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Eva Moffat Review of the A & P of the urinary system The functions of the urinary system are: •Removal of metabolic wastes (nitrogenous and acidic) •Removal of hormones, drugs, and other foreign material from the body •Regulation of water, electrolytes, and acid-base balance in the body •Secretion of erythropoietin •Activation of vitamin D •Regulation of blood pressure through the renin-angiotensin-aldosterone system
Kidneys: Two kidneys are bean-shaped structures
Each the size of a fist, located behind the peritoneum (that is, retroperitoneally) on the posterior abdominal wall.
The kidneys are covered by a fibrous capsule and are embedded in fat, with the superior portion also protected by the lower ribs
Inside each kidney is the cortex, or outer layer, in which the majority of the glomeruli are located, and the medulla, or inner section of tissue, which consists primarily of the tubules and collecting ducts.
Inside the medulla lie the renal pelvis and calyces, through which urine flows into the ureter.
Each kidney consists of over a million nephrons, the functional units of the kidney. The renal corpuscle consists of Bowman's capsule (glomerular)
Stomach: When you first take a bite out of your favorite food, it travels from the mouth through the esophagus and into the stomach.
Then the partially digested food will enter the intestines, where it will be broken down even more.
Eventually, tiny particles of what was once a juicy hamburger will travel through your blood and into the most important organ involved in the detoxification of your body.
This organ is called the liver.
Liver: While many other organs and tissues have the capability to break down things like toxins or drugs, it is the liver that is the biggest center of operation for such needs.
If something enters your bloodstream that is not supposed to be there, liver cells have many ways by which they metabolize, or transform, the toxin or drug into a pretty harmless substance.
The Nephron This filtration of blood and the formation of urine occurs thanks to a structure inside your kidneys called the nephron.
There are many nephrons within each kidney, and each nephron is a structure within the kidney that filters the blood and forms and excretes urine.
Ureters, Bladder, Urethra Once all of the nephrons have performed this role, they will collectively excrete the urine made within the kidneys into a long tube that carries urine from the kidneys and into the bladder called the ureter.
You have two ureters in your body, with one end connecting to the kidney and the other to the bladder, which is the organ responsible for collecting, storing, and excreting urine formed by the kidneys.
1 st^ picture below- Gross Anatomy of the Urinary System 2 nd^ picture- Anatomy of the Kidney
Schema c Illustra on of Urine Forma on
Formation of Urine
Filtration In renal corpuscles Large volume of fluid passes from glomerular capillaries into the tubule (Bowman capsule)
- Wastes, nutrients, electrolytes, other dissolved substances
- Cells and protein remain in the blood. Reabsorption Reabsorption of essential nutrients, water, and electrolytes into the peritubular capillaries Control of pH and electrolytes
Hormones Involved in Reabsorption Antidiuretic hormone (ADH) Secreted by the posterior pituitary Reabsorption of water in distal convoluted tubules and collecting ducts
Aldosterone Secreted by adrenal cortex Sodium reabsorption in exchange for potassium or hydrogen
Atrial natriuretic hormone Hormone from the heart Reduces sodium and fluid reabsorption
GFR later.
Factors Affecting Urinary Elimination
● central control ● Infants are born without voluntary control or ability to concentrate urine ● most children develop control between 2 and 5 years
○ osmoreceptors in medulla when the osmotic concentration of body fluids is high, ADH levels are also high
○ hypothalamus osmoreceptors in the hypothalamus dete ct the osmotic concentration of the bloo d and interstitial fluid
plasma volume or plasma osmolarity sti
→ Tubular resorption ~ most of the fluid’s contents are returned to the blood
→ Tubular secretion ~ unnecessary substances are removed from the blood into the filtrate for excretion
● hormonal control Several hormones, the most important of which is antidiuretic hormone (ADH), play significant roles in the reabsorption of water in the tubules of the nephron. The name “antidiuretic” implies the function of ADH, which is to prevent diuresis, or water excretion. ADH is secreted by the hypothalamus and released by the posterior pituitary in the brain. Increased plasma osmolarity stimulates the release of ADH. When ADH is present, the distal tubule of the nephron becomes more permeable to water, thus producing more concentrated urine. When fluid intake increases, ADH release is suppressed. In the absence of ADH, the renal tubules become relatively impermeable to water, and little water is reabsorbed, producing an increased volume of dilute urine.
