How does the mammalian kidney/ nephron functions/ describe the process of excretion in the kidney/ explain the role of kidney in eliminating excess amino acids from the body/ how is urine formed?
Answer:
-The kidney/ nephron receives blood from the renal artery at higher pressure through afferent arteriole into the glomerulus; blood contains urea, blood cells, dissolved food substances, water, hormones and blood proteins;
-The afferent arteriole entering the glomerulus is wider that the efferent arteriole leaving it/ efferent arteriole is narrower than afferent arteriole;
-Higher blood pressure; narrowness of the efferent arteriole; and narrower lumen of glomerulus; cause higher pressure in the glomerulus; higher pressure causes small sized substances (water, urea, glucose, mineral salts, amino acids) to filter through glomerular wall/ endothelium into the capsular cavity/ Bowman’s capsule; forming glomerular filtrate; (in the process called ultrafiltration).
-Ultrafiltration is important to allow excretion/ removal of metabolic/ nitrogenous wastes;
-Large sized substances (blood cells and blood proteins) do not filter through small pores of glomerulus and Bowman’s capsule; instead they flow to efferent arteriole;
-The glomerular filtrate then flows to the proximal convoluted tubules where selective reabsorption; of amino acids, glucose, vitamins, and some water are reabsorbed through diffusion and active transport and water through osmosis;
-Selective reabsorption is important to allow return/ reabsorption of useful substances back into the blood stream;
-The filtrate then flows to the descending arm/ limb of loop of Henle where water is selectively reabsorbed through osmosis; under the influence of Anti-diuretic hormone (ADH);
-At the ascending arm/ limb of Loop of Henle, sodium ions /salts / mineral salts/ ions are selectively re-absorbed through active transport; Re-under the influence of aldosterone hormone;
-The filtrate then flows to distal convoluted tubule where water is reabsorbed through osmosis;
-The filtrate/ urine then flows to collecting duct where water is reabsorbed through osmosis; Urine contains urea, excess salts, water, some ammonia, some uric acid; which is transported to the urinary bladder for temporary storage before it is lost through urination.
-The afferent arteriole entering the glomerulus is wider that the efferent arteriole leaving it/ efferent arteriole is narrower than afferent arteriole;
-Higher blood pressure; narrowness of the efferent arteriole; and narrower lumen of glomerulus; cause higher pressure in the glomerulus; higher pressure causes small sized substances (water, urea, glucose, mineral salts, amino acids) to filter through glomerular wall/ endothelium into the capsular cavity/ Bowman’s capsule; forming glomerular filtrate; (in the process called ultrafiltration).
-Ultrafiltration is important to allow excretion/ removal of metabolic/ nitrogenous wastes;
-Large sized substances (blood cells and blood proteins) do not filter through small pores of glomerulus and Bowman’s capsule; instead they flow to efferent arteriole;
-The glomerular filtrate then flows to the proximal convoluted tubules where selective reabsorption; of amino acids, glucose, vitamins, and some water are reabsorbed through diffusion and active transport and water through osmosis;
-Selective reabsorption is important to allow return/ reabsorption of useful substances back into the blood stream;
-The filtrate then flows to the descending arm/ limb of loop of Henle where water is selectively reabsorbed through osmosis; under the influence of Anti-diuretic hormone (ADH);
-At the ascending arm/ limb of Loop of Henle, sodium ions /salts / mineral salts/ ions are selectively re-absorbed through active transport; Re-under the influence of aldosterone hormone;
-The filtrate then flows to distal convoluted tubule where water is reabsorbed through osmosis;
-The filtrate/ urine then flows to collecting duct where water is reabsorbed through osmosis; Urine contains urea, excess salts, water, some ammonia, some uric acid; which is transported to the urinary bladder for temporary storage before it is lost through urination.
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Explain what would happen to red blood cells if they are placed in a concentrated salt solution. 
