Transport in mammals

8.1    The circulatory system
8.2    The heart


As animals  become larger, more  complex and more  active,  transport systems become essential to supply nutrients to, and remove waste from, individual cells. Mammals are far more  active than  plants  and require  much  greater supplies of oxygen.  This is transported by haemoglobin inside red blood cells. Candidates will be expected to use  the knowledge gained  in this section to solve problems in familiar and unfamiliar contexts.

Learning outcomes

Candidates should  be able to:

8.1    The circulatory system

The mammalian circulatory system consists of a pump, many  blood vessels and blood, which is a suspension of red blood cells and white  blood cells in plasma.

a)   state that  the mammalian circulatory system is a closed double circulation consisting of a heart,  blood vessels and blood

b)   observe and make  plan diagrams of the structure of arteries, veins and capillaries using prepared slides  and be able to recognise these vessels using the light microscope

c)   explain the relationship between the structure and function  of arteries, veins and capillaries

d)   observe and draw the structure of red blood cells, monocytes, neutrophils and lymphocytes using prepared slides  and photomicrographs

e)   state and explain the differences between blood, tissue fluid and lymph

f) describe the role of haemoglobin in carrying oxygen  and carbon dioxide with reference to the role of carbonic  anhydrase, the formation of haemoglobinic acid and carbaminohaemoglobin (details of the chloride shift are not required)

g)   describe and explain the significance of the oxygen dissociation curves of adult oxyhaemoglobin at different carbon dioxide concentrations (the Bohr effect)

h)   describe and explain the significance of the increase in the red blood cell count  of humans at high altitude

8.2    The heart

The mammalian heart  is a double  pump:  the right side pumps blood at low pressure to the lungs and the left side pumps blood at high pressure to the rest  of the body.

a)   describe the external and internal structure of the mammalian heart

b)   explain the differences in the thickness of the walls of the different chambers in terms of their functions with reference to resistance to flow

c)   describe the cardiac cycle (including blood pressure changes during systole and diastole)

d)   explain how heart  action is initiated  and controlled (reference should  be made to the sinoatrial  node, the atrioventricular node  and the Purkyne  tissue, but not to nervous and hormonal control)