27. Lymphatic & Immune System Flashcards
Basics of lymphatic and immune systems
Lymphatic and immune systems are closely related to cardiovascular system
Lymphatic system returns excess tissue or interstitial fluid (filtered blood lost through capillaries) back to the bloodstream (fluid called lymph)
Immune system fights infections and builds immunity to diseases
Include several organs, lymph vessels, and lymph nodes throughout the body
Pathway of lymphatic vessels
Lymphatic capillaries (collect excess fluid from tissues)
Collecting lymphatic vessels (with lymph nodes attached)
Lymphatic trunks
Lymphatic ducts
Veins
Characteristics of collecting lymphatic vessels
Run with superficial veins in the extremities and deep arteries in the thorax and abdomen
Under low pressure, have many valves to prevent back flow (gives beaded appearance)
Same layers (tunics) as blood vessels, just thinner
Characteristics of lymph transport
Unaided by force of heartbeat
Propelled by skeletal muscle contraction, smooth muscle in vessels, and movement of limbs
Remaining stationary for long times results in edema (swelling due to excessive tissue fluid)
Characteristics of lymph nodes
Lymph capillaries have large one-way valves to take up a lot of fluid (also allows for bacteria, viruses, etc to enter lymphatic vessels)
Lymph nodes are found along collecting lymphatic vessels
Lymph nodes can become swollen from cancerous cells (not painful) or infection (painful)
Location and function of lymph nodes along collecting lymphatic vessels
Intersection of lymphatic and immune systems
Collect and destroy pathogens (contain lymphatic cells)
Large collections in neck (cervical), armpit (axilla), and groin (inguinal)
Characteristics of lymphatic ducts
Collecting lymphatic vessels drain into lymphatic trunks, which drain into lymphatic ducts
2 types: right lymphatic duct and thoracic duct
Right lymphatic duct
Drains lymph into right subclavian vein from right side of head, right upper extremity, and right side of thorax
Thoracic duct
Drains lymph into left subclavian vein from left side of head, left upper extremity, left side of thorax, and lower extremity
Starts at collecting sac called cisterna chyli in abdomen
Characteristics of immune system
Recognizes and attacks specific foreign molecules
Becomes more effective with each new exposure
Lymphatic (lymphoid) cells: in cardiovascular and lymphatic system
Include macrophages, dendritic cells, and lymphocytes
Macrophages
Monocytes that have migrated to lymphatic system from cardiovascular system
Phagocytosis of foreign substances
Dendritic cell
Found in lymphatic nodules (clusters of lymphatic cells)
Internalize antigens and present to other lymphatic cells
Lymphocytes
Most abundant cells in lymphatic system
3 types: T-lymphocytes, B-lymphocytes, and natural killer cells
T-lymphocytes
Most common lymphocyte (~80%)
Attack foreign cells directly
Have surface receptors for specific antigens
B-lymphocytes
15-30% of all lymphocytes
Have surface receptors for specific antigens
Release antibodies that attach to antigens, mark them for destruction by macrophages
Natural killer cells
Least common lymphocyte
Do not recognize specific antigens
Can kill a variety of infected cells
Characteristics of lymphoid tissue
Specialized connective tissue with many lymphocytes
Main battleground to fight infection
Found in 2 general locations:
Mucous membranes (digestive, respiratory, urinary, reproductive tracts) - called mucosa associated lymphoid tissue (MALT)
Called peyer’s patches in small intestines
All lymphoid organs (except thymus)
Types of lymphoid organs
Primary lymphoid organs: bone marrow and thymus (produce B and T lymphocytes)
Secondary lymphoid organs: lymph nodes, spleen, MALT, tonsils, appendix (store lymphocytes to fight microorganisms)
Characteristics of thymus
Lies just behind sternum
Prominent during childhood but atrophies in adults
Secretes hormones for maturation of lymphocytes
Characteristics of the spleen
Largest lymphoid organ
Divides into red and white pulp
White pulp- clusters of lymphatic cells to monitor blood for foreign material
Red pulp- extra supply of RBC’s and platelets
Characteristics of tonsils
Large clusters of lymphatic cells surrounded by connective tissue capsule
Locations:
Palatine, pharyngeal (adenoids), and lingual tonsils
Arranged in a circle around the entrance to your pharynx
Characteristics of the appendix
Worm like projection from beginning of large intestine
Contains lymphoid tissue and “good” bacteria that repopulates colon after infection
