Wk 6: Lymphatic & Immune System Flashcards
What does the immune system contain
- no organs or tissues
- Consists of cells & proteins located in blood & tissue of systems
What does the lymphatic system consist of
- Group of organs & tissues
- Lymphatic vessels - blind ended tubes
- Lymphatic tissues & organs
What is the function of the lymphatic system
Drains body fluid & returns it to the bloodstream (blood vessels are leaky, fluid in interstitial space)
What is lymph
Interstitial fluid once it has entered the lymphatic system
What’s it called when the lymphatic system is blocked & there is accumulation of interstitial fluid
Lymphedema
Through what vessels does the lymph travel through to circulation
- Lymphatic capillaries
- Lymphatic vessels
- Lymphatic ducts
- Circulatory system
What are lymphatic capillaries composed of
One cell thick layer of endothelial cells
What are the lymphatic capillaries called in the GI system
Lacteals
Function of lacteals in the GI system
Transport dietary lipids & lipid soluble vitamins to bloodstream
What parts of the body does the right lymphatic duct drain
- Right side of head
- Thorax
- Right upper limb
What parts of body does the thoracic duct drain
The rest of the body (left upper limb, both lower limbs etc.)
WHere do immune cells arise from & from what precursor cells
- Arise in the bone marrow
- Arise from hematopoietic stem cells
Function of phagocytic cells
Ingest pathogens to destroy them
Function of lymphocytes
For adaptive immunity (slower than innate immunity, but more specific)
Function of cells with cytoplasmic granules
Immune responses against parasites & viruses
3 types of lymphocytes
- B cells
- T cells
- NK cells
What do B cells do (2)
- Express B cell receptors that bind antigens on pathogens to kill them
- Differentiate into plasma cells that secrete antibodies
Functions of T cells
- Secrete soluble factors:
1. Communicate with other immune cells
2. Or destroy cells infected with pathogens
Function of NK cells
- Contain cytotoxic granules in cytoplasm to defend against viruses & certain cancers
What are the 2 primary lymphoid organs
- Bone marrow
- Thymus gland
What are the 3 secondary lymphoid organs
- Lymph node
- Spleen
- Mucosa-associated lymphoid tissue (MALT)
Where do T cells mature
Thymus gland
what are the 2 lobes of the thymus gland called
- Thymic lobules (corpuscles)
The 2 regions of the thymic lobules
- Outer cortex - immature T cells (thymocytes)
- Inner medulla - less packed w cells = lighter colour in histological stain
What are lymph nodes
Clusters of lymphatic tissue
Where are lymph nodes located
Along lymphatic vessels
What kind of capsule do lymph nodes have
External connective tissue capsule
What happens to lymph as it travels through the lymph nodes
- Lymph flows in through afferent lymphatic vessels
- Pathogens are trapped in reticular network
- Pathogens eliminated by leukocytes & dendritic cells
- Clean lymph drains out through efferent lymphatic vessels at hilum
Whats in the germinal centres of lymph nodes & what do these do
- Germinal centres contain dividing B cells surrounded by B cells
- Any pathogens in the lymph as it passes through the nodes will pass through germinal centres & will be monitored by immune cells
Function of MALT
Protect mucous membranes exposed to large numbers of pathogens
The 3 types(?) of MALT
- Tonsils
- Peyers patches
- Appendix
what are peyers patches
Aggregated lymphoid nodules in the ileum
What are the 3 main tonsils
- Pharyngeal
- Palatine
- Lingual
What are the epithelium lining indents in tonsils & what is the function of these
- Tonsillar crypts
- Traps bacteria & debris - pathogens will be exposed to germinal centres (containing B & T cells) - immune response
Function of M cells
- Specialised endothelial cells that sample material from intestinal lumen, transport the material to peyers patches & amount an adaptive immune response
6 parts of the non specific immune system
- Physical barriers
- Phagocytes
- NK cells
- Interferons
- Complement
- Inflammation
What are interferons
Chemicals released by lymphocytes, macrophages & viral infected cells
Function of interferons
- Cells infected w viruses secrete interferons which travel to adjacent cells & induce them to make antiviral proteins
- Defend against viral infection
What does the complement system do
Binds pathogen membrane, activates it & labels it for phagocytosis
Explain the inflammatory response
- Pathogen enters tissue
- There is tissue damage
- MAst cells release histamine
- Histamine causes: increased blood flow, dilation of blood vessels & increased vessel permeability
- All of the above lead to attraction of phagocytes, complement & clotting factors
- This leads to release of cytokines
- Pathogen removal
- Tissue repair
What does binding of an antigen to a B cell induce the cell to do
Differentiate into plasma & memory cells
What do plasma cells do in antigen mediated immunity
Produce antibodies which help eliminate invading pathogens
What do memory cells do in antigen mediated immunity
Deal with subsequent exposure to same antigen
How does an APC present an antigen
- Antigen presented to T cell by antigen presenting cell via its major histocompatability complex (MHC)
- Pathogen phagocytosed & placed in vesicle
- Pathogen digested & antigen extracted
- Antigens bind w MHC proteins that enter vesicle
- Released from vesicle to outer surface of cell membrane
What markers do activated T cells express in cell mediated immunity
- CD4
- CD8 markers
What do the CD4&8 markers do in cell mediated immunity
They keep the T cell in close contact w APC
WHat cells are activated by CD4 & CD8 bearing T cells
Helper T cells & Cytotoxic cells
Function of cytotoxic T cells in cell mediated immunity
Induce apoptosis of infected cells
