Chapter 20 - lymphatic system

Question 1

What is the lymphatic system and what does it consist of?

Answer 1

returns fluids leaked from blood vessels back to blood
- network of drainage vessels (lymphatic vessels)
- fluid (lymph)
- structures that cleanse lymph (lymph nodes)

Question 2

What is the function of lymphoid organs and tissues?

Answer 2

Provide structural basis of immune system
- body’s defense mechanisms
- spleen, thymus, tonsils, lymph nodes, other lymphoid tissues

Question 3

What are the functions lymphatic vessels?

Answer 3

collect the excess protein-containing interstitial fluid and return it to the blood
- transport pathogens to lymph nodes and absorbed fats from intestine to blood

Question 4

What are lymphatic capillaries, where are they not found.

Answer 4

blind-ended vessels that weave between tissue cells and blood capillaries
- bones and teeth

Question 5

How are lymphatic capillaries operate in the brain?

Answer 5

• help drain ECF (inter and cerebro fluids) and their wastes
• malfunction plays a role in degenerative diseases (Alzheimer’s)

Question 6

Why are lymphatic capillaries more permeable than blood capillaries?

Answer 6

• overlap loosely to form one-way minivalves anchored by collagen filaments, so increase ISF volume

Question 7

How does the minivalves close and why is it important?

Answer 7

• pressure in lymphatic capillaries increase, the valve closes and prevents leakage

Question 8

Which tissue is lymphatic capillaries even more permeable?

Answer 8

inflamed tissues, to help take up larger substances

Question 9

What are lacteals in the small intestine and what is the structure set up?

Answer 9

a specialized set of lymphatic capillaries for absorption and transport of digested fat
- intestinal mucosa

Question 10

How do large lymphatic vessels drain?

Answer 10

drain into larger and thinker-walled lymphatic vessels than to the subclavian veins

Question 11

What is the collecting lymphatic vessels composition, location and formation?

Answer 11

• have all three tunica (thinner), valves and anastomoses
• In skin: travel in superficial veins or deep vessels of trunk travel with deep arteries
• larger vessels unite to form lymphatic trunk

Question 12

How many lymphatic trunks are there and what are the 2 main pairings and one singluar one?

Answer 12

9
- Left: lumbar/ broncho mediastinal and Right: subclavian/ jugular trunks
- intestinal trunk

Question 13

What are the 2 main ducts the trunks deliver lymph to?

Answer 13

• right lymphatic duct
• thoracic duct (larger)

Question 14

What parts of the body does the right lymphatic duct serve and where does it drain?

Answer 14

• drains right upper limb and right side of the head and thorax
• venous circulation: right internal jugular and right subclavian

Question 15

What parts of the body does the thoracic duct serve and where does it drain?

Answer 15

• drains the rest of the body
• venous circulation: left internal jugular and left subclavian veins

Question 16

How do lymphatic vessels receive their own blood supply and what is it called when it becomes inflamed.

Answer 16

vasa vasorum
- severe inflammation is called lymphangitis (shown as a red streak on arm)

Question 17

Lymph nodes - what is it composed of and what are the immune system cells?

Answer 17

• made of immune system cells found in lymphoid tissues
• 2 types of lymphocytes (T and B cells) protect the body against antigens

Question 18

What are antigens and are the functions of the 2 types of lymphocytes?

Answer 18

A: anything that triggers an immune response
T lymphocytes: immune response; some directly attack infected cells
B lymphocytes: bind, produce plasma cells, which secrete antibodies that destroy cells with antigen

Question 19

What is the difference between macrophages and dendritic cells?

Answer 19

M - engulfs cell and active T cells - granulomas
DC - capture and deliver antigens to lymph nodes to activate T cells

Question 20

What is a lymphoid tissue?

Answer 20

component of the immune system
- provides activation and proliferation sites for lymphocytes
- ideal surveillance location for lymphocytes and macrophages

Question 21

What is the lymphoid tissue made of and what resides in it?

Answer 21

reticular connective tissue
- in all lymphoid organs except thymus
- spaces between fibers is where lymphocytes to “live” when they return from patrolling the body

Question 22

What is diffuse lymphoid tissue?

Answer 22

loose arrangement of lymphoid cells and reticular fibers
- in every body organ

Question 23

What is lymphoid follicles (lymphoid nodules)?

Answer 23

tightly packed lymphoid cells and reticular fibers
- have germinal centers of proliferating B cells
- helps form larger lymphoid organs

Question 24

Where are lymphoid follicles found?

Answer 24

• intestinal wall (of ileum) called Peyer’s patches
• the appendix
• MALT
• lymph nodes
• tonsils

Question 25

Why can lymph nodes become a secondary cancer site?

Answer 25

- cells get trapped causing a bulge that is not painful

Question 26

What is the primary lymphoid organs?

Answer 26

where T and B cells mature - B cells mature in RBM - T cells mature in the thymus

Question 27

What is the secondary lymphoid organs?

Answer 27

where mature lymphocytes first encounter their antigens and become activated, include: - lymph nodes and spleen mucosa-associated lymphoid tissue (MALT) that form: - tonsils, Peyer's patches in small intestines and appendix - diffuse lymphoid tissues

Question 28

What are the 2 regions of the lymph nodes?

Answer 28

cortex: outer layer with dense follicles and germinal centers filled with dividing B cells - deep part houses T cell in transit (circulate in blood, lymph and nodes) Medulla: consists of medullary cords, contains B cells, T cells, and plasma cells

Question 29

What is the lymph sinuses?

Answer 29

spaces in lymph nodes that separate lymph nodules and are filled with reticular fibers and macrophages

Question 30

Where does lymph enter the lymph node and what is the first structure in travels through?

