True or False? Urine is sterile.

True or False? Urine is sterile.
Pee is the best antidote for a jelly fish sting. Your bladder may rupture if you hold your pee too long. You can make someone pee the bed by putting their hand in warm water while they are asleep. You can buy a dye that turns red if you pee in the pool.

April Fools

The Urinary System p301-314 UNIT B
Chapter 13: Urinary System Section 13.1 The Urinary System p The urinary system is involved in excretion, which is the removal of metabolic wastes from the body. The function of the urinary system is to produce urine and conduct it outside the body. Why do we need it? All living cells in the body produce metabolic wastes (ammonia, CO2) which much be removed bc an accumulation would be toxic. urinary system: a type of organ system containing the kidneys, the urinary bladder, and the tubes that carry urine; eliminates metabolic wastes from the body and helps regulate the fluid balance and pH of the blood. The kidneys produce the urine, other organs store or conduct it outside the body. Kidneys: excretion and homeostasis excretion: the removal of metabolic wastes from the body. Not the same as defecation.-elimination of waste from digestive system urine: liquid waste produced by the kidneys and excreted from the body TO PREVIOUS SLIDE

Excretion Excretion – removal of (harmful) waste from the body (excess water, salts, CO2, urea) Secretion – Release of useful substance from cells within body Defecation – Removal of undigested food and bacteria via anus. (these substances have never actually entered the body proper). Elimination – waste disposal Excretory organs: skin (sweat glands excrete perspiration – water, salt, urea) Lungs ( CO2) Liver: (bile pigments from breakdown of hemoglobin) Kidneys (urine – 95%water, nitrogenous waste and inorganic salts) focus on kidney

Focus on Kidney Nitrogenous Waste: Ammonia (NH3) produced by cells during the metab (deamination) of amine group from aa. NH3 is very toxic and must be broken down before excreted. Deamination occurs in liver, also where NH3 coverted to UREA or uric acid which are much less toxic and can be excreted in urine.

Functions of the Urinary System
UNIT B Chapter 13: Urinary System Section 13.1 Functions of the Urinary System 1. Excretion of Metabolic Wastes mostly nitrogenous wastes: primarily urea, but also ammonium, creatinine, uric acid Urea is formed when ammonia produced from amino acid breakdown (NH3 combines with CO2  urea ) Some ammonia (NH3) is excreted as ammonium ion (NH4+) Creatinine is a breakdown product of creatine phosphate, a high-energy phosphate reserve molecule in muscles. Uric acid is produced from the breakdown of nucleotides High concentration of uric acid in blood can precipitate out. Crystals may accumulate in joints: Gout urea: a by-product of amino acid metabolism: break down of aa in liver release (toxic) ammonia, which liver combines with carbon dioxide to produce less toxic urea. ammonia: a product of the breakdown of amino acids in the liver; extremely toxic uric acid: produced by the breakdown of nucleotides. rather insoluble. High conc of uric acid in blood crystals ppt out, accumulate in joints. gout: a painful ailment caused by too much uric acid in the blood, which forms crystals and precipitates out in the joints TO PREVIOUS SLIDE

2. Maintenance of Water-Salt Balance: Osmoregulation
UNIT B Chapter 13: Urinary System Section 13.1 2. Maintenance of Water-Salt Balance: Osmoregulation Salts can cause osmosis (diffusion of water) into the blood, causing blood volume and blood pressure to increase Kidneys also maintain levels of other ions, such as potassium (K+), bicarbonate (HCO3-), and calcium (Ca2+), in the blood 3. Regulation of Acid-Base Balance Kidneys monitor and keep blood pH at 7.4 by excreting hydrogen ions (H+) and reabsorbing bicarbonate ions (HCO3-) Urine is usually acidic pH 6 osmoregulation: the maintenance of the appropriate balance of water and salt in the blood The kidneys help regulate the acid-base balance of the blood TO PREVIOUS SLIDE

4. Secretion of Hormones UNIT B
Chapter 13: Urinary System Section 13.1 4. Secretion of Hormones The kidneys secrete renin, an enzyme that stimulates the adrenal cortex to secrete the hormone aldosterone, which promotes the absorption of sodium ions (Na+) by the kidneys. Water is also reabsorbed along with sodium; which increases blood volume and therefore blood pressure Secrete the hormone erythropoietin (EPO) to simulate red blood cell production (erythropoiesis) when oxygen demand increases Help activate Vitamin D, a hormone-like molecule that promotes calcium (Ca2+) absorption from the digestive tract erythropoietin (EPO): a hormone secreted by the kidneys that stimulates red blood cell production Aldosterone effects the kidney to raise BP and lower potassium. Aldosterone affects the body's ability to regulate blood pressure. ... The hormone also causes the bloodstream to re-absorb water with the sodium to increase blood volume. Aldosterone is a steroid hormone. Its main role is to regulate salt and water in the body, thus having an effect on blood pressure. TO PREVIOUS SLIDE

