Urinary System Flashcards
Learn the urinary system!
What are the main structures that make up the urinary system? (4)
- Kidneys
- Ureters
- Bladder
- Urethra
What are the functions of the kidneys (4)
- FILTRATION: filters plasma constituents from blood.
- REABSORPTION: reabsorbs water and useful constituents from the filtrate.
- EXCRETION: excretes the excess filtrate.
- HOMEOSTASIS: maintaining the constant condition of the internal environment of the body
Where are the kidneys located?
- Dorsal part of the abdominal cavity on either side of the aorta and vena cava.
- Ventral to the first few lumbar vertebrae.
- Outside the peritoneal cavity attached to the body wall
What is the Renal Hilus?
The area of the kidney where blood vessels and nerves enter the ureter and lymphatics leave.
What is the Renal Pelvis?
The expanded origin of the ureter within the kidney.
What is the function of the renal pelvis?
To receive urine from the collecting tubules of the kidneys
What is the Medulla of the kidney?
- The portion of the kidney that is surrounding the renal pelvis.
What is the structure of the Medulla? What does it contain? (2)
The Medulla has a striated appearance due to radially arranged collecting tubules
Contains:
- Loops of Henle
- Collection tubules
What forms the basis of the renal pyramids?
The collection tubules in the medulla of the kidney
Where is the Cortex located?
Between the Medulla (inside) and the thin connective tissue capsule of the kidney (outside)
Where is the Medulla located?
- Below the cortex as the innermost portion of the kidney
What is located in the cortex of the kidney? (3)
- Renal Corpuscles
- Proximal convoluted tubule
- Distal convoluted tubule
What is the appearance of the Cortex and why does it appear that way?
Granular in appearance because fo the large number of renal corpuscles
How much blood does the kidney receive?
About one fourth (1/4) of the cardiac output.
Two renal arteries enter the kidney through the hilus and divide into a number of large branches. What are the names of the branches that the interlobular arteries become? (2)
- Arcuate arteries
2. Afferent arterioles
What is a glomerulus?
A capillary network within the kidney that is formed by the afferent arteriole branches
What do the afferent arterioles of the kidney become?
A capillary network that forms the glomerulus
What do the efferent arteriole branches of the kidney become once they have left the glomerulus?
They break up into a capillary network that surrounds the rest of the Nephron.
What are Arteriae Rectae?
Capillary networks around collecting tubules and loops of Henle in the kidney.
What is the functional unit of the kidney?
The Nephron
What structures does a Nephron include? (4)
- Glomerulus
- Glomerular Capsule (Bowman’s Capsule)
- Proximal Convoluted Tubule
- Distal Convoluted Tubule
What structures are involved in venous drainage of the kidneys? (4)
- Venae rectae
- Interlobular veins
- Arcuate veins
- Renal vein
Where does the lymph drain to from the kidneys?
The renal lymph nodes
What nerves supply the kidneys? (2)
- Sympathetic nerves from the renal plexus which follow blood vessels and terminate largely on glomerular arterioles.
- Vagus nerves may also supply the kidneys
What is the Ureter and what is it’s function?
- The ureter is a muscular tube running from the kidney to the bladder.
- Function: Carries urine from the kidneys to the bladder.
What is the structure and location of the Urinary bladder?
- A hollow muscular organ which varies in size and amount of urine it contains.
- When the bladder is empty it is thick walled, pear shaped and located on the floor of the pelvis
- When the bladder fills the wall becomes thinner and the bladder is displaced cranial toward the abdominal cavity.
What is the function of the urinary bladder?
To store urine received from the kidneys via the ureters before expulsion.
What controls the passage of urine from the bladder into the urethra?
the circular arrangement of muscle at the neck of the bladder which forms a SPHINCTER.
The neck of the bladder is continuous with what structure?
The urethra
What type of tissues line the pelvis, ureter, bladder and urethra? (1)
They are all lined with transitional epithelium
What are the two types of urethra?
- Penile urethra
2. Pelvic urethra
What is Micturition?
- the expulsion of urine from the bladder.
- a reflex activity stimulated by the distention of the bladder
How does Micturition occur?
reflex centers in spinal cord stimulated –> causes contraction of the muscle wall of the bladder by way of parasympathetic nerves.
How can reflex emptying of the bladder be prevented?
by voluntary control of the external sphincter surrounding the neck of the bladder.
What does the kidney regulate to ensure the homeostasis of the body? (5)
- water balance
- pH
- Osmotic pressure
- Electrolyte levels
- Concentration of many plasma substances
What is the Glomerular (Bowman’s) Capsule?
- the expanded blind end of the tubule in the nephron.
- almost entirely surrounds the nephron.
What does the visceral layer of the glomerular capsule do?
