Answers, BIO 2320, Urinary

Objectives – 4, BIO 2320, Urinary SystemAnswers


1.Homeostasis. Rid body of liquid waste, water balance, filter blood, vitamin D activation, regulates blood pressure and regulates erythropoiesis.

2.Kidneys, Ureters, Urinary bladder, Urethra

3.External to parietal peritoneum

4.Inner to outer: Renal capsule, adipose capsule, renal fascia

5.Medial indentation where blood vessels enter/exit kidney, cortex is outer portion of kidney, medulla is inner, medulla has triangular shaped regions called pyramids, the apex (point) of each pyramid is a papilla, the pelvis is a funnel-like structure inside the kidney in the region of the hilus collecting urine from the pyramids and has extensions into the pyramids called calyces.

6.Tremendous! Via Renal arteries. About 1/5 of cardiac output

7.Nephron; Glomerulus & Glomerular capsule, Renal tubules including proximal convoluted tubule, descending limb of the loop of Nephron, loop of nephron, ascending limb of loop of nephron, distal convoluted tubule, followed by collecting ducts or tubules.

8.Glomerulus is a tuft or network of permeable blood capillaries. It is surrounded by the capsule (Bowman’s Capsule) and these two structures comprise the renal corpuscle. Renal = Kidney

9.Nephrons filter blood to make liquid waste, or urine. They control blood pressure, volume and pH. They remove waste from bloodstream such as protein metabolic waste called urea.

10.Filtration occurs from the glomerulus into the glomerular capsule. It is a passive process influenced by the size of the particles & whether or not they can fit through the pores of the glomerulus and not based on need. Blood pressure in the glomerulus certainly is a driving force.

11.Glomerular hydrostatic pressure (is blood pressure in glomerulus) drives filtration. Opposing factors are not strong enough to oppose filtration, but include the osmotic pressure in the glomerulus as well hydrostatic pressure in the glomerular capsule.

12.Increased pressure increases filtration and decreased pressure decreases filtration

13.Active reabsorption requires ATP and passive does not. Glucose is reabsorbed from the proximal convoluted tubule to the bloodstream by active transport. Water follows passively.

14.The significance is that as you descend into the medulla, the interstitial fluid is very concentrated which offers some great “drawing” power for pulling water out of the kidney tubules. The concentration is maintained by having the vasa recta operate in a countercurrent mechanism so that all of the solutes are not removed from the interstitial region. Additionally, urea adds to the interstitial concentration, as does differential permeability of the different portions of the nephron.

15.The proximal convoluted tubule is where most reabsorption occurs. Most nutrients and water are reabsorbed here. As you descend the limb of the nephron, it is permeable to water and water is reabsorbed. At the loop, urea enters the loop from the interstitial region & is recycled back into the urine. The ascending limb is permeable to salt but not water. As you ascend into a weakly concentrated interstitial region the salt will be reabsorbed. The distal convoluted tubule is ADH and aldosterone dependent. If ADH is present, water is reabsorbed. If aldosterone is present, sodium is reabsorbed and water passively follows. The collecting duct is also hormone dependent. If ADH is present, you will have significant water reabsorption resulting in small amounts of highly concentrated urine. It gets so concentrated, that near the bottom of the collecting duct, even urea is reabsorbed into the interstitial region. Secretions of substances such as hydrogen ions, ammonia, and drugs occur primarily in the convoluted tubules. Here substances can pass directly from the bloodstream into these tubules.

16.Juxta = near. These are some cells of the wall of the distal convoluted tubule that make renin. Renin is an enzyme the activates angiotensinogen, which leads to increased blood pressure.

17. ADH is made by the hypothalamus but stored in the posterior pituitary gland. It causes water reabsorption in the nephron.

18.Aldosterone is made by the adrenal cortex. It causes sodium reabsorption from the nephron and water passively follows.

19.Two parallel tubes running in opposite directions benefit each other. For example if salt is pulled out of one tube, it facilitates pulling water out of the parallel tube.

20.There is a vast decrease in volume and increase in concentration upon traveling through the proximal convoluted tubule. After descending the limb, the concentration increases and volume decreases. After ascending the limb, the concentration decreases and volume is unchanged. After the DCT and collecting tubule, if ADH is present, the volume decreases and concentration increases.

21.Vasa recta serve the limbs of the nephron. They are parallel tubes of blood flow running in opposite direction.

22.The precursor is made by the kidney and stimulates RBC production.

23.500mls urine per day is the minimum to wash your liquid waste out of your body.

24.Ureters run retroperitoneal from kidney to urinary bladder. Their function is peristalsis. The urinary bladder is in the pelvic cavity & functions only to store urine. Note that urine is in its final form once it leaves the collecting ducts of the nephron, in the kidney. No other changes can be made at this point.

25.Two sphincters, with the internal one being smooth muscle and the external being skeletal muscle.

26.Micturition is voiding urine. As the bladder wall stretches, it reflexively sends a message to the sacral region of the spinal cord, which synapses and sends a message back to the bladder wall to contract and the internal sphincter to relax. At this point you have the urge to urinate and will do so unless you voluntarily contract the external sphincter. The pathway from brain to external sphincter is not yet established in babies.

27.Urethra passes from inferior bladder to external urethral orifice. It empties in the vulva of females and is about 1 1/2 inches long and passes through the penis in the male and is about 8 inches long.


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