Organs of the Urinary System:
UNIT B Chapter 13: Urinary System Section 13.1 Organs of the Urinary System: kidneys, ureters, urinary bladder, urethra. Figure 13.1 The urinary system. Urine is found only within the kidneys, the ureters, the urinary bladder, and the urethra. The kidneys are important organs of homeostasis because they excrete metabolic wastes and adjust both the water–salt and acid–base balance of the blood. How many parts can you identify? Kidneys – process urine, Ureter – transports urine to the urinary bladder, bladder – temp stores urine prior to elimination, urethra – conducts urine to exteriorBlood supply enters kidneys via renal artery (branches from descending aorta) Blood leaves from renal vein (joins inferior vena cava) _Kidneys play role in homeostasis by regulating the composition of blood and therefore tissue fluid. As uring is being produced, kidneys 1) carry out excretion of metabolic wastes, particularly nitrogenous wastes; 2) maintain normal water-salt balance of blood and as consequence, the normal blood volume and bp 3) maintain acid-base balance of blood. Also 4) have hormonal function TO PREVIOUS SLIDE

UNIT B Chapter 13: Urinary System Section 13.1 Ureters Small muscular tubes that transport urine from the kidneys to the bladder Peristaltic contractions in the ureters cause urine to enter the bladder Wall of each ureter has three layers: inner mucosa, smooth muscle layer, outer fibrous connective tissue TO PREVIOUS SLIDE

Urinary Bladder UNIT B Stores urine until it is expelled from the body
Chapter 13: Urinary System Section 13.1 Urinary Bladder Stores urine until it is expelled from the body Has three openings: two for the ureters, and one for the urethra, which drains the bladder Has two sphincters that lie close to where the urethra exits the bladder External sphincter is under voluntary control Fig 16.1 in Text book urinary bladder: part of the urinary system that stores urine until it is expelled from the body A healthy bladder can hold one and a half to two cups ( mls) of urine during the day and about four cups (800mls) at night. It is normal to pass urine five or six times a day if you drink between 6-8 glasses of fluid. The third set of muscles is the pelvic floor muscles, also referred to as the external sphincter, which surround and support the urethra. To urinate, the brain signals the muscular bladder wall to tighten, squeezing urine out of the bladder. At the same time, the brain signals the sphincters to relax. Over time, you will learn how to drink more, until you can drink between one and a half to two litres (5 to 7 cups) each 24 hours. This way your bladder will slowly learn to stretch to hold more urine. Normal adult bladder capacity is mL. A female bladder experiences a first desire to void at a volume of approximately 150 to 250 mL, a normal desire to void at 300 to 400 mL, and a strong desire to void at 400 to 600 mL. TO PREVIOUS SLIDE

UNIT B Chapter 13: Urinary System Section 13.1 Urethra Small tube opening that extends from the bladder to an external opening Removes urine from the body Males: 20 cm long; urethra carries urine and semen Females: 4 cm long; urethra carries urine (not connected to reproductive system) urethra: a small tube that extends from the urinary bladder to an external opening that removes urine from the body; in the male reproductive system, it connects to the ejaculatory ducts TO PREVIOUS SLIDE

UNIT B Chapter 13: Urinary System Section 13.1 Urination When the bladder fills with about 250 mL of urine, stretch receptors send nerve impulses to the spinal cord Motor nerve impulses from the spinal cord cause the bladder to contract and sphincters to relax, allowing urination to occur The brain controls this reflex in older children and adults, allowing urination to be delayed Figure 13.2 Urination. As the bladder fills with urine, sensory impulses go to the spinal cord and then to the brain. When urination occurs, motor nerve impulses cause the bladder to contract and internal and external sphincters to relax. TO PREVIOUS SLIDE

Kidneys: UNIT B paired, bean shaped organs Highly vascular.
Chapter 13: Urinary System Section 13.1 Kidneys: paired, bean shaped organs Highly vascular. Each covered by a tough connective tissue layer called a renal capsule Each has a depression (hilum) on the concave side where a renal artery enters and a renal vein and ureter exit Renal pelvis – upper end of ureter. Major calyces drain into pelvis Hilum - depression TO PREVIOUS SLIDE

