lymphatic system Flashcards
list the 3 components of the lymphatic system
- lymph
- lymphatic vessels
- lymphoid tissues and organs
list some circulatory and immune functions of the the lymphatic system
- returns fluids that have leaked from the vascular system back to the blood
- transports nutrients, hormones and wastes
- protects the body by removing foreign material from lymph streams
- provides site for immune surveillance
what do lymphatic vessels do?
lymphatic vessels (lymphatics) form an network of drainage vessels that collect excess interstitial fluid and return it to the bloodstream. This is a one way system in which lymph flows toward the heart.
what is lymph?
the interstitial fluid that has entered the lymphatics
what are lymphatic capillaries and list their 2 structural modifications
lymphatic capillaries drain the interstitial space of most tissues.
- endothelial cells overlap forming easily opened, flap-like minivalves
- collagen filaments anchor the endothelial cells to surrounding structures so that an increase in interstitial fluid volume opens the minivalves
what is a lacteal?
a lacteal is a highly specialised lymphatic capillary present in the villi of intestinal mucosa.
lacteals absorb digested fats from the intestine.
fatty lymph is called ‘chyme’
describe the flow of lymph
lymphatic capillaries-collecting vessels-trunks-ducts-toward heart
list the major trunks (hint there are 9)
2 jugular trunks 2 subclavian trunks 2 bronchomediastinal trunks 2 lumbar trunks 1 intestinal trunk
the first 4 drain into the thoracic duct or right lymphatic duct.
the 2 lumbar trunks and intestinal trunk drain into the cysterna chyli
superficial lymph vessels follow…
veins
deep lymph vessels follow…
arteries
list the 2 lymphatic ducts and state their drainage point
- Right Lymphatic Duct
- Thoracic Duct
these ducts empty into the blood vascular system at the junction of the internal jugular and subclavian veins in the neck (on their own side)
list 4 factors affecting lymphatic flow
- skeletal muscle contraction
- pressure changes in thorax
- contractions of lymphatic vessels
- valves (prevent backflow)
3 lymphatic cell types
- lymphocytes- T, B, Natural Killer
- auxillary immune cells-macrophages, dendritic cells
- supporting cells-reticular cells that form CT stroma
2 functions of lymphoid tissue
- proliferation site for lymphocytes
2. surveillance for lymphocytes and macrophages
2 types of lymphoid tissue
- diffuse lymphoid tissue-loose (most common)
2. lymphoid follicles-dens;germinal centres of proliferating B lymphocytes
list functions of lymph nodes
- house lymphocytes and macrophages
- activate immune system
- filter lymph
describe the flow of lymph through a lymph node
lymph enters the lymph node through afferent vessels, and exits via efferent vessels.
there are few efferent vessels than there are afferent vessels, which allows time for cleansing of lymph.
Lymph flows into the node through afferent lymphatic vessels (convex surface)
Moves through subscapular sinus towards medulla
Flows through medullary sinuses
Exits via afferent lymph vessels located at the Hilum (concave surface)
list some other lymphoid organs a part from lymph nodes
spleen, thymus, tonsils and Peyer’s Patches of intestinal wall
embryologically, what do lymphatics develop as?
outpockets of developing veins
embryologically, lymphoid organs develop from?
haematopoietic tissue
5 functions of spleen
- immunity
- blood filter
- reservoir
- recycles
- erythropoesis in the foetus
the spleen provides a site for lymphocytic proliferation and immune function, and destroys aged or defective RBCs and blood borne pathogens. it also stores and releases the breakdown products of haemoglobin, stores platelets and acts as a hematopoetic site for the fetus.
differentiate primary lymphoid organs from secondary lymphoid organs
primary:
-site of B and T cell maturation
-red bone marrow, thymus
secondary:
-mature lymphocytes first encounter antigens and become activated
-lymph nodes, spleen, appendix, tonsils, Peyer’s Patches (intestinal follicles)
The capsule of the spleen contains smooth muscle fibres. In which situations would this organ need to contract?
When it needs to release blood, platelets and monocytes, e.g. severe bleeding, fight infection
this is initiated by the sympathetic nervous system
Define the following terms:
a) Microbiome
b) Microbiota
c) Commensal
d) Probiotic
e) Pathogen
f) Dysbiosis
a) Microbiome-collection of microbial genomes
b) Microbiota-collection of microbes
c) Commensal-a colonising organism that is neither beneficial nor harmful
d) Probiotic-an organism that elicits health benefits to the host
e) Pathogen-an organism that is detrimental to the host or causes disease
f) Dysbiosis-loss of balance within the microbial community
Explain how dysbiosis can potentially lead to disease
a) microbiome diversity increases at sites which normally have restricted diversity
b) reduced diversity at sites which normally have great diversity
Provide examples of conditions that have been associated with (i) the GIT microbiome and (ii) the vaginal/urethral microbiome
GIT microbiome associated conditions Dental caries Peptic ulceration, oesophageal and gastric carcinoma Obesity IBD IBS
Vaginal/urethral microbiome associated conditions
Bacterial vaginosis
Recurrent UTIs
Susceptibility to infection during pregnancy
Pre-term birth
