Urinary system Flashcards
What is the function of the urinary system?
- regulates plasma ion concentrations
- regulates blood volume and BP
- helps stabilize blood pH
- prevents the loss of valuable nutrients
- eliminates metabolic waste
- synthesizes calcitriol (active form of vitamin D) and erythropoietin (RBC production)
- aids the liver with some metabolic functions
What does the urinary system consist of?
- Kidneys
- urinary tract
What is the function of the kidneys?
- produce urine
- & associated nephrons
what is the function of the urinary tract?
- transports/stores urine
- consists of:
a. ureters
b. urinary bladder
c. urethra
what is the medical term for eliminating urine?
- micturition
- urination
what are the 3 layers of connective tissue that function to protect the kidneys?
- fibrous capsule
- perinephric fat (perirenal fat capsule)
- renal facia
How big is the typical kidney?
- 4 inches long
- 2.2 inches wide
-1.2 inches thick
What does a kidney lobe consist of:
- renal pyramid (overlaying)
- renal cortex &
- adjacent renal columns
what does the kidney consist of?
- renal cortex
- renal medulla
deep to the cortex:- renal pyramids
- renal papillae
- renal columns
where does blood in the renal arteries flow to?
- segmental arteries
- interlobular arteries
- arcuate arteries
- cortical radiate arteries
- afferent arteries
- glomerular capillaries
what does the renal pelvis consist of?
- Minor calyx
- major calyx
(also comprises most of the renal sinus)
what are nephrons?
- where filtration occurs in the kidney
- it creates a concentrated urine by creating an ultrafiltrate from blood
How does blood leave the kidneys?
- glomerular capillaries
- efferent arteriole
- peritubular capillaries
- cortical radiate veins
- arcuate veins
-interlobar veins - renal vein
NO SEGMENTAL veins
what does each nephron have?
- a renal capsule
- renal tubule
how does blood go in & out of the kidneys?
IN: OUT
1. renal artery 1. peritubular capillaries
2. segmental arteries 2. venules
3. interlobar arteries 3. cortical radiate veins
4. arcuate arteries 4. arcuate veins
5. cortical radiate arteries 5. interlobar veins
6. afferent arterioles 6. renal veins
7. glomerulus capillaries
in the nephron where blood is going through the efferent arteriole `
define autoregulation.
- what urine production is regulated by
- involves reflxive change in diameter of nephron arterioles
what does a renal capsule consist of?
- glomerular capillaries (glomerulus)
- glomerular capsule
- glomerular filtrate leaves the glomerular capillaries and enters the glomerular capsule - afferent arteriole and efferent arteriole form the vascular pole
What is the flow of the nephron & collecting system?
- renal tubule
- proximal convoluted tubule (PCT)
- nephron loop
- distal convoluted tubule (DCT)
- Filtrate from the DCT empties into the collecting system
- connecting tubules from several nephrons lead to a common collecting duct
- the collecting duct passes through the renal pyramids
How does the filtrate flow in the connecting duct?
- Papillary duct
- minor calyx
- major calyx
- filtrate is now called urine
How does urine leave the kidneys?
Via the urinary tract:
1. ureter
2. urinary bladder
3. urethra
what are the two types of nephrons?
- cortical nephrons
- juxtamedullary nephrons
what are features of cortical nephrons?
- 85 % of the nephrons are cortical
- most of the nephron is located in the cortex
- have a relatively short nephron loop
what are some features of juxtamedullary nephrons?
- 15% of nephrons are juxtamedullary
- capsule is located near the border of the cortex
- have a long nephron loop
what are the main fuctions of the nephron?
- reabsorbs useful organic material & ions from the filtrate
- reabsorbs more than 99 % if water from filtrate
- enhances the elimination of wastes by actively secreting them into the filtrate
what does the glomerular capsule consist of? q
- capsular outer layer (parietal layer)
- made of squamous cells that are continuous with lining of the PCT - folds back to form the visceral layer
- visceral layer: makes up the epithelial lining of the glomerular capillaries
what 5 filtration barriers does filtrate have to go through in the renal corpuscle
- endothelial surface layer
- glomerular capillary endothelium
- basement membrane
- glomerular epithelium
- subpodocyte space
what is the purpose of mesangial cells?
- provides support for capillaries & regulate blood flow
What are the features of glomerular epithelium?
- consist of special cells called podocytes
- podocytes have ling cellular extensions (secondary processes) that wrap around the basal lamina
- extensions have filtration slits that allow for the filtration of bigger proteins and RBCs
what substances filter through in the renal corpuscle?
- filtrate passing through barriers consist of water, ions, small organic molecules
- passing filtrate contains very few plasmas proteins
- many substances are reabsorbed in the nephron tubule
what features does the proximal convoluted tubule contain?
- begins at tubular pole of renal corpuscle
- lined w/ simple cuboldial epithelium, also has microvilli
what substances does the proximal convoluted tubule reabsorb?
