22. Lymphatic System Flashcards
Lymphatic System
returns fluids that have leaked from the blood vascular system back into the blood
three parts of lymphatic system
- Network of lymphatic vessels
- Lymph = fluid contained in those vessels
- Lymph nodes – cleanse the lymph as it passes through them
Lymphoid Organs & Tissues
- provide the structural basis of the immune system
- House phagocytic cells and lymphocytes which play roles in the body’s defense mechanisms and resistance to disease eg. spleen
- Largest lympathic organ = spleen
lymphatic vessels
- are elaborate networks of drainage vessels that collect the excess interstitial fluid and return it to the bloodstream
- Lymphatic vessels form a one-way system in which lymph flows ONLY TOWARD the heart!!
Lymphatic Capillaries
Weave between the tissue cells and blood capillaries in the loose connective tissues of the body
What 2 unique structural modifications allow lymphatic capilliaries to be EXTREMELY permeable
1) Endothelial cells: not tightly joined, but overlap each other loosely forming easily opened flaplike minivalves
2) Collagen filaments: anchor endothelial cells to surrounding structures
an increase in interstitial fluid volume will open the minivalves
Pressure greater in interstitial space:
• minivalve flaps open
• fluid enters lymphatic capillary
Pressure greater in lymphatic capillary,
• forces endothelial minivalve flaps shut
• preventing lymph from leaking back out as the pressure moves it along the vessel
Structure of Collecting Lymphatic Vessels
have the same three tunics as veins
thinner walls and more internal valves
Lymphatic Trunks
drain fairly large areas of the body
named mostly for the regions from which they drain lymph
Lymphatic Ducts
Right Lymphatic Duct
drains lymph from the right upper limb and the right side of the head and thorax
Thoracic Duct
much larger because receives lymph from the rest of the body
Lymph Flow
Lymphatic Capillaries (smallest) –> Collecting Lymphatic Vessels –> Lymphatic Trunks –> Lymphatic Ducts (largest)
Lymph Transport
• low-pressure conduits
• use the same mechanisms that promote venous return
> milking action of active skeletal muscles
> pressure changes in the thorax during breathing
> valves to prevent backflow
List 3 Lympch Cell Types
- Functions
- Subcells
1) Lymphocytes > T lymphocytes (T cells) > B lymphocytes (B cells) 2) Macrophages: 3) Reticular Cells:
Lymphocytes Function/ Subtype functions
1) Lymphocytes – mediate immune responses, arise in red bone marrow and mature into one of two main types
i) T lymphocytes (T cells): they mature in thymus gland, manage the immune response, directly attack and destroy infected cells,
ii) B lymphocytes (B cells): mature in bone marrow, Protect the body by producing plasma cells that secrete antibodies, Antibodies mark antigens for destruction by phagocytes or other means
B-lymphocytes (B cells) give rise to:
2
a) Plasma Cells – produce antibodies that will attach to foreign cells (antigens) and destroy them
b) Memory B Cells – “remember” pathogens encountered and can have a rapid response if it is detected again
T-lymphocytes (T cells) give rise to:
4
a) Effector T Cells (cytotoxic T cells) – secrete cytotoxic agents that destroy virus-invaded cells and cancer cells
b) Helper T Cells – secrete chemical messengers to activate T and B cells as well as macrophages
c) Regulatory T Cells – act to control immune responses/suppressors
d) Memory T Cells – “remember” antigen so can have rapid immune response to second encounter
