Hematology Flashcards
(28 cards)
Fluid compartments and composition
~57% of total body weight is water (average intake of water is ~2.3L/day to replace water loss)
varies with age and sex (blood volume is ~5L in women and ~5.5L in men)
obesity decreases the percentage (due to increase in fat)
may vary depending on daily intake and output of water (differs when excercised)
Intersitial fluid
fluid occupying the space between cells
dervied from filtration from the capillaries
same constituents as plasma (but plasma has large proteins present at low concentration)
blood capilaries have small pores, allowing movement of molecules but larger proteins cannot pass (remains in plasma)
What are the different fluid compartments?
Two main compartments:
1. intracellular (~28L, mostly inside of cell)
2. extracellular (~14L)
- intersitial fluid (~11L, most fluid is in between cells)
- plasma (~3L, acellular compartment of blood)
- small compartments but vital in function (i.e. CSF, intraocular fluid, fluids of GI tract)
Relative permeability
pores in capilaries vary in size depending on location in the body (larger in liver and smaller in the brain)
molecular weight (MW) is inversely related to permeability (bigger = decrease in permeability)
Colloid osmotic pressure/Oncotic pressure
osmotic pressure caused by the presence of proteins (based on protein concentration)
colloid osmotic/oncotic pressure increases when protein concentration increases
movement of water from low osmotic pressure (low protein) to high osmotic pressure (high protein) - osmosis
Three major types of proteins in the plasma
- albumin
- globulin
- fibrinogen
Albumin
most abundant plasma protein
provide colloid osmotic pressure in the plasma
act as non-specific carrier protein (does not need specifc ligands and is more physical binding = low affinity)
Globulin
less abundant compared to albumin
proteins with specificity, interaction are more specific
i.e. specific carrier proteins, enzymes, immunoglobulins
Fibrinogen
least abundant
key factor in blood clotting
polymerizes into long fibrin threads during blood coagulation
think about it.
Colloid osmotic pressure (πp)
not proportional to concentration of proteins, osmotic pressure is due to nature of size
1. albumin
2. globulins
3. fibrinogen
Starling forces
physical forces that control the movement of fluid between capillaries and tissue fluid
two major starling forces:
- hydrostatic pressure (fluid pressure i.e. blood)
- oncotic pressure (protein concentration)
Fluid movement in and out of capillary
Under normal conditions:
Outward force (outward pressure, Pc + πif) = 28.3 mmHg
Inward force (inward pressure, Pif + πp) = 28.0 mmHg
NET outward force towards intersitial compartment = 0.3 mmHg (result in slight movement of fluid from capillary to intersitial space)
Intersitial compartment
outside cell, outside circulation
contains: collagen fibers (major contributor to pressure in intersitial compartment, Pif), proteoglycan filaments (98% hyaluronic acid + 2% protein)
99% of intersitial fluid is trapped among proteoglycan filaments, resulting in a tissue gel characteristic
Edema - swelling due to accumulation of excessive fluid in intersitial compartment because there’s a finite capacity to form gel
What is the purpose of proteoglycan, gel formation, and collagen support?
- ensure uniform distribution of fluid compartments within body regardless of body position, and prevention of fluid accumulation due to gravity
maintains optimal intracellular distance - allow uniform distribution of dissolved gasses and solutes - mechanical support - give shape to body parts
Lymph system
accessory route for the transport of fluid and macromolecules from intersitial space to veins (one way drainage system into circulation)
filtered through lymph nodes (contains phagocytic cells), act as filters to remove foreign blood contaminants before drainage into veins
lymph flow is proportional to intersitial fluid pressure
Small fluid compartments
small in volume but crucial function
- cerebralspinal fluid: provide cushion and supply nutrient
- intraocular fluid: maintains sufficient pressure in eyeball, change may result in glaucoma
- fluid compartment in lung (i.e. pleural cavity, mucoid fluid): provides lubrication for easy slippage of the moving lung
- fluid compartment of pericardial cavity, peritoneal cavity, joint spaces, bone and cartilage
Pluripotential haemopoietic stem cells (PHSC)
produced in bone marrow
self-proliferation (stem cells)
Myeloid stem cells
uncommited stem cells and self renewal
remains in bone marrow
Lymphoid stem cells
undifferentiated and self-renewal
migrates to lymphoid
Differentiation factors
factors that act on stem cells and turn them into committed progenitor cells by activating/disabling certain genes (control gene expressions)
interleukins and stem cell factors increase production of all haemopoietic stem cells, expressed and produced by CD4 Helper T-cells (important for self-renewal)
- erythropoietin stimulate differentiation of erythrocytes (RBCs)
- thrombopoietin stimulates megakaryocytes differentiation (breaking apart to form platelets)
- granulocytes-monocytes colony-stimulating factor (GM-CSF) differentiation to granulocytes and monocytes
Myeloid-derived cells
- erythrocytes (red blood cells)
- platelets (important for blood clotting)
- granulocytes (neutrophils, basophils, and eosinophils)
- monocytes > macrophage (in tissues)
Lymphoid-derived cells
lymphocytes (Natural killer cells, T-cells: Helper and Killer, B-cells: plasma cells)
Haemopoiesis
production of red blood cells
proliferation and differentiation of blood cells are mediated by cytokines
Committed progenitor cells
destined to become a specific group of blood cells (no going back) once differentiation startes following stimulation by differentiation factors
