lymph Flashcards
2 types of immune response
Humoral immunity secretes antibodies to fight against antigens - B cells
whereas cell-mediated immunity secretes cytokines and no antibodies to attack the pathogens - T cells
complement cascade
- Antibodies activate the complement cascade - Complement is a system of plasma proteins that interacts with pathogens to mark them for destruction by phagocytes. In the early phases of an infection, the complement cascade can be activated
bone marrow
lymphocytes produced in bone marrow from haemopoeitic stem cells
- Also site of B lymphocyte maturation
thymus
site of maturation of immature lymphocytes - anterior mediastinum –** B cells mature into antibody-secreting plasma cells
spleen
- left upper quadrant of abdomen - where T + B interact w/ BLOOD BORNE antigens - triggers stimulation + cell division
lymph nodes
at junctions of major lymphatic vessels
- Where T + B lymphocytes interact w/ antigens + APCs from circulating lymph - leading to lymphocyte activation + cell division
MALT
mucosa associated lymphoid tissue - The total mass of lymphoid tissue in the gastrointestinal, respiratory and genitourinary tracts
- Tonsils + adenoids of oropharynx
- Peyer’s patches of small intestine
- Lymph aggregates of large intestine
Are specialised tissue - respond to antigens entering through mucosae
- NO CAPSULE OR SINUSES
- Mainly B cells - organised into follicles
- Close relationship w/ overlying epithelium
- Provide IMMUNOLOGICAL PROTECTION on exposed surfaces
primary lymphoid organs
THYMUS + BONE MARROW - where t + B cells acquire RECEPTORS to recognise antigens (maturation)
- Rest are secondary organs
lymphatic capillaries
- are usually collapsed - not visible - need to perform specific process to make visible
- have specific osmotic pressure
- openings are VALVED - allow substances in but not back out
lymphatic drainage
Intercellular space —> capillaries —> collecting vessels
—> lymph nodes —> lymphatic trunks —> thoracic duct OR right lymphatic duct
2 main lymph ducts
right lymphatic - upper right quadrant of body
thoracic duct - rest of body
lymph nodes
- small glands that filter lymph
- site of antigen dependent proliferation of B + T cells
- mandible lymphnodes = usually 1cm, easily moved
- in infection = rigid, swollen
lymph flow in lymph node
afferent vessels –> subscapular sinus –> cortical sinuses –> medullary sinuses –> efferent
cortex info
contains lymphatic nodules composed of-
- B LYMPHOCYTES
- Primary nodules - no contact
- Secondary nodules w/ germinal centre - have had contact
- Paracortex - T lymphocytes
3 functional compartments of lymph nodes
- stromal - packed with lymphocytes and APCs
- lymphatic/sinus - acts as a sieve for antigens
- vascular - delivers lymphocytes to lymphnode
tonsils
- Aggregation of lymphnodes in the nasopharynx, form an incomplete tonsillar ring
- Waldeyer’s ring
- Mucous glands present in tonsils -
- secretion needed
- every immune reaction can only take place in fluid
- why we get colds in winter
thymus
- bilobed
- located in front of mediastinum
- involutes after puberty + is replaced by fat
- PRODUCES T CELLS before puberty
- differentiates t cells after puberty
thymus structure
- Has cortex + medulla
- Recognisable in slide as it has LOBES
- Hassal’s corpuscle - only in thymus - distinguishing factor - use is unknown
spleen development
- Begins to develop In 5th week of gestation from mesenchymal cells in dorsal mesogastrium - portion of the dorsal mesentery that attaches to the greater curvature of the stomach
- Rotation of stomach causes dorsal mesogastrium to balloon out to the left - creating lesser peritoneal sac + splenorenal ligament
- Dorsal mesentry between spleen + stomach forms - gastrosplenic ligament
- INTRAPERITONEAL - Intraperitoneal means within the peritoneum. The peritoneum is a thin, transparent membrane that lines the walls of the abdominal cavity
spleen ligaments
- ligament = arteries + veins + vessels
- Gastrosplenal ligament - from anterior hilum to stomach
- Splenorenal ligament - from posterior hilum to left kidney
Between 2 ligaments = lesser peritoneal sac
spleen structure
- Covered by weak connective tissue capsule which provides protection whilst allowing it to expand
- Capsule supported by trabecular network
- Diaphragmatic surface - in contact w/ ribcage and abdomen
- Visceral surface - in contact with other abdominal viscera (internal organs)
spleen functions
STORAGE
- Platelets
- Erythrocytes
- Granulocytes
- HAEMATOPEIOTIC STEM CELLS IN FOETUS
WASTE REMOVAL
- Old RBCs
- Bacteria
- Iron
red pulp
- contains a lot of blood
- Sinusoids - splenic sinuses - capillaries engorged w/ blood- lined w/ macrophages + endothelium
- Splenic cords (cords of billroth) - formed by reticular cells (produce collagen 3) and fibres - located between sinusoids - filter blood
** endothelium lining sinuses - fenestrated - formed by elongated stave cells
white pulp
- Initiates immune response to blood borne antigens í contains lymphocytes + is a lymph component
- Composed of sub compartments
- PALS - PERARTERIOLE LYMPHOID SHEATHS
- FOLLICLES
PALS
periarteriole lymphoid sheaths
- As central arterioles enter pulp, they are surrounded by periarteriole lymphoid sheaths forming irregular masses
- Mainly a T cell zone
follicles in white pulp
- Continuous with PALS, but composed of B cells
- Occur at sites of central arteriole bifurcation
- Follicles may contain germinal centres - form upon antigen stimulation
- Germinal centres contain macrophages + apoptotic B cells
marginal zone
- interface of red + white pulp - macrophages + B cells - screens systemic circulation for pathogens - **NB FOR ANTIGEN PROCESSING
spleen vascular, nervous, venus supply
- Receives vascular supply from SPLENIC ARTERY - part of splenorenal ligament
- Arterial branches of the spleen DO NOT anastomose - cross link
- This gives rise to vascular segments
VENUS DRAINAGE – splenic vein
- Combines w/ superior mesenteric vein giving rise to PORTAL VEIN
INNERVATION = COELIAC PLEXUS
**splenic artery = identifiable as it’s highly tortuous - loop de loop
blood filtering
- Blood enters at hilus via splenic artery
- Splenic artery divides into trabecular arteries within trabeculae entering into the parenchyma / red pulp (the functional tissue of an organ as distinguished from the connective and supporting tissue)
- Small arterioles branch from the trabecular arteries and enter the red pulp - they becom central arterioles - which are surrounded by T cells
- Branches of central arterioles are given to red pulp í penicillar arterioles
penicillar arterioles
bring blood to peripheral sinusoids via open or closed networks
- closed - penicillar arterioles empty directly into sinusoids - purified blood gets into main circulatory system again via efferent veins
- open - penicillar arterioles empty openly into fibrous network of red pulp around sinusoids - must pass through mesh to reach sinusoids - filters out old RBC
