Lymphatic System Flashcards
Lymph
Tissue fluid formed at the post-capillary venule, percolates through cells taking up wastes, and is collected by the lymphatic system
Functions of the lymphatic system
Fluid recovery
Lipid absorption
Immunity
What are lymphatic capillaries?
Begin closed-ended in tissue spaces between cells
Unique one-way structure permits interstitial flow into but not out of the vessels
- Lymph vessels have valves like veins to prevent backflow
What are lacteals?
Blind-ended lymphatic capillaries found in the center of the villi of the small intestine
- specialized for the absorption of chylomicrons (lipids) that are eventually dumped into venous system with the rest of the lymph
- openings allows for the diffusion of fluid and lipids into the lacteal
What are the function of lymph nodes?
Help to recover fluid
Flow of lymph back to the heart: 1-6
- Interstitial spaces - lymphatic capillaries
- Lymphatic vessels
- Lymph nodes
- Lymph trunks
- Collecting ducts
- Subclavian vein
What is a thoracic duct?
Main duct that begins as cisterna chyli dilation in abdomen
- also receives lymph from left head, neck, and chest
What is the right lymphatic duct?
Receives lymph from the right head, neck, and chest
The thoracic and right lymphatic ducts drain into the junction of the …
internal jugular vein and subclavian veins
Elephantiasis - Lymphatic Filariasis
Mosquito-born round worm called filariae
- swelling upstream of the blockage
- skin becomes thickened and cracked
Immunity
The defense capability of the body against pathogens
Pseudopods
Extensions that grab foreign materials and pull them in
Antigen
A molecule that provokes and immune response
Non-specific immunity
Mechanical barriers
phagocytosis
inflammation/fever
Specific immunity
Built over time
Humoral (antibody mediated)
Cell-mediated (t-cells)
Natural Killer cells
Immunological surveillance
T lymphocytes (T-cells) - 3 types
3 types:
Cytotoxic - directly attach and kill other cells
Helper - activate defense mechanisms
Memory - provide long lasting memory of an antigen
B lymphocytes
Differentiate into plasma cells (secrete antibodies)
- Some become memory B cells (long-lasting immunity)
Antigen presenting cell
What would be the effect of a virus that selectively destroyed memory T and B cells?
Prevents from keeping memory of that virus
Macrophages
Develop from monocytes
- phagocyte cells - get rid of tissue and debris
- display foreign fragments to cytotoxic and helper T cells
Antigen presenting cells
Dendritic cells
Branched macrophages
Reticular cels
Found in the thymus
Contribute to stroma of lymphatic organs
Antigen presenting cells
Primary lymphatic organs and tissues
Site of stem cell division and development of immunocompetent B and T lymphocytes
- Includes red bone marrow and the thymus
Secondary lymphatic organs and tissues
Site of most immune responses
- Includes lymph nodes, spleen, and lymphatic follicles
Lymphatic nodule
Structural and functional unit of lymphatic tissue
- not enclosed in a CT capsule
- 1st line of immunological defense
Function of lymphatic nodule
Identify sites where B-lymphocytes in loose areolar CT have encountered antigens
- germinal center is surrounded by corona, where activated B-cells enlarge and divide into plasma cells
Location of lymphatic nodules
Tonsils
Peyer’s patches
Appendix
Lingual Tonsils
Posterior aspect of tongue
Palatine tonsils
Between anterior and posterior pillars
Pharyngeal tonsils (Adenoids)
Posterior wall of nasopharynx
Waldeyer’s Ring
Aggregations of lymphatic tissue in the oro- and nasopharynx that form a ring around the opening of the digestive and respiratory tracts
Red Bone Marrow
In flat bones and epididymis of long bones in adults
- stem cells produce both B and T lymphocytes
- Where B cells mature
Thymus function
Where immature T cells migrate and multiply to mature
- Thymosin is produced here by the reticuloendothelial cells
- Found in the anterior mediastinum next to the heart
Thymus structure
Made of 2 lobes, each has a different cortex and medulla
- Has efferent ductules but no afferent ductules
- Replaced by fat after puberty
Lymph node 2 main regions and their functions
Cortex - Outer area composed of lymphoid nodules (B-cells)
Medulla - Inner area composed of lymphoid sinusoids
How do lymph nodes work?
They filter foreign substances
- Reticular fibers trap and lymph flows through
- Macrophages destroy through phagocytosis
- Lymphocytes destroy through immune responses
How does lymph travel through the lymph node?
Lymph enters in through the afferent vessels into the subcapsular sinuses
- its then contacted by B-cells in the cortex and T-cells in the T-cell dependent zone (between the cortex and medulla)
- Then it exits through the efferent vessels
Histology of the lymph node
Reticular connective tissue
Why are superficial lymph nodes important?
They are scattered throughout the body and are easily palpable
- swelling of these can indicate infection
- Important ones: cervical, axillary, inguinal
Significance of the umbilicus and lymph nodes
The umbilicus is a watershed area for the lymph collected by the superficial nodes
Spleen Characteristics
Largest mass of lymphatic tissues
Contains Red and white pulp
Lymphatic follicles
Concentrations of lymphatic tissue without capsule
- mucosa-associated lymphatic tissue scattered throughout
- also has large aggregations (appendix and tonsils)
Spleen location
Located in the abdomen, posterior-lateral to stomach
White pulp in the spleen
Made of white blood cells
- produces antibodies
- lymphatic tissue
- B-cells differentiate into plasma cells
Red Pulp in the spleen
Made of red blood cells
- destroys old RBC and platelets
- contains macrophages
