2 A&P II Chapter 20 Lymphatics Flashcards
What is the function of the lymphatic system?
Returns fluids that have leaked from the blood vascular system back into the blood
What are the three parts of the lymphatic system?
- Network of capillary vessels
- Lymph
- Lymph nodes
What is lymph?
The fluid in the vessels
What do lymph nodes do?
Clean the lymph as it passes through
Are lymphatic vessels more similar to arteries or veins?
Veins
What do the ends of lymphatic vessels look like?
Closed on one end
What are the lymphoid organs?
Spleen
Thymus
Tonils
Lymph nodes
What pressures force fluid in and out of the capillaries?
Hydrostatic pushes out, osmotic pulls in
What end is fluid pushed out and pulled in at?
Arteriole end pushes fluid out, venous end pulls it back in
What happens to the fluid that remains in the tissue space?
Becomes part of interstitial fluid
Why must the fluid be returned back to the capillaries?
To maintain blood volume
What is interstitial fluid called once it enters the lymphatic vessels?
Lymph
Where do lymphatic vessels flow?
One way towards the heart
Where are lymphatic capillaries absent?
Teeth, bone, marrow, CNS, portion of spleen, avascular structures (cartilage, epidermis, cornea)
What are lymphatic capillaries determining characteristic?
Very permeable
Why are lymphatic vessels so permeable?
Endothelial cells are not tightly joined
What are minivalves composed of?
Endothelial cells are not tightly joined and their edges of adjacent cells overlap
Why don’t lymphatic capillaries collapse?
Collagen filaments anchor endothelium so any increase in fluid opens minivalves, rather than causing the vessels to collapse
What do lymphatic vessels lack structurally?
Basement membrane
What happens when the fluid pressure in the interstitial space is greater than the pressure in the lymphatic capillaries?
Minivalves flap open allowing fluid to eneter
What happens when the pressure is greater inside the lymphatic capillaries?
Valves are forced shut, preventing lymph from leaking out
Proteins in the interstitial fluid can/cannot easily enter the lymphatic capillaries
Can easily enter
What happens to a lymphatic capillary’s permeability when tissues are inflamed?
They develop openings that allow the uptake of large particles like cell debris, pathogens, and cacer cells
What are lacteals?
A special set of lymphatic capillaries that transport absorbed fat from the small intestine tot he blood stream
What is chyle? Where does it drain from?
Fatty lymph, draining from fingerlike villi of the intestinal mucosa
What is the progression of lymphatic vessels?
Capillaries, vessels, trunks, ducts
How many layers do collecting lymphatic vessels have?
Same three tunics as veins
How are lymphatic vessels different from veins?
Thinner walls, more valves, more anastomoses, only one way flow
What do superficial lymphatic vessels follow?
Superficial veins
What do deep lymphatic vessels follow?
Deep arteries
What are the lymphatic ducts?
- Lumbar
- Bronchomediastinal
- Subclavian
- Jugular
- Intestinal
What are the two lymph ducts?
- Thoracic
2. Right lymphatic duct
What drains into the right lymphatic duct?
Right side of head, neck, thorax, and upper limb
What does the cisterna chyli drain?
The lumbar and intestinal trunks
What does the thoracic duct drain?
The lymph in the cisterna chyli, left thorax, head, neck, and upper limb
What circulation do the terminal lymphatic ducts empty into?
Subclavian venous circulation
What is another name for lymph?
Chyle
Is lymphatic a low or high pressure circuit?
Low pressure
What mechanisms does the lymphatic system use since it does not have a pump? (5)
- Milking of skeletal muscle
- Pressure change in thorax during breathing
- Valves to prevent backflow
- Pulsations of nearby arteries help flow
- Smooth muscle in larger vessel walls pump lymph along
What are the characteristics of lymph transport?
Sporadic and slow
What is lymphedema?
Anything that prevents normal return of lymph to the blood
What are some examples of what would cause lymphedema?
Radiation therapy, surgical removal of duct, malignancy, blockage from tumor
How does lymphedema resolve?
Eventually vessels grow and drainage reestablishes
What is the concern with lymphedema?
Tissues and fluid are at high risk for infection
How much lymph do the lymphatic capillaries drain every day?
About 3 liters
Where do lymphocytes arise?
Bone marrow
What are the two types of lymphocytes?
T and B
What do lymphocytes do?
Protect the body against antigens - anything that will cause an immune response
What do activated T cells do?
Manage immune response, some directly attack and destroy infected cells
What do B cells do?
Protect the body by producing plasma cells
What are plasma cells?
Secrete antibodies into the blood, which mark antigens for destruction by phagocytes
What does a macrophage do?
Phagocytize foreign substances and help activate T cells
What do dendritic cells do?
Capture antigens and bring them back to the lymph nodes
What do reticular cells do?
Produce the reticular fiber stroma, which is the network that support the other cell types
What happens at lymphoid tissues?
Houses and provides a proliferation site for lymphocytes
What is lymphoid tissue made of?
Reticular fibers (except thymus)
What is a primary lymphoid tissue?
Site where stem cells divide and become immunocompetent
What are some examples of primary lymphoid tissue?
Bone marrow and thymus