Lymphatic System

Question 1

What is the function of the lymphatic system?

Answer 1

elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream

1) Return excess tissue fluid to the blood

2) Return leaked proteins to the blood

3) Carry pathogens to lymph nodes

4) Carry absorbed fat from the intestine to the blood (through lacteals)

Question 2

What is the structure and distribution of the lymphatic system?

Answer 2

It is a one way system, starting from the (lymphatic capillaries) which are absent in bones & teeth & are remarkably permeable, opening when the fluid pressure in the interstitial fluid is higher than the pressure in the lymphatic capillaries, then to the (collecting lymphatic vessels), then to (lymphatic trunks), then to (lymphatic ducts)

1) lymphatic vessel network

2) lymph

3) lymph nodes which cleanse the lymph as it passes through it

Question 3

What are the modifications of the lymphatic vessels which makes them highly permeable?

Answer 3

1) their endothelial cells which forms their walls are not tightly joined, but are overlapped forming mini-valves

2) collagen filaments anchors them to surrounding structures, preventing their collapse

Question 4

What is lacteals?

Answer 4

Lymphatic capillaries which are present in the small intestine which transports absorbed fats from the S.I to the Blood stream they carry a type of milky lymph called chyle

Question 5

What is the collecting lymphatic vessels?

Answer 5

Having the same three tunics as veins given thinner walls and more valves, unites to form lymphatic trunks

Question 6

What are the major lymphatic trunks?

Answer 6

1) lumbar

2) bronchomediastinal

3) subclavian

4) jugular

5) intestinal trunk

Question 7

What are the major lymphatic ducts?

Answer 7

1) right lymphatic duct (drains lymph from the right upper limb, right side of the head & thorax)

2) thoracic duct (drains rest of the body)

Question 8

What is lymphangitis?

Answer 8

When the vasa vasorum (their blood supply) becomes congested with blood and is tender to the touch

Question 9

What is lymphedema?

Answer 9

When parts of the lymphatic system is removed surgically or tumor block a lymphatic

Question 10

How is the lymph transported?

Answer 10

1) milking action of active skeletal muscles

2) pressure changes in the thorax during breathing

3) valves

4) pulsation of nearby arteries

5) smooth muscles in their walls

6) movement of adjacent tissue

Question 11

Where does the right lymphatic duct empties?

Answer 11

At the junction of the right internal jugular and subclavian veins

Question 12

Where does the thoracic duct empties its lymph?

Answer 12

Left internal jugular and subclavian veins

Question 13

What does the lymphoid cells consists of?

Answer 13

Immune system cells, supporting cells

1) T cells (manages the immune response, & directly attack and destroy infected cells)

2) B cells produces plasma cells which secretes antibodies into the blood which marks antigens for destruction

3) macrophages (phagocytize foreign substances)

4) dendritic cells (captures antigens & brings them to the lymph nodes)

5) reticular cells (produces reticular fiber “stroma” supporting cells of the lymphoid organ)

Question 14

What is a lymphoid tissue?

Answer 14

Mainly composed of reticular connective tissue

1) Houses lymphocytes and provides a site where they can be activated and proliferate

2) Furnishes an ideal surveillance vantage point for lymphocytes and macrophages

Two types:

1) diffuse lymphoid tissue

2) lymphoid follicles (nodules)

Question 15

What is the diffuse lymphoid tissue?

Answer 15

loose arrangement of lymphoid cells and some reticular fibers found in every body organ. Larger collections appear in the lamina propria (loose connective tissue) such as those lining the digestive tract

Question 16

What is the lymphoid follicles (nodules)?

Answer 16

solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers. often have lighter-staining germinal centers where proliferating (rapidly dividing) B cells predominate, which enlarge when the B cells are dividing rapidly and producing plasma cells. ln many cases, the follicles form part of larger lymphoid organs, such as lymph nodes. However, isolated aggregations of lymphoid follicles occur in the intestinal wall as Peyer’s patches (aggregated lymphoid nodules) and in the appendix

Question 17

What are the lymphoid organs?

Answer 17

1) primary lymphoid organs:

• thymus
• red bone marrow

2) secondary lymphoid organs:

• lymph nodes
• spleen

2b) MALT (mucosa associated lymphoid tissue)

• tonsils
• prayers patch (lymphoid nodules in the S.I)
• appendix

Question 18

What is the difference between the primary and secondary lymphoid organs?

Answer 18

Primary is where B & T cells mature, secondary lymphoid organs are where the mature lymphocytes encounter their first antigens and are activated

Question 19

What is the lymph node function?

Answer 19

1) cleansing the lymph

2) immune system activation

Question 20

What is the structure of the lymph nodes?

