6b. Transport in the blood Flashcards
What is the blood made up of
Plasma
Platelets
RBC
WBC
What can blood transport
-CO2 from the organs to the lungs
-Soluble products of digestion from the small intestine to the other organs
-Urea from the liver to the kidneys
What do RBC do
Transport oxygen from lungs to the organs using haemoglobin.
They have no nucleus
What does a WBC do
Form part of the bodys defence against microorganisms
They do have a nucleus
What do platelets do
Small fragments of cells
Help blood to clot at the site of a wound
They have no nucleus
What are the different types of WBC found in the blood
Lymphocytes (B and T cells)
Phagocytes
What is the lifecycle of a RBC
About 120 days
Their membranes become more and more fragile until they are destroyed - normally in the spleen
What are 3 unusual things about RBC
Very small
Shaped like a biconcaved disc
Have no organelles
Why are RBC very small
Every haemoglobin molecule is near to the cell’s membrane
Short diffusion pathway for oxygen
Large SA:V
Why are RBC biconcaved
Increases SA:V
Oxygen can quickly diffuse in and out
Short diffusion pathway
Why do RBC have no organelles
Can carry as much haemoblobin and as much oxygen as possible
What is tissue fluid
Cells are bathed in tissue fluid, which provides them with water, oxygen, glucose and other nutrients
Essential for the efficient exchange of materials between the blood and the cells
Constantly being formed at the arteriole end of capillaries and reabsorbed at the venule end
How are capillaires suited to their function
· Pores in wall to increase permeability
· Small size and large numbers of capillaries give a large SA:VOL ratio
· Narrow diameter – slows blood flow, so more time for diffusion/exchange
What is the hydrostatic pressure of the blood in the arteriole end of the cappilary
Its high
Due to the contraction of the left ventricle in ventricular systole
What two opposing forces affect the formation and reabsorption of tissue fluid
-The high BP forces out water, salts and nutrients
-The soluble plasma proteins in blood, which reduces WP of the blood. Creates a WP gradient which exertts a pulling force, opposing loss of fluid
Why dont plasma proteins leave the capillary along
Too large to fit through capillary pores
How is tissue fluid formed
At the arteriole end of capillaries, the BP is greater than the WP gradient.
So water and solutes are forced out of the blood through the pores in the capillary walls forming the fluid
How does tissue fluid exchange substances with cells
Freshly formed tissue fluid has a high concentration of oxygen, glucose and mineral ions needed by the cells
Substance diffuse into cells
Waste products diffuse out of the cells into tissue fluid then into the capillaries along with water at the venule end
Tissue fluid is the site of the exchange of metabolites
What happens to blood as it passes trough capillaries
As blood moves from the ateriole to the venule end of the capillary, there is a fall in the BP and so the outward force is much reduced
What happens to WP through the capillaries
-WP at venule end is low
PP remain inside the capillary
-WP in the tissue fluid is high
large, inward osmotic pull which is now greater than the outward BP
-Water is drawn back into capillaries by osmosis down a WP gradient at the venule end
What happens to suplus tissue fluid
More fluid leaves the capillaries than is reabsorbed
Drains into the lymphatic vessels
Blind ending tubes with valves which return to the blood via the thoracic duct in the neck
Summarise tissue fluid formation + reabsorption
-At arteriole, outward BP is greater than inward WP gradient from PP
-Water, ions and small molecules are filtered / forced out of blood into spaces between cells
-Loss of fluid from blood leads to fall in BP at venule end
-At venule, inward osmotic pull exceeds the outward BP and some water re-enters by osmosis down a WP gradient
-TF is drained from cells by lymph vessels and returned to blood
What is the solubility of oxygen in water
Relativley low, but oxygen carrying capacity of the bloodis increased by the presence of blood pigments
What does haemoglobin do
Blood pigment with a high affinity for oxygen and readily loads oxygen where O2 concs are high
Unloads O2 where O2 conc are low
Why is haemoglobin a conjugated protein with a quaternry structure
Conjugated - Protein is bound to a non-protein group
-Quaternary - protein has more than one polypeptide chain
What is the name of haemoglobin bound to oxygen
oxyhaemoglobin
What is percentage saturation
The amount of oxygen carried by haemoglobin when refered to as a percentage of the maximum that can be carried
What is cooperative binding
Each haemoglobin molecule combines with four moleucles of O2 in 4 separate reversible reactions
Binding of the first haem grp with O2 changes te tertiary structure and shape of haemoglobin
This uncovers the 2nd haem grp
Making it more accessible and easier for oxygen to bind
increasing the affinity
This increases the affinity of the 3rd haem grp etc
Explains why the oxygen dissociation curve has a sigmoidal shape
What is the oxygen dissociation curve for haemoglobin
a graphical representation of the behaviour of haemoglobin when subjected to differing partial pressures of oxygen
Partial pressure of oxygen is shown as pO2
Curve is sigmoidal and displays the % saturation of haemoglobin with oxygen at varying pO2
What is the dissociation curve for haemoglobin influenced by
Temperature
pH
CO2 conc
What is the Bohr shift
dissociation curve for haemoglobin is influenced by an increase is temp, pH , CO2 conc
Displaces curve to right
It facilitates delivery of oxygen to the respiring tissues
How does the size of a mammal relate to the oxygen dissociation curve
Smaller mammals have haemoglobin with lower affinity for oxygen in order to facilitate oxygen delivery to the tissues
They have larger SA:V so lose heat faster
Have increased respiration rates to release more heat to replace what is lost
Have a higher rate of O2 consumption per gram of body mass due to the faster respiration
What does high affinity haemoglobin look like
- In organisms that live in low pO2 environments
-Haemoglobin loads O2 more readily
-Curve shifts to left
-Haemoglobin is more saturated at any given po2
What does lower affinity haemoglobin look like
- Usually in organisms that have high metabolic rate (e.g. small mammals with large SA:volume ratio and high rates of heat loss)
- Haemoglobin unloads oxygen more readily at tissues for respiration
- Curve shifted to right
- Haemoglobin has reduced saturation at any given pO2