○ ADH ○ Secreted by the posterior pituitary ○ Reabsorpti on of water in distal convoluted tubules and collecting ducts
○ Aldosterone ○ Secreted by adrenal cortex ○ Sodium reabsorption in exchange for potassium or hydrogen
○ Renin-Angiotensin ○ Secreted by juxtaglomerular cells when blood flow to afferent arteriole is reduced ○ Renin- angiotensin mechanism
○ Erythropoietin ● Production of erythropoietin is essential to maintaining a normal red blood cell (RBC) volume.
○ Erythropoi etin stimulates bone marrow to produce RBCs and prolongs the life of mature RBCs.
○ Conversion of vitamin D impacts Ca levels and PTH secretion
The Kidneys produces a substance that converts vitamin D into its active form.
Intestines absorb more Ca from foods.
● Filtration (Glomerular filtration rate) ○ In renal corpuscles ○ Large volume of fluid passes from glomerular capillaries into the tubule (Bowman capsule)
Wastes, nutrients, electrolytes, other dissolved substances
○ Related to systemic blood pressure Adequate blood perfusion to the kidneys is necessary to ensure urine formation. When arterial blood pressure drops too low, the renal arteries do not have enough pressure cause glomerular filtration
● Relationship to blood pressure Glomerular capillary blood pressure is the driving force of glomerular filtration
Low blood pressure Hemhorrage leads to low production of urine
Adequate blood perfusion to the kidneys is necessary to ensure urine formation. When arterial blood pressure drops too low, the renal arteries do not have enough pressure cause glomerular filtration
● Capillary fluid balance at renal tubule As fluid passes down the kidney tubules, 90% of the water in it is reabsorbed, which takes place in the collecting tubes.
The kidney tubule regulation of the salt and water in our bodies is the most important factor in determining urine volume. Too much water and salt in our bodies is dangerous and too little water and salt is dangerous. Therefore, the level of water and salts excreted in urine
- the urine volume - is adjusted to the needs of the body.
○ reabsorption ○ Reabsorpti on of essential nutrients, water, and electrolytes into the peritubular capillaries ○ Control of pH and electrolytes
○ secretion Secretion is the transport of materials from the interstitial fluid into the renal filtrate. It is essentially reabsorption in reverse. The process is important for getting rid of substances not already in the filtrate. Waste products such as ammonia, some creatinine, and the end products of medications move from the blood in the capillaries around the renal tubules into the interstitial fluid. They are then taken in by the cells of the tubules and deposited into the renal filtrate to be eliminated in the urine.
● patency Check the patency or openness of the tube and flow of urine.
● motility Intestinal motility, Insufficient activity Cholenergics: increase tone and motility of bladder. Decreased gastric motility.
Aldosterone RAAS Erythropoietin Conversion of Vitamin D
It is because as women age the levels of the hormone estrogen decrease and can cause menopause.
Capillary fluid balance- Could relate to the reabsorption and secretion but it is less likely than the other ones.
● urinary retention Urinary retention, also known as ischuria, is an inability to completely empty the bladder. It is a common complication of benign prostatic hyperplasia (BPH), though it can also be caused by: Nerve dysfunction. Tethered spinal cord syndrome.
Factors it relates to and how it relates Regulates Water Retention & Blood Pressure.
Decrease in GFR. So it deals with Filtration
● urinary urgency Urinary urgency is a sudden, compelling urge to urinate. It is often, though not necessarily, associated with urinary incontinence, polyuria, nocturia, and interstitial cystitis. It tends to increase with age. When uncontrollable, it causes urge incontinence.
