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Anatomy and Physiology-Urinary System Cheat Sheet by

A brief overview of the urinary system

Urinary System

Functions of the Urinary System

Kidneys dispose of waste products in urine
Kidneys’ regulatory functions include:
Nitrog­enous wastes
Production of renin to maintain blood pressure
Toxins
Production of erythr­opo­ietin to stimulate red blood cell production
Drugs
Conversion of vitamin D to its active form
Excess ions
The urinary system consists of kidneys, ureters, urinary bladder, and urethra.

Kidneys

The kidneys lie against the posterior abdominal wall, underneath the 12th rib.
They are retrop­eri­toneal (posterior to the parietal perito­neum).
• The ribs help protect the kidneys, as does a heavy cushion of fat encasing each
organ.
• Structures (such as blood vessels, the ureters, and nerves) enter and leave the
kidney through a slit called the hilum—­located in a concave notch on the medial
side.

Interior of the Kidney

Interior of the Kidney

A tough, fibrous capsule surrounds each kidney. The interior consists of the renal cortex and renal medulla; the renal cortex forms the outer region and the renal medulla forms the inner region.
Rrenal columns extened from the renal cortex,and divide the interior into cone-s­haped sections, renal pyramids. The base of each pyramid faces outward toward the cortex; the point of the pyramid, renal papill­a,faces the hilum. The renal papilla extends into a cup called a minor calyx.
The calyx collectsV urine leaving the papilla. Two or three minor calyces join together to form a major calyx The major calyces converge to form the renal pelvis, which receives urine from the major calyces. The renal pelvis continues as the ureter, which channels urine to the urinary bladder

Blood Flow Through Kidneys

Aorta → Renal Artery → Afferent Arterioles → Glomerulus → Efferent Arterioles → Pelvic Capill­aries → Renal Vein → Inferior Venal Cava → Right Atrium

Kidney Protection

Three protective layers enclose the kidney
Fibrous capsule encloses each kidney
Perirenal fat capsule surrounds the kidney and cushions against blows
Renal fascia is the most superf­icial layer that anchors the kidney and adrenal gland to surrou­nding structures

Renal Tubule

Arising from Bowman’s capsule is the proximal convoluted tubule.
The renal tubule straig­htens out and dips into the medulla before turning sharply and returning to the cortex.
The collecting duct receives drainage from the distal convoluted tubules of several different nephrons.
Thousands of microvilli that allow absorption line the inside of the proximal convoluted tubule
his entire segmen­t—which consists of a descending limb and an ascending limb—is called the loop of Henle
The collecting duct passes through the medulla and merges with other collecting ducts before draining into a minor calyx.
 
After returning to the cortex, the ascending limb coils again, forming the distal convoluted tubule.

Renal Circul­ation – Blood Supply

One-qu­arter of the total blood supply of the body passes through the kidneys each minute
Renal artery provides each kidney with arterial blood supply
Renal artery divides into segmental arteries → interlobar arteries → arcuate arteries → cortical radiate arteries
   
As it enters the kidney, it divides into smaller and smaller arteries. The arteries pass through the renal columns and into the renal cortex.
   
Blood leaves the kidney through the renal vein, which empties into the inferior vena cava.
   
Nephro­ns—the filtration units of the kidney­—pr­imarily lie in the kidney’s outer region (the cortex). Loops from the nephron dip into the inner region (the medulla).
 

Filtrate from Glomerulus to Urine Excretion

1. Glomerulus --->
2. Bowman's capsule --->
3. Proximal Convoluted Tubule --->
4. Loop of Henle --->
5. Distal Convoluted Tubule --->
6. Collecting Duct --->
7. Renal Pelvic (minor and major calyxes) --->
8. Ureters --->
9. Urinary Bladder --->
10. Urethra

Renal Tubule

Extends from
glomerular capsule and
ends when it empties
into the collecting duct
▪ Subdiv­isions
• Proximal convoluted tubule
(PCT)
• Nephron loop (loop of Henle)
• Distal convoluted tubule
(DCT)

Renal Corpuscle

Bowman’s capsule (or glomerular capsule) consists of two layers of epithelial cells surrou­nding the glomerulus in an open-ended covering. (
Fluid filters out of the glomerulus and collects in the space between the two layers of Bowman’s capsule.
 