Kidney: Internal Structure
Renal cortex (outer region) where ultrafiltration takes place. Erythropoietin produced here. Renal medulla (middle region) collecting chamber, contains cone-shaped masses called renal pyramids Renal pelvis (inner region) upper end of ureter, receives the urine from calyces. . Cortex contains about 1.25 million renal tubules, renal medulla is made up of 10 to 18 of these conical subdivisions. (pyramid) Erythropoietin glycoprotein hormone that controls erythropoiesis, or red blood cell production The pyramids consist mainly of tubules that transport urine from the cortical, or outer, part of the kidney, where urine is produced, to the calyces, or cup-shaped cavities in which urine collects before it passes through the ureter to the bladder. The point of each pyramid, called the papilla, projects into a calyx.

Renal cortex Nephron is the functional unit of the kidney.
Over 1 M/kidney. Spans medulla and cortex

Anatomy of a Nephron UNIT B
Chapter 13: Urinary System Section 13.2 Anatomy of a Nephron The kidney is composed of over 1 million nephrons, also known as renal or kidney tubules. Composed of urinary tubules and associated vessels Responsible for formation of urine Straddle renal cortex and medulla Composed of urinary tubules and associated vessels nephrons: microscopic kidney units made up of a glomerular capsule, the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and the collecting duct Figure 13.3 Anatomy of the kidney. b. An enlargement showing the placement of nephrons. TO PREVIOUS SLIDE

Nephrons: Basic structural and functional unit of the kidney.
Regulates concentration of water and solutes (like sodium salts) by: filtering the blood, reabsorbing what is needed excreting the rest as urine. Over 1M nephrons Spans medulla and cortex

Urinary Tubules UNIT B Glomerular capsule (Bowman’s capsule)
Chapter 13: Urinary System Section 13.2 Urinary Tubules Glomerular capsule (Bowman’s capsule) Inner layer composed of cells called podocytes Spaces between podocytes allow small molecules from the glomerulus to enter the glomerular capsule (Glomerular filtration) glomerular capsule: closed end of nepheron is pushed in on itself into a cuplike structure that is the initial portion of a nephron. TO PREVIOUS SLIDE

Podocytes Podocytes are cells in the Bowman's capsule in the kidneys that wrap around capillaries of the glomerulus.

Many mitochondria to supply energy for active transport (reabsorption)
UNIT B Chapter 13: Urinary System Section 13.2 Proximal convoluted tubule (PCT) Site of tubular reabsorption of water, glucose, amino acids, some salts, etc. into peritubular capillary network Lined with cuboidal epithelial cells that have packed microvilli to increase the surface area for reabsorption Many mitochondria to supply energy for active transport (reabsorption) proximal convoluted tubule: (close to glomerulus) portion of a nephron following the glomerular capsule where tubular reabsorption of filtrate occurs Microvilli form brush border. M TO PREVIOUS SLIDE

Parts of a Nephron – Urinary tubules
UNIT B Chapter 13: Urinary System Section 13.2 Parts of a Nephron – Urinary tubules Loop of the Nephron (loop of Henle) descending limb - site of reabsorption of water (permeable to water) ascending limb Site of active and passive transport of salts into medulla tissue fluid creating an osmotic gradient. (impermeable to water) loop of Henle: portion of a nephron between the proximal and distal convoluted tubules Descending – allows water to leave Ascending limb – extrudes salt is lined with simple squamous epithelium TO PREVIOUS SLIDE

Parts of a Nephron – Urinary Tubules
UNIT B Chapter 13: Urinary System Section 13.2 Parts of a Nephron – Urinary Tubules Distal convoluted tubule (DCT) Helps move molecules (hydrogen ions, ammonia, creatinine, urea, drugs, etc. ) from the blood (peritubular capillary network.) into the tubule (tubular secretion) Many mitochondria No microvilli The DCTs of many nephrons enter one collecting duct Collecting ducts carry urine to the renal pelvis distal convoluted tubule: final portion of a nephron that joins with a collecting duct Composed of cuboidal epithelial cells that lack microvilli but have many mitochondria collecting ducts: carry urine to the renal pelvis TO PREVIOUS SLIDE

Parts of a Nephron – Urinary Tubules
Collecting ducts Final reabsorption of water and excretion of urine. carry urine to the renal pelvis Under control of ADH Glomerular capsule and collecting tubules lie in renal cortex. Loop of nephrn dips into renal medulla Collecting ducts Give renal pyramids their striated appearance Know how each structure is related to function (mitochondria, brush border, small diameter) Know where each molecule is excreted/reabsorbed

