How does entropy relate to the spontaneity of reactions?
An increase in entropy and a decrease in enthalpy increase the spontaneity of a process. The universe moves toward the greatest entropy. Any chemical reaction with a positive entropy change ΔS is favourable. Enthalpy change ΔH also determines whether a reaction is spontaneous or not.
What are the processes that occur in the kidneys to change the concentrations of urea, glucose and water in the blood?
The filtrate is formed by ultrafiltration. Glucose, amino acids, and soluble components enter the Bowman's capsule. Proteins in the blood plasma are not filtered out of the blood. As glucose is not normally in urine it must be reabsorbed. There is selective reabsorption of glucose in the proximal convoluted tubule by active transport. No urea is reabsorbed which leads to urea being more concentrated in urine than in blood plasma. Water is reabsorbed from filtrate by osmosis in proximal convoluted tubule. ADH levels affect the amount of water reabsorption in the collecting duct. The higher the levels of ADH, the more reabsorption.
How are the visceral organs of the lesser pelvis innervated?
By the plexus of nerves that originate from the sympathetic ganglia (both paravertebral and prevertebral) and the parasympathetic (pelvic splanchnic) nerves.