Urinary System Flashcards
Renal Functions
The kidneys continuously monitor the blood to ensure
optimal properties of the blood.
Filtration
Reabsorption
Secretion
Excretion (through urine)
Nephron
Kidneys each contain 1-4 million functional units called nephrons, each with a corpuscle and a long epithelial renal tubule with three main parts. The major divisions of each nephron are:
Renal corpuscle
Renal tubule, with several parts.
The remaining tubes are technically not part of the nephron:
Collecting tubules
Collecting ducts
Renal corpuscle
A dilated part enclosing a glomerulus (tuft of capillary loops) and a two-layered capsule—an outer parietal layer and an inner visceral layer, entirely in the cortex; the site of blood filtration.
Between the layers is the capsular space (Bowman’s space), into which filtrate enters from the capillaries through the visceral layer.
Renal tubule
Several parts. This is the site of secretion and re-
absorption.
Includes:
Proximal tubule
Loop of Henle ( in the medulla)
Distal tubule
Connecting tubule
Connecting tubule
A part of the renal tubule a short tube linking the nephron to collecting ducts.
Collecting tubules
Formed by merger of several connecting tubules.
Collecting ducts
Formed from merger of collecting tubules.
These converge in the renal papilla, where they deliver urine to a minor
calyx, then to a major calyx, and then to the renal pelvis and then to the ureter.
Renal Blood Supply
Renal A
Segmental A
Interlobar A
Arcuate A
Interlobular A
Afferent Arteriole
Glomerulus
Efferent Arteriole
Peritubular capillaries and Vasa recta (associated with loop of Henle)
Interlobular V
Arcuate V
Interlobar V
Renal V
Microvasculature
Small interlobular arteries branch from the arcuate arteries and radiate out through the cortex
giving off the afferent arterioles
Which three of the major functions of the kidneys are performed by specialized epithelial cells of the nephrons and collecting systems:
Filtration
Tubular secretion
Tubular reabsorption
Filtration
Water and blood solutes move from the blood vessels to the lumen of the nephron; it is then called
filtrate. This takes place in the renal corpuscle.
Tubular secretion
Substances move from epithelial cells of the tubules into the lumens.
Tubular reabsorption
Substances move from the
lumen across the tubular epithelium into the interstitium and capillaries.
Glomerular Filter
Glomerular blood pressure forces water and solutes to be filtered out of the blood.
The glomerular filter has three parts:
Fenestrated capillary endothelium
Thick basal lamina (glomerular basement membrane)
Filtration slits of visceral layer
Glomerular filtrate
Includes glucose, amino acids, ions, urea, some
hormones, vitamins, and small proteins (but not large ones).
Travelling through the Nephron
Filtrate
1. Capsular space
Tubular fluid
- Proximal convoluted tubules
- Descending limb of nephron loop (Loop of Henle)
- Ascending limb of nephron loop (Loop of Henle)
- Distal convoluted tubules
- Connecting tubules
- Collecting duct (not part of nephron)
Urine
- Papillary duct
Proximal Convoluted
Tubule
Location: Cortex
Function: Re-absorption (into the peritubular capillaries) of all organic nutrients, all proteins, most water and electrolytes;
secretion of organic wastes, H+, and ammonia.
Loop of Henle
Location: Medulla and Medullary rays
Function: The primary function of the loop of Henle is to produce concentrated urine by osmosis.
Distal Convoluted Tubule
Location: Cortex
Function: Re-absorption of electrolytes (Na+ and Cl-)
Collecting system Principal cells
Location: Medulla rays and medulla
Function: Regulated reabsorption of water and electrolytes; regulated secretion of K+ ions.
Juxtaglomerular Apparatus
The juxtaglomerular apparatus (JGA) is a sensory structure which is an important regulator of blood pressure.
It is made of epithelial cells of the macula densa and smooth muscle cells
in the afferent arteriole called juxtaglomerular granular cells, which
secrete renin.
What is Urine?
About 91-96% of urine consists of water.
The three main nitrogenous wastes of the mammalian body are urea, uric acid, and creatinine.
Urea
The liver detoxifies ammonia by combining
ammonia molecules with carbon dioxide to form urea
Uric acid
a product of metabolism of
purines, and it is a normal component of urine. In contrast to urea, it is mostly
insoluble in water.
High blood concentrations of uric acid can lead to gout and are associated with
diabetes and the formation of some types of kidney stones.
Creatinine
A breakdown product of creatine phosphate from muscle metabolism.
Creatinine is removed from the blood chiefly by
the kidneys, primarily by glomerular filtration, but
also by proximal tubular secretion.
Gout
A painful condition resulting from needle-like crystals of uric acid precipitating in joints, capillaries, skin, and other tissues
Glomerular filtration rate (GFR)
If the filtration in the kidney is deficient, creatinine
blood levels rise. Therefore, creatinine levels in blood and urine may be used to estimate glomerular filtration rate (GFR), a measure of how well the kidneys are working.
Bladder and Urethra
The muscularis consists of three poorly delineated layers, collectively called the detrusor muscle; it contracts to empty the bladder.
There is an internal urethral sphincter muscle (involuntary) and an external urethral sphincter muscle
(voluntary).
Cystitis
inflammation of the bladder
mucosa, is the most frequent problem involving
this organ.
Common during UTI
Chronic cystitis can cause an unstable urothelium (transitional epithelium)
Urinary tract infections
Usually involving coliform bacteria or Chlamydia, often produce urethritis and in women often lead
to cystitis because of the short urethra.
