A&P 20: The Lymphatic System & Lymphoid Organs/Tissues

Question 1

Lymphatic system

Answer 1

system that returns fluids that have leaked from the blood vascular system back to the blood; 3 parts - lymphatic vessels, lymph, lymph nodes

Question 2

Lymphoid organs & tissues

Answer 2

provide the structural basis of the immune system

Question 3

Lymphatic vessels (lymphatics)

Answer 3

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

Question 4

Lymph

Answer 4

once interstitial fluid enters the lymphatic vessels, it is called this, which means “clear water”

Question 5

Lymphatic capillaries

Answer 5

the transport of lymph begins in these microscopic blind-ended vessels

Question 6

Lacteals

Answer 6

special set of lymphatic capillaries; transports absorbed fat from the small intestine to the bloodstream; named because of the milky white lymph that drains through them

Question 7

Chyle

Answer 7

the fatty lymph (“juice”) that drains from the fingerlike villi of the intestinal mucosa

Question 8

Collecting lymphatic vessels

Answer 8

have the same 3 tunics as veins, but these have thinner walls and more internal valves, and they anastomose more

Question 9

Lymphatic trunks

Answer 9

the largest collecting vessels unite to form these, which drain fairly large areas of the body

Question 10

Major trunks

Answer 10

named for the regions from which they drain lymph - paired lumbar, bronchomediastinal, subclavian, and jugular trunks; single intestinal trunk

Question 11

Right lymphatic duct

Answer 11

1 of 2 large ducts in the thoracic region; drains lymph from the right upper limb and the right side of the head and thorax

Question 12

Thoracic duct

Answer 12

larger of the 2 ducts in the thoracic region; receives lymph from the rest of the body

Question 13

Cisterna chyli

Answer 13

the thoracic duct arises anterior to the 1st 2 lumbar vertebrae as this enlarged sac, which collects lymph from the 2 large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs

Question 14

Lymphocytes

Answer 14

the main warriors of the immune system; arise in red bone marrow (along with other formed elements)

Question 15

T cells (T lymphocytes)

Answer 15

when activated, these cells manage the immune response; some of them directly attack and destroy infected cells

Question 16

B cells (B lymphocytes)

Answer 16

cells that protect the body by producing plasma cells

Question 17

Plasma cells

Answer 17

daughter cells that secrete antibodies into the blood or other body fluids

Question 18

Antigens

Answer 18

anything that provokes an immune response, such as bacteria and their toxins, viruses, mismatched RBC’s, or cancer cells

Question 19

Macrophages

Answer 19

play a crucial role in body protection and the immune response by phagocytizing foreign substances and by helping to activate T cells

Question 20

Dendritic cells

Answer 20

spiny-looking cells that capture antigens and bring them back to the lymph nodes

Question 21

Reticular cells

Answer 21

fibroblast-like cells that produce the reticular fiber stroma

Question 22

Stroma

Answer 22

network that supports the other cell types in lymphoid organs and tissues

Question 23

Lymphoid tissue

Answer 23

important component of the immune system, mainly because it (1) houses and provides a proliferation site for lymphocytes and (2) furnishes an ideal surveillance vantage point for lymphocytes and macrophages

Question 24

Reticular connective tissue

Answer 24

lymphoid tissue is largely composed of this loose connective tissue (dominates all lymphoid organs except the thymus)

Question 25

Diffuse lymphoid tissue

Answer 25

loose arrangement of lymphoid cells and some reticular fibers - found in virtually every body organ; larger collections appear in the lamina propria of mucous membranes such as those lining the digestive tract

Question 26

Lymphoid follicles (lymphoid nodules)

Answer 26

solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers

Question 27

Germinal centers

Answer 27

follicles often have these lighter-staining areas where proliferating B cells predominate

Question 28

Lymph nodes

Answer 28

principal lymphoid organs in the body; cluster along the lymphatic vessels of the body

Question 29

Capsule

Answer 29

each lymph node is surrounded by this dense fibrous structure from which connective tissue strands (trabeculae) extend inward to divide the node into a number of compartments

Question 30

Trabeculae

Answer 30

connective tissue strands that extend inward to divide a lymph node into a number of compartments

Question 31

Cortex

Answer 31

outer part of a lymph node

Question 32

Medulla

Answer 32

inner part of a lymph node

Question 33

Medullary cords

Answer 33

thin, inward extensions from the cortical lymphoid tissue; contain both types of lymphocytes

