

bean shaped capsule of dense C/T with trabeculae and stroma that form compartments. outer cortex contains follicles that allow B cell division. deep cortex has T-cells on patrol circulating continuously. medullary cords contain B-cell and T-cell while the lymph sinuses contain macrophages

Question 13

Spleen function

Answer 13

lymphocyte proliferation and immune surveilance.
cleans blood of old cells, breakdown products of RBC’s
stores blood platelets AND produces RBC’s in fetus

Question 14

spleen structure

Answer 14

enclosed capsule w/trabeculae and sinuses. thin and ruptures easily. contains lymphocytes, macrophages and many RBC’s. WHITE PULP - mainly lymphocytes (WBC’s) on reticular fibers. RED PULP - macrophages that dispose of old blood cells and pathogens

Question 15

Key point to the thymus

Answer 15

1. primary lymphoid organ in lower neck to heart
2. large in adolescense, shrinks with age
3. two lobules - outer cortex has dense T-cells and scattered macrophages, inner cortex (medulla) contains Hassall’s corpuscles which regulate T-cell development
4. stroma has THYMOCYTES that secrete hormones (thymosin&thymopoietin) that stimulate T-cell maturation
5. NO B-cells (so plays no role in fighting antigens)
6. considered a PRIMARY lymphoid organ as its where T-cells mature (red bone marrow = B-cells)

Question 16

key points to tonsils

Answer 16

simplest lymphoid organ, form ring of tissue around pharynx.
Function: follicles with germinal centres that produce B-cells. Have CRYPTS which trap and destroy bacteria.
Note: the more antigens exposed to early in life improve immunity later. the body build antigens

Question 17

Aggregates of lymphoid follicles

Answer 17

MALT - mucosal associated lymphoid tissue
1. protects passages that open to the outside from invaders and generates many different memory cells for future invaders (i.e. Peyer’s patches, tonsils, wall of appendix)