The lymphatic system collects and cleanses the fluid which seeps out of the capillary beds, bathing the tissue which it perfuses. This cleansing fluid, called lymph, is collected by afferent lymph vessels which carry it to a lymph node where it is filtered. There, macrophages consume bacteria and debris, and immune cells monitor it for antigens against which antibodies might be made. The cleansed lymph leaves via an efferent lymph vessel and for most of the body, is collected into the thoracic duct which empties into the circulatory system through the L subclavian vein. (The upper right quadrant drains into the R subclavian vein.)
[Gilbert has no relevant illustrations.]
ANATOMY: Illustrate the highlighted features of the lymphatic system in the cat:
Examine the relationship of the mesenteries to the small intestine in the dissected cat. Note that the lymphatic drainage pattern (marked by injected yellow latex) follows the same route as the arterial supply. Small afferent lymph vessels lead to lymph nodes. The efferent vessels join to form successively larger vessels which empty into the large-diametered cisterna chyli, embedded in the mesenteries near the rear abdominal wall (it may appear brown until you remove the adventitia. Follow the cisterna chyli up. When it passes through the diaphragm, it becomes the thoracic duct. In the thorax, may be seen as a thin brown tube in the thorax to the left of the aorta under the intercostal arteries. Trace it up til it passes behind the left subclavian vein into which it empties (next to the jugular vein). Note also these lymph nodes: the submandibular and the numerous lymph nodes associated with the ileocecal junction.
HISTOLOGY OF A LYMPH NODE:
Examine the following slide and illustrate, labeling the specified features. Note the function of each feature. It is specially stained with silver and gold to show reticular fibers. The plate numbers are in the 9th Ed. of di Fiore's Atlas of Normal Histology:
Slide 3. Lymph node, Reticular tissue, (H 550) VE: p. 125 & 127, 40x:
capsule
subcapsular sinus (contains the lymph within the node)
cortex:
trabeculae form baffles which direct lymph over the germinal centers
germinal centers house immune cells, enlarge during infections
medulla:
medullary sinus chamber(s) in the center, collects filtered lymph
reticular fibers give structure to the gland, anchor macrophages,
(best seen at 400x)