Cells And Tissues Of The Lymphatic System Flashcards
What makes up the lymphatic system ?
- lymphatic tissues organs
- lymphatic vessels
- lymph
- cells contained within the lymphoid tissues and organs
What is lymph
- a thin fluid that resembles plasma
- has a pH of 7.4
- but with lower amounts of protein
What is chyle
- lymph that arises in the GI tract
- it is a white , cloudy substance
- contains fats and dissolved lipids
- ie chylomicrons
- fat soluble vitamins
What are the 4 fat soluble vitamins ?
- A
D
E
K
What are two similarities between a vein and lymphatic capillary?
- low pressure system
- valves present
What is a difference between lymphatic capillary and vein ?
- lymphatic capillary contains no cells inside whereas veins do.
Where are the main lymph nodes found ?
- neck ( cervical);
- groin ( inguinal)
- armpit ( axillae)
Describe the structure of a lymph node
- shaped like a kidney bean
- has multiple afferent lymphatic vessels that enter via convex surface
- a SINGLE efferent lymphatic vessel that leaves via the concave hilum.
- each lymph node has a feeding artery and draining vein that leave and enter via the hilum.
- lymphoid follicles that contain immune cells such as dendritic , t, B, and macrophages
-
Where are the lymphoid follicles found in the lymph node?
In the cortex region
Is the hilum surrounded by the cortex ?
No
What is the centre of the lymphoid follicle called ?
Germinal, centre
What is the main connective tissue fibre found in the lymph node ?
Recticulin ( collagen 111)
- made by reticular cells which are special types of fibroblasts found in the lymphatic system.
Which lymphocytes recognise antigens and which need to be presented to an antigen ?
B cells Can recognise antigens
- T cells need to be presented to antigens
How many lymph nodes are found in the lymphatic system ?
600-700
What is the cause of lymphadenopathy ( enlarged lymph nodes )
- the germinal centres fill with increasing numbers of lymphocytes causing the lymph nodes to swell too much.
- can cause considerable amount of pain
What is a difference between lymphoma and leukaemia?
- lymphoma refers to cancer that arises from lymphatic tissue itself (malignancy of the lymphoid tissue itself) whereas leukaemia is cancer where the malignant lymphoid tissue appears in the blood but arises from the bone marrow.
What are the two types of lymphoma?
Hodgkin and non-Hodgkin
What is the difference between Hodgkin and non-hodgkin lymphoma ?
- Hodgkin lymphoma is characterised by the presence of a Reed-Sternberg cell visible under microscope whereas non-Hodgkin lymphoma is a cancer characterised by increased proliferation of B or T cells- occurs in old aged people.
List all 5 lymphatic organs
- thymus
- appendix
- tonsils
- spleen
- payers patches
-
Where is the location of the thymus
Superior mediastinum ( space between both lungs )
How does the size of the thymus change throughout ones life ?
- the thymus increases in size from birth then to puberty.
- after puberty it regresses ( atrophy) and is replaced by fat.
- the loss of the thymus completely ( around age 65) will result in inability to produce T cells - become more susceptible to infection.
What does the structure of the thymus resemble ?
- lymph nodes , but no hilum.
The capsule and septa are made up of what connective tissue ( eg in lymph nodes , thymus)
Recticular fibres ( collagen 3) and recticulin
What is the function of the thymus
-T cells mature from thymocytes( which are immature T cells in the thymus) that proliferate in the cortex before they enter the medulla region to interact with the epithelial cells.
What is the largest lymphoid organ during neonatal and pre adolescent periods ?
Thymus
What makes the red blood cells during the pre natal period ?
Spleen and liver
Where is the spleen located ?
Inferior to diaphragm
- posterior to stomach
What does the structure of the spleen resemble ?
- lymph node but it has two sections the white pulp and the red pulp
What is the function of the red pulp ?
- removal and destruction of old , damaged red blood cells and platelets
- retrieval if iron from red blood cells haemoglobin
- stores RBC
What is the function of the white pulp
Antigen presentation by antigen presenting cells
- activation and proliferation of B and T lymphocytes , production of antibodies
What is splenectomy?
Removal of the spleen , this is where the red blood cells and the bone marrow have to take over the the removal and destruction of red blood cells
What does splenectomy increase the risk of !
Infection by encapcsulated bacteria because they are able to detect it very well. For example , malaria
What is splenomegaly?
Spleen enlarged to upton10x normal size because of localised infection or systemic infection ( eg malaria , glandular fever , sepsis )
What are the 4 types of tonsils ?
1) adenoids tonsils
2) two tubal tonsils
3) lingual tonsils
4) two palatine tonsils ( common ones we talk about )
Where is the location of the tonsils ?
Oropharynx (throat ) and nasopharynx( upper part of the pharynx).
Are tonsils fully formed at birth ?
Yes
Is the spleen fully formed and functional at birth ?
Yes
Is the thymus fully formed and functional at birth ?
Yes
What is the function of tonsils ?
- prevents pathogen ingress through oral , nasal and aural route ( ears)
- crypts increase surface area
Where is the vermiform appendix found ?
At the junction of the small and large intestines.
- inferior to and attached to the caecum.
What type of cells does the appendix have many of ?
Microfold cells in the epithelial surface
Where are the payers patches found ?
They are found inferior to and attached to the ileum ( last part of the small intestine )
- many microfold cells
What is the function of the payers patches ?
Prevents pathogen ingress through digestion
What are the 4 functions of the lymphatic system ?
1) fluid balance - most of the interstitial fluid is returned to the circulation by this route
2) transport of fats and fat soluble vitamins ( A ,d, E,K)
3) defence against invading pathogens or disease
4) storage of and destruction of aged RBC
What is a sentinel lymph node ?
First lymph node that swell due to cancer cells in metastatic disease
- for example axilla or pectoral in breast cancer can be detected using flurography
- if malignant epithelial cells are present - mastecotomy needs to be done ( surgical removal of breasts)
What is lyphedema?
When the lymph vessels are unable to drain excess lymph fluid usually from the arm or leg. It can either be primary lyphedema or secondary lymphedema
What are the possible causes of primary lymphodema ?
- hypoplasia ( not many lymph nodes )
- hyperplasia
- congenital ( onset within 2 years , mutated FLT4 gene , small or missing endothelial cells in vessel wall)
What are possible causes of secondary lymphodema ?
- radiotherapy
- autoimmune disease
- infections
- surgery
How does lymph travel across the body ?
- capillaries drain intersitisl fluid pto make tissue fluid , not all fluid re enters the capillaries , some would enter the lymphatic capillary.
- lymph then enters lymphatic vessel then lymphatic node then lympthatic , trunk then lymphatic duct.
Z- then goes back to veins
Why are lymphatic capillaries blind ended ?
- circulation of lymph begins with the capillaries being blind ended ( intertestial fluid can pass into them but not out of them)
- they are highly permeable , formed by endothelial cells with button like junctions between them which allow fluid to pass through them when the interstitial fluid pressure is high enough .
Lymph from the right upper side of the body and the head drains into which major vessel
- right subclavian vein which is located below the cavical bones .
What is the cisterna chyli?
A dilated collecting sac -located in the lower abdomen.
- drains lymphatic trunks of the lower part of the body.
