Lymphatic System Flashcards
What does the circulatory system consist of?
Cardiovascular system and the lymphatic system
What does the lymphatic system consist of?
The lymphatic vessels and the lymphoid organs
What are the functions of the lymphatic system?
return excess fluid to the intracellular space to the venous circulation and serve as the anatomical seat of the immune system
What are lymphatic vessels similar to?
Veins
What are the smallest lymphatic vessels?
Lymphatic capillaries
When lymphatic capillaries join what are they called?
Lymphatic collecting vessels
When lymphatic collecting vessels join what do they form/
Lymphatic trunks and ducts
Where do lymphatic trunk empty?
venous circulation near the heart
What are lymphatic capillaries?
blind ended vessels that form networks mirroring the structure of cardiovascular capillaries
What kind of tissue lines the walls of the lymphatic capillaries?
Simple Squamous Epithelial
What form the simple valves?
the cells at the end of the lymphatic capillaries overlap
How do the simple valves open?
the hydrostatic pressure from the interstitial space presses on the unarchored portion of teh capillary walls making the valves open
How do the simple valves connect to the surrounding connective tissue?
The collagen filaments anchor them there
Where does the excess interstitial fluid flow?
Into the capillary and flows away from the blind end
Once the fluid enters the lymphatic vessel what is it called?
Lymph
What is lymph’s composition similar to?
Plasma with much less protein
What are lacteals?
Specialized lymphatic capillaries in the intestinal mucosa absorb lipid globules
What is chyle?
lipid globules suspended in lymph form; a milky fluid
Where is chyle transported?
to the venous system
Where are lipids processed?
The Liver
Lymphatic collecting vessels have the same three tunics as veins.
True
Collecting vessels also have valves similar to those in veins?
True
How does the transport of lymph operate ?
Skeletal Muscle Pump and the Respiratory Pump
Where do lymphatic trunks drain?
Lumbar; Bronchomidiastinal; Subclavian; Jugular; Intestinal (all but intestinal trunk are paired)
Where do lymphatic trunks empty into?
Two ducts in the thoracic region
What are the two ducts in the thoracic region ?
Right lymphatic duct and the thoracic duct
Where does the right lymphatic duct drain?
it drains into the right upper arm and the right side of the head and thorax
Where does the thoracic duct drain?
the rest of the body
What is the Cisterna Chyli
an enlarged sac where the thoracic duct arises from
Where does each duct empty into?
The junction of the internal jugular and subclavian veins on its side of the body
What are lymphocytes?
leukocytes; main functional lymphoid cells
What are the lymphocytes divided into?
T-lymphocytes & B -lymphocytes
Where do lymphocytes circulate?
in lymph
Where are lymphocytes found?
in diffuse lymphoid tissues and the walls of the lymphoid organs
What is diffuse lypmhoid tissue composed of?
reticular connective tissue ; housing circulating lymphocytes
Where are diffuse lymphoid tissue found?
every organ
What are lymphoid follicles ?
spherical collections of lymphoid tissue without a fibrous capsule
How are lympoid follicles arranged?
around germinal centers containing dendritic cells and lymphocytes
What are germinal centers?
The site of proliferation of b-lymphocytes during an immune response
What are the lymphoid organs?
Lymph nodes ; spleen ; thymus ; tonsils ; Peyer’s patches ; Appendix
What are lymph nodes?
packets of lymphoid follicles surrounded by a fibrous capsule
Where are lymph nodes found?
along lymphatic vessels and clustered in the inguinal ; cervical ; and axillary regions
What do lymph nodes do?
they act to filter lymph of debris and they house macrophages and lymphocytes that act in immune respones
What do macrophages do?
they digest debris from lymph
Cortex contains ______ while medulla contains _______.
Follicles ; medullary cords
Why is flow slowed down?
Because afferent vessels outnumber efferent vessels
What are lymph sinuses ?
reticular fibers criss-cross the spaces around the follicles
Where do B-lymphocytes predominate?
in the cortex and act as sentries for the immune response
What happens when B-lymphocytes are activated?
they migrate to the medulla and proliferate, and produce plasma cells
Where do T-lymphocytes predominate?
in the medulla
When activated T-lymphocytes do what?
circulate continuously between lymphatic; cardiovascular and tissues
What is the largest lymphoid organ?
the Spleen
Where is the spleen located?
next to the greater curvature of the stomach
What is the function of the spleen?
lymphocyte proliferation and erythrocyte recycling
What is white pulp?
Lymphocytes suspended on reticular tissue
What is red pulp composed of?
venous sinuses
What perform immune surveillance?
lymphocytes and macrophpages
What does the spleen store?
blood platelets and breakdown products of erythrocytes for recycling
Where is the site for erythrocyte production in fetus
Spleen
What is a bilobed organ that secretes (thymosin and thymopoietin) that cause t lymphocytes to become immunocompetent?
Thymus
Does the size of the thymus vary with age?
yes
In infants where is the thymus located?
it is found in the inferior neck and extends into the mediastinum where it partially overlies the heart
Does it increase in size and is most active during childhood?
yes
Why does the immune system weaken as we get older?
Because it stops growing during adolescence and then gradually atrophies
How does the thymus differ from other lymphoid organs?
It functions strictly in T lymphocyte maturation ; and it does not directly fight antigens
What does the stroma of the thymus consist of?
Star shaped epithelial cells (not reticular fibers)
What do thymocytes do?
secrete the hormones that stimulate lymphocytes to become immunocompetent
What is the simplest lymphoid organs?
Tonsils
Where are the tonsils locatead?
they form a ring of lymphatic tissue around the pharynx
What are the different types of tonsils?
Palatine ; lingual ; pharyngeal ; tubal
Where are the palatine tonsils located?
either side of the posterior end of the oral cavity
Where are the lingual tonsils located?
they lie at the base of the tongue
Where are the pharyngeal tonsils located?
posterior wall of the nasopharynx
Where are the tubal tonsils located?
surround the openings of the auditory tubes into the pharynx
What do the lymphoid tissue of tonsils contain?
Follicles with germinal centers
Tonsil masses are not fully encapsulated
True
How are blind-ended crypts formed?
epithelial tissue overlying tonsil masses invaginates
What do the blind -ended crypts do?
They trap and destroy bacteria and particulate matter
Adenoids are a type of tonsil
TRUE
What are Peyer’s patches?
isolated clusters of lymphoid tissue similar to tonsils
Where are Peyer’s patches found?
in the wall of the distal portion of the small intestine (similar structures are found in the appendix
What are the functions of peyers patches and the appendix
they destroy bacteria, preventing them from breaching the intestinal wall. Generate “memory” lymphocytes for long - term immunity
Peyer’s patches and tonsils are part of a widespread patter of what?
Mucosa Associated Lymphoid Tissue (MALT)
Mucosa Associated Lymphoid Tissue (MALT) represents what?
A first line defense against invasion by bacteria and viruses
Where is MALT located?
walls of the bronchii