Answer 20

Bean shaped, surrounded by dense fibrous capsule where connective tissue (trabeculae) extend inwards forming the compartments. It’s internal network are formed by reticular fibers which supports the changing population of lymphocytes

They have a:

1) cortex (superficial part contains packed follicles with germinal layers heavy with diving B cells, and its deeper sites houses T cells, it is abundant with dendritic cells associated with both T and B cells)

2) medulla (consists of medullary cords, thin inward extensions from the cortical lymphoid tissue. Where Both B and T lymphocytes are found)

3) lymph sinuses (lymphatic capillaries, spanned by reticular tissue which contains numerous macrophages)

Question 21

Where is the location of the lymph nodes?

Answer 21

1) inguinal region

2) axillary region

3) cervical region

Question 22

How does the lymph nodes clean the lymph?

Answer 22

They act as lymph filters where their macrophages remove & destroy microorganisms & other debrise preventing their spread

Question 23

How does the lymph nodes activate the immune system?

Answer 23

It is where lymphocytes encounter their first antigens & are activated to mount an attack against them which where brought by the dendritic cells

Question 24

What is the circulation in the lymph nodes?

Answer 24

1) lymph enters from the afferent lymphatic vessels

2) subcapsular sinus

3) medullary sinus

4) exits from the hilum via efferent lymphatic vessels

Question 25

What is lymphadenopathy?

Answer 25

Is is when the lymph nodes becomes overwhelmed by the antigens they encounter causing the lymph node to become inflamed, swollen, & tender to the touch

Question 26

What is the structure of the spleen?

Answer 26

Size of a fist, largest lymphoid organ served by the splenic artery and vein which enters from its hilum, surrounded by a fibrous capsule and contains trabeculae which extend inwards, it consists of two parts:

1) white pulp (composed of lymphocytes suspended on reticulocytes where immune functions takes place)

2) red pulp (where worn-out RBC and blood borne pathogens are destroyed, contains huge amount of RBC and macrophages, It consists of splenic cords, regions of reticular connective tissue, that separate the blood-filled splenic sinusoids (venous sinuses))

Question 27

What is the function of the spleen?

Answer 27

Provides a site for lymphocytes proliferation, immune surveillance & response, it also cleans the blood by extracting aged and defected blood cells & platelets and its macrophages removes debris and foreign matter.
It also:

1) recycles breakdown products of RBC

2) Stores platelets, monocytes and iron

3) can be a site of erythrocytes production in the fetus

Question 28

What is meant by MALT?

Answer 28

Mucosa-associated lymphoid tissues, they are a set of distributed lymphoid tissues located in the mucous membranes through the body which protects us against never ending number of pathogens

Question 29

What are the major components of MALT?

Answer 29

1) tonsils

2) payers patches

3) appendix

4) mucosa of respiratory system

5) mucosa of genitourinary organs

6) digestive track

Question 30

What is the tonsils?

Answer 30

Ring of lymphoid which (contains follicles with obvious germinal centers surrounded by diffusely scattered lymphocytes) tissue around the entrance of the pharynx, the epithelium lining them invaginates deep into their interior, named according to their locations:

1) lingual tonsil (base of the tounge)

2) pharyngeal tonsil (posterior wall of the nasopharynx)

3) tubula tonsils (opening of the auditory tubes into the pharynx)

Question 31

What is the function of the tonsils?

Answer 31

gather and remove many of the pathogens entering the pharynx in food or in inhaled air

Question 32

What is the tonsillar crypts?

Answer 32

Invagination of the epithelium into the interior of the tonsils where bacteria are trapped and work their way to the lymphoid tissue where they are destroyed this way produces immune cells that have a memory for the trapped pathogen

Question 33

What is preyers patches?

Answer 33

Aggregated lymphoid nodules located in the wall of the small intestine

Question 34

What is the appendix?

Answer 34

tubular offshoot of the first part of the large intestine and contains a high concentration of lymphoid follicles.

1) prevent bacteria (present in large numbers in the intestine) from breaching the intestinal wall

2) to generate many “memory” lymphocytes for long-term immunity.

Question 35

What is the structure of the thymus?

Answer 35

Bilobed, found in the inferior of the neck and extends to the superior of the thorax, resembles a cauliflower which there heads are the thymus lobules containing outer cortex (densely packed with rapidly dividing lymphocytes, with few macrophages) and and Inner medulla (containing fewer lymphocytes and thymus corpuscles (concentric rings of keratinized epithelial cells “site of T cell destruction” and the corpuscles are also involved in the development of regulatory T cells to prevent autoimmune responses))

Question 36

What is the function of the thymus?

Answer 36

1) T lymphocytes precursor matures to become immunocompetent

Question 37

How is the thymus (primary lymphoid organ) different from secondary lymphoid organs?

Answer 37

1) thymus has no follicles as it lacks B cells

2) doesn’t directly fight antigens

3) their stroma consists of epithelial cells rather than reticular fibers

Question 38

What is a lymph node?

Answer 38

Small organs associated with lymphatic vessels