BIO211 Weekly Guide #5
LYMPHATIC/IMMUNE
SYSTEM
After completing this laboratory you should be able to:
1) Describe the functions, makeup, production, flow, and reabsorption of lymph in the body
2) Localize the major lymphatic collection vessels in the body
3) Identify the five basic types of lymphatic structures and organs in the body in gross anatomy models and histological section.
4) Distinguish between nonspecific and specific pathogen defense and describe the major nonspecific mechanisms
5) Distinguish between cell-mediated and humoral immunity and describe the lymphocyte types involved in eeach
6) Distinguish between active and passive immunity
7) Distinguish between primary and secondary immune responses
7) Describe the basic chemical structure of antibodies and the antigen-antibody interaction
Guide to Gross Anatomy Guide to Histology Guide to Physiology
Outline
I. Lymphatic System [FAP 22-1, 22-2]
A. Constituents - fluid, cells, vessels, aggregations & organs
B. Functions - drainage, lipid transport, immune system, filtration
C. Lymph fluid - plasma w/o the proteins
D. Lymph tissue
fibers - reticular
cells
motile - B & T lymphocytes, macrophages
fixed - reticuloendothelial cells, plasma cells
E. Lymph vessels
lymph capillaries, lacteals, veins, & ducts
lymph "pumps"
lymphatic flow in body
F. Lymphatic drainage
F. Lymphocytes [FAP Fig. 22-6]
T cells
B cells
NK cells
II. Lymphoid Tissue and Organs [FAP 22-2]
A. Lymph nodules (aggregations) - e.g. Peyer's patches, "MALT"
locations - loose C.T. of transitions zones in G.I. and respiratory tracts
structure - reticular cells & fibers, peripheral B lymphocytes, germinal centers
B. Tonsils
three locations
palatine (pair); pharyngopalatine arches - tonsillectomy
lingual (pair); back of tongue
pharyngeal (single); post. wall of nasopharynx - adenoidectomy
function - defense
structure
C.T capsule and septae
lymphatic nodules
crypts
epithelial covering
moist strat. squamous epithelium - palatine and lingual
respiratory epithelium - pharyngeal
C. Thymus
paired lobes
location in body - mediastinum
large at birth, grows until puberty, regresses after puberty
functions
maturation of T-lymphocytes
maturation of spleen & lymph nodes via thymosin
structure
C.T. capsule, trabeculae
cortex & medulla
epithelial reticular cells, Hassal's corpuscles, lymphocytes
circulation: arteries-->capillaries(blood-thymic barrier)-->veins
D. Lymph nodes
spherical or bean shaped
locations - along path of lymph vessels - superficial and deep nodes
function - filter lymph, produce lymphocytes
structure
dense C.T. capsule
cortex - trabeculae, subcapsular sinuses, cortical nodules, germinal centers
medulla - trabeculae, medullary cords, medullary sinuses, reticular cells & fibers,
hilus
circulation:
afferent & efferent lymph vessels
filtration by reticular cells & macrophages
E. Spleen
bean shaped
location in body - in blood stream, not lymphatic stream
functions - blood filter & reservoir, lymphocyte production
structure
dense C.T. capsule, trabeculae
red pulp - reticular tissue, venous sinuses, RBC's
white pulp - reticular tissue, central arteries, lymphocytes
hilus
circulation: splenic artery-->central arterioles-->terminal arterial capillaries-->
intracellular spaces of red pulp-->venous sinuses-->pulp veins-->
splenic vein
III. Immune System Function
A. Immune challenges [FAP 22-1]
pathogen classes
autoimmunity
antigens
B. Nonspecific immunity [FAP 22-3; Fig 22-11]
physical barriers
inflammation [FAP Fig 22-15]
basophils
mast cells
fever (pyrogenic response)
monocytes and macrophages
microphages: neutophils and eosinophils
immunological surveillance, NK cells [FAP Fig 22-12]
interferons [FAP Fig 22-13]
complement system [FAP Fig 22-14]
C. Specific Immunity [FAP 22-4, Fig 22-16, 22-17]
adaptive vs. innate
passive vs. active immunity
naturally-acquired vs. artificially-acquired
cell-mediated vs. humoral immunity
primary vs. secondary response
D. T cells & cell-mediated immunity [FAP 22-5]
role of thymus
MHC and anitigen presentation
T cell types and roles
cytotoxic T cells
helper T cells
suppressor t cells
memory cells
E. B cells and humoral immunity [FAP 22-6]
sensitization and activation
B cell types
plasma cells
memory cells
antibodies
structure
antigen interaction
antibody effects
neutralization
agglutination
complement activation
inflammation
phagocytosis stimulation
F. Abnormal immune responses [FAP 22-7]
hypersensitivity and allergens
stress effects
immunosuppression
immune deficiency and HIV/AIDS
Gross Anatomy List
Lymphatic Structures:
Organs: Vessels:
lymphoid nodules (aggregates) thoracic duct
lymph nodes chyle cisternae
tonsils right lymphatic duct
thymus
spleen
KEY: Know location & function
Guide to Gross Anatomy
The Lymphatic System [APL 21 Exercise 1]
The lymphatic system consists of lymph vessels, lymph nodules and organs, and the lymph itself. The lymphatic vessels do not preserve well and are hard to find in real human bodies.
a) The lymph vessels [APL Fig 21.2] are properly considered a part of the circulatory system, in that they provide for additional fluid return from the body tissues. On the models and charts identify the following major lymph vessels:
cisternae chyli thoracic duct right lymphatic duct
- What regions of the body do the thoracic duct and right lymphatic duct drain? Into what veins does each drain?
