Lymphatic system Flashcards
List the 3 main functions of the lymphatic system
- Immunity: fluids from all capillary beds are filtered at lymph nodes by immune cells, they’re read to respond to foreign cell or chemicals encountered.
- Lipid absorption: Lacteals in small intestine absorb and transport dietary lipids
- Fluid recovery: absorbs plasma proteins and fluid from tissues and returns it to the bloodstream (subclavian veins). Interference with lymphatic drainage leads to severe edema.
Describe the structure of lymph and lymphatic vessels
Clear, colourless fluid similar to plasma but ↓ protein. Formed from fluid leaked out of the capillaries.
Order the flow of lymph from smallest to largest of lymphatic vessels
Lymphatic vessels larger than capillaries are composed of 3 layers:
Tunica internal endothelium and valves.
Tunica media: elastic fibers, smooth muscle
Tunica externa: thin outer layer.
List 5 mechanisms by which lymphatic return is achieved
Skeletal muscle contractions with valves (preventing back-flow).
Rhythmic contractions of lymphatic vessels
Stretching of vessels stimulates contraction
Thoracic pump aids flow from abdomen cavity to thoracic cavity.
Rapid flowing blood in subclavian veins, draws lymph into it.
Name the major types of lymphatic cells and state their function
Natural killer (NK) cells - (lymphocyte) responsible for immune surveillance.
T lymphocytes (T cells) function to recognize and attack foreign antigens, mature in Thymus.
B lymphocytes (B cells): activation causes proliferation and differentiation into plasma cells that produce antibodies.
Antigen presenting cells - help recognize foreign antigens.
Macrophages - egulf bacteria
Dendritic cells: in epidermis, mucous membranes and lymphatic organs.
Reticular cells: makes the structure of the lymph nodel
Describe the structure and function of lymph nodes
Their are two functions to filter lymph and act as a site of T and B cell activation.
- Sinuses
- Outer cortex
- Germinal center
- Inner cortex
- Medulla
Describe the structure and function of the thymus
The thymus is a lymphatic organ located in superior mediastinum.
It contains reticular epithelial cells which:
1 Form blood-thymus barrier in cortex Isolates developing T cells from foreign antigens.
2 Secretes hormones (thymopoietin, thymulin and thymosins).
3 Promote development and deployment of T lymphocytes
Describe the structure and function of the spleen
Largest lymphatic organ located between diaphragm, stomach and left kidney.
Removes expired RBC. Appears red pulp: sinuses filled with erythrocytes. Blood production in fetus. Blood reservoir in case of blood loss. Immune reactions.
Differentiate between the two major categories of immune mechanisms.
First line of defense
Expulsion- vomit, sneeze, cough.
Mechanical barriers - skin
Chemical barriers: secretions, pH
Second line of defense
Phagocytosis, natural killer cells
Complement system
Inflammation/fever
Innate immunity: In place at birth, first and second line of defense
Adaptive immunity: Develops in response to a particular invader, third line of defense
Describe the mechanical and chemical barriers of defense.
First line of defense is a mechanical and chemical barrier. Goal to prevent organisms from entering the body.
Second line: recognize, neutralize and destroy invaders.
- Phagocytic cells
- Antimicrobial proteins
- Natural Killer
- Inflammatory response
- Fever
Define phagocytosis
Ingestiion and destruction of pathogens by phagocytic cells.
- Extend foot-like projections towards microorganisms
- Pseudopods encircle the microorganisim in a phagosome.
- Lysosomes fuse with phagosome releasing digestive enzymes and hydrogen peroxide - killing the organisims.
- Digestion products released by exocytosis. Innate defnese but it also plays a role in adative immunity
Explain the role of interferon, complement and natural killer cells as they relate to immune defense.
Antimicrobial proteins - interferon.
Interferon is a protein synthesized and released into circulation by certain cells invaded by viruses to signal other cells to enter a protective antiviral state
2.Complement: The classical pathway is initiated by a microbe bound to antibodies. → The alternate pathway is initiated by polysaccarides on the surface of a microbe. Involves a multistep cascade that results in holes being punched in invading microbe.
- NK cells play a major role in destruction of both tumors and virally infected cells.
They are cytotoxic → granules in their cytoplasm contain special proteins → perforin forms pores in the cell membrane of the target cell for apoptosis.
Explain the process of inflammation.
Inflammation is a process that involves aspects of innate immune response that we have already looked at. Role is to: Destroy the agent causing injury
Limit the effects of the agent on the rest of the body.
Repair or replace damaged tissue.
5 Cardinal signs:
1 Redness
2 Swelling
3 Heat
4 Pain
5 Loss of function.
Acute inflammation 2 phases:
- Vascular creates wound, constrict and dilate. (mast cells) Vasodilation - slows blood flow, ↑ the concerntration of inflammatory cells in the area. Vessel permeability - ↑ allowing plasma fluid into flamed tissue.
- Second is cellular: specific cell are draw to the site of injury to combat injury. Phagocytosis & diapedesis - cytokines released by activated macrophages make cell walls sticky, once stuck leukocytes migrate into the tissue so they can attack microorganisms.
List 4 inflammatory mediators and describe how they contribute to the inflammatory response.
Histamine (released by basophils and mast cells) - vasodilation, ↑ vascular permeability.
Prostaglandins (derived from cell membranes when damaged) - ↑ vascular permeability, sensitise nociceptors.
Leukotrienes released by leukocytets and other cells - ↑ vascular permeability, attract phagocytes by chemotaxis.
Complement (group of plasma proteins) - attrach neutrophil by chemotaxis, promote chemotaxis
Describe 3 benefits of fever.
1 Fever is a body-wide repsonse to infection induced by cytokines (pyrogens) and mediated prostoglandins.
2 Kills bacteria or inhibits growth 3 Promotes destruction of viral infected cells 4 Facilitate immune response Enhance phagpcytosis
