LECTURE ONE
• Understand the purpose of the circulatory system - The cardiovascular system has 2 circuits:
pulmonary and systemic.
- It transports O2 and nutrients to cells.
- It transports CO2 and waste from cells.
- It also transports hormones, antibodies and immune cells.
- Pulmonary circuit= oxygenate the blood.
- Systemic circuit= supplies cells with O2 and nutrients and removes CO2 and waste.
- Since the human body is large, we have many vascular beds in parallel.
- Cells are able to expel metabolic wastes and take in nutrients across the plasma
membrane down their concentration gradients. Cells can only afford to be a short distance from oxygen and nutrients.
• Discuss why the circulatory system structure is needed in humans
- CV system is required since cells require oxygen and nutrients from the environment.
- They also produce CO2 and metabolic wastes
- For small organisms surrounded by water, simple diffusion is sufficient.
- As organisms become larger, they require more complex systems to keep internal cells alive- especially if they are homeotherms.
- Circulation holds around 5L in the average individual. At rest the bulk of the blood is found in the systemic veins and venules (64%).
• List two key physical parameters that enable changes in fluid flow along a tube and how these affect flow
- Systemic circulation can be thought of as a pump generating a constant pressure which moves fluid across a variable resistance.
- Heart is a pump which generates pressure. This pressure drives blood through the blood vessels.
- Fluid flow is dependent on the pressure difference. Fluid will only flow if there is a positive pressure gradient.
- If there is no pressure gradient, no flow is present. Flow depends on the change in pressure, not absolute pressure.
- Higher P- lower P= change in pressure.
- The volume of fluid which flows through a tube depends on a pressure difference and the resistance to flow.
- Flow= change in pressure/resistance. As resistance increases, diameter of the pipe decreases.
• Draw the flow of blood through the chambers of the heart and heart valves indicating where the blood is coming from and going to in terms of pulmonary and systemic circulations
• Describe the function of those anatomical features mentioned in this module
Pericardium= membrane that surrounds and protects the heart. It confines the heart in the mediastinum (area from sternum to vertebral column between lungs).
Epicardium= thin outer layer of the heart wall, composed of serous tissue and mesothelium.
Myocardium= responsible for pumping action of the heart and is composed of cardiac tissue.
Endocardium= thin layer of endothelium providing smooth lining for chambers of heart and convers chambers of heart. The endothelial lining minimizes surface friction as blood passes through the heart.
Right Atrium:
- Receives blood from the systemic circuit through the two great veins: superior vena cava and inferior vena cava. Also receives blood from the coronary sinus.
- Superior vena cava= opens into posterior and superior portion of right atrium.
Delivers blood to right atrium from head, neck, upper limbs and chest.
- Inferior vena cava= opens into posterior and inferior portion of right atrium. Carries blood to the right atrium from the rest of the trunk, viscera and lower limbs.
- Coronary veins of heart returns blood to coronary sinus. Coronary sinus= thin vein that opens into right atrium inferior to the connection with inferior vena cava.
- Posterior wall of right atrium and interatrial septum= smooth surfaces.
- Anterior atrial wall and inner surface of auricle= muscular ridges/pectinate muscles.
Right ventricle:
- Right atrium into right ventricle through broad opening bounded by 3 fibrous flaps=
right atrioventricular valve (AV). AV= tricuspid valve.
- Right AV closes when right ventricle contracts to prevent backflow of blood into right atrium.
- Connective tissue fibres- chordae tendineae also prevent backflow of blood. The cusps of the tricuspid valve is connected to the chordae tendineae.
- Trabecular carneae= series of muscular ridges in the internal surface of ventricle - Moderator band= muscular ridge that extends horizontally from interventricular
septum to papillary muscle. This ridge contains the conducting system that coordinates contractions of cardiac muscle cells.
- Blood passes from right ventricle through the pulmonary valve into the pulmonary trunk (artery).
