Vertebrate heart structure and function Flashcards
Why do animals need a circulatory system?
- O2, nutrients must be transported around the body to tissues and organs
- waste products removed
- communication via hormones
- temperature regulation & reproduction
Open circulatory system
- Blood flows freely with body cavities making direct contact with all tissues and organs
- vessels are open ended - blood flows out and bathes tissue
Closed circulatory system
- circulating blood contained in a continuous series of vessels
- specific components of the fluid filter out of blood vessel and penetrate tissues
- blood kept separate to interstitial fluid
What are the advantages of a closed circulatory system?
- faster, more efficient delivery of fluid to tissues
- ability to control distribution
- assists in the delivery of larger molecules to specific tissue
- enabled the evolution of circulatory system that keeps oxygenated and deoxygenated blood separate
Fish heart structure
- one atrium and one ventricle, one circulation
- specialisation of vessels (Arteries and veins)
- Blood pumped over gills to become oxygenated but leaves under very low pressures
- very low pressure in capillary bed - limits efficiency of delivery of nutrients and O2 to tissues
Air-breathing fish hearts
- 2 circulations (pulmonary and systemic)
- partially divided atrium and ventricle
- oxygenated (right) and deoxygenated (left) blood is kept separate
- Gill specialisation:
- low-resistance by-pass to lung
- direct link to aorta
Amphibians (i.e. frog) hearts
- 3 chambered heart
- Left atrium - oxygenated blood, right atrium - deoxygenated blood
- single ventricle - potential for some mixing of blood but septum directs blood movements and maintain separation
- partial separation of pulmonary and systemic circuits allow for different pressures
What are the similarities of a closed and open circulatory system?
• hearts pump the fluid to different regions of the body via blood vessels
• fluid drains back to the heart
- via veins for closed
- via ostia (openings) for open system (Act as valves)
• Valves ensure one-way flow of fluid
What is the bulbus arteriosus in fish hearts?
• In teleosts
• elastic
• works to reduce extreme pulsing of blood leaving the ventricle, giving a more constant, even flow
(like water passing through a balloon)
What is the Sinus venosus in fish hearts?
Preliminary collecting chamber
What does the septum do in amphibian hearts?
Directs blood movement & maintains separation of oxygenated and deoxygenated blood
Reptiles heart structure
• 3/4 chambered hearts
• 2 aortae
Left: oxygenated blood from left ventricle to body
Right: mixed - receives blood from both ventricles
• reptiles dont always breathe - blood by-passes lungs and flows directly to the systemic circuit via the right aorta
• direction of blood is controlled by resistance in the pulmonary circuit
Birds and Mammal heart structure
- 4 chambered heart
* separate pulmonary and systemic circuits
What are the advantaged of having separate pulmonary and systemic circuits?
- pulmonary and systemic circuits can operate at different pressures
- systemic circuit always receives blood with higher O2 content
- gas exchange is maximised
What change occur in the heart immediately after birth?
• fetal heart: foramen ovale and ductus arteriosus is open
In the newborn heart, both these structures are closed
What is Atrial Septal Defect (ASD)
- Hole in the septum
- congenital
- deoxygenated and oxygenated blood mix and the heart does not work efficiently
- shortness of breath, fainting, irregular heart rhythm and fatigue after regular activity
- no treatment - surgery needed
What is the septum?
Muscle wall between atria
Define congenital
Present at birth
Difference between arteries and veins
- Arteries: carry blood away from the heart
* veins: return blood to the heart
What are the 4 main valves in the human heart and where are they found?
- Tricuspid valve - right
- bicuspid valve - left
- Aortic semilunar valve - aorta
- pulmonary semilunar valve - pulmonary artery
Briefly describe the blood flow through a mammalian heart
DEOXYGENATED
• from the body, enters via the vena cava to the right atrium, to right ventricle
• passes pulmonary valve and through pulmonary artery to the lungs
GETS OXYGENATED
• through pulmonary vein to left atrium
• through atrioventricular valves to left ventricle
• passes aortic valve and through aorta to the body
Summarise the blood flow of the mammalian heart
DEOXYGENATED (from body)
• vena cava, into right atrium
• pulmonary artery to lung
OXYGENATED
• lung to pulmonary vein, to left atrium
• from left ventricle through aorta (to body)
Function of valves
Prevent backflow of blood
Difference between the pulmonary and systemic circuits?
- PULMONARY: blood takes up oxygen in the lungs
* SYSTEMIC: oxygenated body is distributed to body tissues
What are the atrioventricular valves and their function?
- mitral (bicuspid) - left
- tricuspid - right
Prevent the backflow of blood into the atria when the ventricles contract
What is the function of the pulmonary and aortic semilunar valves?
Prevent the backflow of blood into ventricles when ventricles relax
What are cardiomyocytes?
Cardiac muscle cells
Describe the features of the cardiac muscle
- Cardiomyocytes branched with cross striations - formed by myosin and actin
- intercalated discs - provide mechanical adhesion
- gap junctions - allow rapid transmission of electrical signal
- thickness of myocardium - affects pressure generated
Describe the steps in a heart cycle
RELAX - Diastole
1. atria contract
2. ventricles contract and atrioventricular valves close “lub”
CONTRACT - systole
3. pressure in the ventricles build and aortic/pulmonary valves open
4. blood is pumped out of the heart
5. ventricles relax and pressure drops at the end of systole
RELAX - diastole
6. pressure in arteries is higher, aortic and pulmonary arteries shut “dub”
7. heart fills with blood again
Summarise the the stages of the heart cycle with sounds
1. Relax - Diastole "Lub" 2. Contract - Systole "Dub" 3. Relax - Diastole
Describe the pressure changes during a human cardiac cycle
Diastole - relax
• volume in left ventricle high = low pressure
• pressure in aorta high
Systole - contract
• left ventricle decreased volume - high pressure
• aorta pressure also high
Diastole - relax
• left ventricle volume very low but starts to increase - pressure decreasing
• pressure of slowly decreases
Mitral regurgitation
Narrowing or leaking of valves
What are heart murmurs?
- Mital regurgitation
- congenital, age related changes, infections
- increased heart work and decreases efficiency - may decrease O2 levels in the blood
- shortness of breath, pain, fainting
- treatment: valve repair surgery if serious
What is Cardiomyopathy?
• Chronic disease of the heart muscle
Dilated cardiomyopathy
- Heart is weak and enlarged - cannot pump blood effectively
* most common type and is caused by various medical problems
Causes of Hypertrophic cardiomyopathy (HCM)
- Genetic
- Infections - damage cardiac muscle
- Excess, long-term alcohol consumption
- nutritional deficiencies
- extreme physical activity
Restrictive cardiomyopathy
- Ventricles don’t properly fill because heart muscle is still
- rare
Describe the structural changes in Hypertrophic cardiomyopathy (HCM)
- enlarged left ventricle wall - reduced space for blood which reduces output
- increased stiffness - reduces pumping force
- thicker ventricle septum
- disorganised cardiac muscle cells
Symptoms of hypertrophic cardiomyopathy (HCM)
Shortness of breath, fatigue, dizziness
- can result in sudden cardiac death
Explain the sounds that are heart when measuring blood pressure.
- First sound of flow “tapping” - systolic pressure
2. continuous “whoosh” sound - diastolic pressure
What are the different types of blood flow?
- Laminar blood flow - silent (pulse present)
- occluded blood flow - silent (no pulse)
- Turbulent blood flow is noisy
