urinary system

list the general functions of the urinary system

excretion of waste products of metabolism

electrolyte and water balance

metabolism of vitamin D to its active form

production of the erythropoietin

production of the enzyme renin

list the parts of the urinary system

right and left kidney

right and left ureter

urinary bladder

urethra

where are the kidneys located in the body?

retroperitoneal

located outside of peritoneal membrane that encloses abdominal cavity organs

what is the hilus of the kidney and where is it located?

the indentation of the bean shape

where the renal artery enters

where the renal vein and ureter exit

what are the 2 part of the kidney grossly?

outer cortex

* where blood is filtered through glomeruli

inner medulla

* where urine is concentrated through tubules

what is a nephron?

one glomerulus and its corresponding set of tubules

list the functions of the kidney

maintain plasma volume and composition

regulate water and ion levels

acid-base balance

retain nutrients

excrete waste, toxins, excess electrolytes

production of hormones (erythropoietin)

what is the function of the outer fibrous connective tissue capsule of the kidney?

surrounds the kidney and prevents expansion

easily stripped away from a healthy kidney

adherent in pathology

what is the renal pelvis?

the funnel-shaped area inside the hilus

what are the pyramids of the kidney?

tubules of nephrons

what are renal papillae?

tips of pyramids

drain urine from nephron tubules into larger vessels called minor calyces

what do papillae drain into?

from nephron tubules into larger vessels called minor calyces

what do minor calyces drain into?

converge into major calyces

what do major calyces drain into?

lead to renal pelvis and enlarged opening of the ureter

blood vessels travel through renal columns to the cortex

describe the general gross anatomy and location of the kidneys in the dog and cat

kidneys are mobile (left in cat)

right kidney is more cranial and lies beneath L1-L3

enclosed within renal fossa of caudate lobe of liver

left kidney under L2-L4

cranial pole contacts greater curvature of stomach

describe the general gross anatomy and location of the bovine kidney

multiple lobules on surface

right is flattened and ellipsoidal

left is thicker at caudal end

each surrounded by layer of fat with no renal pelvis

both located on the right in bovids

left is caudoventral to right and between L2 and L4

describe the general gross anatomy and location of the kidneys in sheep

short and thick and surrounded by thick masses of fat

right kidney cranial portion touches liver, pancras, duodenum, adrenal glands, colon

describe the general gross anatomy and location of the kidneys in swine

flattened dorsoventrally with smooth surface

left and right are aligned

renal pelvis opens into a large space of 2 major calyces

embedded in fat and against psoas muscle

span from last rib cranially and L4 caudally

right kidney doesn’t touch liver

left kidney ventral to asc. colon, base of cecum, pancreas

describe the general gross anatomy and location of kidneys in horses

right kidney is heart shaped, left is pyramidal

dorsoventrally flattened and unipyrimidal

single renal papilla and not smooth

enclosed in fat capusle

right is ventral to/between last 2 ribs and L1 transverse process

left is between last rib and L3 transverse process

what is the basic functional unit of the kidney?

the nephron

what are the 2 parts of the nephron?

renal corpuscle and renal tubule

what is the function of the renal corpuscle?

filters blood in the nephron

what are the 2 parts of the renal corpuscle?

proximal convoluted tubule (PCT)

loop of henle

distal convoluted tubule (DCT)

what is the glomerulus?

part of renal corpuscle

cluster of capillarries at beginning of nephron

where is the glomerulus located?

at the beginning of the nephron

what type of epithelium lines the glomerulus?

simple squamous epithelium

what is the bowman’s capsule?

part of renal corpuscle

membranous double-walled capsule surrounding the glomerulus

where is the bowman’s capsule located?

surrounding the glomerulus

what type of epithelium lines the bowman’s capsule?

simple squamous epithelium

what is the major function of the renal tubule of the nephron?

reabsorption that happens through active or passive transport

substances leave tubules and enter into blood of peritubular capillaries

what are the parts of the renal tubule and where are they located?

