Unit 6 - Urinary System Flashcards
What are the parts of the urinary system?
two kidneys
two ureters
the urinary bladder
urethra
What is the overall function of the urinary system?
- maintain homeostasis
- regulate the volume and composition of body fluids
- excrete unwanted material
- filtration, reabsorption, secretion
What are the four things excreted from the kidney?
nitrogen compounds
toxins
water
electrolytes
what is the main organ of the urinary system
kidney
What does the urinary system control in the blood?
volume and pressure
What ions in the blood does the urinary system control for blood levels?
Na+1, K+1, Ca+2, Cl-1
What ions in the blood does the urinary system control for the blood pH?
H+1, HCO3-1
What are some characteristics of the kidneys?
- paired reddish-brown organs
- filter plasma and plasma constituents from blood
- selectively reabsorb water and useful constituents
- excretes excess and waste products
Where are the kidneys located?
located in the dorsal part of the abdominal cavity, placed on each side of the aorta and caudal vena cava, ventral to the first few lumbar vertebrae
What is the basic anatomy of the kidney?
appear as a bean shape in most animals, covered by a fibrous connective tissue capsule
What is the function of the hilus?
area where blood and lymph vessels, nerves, and ureters enter and leave the kidney
What is the location of the hilus?
The indented area on the medial side of the kidney
Where is the renal pelvis located?
right at the base of the kidney tube
Where are the renal calyces located?
the inside tubes of the kidney tube
What are the functions of the renal pelvis and renal calyces?
structures responsible for directing the urine down the urethra, directs filtered urine to the renal pelvis
What is the renal medulla?
little muscle-looking bulbs at the end of the renal calyces
What is the function of the renal medulla?
regulate concentration of urine to renal calyces
What is the renal cortex?
Outer layer of the kidney, has a dark brown colour and presents a soft consistency
What is the difference between the lobes in kidneys through different species?
- The renal cortex of the equine, ovine, and caprine kidney lacks visible divisions into individual lobes
- The renal cortex of bovine kidney is externally divided into lobes (visible from outside of the kidney)
- The swine kidney lacks external divisions into lobes, but each lobe can be distinguished internally.
What does the renal cortex receive?
most of blood flow to the kidney
What is the renal cortex the location for?
most of the nephron (basic functional unit for the kidney)
Where are the renal pyramids located?
On the renal medulla
What is the renal lobe?
Renal medulla, together with the adjacent cortex will form the renal lobe
What is the calyx?
junction between renal medulla and renal calyces, cuplike extension of renal pelvis
What are renal columns?
sit between the renal pyramids
What are the 5 parts of the nephron?
loop of henle
renal corupscle
proximal convoluted tubule
distal consulted tubule
collecting duct
What is the renal corpuscle made up of?
glomerulus and bowmans capsule
What is the glomerulus?
a tuft of glomerular capillaries
What is the bowmans capsule?
double-walled capsule that surrounds the glomerulus
What is the inner layer of the bowmans capsule?
adheres closely to the surfaces of all glomerular capillaries
What is the bowmans capsule made out of?
podocytes - specialized endothelial cells that cover the outer surface of the glomerular capillaries
What are the afferent vs efferent arteriole functions?
afferent - bring blood towards the bowmans capsule
efferent - bring blood out of bowmans capsule
What is the unique characteristics of the podocytes in the bowmans capsule?
The podocytes covering the capillaries have spaces between them
Creates a permeable layer through which fluid and dissolved substances can pass during
filtration.
What is the function of the renal corpuscle?
filter blood in the first stage of urine production
What is the capsular space
space of the renal corpuscle that is continuous with the proximal convoluted tubule
What is the glomerular filtrate?
the fluid that is filtered out of blood
What is the proximal convoluted tubule?
- continuation of the capsular space of Bowmans capsule
- longest part of the tubular system of the nephron
What is the proximal convoluted tubule lined with?
lined by cuboidal cells with a brush border on their lumen side
What do the cuboidal cells and brush border on the proximal convoluted tubule do?
- Increases the cellular surface area exposed to the fluid
- Important to the reabsorption and secretion functions of the tubule
What is the major function of ht proximal convoluted tubule?
- reabsorb fluid, electrolytes and nutrients
- responsible for roughly 98% of glucose and 65% of sodium reabsorption
Where is the loop of henle located?
continues from the proximal convoluted tubule, descends into the medulla of the kidney, makes a U-turn, and heads back up to the cortex
What is a part of the descending part of the loop of henle?
has cuboidal epithelial cells with brush border, which is highly permeable to water and less permeable to solutes
What occurs at the U-turn of the loop of Henle?
wall becomes thinner, and the epithelial cells flatten and lose their brush border
What occurs in the ascending part of the loop of henle?
wall becomes thicker again, but the cells don’t regain the brush border, the thin part is highly permeable to sodium but impermeable to water
Where is the distal convoluted tubule located?
continuation of the ascending part of the loop of henle
What is the distal convoluted tubule made up of?
composed of simple cuboidal epithelium
What is the function of the distal convoluted tubule?
involved in reabsorption or excretion of bicarbonate and hydrogen ions to maintain blood pH
Where are the collecting ducts located in the nephron?
placed at the end of the distal convoluted tubule
What is the function of the collecting ducts in the nephron?
- carries a filtrate throught he medulla into the calyces, which lead to the renal pelvis
- play an important role in urine volume
- primary site of action of antidiuretic hormone (ADH)
What is the function of the antidiuretic hormone?
ADH, helps to control the amount of water and salt in the body
Where is the renal artery located?
enter the kidney at the hilus
What occurs in the Bowmans capsule in terms of gas exchange?
inside Bowmans capsule - oxygenated blood
no gas exchange in Bowmans capsule
when blood leaves capsule, gas will still be there, but other parts of blood is exchanged
What is the structure of the renal artery?