Surrounds the capillaries of the glomerulus
What is the parietal layer of the glomerular capsule continuous with?
- it is continuous with the convoluted tubule
What is a Renal (Malpighian) Corpuscle?
The complec formed by the glomerulus and inner and outer layers of the glomerular capsule
What is the function of the Renal Corpuscle?
To filter fluid from the blood
- about 100x as much fluid passes through this filter than is excreted as urine
In order for the Renal Corpuscle to filter effectively what conditions must be met and how are they met?
CONDITION: the blood pressure within the capillaries of the glomerulus must remain relatively high
ENSURED BY:
-the capillaries being on the course of an artery between and artery and a vein.
- the afferent and efferent arterioles are supplied with smooth muscle so they control the glomerular pressure.
where are juxtaglomerular cells located?
in afferent arterioles approaching the glomerulus
Where are Myoepithelial cells located and what do they do?
- They form a cuff around the renal corpuscle.
- They have characteristics similar to smooth muscle and epithelium.
- They produce renin
How many Nephrons does a single kidney hold?
approximately one million
How many nephron function at any one time?
one-fourth the total nephrons
What percentage of water is lost from the blood in the nephron and why?
About 20% of the water is lost from the blood so that it becomes more concentrated. Since it has a higher potential osmotic pressure it is better able to reabsorb water from the tubule.
What stimulates the production of renin? (4)
- Decrease in blood pressure in the afferent arteriole
- decrease in plasma sodium concentration.
- decrease in distal tubular osmolarity
- Stimulation of sympathetic fibres supplying afferent arteriole.
What does renin act on?
alpha globulin - angiotensinogen to produce angiotensin.
What is the function of angiotensin? (2)
- acts as a vasoconstrictor to increase blood pressure
2. acts on adrenal gland to secrete aldosterone which acts on kidney to conserve sodium ions.
What is the proximal convoluted tubule?
- The longest and most winding portion of the nephron.
- Forms most of tissue of renal cortex.
- made up of columnar or cuboidal epithelium
What are the functions of the proximal convoluted tubule?
- reabsorption of most of the constituents of the glomerular filtrate that are needed by the animals body.
- secretion of waste products from the blood into the fluid passing through the lumen of the tubule.
What tissues make up the loop of henle? (2)
- thin simple squamous epithelial cells in the descending limb
- thick cuboidal epithelial cells in the ascending limb
What is the distal convoluted tubule?
A tube (shorter than the proximal convoluted tubule) extending from the terminal protion of the loop of henle to the collecting tubule.
What are the initial collecting tubules of the distal convoluted tubule called and what do they do?
Arched tubules - empty into the straight collecting tubules
What are the straight tubules of the distal convoluted tubule unite to form and what does it do?
Unite to form papillary ducts - empty into the pelvis of the kidney
How does the kidney achieve homeostasis?
by filtering large quantities of plasma and small molecules through the glomerulus and reabsorbing varying ammounts of each substance. reabsorption can be either passive or active (tubular transport)
What factors effect the actions of the kidneys? (4)
- The composition of the blood
- arterial blood pressure
- hormones
- the autonomic nervous system
How does the composition of blood effect the actions of the kidneys?
dilution of plasma proteins causes diuresis (increased excretion of urine), including greater excretion of water, Na, Cl, Bicarbonate, etc. The low osmotic pressure of diluted blood inhibits the release of ADH.
How do hormones effect the actions of the kidneys?
ADH and Aldosterone (a sodium conserving hormone) act on the kidneys. Globular filtrate is influenced by these hormones.
What are osmoreceptors and what do they do?
They are receptors in the hypothalamus which cause the release of ADH from the posterior pituitary whenever the osmotic pressure of the blood in the carotid artery increases.
What is glomerular filtrate?
the fluid and fluid constituents that pass from the blood in the glomerulus into the lumen of the glomerular capsule.
What is the composition of filtrate in the glomerulus?
essentially the same as that of blood plasma except it should contain no erythrocytes, plasma proteins or fatty acids (bound to protein)
What substances are filtered in the glomerulus? (9)
- glucose
- amino acids
- urea
- uric acid
- creatinine
IONS: - Na
- Cl
- K
- H
What is the ammount of glomerular filtrate proportional to?
the filtration pressure.
What is filtration pressure in the glomerulus a result of?
differences in the hydrostatic and osmotic pressure in the glomerulus as compared with the same types of pressue in the lumen of the glomerular capsule.
what is the hydrostatic pressure in the glomerular capillaries in a man?
60mm of Hg
What is the colloidal osmotic pressure in the capillaries?
32mm of Hg
what is the pressure in the glomerular capsule?
18mm of Hg
What is the colloidal osmotic pressure in the glomerular capsule?
