Lymphatic system Flashcards
Name the components of the lymphatic system
Red bone marrow
Lymphatic vessels
Lymph nodes
Lymph tissues
What are the main functions of the lymphatic system?
To drain interstitial fluid
To transport dietary molecules and lipid soluble vitamins (A,D,E,K)
Facilitation of immune system
carry pathogens to lymph nodes
return leaked proteins to the blood
What are the 4 types of pressure involved in the lymphatic system?
Hydrostatic pressure
Interstitial osmotic pressure
interstitial fluid pressure
colloidial osmotic pressure
Define hydrostatic pressure
It is the pushing force exerted by a fluid at arterial through venous ends, It is the pressure exerted by the blood against the vessels
(30-10mmHg)
Define Interstitial Osmotic pressure
is the pressure created when a small number of proteins link from capillaries into extracellular space around 8mmHg
Define Colloidal osmotic pressure
Is the force created by the exertion of plasma proteins that are too large to fit through capillaries e.g., albumin
(28mmHg in capillaries)
Define Interstitial fluid pressure
Contributes to the outward pull of the capillaries, is slightly negative (-3mmHg)
It is the hydrostatic pressure in the interstitial fluid
Describe the formation of the lymph
- Blood has high hydrostatic pressure which pushes plasma out of capillaries into surrounding tissue forming interstitial fluid
- albumin a plasma protein is too large to leave capillaries, so exerts osmotic pressure inside capillaries
- this osmotic pressure pulls interstitial fluid into capillaries
- not all interstitial fluid re-enter capillaries, 10% forms lymph & drained into lymphatic system
- lymph needs to be drained to prevent oedemas
- lymph capillaries contain a lower pressure than interstitial fluid, fluid enters lymph capillaries via mini valves, once fluid enters it is known as lymph
Describe the draining of the lymph
Lymph capillaries join to form lymph vessels, lymph flows in 1 direction (valves)
The lymph drains into 1 of 2 ducts (left/right)
Lymph is returned to the blood
In small instestine (ileum), lymph capillaries are called lacteals which join to form vessels. They carry chyle (fatty lymph) which drain into a cisternae (sac) chyli.
Acts as a channel for lipid products from digestions
Describe how the lymph is returned to the blood
upper right duct drains the upper right side of the body and returns the lymph via right subclavian vein in chest
upper left duct drains the left side of the upper body, returns the lymph through left subclavian vein
Describe the relationship between the cardiovascular & lymphatic system
These systems are both part of the circulatory system. Both are involved in waste removal and transportation of fluid around the body.
Work together to keep a balance of nutrient dispersal and waste removal.
Lymph is returned to cardiovascular system
What is an oedema and what factors induce an oedema
An oedema is a build up of fluid, occurs where there is an increase in intersitial fluid. (from 2.5 to 3L)
Factors:
- increased capillary permeability
- obstruction to the lymph
- increased capillary filtration pressure,
- decreased capillary colloidal pressure
What are lymph nodes and describe their structure
A lymph node is a bean-shaped structure found over the body. They receive lymph from afferent vessels
The lymph nodes are then drained by an efferent vessels. Lymph nodes filter the lymph
Structure:
- are surrounded by capsules
- contain trabeculae to make compartments
- Each compartment has reticular cells
- reticular cells are involved in phagocytosis, engulf & digest pathogens
- lymphocytes found between reticular cells, they produce antibodies
What is a melanoma
A melanoma is a form of skin cancer. When a melanoma cells form they often spread to a nearby lymph node.
A stage 3 melanoma is where cancer cells have spread to a lymph node
What is the peyer’s patch
A small cluster of lymphatic cells found in the ileum (small intestine)
They analyze and respond to gut microbes
Peyer’s patch contains T & B cells to respond to molecules, act as a line of defense against harmful/ inflammatory dietary agents & harmful microbes
Describe the role of tonsils and their location in the lymphatic system
There are 5 tonsils
- 2 palatine tonsils found in the oral cavity
- 2 linguae tonsils found at the base of the tongue
- 1 Pharyngeal tonsil found at posterior wall of nasopharynx
Tonsils are used to filter air, they filter germs & pathogens to protect the body from infection. They contain a lot of WBC
Describe the role of the thymus gland in the lymphatic system
Located in the mediastinum, surrounded by a connective tissue capsule containing inward projecting trabeculae.
The thymus produces thymulin, which sets up the production of T-cells & stimulates the maturation of T-cells
Largest in childhood, during adulthood thymus decreases in size
Describe the role of the spleen in the lymphatic system
The spleen is involved in the breakdown
& removal of RBC + plaetelets. Located on the left hand side below the diaphragm, contains reticular cells, red pulp which filters blood, stores WBC, removes old defective RBC
Also contains white pulp which is involved in the immune response
Order of capillaries
- Lymphatic capillaries
- collecting lymphatic vessels
- lymphatic trunks
- lymphatic ducts
Define function of lymphatic trunk
Collecting lymphatic vessels form together into the lymphatic trunk which drain large areas of the body. Named after the region they are found in e.g., subclavanian
Define the function of the Thoracic duct
Drains the rest of the body, it collects lymph from lumbar trunks (lower limb), intestinal trunk
Describe the transport of lymph in the lymphatic system
The lymphatic system lacks a pump, so lymph flows slowly & at low pressure through capillaries
Skeletal muscle, and breathing mechanism aid in the flow of lymph & prevent backflow
During physical activity lymph flows rapidly
Function of dendritic cells
Capture antigen and return them to lymph nodes
Function of reticular cells
The produce reticular fibre stroma which is a network that supports other cells types in lymph tissue
Describe the importance of lymphatic tissue
It houses lymphocytes and provides a site where they can multiply and become active. It also provides a good lookout point for macrophages & lymphocytes
Name the 2 types of lymphatic tissue
Diffuse lymphoid tissue
Lymphoid follicles (nodules)
Describe the structure &function of diffuse tissue
a loose arrangement of lymphoid cells & some reticular fibres,
Found in most organs
Large amounts found in the digestive tract
Describe the structure &function of lymphoid follicles
consists of tightly packed lymphoid cells & reticular fibres
They have germinal centres where B cells can be found
These centres enlarge when B cells divide to produce plasma cells
Found in the peyer’s patch & appendix
Describe the structure &function of the primary lymphoid organ
This is where B & T cells mature, in the red bone marrow & thymus.
Describe the structure &function of the secondary lymphoid organ
Where mature lymphocytes first encounter their antigens and become activated
Includes spleen, peyer’s patch, MALT, lymph nodes ETC
What are the role of lymph nodes?
- To cleanse the lymph by containing macrophages which destroy microorganisms that enter lymph from connective tissue, preventing them from being delivered to the blood & spreading elsewhere
- immune activation: lymph nodes & lymph organs are strategically located in areas where antigens are commonly found so they can be activated and attack them
Many antigens brought by dendritic cells to lymph nodes. This causes the activation of T cells
