Heart and Lungs Week 4 Flashcards
Understand the normal maintenance and control of blood pressure ?
Blood pressure is measured in millimetres of mercury (mmHg) and is given as 2 figures:
systolic pressure – the pressure when your heart pushes blood out
diastolic pressure – the pressure when your heart rests between beats
Regulation of blood pressure is an example of negative feedback.
Blood vessels have sensors called baroreceptors that detect if blood pressure is too high or too low and send a signal to the hypothalamus.
The hypothalamus then sends a message to the heart, blood vessels, and kidneys, which act as effectors in blood pressure regulation. If blood pressure is too high, the heart rate decreases as the blood vessels increase in diameter ( vasodilation ), while the kidneys retain less water.
These changes would cause the blood pressure to return to its normal range. The process reverses when blood pressure decreases, causing blood vessels to constrict and the kidney to increase water retention.
Baroreceptors are sensory neurons that monitor arterial blood pressure. Major baroreceptors are located in the carotid sinus (an enlarged area of the carotid artery just above its separation from the aorta), the aortic arch, and the right atrium.
How does Antidiuretic hormone (ADH) effect blood pressure ?
Antidiuretic hormone (ADH), a hormone produced by the hypothalamus and released by the posterior pituitary, raises blood pressure by stimulating the kidneys to retain H 2O (raising blood pressure by increasing blood volume).
How does Atrial natriuretic peptide (ANP) effect blood pressure ?
Atrial natriuretic peptide (ANP), a hormone secreted by the atria of the heart, lowers blood pressure by causing vasodilation and by stimulating the kidneys to excrete more water and Na +(lowering blood pressure by reducing blood volume).
What is the effect of alcohol on blood pressure ?
increases blood pressure
What is the effect of nicotine on blood pressure ?
Nicotine in tobacco raises blood pressure by stimulating sympathetic neurons to increase vasoconstriction and by stimulating the adrenal medulla to increase secretion of epinephrine and norepinephrine.
What effect does epinephrine (aka adrenaline ) have on blood pressure ?
Epinephrine and norepinephrine, hormones secreted by the adrenal medulla, raise blood pressure by increasing heart rate and the contractility of the heart muscles and by causing vasoconstriction of arteries and veins. These hormones are secreted as part of the fight‐or‐flight response.
Know which arteries most useful for determining pulse and arterial perfusion ?
- Pulse pressure is the difference between systolic and diastolic blood pressures.
Pulse Pressure = Systolic Blood Pressure – Diastolic Blood Pressure
The systolic blood pressure is defined as the maximum pressure experienced in the aorta when the heart contracts and ejects blood into the aorta from the left ventricle (approximately 120 mmHg). The diastolic blood pressure is the minimum pressure experienced in the aorta when the heart is relaxing before ejecting blood into the aorta from the left ventricle (approximately 80 mmHg). Normal pulse pressure is, therefore, approximately 40 mmHg.
The radial artery is most commonly used to check the pulse.
Describe the functional histology of arteries and arterioles ?
There are 3 main types of arteries
Describe the 3 main types of arteries ?
3 main types of arteries: elastic, muscular and arterioles
- Elastic arteries - these arteries receive blood directly from the heart (aorta and pulmonary artery). These need to be elastic so when the heart contracts and ejects blood into these arteries, the walls need to stretch to accommodate the blood surge. Between heart contractions the elastic walls recoil to maintain blood pressure even when the ventricles are relaxed.
- Muscular arteries - distribute blood to different parts of the body. They include femoral and coronary arteries. The walls of these arteries have lots of smooth muscle which means they are able to contract or relax to chnage the
- Arterioles
Describe the 3 main types of arteries ?
3 main types of arteries: elastic, muscular and arterioles
- Elastic arteries - these arteries receive blood directly from the heart (aorta and pulmonary artery). These need to be elastic so when the heart contracts and ejects blood into these arteries, the walls need to stretch to accommodate the blood surge. Between heart contractions the elastic walls recoil to maintain blood pressure even when the ventricles are relaxed.
- Muscular arteries - distribute blood to different parts of the body. They include femoral and coronary arteries. The walls of these arteries have lots of smooth muscle which means they are able to contract or relax to change the amount of blood delivered.
