Cardiovascular system TRI 2 Flashcards
right side
recieves oxygen- pour blood from tissues
pumps blood to lungs to get rid of CO2, pick up O2, via pulmonary circuit
left side
recieves oxyganted blood from lungs
pumps blood to body tissues via systemic circuit
recieving chambers of heart
right atrium
left atrium
left atrium
recieves bloof returning from pulmonary circuit
right atrium
recievs blood returning from systemic cirucit
pumping chambers of heart
right ventricle
left ventricle
right ventricle
pumps blood through pulmonary circuit
left ventricle
pumps blood through systemic circuit
pericardium
double walled sac that surrounds the heart
made of 2 layers:
fibrous pericardium
seroud pericardium
fibrous pericardium
functions to protect, anchor heart to surrounding structures, and prevent overfilling
serous pericardium
has 2 layers:
parietal layer
visceral layer
two layers separated by pericardial cavity
parietal layer
lines interanl surface of fibroud pericardium
visceral layer
on external surface of heart
how many layers of heart wall, what are they?
3
epicardium
myocardium
endocardium
epicardium
visceral layer of serous pericardium
myocardium
circular or spiral bundles of contricle cardiac muscle cells
endocardium
innermost layer
is continous with endothelial lining of blood vessels
lines heart chambers
Function of Blood Vessels
delivery system of dynamic structures that begins and ends at the heart
Function of arteries
carry blood away from heart, oxygenated except for pulmonary circulation
Function of capillaries
direct contact with tissue/cells
directly serve cellular needs
Function of veins
carry blood towards heart
deoxygenated except for pulmonary circulation
What factors contribute to an increase in cardiac output during exercise?
Increased sympathetic activity
Increased skeletal muscle and respiratory pumps
Increased venous return
Increased contractility
Decreased parasympathetic activity
Increased heart rate (HR)
Increased stroke volume (SV)
CO = SV × HR
What are the key differences between pulmonary and systemic circulation?
Pulmonary Circuit: Carries oxygen-poor blood from the right ventricle to the lungs and back to the left atrium.
Systemic Circuit: Carries oxygen-rich blood from the left ventricle to the body and returns oxygen-poor blood to the right atrium.
Describe the pathway of blood flow through the heart.
Right atrium → Tricuspid valve → Right ventricle
Right ventricle → Pulmonary semilunar valve → Pulmonary arteries → Lungs
Lungs → Pulmonary veins → Left atrium
Left atrium → Bicuspid (mitral) valve → Left ventricle
Left ventricle → Aortic semilunar valve → Aorta → Body
What happens to aortic pressure, ventricular pressure, and the electrocardiogram (ECG) during the cardiac cycle?
Aortic Pressure: Rises during ventricular systole, falls during diastole.
Ventricular Pressure: Rapid increase during systole, then decreases during relaxation.
ECG Waves:
P wave: Atrial depolarization
QRS complex: Ventricular depolarization
T wave: Ventricular repolarization
What is the function of venues?
Small veins collecting blood from capillaries
What are the three layers (tunics) of blood vessel walls?
Tunica intima
Tunica media
Tunica externa
Tunica intima
innermost layer of blood vessels.
Composed of endothelium, a simple squamous epithelium.
Functions:
Provides a smooth, low-resistance surface for blood flow.
Continuous with the endocardium of the heart.
Tunica media
Middle layer
Composed of smooth muscle, collagen, and elastin.
Controlled by sympathetic vasomotor nerves:
Vasoconstriction: Narrows lumen, increases blood pressure.
Vasodilation: Widens lumen, decreases blood pressure.
Tunica externa
Outer layer
Composed of collagen fibers that protect and reinforce vessels.
Contains nerve fibers, lymphatic vessels, and elastic fibers (in large veins).
Includes vasa vasorum, a network of tiny blood vessels that supply larger vessels.
How does the lymphatic system interact with blood vessels?
Collects excess interstitial fluid and returns it to circulation.
Contains lymph nodes to filter pathogens.
Works alongside venous system to maintain fluid balance.
What are the three types of arteries?
Elastic arteries
Muscular arteries
Arterioles
Elastic arteries
Thick-walled, low-resistance lumen.
Conduct blood from the heart to medium-sized arteries.
Contain elastin in all three tunics.
Act as pressure reservoirs.
Muscular arteries
Deliver blood to organs.
Thickest tunica media with smooth muscle.
Actively control blood pressure and flow.
Arterioles
Smallest arteries.
Control resistance to blood flow via vasoconstriction/vasodilation.
