blood and lymph Flashcards
what are the 4 key functions of the blood
transport of nutrients, gases, hormones, waste. restriction of fluid loss during injury. defence from infection. homeostasis,
what are the routes of transport
paracellular and transcellular
what is the paracellular route
paracellular route is where molecules diffuse in between endothelial cells, regulated by tight and gap junctions.
what are the 3 transcellular routes
the transcellular route is for larger molecules where they are actively transported. this can happen through receptor mediated endocytosis, or transcytosis where cells take up extracellular medium through CAVEOLAE MEDIATED MACROPINOCYTOSIS. or via transendothelial channels such as vesicular vacuolar organelles which are interconnected vesicles forming channels across the cell
what is the endothelial cell permeability
organs where there is a lot of exchange such as filtration or nutrient absorption need greater permeability
how is greater permeability in endothelial cells achieved
fenestrated endothelial has looser junctions between the cells this is seen in endocrine glands, gi mucosa or glomerulus. there are discontinuous epithelium in the liver where are characterised by fenestrae without diaphragms and poorly organized basement membrane
what is a further advantage of discontinuous epithelium
these ECs have a high level of clathrin-mediated receptor endocytosis activity, further
increasing their ability to take up specific molecules.
where is continuous ec found
skin lung and heart, founds with caveolae, tec and intercellular clefts
how is transport controlled in the brain
formed by tighter endothelial junctions, a thicker basement membrane and a supporting layer of astrocytes. BBB prevents entry of lipophilic neurotoxins by an active transport mechanism mediated by p-glycoprotein
why is endothelial permeability important in organs
can charge during infection or tissue damage. antibodies and antibiotics cannot cross
what is a key hallmark of inflammation
flow of plasma and WBC, local endothelial cells increase permeability so that plasma protein can exit and reach the tissue
describe red blood cells
biconcave disk, enucleated, haemoglobin carriers,
components of blood by density using centrifuge?
first haematocrit, then buffy coat of WBC and platelets, then plasma containing water/proteins/nutrients/hormones
what is the life span of the RBC
3 months
where does erythropoiesis
bone marrow in adults, spleen and liver in fetus
describe erythrocytes
differentiate into erythrocytes by losing the nucleus ribosomes and organelles
how is erythropoiesis regulated
important to adjust to environment with different levels of oxygen. the hormone erythropoietin also has regulatory role
what does EPO do
produced by the kidney and regulated by negative feedback, low oxygen conc stimulates release of EPO stim release of erythrocytes
what does high levels of EPO result in (feedback loop)
high oxygen levels which then suppress production of EPO
what regulates the hypoxia response
regulated by the transcription factor Hif-A (hypoxia inducible factor)
what happens in normoxia
hif-A is hydroxylated and leads to degradation
what happens to hif-A in hypoxia
hydroxylases acitivity is reduced and hif1-a can activate transcription of EPO.
how are RBC eliminated
through macrophages in the liver and spleen. important because rbc release hb and iron which can damage kidney
what do erythrocytes carry on their surface
protein antigens that can be recognised by antibodies of a different individual
what do rh positive individuals have on their surface
rh antigen
what are the role of wbc
fight infection, exit blood stream, active amoeboid movement to navigate through tissues and eliminate microbes
name different types of granulocytes
neurtrophils, eosinophils, basophils
what do neutrophils do
crucial for bacterial infections and most abundant
what is role of eosinophils
role in parasitic infections, granules contain peroxides and enzymes toxic to parasites
what do basophils do
produce histamine and heparin, role in allergy
name the agranulocytes
t and b lymphyocytes, monocytes, megakaryocytes
what do t lymph do
kill infected cells or produce signals that assist function of other immune cells
what do b lymph do
produce antibodies
what do monocytes do
differentiate into macrophages and dendritic cells that can mediate phagocytosis and activation of t cells
what do megakaryocytes
large multinucleated cells whos segmentation gives rise to platelets. the latter are important in haemostasis, response of vessels to local injury/disruption
outline process of haemostasis
endothelium rupture > vascular spasm > vessel decreases in diameter.
