Lymphatic system Flashcards
What does the lymphatic system do?
Returns interstitial fluid and leaked plasma proteins back to the blood in two ways.
What are the two ways that the lymphatic system returns the interstitial fluid back to the blood?
- Lymphatic vessels
- Lymphoid organs and tissues
What are Lymphatic vessels?
Elaborate network of drainage vessels
–>they return about 3L of leaked fluid plus plasma proteins to the blood stream
What do Lymphoid organs and tissues do?
Provide structural basis of immune system by housing phagocytic cells and lymphocytes
–> these are essential in body to provide defense/resistance to disease
What are Lymphatic Capillaries?
Blind-ended vessels that weave between tissue cells and blood capillaries
What are lymphatic capillaries called when they are found in intestinal villi?
Lacteals
Where are lymphatic capillaries not present?
Bones, teeth, and bone marrow and only limited areas (meninges) in the CNS
Are Lymphatic capillaries permeable or not permeable?
Very Permeable
Why do lymphatic capillaries have flap-like minivalves?
They provide spaces in between loosely attached endothelial cells
What happens when fluid pressure builds up in tissues?
Causes EDEMA. This is swelling or puffiness of the tissue right under the skin especially in legs or arms
what is the order of lymphatic vessels from smallest to largest?
Lymphatic capillaries–>Collecting lymphatic vessels–>Lymphatic trunks–>Lymphatic ducts
What is the difference between the structure of veins and Lymphatic vessels?
Lymphatic vessels
1. Thinner walls, with more internal valves
2. Anastomose more frequently
How are lymphatic trunks formed?
formed by union of largest collecting vessels, drain large areas of the body
What are the 5 Lymphatic trunks?
–> labelled from top to bottom
- Paired jugular trunks
- Paired subclavian
- Paired bronchomediastinal
- Paired lumbar
- Single intestinal trunk
Where does lymph go before entering the blood?
The lymph nodes
Where can you find lymph nodes?
clustered along lymphatic vessels; larger clusters where lymphatic vessels converge (inguinal, axillary, cervical regions)
What do lymph nodes do/are responsible for? (2)
- filter lymph (macrophages; remove and destroy microorganisms)
- activate the immune system
Where does the right lymphatic duct drain from?
the right upper limb, right side of the thorax and right halves of the head and neck
Where does the Thoracic duct drain from?
The thoracic duct drains the lower extremities, pelvis, abdomen, left side of the thorax, left upper extremity, and left side of the head and neck.
Lymph Transport
There’s no pump; same return aids as for veins; plus rhythmic contractions of smooth muscle in walls of lymphatic trunks and ducts
What is done for severe local edema?
blockage/removal of lymphatics during surgery
How many types of Lymphoid cells are there?
TWO TYPES
What are the two types of lymphoid cells?
- Immune system cells
- Supporting lymphoid cell
What are the types of Immune system cells? (3)
- Lymphocytes
- Macrophages
- Dendritic cells
Lymphocytes (2 types)
- T-cells – manage immune response; some attack and destroy infected cells
- B-cells – produce plasma cells
What are Plasma cells?
Develop from B lymphocytes (B cells), a type of WBC that is made in the bone marrow
Macrophages
Phagocytize foreign substances, can be antigen-presenting cells and help activate T cells
Dendritic cells
Capture antigens; deliver them to lymph nodes; help activate T cells
What is the type of cells in the supporting lymphoid cell?
Reticular cells (fibroblast-like) produce reticular fibers called stroma
What is the Stroma?
A network-like support that acts as scaffolding for immune cells
Lymphoid tissue
Includes RETICULAR CT.
- Houses and provides proliferation sites for lymphocytes
- offers SURVEILLANCE vantage points for lymphocytes and macrophages as they filter through the lymph.
What are the two main types of lymphoid tissues?
- Diffuse lymphoid tissue: loose arrangement
- Lymphoid follicles (nodules): solid, spherical bodies, tightly packed lymphoid cells
–>contain germinal centers of proliferating B cells
What are the two functional categories that the lymphoid organs are organized into?