proximal convoluted tubule (PCT): proximal to glomerulus

loop of henle: descending and ascending limbs, passed through renal medulla

distal convoluted tubule (DCT): distal to glomerulus

trace the flow of urine starting with the bowman’s capsule

bowman’s capsule, proximal convoluted tubule (PCT), descending limb of the loop of henle, ascending limb of the loop of henle, distal convoluted tubule (DCT), collecting ducts,

what pushes fluid into the bowman’s capsule and what type of substances pass through into the capsule?

blood pressure in the glomerular capillaries

water, ions, amino acids (filtrate mixture)

what is the proximal convoluted tubule (PCT) a continuation of?

a continuation of the capsular space of bowman’s capsule

what type of epithelium lines the PCT?

simple cuboidal epithelium

what is the main function of the PCT?

maximum reabsorption

* AAs, proteins, glucose, vitamins, water, Na+, Cl-, HCO3

secretes waste products into filtrate

* ammonia, urea, H+, K+

what substances are reabsorbed in the PCT?

AAs, proteins, glucose, vitamins, water, Na+, Cl-, HCO3

what substances are secreted into the tubular filtrate in the PCT?

ammonia, urea, H+, K+

what is the descending limb of the loop of henle permeable to?

water

what is the descending limb of the looop of henle impermeable to?

salts

what is the ascending limp of the looop of henle permeable to?

salts

what is the ascending limb of the loop of henle impermeable to?

water

what is the function of the distal convoluted tubule (DCT)?

reabsorbs Na+, Ca2+, HCO3

secretes H+, K+, ammonia, urea

maintains pH and sodium-potassium channel in blood

what is the function of the collecting ducts?

to absorb water and concentrate urine

which 2 hormones control the permeability of the collecting ducts?

ADH (vasopressin) and aldosterone

what is another name for ADH?

vasopressin

where is ADH produced?

in the hypothalamus

what effect does ADH have on the DCT and collecting ducts of nephrons?

increases the permeability of the duct to water by opening aquaporins

where is aldosterone produced?

in the adrenal cortex

what effect does aldosterone have on the late DCT and collecting duct of nephrons?

increases Na/K pump activity

reabsorption of Na+ and water

excretion of K+

acid-base balance

which portion of the nervous system provides the nerve supply to the kidney?

the sympathetic portion of the autonomic nervous system

afferent and efferent nerves

what effect does sympathetic input have on Beta-1-adrenergic receptors in the juxtaglomerular cells of the kidney?

leads to releases of renin and activation of the renin-angiotensin-aldosterone-system (RAAS)

increased Na+ reabsorption

increased systemic blood pressure

describe the blood supply and the function of each to the kidney

renal artery enters at hilus

subdivides to become series of afferent glomerular arterioles

what do afferent glomerular arterioles do?

carry blood to the renal corpuscle

what do glomerular capillaries do?

filter some plasma out of the blood (glomerular filtrate)

what do peritubular capillaries do?

oxygen transfer to cells of nephron and tubular reabsorption and secretion

what are the 3 general mechanisms of renal action?

filtration of blood

reabsorption of useful substances

secretion of waste products

where does the filtration of blood occur?

in the renal corpuscle

what causes plasma to move from the glomerular capillaries into the bowman’s capsule?

high blood pressure in glomerular capillaries

what affects the glomerular filtration rate (GFR)?

depends on the rate of blood flow to the kidney

what determines urine volume?

the amount of water contained in tubular filtrate when it reaches the renal pelvis

what hormones control the amount of water in tubular filtrate?

ADH and aldosterone

what happens if ADH is absent?

polyuria (the production of abnormally large volumes of dilute urine)

how do the kidneys help regulate blood pressure?

RAAS responds to low blood pressure

renin released and converts enzyme angiotensin

increased sodium/water reabsorption into bloodstream=increase in blood volume

increased blood volume=increased blood pressure

list the structures of the lower urinary tract (LUT)

urinary bladder, urethra, caudal ureter

where is the detrusor muscle found?

