The+Kidney

1. Describe the path of urine and the structure and function of each organ in this path. (detail). pp.188-189 The kidneys produce the urine. The kidneys are bean-shaped organs that are on either side of the vertebral column. The urine is then transported by the Ureters. The Ureters send the urine to the urinary bladder, which is where the urine is stored. The Ureters can reach 25cm long and 5mm in diameter. Finally the urine passes through the urethra, which is a small tube that extends from the urinary bladder to an external opening.

2. Describe the four functions of the kidney and how they contribute to homeostasis (balance) (detail) p. 189 1. Excretion of Metabolic Wastes: The kidneys excrete metabolic wastes, mostly nitrogenous wastes. The breakdown of nucleotides, such as those containing adenine and thymine, are also in the first function of the kidneys. 2. Maintenance of Water-Salt Balance: A principle function of the kidneys is to maintain the appropriate water-salt balance of the blood. The kidneys maintain the appropriate level of other ions, such as potassium, bicarbonate, and calcium ions in the blood. 3. Maintenance of Acid-Base Balance: The kidneys regulate the acid-base balance of the blood. In order for a person to remain healthy the blood pH should be just be about 7.4. The kidney also monitor and help control blood pH. 4. Secretion of Hormones: the kidneys assist the endocrine system in hormone secretion. The kidneys release rennin, a substance that leads to the secretion of the hormone aldosterone from the adrenal glands.

3. Trace the path of blood through the kidney. pp.191-192 First the blood passes through the renal cortex, and it is an outer, granulated layer that dips down in between a radially striated inner layer called the renal medulla. Then the blood goes through the medulla, which consist of cone-shaped tissue masses called renal pyramids. Next blood passes through the renal pelvis, and it is a central space, or cavity, that is continuous with the ureter.

4. What microscopic structure is responsible for the production of urine in the kidney? p. 191 Nephrons are responsible for the production of urine in the kidney.

5. Describe the parts of the nephron (detail). pp.192-193 The glomerular capsule is the first part, and the closed end of the nephron is pushed in on itself to form a cuplike sructure. The outer layer of this is composed of squamous epithelial cells, and the inner layer is made up of podocytes that have long cytoplasm extensioins. The second part is a proximal convoluted tubule. A brush border greatly increases the surface area for the tubular reabsorption of filtrate components.

6. What are the major processes of urine formation and how does the nephron carry out each process? p. 195 Glomerular filtration is the first process, and it occurs when whole blood enters the glomerulus by way of the afferent arteriole. The nephron carries the process out because of the small molecules. The next process is Tubular Reabsorption. Occurs when nutrient and salt molecules are actively reabsorbed from the convoluted tubules into the peritubular capillary network, and water flows passively. The last process is Tubular secretion. That occurs when certain molecules are actively secreted from the peritubular capillary network into the convoluted tubules.

7. Explain how an artificial kidney cleanses the blood. p. 200 There is an artificial kidney machine. As the patient’s blood is pumped through dialysis tubing, it is exposed to dialysate. The blood is not only cleansed, but its water-salt and acid-base balances can also be adjusted.

8. How do the kidneys assist other body systems? p. 201-202 The kidneys assist the endocrine system and also the cardiovascular system by producing erythropoietin. The kidneys assist the skeletal, nervous, and muscular systems by helping regulate the amount of calcium ions in the blood.