Edexcel A (SNAB) A Level Biology:复习笔记1.1.3 Mammalian Heart: Structure & Function

Mammalian Heart: Structure & Function

  • Circulatory systems are systems which transport fluids containing materials needed by the organism, as well as waste materials that need to be removed
  • Circulatory systems are described as being either open or closed
    • In a closed circulatory system blood is pumped around the body and is always contained within a network of blood vessels
    • In an open circulatory system the blood, or blood equivalent, is inside the body cavity and bathes the organs
  • Circulatory systems can also be either double or single
    • Double circulatory systems have two loops; one to the lungs and one to the body
    • Single circulatory systems have one loop that includes the lungs and the body
  • Humans have a closed, double circulatory system; in one complete circuit of the body blood passes through the heart twice
    • The right side of the heart pumps blood deoxygenated blood to the lungs for gas exchange; this is the pulmonary circulatory system
    • Blood then returns to the left side of the heart, so that oxygenated blood can be pumped at high pressure around the body; this is the systemic circulatory system

Heart structure

  • The human heart has a mass of around 300 g and is roughly the size of a closed fist
  • The heart is a hollow, muscular organ located in the chest cavity
  • It is protected in the chest cavity by the pericardium, a tough and fibrous sac
  • The heart is divided into four chambers
    • The two top chambers are atria
    • The bottom two chambers are ventricles
  • The left and right sides of the heart are separated by a wall of muscular tissue called the septum
    • The septum is very important for ensuring blood doesn’t mix between the left and right sides of the heart

human-heart-structure

The human heart is adapted for pumping blood around the body

Heart-Dissection-1

The heart is a muscular organ; the muscle itself is supplied with blood by the coronary arteries, enabling it to pump blood via a series of major blood vessels

Valves in the heart

  • Valves are important for keeping blood flowing forward in the right direction and for maintaining the correct pressure in the chambers of the heart
    • The right atrium and right ventricle are separated by an atrioventricular (AV) valve known as the tricuspid valve
      • Remember; the right side of the heart has a tricuspid valve
    • The left atrium and left ventricle are separated by another AV known as the bicuspid valve
    • The right ventricle and the pulmonary artery are separated by a semilunar (SL) valve known as the pulmonary valve
    • The left ventricle and aorta are separated by another SL valve known as the aortic valve
  • Valves in the heart
    • Open when the pressure of blood behind them is greater than the pressure in front of them
    • Close when the pressure of blood in front of them is greater than the pressure behind them
  • The valves are attached to the heart walls by valve tendons, or cords; these prevent the valves from flipping inside out under high pressure

Adaptations of the Structures of the Heart Table

adaptations-of-the-structures-of-the-heart-table

Blood vessels and the heart

  • There are two blood vessels bringing blood into the heart; the vena cava and pulmonary vein
    • The vena cava brings blood from the body
    • The pulmonary vein brings blood from the lungs
  • There are two blood vessels taking blood away from the heart; the pulmonary artery and aorta
    • The pulmonary artery takes blood to the lungs
    • The aorta takes blood to the body
  • The muscle of the heart itself is supplied with blood by a series of blood vessels known as the coronary arteries
    • The coronary arteries can be seen running across the surface of the heart

Exam Tip

When looking at a diagram of a heart remember that the right side of the heart will appear on the left of the diagram, as if you are looking at someone else's heart in front of you

 

 

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