Question 34

Lymph sinuses

Answer 34

large lymph capillaries spread throughout a lymph node and spanned by crisscrossing reticular fibers

Question 35

Afferent lymphatic vessels

Answer 35

lymph enters the convex side of a lymph node through these

Question 36

Subcapsular sinus

Answer 36

from the afferent lymphatic vessels, lymph travels through this large, baglike sinus into a number of smaller sinuses that cut through the cortex and enter the medulla

Question 37

Medullary sinuses

Answer 37

smaller sinuses in the lymph nodes

Question 38

Hilum

Answer 38

lymph exits the node at this indented region on the concave side

Question 39

Efferent lymphatic vessels

Answer 39

lymph exits the node through these structures

Question 40

Lymphoid organs

Answer 40

aggregates of lymphoid tissue in the body; includes nodes, spleen, thymus, tonsils, Peyer’s Patches (aggregated lymphoid nodules) of the small intestine, bits of lymphoid tissue scattered in connective tissues

Question 41

Spleen

Answer 41

soft, blood-rich organ about the size of a fist; largest lymphoid organ; located in the left side of the abdominal cavity just beneath the diaphragm; curls around the anterior aspect of the stomach; site for lymphocyte proliferation and immune surveillance and response; also has blood-cleansing functions

Question 42

White pulp

Answer 42

part of the spleen where immune functions take place; composed mostly of lymphocytes suspended on reticular fibers; forms cuffs around central arteries (appears to be islands in a sea of red pulp)

Question 43

Red pulp

Answer 43

where worn-out red blood cells and bloodborne pathogens are destroyed; contains huge numbers of erythrocytes and the macrophages that engulf them; essentially = all splenic tissue that is not white pulp

Question 44

Splenic cords

Answer 44

regions of reticular connective tissue that makes up red pulp in the spleen

Question 45

Splenic sinusoids

Answer 45

blood-filled venous sinuses

Question 46

Thymus

Answer 46

bilobed organ with important functions, primarily during the early years of life; found in the inferior neck and extends into the superior thorax, where it partially overlies the heart deep to the sternum

Question 47

Thymic corpuscles

Answer 47

bizarre structures of the lighter-staining medullary areas of the thymus; consist of concentric whorls of keratinized epithelial cells - once thought to be sites of T cell destruction; recent evidence suggests they are involved in the development of regulatory T cells (class of T lymphocytes that are important for preventing autoimmune responses)

Question 48

Mucosa-associated lymphoid tissues (MALT)

Answer 48

set of distributed lymphoid tissues strategically located in mucous membranes throughout the body; helps protect us from the never-ending onslaught of pathogens that seek to enter our bodies; largest of these include the tonsils, Peyer’s Patches, and the appendix; also occurs in the mucosa of the respiratory tract and genitourinary organs as well as the rest of the digestive tract

Question 49

Tonsils

Answer 49

form a ring of lymphoid tissue around the entrance to the pharynx (throat) where they appear as swellings of the mucosa; named according to location; gather and remove many of the pathogens entering the pharynx in food or in inhaled air

Question 50

Palatine tonsils

Answer 50

paired; located on either side at the posterior end of the oral cavity; largest, most often infected

Question 51

Lingual tonsil

Answer 51

collective term for a lumpy collection of lymphoid follicles at the base of the tongue

Question 52

Pharyngeal tonsil

Answer 52

referred to as the adenoids if enlarged; in the posterior wall of the nasopharynx

Question 53

Tubal tonsils

Answer 53

tiny; surround the openings of the auditory tubes into the pharynx

Question 54

Tonsillar crypts

Answer 54

epithelium overlying the tonsils invaginates deep into their interior to form these blind-ended areas that trap bacteria and particulate matter

Question 55

Peyer’s Patches

Answer 55

AKA aggregated lymphoid nodules; large clusters of lymphoid follicles, structurally similar to tonsils; located in the wall of the distal portion of the small intestine

Question 56

Appendix

Answer 56

tubular offshoot of the 1st part of the large intestine; contains a high concentration of lymphoid follicles; in an ideal position to destroy bacteria before these pathogens can breach the intestinal wall and to generate many “memory” lymphocytes for long-term immunity

Question 57

Lymph sacs

Answer 57

by the 5th week of embryonic development, the beginnings of the lymphatic vessels and the main cluster of lymph nodes are apparent; these arise as ___ ___ that bud from developing veins