From there, it flows into the renal tubule on the other side of the capsule.
The renal corpuscle consists of a glomerulus and Bowman’s capsule.

Renal Corpuscle

The renal corpuscle is the beginning of the nephron. (The two main components of
a nephron are a renal corpuscle [which filters blood plasma] and a renal tubule
[where urine is formed])

Nephron

Nephron

Nephrons are the filtration units of the kidney
Afferent Arterioles - arise from smaller arteries in the cortex; each afferent arteriole supplies blood to one nephron
Blood leaves the glomerulus through an efferent arteriole
Nephrons need a constant flow of blood. (More than 20% of the blood pumped by the heart each minute goes to the kidneys.)
Earise from smaller arteries in the cortex; each afferent arteriole supplies blood to one nephron, glomerulus
The efferent arteriole leads to a network of capill­aries around the renal tubules, peritu­bular capill­aries
   
These capill­aries pick up water and solutes reabsorbed by the renal tubules.
   
Blood flows from the peritu­bular capill­aries into larger and larger veins that eventually feed into the renal vein
▪ Structural and functional units of the kidneys
▪ Each kidney contains over a million nephrons
▪ Each nephron consists of two main
structures
• Renal corpuscle
• Renal tubule

Renal Circul­ation – Venous

Venous blood flow
Cortical radiate veins → arcuate veins → interlobar veins → renal vein
Renal vein returns blood to the inferior vena cava

Renal Circul­ation – Blood Supply

 

Renin-­Ang­iot­ens­in-­Ald­ost­erone System

Urine Formation

Glomerular filtration
Tubular reabso­rption
Tubular secretion
Blood flows into the glomerulus through the afferent arteriole and leaves through the efferent arterioles
After filtrate leaves the glomer­ulus, it enters the renal tubules, where additional chemicals are removed from the filtrate and returned to the blood
Chemicals are added to the filtrate
The walls of glomerular capill­aries are dotted with pores; water and small solutes (such as electr­olytes, glucose, amino acids, vitamins, and nitrog­enous wastes) filter out of the blood and into Bowman’s capsule.
Sodium, water, glucose, amino acids, chloride, potassium, and bicarb­onate moves by active transport out of the proximal convoluted tubule and into the bloods­tream of the peritu­bular capill­aries
Wastes such as ammonia (NH3 ) and uric acid, as well as drugs (such as aspirin and penici­llin), are secreted out of the blood and into the tubules.
. Blood cells and most plasma proteins are too large to pass through the pores. The fluid that filters into Bowman’s capsule flows into the renal tubules.
About half of the nitrog­enous waste urea is also reabso­rbed.
Tubular secretion of hydrogen ions also occurs, helping to regulate the body’s pH.
 
Sodium and chloride are actively pumped out of the ascending limb of the loop of Henle into inters­titial fluid.
Water diffuses out of the descending limb of the loop of Henle, further concen­trating the filtrate
 
The distal convoluted tubule and collecting ducts reabsorb variable amounts of water and salts.
 
The distal convoluted tubule and collecting ducts reabsorb variable amounts of water and salts.
 
Specia­lized cells play a role in acid-base balance, reabso­rbing potassium and secreting hydrogen into the tubule.
 
Several different hormones 23 Tubular Reabso­rption and Secretion View animation on “Urine formation” Copyright ©2020 F.A. Davis Company Chapter 19: Urinary System 23 help regulate reabso­rption by the cells in the distal convoluted tubule.
 
