Lymphatic System Flashcards
What is the difference between an antibody and an antigen?
Antibody is a protein molecule released by a plasma cell & binds to a specific antigen
Antigen is a surface marker that the body perceives as foreign
What are the vessels in the lymphatic system called, where do they start and where do they end?
Vessels = lymphatics
Start: peripheral tissues
End: venous system
What is the fluid called in the lymphatic system ?
Lymph
What do the organs of the lymphatic system contain?
Many lymphocytes
What are the functions of the lymphatic system?
- produce, maintain and distribute lymphocytes
- maintain NFP (net filtration pressure) by returning fluid and solutes from interstitial fluid to blood
- distribute hormones, nutrients and waste
- removes foreign substances and aged/infected/cancerous cells
- provides structural basis of immune system
What is the lymph pathway?
Blood stream capillaries –> interstitial space –> Lymphatic capillaries –> lymphatic vessels –> Lymphatic trunks –> lymphatic ducts –> Venous blood
What are the differences between lymphatic capillaries and blood capillaries?
Lymph capillaries are:
- blind ended
- very permeable
- made of endothelial cells overlapping to make one way minivalves
- anchored by collagen filaments preventing capillary collapse
What is a lacteal?
Specialized lymph capillaries in the small intestinal mucosa –> absorb digested fat and bring chyle to the blood stream
What is chyle?
fatty lymph
*not brought to the liver (metabolized too quickly)
Where are lymphatic capillaries not found?
Bones, bone marrow, teeth and CNS
What are some of the properties of lymphatic vessels?
- lined by simple squamous epithelium
- surrounded by thin layer of connective tissue and small amounts of smooth muscle
- contain internal valves to ensure unidirectional flow
- anastomose often
- travel with blood vessels
What does anastomose mean?
mesh or plexus of vessels coming together –> 2 becoming 1
What do the lymphatic trunks do?
Drain different body regions
What areas do the right lymphatic duct and thoracic duct drain?
Right lymphatic duct drains right body superior to diaphragm
Thoracic duct drains everything else (right below diaphragm and entire left side)
How does lymph move through the body?
Very slowly –> not propelled by a pump and is a low pressure system
Lymph is propelled by the same things that promote venous return:
- respiratory pump
- valves
- skeletal muscle “milking”
AND
- pulsations of nearby arteries
- contractions of smooth muscle in walls of lymphatics
How does breathing help move lymph?
Changes pressures in the thorax and abdomen; negative pressures and volumes in the thorax help pull fluid
What are the classes of lymphocytes?
T cells (80%)
B cells (10-15%)
NK cells (5-10%)
What are the subtypes of T cells?
- Cytotoxic T cells –> attack foreign cells or infected body cells
- Helper T cells –> stimulate activation of T and B cells
- Suppressor T cells –> inhibit activation of T and B cells which helps establish and control the sensitivity of the immune response
What does a plasma cell do?
B Cells differentiated = Plasma cells
Produce and secrete antibodies responsible for antibody-mediated immunity (humoral)
What does an NK cell do?
NK = Natural killer
immune surveillance, attack foreign bodies, cells that are infected and cancer cells
How do NK cells work?
- unusual antigen (Ag) recognized by NK and becomes activated; NK adheres to target cell
- NK golgi moves so the face points at abnormal cell; Golgi produces secretory vesicles containing perforins
- Perforins are released at NK cell surface and diffuse across narrow gap separating NK cells from target
- Perforins create pores that make the abnormal cell unable to maintain the boundary between internal and external environments
What are the other lymphoid cells and their functions?
Macrophages: phagocytize foreign substances and help activate the T cells
Dendritic cells: capture antigens and deliver them to lymph nodes
Reticular cells: make stroma/framework so the organs don’t collapse
What is the difference between primary and secondary lymphoid organs?
Primary is where the B & T cells mature (bone marrow and thymus)
Secondary is where B & T cells encounter antigens (tonsils, lymph nodes, spleen, peyer’s patch and appendix)
Where do the T cells get their “education” and through which processes does this happen?
Thymus
Positive selection: T cells must first be able to recognize self MHC, if they cannot, they undergo apoptosis
Negative selection: T cells must fail to bind to the self-Ag because that would mean potential for an autoimmune disorder, cells that recognize self-Ag cells undergo apoptosis