14-09-22 - Circulation of Blood Flashcards
Learning outcomes
• To recognise the basic anatomy and the function of the major components of the CVS, including the heart (including valves), arteries, veins and microcirculation.
• To identify which body systems the CVS integrates with, and how secondary nervous and hormonal elements control the function of the CVS.
• To describe the normal distribution and flow of blood through the pulmonary and systemic circulations.
• To compare the features of myocardial muscle with skeletal muscle.
What are 5 functions of the cardiovascular system?
• Functions of the CV system:
1) Bulk flow of materials e.g gas, nutrients, hormones, waste
2) Temperature regulation
3) Homeostasis
4) Host defence
5) Reproduction
What function does the CNS have in relation to the CVS system?
What function does the sympathetic and parasympathetic nervous system have on the CVS system?
• The CNS integrates overall activity of the CVS with the activity and functions of the respiratory and renal systems
Why is the wall of the left ventricle thicker than the right ventricle?
Describe the route of blood through the pulmonary and systemic circulation (in picture).
What is the total blood volume in the body?
How much blood is pumped through the body at rest?
How are blood vessels arranged in parallel?
What are 3 reasons why parallel arrangement of blood vessels important?
Why do both sides of the heart need to contract at the same time?
• The wall of the left ventricle is thicker than the right wall because the left side pumps to the whole body, while the right side only pumps to the lungs
• The total blood volume in the body is 5 litres
• About 5 litres of blood is pumped through the body per minute at rest (entire body blood volume every minute)
• Blood vessels are arranged in parallel through having capillary beds that branch at different organs
• Parallel arrangement of blood vessels is important because:
1) Can have more or less blood flow to a particular organ
2) If an organ gets blocked, it doesn’t compromise the entire blood flow
3) Allows adaptations to the metabolic demands of tissues e.x sweating or exercise may need to increase volume and rate of blood flow
• Both sides of the heart contract at the same time to prevent a build-up of blood in the blood vessels, which can lead to heart failure
What are all blood vessels lined by?
What are the 4 functions of these cells?
What are factors blood vessels may vary in?
What are 3 major differences between arteries and veins?
• All blood vessels are lined by endothelial cells
• 4 functions of endothelial cells:
1) Filtration of fluids
2) Blood vessel size regulation
3) Haemostasis – process to prevent and stop bleeding
4) Transport of substances throughout the body
• Blood vessels may vary in:
1) Number
2) Diameter
3) Wall thickness
4) Smooth muscle
5) Elastic tissue
6) Fibrous tissue
• The lumen of veins is significantly larger than arteries because veins carry a greater volume of blood than arteries
• Arteries (particularly muscular arteries) contain significantly more smooth muscle and veins contain more collagen and elastic fibres.
• This is due to arteries (especially muscular arteries) handling blood at higher pressure than veins, and veins carrying a greater volume of blood
What 4 structures are part of microcirculation?
What are features of each?
What is the blood flow in ml/min through different organs?
• Microcirculation:
1) Arterioles
• Smallest diameter muscular walled arteries
2) Precapillary sphincters
• Rings of smooth muscle which control entry of blood from arterioles into each capillary
• No capillary is constantly filled, otherwise all the blood in the body would be in the capillaries
• Precapillary sphincters prevent this
3) Capillaries
• Smallest diameter blood vessel
• Simple tube, one cell thick, of flattened endothelial cells
• Allows for diffusion of nutrients, waste etc in and out of tissues
• About 10 billion capillaries
4) Venules
• Small diameter vessels which drain blood back to the larger true veins
Label these heart structures
What are the 2 atrioventricular valves?
How do the valves close?
What do these valves attach to?
What is the role of the chorda tendinea?
• The atrioventricular (cuspid) valves:
1) Tricuspid valve (3 semi-lunar cusps)
• Between the right atrium and right ventricle
2) Mitral (bicuspid valve – 2 semi-circular cusps)
• Between the left atrium and left ventricle
• These valves are fairly flimsy
• Blood comes into the ventricle from the atria
• When the ventricle contracts, it pushes blood back against the valves and closes them due to the change in pressure
• They are attached to chordae tendinea, which don’t close the valves, but keep the valves closed (prevent prolapse during systole)
What are the 2 semi-lunar valves?
How strong are these valves compared to atrioventricular valves?
How do these valves close?
• 2 semi-lunar valves:
1) Aortic valve (3 semi-lunar cusps)
• Between left ventricle and aorta
2) Pulmonary valve (3 semi-lunar cusps)
• Between the right ventricle and pulmonary trunk
• These valves are heavy duty then the atrioventricular valves
• The tri-cuspid valves have smaller openings, higher pressure, therefore have more stress and physical abrasion
• The rigidity of these semi-lunar valves is what helps keep them closed
What is an echocardiogram?
• An echocardiogram (or echo) is a scan used to look at the heart and nearby vessels
• It is an ultrasound of the heart
What is the structure of cardiac cells?
How are they connected together?
What do these intercalated disks contain?
How do these structures allow functional syncytium?
What is functional syncytium?
What does functional syncytium allow the heart to do?
• Structure of cardiac cells:
• Cardiac muscle cells branch into a network
• Cardiac cells are connected together by desmosomes at the junction between cells, which gives strong cell to cell adhesion and forms intercalated disks
• These intercalated disks also contain gap junctions
• The gap junctions directly connect the cytoplasm of muscle cells and permit the easy transfer of ions between cells, meaning the cells are electrically connected, which produces a functional syncytium
• A functional syncytium is a unit of contraction comprised of a network of electrically connected cardiac muscle cells.
• Functional syncytium allows the heart to work as a unit and provides synchronous (occurring at the same time) contraction of the heart cells
• This means if an electrical event (via the SA node) depolarises the cells in one region of the heart, it will spread over the whole heart
What are features of the cardiac muscle?
• Features of the cardiac muscle:
• Striated muscle similar to skeletal muscle
• Composed of thick and thin filaments of myosin and actin
• Cardiac muscle contains smaller fibres with individual nuclei
What is the function of about 1% of cardiac fibres?
What is the intrinsic pacemaker of the heart?
How does autonomic innervation (sympathetic and parasympathetics) affect depolarisation of the heart?
• Approximately 1% of cardiac fibres don’t contract, but form excitatory and conductive muscle fibres
• The Sinoatrial node (SAN) is the intrinsic pacemaker of the heart, but other areas have pacemaker activity
• Sympathetic nerves increase the rate of SAN depolarisation (fight or flight)
• The excitability of all portions of the heart is increased by sympathetic stimulation, reducing conduction time.
• Parasympathetic nerves decrease the rate of SAN depolarisation (rest and digest)
• The excitability of AV junctional tissue is lowered by parasympathetic stimulation, slowing transmission of the pacemaker impulse to the ventricles.