0mm of Hg
What is the filtration pressure forcing fluid from the glomerulus in to the glomerular capsule?
10mm of Hg
What is the glomerular filtration rate?
the rate at which the fluid and constituents leave the blood and become filtrate
Glomerular filtration rate is directly proportional to what?
filtration pressure
What happens when the afferent arterioles are constricted?
glomerular filtration rate decreases
what happens when the afferent arterioles dilate?
glomerular filtration rate increases
what happens when the kidneys receive sympathetic stimulation?
smooth muscles constrict and glomerular filtration rate decreases. Shut down of filtration may occur.
Why does shut down of filtration occur as a result of sympathetic stimulation?
- hemorrhaging or shock may be occurring
- an animal can better afford loss of renal function for a few hours than it can the loss of brain, heart and liver function.
What is necrosis?
the loss of blood supply or renal failure.
What is plasma clearance?
expresses the degree to which any substance is removed from the plasma by the kidneys and excreted in the urine.
what is used clinically as a measure of kidney function? why?
clearance of creatinine
- plasma concentration of creatinine and the total daily excretion remain constant
- if functional nephron decreases (disease), then clearance of creatinine decreases and its plasma level increases
plasma clearance of any substance =
(mg/ml of substance in urine x ml urine/min) / (mg/ml of that substance in plasma)
what is the process of reabsorption?
if the materials are carried from the lumen of the tubule to the interstitial fluid
What is the process of secretion or excretion?
if materials are carried from the lumen of the tubule to the lumen.
what is Tubular Maximum (TM) for reabsorption or secretion of a substance?
essentially, each substance has a threshold and the excess of a reabsorbable substance above threshold remains in the filtrate to be excreted in the urine.
Regulation of sodium ions in the kidney mainly occurs by the action of what hormone?
Aldosterone
how do the Kidneys maintain the proper concentration of sodium ions in the extracellular fluids of the body
the kidneys excrete the same ammount of sodium ions that is ingested daily in the diet. as long as the animal’s sodium concentration is in equilibrium.
When is Aldosterone secreted? (3)
- Plasma sodium concentration decreases
- plasma potassium concentration increases
- plasma volume or cardiac output decreases and stimulated the sympathetic nervous system
How does plasma sodium or potassium concentrations effect when aldosterone is secreted?
- the changes have a direct effect on the secretory cells of the zona-glomerulosa of the adrenal cortex as the blood flows through the adrenal gland.
- when Na concentration is deficient in the plasma or in the distal convoluted tubule at the level of the juxtaglomerular apparatus or when the blood pressure decreases and causes a decrease in the blood flow through the renal arterioles.
Renin is what type of enzyme?
a proteolytic enzyme
what does the increased reabsorption of sodium salt mean?
more water is osmotically reabsorbed as well which helps, somewhat, in restoring blood volume.
What does aldosterone cause in relation to Na and K
Na gets reabsorbed when aldosterone is active and potassium gets excreted in order to establish a normal sodium to potassium ratio in the extracellular fluid.
The balance between sodium and potassium is crucial for maintaining what major normal body functions? (3)
- nerve conduction and stimulation
- muscle contraction
- heart function
what is produced in large amounts in the cells of an animals body as a result of metabolism?
intermediary acids
Enzyme activity and metabolic processes require control of what for optimal function?
control of pH within narrow limits
what is the normal average pH of arterial blood? Venous blood?
Arterial blood = 7.4
Venous blood = 7.35
What happens when the pH of arterial blood falls below 6.8?
the animal dies in coma because the high carbon dioxide concentration (acidosis) depresses the CNS neurons.
What happens when the pH of arterial blood reaches 7.8 or more?
death can occur from tetany of the respiratory muscles, because the high pH overexcites the CNS nerves, producing spasms and tetany.
in what ways does the body control pH levels? (3)
- BUFFER SYSTEMS: bicarbonates, phosphates and proteins
- BREATHING: pulmonary ventilation
- The kidneys excreting alkaline or acid urine as needed.
What is nephritis?
inflammation of the kidneys
What is nephrosis?
non-inflammatory kidney disease
What is albuminurea?
degeneration of tubules
What is Uremia?
urine in the blood - may occur in kidney disease is the kidneys are unable to remove enough of the usual constituents of urine from the blood.
What are Urinary Calculi?
stones found in any part of the urinary system. May develop in the pelvis and obstruct passage of urine through the ureter or they may develop in the bladder and interfere with passage of urine through the urethra.
What causes urinary calculi?
high mineral uptake, less water intake and low vitamin A levels.
what is Cystitis?
Inflammation in the bladder
what is Pyelitis?
inflammation in the pelvis?
What is Pyelonephritis?
inflammation of the pelvis and kidney