- organic nutrients
- plasma proteins
- 60 % of the sodium & chloride ions & water
- other ions
- ex: calcium, potassium, phosphate, and bicarbonate
What does the nephron loop consist of?
- descending limb:
- water leaves this portion and enters the blood stream (preventing dehydration) - ascending limb:
- pumps ions (sodium ions & chloride ions) and out of
what does the nephron consist of?
- descending limb
- ascending limb
- both loops have simple squamous epithelium
- capillaries surrounding the nephron lopp
what is the vasa recta
- capillaries surrounding the nephron loop
what does the descending limb in the nephron loop do?
- descending limb:
- water leaves this portion and enters the blood stream (preventing dehydration)
what does the ascending limb in the nephron loop do?
- ascending limb:
- pumps ions (sodium ions & chloride ions) and out of the tubular fluid- impermeable to water
what are the features of the distal convoluted tubule?
- active, regulated secretion of ions and acids
What does the distal convoluted tubule consist of?
- The juxtaglomerular complex
- located in the region of vascular pole
What does the juxtaglomerular complex consist of?
- macula densa cells
- juxtaglomerular cells
- extraglomerular mesangial cells
What two hormones does the distal convoluted tubule?
- Renin: involved in regulating BP
- erythropoietin: involved with making RBC’s
what is the overall summary of the collecting system?
- The DCT of each nephron connects to a connecting tubule
- Several connecting tubules drain into a
collecting duct - The cells of the collecting ducts make final
adjustments to the concentration of the urine that is about to exit the kidneys - Several collecting ducts converge and empty into a papillary duct
- Papillary ducts empty into minor calyxes
- At this point the filtrate is no longer modified and is properly called urine
- Urine moves from minor calyx to major calyx
- Then drains to renal pelvis
- Then drains to ureters
what are the features of epithelium of the collecting system?
- Begins as simple cuboidal in collecting tubules
- Transitions to simple columnar in collecting and papillary ducts
- transitional epithelium lines the minor and major calyces and renal pelvis
Once the urine has entered the ureter where does the urine flow to?
- Exit the kidney at the hilum area
- Extend to the urinary bladder
- Enter the urinary bladder on the posterior/inferior side
- The ureteral orifices enter the urinary bladder in the trigone area
- Peristaltic contractions and gravity move urine toward the urinary bladder
what are the 3 layers of the ureter?
- inner mucosa (lined w/ transitional epithelium)
- middle muscular layer (longitudinal and circular smooth muscle)
- Adventitia (continuous w/ fibrous capsule and parietal peritoneum)
what is the difference between male and female between urinary bladder?
Females: The base of the urinary bladder is inferior to the uterus and anterior to the vagina
males: The base of the urinary bladder is between the rectum and the symphysis pubis
define peritoneal folds
- that assist in maintaining the position of urinary bladder
define median umbilical ligament
- extends from the anterior/superior bored to the umbilical region
define Lateral umbilical ligaments
extend from lateral edges to the umbilical region
what is the mucosa of the urinary bladder?
- has folds called rugae to increase bladder volume
- lined w/ transitional epithelium
- trigone region funnels urine to the urethra
define detrusor?
- smooth muscle layer of the urinary bladder
What surrounds the entrance to the urinary bladder?
- neck of the urinary bladder
- liked w/ smooth muscle that make up internal sphincter
- under involuntary control
What are the features of male urethra?
- 18/20 cm in length
- subdivide into prostatic urethra, membranous urethra, spongy urethra
what is the histology of male urethra?
- transitional epithelium near bladder
- changes to pseudostratified columnar and then stratified columnar
- finally, striated squamous near external urethral opening
what is the function of the prostatic urethra?
- passes through the prostate gland
what is the function of the membranous urethra?
- short segment that penetrates the muscular wall of the pelvic cavity in the inguinal region
what is the function of the spongy urethra? (penile urethra)
- extends through the penis to the external urethral orifice
what makes up the external urethral sphincter?
- skeletal muscle
- under voluntary control (we learn to control as an infant)
- lose control as we age
what is the urine storage reflex?
- urine storage increases sympathetic activity
- inhibits detrusor muscle
- stimulates contraction internal and external urethral sphincter
- first urge to urinate is when the urinary bladder fills 200 ml
- Stretch-activated spinal reflexes stimulate parasympathetic activity
- Stretch also decreases sympathetic activity
how does urination occur?
- Voluntary effort is needed to relax (and therefore open) the external urethral sphincter
- Upon “complete void,” approximately 10 ml of urine still remains
- When the urinary bladder nears capacity, both urethral sphincters will open based on pressure
Age related problems with urinary system:
- number of functional nephrons decrease with age
- nephrons decline by 30- 40 % between ages 25 to 85
- reduced sensitivity by ADH hormone, resulting in frequent urination