Feature of Arteries
Wall thickness- thick
Lumen size- Narrow
Tunica Media- thick with smooth muscl e
No valves
Features of veins
Wall thickness- thin
Lumen size- wide
Tunica media- thin
Valves- present in larger veins
Features in capillaries
Wall thickness- one cell thick
Lumen size- very small
No tunica media
No valves
What is atherosclerosis, and how does it affect arteries?
A condition where plaque (lipids, calcium, cellular debris) builds up in arteries.
Leads to:
Narrowing of arteries.
Reduced blood flow.
Increased risk of heart attack or stroke.
Plaque can rupture, causing blood clots.
What are capillary beds, and what is their function?
A network of capillaries between arterioles and venules
Facilitates the exchange of gases, nutrients, and waste between blood and tissues.
Microcirculation: Blood flow through the capillary bed
What are the two types of vessels in capillary beds?
Vascular shunt
True capillaries
Vascular shunt
A direct passage for blood between arteriole and venule
True capillaries
Exchange vessels that’s branch from the metarteriole
What structures make up the vascular shunt?
Terminal Arteriole
Metarteriole
Thoroughfare channel
Postcapillary venule
Terminal arteriole
Feeds blood into the capillary bed
Metarteriole
Intermediate vessel between Arterioles and capillary
Thoroughfare channel
Intermediate vessel between capillary and venule
Postcapillary venule
Drains the capillary bed
How is blood flow through true capillaries regulated?
Precapillary sphincters control whether blood enters the true capillaries or bypasses via the vascular shunt.
Regulated by local chemical conditions and vasomotor nerves.
What forces regulate fluid movement in and out of capillaries?
Blood hydrostatic pressure
Blood colloid osmotic pressure
Interstitial fluid hydrostatic pressure
Interstitial fluid osmotic pressure
Blood hydrostatic pressure
Pushes fluid out of capillaries
Blood colloid osmotic pressure
Pulls fluid into capillaries
Interstitial fluid hydrostatic pressure
Pushes fluid into capillaries
Interstitial fluid osmotic pressure
Pulls fluid out of capillaries
How do veins differ from arteries, and what adaptations help return blood to the heart?
Lower blood pressure than arteries.
Large-diameter lumens → Offer little resistance.
Venous valves:
Prevent backflow of blood.
Most abundant in veins of the limbs.
What are varicose veins, and what causes them?
Dilated, painful veins due to incompetent (leaky) valves.
Caused by:
Prolonged standing.
Obesity.
Pregnancy.
Genetic factors.
What is blood flow, and how is it measured?
The volume of blood moving through a vessel (ml/min).
Equivalent to cardiac output (CO) for the entire vascular system.
Constant at rest but varies in different organs based on needs.
What is blood pressure (BP), and how is it measured?
Force per unit area exerted by blood on vessel walls.
Measured in mmHg (millimeters of mercury).
Systemic arterial BP is taken from large arteries near the heart.
Pressure gradient:
Drives blood flow from higher to lower pressure areas
What is resistance in blood flow, and what factors affect it?
Opposition to flow due to friction.
Three main factors:
Blood viscosity: Thicker blood = more resistance.
Total blood vessel length: Longer vessels = more resistance.
Blood vessel diameter: Smaller diameter = higher resistance
How do blood viscosity and vessel length affect resistance?
The thickness/stickiness of blood due to cells and proteins.
Higher viscosity = increased resistance
Longer vessel = more resistance to blood flow.
Why is blood vessel diameter the most important factor in resistance?
Resistance varies inversely with the fourth power of the vessel’s radius.
If radius doubles, resistance drops to 1/16.
If radius halves, resistance increases 16-fold.
How does systemic blood pressure change throughout circulation?
Highest in the aorta.
Declines progressively as blood moves through arteries, capillaries, veins.
Steepest drop occurs in arterioles (major resistance vessels)
What are systolic, diastolic, and mean pressures in blood vessels?
Systolic pressure: Highest pressure during heart contraction.
Diastolic pressure: Lowest pressure during heart relaxation.
Mean arterial pressure (MAP):
MAP ≈ Diastolic pressure + (1/3 × Pulse pressure)
What two factors determine arterial blood pressure?
Elasticity (compliance or distensibility) of arteries close to the heart.
Volume of blood forced into arteries at any time
Pulsation nature
Blood pressure rises and falls with each heartbeat
What is systolic pressure?
Pressure exerted in the aorta during ventricular contraction.
Left ventricle pumps blood into the aorta.
Normal adult average: 120 mmHg.
What is Diastolic pressure?
