The+Kidneys+AG

Allie Gruber Human Bio Field Period 1 September 17, 2008

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 are paired organs located near the small of the back, on either side of the vertebral column. Kidneys are bean-shaped and reddish brown in color. The kidneys produce the urine until the ureters conduct it from the kidneys and transport it into the bladder. The wall of a ureter has three layers: inner mucosa, a smooth muscle layer, and an outer figrous coat of connective issue. The urinary bladder stores urine until it is expelled from the body. After urine enters the bladder from a ureter. Small folds of bladder mucosa act like a valve to prevent backward flow. After being stored in the urinary bladder, it travels to the uretha, which is a small tube that extends from the urinary bladder to an external opening. Uretha removes the urine from the body and to the outside. It has different lengths depending on male and female body system.

2. Describe the four functions of the kidney and how they contribute to homeostasis (balance) (detail) p. 189 The kidneys excrete metabolic wastes such as nitrogenous wastes. Urea is the primary nitrogenous end product of metabolism in humans, but also excreted is ammonium, creatinine, and uric acid. Another function of the kidneys is to maintain the appropriate water-salt balance of the blood. This process is called maintenance of water-salt balance. Salts have the ability to cause osmosis in the blood, which can raise blood pressure. With this process the kidneys are involved in regulating the blood pressure. The kidneys are also responsible for regulating the acid-base balance of the blood. Human’s blood pH should be about 7.4, and the kidneys monitor and help control the blood pH by excreting hydrogen ions and reabsorbing the bicarbonate ions as needed. Lastly, 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.

3. Trace the path of blood through the kidney. pp.191-192 The kidney is structured in 3 separate regions; the renal cortex is an outer, granulated layer that dips down in between a radially striated inner layer called the renal medulla, the renal medulla, which consists of cone-shaped tissue masses called renal pyramids; and the renal pelvis, which 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 microscopic components of the kidney that produce urine and are positioned so that the urine flows into a collecting duct and eventually entering the renal pelvis.

5. Describe the parts of the nephron (detail). pp.192-193 The nephron is composed by a cuplike structure called the glomerular capsule. The outer later is made up of squamous epithelial cells and the inner layer is made up of podocytes that have long cytoplasmic extensions. Next there is a proximal convoluted tubule that includes numerous microvilli tightly packed and from a brush border. Simple squamous epithelium appears as the tube narrows and makes a U-turn called the loop of the 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 convoluted tubule have numerous mitochondria but they lack micrvilli. The distal convoluted tubule of several nephrons enters one collecting duct and then many of the 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 Glomerular filtration occurs when whole blood enters the glomerulus by way of the afferent ateriole. Due to glomerular blood pressure, water and small molecules move from the glomerulus to the inside of the glomerular capsule. Tubular reabsorption occurs as molecules and ions are both passively and actively reabsorbed from the nephron onto the blood of the pertiubular capillary network. The osmolarity of the blood is maintained by the presence of both plasma proteins and salt. Nutrients such as glucose and amino acids return to the pertibular capillaries almost exclusively at the proximal convoluted tubule. Tubular secretion is another way in which substances are removed from blood and added to the tubular fluid. Hydrogen ions, creatinine, and drugs are some of the substances that are moved by active transport from blood into the kidney tubule.

7. Explain how an artificial kidney cleanses the blood. p. 200 Substances more concentrated in the blood diffuse into the dialysate, and substances more concentrated in the dialysate diffuse into the blood. In this process, the artificial kidney can be utilized either to extract substances from blood, including waste products or toxic chemicals and drugs.

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. It is used to stimulate red bond marrow production and assist the skeletal, nervous, and muscular systems by helping regulate the amount of calcium ions in the blood. The kidneys also regulate the sodium and potassium content in the blood that are necessary to the contraction of the heart and other muscles in the body.