CH22

Question 1

what are pathogens?

Answer 1

disease-producing microbes such as bacteria and viruses

Question 2

what is immunity?

Answer 2

resistance

The state of being resistant to injury, particularly by poisons, foreign proteins, and invading pathogens through the body’s defenses

Question 3

what is susceptibility?

Answer 3

lack of immunity or resistance

Question 4

what are the two general types of immunity?

Answer 4

1) innate immunity
2) adaptive immunity

Question 5

what is innate immunity?

Answer 5

defenses that are present at birth and acts against all microbes in the same way

represents immunity’s early warning system and is designed to prevent microbes from entering the body and to help eliminate those that do gain access

Question 6

what is adaptive immunity?

Answer 6

defenses that involve specific recognition of a microbe once it has breached the innate immunity defenses

based on a specific response to a specific microbe

Question 7

what is lymph plasma?

Answer 7

clear, pale-yellow fluid confined in lymph vessels and flowing through the lymphoid system until it is returned to the blood

Question 8

what is the function of the lymphatic system?

Answer 8

assists in circulating body fluids and helps defend the body against disease-causing agents

Question 9

why do interstitial fluid and lymph plasma contain less protein than blood plasma?

Answer 9

most blood plasma protein molecules are too large to filter through the capillary wall, so most remain in cardiovascular system

Question 10

how much fluid filters from blood into tissue spaces?

Answer 10

~ 20L fluid

Question 11

how much fluid pass into lymphatic vessels and returned to blood?

Answer 11

~3L fluid

Question 12

what is lymphoid tissue?

Answer 12

specialized form of reticular connective tissue that contains large numbers of lymphocytes

Question 13

what are the primary functions of the lymphatic system?

Answer 13

1) Drains excess interstitial fluid Lymphatic vessels drain excess interstitial fluid from tissue spaces and return it to the blood

2) Transports dietary lipids Lymphatic vessels transport lipids and lipid-soluble vitamins (A, D, E, and K) absorbed by the digestive canal

3) Carries out immune responses Lymphoid tissue initiates highly specific responses directed against microbes or abnormal cells

Question 14

how are lymphatic vessels different from veins?

Answer 14

• thinner walls
• more valves

Question 15

what are lymph nodes?

Answer 15

encapsulated bean-shaped organs consisting of masses of B cells and T cells

Question 16

how are lymphatic capillaries different from blood capillaries?

Answer 16

• greater permeability: can absorb large molecules such as proteins, microbes, and lipids
• slightly larger in diameter
• one-way structure that permits interstitial fluid to flow into them but not out

Question 17

what is the one-way structure of lymphatic capillaries?

Answer 17

coming in The ends of endothelial cells that make up the wall of a lymphatic capillary overlap. When pressure is greater in the interstitial fluid than in lymph plasma, the cells separate slightly, like the opening of a one-way swinging door, and interstitial fluid enters the lymphatic capillary.

cannot come out When pressure is greater inside the lymphatic capillary, the cells adhere more closely, and lymph plasma cannot escape back into interstitial fluid.

The pressure is relieved as lymph plasma moves further down the lymphatic capillary

Question 18

what is the function of anchoring filaments?

Answer 18

They extend out from the lymphatic capillary, attaching lymphatic endothelial cells to surrounding tissues.

When excess interstitial fluid accumulates and causes tissue swelling, the anchoring filaments are pulled, making the openings between cells even larger so that more fluid can flow into the lymphatic capillary.

Question 19

what are lacteals?

Answer 19

specialized lymphatic capillaries in small intestine that carry dietary lipids into lymphatic vessels and ultimately into the blood

Question 20

what is chyle?

Answer 20

The milky‐appearing fluid found in the lacteals of the small intestine after absorption of lipids in food

The presence of these lipids causes the lymph plasma draining from the small intestine to appear creamy white

Question 21

why do proteins that do leave blood plasma cannot return to the blood by diffusion?

Answer 21

the concentration gradient (high level of blood plasma proteins inside blood capillaries, low level outside) opposes such movement

Question 22

how do lymphatic vessels return the lost blood plasma proteins to the bloodstream?

