L17: The lymphatic system Flashcards
(34 cards)
What is the lymphatic system?
Network of tissue and organs to help rid the body of toxins, waste and other unwanted materials
Maintain the body balance of fluids
How is the lymphatic system organised?
Lymph
Lymphatic vessels
Lymphatic tissue and organs
What is lymph?
Fluid that resembles plasma→ lower amount of protein
(chyle→ lymph that arises int he GI tract, white, cloudy substance contains fats and dissolved lipids- chylomicrons and fat soluble vitamins)
What are the lymph vessels?
Transport lymph throughout the body
Capillaries→ trunks→ ducts→ veins
What is the structure of the lymphatic capillaries?
Single endothelial cells in basement membrane
Overlap with one another
Make reticulin- Collagen 3 to anchor cells in place
Overlapping cells allows fluid to flow inwards
→ No pressure ‘valve’ closed
→ High interstitial pressure ‘valve’ open
How does the lymph flow?
- Vessels lie adjacent to capillaries, veins and arteries
- Arranged into superficial and deep (deep to fascia)
- Deep lymphatic vessels in the limbs pass through muscles where contraction aids lymph movement
- Larger lymphatic vessels (ducts and trunks) contain smooth muscle cells in their wall
- Contraction of smooth muscle is an important contributor to lymph flow at these sites
Compare a lymphatic capillary to a normal vein?
Low pressure system
Valves present
No cells (normally)
Lymphangion→ compression by local veins and arteries propels the lymph
Compare lymphatic trunks and ducts to a vein?
Equivalent to larger veins
Large fibrocartilaginous valves
Skeletal muscle and organ movement for ‘flow’
Where does the left and right lymphatic system drain?
Right→ upper right quadrant of the body (right arm, righ shoulder, upper right chest, right half of head) into the right subclavian vein/internal jugular vein
Left→ rest of the body into the left subclavian vein/internal jugular vein
What is a lymph node?
- 600-700 of them
- Organised collection of lymphatic tissue
- Shaped like a kidney bean
- Each node has multiple afferent lymphatic vessels→ enter via convex surface
- Single efferent lymphatic vessels→ leaves via the concave hilum
- Feeding artery and draining vein that also enter and leave via the hilum
- Multiple follicles ‘nodules’ that contain the immune cells (macrophages, dendritic cells, B and T cells)
- Surrounded by a fibrous capsule
How do lymphocytes enter the lymph node?
Most through the feeding artery
How do dendritic cells enter?
Enter with pathogens within the lymph
What is lymphadenopathy?
Enlarged lymph node
Occur when fighting infection
Germinal centres fill with increasing number of lymphocytes causing the lymph nodes to swell
Can occur in all the nodal region or affect lymphatic organs
OR
Lymphoma - malignancy of lymphoid tissue itself
What are the different lymphatic organs in the body? Where are they located?
Thymus → mediastinum
Spleen → left side of abdomen
Tonsils → on the oropharynx and nasopharynx
Appendix → lower right quadrant of abdomen
Payer’s patches → under the mucosal membrane of SI
The thymus is one of the lymphatic organs, describe the anatomical location and structure of it?
Location - Superior mediastinum - Fully formed at birth, involutes after puberty and by late teens is mostly fat Structure - Similar to lymph node (but no hilum)
What is the function of the thymus?
Maturation of bone marrow derived stem cells into immunocompetent T cells
Thymic cell education
What is the largest lymphatic organ in the body?
The spleen
What is the location, structure and function of the spleen?
Inferior to diaphragm, posterior to stomach
Similar structure to lymph node, separated into white pulp and red pulp
Function→
- White pulp→ Immune part
- Red pulp→ Haemopoietic part- removes aged RBC
What are the immune functions of the spleen?
Antigen presenting by APCs
Activation and proliferation of B and T lymphocytes, production of antibodies
Removal of macromolecular antigen (e.g. charcoal) from blood
What are the haemopoietic functions of the spleen?
Removal and destruction of old, damaged, and abnormal erythrocytes and platelets
Retrieval of iron from erythrocyte haemoglobin
Erythrocyte storage
What are some clinical complication with the spleen?
Rich blood supply and is relatively fragile
- Ruptured spleen= death by exsanguination (bleed out)
- Splenectomy if damaged
Splenectomy
→ increased risk of infection by encapsulated bacteria and malaria
→ liver and bone marrow take over removal and destruction of aged RBCs
Splenomegaly
→ Enlarges in response to localised infections (like lymoh nodes)
→ Enlarges in response to systemic infection (glandular fever, malaria, septicaemia)- enlarge to 10 times it size
What is the function of the tonsils?
Prevent pathogen ingress through oral and nasal routes
Prevents pathogen ingress through aural route (adenoids)
Crypts increases surface area
Form Walderyer’s ring→ Adenoids, 2 tubal tonsils, 2 palatine tonsils and lingual tonsils
In the oropharynx and nasopharynx
What are the clinical complications associated with the tonsils?
Surface epithelia have numerous microfold (M cells)
Present antigens to underlying immune cells
Swelling due to proliferation of B and T cells
What is the veriform appendix? (location, structure, function)
- Inferior to and attached to caecum (ascending colon)
- Nodules reside inferior to surface invaginations, many M fold cells in epithelial surface
- Prevents pathogen ingress through GI routes
- Prevent pathogen ingress arriving from ileum
- Crypts increase surface area