Subdivides into arterioles, until becomes the afferent glomerular arteriole
What do afferent arterioles do?
carry blood to the glomerular capillaries
What are glomerular capillaries?
continuation of the afferent arterioles
What does the efferent arteriole do?
blood plasma is filtered, and the blood leaves the capsule through the efferent arteriole
What is important to note about the O2 comp of the blood in the efferent arteriole?
Blood is still arterial blood at this point, because oxygen exchange hasn’t taken place yet
What are the peritubular capillaries?
capillaries that the efferent glomerular arterioles divide into
What is the function of the peritubular capillaries?
oxygen is transferred from the blood to the nephrons, compounds will be reabsorbed from the filtrate back to the bloodstream
What is the total steps of the urine flow through the kidney?
- blood enters the kidney through the renal artery
- the arteries divide into arterioles
- arterioles branch into capillaries at the nephrons
- place where blood is filtered, and urine formation starts
- filtered blood passes to the series of venules
- exits the kidney through the renal vein
- urine is collected into collecting ducts
- leaves the kidney via ureters
What are the steps to blood filtration?
- blood enters the glomerular capsule via afferent arteriole
- passes through a ball of capillaries (glomerulus)
- blood leaves the glomerular capsule through efferent arteriole
What is the size difference of the afferent and efferent arterioles?
afferent arteriole is larger than efferent arteriole
- creates blood flow with a large inlet with small outlet
- results in a very high hydrostatic pressure in the capillaries
What does the high pressure in the arterioles create?
high pressure drives the water and solutes from blood plasma through a filtration membrane into the capsular space of the nephron
What are fenestrations?
pores in the capillary endothelium, plasma passes through here
What is plasma made out of?
Water, inorganic ions, glucose, amino acids, metabolic waste
How does glomerular filtrate become tubular filtrate?
enters the PCT, has to remove some constituents of filtrate through reabsorption back into the bloodstream
How much of tubular reabsorption takes place in the proximal convoluted tube?
65%
What is the tubular filtrate made up of?
water, sodium, chloride, bicarbonate, glucose, amino acids
What is the main function of the loop of henle?
create and maintain an osmolarity gradient in the renal medulla, enables the collecting duct to concentrate urine at later stage
What is a special feature of the descending part of the loop of henle?
the wall is relatively permeable to water but relatively impermeable to particles, water is removed because of the osmotic gradient between the tubular lumen and the interstitial fluids of the renal medulla
What is a special feature of the ascending part of the loop of henle?
relatively impermeable to water, it has a thick portion that is the site of a great deal of sodium and chloride reabsorption (going from the tubule to the capillaries)
How is the osmotic gradient produced in the ascending limbs of the loop of henle?
the combined effect of transport by ascending and descending limbs produces an osmotic gradient in the interstitial fluids of the renal medulla
Where does reabsorption and secretion occur in the nephron?
distal convoluted tubule under control of hormones, this is how kidneys respond to the body’s needs and adjust urine content
What is the function of the collecting duct in terms of concentrating urine?
concentrate urine by conserving water, this is possible by the osmolarity gradient generated by the loop of henle, the medulla gets saltier, the filtrate loose water, as it flows in the collecting duct
What occurs during reabsorption in the kidney?
- Principal cells in the collecting ducts are
the target cells for ADH - If ADH is not present, the water permeability of the collecting duct is relatively low
- It results in a large volume and diluted urine, as the collecting ducts are impermeable to water
- If ADH is present, the water permeability of the collecting duct is increased
- Water is reabsorbed because the osmolality inside the duct is less than that outside
What is tubular secretion?
Regarding the transfer of several substances that were not filtrated in the glomerular capillaries. These compounds are transferred from the peritubular capillaries back to the tubules, will be excreted in the urine
What is the definition of reabsorption?
movement of substances out of the tubular lumen, through the tubular epithelium and interstitial fluid, and into the peritubular capillary
What is the definition of secretion?
movement of substances from the peritubular capillary, through the interstitial space, tubular epithelium, and tubular lumen.
What are ureters?
a muscular tube that conveys urine from the kidney to the urinary bladder
Where is the ureter located?
Each ureter originates at the renal pelvis and empties into the
urinary bladder
What are the functions of the ureter?
- The smooth muscle of the ureter undergoes peristaltic waves of contraction
- Enables urine to move to the urinary bladder regardless of the position of the animal’s body
What is the function of the transitional epithelium of the ureter?
The transitional epithelium (mucosa) allows the ureters to stretch as urine is passed through them on its way to the urinary bladder
What is the function of the ureters angular entry into the bladder?
Ureters enter the urinary bladder at an oblique angle
When the bladder is full, it collapses the opening of the ureter, preventing urine from backing up into the ureter
What is the urinary bladder?
Is a hollow muscular organ that varies in size and position with the amount of urine it contains
What is the function of the urinary bladder?
The function of the urinary bladder is to collect, store, and release urine
When the bladder is full, it collapses the opening of the ureter
What is the urethra?
Continuation of the urinary bladder
What is the urethra lined with?
transitional epithelium that allows it to expand
What is the function of the urethra?
The urethra carries urine from the urinary bladder to the external environment
What is the difference of the urethra in males and females?
female: strictly urinary function
male: has also a reproductive function (carry semen)
What are the artery and vein that supply and drain blood from the kidney?
renal artery and renal vein
What are the five functions of the kidney
- blood filtration, reabsorption, secretion
- fluid balance regulation
- acid-base balance regulation
- hormone production
- blood pressure regulation
