Portage Learning: A&PII - Module 7

Trace the flow of blood through the vessels of the kidney from renal artery into the glomerulus and back to the renal vein.

(1) Renal artery, (2) Segmental artery, (3) Lobar artery, (4) Interlobar artery, (5) Arcuate artery, (6) Interlobular artery, (7) Afferent arteriole, (8) Glomerular capillaries, (9) Efferent arteriole, (10) Peritubular or Vasa recta capillaries, (11) Interlobular vein, (12) Arcuate vein, (13) Interlobar vein, (14) Renal vein

What is the normal range of COP?

25-32mmHg.

What is the concentration of the filtrate in the PCT vs. the bottom of the loop of Henle?

300 mOsm/L; 1200 mOsm/L

About what percentage of Na+ is reabsorbed in the PCT? The loop of Henle? The DCT?

65%; 25%; 10% (DCT reclaims nearly all when necessary)

Describe the urinary bladder. Compare male and female locations.

A hollow, muscular, elastic pouch that receives, and stores urine excreted by the kidneys before disposal through the urethra. In males, the base of the bladder lies in front of the rectum and behind the pubic symphysis. In females, the bladder sits below the uterus and in front of the vagina, so the maximum capacity of the bladder is lower in females than in males.

Describe the action of ADH.

ADH inhibits urine output by increasing the number of channels in the cells of the collecting ducts. Increasing the channels allows water to pass easily from the filtrate and move into the surrounding interstitial space, eventually returning to blood circulation. Water rapidly leaves the filtrate through the channels in the collecting ducts opened by ADH. ADH retains up to 99% of the water in filtrate, and the kidneys excrete a very small volume of highly concentrated urine.

About how many gallons are filtered vs. excreted as urine?

About 47 gallons are filtered, and only 0.5 are excreted as urine.

The ____glands are located on top of each kidney.

Adrenal glands

Once circulating angiotensin II reaches the adrenal cortex, it causes the release of the hormone ____.

Aldosterone

Describe the mechanisms of aldosterone.

Aldosterone increases Na+ reabsorption through the excretion of hydrogen ions (H+). Sodium ions are pumped out of the filtrate while hydrogen ions are pumped inside for excretion. Because water follows salt, Na+ reabsorption also causes water reabsorption. A second action of aldosterone is to increase potassium secretion through sodium-potassium pumps. Na+ is pumped out of the filtrate to be returned to the blood while potassium (K+) is excreted in urine.

What is an anion?

An anion is a negatively charged ion.

What are the three major chemical buffer systems in the body?

Bicarbonate buffer system for interstitial and plasma fluids; Phosphate buffer system in the urine and intracellular; The protein system is the main buffer of the intracellular fluid.

What is Colloid osmotic pressure (COP)?

COP is dependent on the amount of proteins in the plasma. COP opposes blood hydrostatic pressure by driving fluids back into the capillary beds.

What is the principal method through which acids enter the human body?

Cellular metabolism (chemical reactions inside a cell to maintain life)80.

________are found in the cortex region of the kidney, except for a portion of their loop of Henle which extends into the medulla. ______pass deeply into the medulla because of their location and their longer loops of Henle.

Cortical nephrons; juxtamedullary nephrons

What is countercurrent flow?

Countercurrent flow is the movement of fluids in opposite directions through adjacent channels.

What are diuretics?

Diuretics are substances that act on the nephron to increase urinary output.

True or False: ADH increases water output.

False

True or False: The concentration of urea is relatively low in the distal convoluted tubule and the cortex regions of the collecting ducts because the tubules in the cortex are permeable to it.

False

True or False: The descending and ascending regions of the loop of Henle have the same reabsorption characteristics.

False

True or false: all reabsorption occurs in the renal tubules by diffusion.

False: Some ions require active transport.

True or False: A solution has a pH of 0, which is alkaline.

False: The closer to 0, the more acidic a solution.

What happens to cause hyperventilation? hypoventilation?

If blood pH begins to fall (becomes more acidic), the respiratory center is excited, causing hyperventilation. If blood pH begins to rise (become more alkaline), the respiratory center is depressed, causing hypoventilation.

What happens if the GFR is too slow? too fast?

If flow is too rapid, needed substances cannot be adequately reabsorbed. If flow is too slow, nearly all the filtrate is reabsorbed, including most of the wastes that should be excreted.

What happens in severe acidosis?

In severe acidosis the blood pH drops below 7.0, and the central nervous system is markedly depressed causing coma and imminent death.

What happens in severe alkalosis?

In severe alkalosis the blood pH rises above 7.8, and the nervous system is markedly excited causing extreme nervousness, muscle contraction, convulsion, and death due to cessation of breathing.

Where does the greatest amount of renal tubular reabsorption occur?

In the cells of the proximal convoluted tubule (PCT).

What is incontinence?

