Kidney+Homework+NLL

__**The Kidney**__

1. Describe the path of urine and the structure and function of each organ in this path. (detail). pp.188-189 The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. 1. Kidneys produce urine. 2. Ureters transport urine. 3. Urinary bladder stores urine. 4. Urethra passes urine to outside. The kidneys are paired organs located near the small of the back, on either side of the vertebral column. The ureters conduct urine from the kidneys to the bladder. They are small, muscular tubes about 25 cm long and 5 mm in diameter. The urinary bladder stores urine until it is expelled from the body. The bladder has 3 openings: two for the ureters and one for the urethra, which drains the bladder. The urethra is a small tube that extends from the urinary bladder to an external opening. Its function is to remove urine from the body.

2. Describe the four functions of the kidney and how they contribute to homeostasis (balance) (detail) p. 189 The four functions of the Urinary System consist of the Exertion of Metabolic Wastes, Maintenance of Water-Salt Balance, Maintenance of Acid-Base Balance, and Secretion of Hormones. In Excretion of Metabolic Waste the kidneys excrete metabolic wastes, notably nitrogenous wastes. The Maintenance of Water-Salt Balance principal function of the kidneys is to maintain the appropriate waster salt balance of the blood. Maintenance of Acid-Base Balance the kidneys regulate the acid-base balance of blood. In order for a person to remain healthy, the blood pH should be just about 7.4. The kidneys control and monitor blood pH. 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, which lie atop the kidneys. The kidneys also help activate vitamin D from the skin. Whenever oxygen-carrying capacity of the blood is reduced, the kidneys secrete the hormone erythropoietin, which stimulates red blood cell production.

3. Trace the path of blood through the kidney. pp.191-192 The renal cortex is an outer, granulated layer that dips down in between a radically striated inner layer called the renal medulla. The renal medulla consists of cone-shaped tissue masses called renal pyramids. The renal pelvis 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. The nephrons produce urine and are positioned so that the flow into a collecting duct.

5. Describe the parts of the nephron (detail). pp.192-193 The closed end of the nephron is pushed in on itself to form a cuplike structure called the glormerular capsule. The outer layer of the glomerular capsule is composed of squamous epithelial cells; the inner layer is made up of podocytes that have long cytoplasmic extensions. Next there is a proximal convoluted tubule. The cubodial epithelial cells lining this part of the nephron have numerous microvilli, about 1um in length, that are tightly packed and form a brush border. Simple epithelium appears as the tube narrows and makes a U-turn called the loop of nephron. Each loop consists of a descending limb that allows water to leave and an ascending limb that extrudes salt. The cuboidal epithelial cells of the distal convulted tubule have numerous mitochondria, but they lack microvilli. The distal convoluted tubules of several nephrons enter one collecting duct. Many collecting ducts carry urine to the renal pelvis.

6. What are the major processes of urine formation and how does the nephron carry out each process? p. 195 The three main processes in urine formation are: Glomerular Filtration, Tubular Reabsorption, and Tubular Secretion. Glomerular Filtration occurs when whole blood enters the glomerulus by way of the afferent arteriole. Tubular Resbsoprtion occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network. Tubular Secretion is a second way by which substances are removed from blood and added to the tubular fluid.

7. Explain how an artificial kidney cleanses the blood. p. 200 The patient’s blood is passed through a membranous tube, which is a contact with a dialysis solution. Substances more concentrated in the blood diffuse into the dialysate, and substances more concentrated in the dialysate diffuse into the blood. The dialysate is continuously replaced to maintain favorable concentration gradients. In this way, the artificial kidney can be utilized either to extract substances from blood, including waste products or toxic chemicals and drugs, or to add substances to blood.

8. How do the kidneys assist other body systems? p. 201-202 The kidneys excrete nitrogenous wastes and maintain the water-salt balance and the acid-base balance of the blood. Production of rennin by the kidneys helps maintain blood pressure. The digestive system absorbs nutrients, ions, and water. These help kidneys maintain the proper level of ions and water in the blood. The kidneys regulate the amount of ions in the blood. The kidneys regulate the amount of ions in the blood. The kidneys help the lungs by excreting carbon dioxide as bicarbonate ions, while lungs help the kidneys maintain the acid-base balance of the blood by excreting carbon dioxide. The kidneys produce rennin, leading to the production of aldosterone, a hormone that helps the kidneys maintain the water-salt balance.