- Arterioles - are small arteries that deliver blood to capillaries.
Describe the histology of arterioles ?
- lumen is very small
- The tunica intima is very thin, and mostly consists of a single layer of squamous epithelium.The tunica media consists almost entirely of a single layer up to six layers of smooth muscle cells, and there is no EEL. The Tunica adventitia is about the same size as the tunica media layer, merges in with surrounding tissue.
Describe the histology of muscular arteries ?
- compared to elastic arteries have much less elastic layer and more smooth muscle.
Review the location and function of alpha and beta adrenoreceptors in the CVS ?
Beta-1 receptors, Beta-2, Alpha-1, and Alpha-2 receptors, are adrenergic receptors primarily responsible for signaling in the sympathetic nervous system.
Beta-agonists bind to the beta receptors on various tissues throughout the body.
Beta-1 receptors are predominantly found in three locations: the heart, the kidney, and the fat cells.
How do Beta - 1 adrenergic receptors work ?
The beta-1 adrenergic receptor is a G-protein-coupled receptor communicating through the Gs alpha subunit. By signaling Gs, a cAMP-dependent pathway is initiated through adenylyl cyclase, and this results in potentiation of the receptor’s function.
Where are alpha and beta adrenoreceptors found ?
Both alpha and beta receptors are located on the postsynaptic membrane at the sympathetic junctions.
Both alpha and beta receptors are stimulated by epinephrine and norepinephrine.
Difference between alpha and beta adrenoreceptors ?
Alpha Receptors: Alpha receptors are the cell receptors that control physiological processes like vasoconstriction, intestinal relaxation, pupil dilation upon interaction with epinephrine and norepinephrine.
Beta Receptors: Beta receptors are a group of receptors that control vasodilation, relaxation of the bronchial and uterine smooth muscles, and increased heart rate.
Effect:
Alpha Receptors: Alpha receptors stimulate effector cells.
Beta Receptors: Beta receptors relax effector cells.
Types:
Alpha Receptors: The two types of alpha receptors are alpha 1 and alpha 2.
Beta Receptors: The three types of beta receptors are beta 1, beta 2, and beta 3.
Occurrence:
Alpha Receptors: The two types of alpha receptors are alpha 1 and alpha 2.
Beta Receptors: The three types of beta receptors are beta 1, beta 2, and beta 3.
Muscle stimulation:
Alpha Receptors: Alpha receptors stimulate smooth muscles.
Beta Receptors: Beta receptors stimulate both cardiac and smooth muscles.
Examples:
Alpha Receptors: The stimulation of alpha receptors in the heart constricts blood vessels.
Beta Receptors: The stimulation of beta receptors in the heart increases the heart rate and the strength of contraction.
When does the heart start beating ?
23 days after fertilization
How much blood on average does the heart pump out in a minute ?
5.250 L of blood per min
Describe the layers of the heart ?
Describe sarcomeres in cardiomyocytes ?
Describe the action potential of the SA ?
At what point does the esophagus, aorta and inferior vena cava go through the diaphragm ?
I ate (8) 10 Oreos at 12
Aortic - T8
Oesophagus - T10
Aortic - T12
Describe the internal anatomy of an artery or vein ?
What is the difference between elastic artery. muscular artery and arterioles ?
What are the 3 types of capillaries ?
Describe the structures found in the capillaries ?
- Precapillary sphincters:
A precapillary sphincter is a band of contractile mural cells either classified as smooth muscle or pericytes that adjusts blood flow into capillaries.
- Vascular shunt: A blood vessel that links an artery directly to a vein, allowing the blood to bypass the capillaries in certain areas.
This useful at times when tissues don’t need blood. This is very clever the body can send the blood to where it is needed the most.
Describe how the veins serve as a volume reservoir ?
Describe how the veins serve as a volume reservoir ?
Describe how the arteries act as a pressure reservoir ?
Arteries are low resistance vessels that serve as pressure reservoirs to maintain blood flow during diastole. All arteries have muscular walls. In response to pressure, to paracrines, and to nervous activity, the smooth muscle of the artery can either constrict or relax and thereby change the diameter of the vessel.
Does blood pressure vary ?
Blood pressure is different in blood vessels and varies from minute to minute dependent on factors such as stress.
