respiration+3

DeMarcus Waggoner September 17, 2008 Respitory 3

The Kidney 1. Describe the path of urine and the structure and function of each organ in this path. (detail). pp.188-189 The Kidney produces urine and it is transported by the Ureters. The urinary blabber stores urine wile the urethra releases urine.

The Kidney’s are paired organs near the small of the back, on both sides of the vertebral column. They are protected by the lower rib cage, because they are in the depression of the back beneath the peritoneum. The kidneys are bean shaped and reddish brown in color. A tough capsule of fibrous connective tissue, called a renal capsule, covers the fist-sized organs. Masses of adipose tissue adhere to each kidney. The concave side of a kidney had a depression, where the renal artery connects and the renal vein and ureter exit the kidney. The Ureters are small muscular tubes that transport urine from the kidneys to the bladder. It is about 25 cm long and 5 mm in diameter. Each descends beneath the peritoneum to enter the bladder at its dorsal surface.. the wall of a ureter has three layers: an inner mucosa (mucous membrane), a smooth layer, and an outer fibrous coat of connective tissue. Peristaltic contractions cause urine to enter the bladder in spurts that occur at the rate of one to fiver per minute. The Urinary Bladder is the organ where urine is stored until it is ready to be expelled from the body. There are three openings to the Urinary bladder, two are for the ureters and one is for the urethra, which drains the bladder. A middle layer of circular fibers and two layers of longitudinal muscle allow the bladder to expand. When the epithelium of the mucosa becomes thinner, and it folds in the mucosa called ragae disappear as the bladder enlarges. Another way urine is contained is when the sphincters close that are located where the urethra exits the bladder. The internal sphincter occurs around the opening to the urethra. An external sphincter is composed of skeletal muscle that can be voluntarily controlled. The urethra is a tube that expels urine from the bladder. It is the last stop for the urine as it leaves the body. The size depends on the gender, for makes the urethra is longer, but for females its shorter which is more susceptible to bacterial infections. For females the urethra is about 4 cm long, but for males it averages around 20 cm long. In males the urethra is encircled by the prostate glands. In females the reproductive and urinary systems are not connected. In males, the urethra carries urine during urination and sperm during ejaculation. This double unction of the urethra in males does not alter the pat of urine.

2. Describe the four functions of the kidney and how they contribute to homeostasis (balance) (detail) p. 189

Excretion of Metabolic waste: Nitrogen waste is a part of the excretion process that takes place in the kidneys. Urea is the primary nitrogenous end product of metabolism I human beings, but humans also excrete some ammonium, creatinine, and uric acid. Urea is a byproduct of amino acid metabolism. The breakdown of amino acids in the liver releases ammonia, which the liver rapidly combines with carbon dioxide to produce urea. Ammonia is very toxic to cells, but urea is much less toxic. Creatinine is the breakdown of creatine phosphates, which is a high0energy phosphate reserve molecule in muscles. Uric acid comes from the break down of amino nucleotides, such as thymine and adenine. Uric acid is very insoluble. In some cases when there is too much present crystal begin to form in the blood and it is called gout. Gout symptoms come from the painful buildup of the crystals in the blood.

Maintenance of Water-Salt Balance The balance of salt and water, to the body, is very important. The kidneys use salts such as NaCl to cause osmosis, the diffusion of water into the blood. The more salts there are in the blood the greater the blood volume and the greater the blood pressure. So kidneys are involved in regulating blood pressure. The kidneys also regulate the level of ions, such as potassium ions bicarbonate ions and calcium ions in the blood.

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 about 7.4. The kidneys monitor and help control blood pH, mainly by excreting hydrogen ions and reabsorbing the bicarbonate ions as needed to keep blood pH at 7.4. Urine usually has a pH of 6 or lower because our diets often contain acidic foods. Secretion of Hormones The kidneys assist in the endocrine system in hormone secretion. The kidneys release rennin, a substance that leads to the secretion of the outer portions of the adrenal glands, which like atop the kidneys Adosterone promotes the reabsorbtion of sodium ions by the kidneys. When ever the oxygen-carrying compactly of the blood is reduced, the kidneys secrete the hormone erythropoietin which stimulates red blood cell production. The kidneys also help activate vitamin D from the skin. Vitamin D is a molecule that promotes calcium absorption from the digestive tract.

3. Trace the path of blood through the kidney. pp.191-192 The renal meuulla is a radically striated inner layer, and the renal cortex is an outer, granulated layer that dips in between the renal medulla. The renal medulla is a cone-shaped tissue mass called the renal pyramids. The renal pelvis 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 are the microscopic structure that are responsible for production of urine. 5. Describe the parts of the nephron (detail). pp.192-193 The closed end of the nephron is pushed in on itself to forma cup-like structure called the glomerular 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 cytoplasm extensions. The podocytes cling to the capillaries walls of the glomerulus and leave pores that allows passage of small molecules from the glomerulus to the inside of the glomerulus capsule. This process is called glomerular filtration, produces a filtrate of the blood. Next, there is a proximal convoluted tubule. The cubical epithelial cells lining this part of the nephron have numerous microvillus, about 1 µm in length, that are tightly packed and form a brush border. A brush border greatly increases the surface area for the tubular reabsorbtion of filtrate components. Each cell also has many mitochondria, which can supply energy for active transport of molecules from the lumen to the peritubular capillary network. Simple squamous epithelium appears as the tube narrows and makes a U-turn called the loop of the nephron. Each loop consist of an ascending limb that extrudes salt. And it Facilitates the reabsorbstion of water by the nephron and collecting duct. The cubiodial epithelial cells of the distal convoluted tubule have numerous mitochondria, but they lack microvilli. So the distal convulted tuble is not specialized for reabsorbtion but can participate in moving molecules from the blood into the tutule, a process called tubular secretion. The distal convoluted tubules of several nehrons 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 There are three main steps to urine formation glomerular filtration, tubular reabsorption, and tubular secretion. Glomercular Filtration occurs when whole blood enters the glomerulus by the way of the afferent arteriole. Tubular reabsorption occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the particular 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 dialsate, and substances more concentrated in the dialsate diffuse into the blood. The dialsate 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 renninn by the kidneys helps maintain blood pressure. The digestive system absorb nutrients, ions, and water. These help kidneys maintain the proper level of ions and water in the blood. 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 ndioxide as bicarbonat 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.