Lecture 15 - Lymphatic System Flashcards
Function of lymphatic system
- > helps immune system defend body against infectious agents
- > transports and houses lymphocytes and other immune cells
- > returns excess fluid to blood to maintain fluid balance-lymph, fluid transported within lymph vessel
Characteristics of lymph and lymphatic capillaries
- > 15% of fluid entering interstitial spaces not reabsorbed into blood capillaries
- > moves passively into lymphatic capillaries due to pressure gradient
- > termed lymph once inside lymph vessels
- > capillaries have no defined start or end
Components of lymph and lymphatic capillaries
- > water, dissolved solutes, and small amount of protein
- > sometimes cell debris, pathogens, or metastasized caner cells
lymphatic capillaries
- they have overlapping endothelial cells
- > one way flaps to allow fluid entrance without entrance - they are Anchoring filaments -
> they help hold endothelial cells to nearby structures
- Lacteals (lymphatic vessels of GI tract that absorb fats nutrients, etc.)
- > lymphatic capillaries within within the GI tract
- > they allow for absorption of liquid-soluble substances from GI tract
Describe how lymph is made
starts off as liquid from blood plasma
- > becomes interstitial fluid - >
becomes lymph when it enters a lymphatic capillary
how does lymph move within lymphatic capillaries
- > as additional fluid is filtered into interstitial space from blood capillary, hydrostatic pressure increases which “pushes” interstitial fluid into lymphatic capillary lumen
- > the higher the pressure, the more fluid enters a lymphatic capillary
- > the pressure of lymph within capillary forces endothelial cells (flaps) of vessel to close, trapping lymph within lymphatic vessel
- > bigger (pulsing) vessels that are adjacent to lymphatic capillaries help move lymph
What/where are lymphatic vessels
- > larger structures formed from lymphatic capillaries
- > superficial vessels positioned adjacent to superficial and veins; Deep vessels next to deep arteries and veins
- > have all three vessel tunics (intima, media, externa)
- > have valves within their lumen (required to prevent lymph from pooling in vessel and backflow in pressure systems)
Consequences of lymphatic system lacking a pump
has to rely on several mechanism to move lymph
- > contractions of nearby skeletal muscles in limbs
- > contractions of respiratory muscles
- > rhythmic contractions of smooth muscle in larger lymph vessel walls
* some connect directly to lymph nodes
Lymphatic VS. Blood Capillaries
Blood Capillaries
- > carries blood
- > high pressure
- > walls: continuous, fenestrated, sinusdoid
- > open ended
- > lack valves
- > smaller diameter Lymphatic Capillaries
Lymphatic Capillaries
- > carries lymph
- > low pressure
- > walls: overlapping flaps
- > blind-ended sacs
- > have valves
Lymphatic trunks and what do they do
- > any large lymph vessel that forms from the convergence of many lymph vessels from left and right sides of the body
Jugular trunks - > drains lymph from head and neck
Subclavian trunks - > drains lymph from upper limbs, breasts and superficial thoracic wall
Bronchomediastinal trunks- > drains deep thoracic structures
Intestinal trunks - > drain most abdominal structures
Lumbar trunks - > drain lower limbs, abdominopelvic wall and pelvic organs
Lymphatic Ducts
- > largest lymphatic vessels
- > drained into lymphatic trunks
- > two lymphatic ducts (right lymphatic duct and thoracic duct)
- > convey lymph back into venous circulation of the blood
where does the right lymphatic duct receive lymph from
- > right upper limb
- > right side of thorax
- > right side of head and neck
Where does the thoracic duct receive lymph from
- > from diaphragm to junction of slft subclavian and left jugular veins
- > drains lymph from remaining body that isn’t drained into right lymphatic duct
Cisterna chyli
saclike structure at the base of the thorasic duct
- > right/ left intestinal and lumbar trunks drain into this structure
- > contains chyle
chyle
name for lipid-rich lymph
from vessels draining GI tract
What are the primary lymphatic structures that assist the immune system
- > Red bone marrow
- > Thymus
What are the secondary structures that assist the immune system
- > lymph nodes
- > spleen: white pulp