platelets aggregate at the site to form a plug. they release factors triggering coagulation reaction.
fibrinogen > fibrin by thrombin. fibrinolysis follows.
plasminogen > plasmin which breaks down fibrin
bradykinin a vasodilator releaxes muscles and restores blood flow
functions of lymphatic system 4
returns interstitial fluid and plasma proteins into blood, filters blood by removing harmful agents, provides structural basis for immune system, transports dietary lipids from gastrointestinal tract to blood
is lymphatic a closed circulation
no
are lymphatic vessels more permeable than blood vessels
yes, allowing passage of proteins and even cells
describe structure of lymphatic vessels
blind ends with openings in the form of overlaid flaps allowing passage of interstitial fluid called lymph
how is lymph flow facilitated
muscle movements during breathing, exercise, good posture
where is lymph filtered
in lymphoid tissues ending up in the thoracic duct which feeds into the subclavian vein and returns filtered blood into the circulation
cells present in lymph
lymphocytes, macrophages, dendritic cells
name lymphoid organs
primary lymphoid organs e.g. bone marrow and thymus. secondary lymphoid organs e.g. lymph nodes, spleen and mucosa associated lymphoid tissue
what do primary lo do
produce blood cells
what do secondary lo do
enable immune responses sites of immunosurveillance
outline the role of the bone marrow
site of hematopoiesis, production of blood cells throughout life by hematopoietic stem cells. haematopoiesis declines with age by replacement of h tissue by fat
outline the thymus
located behind the sternum above the heart and constitutes the site of mature t lymphocyte production. t precursors migrate to the thymus from the bone marrow
what is the critical role of the thymus
selecting lymphocytes that will react with foreign and not self components.
when does the size of the thymus change
decreases with age leading to reduced amount of naive t lymphocytes
role of lymph nodes
drain interstitial fluid from peripheral tissues whilst removing harmful toxins and pathogens. lymph enters from afferent lymphatic vessels and filtered lymph exits through efferent vessels, the node is surrounded by a capsule
role of spleen
remove old red blood cells and filter blood borne antigens. also serves as location for initiation of immune reponses to blood pathogens.
why is spleen highly vascularised
to enable good filtration
describe the structure of the spleen
surrounded by weak capsule, below capsule is RBC rich area called red pulp where blood antigens are filtered and rbcs removed and wbc rich area called white pulp where lymphocytes initiate immune reponses to blood pathogens
what is mucosa associated lymphoid tissue
lymphoid tissues attached to mucosal surfaces of the gastrointestinal tract or respiratory tract to provide additional pathogen filtering
how does lymphatics provide structural support for immune responses
the immune system produces lymphocyte clones with unique receptors for a specific microbial determinant and only a few of them are able to react with a specific antigen from an invading pathogen. these clones have to detect an invading pathogen anywhere in the body
how do lymphatic clones achieve this detection
constant recirculation of lymphocytes through the lymphatic system. naive lymphocytes transit through the blood, nodes and spleen and return to the blood via the thoracic duct
how do lymphocytes enter lymph nodes
through specialised venules called high endothelial venules
where do b cells accumulate inside the node
follicles in the cortex, they recognise and bind antigens brought by lymph into the follicle
where do t cells accumulate inside the node
paracortex right beneath the cortex, they recognise antigens on antigens presenting cells that arrive in the area
how do lymphocytes encounter antigens
small extracellular antigens travel in soluble form form a certain tissue to the closest draining lymph node via the lymph. entire microbes and larger molecules are engulfed by APCs . APCs then migrate to the nearest lymph node to present antigen to the lymphocyte clone of relevance.
where do blood borne antigens travel
to the spleen, either in soluble form or after being picked up by APCs in the blood
