Exam II Anatomy 2 Flashcards
lymphatic systm
Consists of two semi-independent parts
A network of lymphatic vessels
Lymphoid tissues and organs scattered throughout the body
Returns interstitial fluid and leaked plasma proteins back to the blood
lymph
interstitial fluid once it has entered lymphatic vessels
functions of lymph system
Draining excess interstitial fluid & plasma proteins from tissue spaces
Transporting dietary lipids & vitamins from GI tract to the blood
Facilitating immune responses
recognize microbes or abnormal cells & responding by killing them directly or secreting antibodies that cause their destruction
lymph vessels
A one-way system in which lymph flows toward the heart
Lymph vessels include:
Microscopic, permeable, capillaries
Lymphatic collecting vessels
Trunks and ducts
lymph capillaries
Similar to blood capillaries, with modifications
Very permeable
Loosely joined endothelial minivalves
The minivalves function as one-way gates that:
Allow interstitial fluid to enter lymph capillaries
Do not allow lymph to escape from the capillaries
Withstand interstitial pressure and remain open
lymphocytes
T cells
Manage the immune response
Attack and destroy foreign cells
B cells
Produce plasma cells, which secrete antibodies
Antibodies immobilize antigens
Other Lymphoid Cells
Macrophages – phagocytize foreign substances and help activate T cells
Dendritic cells – spiny-looking cells with functions similar to macrophages
Reticular cells – fibroblastlike cells that produce a stroma, or network, that supports other cell types in lymphoid organs
lymphoid tissue
Diffuse lymphatic tissue
Lymphatic follicles (nodules)
Lymph nodes
lymphoid tissue function
- Diffuse lymphatic tissue – scattered reticular tissue elements in every body organ (not enclosed by a capsule)
Larger collections appear in the lamina propria of mucous membranes and lymphoid organs.
found outside of lymphatic system organs
- Lymphatic follicles (nodules) – solid, spherical bodies consisting of tightly packed reticular elements and cells
Have a germinal center composed of dendritic and B cells
Found as part of larger lymphoid organs (lymph nodes) or embedded within non-lymphoid organs like Peyer’s Patches
lymph nodes
Lymph nodes are the principal lymphoid organs of the body
Nodes are imbedded in connective tissue and clustered along lymphatic vessels
Aggregations of these nodes occur near the body surface in inguinal, axillary, and cervical regions of the body
lymph node function
Their two basic functions are:
Filtration – macrophages destroy microorganisms and debris
Immune system activation – monitor for antigens and mount an attack against them
lymph node structure
Nodes are bean-shaped and surrounded by a fibrous capsule
Trabeculae extended inward from the capsule and divide the node into compartments
Nodes have two histologically distinct regions: a cortex and a medulla
The cortex contains follicles with germinal centers, heavy with dividing B cells
Dendritic cells encapsulate the follicles
The deep cortex houses T cells in transit
T cells circulate continuously among the blood, lymph nodes, and lymphatic stream
Medullary cords extend from the cortex and contain B cells, T cells, and plasma cells
Macrophages sit in these cords and phagocytize foreign matter
circulation in lymph nodes
Lymph enters via a number of afferent lymphatic vessels
It meanders through sinuses and exits the node at the hilus via efferent vessels
Because there are fewer efferent vessels, lymph stagnates somewhat in the node
This allows lymphocytes and macrophages time to carry out their protective functions
other lymphoid organs
The spleen, thymus gland, and tonsils
Peyer’s patches and bits of lymphatic tissue scattered in connective tissue
All are composed of reticular connective tissue and all help protect the body
Only lymph nodes filter lymph
spleen
Largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm
It is served by the splenic artery and vein, which enter and exit at the hilus
function of the spleen
Site of lymphocyte proliferation
Immune surveillance and response
Cleanses the blood by removing old RBC
Stores blood platelets
structure of the spleen
Surrounded by a fibrous capsule, it has trabeculae that extend inward
Two distinct areas of the spleen are:
White pulp – area containing mostly lymphocytes suspended on reticular fibers and involved in immune functions
Red pulp – remaining splenic tissue concerned with disposing of worn-out RBCs and bloodborne pathogens
thymus
A bilobed organ that secrets hormones (thymosin and thymopoietin) that cause T lymphocytes to become immunocompetent
The size of the thymus varies with age
It increases in size and is most active during childhood
It stops growing during adolescence and then gradually atrophies
internal anatomy of the thymus
Thymic lobes contain an outer cortex and inner medulla
The cortex contains densely packed lymphocytes and scattered macrophages
The medulla contains fewer lymphocytes and thymic (Hassall’s) corpuscles
thymus
The thymus differs from other lymphoid organs in important ways
It functions strictly in T lymphocyte maturation
It does not directly fight antigens
Star-shaped thymocytes secrete the hormones that stimulate lymphocytes to become immunocompetent
tonsils
Simplest lymphoid organs; form a ring of lymphatic tissue around the pharynx
Location of the tonsils
Palatine tonsils – either side of the posterior end of the oral cavity
Lingual tonsils – lie at the base of the tongue
Pharyngeal tonsil – posterior wall of the nasopharynx (A.K.A. Adenoids)
Lymphoid tissue of tonsils contains follicles with germinal centers
Epithelial tissue overlying tonsil masses invaginates, forming blind-ended crypts
Crypts trap and destroy bacteria and particulate matter
peyer’s patches
Isolated clusters of lymphoid tissue, similar to tonsils
Found in the wall of the distal portion of the small intestine
Similar structures are found in the appendix
Peyer’s patches and the appendix:
Destroy bacteria, preventing them from breaching the intestinal wall
Generate “memory” lymphocytes for long-term immunity
malt
Mucosa-Associated Lymphatic Tissue is composed of:
Peyer’s patches, tonsils, and the appendix (digestive tract)
Lymphoid nodules in the walls of the bronchi (respiratory tract)
MALT protects the digestive and respiratory systems from foreign matter
immunity
resistance to disease
what are the two intrinsic systems of the immune system?
Innate (nonspecific) defense system
First - external body membranes (skin and mucosae)
Second - antimicrobial proteins, phagocytes, and other cells
Inhibit spread of invaders
Inflammation most important mechanism
Adaptive (specific) defense system
Third line of defense attacks specific foreign substances
Takes longer to react than innate system
innate defenses
surface barriers
chemical barries
respiratory system modification
What are surface barriers,
chemical barriers, and
respiratory system modification
Surface/Physical barriers ward off invading pathogens
Skin, mucous membranes, and their secretions
Chemical barriers inhibit or destroy microorganisms
Acids of skin and stomach
Enzymes – lysozymes – kill microorganisms
Defensins – antimicrobial peptides – inhibit growth
Respiratory system modifications
Nose hair coated in mucous
Cilia sweep pathogens out of trachea