Incontinence is the inability to control micturition voluntarily.

Describe the loop of Henle.

Initially the loop of Henle has the descending limb followed by the ascending limb. The descending limb allows water loss and the ascending limb allows salt (NaCl) loss.

Describe the three layers of the ureter wall.

Inner transitional epithelium middle longitudinal and circular muscle outer fibrous connective tissue.

Water is found in what two main compartments?

Intracellular and extracellular.

Describe the distal convoluted tubule.

It allows for hormonally controlled reabsorption of water and solutes. Mostly the distal convoluted tubule is responsible for the secretion of unwanted substances.

What is capsular pressure?

It also opposes blood hydrostatic pressure and drives fluid back into the glomerular capillaries.

What is the GFR?

It is an amount of blood filtered by the glomerulus over time.

Describe the shape, weight and location of the adult kidney.

It is bean-shaped, about the size of a can of soup and weighs about 5 ounces. The right kidney lies slightly lower than the left because of the liver's location. They are located between T-12 and L-3 vertebra.

What is the hormonal control mechanism for the renal flow?

It is called the renin-angiotensin-aldosterone (RAA) system. *The RAA system has more effects in the body than are discussed in the module text. You will be responsible for knowing what is discussed in the text for the RAA system. The RAA system figure in the module goes into supplemental details about other effects in the body.

Describe the structure of the renal corpuscle

It is composed of the glomerulus, a network of tiny blood capillaries surrounded by the glomerular (Bowman's) capsule, a double-walled simple squamous epithelial cup.

Describe the proximal convoluted tubule

It is specialized to reabsorb water and many solutes from the glomerular filtrate into the low-pressure peritubular capillaries which surround the renal tubule as well as secrete certain unwanted substances.

What is Blood hydrostatic pressure (HP)?

It is the amount of pressure found inside the blood in the capillaries, driving fluids out of the glomerular capillary.

Describe the process of micturition.

Micturition is the act of emptying the bladder. As urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine. The urge to urinate usually starts when about 200 ml of urine has accumulated. This causes the detrusor muscle to contract and the internal sphincter to relax forcing stored urine through the internal sphincter into the upper part of the urethra. A person can consciously resist this initial urge to urinate because the external sphincter is voluntarily controlled. As the bladder continues to fill, the desire to urinate becomes stronger. Eventually, if the amount of urine reaches 100% of the bladder's capacity, the voluntary sphincter opens, and micturition occurs involuntarily.

Calculate the net filtration pressure for a patient with a blood hydrostatic pressure of 60mmHg, a colloid osmotic pressure of 32mmHg, and a capsular pressure of 18mmHg.

Net filtration pressure = (Outgoing forces - incoming forces)= HP- (COP + Capsular pressure)=60mmHg - (32mmHg +18mmHg))= 10 mmHg (net outward pressure)

What are the normal blood serum levels? (for pH, PCO2, HCO3-)

Normal pH = 7.35-7.45, Normal PCO2 = 35-45 mm, Normal HCO3- = 22-26 mEq/L

The renal medulla is divided into sections called _____.

Pyramids

Which mechanism (above) is the kidney controlling its own rate of flow?

Renal autoregulation

What are the three mechanisms that regulate renal flow?

Renal autoregulation, nervous system control, and hormone control.

The _____ is a continuous outer region with several cortical columns.

Renal cortex

Which system has the largest impact on the level of pH in the blood?

Renal system (kidney secretion or retention of bicarbonate ion).

When blood pressure drops, the enzyme ____ is released by the juxtaglomerular (JG) cells of the nephron.

Renin

What is secretion?

Secretion involves substances entering the filtrate from the surrounding fluid, allowing for the elimination of undesirable substances

What causes an increase in the GFR? a decrease?

The GFR is increased by an increase in the arterial blood pressure in the kidneys. The GFR and is decreased by an increase in glomerular osmotic pressure most often caused by dehydration.

What causes water and solutes to leave the glomerulus?

The afferent arteriole, which is fed by the interlobular artery, is much larger in diameter than the efferent arteriole. The difference in diameter causes an extremely high blood pressure in the glomerular capillaries, forcing water and solutes out of the blood, thus making filtration possible. Water and solutes leave the glomerulus, enter the glomerular capsule, and subsequently flow into the renal tubule.

What is a nephron?

The basic structural and functional unit of a kidney. The function of the nephron is to control the concentration of water and soluble materials by filtering the blood, reabsorbing needed materials and excreting the rest as urine.

Describe the bladder when it is full and when it is empty.

The bladder is very elastic, collapsing into it a pyramidal shape when empty. As it is filled by urine, the bladder swells and becomes pear-shaped, rising in the abdominal cavity.

How do the cardiovascular baroreceptors control the nephron?

