[7.3] circulatory system of a mammal

Question 1

why do large organisms have a transport system?

Answer 1

• with increasing size, the SA:V ratio becomes too small so SA is not enough for needs of organism
• specialist exchange surfaces are needed to absorb nutrients and oxygen, and remove waste
• a transport system is needed to move these materials

Question 2

what 2 factors determine if there is a specialised transport medium, and whether or not it is circulated by a pump?

Answer 2

• SA:V ratio
• how active the organism is

the lower the SA:V ratio, and the more active the organism, the greater the need for a specialised transport system with a pump

Question 3

what are common features of transport systems?

Answer 3

• a suitable medium to carry materials eg. blood, gas
• mass transport - transport medium is moved around in bulk and over large distances more rapidly than diffusion
• a closed system of tubular vessels that containing transport medium which forms a branching network to distribute it to all parts of the organism
• a mechanism for moving the transport medium within vessels
  > needs a pressure difference between one part of the system and another

Question 4

how can a successful transport system be achieved?

Answer 4

1. animals - muscular contractions eg. heart
2. plants - passive process eg. evaporation of water

• a way of keeping mass flow movement in one direction eg. valves
• a way of controlling flow of transport medium to suit changing needs of different parts of organism
• a mechanism for mass flow of water or gases eg. intercostal muscles and diaphragm for breathing

Question 5

describe the circulatory system that mammals have

Answer 5

• closed, double circulatory system
• blood goes heart -> lungs then back to heart and tissues

Question 6

why do mammals have a double circulatory system?

Answer 6

• when blood is passed through the lungs, its pressure is reduced
• if it were to pass immediately to the rest of the body, its low pressure would make circulation very flow
• blood is therefore returned to the heart to boost its pressure before being circulated to the rest of the tissues
• therefore, substances are delivered to the rest of the body quickly
• this is necessary as mammals have a high body temperature and hence a high rate of metabolism

Question 7

describe the flow of oxygenated blood through the mammalian circulatory system (a diagram would make more sense tbh)

Answer 7

• lungs to left atrium through pulmonary vein
• blood leaves left ventricle through aorta and brings it to:

> upper / fore limbs

> head and neck

> liver via hepatic artery

> stomach and intestines

> kidneys via renal artery

> lower / hind limbs

Question 8

describe the flow of deoxygenated blood through the mammalian circulatory system (a diagram would make more sense tbh)

Answer 8

• right ventricle to lungs via pulmonary artery
• superior vena cava brings blood to heart from head and neck, upper / fore limbs
• inferior vena cava brings blood to heart from liver, stomach and intestines, kidneys (via renal vein), and lower / hind limbs

Question 9

what is the hepatic portal vein?

Answer 9

• from stomach and intestines to liver
• extra blood supply to liver