Flashcards in CVS- 1 and 2 Deck (82):
How to single celled organisms obtain O2 and nutrients?
Why is diffusion not efficient in larger organisms?
Would take too long to obtain nutrients so they need a gas exchange and circulatory system
How does the CVS work?
A mechanism that transporting substances close to the cells to allow diffusion to take place.
How does blood exchange oxygen and nutrients with cells?
Diffusion - the CVS provides the correct conditions for diffusion to occur at tissues and lungs.
Where does diffusion take place? What are the type of cells and what are they surrounded by?
Capillaries - single endothelial cells surrounded by basal lamina
What molecules can diffuse directly through the bilayer? (2)
Oxygen and Carbon dioxide
How do large molecules such as glucose, amino acids and lactate (water soluble molecules) diffuse into capillaries?
Through pores in the capillaries.
What effects the rate of diffusion? (3)
Explain how they effect the rate.
Area - determined by how many capillaries per unit volume (capillary density). Large area = greater diffusion. Tissues that are more metabolically active have more capillaries.
Diffusion Resistance - nature of molecule (large molecule = slower), nature of barrier (hydrophillic diffuse more readily if there's pores) and path length (Shortest path = greatest diffusion).
Concentration gradient - greater gradient = greater diffusion
What must be maintained for diffusion to continue?
If there is a lower blood flow, would there be an increase or decrease in the number of capillaries?
Decrease - lower capillary concentration
What is the rate of blood flow called?
What is the blood flow at rest in litres.min-1?
What is the blood flow to the brain, heart and kidneys? And describe the flow?
Brain 0.5ml min -1 g-1 (High, constant flow)
Heart 0.9 to 3.6 ml min-1 g-1 (High flow, increases with exercise)
Kidneys 3.5ml min-1 g-1 (High, constant flow)
What is the rate of blood flow during exercise in l.min-1?
What four components make up the CVS?
Pump = heart
Distribution system = vessels and blood
Exchange mechanism = capillaries
Flow control = arterioles and pre capillary sphincters
What are the resistance vessels in the CVS?
Arterioles and pre capillary sphincters
What does blood flow through when it leaves the heart?
Heart - arteries - arterioles - capillaries - venules - veins - heart
Where is the temporary store of blood kept? And why?
Veins - thin walls, easily distend/collapse, act as a variable reservoir.
Why does the body require a temporary blood store?
What is the store of blood called?
To meet the requirements of the body, blood flow is flexible
What store of blood is kept in the veins, heart, arteries/arterioles and capillaries?
Veins = 67%
Heart = 17%
Artery/arterioles = 11%
Capillaries = 5%
When does blood flow fastest, when cross sectional is at greatest or least?
In what vessels does blood flow fastest and slowest?
Cross section is least
Fastest = Aorta
Slowest = Capillaries
What are the three major arterial trunks?
Left common carotid artery
Left subclavian artery
What happens to blood pressure in systole? And what part of the heart causes this change?
Blood pressure rises (120mmHg) due to the left ventricle contracting
What happens in diastole? (4)
Aortic semilunar valve closes
Walls of aorta recoil
Blood pressure maintained - moves towards smaller vessels
Aortic pressure drops (70-80mmHg)
What are the three layers of the arteries and veins from inside out?
Describe the tunica media of the large elastic arteries?
40-70 fenestrated elastic membranes, smooth muscle cells and collagen between lamellae
What is the vasa vasorum?
A network of small blood vessels that supply large blood vessels
What makes up the tunica adventitia in elastic and muscular arteries?
Thin fibroelastic connective tissue containing;
Describe the tunica media of muscular arteries?
40 smooth muscle cells connected by gap junctions for coordinated contraction
What are end arteries?
Terminal artery supplying all or most of the blood to a body part. Undergo progressive branching without development of channels connecting other arteries
Give 4 examples of end arteries.
Main examples = Coronary artery, Splenic artery, Renal artery
Anatomically true = Central artery to retina, Artery of inner ear
What is bridging?
Compression of segment of coronary artery during systole resulting in the narrowing that reverses during diastole
How many layers of smooth muscle do arterioles have in their tunica media?
1 to 3 layers of smooth muscle
What are metaarterioles?
Arteries that supply blood to capillary beds
What is the characteristic of smooth muscle in metaarterioles?
Smooth muscle is not continuous. Individual muscle cells are spaced apart, each encircles endothelium of capillary arising from metaarteriole
What is a pre capillary sphincter?
A band of smooth muscle that adjusts flow into capillaries.
Open= plentiful supply
Closed = decreased supply
What is the role of the lymphatic capillaries?
To drain away excess ECF returning it to the blood at junctions of internal jugular and subclavian veins.
By how much can metaarterioles dilate?
40-60% of resting diameter.
Can maintain contraction for up to 40%.
During exercise, what happens to blood? Where does it flow and how?
Skeletal muscle flow increases, dilation of arterioles.
The Gut flow decreases by constriction of arteries.
What makes capillaries suitable for nutrient and gaseous exchange?
Large surface area
Where is blood flow at its lowest velocity and why?
Capillaries - to allow time for gas exchange
What is the diameter of a capillary?
7 - 10 micrometres
What are the three types of capillaries?
Sinusodial or discontinuous
What are the most common capillaries? Where are they found?
Found in nerves, muscle, connective tissue, exocrine glands and lungs
What are fenestrated capillaries and where are they found?
Interruptions (pores) exist across thin parts of the endothelium, bridged by thin diaphragm
Gut, endocrine glands and renal glomerulus
What are sinusodial/discontinuous capillaries and where are they found?