Answer 22

The lost blood plasma proteins can move readily through the more permeable lymphatic capillaries into lymph plasma

Question 23

what is the sequence of fluid flow from lost blood plasma back to t circulation?

Answer 23

blood capillaries (blood) → interstitial spaces (interstitial fluid) → lymphatic capillaries (lymph plasma) → lymphatic vessels (lymph plasma) → lymphatic trunks or ducts (lymph plasma) → junction of the internal jugular and subclavian veins (blood)

Question 24

what are the two “pumps” that aid the return of venous blood to the heart maintain the flow of lymph plasma?

Answer 24

1) Respiratory pump Lymph plasma flow is also maintained by pressure changes that occur during inhalation. Lymph flows from the abdominal region, where the pressure is higher, toward the thoracic region, where it is lower. When the pressures reverse during exhalation, the valves in lymphatic vessels prevent backflow of lymph. when a lymphatic vessel distends, the smooth muscle in its wall contracts, which helps move lymph plasma from one segment of the vessel to the next

2) Skeletal muscle pump skeletal muscle contractions compresses lymphatic vessels (as well as veins) and forces lymph plasma toward the junction of the internal jugular and subclavian veins

Question 25

what are primary lymphoid organs?

Answer 25

sites where stem cells divide and become immunocompetent

Question 26

what do multipotent stem cells in red bone marrow give rise to?

Answer 26

• mature, immunocompetent B cells
• pre-T cells

Question 27

what do pre-T cells in thymus give rise to?

Answer 27

immunocompetent T cells

Question 28

what is immunocompetence?

Answer 28

capable of mounting an immune response

Question 29

what are secondary lymphoid organs?

Answer 29

sites where most immune responses occur

• lymph nodes
• spleen
• lymphoid nodules (tissues instead of organs)

Question 30

what are lymphatic ducts?

Answer 30

ducts that empty lymph plasma into junction of jugular and subclavian veins

Question 31

what is the thymus?

Answer 31

A bilobed organ, located in the superior mediastinum posterior to the sternum and between the lungs, in which T cells develop immunocompetence

Question 32

what is the thymus’s cortex?

Answer 32

outer layer of thymus composed of large numbers of T cells and scattered nodular dendritic cells, epithelial cells, and macrophages

pre-T cells migrate from RBM to cortex, where they proliferate and mature

Question 33

what are nodular dendritic cells?

Answer 33

derived from monocytes and assists the maturation process of pre-T cells

Question 34

what is the function of the specialized epithelial cells in the thymic cortex?

Answer 34

• undergo positive selection for pre-T cells
• produce thymic hormones that are thought to aid in the maturation of T cells

Question 35

what is the thymus’s medulla?

Answer 35

inner term of thymus that consists of widely scattered, more mature T cells, epithelial cells, nodular dendritic cells, and macrophages

Question 36

what are thymic corpuscles?

Answer 36

clusters of some epithelial cells that become arranged into concentric layers of flat cells that degenerate and become filled with keratohyalin granules and keratin

may serve as sites of T cell death in the medulla

Question 37

what happens to T cells that mature and leave the thymus?

Answer 37

T cells that leave the thymus via the blood migrate to lymph nodes, the spleen, and other lymphatic tissues, where they colonize parts of these organs and tissues

Question 38

what is thymic involution?

Answer 38

functional portion of the gland is reduced considerably because adipose and areolar connective tissue begin to replace the thymic tissue

Question 39

what happens right before the thymus atrophies?

Answer 39

populates the secondary lymphoid organs and tissues with T cells.

some T cells continue to proliferate in the thymus throughout an individual’s lifetime, but this number decreases with age.

Question 40

what is the function of trabeculae in lymph nodes?

Answer 40

divide the node into compartments, provide support, and provide a route for blood vessels into the interior of a node

Question 41

what is the function of the stroma of a lymph node?

Answer 41

provides a supporting framework for lymph nodes

Question 42

what is the parenchyma of a lymph node?

Answer 42

the cortex and medulla of the lymph node

Question 43

what are lymphoid nodules?

Answer 43

egg-shaped aggregates of B cells within outer cortex

Question 44

what is the rate the thymus shrinks per year in adulthood?

Answer 44

3% per year