Week 5 Flashcards
What is the Lymphatic System?
System that returns fluids that have leaked from blood vessels back to the blood. Pathogens travel throughout body via lymphatics
What does the lymphatic system consist of?
Consists of three parts:
1. Network of lymphatic vessels (lymphatics)
2. Lymph – fluid in vessels
3. Lymph nodes – cleanse lymph
Function of lymphatic vessels (lymphatics)
Return interstitial fluid and leaked plasma proteins back to blood
~3L/day
What is lymph?
It is the interstitial fluid that enters
lymphatics
Where do lymphatic vessels flow towards?
One-way system; lymph flows
toward heart
What do Lymphatic vessels include:
Lymphatic vessels include:
– Lymphatic capillaries
– Collecting lymphatic vessels – Lymphatic trunks and ducts
Lymphatic vessels diagram
What are lymphatic capillaries?
Similar to blood capillaries, except:
• Very permeable (take up proteins, cell debris, pathogens, and cancer cells)
– Endothelial cells overlap loosely to form
one-way minivalves
– Anchored by collagen filaments,
preventing collapse of capillaries; increased ECF volume opens the minivalves
Lymphatic capillaries are absent from:
bones, teeth, bone marrow, and CNS
What are lacteals?
Lacteals: specialized lymph capillaries present in intestinal mucosa
Lacteals function
Absorb fat and deliver fatty lymph (chyle) to the blood
What are Lymphatic Collecting Vessels ?
Similar to veins, except:
• Have thinner walls, with more internal valves
• Anastomose more frequently
– Collecting vessels in skin
travel with superficial veins
– Deep vessels travel with arteries
What do the lymphatic collecting vessels travel with?
Collecting vessels in skin
travel with superficial veins
What do the deep lymphatic collecting vessels travel with?
Deep vessels travel with arteries
Lymphatic Collecting Vessels diagram
What do lymphatic vessels include:
Lymphatic Capillaries, Lymphatic Collecting Vessels, Lymphatic Trunks and Lymphatic Ducts
What are lymphatic trunks formed by?
Formed by union of largest collecting ducts • 2x lumbar
• 2x bronchomediastinal • 2x subclavian
• 2x jugular
• 1x intestinal
Diagram of major lymphatic trunks and ducts.
What ducts are the lymph delivered into?
– Lymph delivered into one of two large ducts
• Right lymphatic duct drains rightupperarmandrightside of head and thorax
• Thoracic duct arises as cisterna chyli; drains rest of body
Where do the 2 large lymphatic ducts empty unto?
Each empties lymph into venous circulation at junction of internal jugular and subclavian veins on its own side of body
Diagram of lymphatic trunks?
What is the Lymph fluid propelled by?
Lymph fluid is propelled by:
– Milking action of skeletal muscle
– Pressure changes in thorax during breathing
– Valves to prevent backflow
– Pulsations of nearby arteries
– Contractions of smooth muscle in walls of lymphatics
What are the lymph fluids?
Interstitial fluid, leukocytes, and reticular cells
What is interstitial fluid?
Interstitial Fluid; water, carbohydrates, fats & proteins
What do Leukocytes consist of?
– Lymphocytes
• Arise in red bone marrow
• Protect against foreign antigens
– Bacteria and bacterial toxins, viruses, mismatched RBCs, cancer cells
• Mature into one of two main varieties:
– T cells (T lymphocytes)
» Manage immune response
» Attack and destroy infected cells
– B cells (B lymphocytes)
» Produce plasma cells, which secrete antibodies
(antibodies mark antigens for destruction by phagocytosis or other means)
– Macrophages
• phagocytize foreign substances; help activate T cells
– Dendritic cells
• capture antigens and deliver them to lymph nodes; activate T cells
What do reticular cells produce ?
produce reticular fibre stroma that supports other cells in lymphoid organs
Function of Lymphoid Organs and Tissues
• Provide structural basis of immune system
• House phagocytic cells and lymphocytes
What structures do Lymphoid Organs and Tissues include?
Structures include spleen, thymus, tonsils, lymph nodes, other lymphoid tissues
What does Lymphoid Tissue house?
Houses, and provides proliferation site for lymphocytes
Lymphoid tissue is known as the surveillance…
Surveillance vantage point for lymphocytes and macrophages
What does lymphoid tissue consist of?
Surveillance vantage point for lymphocytes and macrophages
What is largely reticular connective tissue?
- Largely reticular connective tissue – type of loose connective tissue
What are the 2 main types of Largely reticular connective tissue?
Two main types:
– Diffuse lymphoid tissue of lymphoid cells and reticular fibres in almost
every body organ
•Larger collections in lamina propria of mucous membranes
– Lymphoid follicles/nodules are solid, spherical bodies of tightly packed lymphoid cells and reticular fibres
• Germinal centres of proliferating B cells
• Mayformpartoflargerlymphoidorgans
• Isolated aggregations,e.g.palatinetonsils,Peyer’spatches(SI)
•Similar to lymph nodes except that they are not surrounded by a connective
tissue capsule
What are lymph nodes?
Principal lymphoid organs of body
Where are lymph nodes found?
• Embedded in connective tissue, in clusters along lymphatic vessels
• Near body surface in inguinal, axillary, and cervical regions of body
Functions of lymph nodes:
- Filter lymph—macrophages destroy microorganisms and debris
- Immune system activation—lymphocytes activated and mount attack against antigens
What is the largest lymphoid organ?
Spleen
Where is the spleen found?
Found in the left upper quadrant of the abdomen
What artery and vein is the spleen served by?
Served by splenic artery and vein, which enter and exit at the hilum
Functions of the spleen?
• Functions:
– Site of lymphocyte proliferation, and immune surveillance and response – Cleanses blood of aged cells and platelets; macrophages remove debris – Stores breakdown products of RBCs (e.g., iron) for later use
– Stores blood platelets, and the precursors of macrophages and dendritic
cells
Picture of spleen location
Where is the thymus found?
Found in inferior neck; extends into mediastinum; partially overlies heart
Does thymus continuously grow?
Stops growing during adolescence, then gradually atrophies
What are most thymic cells?
Most thymic cells are lymphocytes