Capillaries that have a larger diameter and slower blood flow. Gaps in the walls allowing whole cells to move between blood and tissue.
Found in the liver, spleen and bone marrow
What are pericytes?
Branching network on outer space of endothelium. Capable of dividing into muscle cells, fibroblasts. Found in tumour growth and wound healing.
What are more permeable than capillaries and have lower pressure?
Post capillary venules
Lower pressure - blood drains into them except in an inflammatory response.
What is the diameter of a post capillary venule?
What is the diameter of a capillary?
7- 10 micrometre
Describe a venule.
Endothelium assocaited with pericytes/smooth muscle to form thin walls. Can have valves.
NO valves - thoracic and abdo cavity
Describe a vein. Diameter, connective tissue and elastic/muscle fibres?
Larger diameter than artery and thinner wall
More connective tissue and fewer elastic/muscle fibres
Is the tunic intima and media, thick or thin in small and medium sized veins?
Thin tunica intima and media. Well developed adventitia
Name 4 examples of large veins
What is the function of valves?
They act with muscle contraction to propel the blood towards the heart
What are venae comitantes? Give examples.
Deep paired veins that accompany one of the smaller arteries on each side of the artery.
Three vessels wrapped in one sheath
Pulsing of artery promotes venous return within adjacent, parallel and paired veins
Examples = brachial, ulnar, tibial
Why do we need a CVS?
All cells are metabolically active
CVS carry oxygen and nutrients to cells and waste products away
What is a pericardial effusion?
Abnormal amount of fluid between the heart and pericardium
What can cause a Pericardium Effusion?
Inflammation of the pericardium called pericarditis.
Viral infections are one of the main cases of pericarditis and pericardial effusions.
Injury to pericardium or heart
Uraemia - severe kidney disease
Autoimmune disease - lupus, RA
Bacterial infections e.g. TB
What are the symptoms of pericardial effusion?
Chest pain - main symptom. Maybe made worse by deep breathing and lessened by leaning forward
How would you diagnose a pericardial effusion?
Physical examination - occasionally hear abnormal sounds over the heart
What is the treatment for a pericardial effusion?
Treatment depends on severity and cause.
Nonsteroidal anti inflammatory drugs (NSAIDs)
Severe infection (cardiac tamponade) - pericardial effusion must be drained urgently
What is pericardiocentesis?
Drainage of a pericardial effusion by inserting a needle through the chest into the pericardial effusion. A catheter is advanced into the fluid and the pericardial effusion is sucked out.
What is cardiac tamponade?
Inflammation of the pericardium can lead to a large build up of fluid inside the pericardium. The extra fluid puts the heart under pressure, which makes it unable to pump blood around the body effectively.
How is cardiac tamponade treated?
It is life threatening. Symptoms can develop very quickly.
What are the four main roles of the pericardium?
Fixes the heart - in the mediastinum and limits its motion due to attachment to the diaphragm, the sternum and tunica adventitia of the great vessels
Prevents overfilling - prevents heart from increasing in size too rapidly, thus placing physical limit on the potential size of the organ
Lubrication - thin film of fluid between two layers of the serious pericardium reduces the friction generated by the heart as it moves in the thoracic cavity
Protection from infection - physical barrier between the muscular body of the heart and adjacent organs
What is the pericardium?
A fibroserous fluid filled sac that surrounds the muscular body of the heart and roots of the great vessels.
What are the 4 great vessels?
Vena Cava - superior/inferior
What nerve runs over the heart?
C3, 4 and 5 - keep you alive!
Name the two layers of the pericardium
Fibrous pericardium - tough connective tissue. Rigidity prevents overfilling of the heart
Serous pericardium - thin, internal layer
What are the layers of the pericardium from outside to inside?
Parietal layer of serous pericardium
Visceral layer of serous pericardium - forms outer layer of the heart
Fart Police Smell Villians - Acronym
What does the pericardial cavity contain? And why?
Small amount of lubricating fluid to minimise the friction generated by the heart as it contracts and moves about within the thoracic cavity.
What are the three layers of the heart? (Inside to outside)
Middle layer of the myocardium
How are the cardiac muscle fibres attached to the epicardium?
Bundles of collagen fibres
List three features of purkinje fibres
Rich in glycogen
Relatively few myofibrils
Where is the pacemaker of the heart located (sinus node)?
Upper part of the wall of the right atrium. Electrical impulses are generated there
What makes up the tunica intima?
Simple squamous epilthelial cells
endothelium resting on a connective tissue later.
Where does the heart lie?
What is the course of blood through the heart?
Enters through the inferior and superior vena cava, empties deoxygenated blood into the right atrium
Right atrium contracts pushing blood into right ventricle through tricuspid valve
When the ventricle is full, valve closes.
Blood leaves the heart through the pulmonary artery and goes to the lungs to become oxygenated.
Pulmonary vein empties oxygenated blood into left atrium
Left atrium contracts, pushes to left ventricle
When the left ventricle is full, mitral valve closes.
Blood leaves the heart through the aortic valve into the aorta and the body
What is the coronary sinus?
A collection of veins joined together to form a large vessel that collects blood from the heart muscle. It delivers deoxygenated blood to the right atrium as do the superior/inferior vena cava.
Where does the heart receive a blood supply from?
The coronary arteries. Two major coronary arteries branch off the aorta near the point where the aorta and left ventricle meet. These arteries and their branches supply all parts of the heart muscle with blood
What are the major branches of the right coronary artery?
Right marginal artery
Posterior descending artery