The collecting duct reabsorbs water and concen­trates the filtrate, resulting in urine.
Urine formation involves three processes:
1. Glomerular filtration
2. Tubular reabso­rption
3. Tubular secretion

Formation of Urine

Basic Stages of Urine Formation

1. Glomerular Filtra­tion:
Creates a plasma­-like filtrate of the blood.
2. Tubular Reabso­rption:
Removes useful solutes from the tubular
fluid, returning them to the blood
3. Tubular Secretion:
Removes additional waste from the blood,
adds them to the tubular fluid
4. Water Conser­vation:
Removes water from the urine and returns
it to the blood; concen­trates waste

Urine Compos­ition

Color – the color is generally yellow but varies in degree and clarity
Odor – freshly voided urine should have no particular order unless affected by certain ingred­ients. Urine that has sat smells of ammonia
pH – pH is generally acidic but can range from 4.5-8.0
Volume – 0.75L – 2L/24 hours
Specific Gravity – 1.003 – 1.032

Compos­ition of Urine

Consists of 95% water; 5% dissolved substances
Reveals inform­ation about health of kidneys and other organs
The dissolved substances include nitrog­enous wastes­—such as urea, uric acid, ammonia, and creati­nine—as well as other solutes, such as sodium, potassium, and sulfates.

Solutes in Urine

Solutes normally found in urine
Solutes NOT normally found in urine
Sodium and potassium ions
Glucose
Urea, uric acid, creatinine
Blood proteins
Ammonia
Red blood cells
Bicarb­onate ions
Hemoglobin
 
WBCs (pus)
 
Bile

Hormones That Affect the Urinary System

• Aldost­erone, ANP, and PTH all act on the renal tubules; ADH acts primarily on the
collecting duct.
• The adrenal cortex secretes aldost­erone when blood levels of Na+ decline or
concen­tration of K+
increases.
• The atria of the heart secretes ANP when blood pressure rises; this inhibits the
secretion of aldost­erone and ADH.
• The posterior pituitary gland secretes ADH.
• The parath­yroid glands secrete PTH in response to low calcium levels.
 

Urinary System

The ureters and urethra serve as passag­eways for conducting urine away from the
kidneys and out of the body while the bladder stores urine until it can be
elimin­ated.
The ureters connect the renal pelvis of each kidney with the bladder

Ureters

Attaching the kidney to the urinary bladder
Perist­alsis aids gravity in urine transport
Continuous with the renal pelvis
Enter the posterior aspect of the urinary bladder
Run behind the peritoneum

Urinary Bladder

Smooth, collap­sible, muscular sac situated posterior to the pubic symphysis
Trigon­e—t­ria­ngular region of the urinary bladder base based on three openings
Mucous transi­tional epithelium lines the bladder. When the bladder relaxes, this layer forms folds, rugae. As urine fills the bladder, the rugae flatten and the epithelium thins, allowing the bladder to expand.
Two openings from the ureters (ureteral orifices)
 
One opening to the urethra (internal urethral orifice)
 
At the point where the urethra leaves the bladder is a ring of smooth muscle that forms the internal urethral sphincter. This sphincter contracts involu­ntarily to retain urine in the bladder.
 
External urinary sphincter exists where the urethra passes through the pelvic floor; this sphincter consists of skeletal muscle and is, therefore, under voluntary control.
 
The urethra is a small tube that conveys urine away from the bladder and out of the body; it opens to the outside of the body at the external urinary meatus.
▪ In males, the prostate
surrounds the neck of the
urinary bladder

Urinary Bladder

Smooth, collap­sible, muscular sac situated posterior to the pubic symphysis
Trigon­e—t­ria­ngular region of the urinary bladder base based on three openings
Mucous transi­tional epithelium lines the bladder. When the bladder relaxes, this layer forms folds, rugae. As urine fills the bladder, the rugae flatten and the epithelium thins, allowing the bladder to expand.
Two openings from the ureters (ureteral orifices)
 
One opening to the urethra (internal urethral orifice)
 
At the point where the urethra leaves the bladder is a ring of smooth muscle that forms the internal urethral sphincter. This sphincter contracts involu­ntarily to retain urine in the bladder.
 
External urinary sphincter exists where the urethra passes through the pelvic floor; this sphincter consists of skeletal muscle and is, therefore, under voluntary control.
 
The urethra is a small tube that conveys urine away from the bladder and out of the body; it opens to the outside of the body at the external urinary meatus.
▪ In males, the prostate
surrounds the neck of the
urinary bladder

Urethra

Thin-w­alled tube that carries urine from the urinary bladder to the outside of the body by perist­alsis
           
 

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