What are the three functions of the lymphatic system?
draining interstitial fluid, transporting dietary lipids, protection
Describe the structure of a lymphatic capillary. How does it work?
- made of a single layer of squamous epithelial cells
- slightly larger than blood vessels
- cells overlap and act as one-way valves
- opened by pressure of interstitial fluid
- anchoring filaments attach cells to surrounding tissue
Where would we find lymphatic capillaries and where are they absent in the body?
- found in tissue spaces between cells
- absent from the central nervous system, bone marrow, teeth, avascular tissues, splenic pulp
What is lymph? Is it a circulating fluid?
- interstitial fluid and leaked plasma proteins drain into lymphatic capillaries
- NOT a circulating fluid
Trace the flow of lymph from the lymphatic capillaries to the collecting ducts.
lymphatic capillary, lymphatic vessel, lymph node, lymphatic vessel, lymphatic trunk, collecting duct
What are the two major lymphatic ducts, and what areas of the body do they drain?
THORACIC DUCT - 3/4 of the body
RIGHT LYMPHATIC DUCT - drains right arm, and right side of head, neck and upper torso
Where do the two major lymphatic ducts empty into the circulatory system?
both empty into subclavian veins at junction with internal jugular vein
Where would you find the cisterna chyli?
lower end of the thoracic duct (in most mammals) into which lymph from the intestinal trunk and two lumbar lymphatic trunks flow
What are the organs of the lymphatic system?
PRIMARY ORGANS - red bone marrow, thymus gland
SECONDARY ORGANS - lymph nodes, lymph nodules, spleen
Describe the structure and function of a lymph node.
- vary in shape and size but most bean shaped
- external fibrous CAPSULE
- TRABECULAE extend inward and divide node into compartments
- two histologically distinct regions: Cortex, Medulla
# FUNCTION #
- provide biological filtration
- immune system activation—lymphocytes activated and mount attack against antigens
- site of cancer growth and metastasis
What is the medical name for a swollen lymph node?
buboes (singular: bubo)
What does albumin do for the blood?
regulates osmotic pressure
What happens when the flow of lymph is blocked?
lymphedema, which means swelling due to a blockage of the lymph passages
What are lacteals and what do they do?
- specialized lymphatic capillaries in vili of small intestine
- transport lipids
What are lymph nodules?
small, localized collection of lymphoid tissue, usually located in the loose connective tissue beneath wet epithelial (covering or lining) membranes, as in the digestive system, respiratory system, and urinary bladder
What is MALT?
mucosa associated lymphoid tissue
What are Peyer’s patches?
- small masses of lymphatic tissue found throughout the ileum region of the small intestine
- form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines
What are tonsils?
lymphoid tissue under the mucous membranes of the throat
Name the three major tonsils.
- (1) the pharyngeal tonsils, commonly known as adenoids
- (2) the palatine tonsils and (3) the lingual tonsils, which are lymphatic tissue on the surface tissue of the base of the tongue
What does the thymus do?
- does not directly fight antigens
- functions strictly in T lymphocyte maturation (keeps isolated via blood thymus barrier)
Where is the thymus?
inferior neck; extends into mediastinum; partially overlies heart
When is the thymus largest? Then what happens to it?
grows in size and most active during childhood, then stops growing during adolescence and then gradually atrophes
Locate the spleen. What is white pulp? Red pulp?
- upper left quadrant of abdomen
- WHITE PULP: little islands, mostly B cells
- RED PULP: connective tissue (the cords of Billroth) and many splenic sinusoids that are engorged with blood (red color) primary function - is to filter the blood of antigens, microorganisms, and defective or worn-out red blood cells
What are the three functions of the spleen?
- site of lymphocyte proliferation and immune surveillance and response
- cleanses blood of aged cells and platelets, macrophages remove debris
- stores breakdown products of RBCs for later use and stores blood platelets and monocytes