19. Vertebrate Heart Structure And Function

Question 1

Why do animals need a circulatory system?

Answer 1

• O2 and nutrients must be transported around the body to tissues and organs
• Waste products must be removed
• Communication via hormones
• Temperature regulation and reproduction, etc

Question 2

How does blood circulate in an open circulatory system?

Answer 2

• Blood (haemolymph) flows freely within body cavities making direct contact with all tissues and organs
• Hearts pump the fluid to different regions of the body via blood vessels
• Vessels are open ended so blood flows out and bathes tissues
• All components of the haemolymph leave the vessels
• Fluid drains back to the heart. Enters the heart when relaxed via Ostia (openings) which act as valves to ensure one way flow of fluid

Question 3

What are the characteristics of a closed circulatory system?

Answer 3

• Circulating fluid (blood) contained in a continuous series of vessels
• Hearts pump fluid to different regions of the body through blood vessels
• Specific components of the lucid filter out of the vessels (in capillaries) to penetrate tissues.
  🔸 Small solutes and water leave
  🔸Larger molecules and blood cells remain
• Transport fluid (blood) is kept separate from fluid that surrounds cells (interstitial fluid)
• Fluid returns to the heart via veins, with valves to ensure one way flow of fluid

Question 4

What are the advantages to a closed circulatory system?

Answer 4

• Faster transport and more efficient delivery of fluid to tissues
• Ability to control distribution of blood to specific tissues (by changing vessel resistance)
• Assists in the delivery of larger molecules (nutrients and hormones) to specific tissues
• Enabled the evolution of circulatory systems which keep oxygenated blood separated from deoxygenated blood

Question 5

How have vertebrate heart chambers evolved?

Answer 5

• One atrium and ventricle, one circulation
• Specialisation of vessels (arteries and veins)
• Blood pumped over gills to become oxygenated and leaves under very low pressure
• Very low pressure in capillary beds and limits efficiency of delivery of nutrients and o2 to tissues

Question 6

What is the bulbous arteriosus in fish hearts?

Answer 6

Found in teleosts. It is elastic and works to reduce extreme pulsing of blood leaving the ventricle, giving more constant, even flow

Question 7

What is the sinus venosus?

Answer 7

The preliminary collecting chamber.

In teleosts it is filled primarily from the hepatic veins. No muscular wall

Question 8

What is the heart structure of air breathing fish?

Answer 8

• 2 circulations: pulmonary and systemic
• Partially divided atrium and ventricle
  🔸 Left receives oxygenated blood from lungs
  🔸 Right receives deoxygenated blood from body
• Gill specialisations: low resistance bypass to lung and direct link to aorta
• Oxygenated blood is separated from deoxygenated blood

Question 9

What is the heart structure of amphibians?

Answer 9

• 3 Chambered heart
• Left atrium contains oxygenated blood from the lungs while the right atrium received deoxygenated blood from the body
• Single ventricle: potential for some mixing of blood, but a septum directs blood movement and maintains separation
• Partial separation of pulmonary and systemic circuits allows different pressures

Question 10

What is the structure of the reptile heart?

Answer 10

• 3 or 4 chambered heart
• Have 2 aortae. The left receives oxygenated blood from left ventricle to the body while the right receives blood from both ventricles (mixed)
• Reptiles don’t always breathe. Blood by passes lungs and flows directly to the systemic circuit via the right aorta (shunt)
• direction of blood flow is controlled by resistance in the pulmonary circuit ( lower when animal is breathing)

Question 11

What is the structure of bird and mammal hearts?

Answer 11

• 4 chambered hearts

- Separate pulmonary and systemic circuits

Question 12

What are the advantages of the 4 chambered mammalian heart?

Answer 12

• Pulmonary and systemic circuits can operate at different pressures
• Systemic circuit always receives blood with a higher O2 content
• Gas exchange is maximised

Question 13

What is atrial septal defect?

Answer 13

A hole in the septum (muscle wall) between atria. Congenital = present at birth

Question 14

How does atrial septal defect affect the blood

Answer 14

Deoxygenated and oxygenated blood mix, and the heart doesn’t work efficiently

Question 15

What are the symptoms of ASD?

Answer 15

Shortness of breath, fainting, irregular heart rhythm and fatigue after mild activity

Question 16

What is the purpose of valves in the heart?

Answer 16

They prevent backflow, so that blood always flows from high pressure to low pressure

Question 17

Where does blood come into the heart from the body?

Answer 17

Vena cava

Question 18

Where does blood leave the heart to the lungs (pulmonary circuit)?

Answer 18

Pulmonary artery

Question 19

Where does blood enter the heart from the lungs?

Answer 19

Pulmonary vein

Question 20

Where does blood leave the heart to go to the body (systemic circuit) from?

Answer 20

Aorta

Question 21

Which valve is between the right atrium and right ventricle?

Answer 21

Tricuspid valve

Question 22

Which valve is in between the left atrium and the left ventricle?

Answer 22

The bicuspid valve (mitral)

Question 23

How is the structure of the atrioventricular valves (bicuspid and tricuspid) related to their funciton?

Answer 23

They lie between the atria and the ventricles and prevent backflow into the atria when the ventricles contract

Question 24

What do the pulmonary and aortic valves do?

Answer 24

They lie between the ventricles and the major arteries and prevent backflow not ventricles when ventricles relax

Question 25

How is the structure of cardiac muscles related to their function?

Answer 25

• Cardiomyocytes are branched with cross striations formed by myosin and actin
• Intercalated discs provide mechanical adhesion
• Gap junctions allow rapid transmission of electrical signal (syncytium)
• The thickness of the myocardium affects the pressure generated

Question 26

What are the steps of the cardiac cycle and heart sounds in humans?

Answer 26

1. The atria contract
2. “Lub”: the ventricles contract, the atriventricular valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open
3. Blood is pumped out of the ventricles and into the aorta and pulmonary artery
4. “Dup” The ventricles relax; pressure n the ventricles falls at the end of the systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut
5. The ventricles fill with blood

Question 27

What are heart murmurs and what is their effect?

Answer 27

• Narrowing or leaking of valves (e.g mitral regurgitation)
• Congenital, age related changes, infections
• Heart murmurs (whooshing sounds)
• Valve repair surgery is the only option if the condition is serious

Question 28

What are the three types of cardiomyopathy?

Answer 28

Dilated, Hypertrophic and restrictive

Question 29

What does dilated cardiomyopathy involve?

Answer 29

Heart is weak and enlarged and cannot pump blood effectively. Caused by various medical problems. Most common type

Question 30

What does hypertrophic cardiomyopathy involve (HCM)?

Answer 30

Heart muscle is thickened, reducing the space for blood, resulting in reduced output.

Often genetic

Question 31

What does restrictive cardiomyopathy involve?

Answer 31

Ventricles don’t properly fill because heart muscle is stiff

Rare

Question 32

What are some structural differences caused by HCM?

Answer 32

Enlarged left ventricle wall
Thick ventricular septum
Disorganised cardiomyocytes

Affects blood flow through the heart; less filling room and increased stiffness reduces pumping force

Question 33

What are the types of blood flow and their sounds when measured?

Answer 33

• Laminar blood flow is silent (pulse present)
• Occluded blood flow is silent (no pulse)
• Turbulent flow is noisy