Lowest aortic pressure when the heart is at rest.
Normal adult average: 80 mmHg.
What is pulse pressure?
Difference between systolic and diastolic pressure (120 – 80 = 40 mmHg).
What is a pulse?
Throbbing of arteries due to pressure fluctuations.
Can be felt under the skin.
Why is low capillary pressure beneficial?
High BP would rupture thin-walled capillaries.
Most capillaries are very permeable, allowing adequate exchange at low pressure.
How does venous blood pressure compare to arterial pressure?
Much lower than arterial pressure
If vein is cut, blood flows out smoothly.
If artery is cut, blood spurts due to higher pressure.
How does blood pressure change throughout circulation?
Highest in the aorta (~120 mmHg).
Falls across arteries, arterioles, capillaries, venules, and veins.
Steepest drop occurs in arterioles, due to increased resistance.
Venous pressure is lowest (near 0 mmHg in vena cava).
What are the three mechanisms aiding venous return?
Muscular pump
Respiratory pump
Sympathetic venoconstriction
Muscular pump
Skeletal muscle contractions “milk” blood back to the heart; valves prevent backflow.
Respiratory pump
Breathing squeezes abdominal veins, drawing blood toward the heart.
Sympathetic venoconstriction
Smooth muscle constriction under sympathetic control pushes blood back to the heart.
What are the three main factors regulating blood pressure?
Cardiac output
Peripheral resistance
Blood volume
What are the main mechanisms that regulate blood pressure?
Short term regulation:
Neural controls
Hormonal controls
Long term regulation:
Renal controls
What factors influence Mean Arterial Pressure (MAP)?
Cardiac output which in increased by higher stroke volume and increased heart rate
Peripheral resistance which is increased by smaller vessel diameter, higher blood viscosity and longer blood vessel length
How do neural mechanisms regulate blood pressure?
Vessel diameter regulation
Blood distribution adjustment
Vessel diameter regulation
If blood volume drops, all vessels constrict to maintain pressure.
Blood distribution adjustment
Blood is directed to organs based on demand (e.g., muscles during exercise).
What are the key components of the neural reflex arc that controls blood pressure?
Cardiovascular center of the medulla – Regulates heart rate and vessel tone.
Baroreceptors – Detect pressure changes.
Chemoreceptors – Respond to changes in oxygen, CO₂, and pH.
Higher brain centers – Influence BP during stress or emotions.
How do baroreceptors regulate high blood pressure?
Baroreceptors in the carotid sinus and aortic arch are stimulated
Signals sent to inhibit the vasomotor center
Vasodilation and reduced cardiac output therefore BP decreases.
How do baroreceptors regulate low blood pressure?
Baroreceptors are inhibited
Signals activate the vasomotor center
Vasoconstriction and increased cardiac output therefore BP rises.
What hormones influence blood pressure, and how?
Epinephrine/Norepinephrine – Increases HR and contractility (↑ BP).
Angiotensin II – Causes vasoconstriction (↑ BP).
Atrial Natriuretic Peptide (ANP) – Promotes vasodilation (↓ BP).
Antidiuretic Hormone (ADH) – Retains water, increasing blood volume (↑ BP).
Aldosterone – Increases salt retention, leading to higher blood volume (↑ BP).
How do the kidneys regulate long-term blood pressure?
Direct mechanism
Indirect mechanism
Direct mechanism
If BP is high, kidneys increase urine output, lowering blood volume and BP.
Indirect mechanism
Renin- Angiotensin- Aldosterone system (RAAS)
Low BP triggers renin release
Converts angiotensinogen to angiotensin I
Converted to angiotensin II
Causes vasoconstriction and stimulates aldosterone and ADH → BP rises.
What are the effects of angiotensin II in blood pressure regulation?
Vasoconstriction → Increases peripheral resistance → Raises BP.
Stimulating ADH release → Promotes water retention in kidneys.
Triggering thirst (via hypothalamus) → Increases water intake.
Stimulating aldosterone release from adrenal cortex → Increases Na⁺ and water reabsorption → Raises blood volume and BP.
How does aldosterone affect blood pressure?
Increases sodium (Na⁺) reabsorption in kidney tubules.
Water follows Na⁺, leading to increased blood volume.
Higher blood volume leads to higher BP.
How does ADH help regulate blood pressure?
ADH (vasopressin) is released from the posterior pituitary when:
BP drops
Osmolarity increases (dehydration)
Effects of ADH
Increases water reabsorption in kidneys
Reduces urine output, conserving water
Increase blood volume, raising BP