Describe a blood pressure reading ?
How do you work out the mean arterial pressure (MAP) ?
What aids venous return to the blood ?
What is the difference between Cardiac Output (CO), Stroke Volume and Heart Rate ?
What are the 3 factors stroke volume is determined by ?
Preload:
Preload (End Diastolic Volume)»> the higher the volume, the higher the stroke [Frank-Starling law of the heart]
Factors affecting preload:
- blood volume
- venous return
Afterload:
is the pressure that the ventricles must overcome to eject blood. It is
essentially the back pressure that arterial blood exerts on the aortic and pulmonary valves—about 80 mm Hg in the aorta and 10 mm Hg in the pulmonary trunk
What is catecholamine ?
- A type of neurohormone (a chemical that is made by nerve cells and used to send signals to other cells).
Catecholamines are important in stress responses. High levels cause high blood pressure which can lead to headaches, sweating, pounding of the heart, pain in the chest, and anxiety.
What is catecholamine ?
- A type of neurohormone (a chemical that is made by nerve cells and used to send signals to other cells).
Catecholamines are important in stress responses. High levels cause high blood pressure which can lead to headaches, sweating, pounding of the heart, pain in the chest, and anxiety.
What is hematocrit ?
What is arterial occlusion ?
Acute arterial occlusion is a sudden blockage or closing of one of your peripheral arteries that interrupts blood flow. Healthcare providers also call this condition acute limb ischemia. “Ischemia” means part of your body isn’t receiving enough oxygen-rich blood.
Occlusion can increase blood pressure dramatically.
A 20% occlusion of a healthy artery can increase blood pressure from 120mmHg to 293mmHg.
What happens to blood pressure when you have arteriosclerosis ?
Atherosclerosis is the buildup of fats, cholesterol and other substances in and on the artery walls. This buildup is called plaque. The plaque can cause arteries to narrow, blocking blood flow. The plaque can also burst, leading to a blood clot.
Higher blood pressure, higher chance of bad things happening
How do we generate and maintain our own blood pressure ?
- Dependent on blood flow, change in pressure and resistance.
Statistics about heart ?
What happens during diastole and systole ?
Diastole:
Blood flows from atria to ventricles
Systole:
Blood is ejected from the ventricles
What is the equation to work out blood flow ?
What happens to resistance of blood during exercise ?
- In exercise the body changes the resistance of blood vessels to divert the blood to where it is needed.
If resistance falls blood flow increases
If resistance rises blood flow decreases
We need to remember when resistance is falling so is pressure, we need to increase our cardiac output somehow ?
This is done easily by increasing heart rate. And is the reason why our heart rate increases during exercise.
CO = HR x SV
An increase in cardiac output increases the pressure we can generate and compensates the fall in resistance which is increasing our blood flow.
What happens to blood flow rate when the diameter of a vessel is increased ?
Doubling the diameter (lumen ) of a vessel increases the blood flow rate by 4.
This is shown by Poiseuille’s Law
How do we control local control of blood flow ?
Local control of blood flow is generally controlled though metabolic products of the tissues affecting the vascular bed.
Vasodilation causes:
- So vasodilation can be induced by cytokines when blood vessels are damaged. Nitric oxide is a good example of this.
- High CO2 levels can lead to vasodilation
- This makes sense because if you damage to tissue or vessels, then you need to get inflammatory products circulating the body to that tissue. So you want to increase blood flow to that tissue bed.
-Similarly CO2 is a waste product that is harmful to the body. If you have high concentrations of it in a certain area of the body, increasing vasodilation increases blood flow away.
Vasoconstriction causes:
- Low oxygen: If you have low oxygen levels in the blood you may want to vasoconstrict to divert blood away from areas that is may not be needed to those who do need it eg. heart, brain and major organs
- Acidity
- Potassium and bicarbonate
What is the central control of blood pressure ?
The central control of blood pressure can be split into two categories:
- Autonomic nervous system
- which is driven by the sympathetic nervous system and has a very fast acting effect.
- Endocrine system
- which has various different hormonal pathways
- the endocrine system has a longer term effect than the autonomic nervous system.
What doe the sympathetic fibers do to the vessels ?