- Primary lymphoid organs
- Secondary lymphoid organs
Primary lymphoid organs
Areas where T and B cells mature - RED BONE MARROW and THYMUS
Secondary lymphoid organs
Areas where mature lymphocytes first encounter their antigen and become activated
- Like lymph nodes composed of reticular CT
- ONLY LYMPH NODES filter lymph; other organs have only efferent lymphatics
–> Nodes, spleen, MALT (mucosa-associated lymphoid tissue) and diffuse lymphoid tissues
What are the principal secondary lymphoid organs of the body?
Lymph nodes.
–> about 2.5 cm long
–> hundreds of nodes are found throughout the body
Cortex?
Follicles with germinal centres that contain dividing B cells
Medulla?
Medullary cords (B and T cells found here) and large lymph sinuses (lymph capillaries)
What is the pathway for Lymph throughout the lymphatic vessels?
- Lymph enters the convex side of the node via afferent lymphatic vessels
- Travels through large sub capsular sinus and then into smaller sinuses found throughout the cortex and medulla
- Lymph then enters medullary sinuses
- Finally exits the concave side of the hilum via efferent lymphatic vessels
What is the effect of having more afferent than efferent vessels?
Having fewer efferents causes lymph to accumulate in lymph nodes, allowing more time for its cleansing.
It allows for lymphocytes and macrophages to fulfill their immune support functions.
Spleen - physical qualities and FUNCTION
Largest lymphoid organ! Blood-rich organ about the size of a fist. It is located on the left side of the abdominal cavity, just below the stomach
Function:
- site of lymphocyte proliferation and immune surveillance and response
- blood cleansing/recycling
- stores blood platelets and monocytes for release into the blood when needed
- may be the site of fetal RBC production
What are the two components, histologically, of the spleen?
- White pulp
–> site where immune function occurs - Red pulp
–> site where old blood cells and bloodborne pathogens are destroyed
What are the possible consequences of our thin capsule, the outer layer of our spleen?
Easily ruptured.
By producing weak contraction of the capsule, these cells help to discharge the blood stored within the spleen into the circulation.
- A ruptured spleen is a medical emergency. It can cause life-threatening internal bleeding.
Thymus
- bilobed lymphoid organ found in inferior neck
- T-lymphocytes acquire immunocompetence here
- Prominent in NEWBORNS
What does immunocompetence mean?
The immune system is working properly! The body is able to maintain and produce an appropriate immune response when necessary
Lymphocyte maturation (T-cells)
only lymphoid organ that doesn’t directly fight antigens
MALT stands for
Mucosa-Associated Lymphoid Tissue
What does MALT do? Responsible for what?
Lymphoid tissues in mucous membranes throughout the body
- Prevents from pathogens trying to enter body
- Found in: mucosa of respiratory tract, genitourinary organs and digestice tract
Where are the largest collections of MALT found? (3)
- Tonsils
- Peyer’s patches
- Appendix
Tonsils (MALT)
This is the simplest lymphoid organs; ring of lymphatic tissue around pharynx; appear as swellings of mucosa
What are the four Main parts of the TONSIL and location?
- Palatine tonsils: oral cavity
- Lingual tonsil: base on tongue
- Pharyngeal tonsil (adenoids): posterior wall of nasopharynx
- Tubal tonsils: entry of auditory tubes into pharynx
Appendix (MALT)
- offshoot of first part of large intestine
- Contains a large number of lymphoid intestine
Which part of MALT generates “memory” lymphocytes? and what are they?
Appendix
Memory lymphocytes can recognize an antigen introduced into the body during a prior infection or vaccination.
Peyer’s patches
- clusters of lymphoid follicles in wall of distal portion of small intestine
–> these are also called aggregated lymphoid nodules. - structure is similar to tonsils
What is lymphangitis? What is its cause?
This is a condition where the lymphatic vessels appear as painful red lines under the skin.
It is caused by the inflammation of larger lymphatic vessels that contain vaso vasora
Lymphedema? What are some causes of lymphedema?
This is severe localized edema. Severe swelling in one spot of the body.
The causes are–> anything that prevents normal return of lymph to the blood
What is vaso vasora?
These are defined as vessels of vessels. These are small veins or arteries within large veins or arteries.
What is buboes? What causes buboes?
It is inflamed, swollen, tender lymph nodes that result when nodes are overwhelmed by what they are trying to destroy. (swollen glands)
In the past was caused by a plague. Also caused by a strong disease.
Cancer link to the lymphatic system
Lymph nodes (little lumps of tissue) can become secondary cancer sites if metastasizing cancer cells become trapped in node
