Lymphatic System Flashcards
Explain the structure of the Lymphatic System
Lymphatic System
Consists of two semi-independent parts:
- A network of lymphatic vessels
- Lymphoid tissues and organs scattered throughout the body
Explain the main functionalities of the Lymphatic System
Lymphatic System
- Returns interstitial fluid and leaked plasma proteins back to the blood
- Lymph – interstitial fluid once it has entered lymphatic vessels
- One-way system, lymph flows toward the heart
Which are the Lymph vessels?
Lymph vessels
- capillaries
- collecting vessels
- trunks and ducts
Describe Lymphatic Capillaries.
Lymphatic Capillaries
- Similar to blood capillaries, with modifications:
- Very permeable
- Loosely joined endothelial minivalves
- Withstand interstitial pressure and remain open
- The minivalves function as one-way gates that:
- Allow interstitial fluid to enter lymph capillaries
- Do not allow lymph to escape from the capillaries
During inflammation, lymph capillaries can absorb:
Lymphatic Capillaries
During inflammation, lymph capillaries can absorb:
- Cell debris
- Pathogens
- Cancer cells
What is Cell debris?
Debris - A useless accumulation of miscellaneous particles; waste in the form of fragments.
What is the task of cells in lymph node?
Cells in the lymph nodes cleanse and “examine” this debris
What is the task of Lacteals?
Lacteals – specialized lymph capillaries present in intestinal mucosa
- Absorb digested fat and deliver chyle to the blood
The intestinal mucosa, also called the gastric mucosa, is the lining of the gastrointestinal tract. It surrounds the lumen, the hollow space at the center of the tract, through which food passes. The mucosa secretes a layer of mucus that protects the cells and helps food move along the gastrointestinal tract.
Explain how Lymph is transported.
Lymph Transport
- The lymphatic system lacks a pumping organ
- Vessels are low-pressure conduits
- Uses the same methods as veins to propel lymph:
- Pulsations of nearby arteries
- Contractions of smooth muscle in the walls of the lymphatics
Example of Lymphocytes
Lymphocytes
- T cells
- B cells
- Natural Killer cells
Explain the function of T-cells.
T cells - Lymphocytes
- Manage the immune response
- Attack and destroy foreign cells
Explain the function of B-cells
B cells - Lymphocytes
- Produce plasma cells, which secrete antibodies
- Antibodies immobilize antigens
What is the definition of an antigen and who are protecting against these?
Definition of “antigen”
- T cells and B cells protect the body against antigens
- Antigen – anything the body perceives as foreign;
- Bacteria and their toxins; viruses
- Mismatched RBCs or cancer cells
Describe Macrophages.
Macrophages – Other Lymphoid Cells
Phagocytize foreign substances and help activate T cells
Explain Dendritic cells
Dendritic cells - Other Lymphoid Cells
Spiny-looking cells with functions similar to macrophages
Describe Lymph Nodes
Lymph Nodes
- Principal lymphoid organs of the body
- Embedded in connective tissue and clustered along lymphatic vessels
- Aggregations of these nodes occur near the body surface in inguinal, axillary, and cervical regions of the body
Which are the two basic functions of Lymph Nodes?
Lymph Nodes
Two basic functions:
- Filtration – macrophages destroy microorganisms and debris
- Immune system activation – monitor for antigens and mount an attack against them
View Structure of Lymph Node
Structure of Lymph Node
Which are the Lymphoid Organs?
Lymphoid Organs
Which is the largest lymphoid organ?
Spleen
- Largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm
- It is served by the splenic artery and vein, which enter and exit at the hilus
Which are the functions of the spleen?
Functions Spleen
- Site of lymphocyte proliferation
- Immune surveillance and response
- Cleanses the blood
Addition Spleen Functions:
- Stores breakdown products of RBCs for later reuse
- Spleen macrophages salvage and store iron for later use by bone marrow
- Site of fetal erythrocyte production (normally ceases after birth)
- Stores blood platelets
Describe Thymus.
Thymus
A bilobed organ that secretes hormones (thymosin and thymopoietin) that cause T lymphocytes to become immunocompetent
Explain how the size of Thymus varies with age
Size of the thymus varies with age:
- In infants, it is found in the inferior neck and extends into the mediastinum where it partially overlies the heart
- It increases in size and is most active during childhood
- It stops growing during adolescence and then gradually atrophies
Explain Tonsils and where they are located.
Tonsils
- Simplest lymphoid organs; form a ring of lymphatic tissue around the pharynx
- Location:
- Palatine tonsils – either side of the posterior end of the oral cavity
- Lingual tonsils – lie at the base of the tongue
- Pharyngeal tonsil – posterior wall of the nasopharynx
- Tubal tonsils – surround the openings of the auditory tubes into the pharynx
Explain MALT.
MALT – mucosa-associated lymphatic tissue:
- Peyer’s patches, tonsils, and the appendix (digestive tract)
- Lymphoid nodules in the walls of the bronchi (respiratory tract)
MALT protects the digestive and respiratory systems from foreign matter
