Transport in mammals Flashcards
2 parts of mammalian circulatory system
what type of circulatory system is it then?
systemic and pulmonary
double circulatory system
mammalian circulatory system
a closed network of blood vessels that carry blood away from the heart, transport it to the tissues of the body, and then return it to the heart.
pulmonary system
carries blood between the heart and lungs
systemic system
carries blood between the heart and the rest of the body
2 subdivisions of the systemic system
coronary circulation
hepatic portal circulation
coronary circulation
supplies the heart muscle
hepatic portal circulation
runs from the gut to the liver
overview of circulation through the heart
deoxygenated blood arrives from the right side of the heart via the vena cava and is pumped out of the right ventricle via the pulmonary artery to become oxygenated at the lungs before returning back to the left side of the heart via the pulmonary vein and returning to the rest of the body via the aorta
venous system
returns blood from the capillaries to the heart
arterial system
carries blood from the heart to the capillaries
portal systems
carry blood between 2 capillary beds
pulmonary vein
carries oxygenated blood from the lungs to the heart
superior vena cava
receives deoxygenated blood from the head and body
inferior vena cava
receives deoxygenated blood from the lower body and organs
hepatic vein
carries deoxygenated blood from the liver
hepatic portal vein
carries deoxygenated, nutrient-rich blood from the gut for processing
renal vein
carries deoxygenated blood from the kidneys.
aorta
carries oxygenated blood to the body, branching to form the carotid arteries supplying the head and neck
pulmonary atrery
carries deoxygenated blood to the lungs
abdominal aorta
supplies organs of abdominal cavity
hepatic artery
carries oxygenated blood to the liver
mesenteric artery
carries oxygenated blood to the gut
renal artery
carries oxygenated blood to the kidneys
blood
complex connective tissue made up of cellular components suspended in matrix of liquid plasma.
role of blood
transports nutrients, respiratory gases, hormones and wastes.
distributes heat in thermoregulation
aids immune response and clots to prevent pathogens entering blood or blood loss
white blood cells
involved in internal defence
platelets
small, membrane-bound cell fragments
red blood cells
transport oxygen bound to haemoglobin and a small amount of carbon dioxide. no nucleus and are made up of haemoglobin protein
plasma
watery matrix transporting dissolved substances, providing cells with water, distributing heat and maintaining blood volume
what does plasma contain
dissolved proteins, glucose, amino acids, vitamins, minerals, urea, uric acid, carbon dioxide, hormones and antibodies
wrights stain
differentiates the cells, contains eosin
what does eosin do?
stains cytoplasm orange-pink
methylene blue
stains nuclei blue
arteries
thick-walled blood vessels carrying blood away from the heart to the capillaries, branch to form arterioles which deliver blood to capillaries
arterioles
y consist of only an endothelial layer wrapped by smooth muscle fibres at intervals along the length
vasoconstriction
increases blood pressure as the walls contract
vasodilation
decrease blood pressure as walls relax
artery structure
large lumen and thick muscle walls which allow them to withstand the pressure of blood pumped to the heart while maintaining it with the contractile ability
how does the muscle mass of arteries change as you go further from the heart?
closer to the heart, the heart has more elastic tissue and so have greater resistance to the higher blood pressures.
arteries further from the heart have more muscle to maintain blood pressure
three main regions of arteries
tunica intima (endothelium) tunica media tunica externa
endothelium
thin inner layer of squamous endothelial cells
tunica media
thick central layer of elastic tissue and smooth muscle that can stretch and contract
tunica externa
outer connective tissue layer with elastic tissue, anchors the artery to other tissues and allows it to resist overexpansion
role of the elasticity of outer layers in the arteries
even out surges from the heart as the heart pumps blood
role of smooth muscle in the arteries
regulates blood flow and pressure by contracting and relaxing to alter arterial diameter and adjust blood volume
veins
blood vessels that return blood from the tissues to the heart, branching off into venules.
