Cardiovascular system lecture 13&14 Flashcards
functions of cardiorespiratory system
- To carry oxygen to cells and to collect carbon dioxide
- To carry nutrients to cells and to collect waste
- To pick up oxygen from the lungs
- To pick up nutrients from the intestines
- To carry hormones and other signalling substances
- Thermoregulation
cardiorespiratory system
• The heart comprises two, side-by-side
pumps, serving different blood circuits
• The heart and lungs comprise the pulmonary circuit
• The systemic circuit moves blood to and from capillaries at cells
• By definition, arteries take blood away from
the heart; veins take blood towards the heart
circulatory system- blood’s journey
oxygenated blood from lungs to left atrium, through left atrioventricular valve (mitral valve) to left ventricle then through aortic valve to rest of body
deoxygenated blood from body to right atrium, through right atrioventricular valve to right ventricle, through pulmonary valve to lungs
valve that separates left atrium and ventricle
mitral valve
valve that separates right atrium and ventricle
tricuspid valve
early diastole
AV valves open
semilunar valves closed
all chamber relaxed, ventricles filling
atrial systole
AV valves open
semilunar valves closed
L+R atria contract; further ventricular filling
ventricular contraction
AV and semilunar valves closed
L+R ventricles start to contract
ventricular ejection
AV valves closed
semilunar valves open
L+R ventricles fully contract; blood leaves heart
ventricular relaxation
AV and semilunar valves closed
ventricles relax
Atrioventricular valves
(prevent backflow into atria)
• Tricuspid valve (right AV valve)
• Mitral valve or bicuspid valve (left AV valve)
Semilunar valves (prevent backflow into ventricles)
- Aortic valve (between left ventricle and aorta)
* Pulmonary valve (between right ventricle and pulmonary artery)
intercostal space
the space between the ribs
where to listen to Aortic valve
2nd intercostal space, right sternal margin
where to listen to Pulmonary valve
2nd intercostal space, left sternal margin
where to listen to Tricuspid valve
5th intercostal space, right sternal margin
where to listen to Mitral valve
5th intercostal space, in line with middle of clavicle
Chordae tendineae
• Largely collagen, with elastin components • As ventricles contract, tricuspid and mitral valves close • Pressure in ventricles increases dramatically • Chordae tendinae prevent the eversion of the valves into the lower pressure atria
ventricles
• Ventricles have thick walls, since they
pump blood over long distances
– LV pumps to the body
– R V pumps to the lungs
• Thickness can be diagnostic
– pumping to body requires more effort, so left ventricle usually thicker
– in arteriosclerosis, LV distended
– in emphysema, RV has to pump harder and becomes even larger
coronary circulation
• Shortest circulation in the body
• Arterial supply via left and right coronary arteries
• Both arise from base of aorta, and both divide to run anteriorly and posteriorly
• Blood from the coronary circulation is returned to the heart via the coronary sinus
• Blood is emptied into right atrium via
– superior vena cava (blood from body superior to diaphragm)
– inferior vena cava (blood from body inferior to diaphragm)
– coronary sinus (blood from myocardium
innervation of the heart
- Because the heart needs to be both excited and calmed as appropriate, innervation is via the sympathetic (via spinal nerves) and parasympathetic (via vagus) components of the ANS
- Depolarisation initiated at sinoatrial node
- Travels via atrial myocardium to atrioventricular node
- AV bundle
- Left and right bundle branches
- Purkinje fibres
Hepatic portal system
- Special set of veins that carry blood from capillary beds in the intestines to capillary beds in the liver
- It is the only part of the venous system that does not carry blood from capillary beds straight back to the heart
difference between arteries and veins
- Arteries “beat” along with the heart and blood pressure is high
- Arteries have thick, muscular walls; veins have thin, non-muscular walls
- At any one time, veins contain about 70% of the body’s blood
- Veins have low blood pressure and flow is powered by gravity – but only on the way down!
