Topic 8 – Exchange and Transport in Animals- The circulatory system Flashcards
What is the circulatory system?
● Network of organs and vessels
● Enables the flow of blood and transport of oxygen, carbon dioxide, nutrients and other molecules around the body
What are the main components of blood?
● Red blood cells
● White blood cells
● Platelets
● Plasma
What are red blood cells also known as?
Erythrocytes
What is the function of red blood cells?
● Transport O2 from lungs to tissues
● Transport CO2 from tissues to lungs
How do red blood cells transport oxygen to body cells?
● Lungs, haemoglobin in RBCs binds reversibly with oxygen to form oxyhaemoglobin
● Tissues, oxyhaemoglobin breaks down to form haemoglobin and oxygen which diffuses into cells
How are red blood cells adapted to their function?
● Biconcave disk gives large SA/V ratio, increasing diffusion rate
● Lack nucleus, allowing more space for haemoglobin molecules (increases oxygen carrying capacity of the cell)
● Small and flexible so they can squeeze through capillaries
● Thin giving a short diffusion distance
What is the function of white blood cells?
Provide immunological protection
Name two types of white blood cell
● Phagocytes
● Lymphocytes
What are phagocytes?
● Type of WBC
● Engulf pathogens and digest them in a process known as phagocytosis
What are lymphocytes?
● Type of WBC
● Produce antibodies specific to a pathogen
● Produce antitoxins to neutralise toxins
What is the function of platelets?
Role in blood clotting
What is plasma?
● Pale-yellow liquid portion of the blood
● Contains proteins, nutrients, waste products, hormones, antibodies etc.
How is plasma adapted to its function?
Plasma consists mainly of water. This acts as a solvent, enabling the transport of materials around the body.
What are the three main types of blood vessel?
● Arteries
● Capillaries
● Veins
What is the function of the arteries?
Carry blood away from the heart under high pressure
Describe how the arteries are adapted to their function (6)
● Narrow lumen maintains high pressure
● Thick wall to withstand high pressure
● Thick layer of smooth muscle provides strength
● Thick layer of elastic fibres allow stretch and recoil
● Smooth inner lining to reduce friction
● No valves
What is the function of the veins?
Return blood to the heart under low pressure
Describe how the veins are adapted to their function (4)
● Large lumen eases blood flow
● Thin wall as blood at low pressure
● Thin layer of smooth muscle and elastic fibres
● Valves prevent backflow of blood
What is the function of the capillaries?
Allow the exchange of materials at tissues
Describe how the capillaries are adapted to their function (4)
● Form large network ∴ greater surface area for diffusion
● Walls one cell thick giving a short diffusion distance
● Walls permeable allowing the exchange of substances ● Narrow lumen decreases diffusion distance
Describe the double circulatory system in humans
Blood flows through the heart twice in two circuits:
● Pulmonary circuit
● Systemic circuit
What is the pulmonary circuit?
● Part of the circulatory system involving the right side of the heart
● Deoxygenated blood is transported to the lungs
● Gaseous exchange occurs between the alveoli and capillaries in the lungs
● Oxygenated blood is returned to the left side of the heart
What is the systemic circuit?
● Part of the circulatory system involving the left side of the heart
● Oxygenated blood is pumped to tissues and organs around the body
● Exchange of materials occurs at tissues
● Deoxygenated blood returns to the right side of the heart
Name the four chambers of the heart
● Left atrium
● Left ventricle
● Right atrium
● Right ventricle
Describe the pathway of blood around the body, naming the structures of the heart
Pulmonary vein → Left atrium → Left ventricle → Aorta → Body → Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs
Why is the left ventricle thicker than the right ventricle?
● It pumps blood a further distance
● It must generate a greater force of contraction so blood can be pumped at a higher pressure
What is the function of valves in the heart?
Prevent the backflow of blood
What is cardiac output?
The volume of blood pumped out of a ventricle in one minute
What is stroke volume?
The volume of blood pumped out of a ventricle in one contraction
What is heart rate?
The number of times the heart contracts in one minute
How is cardiac output calculated?
cardiac output = heart rate × stroke volume (cm3 min-1) (bpm) (cm3)