Every single blood vessel apart from the capillaries is innervated by the sympathetic nerve.
Describe how sympathetic activation affects blood flow and blood pressure ?
Vasconstriction:
- Increases peripheral resistance which increases blood pressure
- increases venous pressure = increases blood flow back to the heart = increases SV
Increased heart rate:
- increases cardiac output = increases blood pressure
Increased inotropy:
- increases stroke volume = increased cardiac output = increased blood pressure
Increased adrenaline / noradrenaline secretion from adrenal glands:
- Activate alpha - and beta-adrenergic receptors
- Vasoconstriction, increased heart rate, increased inotropy
Pressure = Cardiac output x Resistance
Cardiac output = HR x SV
What causes sympathetic activation to be stimulated ?
Possible causes: exercise, emotional stress, changes in intravascular pressure
Sympathetic reaction is governed by changes in blood pressure itself. Change in blood pressure can cause sympathetic activation or deactivation.
Baroreceptors detect a change in pressure
Arterial baroreceptors (pressure receptors) are found in:
- Aortic arch
- Internal carotid arteries
As the pressure increases the vessels stretch. Baroreceptors detect this stretch. Vascular stretch causes an increase in efferent impulses which activate the sympathetic nervous system. This works in a negative feedback loop.
Describe blood pressure and negative feedback loop?
The process is called Vasomotor tone.
Decreased blood pressure
Decreased firing from baroreceptors
Vasomotor centre in the medulla
Increased sympathetic activation
Increased blood pressure
Detected by baroreceptors when they stretch. Which increases firing from baroreceptors
Send efferent signals to the vasomotor centre in the medulla
This decreases sympathetic activation
Which decreases blood pressure
Why are baroreceptors important ?
Baroreceptors minimise variations in our BP regardless of cause. This is why we do not feel dizzy when we get out of bed in the morning and we do not get severe headaches and blurred vision when we become excited.
How does hypoxia cause high blood pressure ?
Low levels of oxygen, can cause vasoconstriction to divert blood to where it is most needed.
What layer of the embryo contributes to the arteries and cardiac outflow?
The mesoderm
Which layer of the embryo forms the blood and heart?
mesoderm
What does the truncus arteriosis or bulbus cordis do and where is it?
It is at the top of the fused heart tubes and forms the aortic arch and most of the right ventricle
Describe the steps for the embryology of the heart ?
Day 19: precursor cells start to become endocardial tubes.
Day 21: during lateral and cephocaudal folding the two heart tubes fuse into one single primitive tube.
Day 22: the heart begins to beat
Day 23- 28: looping of the heart
Day 28- 46 (approx): septum divide heart into different chambers
How does blood return to the heart from the yolk sac and developing foregut ?
Vitelline veins
What is septum premium ?
Grows from the roof of the atrium towards the endocardial cushions
Where does the right and left horns of sinus venous receive blood from ?
The common cardinal vitelline veins and umbilical veins
What occurs as a result of aortic or pulmonary stenosis ?
Left and right wall ( respectively ) become thickened ( hypertrophied), stenosis ( narrowing) of the valves restricts flow; these together result in a heart murmur
Where do vitelline arteries bring blood to ?
The yolk sac and future gut
Label the primitive heart tube
Truncus arteriosus: aorta, pulmonary trunk
Bulbus cordis: right ventricle ( trabeculated part, proximal), ventricle outflow tracts
Primitive ventricle: left ventricle ( trabeculated part)
Primitive atrium: right and left atrium (anterior parts)
Sinus Venosus: right atrium ( smooth parts )
Which cells form the definitive mitral and tricuspid valves ?
Mesenchymal cells
How does oxygenated blood from the placenta return to the embryos heart ?
Via the umbilical vein
What do the vitelline arteries represent in an adult ?
Celiac, superior and inferior mesenteric arteries
Describe the order of blood flow in the newly formed heart ( pre looping )
From bottom to top: 1. Sinus venosus 2. Primitive atria 3. Primitive ventricle 4. Bulbus cordis 5. Truncus arteriosus 6. Aortic sac 7. Dorsal aorta
Describe the inflow tract of the early embryo ? ( pre looping )
Sinus venous receives paired umbilical, vitelline and common cardinal veins
Which germ layer are the lungs formed from ?
