Lymphatic System Flashcards
Student Lecture Notes
What is the lymphatic system?
Network of vessels that penetrate nearly every tissue of the body and a collection of tissues and organs that produce immune cells
What are the three functions of the lymphatic system?
Fluid recovery, Immunity, Lipid absorption
How does the lymphatic system recover fluid?
Absorbs plasma proteins and excess fluids that come from the blood capillaries and puts it back into the blood stream
What happens when the lymphatic system does not recover fluid?
The circulatory system does not have enough blood and it can lead to edema
What is elephantiasis?
mosquito-borne roundworms infect lymph nodes blocking the flow of lymph, causing edema
How does the lymphatic system provide immunity?
fluids from all capillary beds are filtered through lymph nodes, which is where immune cells wait
How does the lymphatic system absorb lipids?
The small intestine has lymphatic vessels called lacteals that absorb lipids
What is the most common type of lipid absorbed by the lymphatic system?
long chain lipids that do not fit in the blood capillaries
What is lymph?
clear, colorless fluid, similar to plasma but contains less proteins
What are lymphatic capillaries?
closed at one end and tethered to surrounding tissue by protein filaments
What do lymphatic capillaries do?
allow lymph fluid, small proteins, and bacteria entrance into lymphatic capillary
Where are there not lymphatic capillaries?
bones, teeth, bone marrow, nervous system
What happens when interstitial pressure is high?
Valve like flaps on lymphatic capillaries open (they close when pressure is low)
What are the characteristics of lymphatic vessels?
low pressure, larger ones are composed of three layers
What are the three layers of lymphatic vessels?
tunica interna (endothelium valves), tunica media (elastic fibers, smooth muscle), tunica externa (thin external layer)
Route of Lymph Flow
lymphatic capillaries –> collecting vessels –> lymphatic trunks –> collecting ducts
What do collecting vessels do?
course through many lymph nodes
What do lymphatic trunks do?
drain to major portions of body
What do collecting ducts do?
right lymphatic duct and thoracic duct
Where does the route of lymph flow end?
The clavicles
Where does the right lymphatic duct drain?
drains lymph from the right arm, right side of head and thorax; empties into the right subclavian vein
Where does the thoracic duct drain?
left subclavian vein and receives lymph from the diaphragm, head, neck and thorax
What is the difference between the right lymphatic duct and the thoracic duct?
The thoracic duct is larger and longer and begins as a sac in the abdomen called cisterna chyli
Where does all lower extremity lymph get dumped?
The left subclavian
What are the mechanisms of flow for lymph transport?
skeletal muscle pump, pressure changes in thorax during breathing, artery pulsations, and rhythmic vessel smooth muscle contraction
What do artery pulsations do?
Helps increase lymphatic vessel pressure
What are lymphocytes also called?
T and B cells
What are lymphocytes?
Main WBC warriors of immune system, arise in red bone marrow, protect the body against antigens
What are T-cells?
mature in thymus (t=thymus dependent) and once activated they manage the immune response, attack/destroy infected cells
What are B cells?
cells that produce plasma cells that secrete antibodies in blood or other fluids which mark antigens for destruction
What do macrophages do?
phagocytize foreign substances and activates T-cells
What do dendritic cells do?
capture antigens bringing them back to lymph nodes
What do dendritic cells look like?
spiny
What do reticular cells do?
produce spider web-like fibers called stroma; network that supports other cell types in lymphoid organs and tissues
How many lymph nodes are in the body?
hundreds
Which lymph nodes are close to the surface?
cervical, inguinal, axillary
Which lymph nodes are deep in cavities?
thoracic, pelvic, abdominal region
What is the structure of lymph nodes?
most are bean shaped and less than an inch
What surrounds nodes?
Dense fibrous capsules from which CT strands called trabeculae extend inward dividing the node into compartments
What is lymph node flow?
receives lymph through afferent lymphatic vessels that lead into the cortex and medulla sinuses, while lymph leaves node through 1 to 3 efferent lymphatic vessels
Function of lymph nodes
only organ that filters lymph
What happens with in the filtration of the lymph nodes?
macrophages remove/eat microbes
How is the immune system activated?
lymphocytes attack foreign antigens and fight things
What is lymphadenitis?
swollen, painful node that is responding to a foreign invader (antigen)
What happens with cancer of the lymph nodes?
cancer cells can break loose, enter lymphatic capillaries, and lodge in the nodes
What do tonsils do?
Guard entrance to pharynx against ingested pathogens
What are tonsillar crypts?
the epithelium of the tonsils that has deep pits lined with lymphatic nodules
What happens when pathogens enter the tonsillar crypts?
They encounter lymphocytes
Where are the lingual tonsils located?
both sides of the tongue
Where are the tubal tonsils located?
surround the openings of the auditory tubes into the pharynx
Where is the pharyngeal tonsil located?
on the wall of pharynx just behind the nasal cavity
Where are the palatine tonsils located?
largest and most often infected of the tonsils in the posterior margin of the oral cavity
What is the function of the thymus?
houses developing T lymphocytes and secrete hormones that regulate their later activity
What do T lymphocytes do?
during development, are protected from foreign antigens by the blood-thymus barrier until they are mature and enter the blood or lymphatic vessels
What is the size of the thymus?
Large in fetuses and shrinks in adult
What is the body’s largest lymphatic organ?
Spleen (size of the fist)
What is red pulp?
consists of sinuses gorged with RBC’s
What is white pulp?
consists of lymphocytes and macrophages suspended on reticular fibers along the small branches of the splenic artery
What is MALT?
mucosa-associated lymphoid tissue
What does MALT do?
set of distributed lymphoid tissues strategically located in mucous membranes throughout the body
Where are the largest collections of MALT found?
Peyer’s patch and appendix
What is Peyer’s patch?
large clusters of lymphoid follicles, similar to tonsils, found in the wall of distal portion of the small intestine
What is the appendix?
Tubular offshoot of the first part of the large intestine that contains a high concentration of lymphoid follicles
Where are smaller collections of MALT found?
In the mucosa of the respiratory and genitourinary organs and digestive tract
