Secondary Lymphoid Organs, Lymphatic Components, and Flow Flashcards
if common lymphoid progenitor cells are defective, what is affected?
can’t make B cells, T cells, or NK cells; has a large impact on adaptive immunity
describe secondary lymphoid organs (3)
- where mature lymphocytes are maintained
- where cells of the immune system meet and immune responses are initiated
- surveillance of antigens
what are 3 secondary lymphoid organs? describe
- lymph nodes: screen lymph/peripheral tissues
- spleen: screens blood
- MALTs: monitors mucosal tissues
do lymphatics reach into every part of the body? are there any exceptions?
reach into every part of the body except teeth and brain
what are the 3 functions of the lymphatic system and say which is the most important function
- collect excess fluid from tissues and return it to the bloodstream
- transport fats that have been absorbed from the GI tract to the bloodstream
- enable immune responses!!
what is lymph fluid?
plasma-like fluid that leaks from capillaries in the cardiovascular system into tissues
what do starling’s forces describe?
hydrostatic and osmotic/oncotic pressure
what is the starling principle?
fluid movements between blood and tissues are determined by differences in hydrostatic and colloid osmotic (oncotic) pressures between plasma inside microvessels and fluid outside them
define osmotic pressure
force per unit area (pressure) required to prevent osmotic water flow
what is osmotic force?
osmotic pressure when there is no flux able to happen
what 2 molecules are in plasma? describe in terms of their ability to cross the membrane
electrolytes: can move across the membrane
2. proteins: most cannot move across the membrane (too big)
what causes hydrostatic pressure?
comes from the heart pumping blood through the system
what are the 2 starling forces from blood? describe
- blood hydrostatic pressure: pushes water out of the capillary
- blood oncotic/osmotic pressure: pulls water back into the capillary
these forces oppose each other and are referred to as hydrostatic pressure
due to hydrostatic forces, what happens if you are low in protein?
extra fluid accumulates outside the vessels because less protein to pull it back in to vessels so edema
what two starling forces come from interstitial fluid?
interstitial osmotic pressure: the molecules in interstitial fluid seeking to pull fluid from the capillaries
interstitial hydrostatic pressure: pressure pushing interstitial fluid into capillaries
what is interstitial fluid?
fluid of and between tissues; bathes cells, providing them with water, nutrition, electrolytes, lipids, amino acids, and waste removal
what happens to hydrostatic forces as blood moves from arterioles through capillaries and to venules? what happens to oncotic forces?
hydrostatic forces decrease (pumping of heart strongest at arterioles then decrease) as oncotic forces increase
what are the 3 components of lymph fluid? describe
- fluid: fluid leaked from blood vessels into interstitium; is plasma-like and contains electrolytes
- cells: immune cells like antigen presenting cells that talk to B and T cells to initiate the adaptive immune response
- molecules: small molecules like proteins and large molecules like bacteria and viruses inside and outside the cell
describe the structure of lymphatic vessels and how the structure aids their function
the ends of the vessels are open to allow interstitial fluid in, there are then valves that close to prevent backflow and direct the fluid into the collecting lymphatic vessel; when hydrostatic pressure is greater outside the vessel, fluid pushes into the vessel through the open gates; when. the hydrostatic pressure is greater inside, the gates/permeable holes shut and the fluid is passed on through the vessel
what kind of muscle lines lymphatic vessels and why?
smooth muscle; contracts to push the contents of the vessel
why do we palpate lymph nodes as part of our physical examination?
to monitor if the external response (enlarged lymph node) to an infection is in a certain or many regions of the body
describe lymphatics
an open circulatory system that collects lymph and returns it to the cardiovascular circulation
describe lymph nodes in relation to the lymphatic system
filtering stations within the lymphatic system
where does lymph fluid from caudal regions (both hind legs) gather?
from hind limbs gathers in cisterna chyli then travels through the thoracic ducts which in turn drains into the left subclavian vein and into the heart
where does lymph fluid from the left forelimb gather?
drains into the thoracic duct which in turn drains into the left subclavian and into the heart
where does lymph fluid from the right forelimb gather?
drains straight into the right subclavian vein and into the heart (the exception to all others!)
how does the composition of lymphatic fluid from the cisterna chyli differ from that that just drains through the thoracic duct or right subclavian vein ?
the lipids absorbed from the GI tract alter the composition of lymphatic fluid from the cisterna chyli as the intestines have a lot more fat
how does lymph move? (2) describe
- skeletal muscle movement: as valves close and the pressure outside of lymph vessels is increased, lymph can only move forward
- in some parts of the body (where skeletal muscle is minimal or absent) smooth muscle cells contract to move lymph, like in the abdomen
what are lymph nodes designed for?
maximal exposure of T and B cells to antigen
what does lymphatic fluid bring onto lymph nodes? (4)
- antigens
- pathogens
- debris
- toxins
what do dendritic cells bring into lymph nodes? how? (2)
bring antigen to lymph nodes through
1. lymphatics or
2. blood vessels
what does blood deliver to lymph nodes?
B and T cells
what are the 6 features of lymph nodes?
- afferent lymphatic vessels
- marginal/medullary sinuses
- paracortical region
- primary follicles
- secondary follicles (germinal centers)
- plasma cells in medullary sinus
what is the function of the afferent lymphatic vessels of lymph nodes?
bring lymph into lymph node
what is the function of macrophages/dendritic cells in lymph nodes? how do they enter lymph nodes
can find antigen while filtering in through marginal medullary sinuses
what is the function of T cells in the paracortical region of lymph nodes?
communicate with macrophages/dendritic cells in medulla and with B cells in the cortex
what is found in the primary follicles in the cortical region of lymph nodes?
B cells that are mostly naive/haven’t met antigen yet
what is found in the secondary follicles/germinal centers of lymph nodes?
these are active follicles!! B cells are responding to antigen and differentiating
what is the function of plasma cells in the medullary sinus of lymph nodes?
these plasma cells constantly release antibodies
what does the spleen do? (2)
- mounts immune responses to blood borne pathogens
- has resident macrophages to help recycle senescent red blood cells
describe the structure of the spleen (2)
- red pulp: red blood cells and macrophages; where the bulk of RBC recycling occurs
- white pulp: lymphoid tissue that surrounds arterioles; structure is similar to that in lymph nodes
describe the organization of the white pulp of the spleen
- periarterial lymphoid sheath (PALS): consist mostly of T cells and surround arterioles
- primary and secondary follicles: contain B cells in both naive and differentiating stages; near the PALS
- marginal zone: contains B cells and is an area where a particular antigen gets trapped at the interface between the red and white pulp
what are 6 mucosal-associated lymphoid tissues?
- NALTs: nasopharyngeal; in tonsils
- GALT: gut; includes peyer’s patches in small intestines and cecal tonsils of birds
- BALTs: bronchus; in lungs
- urethral MALTs
- vaginal lymphoid tissues
- SALTs: skin
describe MALTs
all mucosa contain specialized lymphoid aggregates that monitor and respond to potential pathogens with varying degrees of organization
