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
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
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
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)
