(2) The gas exchange between the lungs and the outside world is called lung ventilation, which is realized by breathing movement. Gas always diffuses from high concentration to low concentration, and the gas exchange process between alveoli and blood is realized by gas diffusion.
(3) When the blood flows through the capillaries at the tissue cells, oxygen and nutrients in the blood enter the tissue cells and generate energy in the mitochondria of the cells through respiration to meet the needs of human life activities.
(4) The formation of urine includes two processes: filtration of the inner wall of glomerulus and renal capsule and reabsorption of renal tubules. In the figure, process B represents the filtration of the inner wall of glomerulus and renal capsule.
So the answer is: (1) glucose; Absorption; Small intestine?
(2) respiratory movement; Gas diffusion?
(3) a; oxygen
(4) filtration of the inner wall of glomerulus and renal capsule