Endoderm layer.
The lungs originate from the ventral aspect of the foregut. This is known as the respiratory diverticulum which later becomes the lung bud
Which week do we get the separation of the trachea and oesophagus (tracheal oesophageal ridge )
The foregut has differentiated into the trachea and oesophagus by week 4
What is the tracheooesphageal fistula ?
Separation of the trachea and oesophagus
Where do the supporting structures of the lung develop from ?
Mesenchyme layer of the mesoderm
Where are the actual lungs derived from and where is the pleura derived from ?
Actual lungs: ectoderm
Pleura: splanchnic mesoderm
Describe the development of the lungs ?
28 days we can see the bronchial buds
35 days we can see the left and right main bronchus
42 days the branching levels will be more complex and proliferate into a, b and c
What are the 5 stages of the lung maturation period?
Embryonic stage ( 3-6 week)
Pseudo glandular stage ( 5-17 week )
Canalicular stage (16-25 week )
Terminal sac / saccular stage ( 24 weeks until birth)
Alveolar stage ( 36 weeks - 8years )
Describe the embryonic stage of lung development ( 3-6 weeks) ?
- respiratory diverticulum appears on the foregut
- caudal end of trachea bifurcate into the left and right bronchial buds which continue to grow into the adjacent layer of splanchnic mesoderm derived pleural mesenchyme
- at the end of the 5th week- the primary bronchial buds divide asymmetrically to form the secondary bronchial buds. 2 on the left and 3 on the right , which will give rise to future lobes
The left renal artery leaves the aorta at what point ?
The testicular and ovarian arteries leave the aorta at what point ?
- L1
- L2
What is the bifurcation point of the abdominal aorta ?
L4: bifurcation of the abdominal aorta
Describe the arteries stemming off the brachiocephalic trunk and right subclavian artery ?
Where does the right internal and external carotid artery lie ?
Common carotid arteries on a cadaver ?
Facial artery and superficial temporal artery ?
Branches of left common carotid artery and left subclavian artery ?
What are the branches of the descending aorta ?
What are the branches of the inferior vena cava ?
What are the branches of the superior vena cava ?
Where does the descending thoracic aorta run from ?
T4 to T12
Where does the abdominal aorta run from ?
Starts at T12 and bifurcates at L4 into the right and left common iliac arteries.
How does the inferior vena cava arise ?
The left and right common iliac veins arising as the anastomosis (joining) of the external and
internal iliac veins on either side.
The inferior vena cava (formed by the anastomosis of the right and left common iliac veins the level
of L5 – runs on right side of vertebral column – is partially embedded in the liver before passing
through the caval opening of the diaphragm at T8, and entering the right atrium)
Renal veins - L1
Gonadal veins - L2
Where does deoxygenated blood from the superior vena cava come from ?
Where does blood draining into the azygous vein come from ?
The superior vena cava is formed by the
union of the brachiocephalic veins
Veins
Right internal jugular and left internal jugular
External and internal iliac arteries ?
External and internal iliac veins ?
IMPORTANT
The inferior vena cava runs alongside the side of the abdominal aorta
- Below the kidneys we have the inferior mesenteric artery.
Iliac arteries and veins
What does the external iliac artery supply ?
What does the internal iliac artery supply ?
The external iliac artery changes name to the femoral artery
The femoral artery, femoral vein and femoral nerve run alongside each other.
What is the popliteal fossa ?
The Popliteal Fossa is a diamond-shaped space behind the knee joint. It is formed between the muscles in the posterior compartments of the thigh and leg. This anatomical landmark is the major route by which structures pass between the thigh and leg.
The popliteal artery passes through the popliteal fossa and ends at the lower border of the popliteus muscle, where it branches into its two terminal branches; the anterior and posterior tibial arteries.
Posterior and anterior tibial artery ?
What are the branches of the coeiliac / celiac trunk ?
Celiac trunk arises from the aorta at T12. It’s branches are the splenic artery , hepatic artery and the left gastric artery
Where does the left testicular vein drain into ?
Left and right testes are drained by the left and right testicular/gonadal vein respectively. The right testicular vein drains directly into the inferior vena cava, while the left testicular vein drains into the left renal vein which then drains into the inferior vena cava.
