blood physiology Flashcards
cellular components of blood
- RBCs (erythrocytes)
- WBCs (leucocytes)
- platelets (thrombocytes)
plasma is ___% water
98
plasma contains what
water, ions, plasma proteins (albumin, globulin, fibrinogen), clotting factors
serum
plasma without the clotting factors
blood transports what
Oxygen, carbon dioxide, nutrients,
hormones, waste products
blood functions
- transport
- homeostasis
- protection against infections
- blood clottings
functions of RBCs
- Oxygen (O2) transport
- Carbon dioxide (CO2) transport
- Buffer
gas diffusion
high pressure –> low pressure
Gas diffuses between terminal _____ due to difference in partial pressure
bronchioles and alveoli
The rate of gas diffusion depends on the
partial pressure of gases.
how are oxygen and carbon dioxide transported in blood
can both be dissolved in blood, or bound to haemoglobin.
In addition, the majority of carbon
dioxide is transported in the form of bicarbonate
Dissolved O2 concentration =
= (PO2) x (O2 solubility at body temperature)
henry’s law
the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas
Erythrocytes (red blood cells) contain lots of _____ molecules
haemoglobin
Each haemoglobin molecule contains ___ subunits
4
Each of the 4 subunits of hemoglobin is bound to a
heme molecule
Each heme molecule (on each of the subunit of hemoglobin) binds to an
O2 molecule
→ Each haemoglobin molecule can carry up to
4 molecules O2
hemoglobin binding O2 summary
- Erythrocytes (red blood cells) contain lots of haemoglobin molecules
- Each haemoglobin molecule contains 4 subunits
- Each subunit is bound to a heme molecule
- Each heme molecule binds to an O2 molecule
→ Each haemoglobin molecule can carry up to 4 molecules O2
More red blood cells = ____oxygen that can be transported
more
Oxyhaemoglobin (Hb−O2) is formed when
O2 binds to haemoglobin
Oxyhaemoglobin is what colour
bright red-coloured molecule and so Oxygenated blood is bright red
Hb + O2 ↔ Hb−O2
reversible; where is oxygen loaded and unloaded
- Oxygen is loaded onto RBCs at the lungs (high concentration of O2)
- Oxygen is unloaded at the tissues (low concentration of O2)
The affinity of haemoglobin to O2 ____ as more O2 is bound
increases
is the curve between PO2 and O2 saturation of Hb is linear
no– sigmoidal curve
When all four heme sites are occupied by O2, the haemoglobin is said to be
saturated
when one to three of the heme sites are occupied w O2 the hemoglobin is said to be
partially saturated
A haemoglobin saturation of 100 percent would mean
every single heme unit in all of the
erythrocytes of the body is bound to oxygen.
In a healthy individual with normal
haemoglobin levels, haemoglobin saturation generally ranges from
95 to 99 percent
gases will travel from an area of higher partial pressure, to an area of
lower partial pressure
the more oxygen binds to heme, the affinity
increases
as the partial pressure of oxygen increases, a ____ percentage of oxygen molecules are bound by heme
greater
at lower partial pressures of
oxygen, ____ oxygen molecules will be bound by heme
fewer
in the lungs, at higher partial pressures of oxygen, the PO2 can change without much change in the
O2 sat, or oxygen concentration
______ plays a major role in how much oxygen is bound to heme in the lungs, as well as how much the oxygen dissociates from heme at the body tissues
partial pressure of oxygen
Although we consider venous blood returning to the heart to be deoxygenated some oxygen is still bound to haemoglobin, what is this oxygen for
This is an oxygen reserve that can be accessed when the tissues suddenly demand more oxygen.
