Chapter 18: Urinary System

what is glomerular filtrate made up of?

-H2O -small molecules: glucose, NaCl, amino acids, K+, HCO3, -waste: urea and creatinine

urethra

-continuation of neck of bladder -proximal and distal ends are both sphincters -lined with transitional epithelium

ureters

-continuous with renal pelvis - 3 layers: transitional epithelium (inner), smooth muscle layer (middle - contract urine down), fibrous CT (outer - provides strength and support)

What are the 5 main functions of the kidneys?

1. filtration of waste 2. H2O homeostasis 3. acid/base balance 4. RBC homeostasis 5. regulate BP

what are the three methods of waste elimination?

1. filtration: filters out blood that passes through the kidneys 2. reabsorption: body reabsorbs useful things into peritubular capillaries 3. secretion: body secretes additional waste into tubules from the blood

What percentage of blood goes to the kidneys with each heart beat?

25%

What hormone is regulated by the kidney?

ADH

Which two hormones play a major role in the control of the amount of water contained in urine?

ADH and aldosterone

antiduretic hormone (ADH)

Hormone made within the pituitary gland that travels to kidney via blood - regulates water reabsorption - stops urination -receptors are located in DCT & collecting ducts

aldosterone

Hormone that stimulates the kidney to retain sodium ions and water and is made within the adrenal gland

Where does secretion occur?

PCT -uric acid -ammonia -antibiotics & other medications DCT -K+ -H+

Glomerular capillaries are a continuation of the

afferent arterioles.

What three substances are eliminated from the body through tubular secretion?

ammonia, hydrogen, potassium

what is the path of urine drainage?

collecting duct, papillary duct, minor calyx, major calyx, renal pelvis, ureter, urinary bladder

macula densa cells

constantly monitor NaCl concentrations in blood - when NaCl levels decrease, BP decreases which sends a message to the juxtaglomerular cells to release renin (start of RAAS)

A renal corpuscle is located in the renal

cortex

The outermost layer of the kidney is the

cortex The cortex is the layer that is visible grossly in an intact kidney after the capsule has been removed. The hilus is the indented area on a bean-shaped kidney where the blood vessels enter and leave the kidney and the ureters leave the kidney.

The right kidney sits __ to the left kidney

cranial

Which portion of the renal segment is under ADH and aldosterone stimulation?

distal convoluted tubule

Location of ureters

dorsal, caudal surface partially found in both the parietal peritoneum and retroperitoneal space

What two substances are normally 100% reabsorbed in the PCT?

glucose and amino acids

Where do blood vessels, lymph vessels, and nerves enter and leave the kidney?

hilus

Which two ions can the kidney preserve or excrete to regulate the blood pH?

hydrogen and bicarbonate

The medulla of the kidney is made up of mostly

loops of henle

polyuria

lots of urine

The collecting system in the kidney is responsible for __________

making final adjustments to the sodium ion concentration and volume of urine

When antidiuretic hormone levels rise, the distal convoluted tubule becomes __________.

more permeable to water; water reabsorption increases

what is secretion?

movement of wastes from the blood stream (peritubular capillaries) into the PCT/DCT tubules

secretion

movement of wastes from the bloodstream into PCT and DCT -PCT secretes uric acid, ammonia, and meds -DCT secretes K+ and H+ ions -loop of henle ammonium and urea

The basic functional unit of a kidney is the

nephron

Oxygen transfer to the cells of a nephron takes place in the

peritubular capillaries. Peritubular capillaries surround each nephron. An afferent glomerular arteriole brings oxygenated blood into the glomerulus. An efferent glomerular arteriole carries blood (still oxygenated) away from the glomerulus. The glomerular capillary tuft is where fluid is filtered out of blood but no oxygen exchange takes place.

What are fenestrations?

pores in the capillary endothelium that help transfer plasma out of the capillaries. They are large and allow more fluid to leave - this fluid is called glomerular filtrate

Most of the nitrogenous waste in the body is a result of

protein metabolism Proteins are broken down into amino acids and ammonia, which contain nitrogen, a waste product of amino acid metabolism. Carbohydrate metabolism produces glucose. Erythrocyte breakdown produces heme and globin. Fat metabolism produces fatty acids.