venules
return blood from the capillaries to the veins
structure of veins in comparison to arteries
less elastic and muscle tissue, thicker tunica externa and larger lumen
less elastic than arteries but can adapt to changes in pressure and volume of blood
veins have valves
venules structure
endothelium and a tunica externa of connective tissue. as they get closer to veins, have tunica media
characteristics of blood in veins
low pressure as have passed through narrow capillary vessels, meaning require valves
vein structure
valves prevent backflow
endothelium
tunica media is markedly thinner than arteries, layer of smooth muscle with collagen fibres
tunica externa has layer of collagen thicker than in arteries
capillaries
small, thin-walled vessels allowing exchange of substances between the blood and tissues and connecting arterial and venous circulation, form networks/beds and are abundant where metabolic rate is high. fluid leaking from capillaries bathe the tissues
structure of endothelium
thin endothelium (one cell thick)
basement membrane
diameter of 4-10 micrometers
how do capillaries aid in bathing the tissues
blood pressure at arterial end causes fluid to leak from capillaries through fenestrations to bathe the tissues and supply nutrients and oxygen to the tissues and remove waste. some returns to the blood at the venous end of the capillary bed while some is drained by lymph vessels to form lymph
smooth muscle in comparison to cardiac muscle
less active than cardiac muscle and relies on anaerobic metabolism, not requiring as much of a blood supply
lymph
drains excess tissue fluid and returns to general circulation and has a role in immune system.
tissue fluid composition
leucocytes, hormones and proteins
lymph composition
lymphocytes and carbon dioxide
microcirculation
the flow of blood through a capillary bed
2 types of vessels in a capillary bed
capillaries and a vascular shunt
vascular shunt
connects arterioles and venules at either end of the bed, diverting blood flow past capillaries with low metabolic demand
structure of a capillary network
capillaries are branching networks of small blood vessels connected between the venous and arterial end, outside of a vascular shunt
smooth muscle sphincters
regulate blood flow through the capillary network by contracting to restrict blood flow to the network and relaxing to let blood flow in. contract to allow a vascular shunt to work.
how does a portal venous system differ from other capillary systems?
drains blood away from one capillary network into another
tissue fluid function
provides oxygen and nutrients to the body’s tissues
how does tissue fluid reach the cells?
moves in and out of the cells by diffusion, cytosis and fenestrations
what effects the direction fluid moves in the capillary membranes?
balance between blood pressure and oncotic pressure at each end of a capillary bed
oncotic pressure
colloid osmotic pressure pulls water into the capillaries
It is the pressure created by blood proteins
Pressure at the arteriolar end of a capillary bed
Capillary hydrostatic pressure exceeds oncotic pressure, allowing fluid and solutes to leak out through the capillary walls.
Net outward pressure
What happens to the tissue fluid once it has left the capillary
Some is collected by lymph vessels and returned to circulation near the heart while the rest returns to the capillary at the venous end
Pressure at the venous end of a capillary bed
Oncotic pressure exceeds hydrostatic pressure, pulling water and solutes into the capillary
Net inward pressure
Haemoglobin
Respiratory pigment in red blood cells which binds oxygen and increases the efficiency of its transport and delivery to tissues throughout the body.
Myoglobin
Where oxygen from haemoglobin is transferred to and retained in the muscles (oxygen store within the muscles)
Consists of only one haem-globin unit.
Greater affinity for oxygen than haemoglobin.
Releases oxygen during periods of prolonged / extreme muscular activity.
What is most of the carbon dioxide in the blood carried as?
Bicarbonate (HCO3-)
Formed in red blood cells in a reversible, enzyme catalysed reaction.HCO3 diffuses out of the red blood cells into the plasma, contributing to the buffer capacity of the blood.
What happens when carbon dioxide levels rise too quickly?
