Blood, lymph and immunity Flashcards
Blood is and functions to
Functions to:
Provide internal transport
Regulate
Defend the body.
Blood is composed of cells suspended in plasma. The cells are:
Red Blood Cells (RBCs) or erythrocytes
White Blood Cells (WBCs)
Platelets (Cell fragments)
transportation of blood
Hemoglobin in RBC’s carry oxygen
Nutrients and other compounds are carried dissolved in plasma
Waste removal (CO2, urea, etc) – transports to lungs, liver and kidneys
Hormones – to target organ
WBCs to location of infection
Platelets to location of blood vessel damage (bleeding)
Regulation of blood
Body temperature
Tissue fluid content – provides a reservoir for fluids during dehydration and over-hydration
pH – waste products are usually acidic. Blood buffers these through the actions of three systems:
Bicarbonate buffers
Hemoglobin
Phosphate buffers
Normal blood pH is 7.4 +/-0.05
Defense mechanism in blood
WBC provide immune functions including phagocytosis
Clotting factors and platelets protect against blood loss
Peripheral blood
Blood in vessels
Whole blood
Blood as it is drawn directly from a blood vessel
Plasma vs serum
Plasma the clear liquid in which the cells are suspended
Serum is the fluid left after clotting
Blood volume calculation
Can estimate blood volume of an animal based on its lean body weight
Blood volume in liters is about 6-9% of total lean body weight.
Fit, muscular or hyper animals have greater volume
One reason Greyhounds are used as donors
How much blood can be drawn and when does blood loss cause shock
Usual blood donation is 500 mL
In general, sudden blood loss of > 30% of total volume is a life-threatening situation
Where is blood stored
During rest, the need for circulating blood is lower, so the body stores it in the spleen
Spleen acts like a sponge
When stimulated (exercise, hemorrhage), the spleen contracts and expels the blood back into circulation as needed.
Plasma is
Fluid part of blood
45-78% of the volume of a blood sample
Varies depending on species, exercise and hydration status
About 93% water
Proteins in blood
about 70% of the solutes.
Albumin, globulins, and clotting factors
such as fibrinogen and prothrombin
All proteins, but particularly albumin, contribute to oncotic pressure. Remember - this is important in maintaining vascular volume.
Some of the globulins (gamma) are immunoglobulins which are also called antibodies
Other globulins (alpha and beta) and albumin help to transport lipids and lipid-soluble vitamins (insoluble in water).
Gasses in protein
Oxygen, carbon dioxide, nitrogen
Nitrogen does not have a known bodily function
Electrolytes in plasma
sodium, potassium, calcium, magnesium, chloride, and bicarbonate and phosphate buffers
Colour of plasma and what it can indicate
Tends to be clear, pale yellow in colour in normal animals
White, cloudy appearance indicates high amounts of lipids which may be from a recent fatty meal
Normal to have a pale yellow hue in herbivores – due to plant carotenoids.
A yellow-orange color indicates bilirubin, a breakdown product of hemoglobin
So animals with a hemolytic anemia or liver disease often become icteric
Note that horses have an increase in bilirubin in fasting, this is normal and will give a moderate yellow (not yellow-orange) color to plasma.
White blood cells and granuales
Some have granules (called granulocytes) and are named according to staining characteristics
Others do not have granules (called agranulocytes: monocytes and lymphocytes)
Red blood cells
Red Blood Cells (erythrocytes): carry oxygen bound to hemoglobin
Platelets do what
Platelets: help blood to clot when vessels are damaged
Hematopoiesis is
Means production of blood cells
Continuous process due to continuous loss, use, and replacement
Site of hematopoiesis
Fetus: occurs in spleen and liver
Newborn: occurs in red bone marrow
Older animal:
Most of the hematopoietic tissue (red marrow) in the medullary cavities replaced by yellow bone marrow (mostly fat).
Hematopoiesis continues in ends of long bones and in the flat bones like hip bones, sternum, and ribs.
Liver and spleen can contribute a limited amount, but never become an important site
Hematopoiesis and PPSC
Blood cells all differentiate from a common cell type called the pluripotent stem cell (PPSC)
Various stimuli trigger the PPSC to develop into the type of blood cell required by the body
Cannot reverse the process once differentiation begins (can’t become a RBC then convert to a WBC)
PPSC’s lacking appropriate stimuli will not develop into anything
Hematopoiesis bone marrow
Complete development of most blood cell types occurs in the bone marrow. Cytology of the bone marrow shows populations of cells in various stages of development
Numbers depend on cell type and stimuli bone marrow has received to produce that type
Used to diagnose disease
Except for lymphocytes which mature in lymph tissue (i.e. thymus, lymph node, spleen)
Disease with hematopoiesis
If there is a problem or disease, this may stimulate a large release of cells
Hemorrhage – may stimulate release of RBC’s
Infection – may stimulate release of neutrophils
If the problem is very serious and sudden, immature cells may be released to get as much of the cell type into circulation as possible
Immature cells are not as effective!
RBCs shape and function
Biconcave disks with no nucleus or mitochondria.
Contain the protein hemoglobin
Function to carry oxygen to all tissues of the animal
At tissues, O2 is released and CO2 is picked up and carried back to the lungs
Formation of red blood cells
Erythropoiesis: the production of red blood cells from the PPSC in bone marrow
Stimulated by erythropoietin, produced mostly by the kidney (~85%) in response to low oxygen levels (hypoxia) in the blood.
Initiates differentiation of PPSC into RBC’s
Human erythropoietin used to stimulate RBC production in humans and animals, but often animal’s immune system will destroy it.
Has been abused in horses in an attempt to increase performance
Synthesis of new RBC’s requires iron, folic acid, and vitamin B12
Mature RBCs have no mitochondria, cannot perform Krebs cycle and rely on plasma glucose for energy!!
Why is red blood cell formation important to vet techs
Important to Vet TEchs because RBCs use glucose after blood is collected
Important to separate serum within an hour of collection to prevent errors
Falsely low glucose
Because RBC use up the serum glucose
Falsely high potassium
Because most of the body’s potassium is intracellular it will shift form inside the RC to the serum
Hemoglobin as and does what
A protein composed of two parts; one globin with 4 heme molecules attached = 1 hemoglobin
Heme: each heme molecule has an iron atom portion (Fe++) tha binds to oxygen molecule
Almost all oxygen in blood is bound to hemoglobin
Types of hemoglobin
Hgb that is carrying oxygen attached to each iron molecule is called oxyhemoglobin and appears bright red
Hgb that has no bound oxygen is called deoxyhemoglobin and appears dark red (sometimes purple)
Hgb bound to carbon monoxide is called carboxyhemoglobin and appear cherry red
hemoglobin and gasses
Carrying gasses
Ability of Hgb to carry and hold oxygen depends on pH, temperature, and the concentration of oxygen and carbon dioxide gasses in the air and blood (partial pressures)
Carbon dioxide transport
Some simply dissolves in the plasma
Some is bound to proteins and Hgb (not at the oxygen site)
The majority is transported as bicarbonate
RBCs are very important in bicarbonate formation because they contain an enzyme that catalyzes the formation of carbonic acid
CO2 diffuses into RBC, combines with water to make carbonic acid, then dissociates to produce hydrogen ions and bicarbonate
At the lungs, the reverse occurs, and CO2 is breathed off
