General Functions of the Lymphatic System
1. Help maintain H20/electrolyte balance
2. Help defend body tissues from infections
3. Absorb fats
How does the lymphatic system help maintain water/electrolyte balance?
By moving excess interstitial fluid (ISF) from interstitial spaces (ISS) into lymph, and back into blood.
How does the lymphatic system help defend body tissues from infections?
1. "Filtering" pathogens from lymph
2. Supporting immune activities of lymphocytes & macrophages
Where/how does the lymphatic system absorb fats?
From intestines via lacteals to reduce blood vicosity
Lymph Formation
1. Hydrostatic pressure forces plasma from blood capillaries into ISS, where it becomes ISF
2. Some ISF becomes ICF, transcellular fluid (TCF) or blood via osmotic pressure
3. Remaining ISF is moved by hydrostatic pressure into highly permeable ends of lymphatic capillaries and become "lymph"
How many liters of water and plasma protein enter the interstitial spaces each day?
2-4 liters of water
1/4 to 1/2 of plasma protein
Interstitial
extra-cellular spaces in tissues
What does transcellular fluid (TCF) include?
1. Cerebral Spinal fluid (CSF)
2. Synovial fluids
3. Peritoneal fluid
4. Plural fluid
5. Pericardial fluid
6. Fluids in the eye
7. Fluids in the digestive system
8. Fluids in the urinary system
9. Fluids in the respiratory tract
What is lymph?
It is essentially ISF that has entered the lymphatic pathway
What ions does lymph contain high concentrations of?
Na+
Cl-
HCO3-
What ions does lymph contain low concentrations of?
K+
CA 2+
MG 2+
PO4 3-
SO4 2-
What are the major lymphatic organs?
1. Lymph Nodes
2. Thymus
3. Spleen
4. Mucosa/Gut - Associated Lymphatic Tissue (MALT or GALT)
Cervical lymph nodes
Axillary lymph nodes
Inguinal lymph nodes
Lymph Nodes - Structure
Bean-shaped
Encapsulated by dense fibrous connective tissue containing many nodules within many sinuses
Nodules
Dense masses of lymphocytes and macrophages
Lymph Nodes - Function
Produce lymphocytes
Lymphocytes
Help macrophages "filter" lymph by removing pathogens and foreign substances from lymph before it enters venous blood.
Thymus
Thymus - Location
Anterior surface of mediastinum
Anterior to aortic arch
Inferior to manubrium
Thymus - Structure
Soft bi-lobed immune organ composed of lymphatic tissue and subdivided into lobules containing large numbers of lymphocytes
Thymus - Function
Produce & Secrete hormone Thymosin
-Very large in fetus & grows slightly during childhood
-After age 14 begins to undergo involution & becomes quite small in adults
-In the elderly, has been replaced almost entirely by fibrous and fatty tissue. Is barely distinguishable
Thymosin
Stimulatees "undedicated" lymphocytes to develop into "dedicated" T-cells
What is the largest lymphatic organ?
Spleen
Spleen
Spleen - Location
Left hypochondriac region
Spleen - Structure
Similar to a large lymph node
Encapsulated and subdivided into lobules with blood filled spaces and nodules containing lymphocytes
What are the four MAJOR functions of the spleen?
1. Serves as a blood reservoir at prolonged periods of inactivity
2. Storage site for thrombocytes and hemoglobin breakdown products
3. Site for lymphocytic proliferation. (multiplication of lymphocytes)
4. One of the sites for destruction of aged/defective RBCs and pathogens
Why is the spleen known as the erythrocyte graveyard?
That is where it recycles/destroys red blood cells and other pathogens
Other functions/characteristics of the spleen
1. Produce blood cells in fetus & sometimes resumes this role in adulthood in extreme cases of anemia
2. help activate defensive immune response
3. Highly vascular - vulnerable to trauma and infection
4. relatively dispensable organ
What body parts can take over the function of the spleen if it is removed?
Liver
Bone marrow
What lymphatic tissues are associated with the mucosa/gut and where are they located?
1. Tonsils - mouth/throat
2. Peyer's patches - small intestine
3. Vermiform appendix - large intestine
What are the three sets of tonsils and where are they located?
1. Palatine - post. oral cavity
2. Lingual - base of tongue
3. Pharyngeal (adenoids when inflamed) - post. wall of nasopharynx
Palatine tonsils
Lingual tonsils
Pharyngeal tonsils
Tonsils - Structure
Partially encapsulated lymph nodules containing lymphocytes
Tonsils - Function
Gather/remove pathogens from ingested food and inhaled air
Peyer's patches - Location
Scattered throughout mucosal lining of ileum
Peyer's patches - Structure
Large isolated
Peyer's patches - Function
Trap and destroy bacteria in small intestine
Vermiform Appendix - Location
Post./Medial surface of cecum
Vermiform Appendix - Structure
"Wormlike" tubular structure containing lymphatic tissue
Vermiform Appendix - Function
Breeding ground for intestinal flora and lymphatic tissue much like the tonsils
Lymphatic capillaries
Lymphatic vessels
Lymph capillaries - Location
Throughout body in ISS parallel to blood capillaries
Lymph capillaries - Structure
Very permeable close-ended tube composed of simple squamous e.
Lymph capillaries - Function
Receive excess ISF moved into lymph pathway via osmotic pressure
Lymph Vessels - Location
Between lymph capillaries/lymph nodes and lymph nodes/lymph trunks
Lymph Vessels - Structure
3 layers similar to veins
What are the three layers of lymph vessels & what makes them up?
1. Inner = endothelium with valves
2. Middle = smooth muscle
3. Outer = connective tissue
How to lymph vessels move lymph?
By using the milking action of skeletal muscles similar to veins (known as ******)
Lymph Vessels - Function
Transport lymph to lymph nodes and lymphatic trunks
Lymphatic Trunks - Location
Throughout trunk of body where larger lymphatic vessels merge
Lymphatic Trunks - Structure
Similar to veins
Lymphatic Trunks - Function
Drain lymph from relatively large regions of the body
What are the 5 regions of the body where lymphatic trunks train lymph from? (Each lymphatic trunk is named after the region it drains from)
1. Lumbar
2. Intestinal
3. Bronchomediastinal
4. Subclavian
5. Jugular
Identify the 5 lymphatic trunks
1. Intestinal
2. Subclavian
3. Lumbar
4. Jugular
5. Bronchomediastinal
How many collecting ducts are there and where to they drain?
2 collecting ducts
Drain into the subclavian vein on its respective side
Collecting Ducts - Location
Where groups of lymphatic trunks merge at two locations
Collecting Ducts - Function
Receive lymph from lymphatic trunks and empty the collected lymph into venous circulation at junction of Jugular and Subclavian Veins
Identify the 2 collecting ducts
1. Right lymphatic duct
2. Thoracic duct
Right Lymphatic Duct - Location and Function
-Upper right side of thorax and head. At union of R jugular, subclavian and bronchomdediastinal trunks
-Recieves lymphatic drainage from right arm and right side of thorax and head
Thoracic Duct - Location and Function
-Drains L. head/neck, arm, thorax, entire abdomen and both legs.
-Larger and longer with cisterni chyli (expanded upper region in upper abdominal cavity)