H+ can accumulate in the blood and reduce pH, providing a strong stimulus to increase breathing rate in the medullary respiratory centre
Gas exchange membrane
Formed by the epithelial cells of alveolus and capillary together
Half a micrometer across, allowing fast diffusion
What happens when oxygen levels are too high?
Haemoglobin binds with a lot of oxygen so that it becomes saturated
3 ways carbon dioxide is carried around in the blood
Dissolved in plasma (5%)
Bicarbonate in cells and plasma (75-85%)
Carb amino haemoglobin (10-20%)
Chloride shift
Diffusion of chloride into the red blood cell to counter the loss of bicarbonate ions
Reaction by which bicarbonate is formed
CO2 and water react (catalysed by enzyme carbonic anhydrase) to form carbonic acid which then forms bicarbonate and a hydrogen ion
What happens to the hydrogen ion produced by the reaction of water and carbon dioxide
Picked up by Hb to form haemoglobinic acid
Acts as blood buffer
What happens to bicarbonate in the blood?
Combines with sodium once diffused into the plasma
How is oxygen carried in the blood?
Is carried in a chemical combination with haemoglobin in red blood cells
How does oxygen tension affect oxygen’s combination with Hb
Higher the oxygen tension, the more oxygen will combine with Hb
X axis of oxygen-haemoglobin dissociation curve
Oxygen tension
Y axis of oxygen-haemoglobin dissociation curve
Percentage saturation of haemoglobin with oxygen
Bohr effect
As pH increases (lower CO2), more oxygen is combined with Hb
As pH decreases (more CO2), less oxygen is combined with Hb
how do you work out the amount of oxygen released to the tissues from an oxygen-haemoglobin dissociation graph?
difference in Hb saturation at high and low pH
regions of high oxygen in the body
lung capillaries and alveoli
regions of high carbon dioxide in the body
capillaries leaving the tissues and in the cells of body tissues
role of reversible binding reaction of Hb with oxygen
to take up oxygen where oxygen tensions are high and carry oxygen to where it is required before releasing it
how is foetal Hb different to adult Hb
foetal haemoglobin has a much higher affinity for oxygen than adult haemoglobin, enabling oxygen to be passed from maternal Hb to foetal Hb across the placenta.
Myoglobin affinity for oxygen
very high as is then able to pick up oxygen from Hb and store it in the muscles
contributors to the buffer capacity of the blood
haemoglobin picks up H+ formed by dissociation of carbonic acid, bicarbonate and blood proteins
what happens at high altitude
pressure decreases with altitude and so does pressure of oxygen in the air decreases
physiological effect on heart rate at high altitude
HR increases while stroke volume remains the same.
overall increase in cardiac output
physiological effect on kidneys at high altitude
kidneys produce EPO (erythropoietin)
what does erythropoietin do
increased production of red blood cells in the blood by the bone marrow
effect on breathing at high altitude? effects of this?
hyperventilation increases volume of oxygen in blood while decreasing volume of carbon dioxide.
makes body fluids more alkaline
kidneys response to increased alkalinity of body fluids?
removes bicarbonate from the blood
why is hyperventilation caused?
low oxygen pressures in the blood induces a hypoxic response, stimulating oxygen-sensitive receptors in the aorta to induce hyperventilation
effects of increased number of red blood cells in the blood
more haemoglobin in the blood, allowing more oxygen to be transported
increased viscosity of the blood
initial symptoms of high altitude
dizziness, breathlessness, headache, nausea, fatigue, coughing
(altitude sickness)
pericardium
function?
double layered connective tissue of the heart, prevents over distension of the heart and anchors it within the central compartment of the thoracic cavity
chordae tendinae
non-elastic strands supporting the valve flaps
semi-lunar valve
prevents blood flow back into the ventricle
septum
separates ventricles
how are the high oxygen demands of the heart supported?
dense capillary network branching from the coronary artery
location of the coronary arteries
arise from the aorta and spread over the surface of the heart, supplying cardiac muscle with oxygenated blood
which carries more blood, the left or right coronary artery?