The cardiovascular baroreceptors are in the aorta and carotid arteries under the control of the vagus and glossopharyngeal cranial nerves. If blood volume (and consequently blood pressure) rises, the baroreceptors inhibit sympathetic nervous system signals to the kidney, dilating the afferent arterioles which carry blood to the glomerulus. This causes a dramatic increase in the filtration rate, increasing the output of water and Na+ which reduces blood volume to quickly normalize the pressure.

Discuss the differences between the male and female urethra.

The female urethra is shorter and only carries urine while the male urethra is about 5 times longer and carries both urine and semen from the body.

What are the three types of capillaries associated with nephrons and their function?

The glomerular capillaries, the peritubular capillaries and the vasa recta. The glomerular capillaries (glomerulus) are highly coiled capillary beds formed from the afferent arteriole, leaving as the efferent arteriole. The peritubular capillaries closely follow the renal tubules and drain into the interlobular vein. the vasa recta which follow the loops of Henle in the juxtamedullary nephrons of the medulla.

What is urinary retention?

The inability to expel stored urine

Describe the two sphincters of the bladder.

The involuntary-controlled internal urethral sphincter is located near the bladder and keeps the urethra closed to prevent urine from leaving the bladder. The voluntary-controlled external urethral sphincter, composed of skeletal muscle, surrounds the urethra as it passes through the pelvic floor.

How many times a day does the kidney filter through the blood plasma?

The kidneys filter the entire blood plasma volume about 60 times each day

What is the normal pH of arterial blood?

The normal pH of arterial blood is between 7.35 and 7.45.

Describe the three layers of the bladder.

The outer adventitia is fibrous connective tissue, the middle layer is a muscular layer known as the detrusor muscle with inner and outer longitudinal layers and middle circular layer, the inner mucosal layer is composed of transitional epithelium.

What is reabsorption?

The process of fluid and substances moving from the filtrate back into the blood is called reabsorption.

What are the three regions of the male urethra?

The prostatic urethra which runs within the prostate gland, the membranous urethra which runs within the urogenital diaphragm and the spongy (penile) urethra.

Describe the three layers of protective tissue that surround the kidney.

The renal capsule is a tough fibrous outer skin of the kidney which protects it from injury and infection. The middle adipose capsule protects the kidney from trauma. The outer renal fascia is dense fibrous connective tissue which keeps the kidney in place.

Describe the renal pelvis.

The renal pelvis constitutes a funnel-shaped tube that connects to the ureter as it leaves the hilus.

How does the respiratory center control pH?

The respiratory center has chemoreceptors in the medulla which monitor the CO2 in the blood. Bicarbonate is the form in which carbon dioxide is transported in the blood plasma

What prevents blood cells from leaving the glomerular capillaries?

The size of the capillary fenestrations prevents passage of blood cells and most blood proteins from leaving across the filter.

The renal tubule is made of:

Three parts: the proximal convoluted tubule (PCT), the loop of Henle, and the distal convoluted tubule (DCT).

Each nephron consists of:

Two parts: the glomerular capsule (renal corpuscle) and the renal tubule.

______are sphincters located where the ureters enter the bladder.

Ureterovesical valves

Describe normal urine.

Usually clear and pale to deep yellow in color depending on the body's degree of hydration. The normal range of urine pH is 4.5 to 8.0. Urine contains about 95% water with about 5% of solutes of varying amounts.

Describe the impact of weak acids on a solution.

Weak acids do not significantly contribute to the pH of a solution because in this form, H+ is tightly bound and cannot dissociate to become free H+.

When an osmotic gradient is isosmotic, what does this mean?

When the fluid outside and inside have the same osmotic concentrations.

Describe the nervous system control of the renal flow.

When the nervous system takes over regulation, the afferent arterioles diameter is narrowed by sympathetic nerve fibers. The release of the hormone epinephrine by the adrenal medulla causes a decrease in renal blood flow and decreases the GFR.

Once water and solutes leave the blood and enter the glomerular capsule it is called ____.

filtrate

What are the three steps of urine formation?

filtration, reabsorption and secretion.

Angiotensinogen is a pre-enzyme produced by the ___ and freely circulates in the blood.

liver

In the ____, angiotensin I is converted to ____.

lungs; angiotensin II

ADH is secreted by the ____.

posterior pituitary

Input from the _______ adjusts the diameter of the renal arteries thereby regulating renal blood flow.

sympathetic nervous system

A vertical cross section shows what three regions inside the kidney?

the cortex, the medulla, and the pelvis

The urinary system has ____ kidneys, _____ ureters, and _____ bladder.

two, two, one

Both ureters open into the bladder via the _____.

ureteral orifices

Urine is carried from the kidneys to the bladder by thin muscular tubes called ____.

ureters

The bicarbonate buffer system is composed of _____and _____.

weak carbonic acid (H2CO3); bicarbonate ion (HCO3-).