Unit 13: Lymphatic System

Question 1

What does the lymphatic system consist of?

Answer 1

• one-way network of lymphatic vessels that collect about 10% of the extracellular fluid that leaked out from cardiovascular capillaries and return this fluid (now termed lymph) to the venous blood
• Lymph nodes along the vessel network that cleanse lymph as it passes through them
  
  • contain T and B lymphocytes that identify and remove
    bacteria, viruses, and cancer cells
• lymphoid cells, tissues, and organs support the functions of the lymphatic system

Question 2

What are the two body fluid compartments?

Answer 2

1) Intracellular fluid = found w/in cells (about 40% of body weight)

2) Extracellular fluid = found outside of cells; includes:
a) blood plasma (about 5% of body weight) - fluid in blood, some exits capillaries to form ISF
b) ISF (interstitial fluid) (about 15% of body weight) - fluid btw. cells w/in body (except blood cells which are surrounded by plasma - some moves into lymphatic capillaries to form lymph)
c) Lymph (about 1% of body weight) - fluid inside lymphatic vessels, returned to blood plasma

Question 3

Outline of lymphatic circulation

Answer 3

Lymphatic capillaries
to
lymphatic collecting vessels (w/ valves)
to
lymphatic ducts
to
subclavian veins

Question 4

Info about lymphatic circulation

Answer 4

Lymph enters lymphatic capillaries (closed-ended vessels that project into cardiovascular capillary beds)
- lymphatic capillaries in the small intestine also play a role in fat absorption

Lymphatic capillaries connect to larger lymphatic collecting vessels that have one-way valves
- lymph nodes along collecting vessels filter lymph (bacteria, debris)
- transports lymph fluid AWAY from tissues to:
1) R lymphatic duct (lymph from the R side of head, chest,
and arm) - drains into R subclavian vein re-entering
circulation
2) thoracic duct (lymph from below the ribs and the entire L side of body)
- collecting vessels from below the ribs converge to an
enlarged lymph vessel = cisterna chyli (this is the most
inferior portion of the thoracic duct)
- the thoracic duct drains into the L subclavian vein
reentering blood circulation

Fluid flows through lymphatic-collecting vessels largely as result of body movements (muscle contractions) that move the fluid toward the heart. One-way valves in the collecting vessels prevent back flow of blood.

Question 5

What are lymphoid tissues and organs and what do they include?

Answer 5

• they contain many lymphocytes and play a key role in the body’s IMMUNE SYSTEM (protect against disease)
• includes primary lymphoid organs and tissues and secondary lymphoid organs and tissues

Question 6

Info on primary lymphoid organs and tissues

Answer 6

a) locations where lymphoid stem cells divide and mature (become immunocompetent)
b) includes:
i. red Bone marrow
- all lymphocyte stem cells arise here
- site of B lymphocyte proliferation (mitosis) maturation
ii. Thymus gland
- early in development (fetal stage) lymphocyte stem cells
migrate here
- site of T lymphocyte proliferation (mitosis) and
maturation
c) mature lymphocytes move into blood stream and migrate to the secondary lymphoid organs/tissues

Question 7

Info on secondary lymphoid organs and tissues

Answer 7

• where lymphocytes detect and remove pathogens
• locations where lymphocytes are activated and proliferate further
  Includes:
  a) lymph nodes
  
  • small masses of lymphoid tissue along lymphatic
    collecting vessels
  • high concentrations of lymph nodes are located in:
    cervical (neck), axillary (armpit), inguinal (groin), intestinal,
    and pelvic regions
    b) spleen
  • located in L side of abdominal cavity just below
    diaphragm next to stomach
  • filters (cleans) blood by removing pathogens (organisms
    that can cause disease like bacteria or viruses), old and
    defective blood cells, and cellular debris
    c) Mucosal Associated Lymphoid Tissue (MALT)
  • trap and remove pathogens at points of entry into the
    body
  • includes tonsils, appendix, and other lymphoid tissues on
    mucous membranes
  • e.g. aggregated lymphoid nodules (Peyer’s patches) in the
    small intestine
  • e.g. tonsils: form a ring around the pharynx
    i. pharyngeal (1) - in posterior nasopharynx (referred to
    adenoids when infected/swollen)
    ii. palatine (2) - in oropharynx - used to be commonly
    removed
    iii. lingual (1) - bumpy nodules on posterior part (base) of
    tongue