- Bringing blood back to the heart from the lower extremities against gravity is difficult
- Veins have valves that prevent backflow, which helps blood move against gravity (arteries do not)
- Muscular movements in surrounding structures help blood move against gravity
- If muscles aren’t working, blood collects in veins and valves fail (varicose veins) blood into the veins, and there is nothing to send it back
capillaries
• about 1 m m long, with an internal diameter of about 10µm
• This is just large enough for red blood cells to pass through in single file
• Capillaries can be divided into three structural types:
1. Continuous capillaries
2. Fenestrated capillaries
3. Sinusoidal capillaries
Continuous capillaries
- Most c o m m o n
- Abundant in skin, muscles
- Adjacent cells are joined by tight junctions
- Tight junctions are actually loose enough to allow limited movement of fluids and small solutes in and out of the capillaries
- Capillaries in the brain are an exception: tight junctions really are tight; this is the blood-brain
Fenestrated capillaries
- Similar to continuous capillaries, but with pores in some cells
- Much more permeable
- Common in the small intestine (where capillaries pick up nutrients from digested food) and in endocrine organs (where hormones enter the circulatory system) and in the kidney
Sinusoidal capillaries
- Very leaky
- Found only in liver, bone marrow, spleen and adrenal medulla
- Have fenestrations and fewer tight junctions, allowing large molecules and even blood cells to pass in and out
- Lining contains macrophages that destroy bacteria
- Irregular shape of lumen slows blood, giving time for all of this to occur
thermoregulation
• Central channels are vessels that traverse a capillary bed and connect arterioles to venules
• They consist of a metarteriole and a thoroughfare channel
• Contraction of precapillary sphincters forces the blood directly from the metarteriole to the thoroughfare channel, bypassing the rest of the capillary bed
• Important in thermoregulation and in the
control of blood pressure
• In many animals, including humans, the
circulatory system also controls temperature via countercurrent heat exchange
• At low external temperatures, blood
flows through veins intimately associated with arteries
• The warm blood from the heart transfers
heat to the cooler blood returning from the extremities
• This cools arterial blood and warms the
venous blood, minimising heat loss to
the environment
Capillary hydrostatic pressure (CHP)
forces fluid out of the circulatory system, but
pressure drops moving from arterial to venous end of capillaries
Blood colloid osmotic pressure (BCOP)
tends to pull water and solutes into capillaries
Net filtration pressure (NFP)
is the difference between these
foetal circulation
• No gas exchange in lungs; pulmonary vessels
vasoconstricted
• Three shunts ‘short-circuit’ circulation:
– ductus venosus
– foramen ovale
– ductus arterosus
Ductus venosus
Connects umbilical vein to inferior vena cava
bypassing liver
Foramen ovale
Right atrium to left atrium (bypassing lungs)
Ductus arteriosus
Pulmonary trunk and aorta (bypassing lungs)
Circulatory events at birth
• Umbilical artery and vein close • 1 Ductus venosus Vein through liver closes (leaving hepatic portal system as remnant) 2. Foramen ovale Foramen ovale in heart closes (called fossa ovalis in adult heart) 3. Ductus arteriosus Ductus arteriosus closes (leaving ligamentum arteriosum)
name the Ischaemic heart diseases
- Coronary artery occlusions
* Myocardial infarction
name the Valvular heart diseases
- Degenerative valvular diseases
- Rheumatic heart disease
- Bacterial endocarditis
name the different shocks
- Hypovoleamic shock
- Cardiogenic shock
- Septiceamic shock
- Anaphylactic shock
Ischaemic Heart Diseases
- This is a generic name for a group of closely related syndromes that result from myocardial ischaemia.
- In over 90%, this is due to a reduction in coronary blood flow. (Decrease in supply)
- Other conditions arise as a result of increases in demand e.g. hypertrophy, shock, increase heart rate, etc.
Diminished Coronary Perfusion
- Fixed coronary obstruction
- More than 90% of patients with IHD
- One or more lesions that causes at least 75% reduction of the cross-sectional area of at least one of the major epicardial arteries.
Angina Pectoris
• This is a symptom complex. Symptoms caused by transient myocardial ischaemia that falls short of inducing the cellular necrosis that defines myocardial infarction. • Three variants:- • Stable angina • Prinzmental angina • Unstable angina
Effects of ischaemia on myocytes
- Onset of AT P Depletion
- Loss of contractility
- AT P reduced
- to 50% of normal
- To 10% of normal
- Irreversible injury
- Microvascular injury
Laboratory detection of myocardial infarction
• This is based on the measurement of intracellular macromolecules leaked
from the damaged myocytes into the circulation
• Creatine kinase – particularly the M B isoenzyme
• Lactate dehydrogenase
• Troponin – Troponin I and Troponin T
Effects of valvular disease
• Stenosis – tightening of the valvular opening resulting in decreased flow of
blood through the opening.
• Incompetence – incomplete closure of the valvular opening, allowing
backflow of blood through the valvular opening
• Mixed.
Rheumatic fever
• Once the most common cause of valvular heart disease.
• It is an acute immunologically mediated , multi-system inflammatory disease
that occurs a few weeks after an episode of Group A (ß-hemolytic)
streptococcal pharyngitis.
what is shock
A state of generalised hypoperfusion of all cells and tissues due to reduction in blood volume or cardiac output or redistribution of blood resulting in an inadequate effective circulating volume
• A systemic (whole body) event resulting from failure of the circulatory system
• It is at first reversible, but if protracted leads to irreversible injury and death.
causes of shock
- Hypovoleamia
- Cardiogenic (pump failure)
- Anaphylactic (peripheral pooling) (return failure)
- Septic (Septiceamic) – Complex reasons
Vicious circle of pathology
pump failure
vessel injury
peripheral pooling
and repeat