P_50
the PO2 at 50% Hb saturation
what does P_50 indicate
Indicates the general affinity of O2 for Hb
right shift: P_50 increases
Increases O2 unloading at a given PO2
4 primary conditions in which more oxygen needed to be offloaded into peripheral tissues
- temp increase
- PCO2 increase
- decrease pH (increase H+)
- increase in metabolite of RBCs; BPG (BPG is biproduct of glycolysis)
Carbon monoxide (CO) has _____ affinity for the oxygen binding sites on haemoglobin than oxygen does
greater
HbCO of 50%
[Hb] is normal but 50% is bound
to CO rather than O2
- carbon monoxide poisoning
Anaemia
only 50% haemoglobin concentration
Converting CO2 into
HCO3-
- Carbonic anhydrase reaction
- RBC involvement
- 70-90% of CO2
Carrying of CO2 by Hb
- Hb binding
- Related to O2 content
- 5-23% of CO2
CO2 dissolved in plasma
- CO2 solubility
- 5-7% of CO2
3 ways of CO2 transport
convert, carry and dissolve
- convert; into bicarb
- carry; by Hb
- dissolve; into plasma
Chloride shift
HCO3- diffuses into the plasma
and is replaced by Cl-
Carbonic anhydrase (CA) causes carbon dioxide and water to form
carbonic acid
Carbonic anhydrase (CA) causes carbon dioxide and water to form carbonic acid, which then dissociates into two ions:
H+ and bicarbonate
bicarb concentration higher in or out RBCS
Bicarb tends to build up in the red blood cells, so there’s a greater concentration inside, than in the surrounding blood plasma
At the pulmonary capillaries what happens to RBCs in terms of bicarb and chloride
Much of the bicarb in the plasma diffuses back into the red blood cells in exchange for chloride ions (reaction reversed)
Hydrogen ions and bicarb join to form carbonic acid, which is converted back into carbon dioxide and water by carbonic anhydrase. Carbon dioxide then diffuses out of the red blood cells and into the plasma, where it diffuses across the respiratory membrane into the alveoli to be exhaled.
Carbaminohaemoglobin is formed when
haemoglobin and CO2 bind
is easily reversible
Oxygenated blood has slightly
____ CO2 than deoxygenated
lower
CO2 -Hb dissociation curve more
_____ than the O2-Hb dissociation curve
linear
Blood CO2 levels are maintained
within very _____ parameters
narrow
40 – 45 mmHg
erythropoiesis
RBC production
erythropoiesis stimulated by
erythropoietin (EPO)
erythropoietin (EPO) produced by
kidney
erythropoietin (EPO) is produced in response to
hypoxia (low oxygen in the kidney tissue)
Hypoxia
- Reduced availability of O2 at tissues
- Under-oxygenation of organs, tissues and cells
- Impairs normal metabolism
- If severe, can lead to cellular death
Hypoxaemia
- Low concentration of O2 in arterial blood (PaO2)
4 main types of tissue hypoxia
1) Cytopathic
* Mitochondrial dysfunction inhibits effective utilisation of oxygen
* Septic shock
2) Anaemic
* Blood doesn’t have enough O2 carrying capacity
3) Stagnant
* Low cardiac output
* Low tissue perfusion
4) Hypoxemic
* Low PaO2 leading to low delivery of O2 to tissues
Coagulation
Process by which blood turns from a liquid to a gel; Forming blot clot
coagulation results in
haemostasis
- Begins almost instantly when endothelium of a blood vessel is damaged
- Stops blood loss
- Followed by repair process
Haemostasis
innate response for the body to stop bleeding
3 things that happen in haemostasis
1) vascular spasm
2) primary haemeostasis
3) secondary haemostasis
vascular spasm (first step of haemostasis)
- vasoconstriction of blood vessels
- damaged vessels constrict, reducing the amount of blood flow; helping reduce blood loss.