LUT, bladder apex and body

expels urine

what is the function of the detrusor muscle?

expels urine

what type of muscle is the detrusor muscle?

smooth muscle

where is the internal urethral sphincter located?

the bladder neck and cranial urethra

what is the function of the internal urethral sphincter?

regulates involuntary control of urine flow from the bladder to the urethra

what type of muscle is the internal urethral sphincter?

smooth muscle

where is the external urethral sphincter located?

urethralis muscle that encircles the caudal urethra

what is the function of the external urethral sphincter?

provides voluntary control of urine flow from the bladder to the urethra

what type of muscle is the external urethral sphincter?

striated urethralis muscle

what is the urethralis muscle?

muscle that encircles the caudal urethra

list and describe the 3 parts of the urinary bladder

apex

* cranial blind end

neck

* funnel-shaped region between ureter openings and urethra

body

* region between neck and apex

what is the trigone of the urinary bladder?

triangular area of smooth mucosa inside dorsal wall of bladder neck

attaches ureters to bladder neck and urethra

what are the ureters?

tubes that exit the kidney and empty into the urinary bladder by a slit opening at the cranial margin of the vesical neck

continuation of the renal pelvis

what type of epithelium lines the ureters?

transitional epithelium

what prevents urine in the urinary bladder from backing up into the ureters?

the openings of the ureters collapse when the bladder is full

what is the function of the urinary bladder?

store urine, collect urine, release urine

what type of epithelium lines the urinary bladder?

transitional epithelium

what is micturition?

the action of urinating

what is uresis?

the passing of urine, urination

which portion of the nervous system stimulates the detrusor muscle to expel urine?

the parasympathetic activation via pelvic nerve innervation

which nerve innervates the detrusor muscle?

the pelvic nerve

what structure provides involuntary tonic resistance to urination?

the smooth muscle sphincter

which portion of the nervous system stimulates the internal urethral sphincter?

the sympathetic innervation via hypogastric nerves

which nerve innervates the internal urethral sphincter?

hypogastric nerves

which structure opposes sudden increases in bladder pressure and is important for voluntary continence?

the striated urethralis muscle

which nerve innervates the external urethral sphincter?

the pudendal nerve

what is the function of the urethra?

to carry urine from the bladder to the external environment

where is the female urethra located in dogs and cats?

from the internal urethral orifice at the bladder neck to the external urethral orifice

where does the female urethra open in dogs and cats?

on the floor of the cranial vestibule

in a urethral tubercle (dog)

as a groove (cat)

what type of epithelium lines the female urethra?

transitional epithelium that become stratified cuboidal in the mid urethra and stratified squamous at the termination

what type of muscle is found in the female urethra of dogs and cats?

circular smooth muscle in the cranial 2/3

striated muscle in the caudal 1/3

describe the comparative anatomy and function of the female urethra

shorter/straighter

opens on ventral portion of vestibule of vulva

lined with transitional epithelium to expand

carries only urine

list and describe the 3 parts of the pelvic urethra in male cats

preprostatic urethra

* extends from bladder neck to prostrate
* smooth muscle coat is circular

prostatic urethra

* ventral to the body of the prostrate
* submucosa has elastic fibers, deficient in smooth muscle
* bilateral opening of each ductus deferens and prostatic ducts

postprostatic urethra

* extends from prostrate body to root of penis, paired bulbourethral glands here
* striated urethralis muscle encircles urethral submucosa

list and describe the 2 parts of the pelvic urethra in male dogs

prostatic urethra

* encircled by large bi-loped prostate gland
* submucosa rich in elastic fibers, lacks encircling smooth muscle

postprostatic urethra

* striated urethralis muscle overlaps caudal surface of prostate gland
* islands of disseminate prostate gland are evident

describe the comparative anatomy and function of the male urethra

longer/curved

runs along ventral aspect of penis

lined with transitional epithelium for expansion

carries urine or semen