Associated Vessels - Blood Supply in a Nephron
UNIT B Chapter 16: Urinary System Section 16.2 Associated Vessels - Blood Supply in a Nephron Figure 13.4 Nephron anatomy. a. You can trace the path of blood through a nephron by following the black arrows. Each nephron has it own blood supply. Blood from the renal artery branches into afferent arterioles. Filtered blood returned to the inferior vena cava via renal vein. Two capillary regions: glomerulus (ball of capillaries inside the Bowman’s capsule) Peritubular capillary network (surrounds rest of nephron) afferent arteriole carries blood from the renal artery into the glomerulus, where it divides to form a circulatory network. At the distal end of the glomerulus, the capillaries rejoin to form the efferent arteriole through which blood leaves the glomerulus. glomerulus: a knot of capillaries inside the glomerular capsule TO PREVIOUS SLIDE

Afferent Arteriole: brings blood to nephron Glomerulus: site of pressure filtration Efferent arteriole: takes blood from glomerulus to peritubular capillary network, before exiting through the renal vein BP is higher in the glomerulus bc the efferent arteriole is narrower than the afferent . The efferent arteriols takes blood  PCN, wich surrounds the rest of the nepron. Then gloood goes into a vennule that joins with renal vein. Peritubular cap network has smaller diameter than the afferent arteriole

Peritubular Capillary Network: Surrounds tubules of nephron and reabsorbs useful material. Site of oxygen/carbon dioxide exchange (for kidney cells) Drains into renal venules

UNIT B Chapter 13: Urinary System Section 13.2
Figure 13.4 Nephron anatomy. TO PREVIOUS SLIDE

Urine Formation Blood passing through kidneys are cleaned and filtered
Useful materials are retained and potentially harmful wastes are excreted. The waste forms urine Humans produce about 1 mL/min Urine formation occurs in the nephrons as molecules are exchanged between blood vessels (glomerulus and peritubular network) and urinary tubules (proximal convoluted tubules, loop of Henle, distal convoluted tubule).

UNIT B Chapter 13: Urinary System Section 13.2 Urine Formation Urine formation is divided into the following processes: Pressure filtration (glomerular filtration) : water, salts, nutrients, and wastes move from the glomerulus to the inside of the glomerular capsule Selective (tubular) reabsorption: nutrient and salt molecules are actively reabsorbed from the convoluted tubules into the blood of the peritubular capillary network Tubular secretion: certain molecules are actively secreted from blood (peritubular capillary network) into the convoluted tubules pressure filtration: part of urine formation; occurs when whole blood enters the afferent arteriole and the glomerulus selective reabsorption: part of urine formation; occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network tubular excretion: part of urine formation; a way by which substances are removed from blood in the peritubular network and added to the tubular fluid TO PREVIOUS SLIDE

Figure 13.5 Processes in urine formation. The three main processes in urine formation are described in boxes and colour-coded to arrows that show the movement of molecules into or out of the nephron at specific locations. In the end, urine is composed of the substances within the collecting duct (see blue arrow). TO PREVIOUS SLIDE

1. Glomerular (Pressure) Filtration
UNIT B Chapter 13: Urinary System Section 13.2 1. Glomerular (Pressure) Filtration Pressure filtration occurs when blood enters the afferent arteriole and the glomerulus. pressure forces small molecules to leave the glomerulus and enter the glomerular capsule These filterable blood components form the glomerular filtrate Afferent arteriole entering glomerulus is larger than efferent art leaving it. This pressure forces small molecules to leave the glomerulus and enter the Bowman’s capsule Larger molecules remain in blood and move out of glomerulus into efferent arteriole. If urine was composed of the same materils as the glomerular filtrate, the body would continulally lose water and nutrients. These substances have been forece out of the blood due to their small siazea nd the pressure in the glomerulus. This would result in death from dehydration, starvation andlow BP. Obsiously the composition of the filtrate must be altered as it passes throughthe remainder of the nephrn on its way to the collecting duct. TO PREVIOUS SLIDE

2. Selective (Tubular) Reabsorption
UNIT B Chapter 13: Urinary System Section 13.2 2. Selective (Tubular) Reabsorption Selective reabsorption of useful materials begins in the proximal convoluted tubule into the blood of the peritubular capillary network. Most Reabsorbed: Some Not: Water, ( Water glucose, Nitrogenous Waste amino acids excess salts (ions) Sodium selective reabsorption: part of urine formation; occurs as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network TO PREVIOUS SLIDE