-Collagen fibres are exposed at the site of the injury; collagen promotes the adhesion of platelets to the site of the injury
primary haemostasis (second step of haemostasis)
- Platelets immediately
form a “plug” at site of injury - Degranulate; they release granules that contain things like
- Serotonin; helps increase vasoconstriction
- ADP; attracts more platelets
- Thromboxane A2, helps platelet aggregation
- Positive feedback loop
secondary haemostasis (third step of haemostasis)
- Occurs simultaneously
- Proteins in blood plasma
(clotting factors) respond
in a complex “clotting cascade” - Form fibrin strands from inactive fibrinogen
- Fibrin strands strengthen
platelet “plug”
Granulocytes
WBCs that contain granules
include
*neutrophils
*eosinophils
*basophils
Agranulocytes
WBCs that lack visible granules, include
* B lymphocytes
* T lymphocytes
* Natural killer cells
* Monocytes (macrophages)
Innate Immune Response
non-specific immune reactions
Chemotaxis
part of innate immune response: attracted by chemical substances released
Phagocytosis
part of innate immune response: engulf and digest
innate immune response activates adaptive immune system via
antigen presentation
The major white blood cell in the circulation is the
neutrophil
usually first cells to arrive at site of infection
neutrophil
neutrophil involved predominantly in
phagocytosis
Monocytes are found in the blood, and differentiate into _____ in the tissues
macrophages
Monocytes function
phagocytic cells
Dendritic cells functions
- phagocytic
- main function is activation of T cells
- engulf antigen material, process it, and present it on their cell surface to T cells
Eosinophils, basophils and mast cells are specialised to produce
inflammatory mediators
natural killer cells function
kill infected cells
involved in cell‐mediated, cytotoxic innate immunity
adaptive immune response
Specific – adaptive immune reactions
* Immunological “memory”
* Leads to enhanced response to future exposes to pathogen
* Slower - lag time between exposure and maximal responses
cells of the adaptive immune response
B cells: Make antibodies that bind to pathogens
T cells; Including:
CD4+
* “Helper” T cells
* Help coordinate immune response
* Differentiate into Th1, Th2, Th17 and Treg cells
CD8+
* Cytotoxic T cells
* Kill infected/tumour cells without damaging surrounding tissues
How many oxygen molecules can bind to one haemoglobin protein?
4
Why does the oxygen-haemoglobin dissociation curve have a sigmoidal shape?
As each oxygen molecule binds to haemoglobin, the affinity for the next oxygen molecule is increased
Which of the following factors shifts the oxygen-haemoglobin dissociation curve to the left?
A.
High temperature
B.
High concentration of CO2
C.
Increase in pH
D.
Decrease in pH
C.
Increase in pH
Which of the following factors will shift the oxygen-haemoglobin dissociation curve to the right?
A.
Decrease in pH
B.
Decrease in body temperature
C.
Decrease in 2,3 DPG
D.
Decrease in hydrogen ion concentration
Decrease in pH
Which of the following ions is bicarbonate exchanged for in a red blood cell?
Chloride
Which of the following statements is CORRECT when comparing the CO2-haemoglobin dissociation curve to the O2-haemoglobin dissociation curve?
The CO2-Hb dissociation curve is more linear
Which of the following statements is NOT true regarding carbon dioxide transport in the blood?
A.
There is more CO2 dissolved in the blood than O2
B.
The solubility of oxygen is greater than that of carbon dioxide
C.
Less carbon dioxide is bound to haemoglobin as compared to oxygen
D.
The majority of the carbon dioxide in the body is in the form of bicarbonate ions
B.
The solubility of oxygen is greater than that of carbon dioxide
What is the first response that takes place when a blood vessel is injured?
Vascular smooth muscle cells of the damaged vessels constrict, reducing the amount of blood flow through the area
Which of the following statements BEST describes “secondary haemostasis”?
The clotting cascade leads to the formation of fibrin strands around the platelet “plug”, from inactive fibrinogen
Which of the following cells contributes towards adaptive immune responses
A.
Neutrophil
B.
CD4+ T cell
C.
Macrophage
D.
Eosinophil
CD4+ T cell
Which of the following cells identifies and removes foreign substances through phagocytosis?
A.
Basophil
B.
B cell
C.
Neutrophil
D.
Natural killer cell
C.
Neutrophil