- > tonsils
- > lymph nodules/MALT
Red bone marrow
- > responsible for hematopoiesis (produces erythrocytes, platelets, granulocytes and a granulocytes)
- > lymphocyte production; type of leukocyte (2 major types; T and B lympocytes)
- > T lymp migrates to thymus to mature
Thymus
- > bilobed organ in superior mediastinum
*trabeculae (fibrous extention) separates the two lobes into lobule
- > each loble has an outter cortex (immature T-Lymphocytes) and an inner medulla (mature T-Lymphocytes)
- > functions in T-lymphocyte maturation
involution
the process in which our thymus shrinks with age, mostly replaced by adipose tissue
functions and characteristics of Lymph Nodes
- > filter lymph and remove unwanted substances
- > typically occurs in clusters (i.e. axillary lymph receives lymph from breast, axilla and upper limb)
- > located along pathways of lymph vessels
Structure of lymph nodes
Afferent lymphatic vessels
- > bring lymph into lobe
Efferent lymphatic vessel
- > drains node, originates at the hilum
Capsule
- > sends internal extensions into in, trabeculae
- > subdivide node into compartments
Outter lymphatic node
cortex
- > has reticuar fibres
- > support germinal center (houses B-lymphocytes and some microphages)
- > has an outer region, mantel zone (contains T-Lymphocytes, macrophages, dendritic cells)
- > has corticus sinus
Inner lymphatic node
Medulla
- > medullary sinus (tiny open channels lined with macrophages)
- > connective tissue fibres, medulary cord (suppors strans of B and T lymphocytes and microphages)
Lymph flow through lymph nodes
- > enters node through afferent lymphatic vessels
- > makes its vay through lymph node sinus
- > lymph continuously monitored for presence of foreign material
- > macrophages (remove forein debris from lymph)
- > lymph exiting lymph node through efferent vessel
- > may enter nearby lymph node in cluster
What happens when lymphocyte contacts a forein substance
- >* immune response is generated
- > lymphocytes undergo cell division (especially i germinal centres)
- > some remaining in lymph node
- > others transported in lymph and blood
- > reaches area of infection
What does it mean when your lymph node is swollen
- > you’re creating so many antebodies that it stretches your lymphnode
- > sign that your body is fighting something
characteristics of spleen
- > largest lymphatic organs
- > concave anteromedial border (contains hilum, where blood vessels and nerves enter)
- > subdivide spleen into red and white pulp
- > drained by splein vein
- > supplied by splenic artery
- > surrounded by connective tissue capsule
Red vs White Pulp
White Pulp
- > clusters of T and B lymphocytess and macrophages
- > contains a central artery
Red Pulp
- > contains erythrocytes, platelets, macrophages and B-lymphocytes
- > cells housed in reticular connective tissue, forming splenic cords
- > platelets resevoir re-enters blood as needed
- > has splenic sinusoids
* permeable capillaries, so blood cells easily exit; drain to small venules leading to splenic vein
Splenic Blood flow
- > blood first enters splenic arterny, then splenic arterioles, then into the central artery (white pulp)
- > continues out through sinusoids of red pulp
- > red pulp macrophages phaocytize bacteria, foreign objects, old and defective erythrocytes and platelets
- > blood re-entres red pulp sinusoids
- > then travels through venules and out splein vein
Tonsils
- > not completely surrounded by capsule (hemicapsulated)
- > helps protect against foreign substances inhave or ingested
- > have invaginated tonsillar cryptes to increase surface area to trap material
- > contains lymphatic nodes
Different types of tonsils
Pharyngeal tonsil (1)
Palatine tonsils (2)
Lingual tonsils (several)
lymphatic nodules
- > small clusters of lymphatic cells with some extracellular matrix
- > help defend against infection
- > different from lymph node because it’s smaller and is not completely surrounded by conective tissue capsule
- > in some areas, they group together to form larger stuctures i.e. MALT
MALT
- > mucosa- associated-lymphatic-tissue
- > helps defend agains foreign substances
- > prominant in small intestins
- > located in GI (GALT), resperatory (BALT), genital, and urinary tracts
* found in lamina propria of the mucosa