Answer 30

- convex side of lymph node via afferent lymphatic vessels - large subcapsular sinus

Question 31

Where does lymph travel after the subcapsular sinus?

Answer 31

smaller sinuses of the cortex and medulla, then passes through the medullary sinuses before exiting the node at hilum via efferent lymphatic vessels

Question 32

Why is the flow of lymph slow through the lymph node?

Answer 32

fewer efferent vessels draining the node compared to the afferent vessels

Question 33

What is the largest lymphoid organs and where is it located?

Answer 33

spleen - on the left side of the abdominal cavity, under the diaphragm

Question 34

What arteries and veins serve the spleen?

Answer 34

splenic artery and vein, which enters and exits at the hilum

Question 35

What role does the spleen play in immune function?

Answer 35

provides a site for lymphocyte proliferation, immune surveillance, and immune response

Question 36

How does the spleen cleanse the blood?

Answer 36

cleanses the blood of aged and defective blood cells and platelets through macrophages

Question 37

What is the function of the spleen when it comes to storage and being a site?

Answer 37

1. stores iron and recycles breakdown products of RBC 2. stores platelets and monocytes from release into blood 3. site of fetal erythrocyte production

Question 38

What is the structure order starting from diaphragm to pancreas?

Answer 38

- diaphragm - spleen - adrenal gland - left kidney - splenic artery - pancreas

Question 39

What are the 2 components that make up the spleen?

Answer 39

White pulp and red pulp

Question 40

What is the function of white pulp?

Answer 40

where immune function occurs - mostly in lymphocytes on reticular fibers - islands of white in sea of red

Question 41

What is the function of red pulp?

Answer 41

where old blood cells and bloodborne pathogens are destroyed - lots of RBC and macrophages that engulf - made of splenic cords (reticular tissue)

Question 42

What is a potential consequence of a direct blow or severe infection to the spleen?

Answer 42

spleen ruptures, spilling blood into the peritoneal cavity

Question 43

What have surgeons discovered about the spleen after splenectomy?

Answer 43

can repair itself if left alone.

Question 44

What happens when the spleen is removed?

Answer 44

The liver and bone marrow take over most of the spleen’s functions

Question 45

Can the spleen regenerate after removal?

Answer 45

Children (>12), it will regenerate

Question 46

What is mucosa-associated lymphoid tissue (MALT), where does it and what is its function?

Answer 46

lymphoid tissues in mucous membrane - lines respiratory, genitourinary and digestive tract - protects from pathogens trying to enter the body

Question 47

Where is the largest collection of MALT?

Answer 47

- tonsils - peryer's patches - appendix

Question 48

What is the main function of tonsils?

Answer 48

lymphoid tissue at entrance of pharynx gathers and remove pathogens in food and inhaled air

Question 49

How can tonsils be identified and what is the main types?

Answer 49

seen swelling in the mucosa 1. paired palatine tonsils 2. lingual tonsil 3. pharyngeal tonsil (adenoid if enlarged) 4. pair of tubal tonsil

Question 50

Where are the paired palatine tonsils located?

Answer 50

sides posterior to oral cavity

Question 51

Which tonsils are the largest and most often infected?

Answer 51

the paired palatine tonsils

Question 52

Where is the pharyngeal tonsil (adenoid if enlarged) found?

Answer 52

posterior wall of the nasopharynx.

Question 53

What is the location and function of the pair of tubal tonsils?

Answer 53

openings of the auditory tubes into the pharynx.

Question 54

What are the components of the tonsils' lymphoid follicles?

Answer 54

- follicles with germinal centers - diffusely scattered lymphocytes.

Question 55

How are tonsils different from other lymphoid tissue?

Answer 55

- partially encapsulated - epithelium invaginates, forming deep tonsillar crypts

Question 56

What role do tonsillar crypts play?

Answer 56

trap debris and bacteria, which cross the epithelium to enter the lymphoid tissue

Question 57

How do tonsils contribute to immune response?

Answer 57

Immune cells in the tonsils are activated and build "memory" against pathogens

Question 58

What are Peyer's patches (aggregated lymphoid nodules) and what are the structurally similar to?

Answer 58

large cluster of lymphoid follicles in small intestine - tonsils

Question 59

Why is the location of the Peyer's patches ideal?

Answer 59

prevent bacteria from breaching intestinal wall - generate " memory" lymphocytes from long-term immunity

Question 60

What is the appendix and why is it placed where it is?

Answer 60

first part of large intestine containing lymphoid follicles - generate " memory" lymphocytes from long-term immunity

Question 61

Where is the thymus located and what is its function?

Answer 61

inferior neck, extending into the mediastinum and partially overlying the heart - site of T lymphocyte development

Question 62

When is the thymus most active and what happens to it after puberty?

Answer 62

- childhood - atrophies (gets smaller)

Question 63

Does the thymus continue to produce immune cells after atrophying?

Answer 63

Yes, but slowly

Question 64

What happens to the thymus in older adults?

Answer 64

replaced by fibrous and fatty tissue - difficult to distinguish from surrounding connective tissue

Question 65

What is found in the cortex of the thymus?

Answer 65

- rapidly dividing lymphocytes - scattered macrophages

Question 66

what is found in the medulla of the thymus?

Answer 66

- fewer lymphocytes - thymic corpuscles (keratinized epithelial cells)

Question 67

What role does the thymus play in immune regulation?

Answer 67

development of regulatory T cells - prevents autoimmune responses

Question 68

How does the thymus differ from secondary lymphoid organs?

Answer 68

1. no follicles (no B cells) 2. only for T lymphocyte maturation 3. has blood-thymus barrier (separates immature T lymphocytes from antigens)

Question 69

What type of cells make up the stroma of the thymus?

Answer 69

epithelial cells (not reticular fibers)