- What are the lacteals of the intestinal villi? What is their role in transport of digestive products?
b) On the models and charts locate the lingual, palatine, and pharyngeal tonsils [APL Fig 21.5]. Notice that they ring the entrance to the respiratory and digestive tracts.
c) The thymus [APL Fig 21.2] lies in the superior mediastinum, anterior to the great vessels of the heart. It is prominent in the fetus but regresses and is replaced by connective tissue in the adult. Locate the thymus in the fetal viscera chart.
d) Lymph nodes [APL Fig 21.3] are located along the path of the lymphatic tributary vessels.
- Where are the clusters of lymph nodes in the body?
e) The spleen [APL Fig 21.4] is a lymphatic organ which filters and stores blood, as well as producing lymphocytes.
- Locate the spleen on the models and charts. It lies on the left side between the 9th and 11th ribs and may be palpated under the ribs after a full expiration.
- Why do you suppose that rupture of the spleen often leads to such serious internal bleeding?
Guide to Histology
Lymphatic System [APL 21 Exercise 2]
Lymphatic tissue consists of lymphatic cells supported by a reticular network of fibers and/or cellular processes. It ranges in complexity from simple local aggregations - the nodules, to distinct and structurally complex organs - the lymph nodes and spleen.
Be able to define the following: lymph nodule, lymph node, germinal center, capsule, subcapsular space, trabeculae, peritrabecular space, afferent lymphatic, efferent lymphatic, Hassall bodies, Malpighian corpuscles, red pulp, white pulp, central arterioles, closed circulation, open circulation. You should be able to use the presence or absence of these structures to distinguish the following five types of lymphatic "organs".
a) Lymph Nodules [APL Fig 21.7C]
Lymph nodules are the most structurally simple lymphatic organs. They are aggregates of lymphocytes, suspended in a reticular fiber meshwork, and imbedded within the surrounding connective tissue of other bodily organs. Lymph nodules are found in the lamina propria (part of the inner wall) of the digestive tube. In the ileum (distal small intestine) these aggregations are especially large and are called "Peyer's patches".
- Identify the Peyer's patches in the ileum slide. What is the function of lymph nodules in this location? What are the numerous small, heavily stained cells which make up these aggregations?
- Notice that the cells are most compact at the center of each aggregation. This is a germinal center, a region of cell proliferation and maturation.
- Classify the epithelium that overlies these aggregations.
b) Tonsils [APL Fig 21.7D]
The tonsils are slightly more structurally complex than the lymphatic nodules. The tonsils collectively form a ring around the common entrance to the digestive and respiratory tracts. They may be identified by the overlying epithelium, "hemicapsule", and deep crypts.
- What kind of epithelium overlies the lingual and palatine tonsils? What kind of epithelium overlies the pharyngeal tonsil? Which does the demonstraton slide
c) Thymus
The main functions of the thymus are the production of T-lymphocytes and the production of the hormone thymosin, which stimulates lymphatic tissue. The thymus may be identified by the C.T. capsule which completely surrounds it and by the dense, involuted Hassall bodies.
- Contrast the appearance of the thymus in the human infant and adult.
d) Lymph Node [APL Fig 21.7B]
Review the structure of a lymph node. Lymph nodes may be identified by the prominent C.T. capsule and trabeculae, together with the subcapsular and peritrabecular spaces.
- Identify the germinal centers, capsule, trabeculae, subcapsular and peritrabecular spaces, cortex, and medulla. What are the structural differences between lymph nodes and lymph nodules? What additional function(s) do lymph nodes perform?
- What is the significance of the large lymphocytes in the germinal centers.
- How does lymph enter and leave the node? How does blood enter and leave the node?
e) Spleen [APL Fig 21.7A]
The spleen is the largest and most structurally complex lymphatic organ. Review its structure. Compare this structure to that of the lymph nodes. The spleen may be identified by the presence of red pulp and the central arterioles of the white pulp.
- What are the functions of the spleen? How do these differ from those of the lymph nodes?
- What cell type(s) predominate in the red pulp? In the white pulp?
f) Lymph Vessels
Due to their extremely thin walls, lymphatic vessels are extremely difficult to unambiguously identify in histological preparations.
- What propels lymph through these vessels? What prevents backflow?
Guide to Physiology
There are no structured immune system physiology component to this lab. APL 21 Exercise 3 may be useful for synthesizing and reviewing immunological responses.