60 to 70 percent of the water is reabsorbed in the __________.

proximal convoluted tubule

What is the primary site of nutrient reabsorption in the nephron?

proximal convoluted tubule

Where does filtration occur?

renal corpuscle (glomerulus) --> it produces a fluid called glomerular filtrate

What are the four parts of a nephron?

renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule

oliguria

small frequent urination

Where does reaborption occur?

the PCT to peritubular capillaries reabsorbs 100% glucose and amino acids & 80% of everything else

The renal corpuscle consists of __________.

the glomerular capsule and the glomerulus

Contraction of the muscular bladder forces the urine out of the body through the __________.

urethra

reabsorption

movement of useful things back into the bloodstream from PCT and DCT -PCT absorbs 100% glucose and amino acids and 80% of Na, Cl, K+, HCO3, H20, creatinine and urea -DCT absorbesa little more H20 and NaCl -Loop of Henle absorbs Na, Cl, and H20

What is the primary site in the nephron where the loss of water, sodium, and potassium ions is regulated?

nephron loop and collecting duct

The term for a condition where very little urine is being passed is

oliguria

The high blood pressure in glomerular capillaries forces some __ to leave the blood

plasma The plasma becomes glomerular filtrate after it leaves the blood. Plasma is mostly water, but there are solutes dissolved in the water. Red blood cells don't pass through the capillary walls.

What is the expanded, funnel-shaped structure in the kidney leading to the ureter?

renal pelvis

Because the kidneys sit between and peritoneum and the dorsal abdominal muscles, they are considered

retroperitoneal - Retroperitoneal means "behind the peritoneum" and indicates that the kidney isn't covered with visceral peritoneum. Intrahepatic means "within the liver." Intramuscular means "within a muscle." Retrorenal means "behind the kidney."

diabetes ins

this happens when there is very low or no ADH -associated with issues within the pituitary gland and polyuria

The ureters are lined by what kind of epithelium, which allows them to be stretched when undergoing peristalsis and moving urine?

transitional

The openings of the urethra and the two ureters mark an area on the internal surface of the urinary bladder called the __________.

trigone

diuresis

urination

mucturition

urination

What is the purpose of the stretch receptors found within the bladder?

whenever the bladder fills to a certain point, the stretch receptors will send a message to the spinal cord which will then send a message back to the detrusor muscles to contract -this is how one develops voluntary control of urination

The __ is a tuft of capillaries that filters blood in the first stage of urine production.

glomerulus

What results from the effect of aldosterone along the DCT, the collecting tubule, and the collecting duct?

increased conservation of sodium ions and water

What is the correct order of organs of the urinary system from cranial to caudal

kidneys, ureters, urinary bladder, urethra The kidneys are located in the dorsal part of the abdomen. The ureters enter and leave the kidney on the medial side at the hilus. Urine is constantly being produced by the kidneys and sent down through the ureters into the urinary bladder for storage until it is eliminated. The neck of the bladder extends caudally from the sac into the pelvic canal, and joins the urethra.

Aldosterone stimulates ion pumps along the distal convoluted tubule (DCT), the collecting tubule, and the collecting duct, causing __________.

a reduction in the number of sodium ions lost in the urine

A kidney can slowly lose nearly __ of its functional ability to make urine before clinical signs of renal failure appear.

67% -Roughly two thirds of kidney function can be gone before clinical signs of renal failure appear. Below 67% loss the animal would slowly be losing renal function but the other kidney and what's left of this kidney will compensate. More than 90% loss is not compatible with life.

anuria

absence of urine

What hormone regulates the kidneys sodium reabsorption?

aldosterone

The BUN is a measure of

blood urea nitrogen. The test measures how much urea nitrogen is in the blood to see how well the kidney is removing the waste product ammonia (containing nitrogen) from blood

ADH stimulates the reabsorption of water in __________.

both the distal convoluted tubule and the collecting system

What is the triple-layered muscle responsible for urinary bladder contractions?

detrusor

Location of the bladder

empty: pelvic canal (completely for large animals and mostly in small animals) full: extends into the abdomen - thin walled and easy to rupture

What hormone is produced by the kidney

erythropoietin

he thin segments in the nephron loop are __________.

freely permeable to water and relatively impermeable to ions and other solutes

What is the difference between glomerular filtrate and tubular filtrate?

glomerular filtrate that leaves the glomerular capillaries in the capsular space inside the renal corpuscle the tubular filtrate is when the GF enters the PCT to the DCT

What is the outward pressure forcing water and solute molecules across the glomerulus wall?

glomerular hydrostatic pressure