the left artery carries 70% of the coronary blood supply and the right carries the remaining 30%
function of the coronary veins
carries away the deoxygenated blood from the heart and returns to the right atrium via a large coronary sinus.
why is the heart asymmetrical?
the left side of the heart is thicker and more muscular than the right due to the pressure differences the pulmonary and systemic circulations
left side must develop enough added pressure for the muscles blood flow to the muscles of the body and maintain kidney filtration rates without decreasing blood flow to the brain.
why must the pulmonary circulation be at a much lower pressure than the systemic ?
so that fluid isn’t forced through the alveoli at the lungs, causing drowning
the systemic circuit must operate at a higher pressure so as to maintain high glomerular filtration rates (kidneys) while still having enough pressure to supply blood to the brain
valves function
prevent backflow of blood in the heart and regulate filling of the chambers
why does the heart need its own blood supply
to meet the high oxygen demands of the heart tissue
requires a system to return waste products and deoxygenated blood back to the right atrium
what are you recording when you take a pulse?
expansion and recoil of the artery that occurs with each contraction of the left ventricle.
apex
the narrow, pointed end of the heart
base of the heart
wider end of the heart where the blood vessels enter
cardiac cycle
the sequence of events of a heartbeat
three main stages of cardiac cycle
atrial systole
ventricular systole
complete cardiac diastole
atrial systole
ventricles relax as blood flows into them from atria passively (70%) before the atria contract to force the last remaining blood into the ventricles.
forces semi-lunar valves closed to create lub sound
ventricular systole
atria relax as ventricles contract, pumping blood into the aorta/pulmonary artery
forces the atrioventricular valves shut (heart sound)
full cardiac diastole
semi-lunar valves close to prevent backflow into ventricles
and blood fills atria and causes the cardiac cycle to begin again
QRS complex
corresponds to the spread of the impulse through the ventricles causing them to contract
P wave
spread of the impulse from the pacemaker through the atria so that they contract
T wave
signals recovery of electrical activity of ventricles as they relax
when is aortic pressure the highest
during ventricular contraction (when ventricular pressure is highest)
electrical event preceding increase in ventricular pressure
QRS wave
when is ventricular pressure the lowest?
during diastole
why is there an electrical recovery in the T wave?
prevents fatigue in the heart so it doesn’t contract
myogenic
originating within the cardiac muscle itself
how is the heartbeat regulated ?
by a pacemaker and a specialised conduction system
what influences the heartbeat
pacemaker sets the basic rhythm
can be affected by hormones/cardiovascular control centre
nodal cells
what are they
function
sinoatrial node and atrioventricular node
generate rhythmic action potentials (without neural stimulation)
normal resting rate of self-excitation of the SAN
50 beats per minute
cardiac output
amount of blood ejected from the left ventricle per minute
formula for cardiac output
heart rate times stroke volume
stroke volume
volume of blood ejected from left ventricle with each contraction
how does blood volume affect the strength of contraction? why?
greater blood volume, greater force of contraction
regulates stroke volume in response to demand
epinephrine
hormone increasing heart rate in preparation for vigorous activity
main mechanism for controlling cardiac output to meet changing demands
changing the rate and force of heart contraction
intercalated discs
specialised electrical junctions allowing impulses to spread rapidly through the heart muscle
sinoatrial node
pacemaker of the heart
small mass of specialised muscle cells on the wall of the right atrium, near the entry point of the vena cava
sets the basic heart rate
how does the sinoatrial node act as a pacemaker?
spontaneously generates action potentials that cause the atria to contract
atrioventricular node
location
base of atrium
atrioventricular node function
delays the impulse so that time is left for atrial contraction to finish before ventricles contract
atrioventricular bundle
tract of purkyne fibres that distribute action potentials over the ventricles to cause ventricular contraction
