BioLab#10 Quiz

How would each of the solutions affect a Red Blood Cell?

0.9% NaCl- not a large change, minimal shrinkage 150mMoles CaCl2- hypertonic solution, cell will shrink (crenation) 7% glucose- hypertonic solution, cell will shrink 1% MgCl2- minimal shrinkage Hypotonic solution- cause lysing of cell (bursting)

Anti-diuretic Hormone (ADH, Vasopressin

secreted by the posterior pituitary gland in response to an increase in the osmolarity of the blood plasma. This increase may result from dehydration. The release of ADH stimulates the kidneys to retain more fluid in the blood and excrete less in the urine. A dehydrated person will then drink more and secrete less urine, also increasing blood volume.

Atrial Natriuretic Peptide (ANP)

secreted by the right atrium of the heart in response to stretching caused by increased blood volume. This also promotes excretion of Na+ and thereby water into the urine, thus decreasing blood volume.

What tissue types are associated with the urinary bladder and the renal tubules?

- the urinary bladder is lined with transitional epithelial tissue that is able to stretch significantly to accommodate large volumes of urine - renal tubules: simple cubodial epithelium tissue forms the tubules. Cubodial tissue is classified as simple, since it consists of only a single layer of cells - Simple squamous

Briefly describe the three basic functions of the kidney.

1.) Filtration: Fluid in the blood is filtered into the tubule system, leaving cells and large protein in the blood and a filtrate composed of water and all of the blood solutes. This filtrate is modified by the rest of the kidney to produce urine for excretion. 2.) Reabsorption: Reabsorption is the selective movement of important solutes, such as glucose, amino acids, and a variety of inorganic ions, out of the filtrate in the tubule system to the extracellular fluid, then back into the bloodstream via peritubular capillaries. The process of reabsorption can utilize active or passive processes depending on the solute. Water is also reabsorbed, and this can be controlled to regulate the amount of water loss. 3.) Secretion: Secretion is the movement of substances from the blood into the extracellular fluid, then into the filtrate in the tubule system. Unlike reabsorption, which preserves substances in the body, this adds to what will be expelled from the body and can be used to remove toxic substances.

What is the function of the vasa recta? Where is it located?

Acts as a counter current exchange - Rect = Straight, Vasa = Vessels. Long vessels parallel to long loops of Henle. - Arises from efferent arterioles of the juxtamedullary nephrons. - Reabsorbs water and solutes and helps maintain NaCl gradient between cortex and medulla - Help return solutes and water reabsorbed in medulla to bloodstream - Blood flows slowly, water flows out of the descending limb, and Na & Cl move in - Afferent and efferent - Varying levels of osmolarity- higher towards medulla - Cortical nephrons

Aldosterone, Renin, Angiotensin

Aldosterone is secreted by the adrenal cortex in response to the renin, angiotensin cycle. When blood flow through the kidneys decreases, a specialized group of cells located in juxtamedullary apparatus of the kidneys that initiate release of the enzyme renin into the blood. It splits the inactive polypeptide Angiotensin I from the larger plasma protein Angiotensinogen (produced by the liver). Angiotensin I is converted by ACE (angiotensin converting enzyme found in capillary endothelial walls) into Angiotensin II. This stimulates vasoconstriction throughout the body and also stimulates the release of aldosterone by the adrenal cortex. Aldosterone causes kidneys to promote the retention of Na+ and the subsequent retention of water in the blood, thereby increasing blood pressure.

Hormones Associated with the Urinary System

As you know, blood pressure is one of the body's most highly defended variables because there must always be sufficient pressure to supply the brain, heart, organs and all other tissues with oxygen. The hormones which are listed below contribute to this regulation and they have been discussed in previous labs. Although they are secreted by different glands or organs, they all work through the kidney in some way.

how osmolarity is calculated

Grams/liter X number of ions formed X 1000 = osmolarity in mOsM M.W. Osmotic Pressure = Conc. (in mMoles) X No. of dissociated species (ions) X 19.3 mm Hg

Overview of Kidney Anatomy

The kidneys are located in the abdominal cavity, one to either side of the midline (see page 499 in Mosby's Handbook, or look at an Anatomy text in the rear of the lab). They are referred to as retroperitoneal because they lie behind the peritoneal lining of the abdominal cavity. The kidneys are supplied with blood by the renal arteries, which branch off the descending abdominal aorta.Blood is drained from the kidneys by the renal veins, which then drain into the inferior vena cava as it goes toward the heart. Urine forms in the nephrons and leaves the kidneys via two ureters which connect with the floor of the bladder. A single urethra then drains the bladder. The urethral opening and the two openings of the ureters form an anatomical landmark called the urinary trigone, located on the floor of the bladder. A diagram of the internal anatomy of the kidney is shown on page 508 of Mosby's Handbook and on the models at the rear of the lab. Please locate the structures listed below on the lab models. Renal artery, renal vein, ureters, renal capsule, cortex, medulla, major calyx, minor calyx, renal pyramid, renal column, renal pelvis

Osmolarity and Osmotic Pressure

The primary function of the kidneys is to maintain homeostasis through regulation of the fluid balance between the intracellular and extra-cellular compartments of the body. This is achieved through filtration of the blood, reabsorption of water and salts, and secretion. The concentration of solutes in the blood creates an osmotic pressure. Osmotic pressure is measured in milliosmoles (mOsM) and it can be defined as the potential pressure developed by a solution separated from pure water by a differentially permeable membrane. The higher the solute concentration of the solution, the greater its osmotic potential. Since water always moves down a concentration gradient, it will move into or out of the RBC based upon the solute concentration of the solution it is in. Blood normally has an osmolarity of approximately 300 mOsM. Solutions such as 0.9% NaCl (.155 M) have a similar osmotic concentration and may be added to the blood without consequence to the RBCs. Usually, solutions having an osmolarity within ten percent of 300mOsM will not cause any significant change to the RBC.

The Nephron, Functional Unit of the Kidney

There are two types of nephrons found in the kidneys. The first is a cortical nephron, named because it lies mostly within the kidney cortex, and the second is a juxtamedullary nephron, named because it lies closer to the corticomedullary junction. The differential placement of these two nephrons allows the kidney to produce dilute or concentrated urine, depending on conditions within the body. Cortical nephrons have a peritubular capillary network surrounding the tubules while the juxtamedullary nephrons have the vasa recta. Use the models and the Mosby's to locate the following structures: Bowman's capsule, glomerulus, proximal convoluted tubule, loop of Henle and the descending and its ascending limbs, distal convoluted tubule, collecting duct, peritubular capillaries, vasa recta, afferent arteriole, efferent arteriole. The function of the kidney is to eliminate certain toxins, waste products, and excess water from the blood. This is accomplished through three separate processes: glomerular filtration, tubular secretion and tubular reabsorption.

Bladder and Urinary Passages

When the ureters leave the kidneys, they travel down to where they enter the floor of the bladder, posterior to the exit of the urethra. The specialized epithelium which lines the bladder and urinary passages is called transitional epithelium. When the bladder is empty, the cells of this epithelium are stacked on top of each other with the individual cells having a somewhat domed appearance. As the bladder fills, the smooth muscle tissue of the walls stretches and the cells of the epithelium flatten out. Transitional tissue allows the bladder to fill and empty without being damaged. There are also two urinary sphincters which control the release of urine. The interior urinary sphincter is composed of smooth muscle and the external sphincter is of skeletal muscle.