Factors it relates to and how it relates Filtration (GFR)
Capillary fluid balance at renal tubule
Might also be with hormonal control
● urinary frequency Frequent urination, or urinary
frequency, is the need to urinate more often than usual. It is often, though not necessarily, associated with urinary incontinence and polyuria (large total volume of urine).
Factors it relates to and how it relates Could be filtration, capillary fluid balance at renal tubule because reabsorption and secretion
● anuria Failure of the kidneys to produce urine.
Factors it relates to and how it relates Patency, filtration, control center, capillary fluid balance.
● oliguria Production of abnormal small amounts of urine.
Factors it relates to and how it relates Filtration, Hormonal control, capillary fluid balance and integrity of tissues probably.
● Polyuria Excessive or large amounts of urine.
Factors it relates to and how it relates Filtration, patency, motility integrity of tissues Hormonal control.
● micturition Micturition syncope or post-micturition syncope is the name given to the human phenomenon of fainting shortly after or during urination. It is a type of vasovagal response.
Factors it relates to and how it relates Filtration, hormonal control and maybe capillary fluid balance. These relate by the micturition of the urine.
● Calculi Kidney stones, or renal calculi, are solid masses made of crystals. Kidney stones
the urine tubes. Hormonal control because of ADH and Aldosterone.
Significance of findings of common diagnostic test for urinary function:
● Urinalysis ● Straw colored with mild odor o Normal urine, specific gravity 1.010 to 1. ● Cloudy o May indicate the presence of large amounts of protein, blood, bacteria, and pus ● Dark color o May indicate hematuria, excessive bilirubin, or highly concentrated urine ● Unpleasant or unusual odor o Infection or result from certain dietary components or medication
Urinary casts Indicate inflammation of kidney tubules (and protein) Specific gravity Indicates ability of tubules to concentrate urine Low specific gravity— dilute urine (with normal hydration) High specific gravity— concentrated urine (with normal hydration)
- Related to renal failure Glucose and ketones Found when diabetes mellitus is not well controlled
● Culture and Sensitivity ● Culture and sensitivity studies on urine specimens o Identifica tion of causative organism of infection o Help select appropriate drug treatment
● BUN ● Elevated serum urea and serum creatinine levels o Indicate failure to excrete nitrogen wastes ▪Caused by decreased GFR
● Creatinine Creatinine is a waste product from the normal breakdown of muscle tissue. As creatinine is produced, it's filtered through the kidneys and excreted in urine. Doctors measure the blood creatinine level as a test of kidney function.
● Total protein The total protein test measures the total amount of two classes of proteins found in the fluid portion of your blood. These are albumin and globulin. Proteins are important parts of all cells and tissues. Albumin helps prevent fluid from leaking out of blood vessels. Globulins are an important part of your immune system.
problem if you have too little creatinine production but not in the sense of kidney problems.
Blood tests Antibody level Antistreptolysin O or antistreptokinase titers Used for diagnosis of poststreptococcal glomerulonephriti s
Elevated renin levels Indicate kidney as a cause of hypertension
Electrolytes Depend on related fluid balance
Metabolic acidosis* Failure of tubules to control acid-base balance
Anemia* Indicates decreased erythropoietin secretion and/or bone marrow depression
*In the absence of other problems.
Other tests Clearance tests Examples: creatinine or inulin clearance Used to assess GFR Cystoscopy Visualizes lower urinary tract May be used to perform biopsy or remove kidney stones Biopsy Used to acquire tissue
specimens
Culture and sensitivity studies on urine specimens Identification of causative organism of infection Help select appropriate drug treatment
Radiologic tests Radionuclide imaging, angiography, ultrasound, CT, MRI, intravenous pyelography Used to visualize structures and possible abnormalities, flow patterns, and filtration rates
Alterations of Urinary Elimination and Sexuality
For each alteration, a. identify pathogenesis and clinical manifestations. b. ask yourself “Why” each clinical manifestation would occur. c. describe how the factors affecting urinary elimination are related to this alteration? Urinary tract infections
