Circulatory system Flashcards
The CVS is made up of 2 circulatory pathways
- Pulmonary circulation
- Systematic circulation
- Pulmonary circulation
Circuit through the lungs where blood is oxygenated
- Systematic circulation
Circuit through the rest of the body to provide oxygenated blood
The 2 circuits are linked to each other through the ______ creating a ______
heart
continuous cycle of blood through the body
Systemic circulation process
- oxygen rich blood is pumped from the left ventricle into the ascending aorta.
- The aorta makes an inverted U-turn to form the aortic arch, which gives rise to branches that supply the head, neck and upper limbs
- The aorta continues posterior to the heart, as the descending aorta
- Which travels through the thoracic and abdominopelvic cavities.
- It supplies organs of these two cavities and the lower limbs
- In systemic capillaries, oxygen is exchanged for CO2, resulting on oxygen poor blood
- The oxygen poor blood enters the RA via the SVC and IVC
Pulmonary circulation process
- Oxygen poor blood is pumped from the RV into the pulmonary trunk.
- The large pulmonary trunk divides into the R and L pulmonary arteries.
- These arteries transport blood to the R and L lungs
- In pulmonary capillaries, CO2 is exchanged for O2.
- This results in O2 rich blood that them flows through the 4 pulmonary veins and enters the left atrium
Blood flow through the heart
- Heart is a functional pump from 8 weeks
- RA recieves venous blood from: SVC, IVC, coronary sinus
- RV recieves venous blood:
- Via tricuspid valve (R AV valve)
- exits via conus arteriosus/ infundibulum through pulmonary valve to pulmonary trunk
- pulmonary arteries to lungs - LA receives O2 blood from 4 pulmonary veins from lungs
- LV receives o2 blood:
- via bicuspid valve ( L AV valve/ mitral valve)
- Exits via aortic vestibule, then through aortic valve
- Ascending aorta
What is the main difference between foetal circulation and normal circulation?
Mainly because the lungs are not used
how does the foetus receive O2 and stuff if lungs not used?
- from mother
- Through the placenta and umbilical chord
Main structures involved in foetal circulation
- Placenta
- umbilical vein
- ductus venosus
- umbilical arteries
- foramen ovale
- ductus arteriosus
Foetal circulation
- Blood rich in nutrients and oxygen, supplied from the placenta, flows from the umbilical vein to the ductus venosus
- Blood flows from the ductus venosus to the IVC, up to the RA
- This blood mixes with blood returning to the heart, from the upper body, via the SVC and from the lower body via the IVC
- Once in the RA, some of the blood flows to the RV
- And some flows to the foramen ovale, to the left atrium and then to the LV
- It is then pumped out, into the aorta to the body
- Blood that flows into the RV is then pumped to the pulmonary artery
- because the lungs are fluid filled, instead of air filled, vessels in the lung are narrow, creating higher resistance to blood flow to the lungs
- Due to this high resistance to blood flow in the pulmonary circulation and the low resistance to blood flow in the systemic circulation, blood pumped into the pulmonary artery by the RV, is more likely to flow into the ductus arteriosus and then into the aorta.
- Due to the high blood flow, from the SVC and IVC, up to the RA, pressures in the RA are higher than in the LA
- This promotes blood flow from the foramen ovale at the atrial level
- Only 8% of right ventricular output flows into the lungs, providing nutrients to the developing lung tissues
- Most of the blood passes through the ductus arteriosus, into the aorta and out, into the body
- the umbilical arteries allow blood to flow from the body, back to the placenta, to be enriched with O2 and nutrients
Once the baby is born and takes a breath, what happens?
- the umbilical chord clamped and the placenta is removed from systemic circulation
- the transition from foetal to post natal circulation begins immediately
What is the result of the removal of the placenta from systemic circulation?
systemic vascular resistance begins to rise
- with each breath, more alveoli in the lungs expand
- and the vessels surrounding them dilate in response to the presence of oxygen
