Chapter 20: The Lymphatic System Flashcards
A hematopoietic stem cell will give rise to
erythrocytes
leukocytes
platelets
-all three types of formed elements found in the blood
Predict the outcome of an overdose of the hormone erythropoietin
The blood viscosity increases to levels that may induce heart attacks or strokes. making too many red blood cells
if a patient has pernicious anemia, the inability of the body to absorb vitamin B12, the patient
would have a decreased number of red blood cells
Lymphatic system
- > A network of vessels that absorbs fluid that leaks from the blood into surrounding tissues
- > about 3 liters of fluid leak out each day
- > if leakage continued unchecked the body would swell with fluid
- > one-way system: starts at the capillaries and dumps it back into the circulatory system via the subclavian
Lymphatic system: consists of 3 parts
- A network of lymphatic vessels (lymphatics)
- Lymph-fluid
- Lymph nodes, tissues and organs
- > a functional system.
Lymphatic system functions
- > returns interstitial fluid and leaked plasma proteins back into the blood
- once interstitial fluid enters lymphatics, it is called lymph (clear water)
->together with lymphoid organs and tissues, provide the structural basis of the immune system
area drained by right lymphatic duct
only does right side of the face and the right arm
area drained by thoracic duct
drains the left side of the face, left arm, the abdomen, both legs
Lymphatic vessels
-> one-way system, lymph flows toward the heart
- > lymph vessels (lymphatics) include:
- lymphatic capillaries
- lymphatic collecting vessels
- lymphatic trunks and ducts
*lymphatic capillaries
Similar to blood capillaries, except:
- > very permeable (take up cell debris, pathogens, and cancer cells)
- > endothelial cells overlap to form one-way minivalves
Lacteals: specialized lymph capillaries present in small intestines.
*absorb digested fat and deliver fatty lymph (chyle) to the blood
Lymphatic capillaries are blind-ended tubes in which
adjacent endothelial cells overlap each other, forming flaplike minivalves.
*lymphatic collecting vessels
Similar to veins, except:
- > have thinner walls, with more internal valves
- > anastomose (multiple pathways to get from one point to another) more frequently
Collecting vessels in the skin travel with superficial veins
-Deep collecting vessels travel with arteries
Regional lymph nodes
- cervical nodes
- axillary nodes
- inguinal nodes
Lymphatic trunks
Formed by the union of the largest collecting ducts
- > Paired lumbar
- > Paired bronchomediastinal
- > Paired subclavian
- > Paired jugular trunks
- > A single intestinal trunk
Lymphatic capillaries -> collecting vessels -> trunks
-> ducts
true
Lymphatic ducts
Lymph is delivered into one of two large ducts
* right lymphatic duct drains the right upper arm and the right side of the head and thorax
- Thoracic duct arises from the cisterna chyli(large sac) and drains the rest of the body
- > each empties lymph into venous circulation at the junction of the internal jugular and subclavian veins on its own side of the body
Lymph transport
Lymph is propelled by:
- pulsations of nearby arteries
- contractions of smooth muscle in the walls of the lymphatics
- milking action of active skeletal MM
- pressure changes in the thorax during breathing
Lacks an organ to act as pump, low pressure vessels
Lymphoid cells
Lymphocytes the main warriors of the immune system
->2 main varieties: T cells (T lymphocytes): mature in thymus
B cells (B lymphocytes): mature in bone marrow
Lymphocytes
T cells and B cells protect against antigens.
*Anything the body perceives as foreign-> bacteria and their toxins; viruses; mismatched RBCs or cancer cells
T cells:
*attack and destroy foreign cells
B cells:
*produce plasma cells, which secrete antibodies.
Other lymphoid cells
Macrophages:
*phagocytize/eat foreign substances and help activate T cells
Dendritic cells:
*capture antigens and deliver them to lymph nodes
Reticular cells:
*produce lymphoid tissue stroma (mattress) that supports other cells in lymphoid organs
… can enter lymphatic capillaries
bacteria, large proteins, interstitial fluid
Lymphoid tissue
- > houses and provides a proliferation site for lymphocytes
- > furnishes a surveillance vantage point
- > 2 main types:
a) diffuse lymphatic tissue
b) lymphatic follicles
Diffuse lymphatic tissue
- found in every organ in the body
- made of loose reticular CT
- larger collections appear in mucous membranes (i.e digestive tract) and lymphoid organs
Lymphatic follicles (nodules)
solid, spherical bodies of tightly packed reticular elements and cells
- Germinal center: composed of dendritic and B cells (enlarge when B cells are dividing and producing plasma cells)
- may form part of larger lymphoid organs (lymph nodes)
- NO T CELLS in the nodules
Primary lymph organs
- where B and T cells mature
- B cells mature in red bone marrow (where they originate, they don’t have to go anywhere to mature)
- T cells mature in thymus
