Chapter #22: The Lymphatic System Flashcards
Lymphatic system (lymphoid system)
-Protects us against disease
-Lymphatic system cells respond to
–Environmental pathogens
–Toxins
–Abnormal body cells, such as cancers
-contain lymphocytes
Lymphocytes
-Part of the immune response
-Identify, attack, and develop immunity to specific pathogens
-Make up 20–40 percent of circulating leukocytes
-Most are stored, not circulating
-Divide in cortex
-Migrate into medulla
-Mature T cells leave thymus by medullary blood vessels
Components of lymphatic system
- Lymph
- Lymphatic vessels
- Lymphoid tissues and lymphoid organs
- Lymphoid cells
Lymph
A fluid similar to plasma but without plasma proteins
Lymphatic vessels
-Carry lymph from peripheral tissues to veins
-Superficial lymphatics
-Deep lymphatics
–Larger vessels that accompany arteries and veins
-Join to form large lymphatic trunks that empty into two major collecting vessels
–Thoracic duct
–Right lymphatic duct
Lymphoid tissues and lymphoid organs
Scattered throughout body
Lymphoid cells
-Lymphocytes, phagocytes, and other cells
-Immune system cells and supportive cells in lymphoid tissues
Lymphocytes are produced in
-Primary lymphoid tissues and organs
-Red bone marrow and thymus
Lymphocytes are activated in
-Secondary lymphoid tissues and organs
-Tonsils, MALT, lymph nodes, and spleen
Functions of lymphatic system
-Produce, maintain, and distribute lymphocytes and other lymphoid cells
-Return excess fluid to bloodstream
–Maintain normal blood volume
-Transport hormones, nutrients, and wastes
Lymphatic capillaries
-Overlap of endothelial cells acts as one-way valve
–Allows fluids, solutes, viruses, and bacteria to enter
–Prevents their return to intercellular spaces
Lymph flows
lymphatic capillaries to larger lymphatic vessels with one-way valves
Lacteals
-Special lymphatic capillaries in small intestine
-Transport lipids from digestive tract
Thoracic duct
-Base expands to form cisterna chyli, which receives lymph from
–Right and left lumbar trunks
–Intestinal trunk
-Inferior segment collects lymph from
–Left bronchomediastinal trunk
–Left subclavian trunk
–Left jugular trunk
-Empties into left subclavian vein
Right lymphatic duct
-Collects lymph from
–Right jugular trunk
–Right subclavian trunk
–Right bronchomediastinal trunk
-Empties into right subclavian vein
Lymphedema
-Blockage of lymph drainage from a limb
-Causes severe swelling
-Interferes with immune system function
Types of Lymphocytes
- T cells (Thymus-dependent)
- B cells (Bone marrow-derived)
- NK cells (natural killer cells)
Lymphoid tissues
Connective tissues dominated by lymphocytes
Lymphoid nodules (lymphatic nodules)
-Tissue with densely packed lymphocytes
-Germinal center contains dividing lymphocytes
Where are lymphoid nodules distributed?
-Lymph nodes
-Spleen
-Respiratory tract (tonsils)
-Along digestive, urinary, and reproductive tracts
Five tonsils in wall of pharynx
-Pharyngeal tonsil (adenoid)
-left and right palatine tonsils
-two lingual tonsils
Tonsilitis
Inflammation of tonsils, especially palatine tonsils
Mucosa-associated lymphoid tissue (MALT)
-Lymphoid tissues associated with digestive system
-Aggregated lymphoid nodules (Peyer’s Patches)
–Clustered deep to intestinal epithelial lining
Appendix (vermiform appendix)
-Contains a mass of fused lymphoid nodules
-where the small intestine meets the large intestine
Lymphoid organs
-Lymph nodes
-Thymus
-Spleen
What are lymphoid organs separated by?
Separated from surrounding tissues by a fibrous connective tissue capsule
Efferent Vessel vs Afferent vessel
-Efferent vessel = contains anything leaving
-Afferent vessel = contains anything entering
Trabeculae
-Bundles of collagen fibers
-Extend from capsule into interior of lymph node
Hilum
Shallow indentation where blood vessels and nerves reach lymph node
Afferent lymphatics
Carry lymph from peripheral tissues to lymph node
Efferent lymphatics
-Leave lymph node at hilum
-Carry lymph to venous circulation
Lymph flow through nodes
- From subcapsular space
- Through outer cortex
- Through the core (medulla)
- Finally, into efferent lymphatics at hilum
Lymph node function
-Purify lymph before return to venous circulation
–Remove antigens
-Antigens released due to infection
–Enter lymph and stimulate immune cells in lymph nodes
Lymphoid tissues and lymph nodes
-Monitor peripheral infections
-Respond before infections reach vital organs
Lymph nodes of gut, trachea, lungs, thoracic duct
Protect against pathogens in digestive and respiratory systems
Largest lymph nodes
-In groin, axillae, and base of neck
-Swell in response to infection
Lymphadenopathy
-Chronic or excessive enlargement of lymph nodes
-May indicate infections or cancer
Thymus
-Located in mediastinum
-Divided into two thymic lobes
-Septa divide lobes into smaller lobules
Thymic lobule
-Dense outer cortex
-Pale central medulla
Thymic hormones
Thymosin
Thymosin
Promotes development and maturation of T cells
Functions of the spleen
- Removal of abnormal blood cells by phagocytosis
- Storage of iron recycled from red blood cells
- Initiation of immune responses by B cells and T cells
–In response to antigens in circulating blood
Location of the spleen
-Attached to stomach
-Contacts diaphragm and left kidney
Histology of the spleen
-Cellular components within capsule make up pulp
–Red pulp contains many red blood cells
–White pulp resembles lymphoid nodules
Spleen function
-Phagocytes and other lymphocytes in spleen
–Identify and attack damaged and infected cells in circulating blood
