The+Kidneys+Questions+SLS

September 17, 2008 Human Bio**
 * Shelby Smith

**The Kidney ** **1. Describe the path of urine and the structure and function of each organ in this path. (detail). pp.188-189** Kidneys, ureters, urinary bladder and urethra. The kidneys are paired organs located near the small of the back. They are bean-shaped and reddish-brown, and they produce urine. The ureters conduct urine from the kidneys to the bladder and they are small muscular tubes with three layers: an inner mucosa, a smooth muscle layer another fibrous coat of connective tissue. The urinary bladder stores urine until it is expelled from the body. The bladder is small and is able to stretch out in order to accommodate the urine. Urethra is a small tube that extends from the urinary bladder to an external opening. It’s function is used 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 excretion of metabolic wastes: The kidneys excrete metabolic wastes, notably nitrogenous wastes. Humans also excrete some ammonium, creatinine, and uric acid. Maintenance of Water-Salt Balance: The kidneys main function is to also maintain the balance of water and salt in the body. They also maintain the appropriate levels of other ions such as bicarbonate, and calcium ions which are found in the blood. Maintenance of Acid-Base Balance: Kidneys monitor and help control blood pH, mainly by excreting hydrogen ions. Secretion of Hormones: The kidneys assist the endocrine system in hormone secretion.

**3. Trace the path of blood through the kidney. pp.191-192 ** The blood travels through the renal cortex, and then the renal medulla and lastly the renal pelvis.

**4. What microscopic structure is responsible for the production of urine in the kidney? p. 191 ** The nephrons.

**5. Describe the parts of the nephron (detail). pp.192-193 ** They are positioned so that urine flows into a collecting duct. Each nephron has it’s own blood supply, which include capillary regions. The nephron is pushed into itself glomerular capsule. The outer layer of the glomerular capsule has podocytes which cling to the capillary walls and allow easy passage of small molecules from the glomerulus to the inside of the glomerular capsule. Next, there’s the proximal convoluted tubule and lastly there is the loop of the nephron and the distal convoluted tubule.

**6. What are the major processes of urine formation and how does the nephron carry out each process? p. 195 ** The major processes of urine formation are Glomerurlar Filtration which is when the whole blood enters the glomerulus by way of the afferent arteriole. The glomerulus filters the blood and transfers it into the glomerular filtrate, which holds the filtered blood. The nephron in the kidneys filters the water, and if this process didn’t happen, we would use water and nutrients that would be excreted through urine. Next is the Tubular Reabsorbtion which occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of ther peritubular capillary network. The reabsorbtion of salt increases the osmolarity of the blood, and therefore water moves passively from the tubular into the blood. Lastly, there is tubular secretion, which is when substances are removed from the blood and added to the tubular fluid. Ultimatley, urine contains substances that have undergone tubular filtration but have not been reabsorbed, and substances that have undergone tubular secretion.

**7. Explain how an artificial kidney cleanses the blood. p. 200 ** An artificial kidney cleanses the blood by pumping the blood through a dialysis machine which is when a patient’s blood is exposed to dialysate. Blood is not only cleansed by this system but the acid-base and the salt-water balance can be adjusted.

**8. How do the kidneys assist other body systems? p. 201-202 ** The kidney’s primary function is to clean the urine. But it is also an assist in the cardiovascular system by producing rennin, which helps maintain blood pressure. They also assist in Digestive System where it excretes the urine. It also assists the nervous system, the respiratory system, the endoctrine system, and lastly the integumentary system.