UNIT B Chapter 13: Urinary System Section 13.2 TO PREVIOUS SLIDE

Cells of proximal convoluted tubule are specialized for reabsorption (microvilli to increase SA) and active transport (many mitochondria)

UNIT B Chapter 13: Urinary System Section 13.2 2. Selective (Tubular) Reabsorption The glomerular filtrate that enters the proximal convoluted tubule is divided into two portions. Reabsorbed filtrate components: reabsorbed from the tubule into blood Nonreabsorbed filtrate components: continue to pass through the nephron to be processed into urine (become the tubular fluid that enters the loop of Henle) Active Reabsorption: Reabsorption by Active transport involves carrier proteins, specific for certain substances Actively reabsorbed substances: Sodium, glucose, amino acids TO PREVIOUS SLIDE

Tubular Reabsorption Na+ ions are actively reabsorbed into the blood,
Most Reabsorbed: Some Not: Water, Water glucose, Nitrogenous Waste amino acids excess salts (ions) Sodium Na+ ions are actively reabsorbed into the blood, Cl- ions follow passively, results in water moving passively from tubule blood Glucose and amino acids actively reabsorbed (via carrier proteins) into the blood almost exclusively at the proximal convoluted tubule Some urea due to diffusion

3. Tubular Secretion UNIT B
Chapter 13: Urinary System Section 13.2 3. Tubular Secretion Second way substances are removed from blood in the peritubular capillary network and added to the tubular filtrate. Active transport of molecules out of blood  into Distal Convoluted Tubule Hydrogen ions, potassium ions, ammonium ions, creatinine, and certain drugs (antihistamines, penicillin) The resulting urine contains: Substances that have undergone glomerular filtration but have not been reabsorbed Substances that have undergone tubular excretion tubular excretion: part of urine formation H+ excreted when blood pH is low Creatinine from break down of creatinine phosphate in muscles. Opposite of tubular secretion: when pH of blood is high, H+ would be secreted into blood Cells of Distal Conv tubule have many mitochondria but do not require microvilli for reabsorption 38. An antibiotic such as penicillin that is taken orally is soon excreted in the urine. Since infections last for a short while, what is the best strategy for overcoming this continual loss? A. Provide another oral medication that stops cellular metabolism. B. Provide a medication that prevents the filtration of all metabolites in the kidney. C. Take a much larger single dose of penicillin. D. Take continual doses of penicillin sufficient to maintain it in the bloodstream. TO PREVIOUS SLIDE

Question 38. An antibiotic such as penicillin that is taken orally is soon excreted in the urine. Since infections last for a short while, what is the best strategy for overcoming this continual loss? A. Provide another oral medication that stops cellular metabolism. B. Provide a medication that prevents the filtration of all metabolites in the kidney. C. Take a much larger single dose of penicillin. D. Take continual doses of penicillin sufficient to maintain it in the bloodstream. D

3. Tubular secretion What would you expect to see in cells of convoluted tubules? Cells of Distal Conv tubule have many mitochondria but do not require microvilli for reabsorption

Gravity and peristalsis of smooth muscle tissue in the walls of the ureters move urine toward the urinary bladder.

Regulatory Functions of the Kidneys
UNIT B Chapter 13: Urinary System Section 13.3 Regulatory Functions of the Kidneys Osmoregulation The kidneys maintain the water-salt balance in the blood (osmoregulation). In this way, they also maintain blood volume and blood pressure. The excretion of a hypertonic urine (more concentrated than blood) depends on the reabsorption of water. This requires: Reabsorption of water Reabsorption of salt Establishment of a solute gradient Most of the salt (NaCl) in the filtrate is reabsorbed across the wall of the proximal convoluted tubules. TO PREVIOUS SLIDE

Reabsorption of Water Water is reabsorbed along length of nephron but excretion of hypertonic urine depends on action of Loop of Henle and Collecting Duct. Loop of Henle is in Renal Medulla Reabsorption of water out of loop and into blood depends on [NaCl] in renal medulla

Loop of Henle NaCl passively diffuses out of lower portion of ascending limb. And actively transported out of upper, thick portion into tubule of renal medulla. Results in high [NaCl] in renal medulla  osmotic gradient Less salt becomes available for transport as fluid moves up thick portion of ascending limb. Causing osmotic gradient witinn renal medulla: the conc of salt is greater in direction of inner medulla (water cannot leave ascending limb bc impermeable to water

This osmotic gradient (water moves out) allows for more water reabsorption
Water from interstial is absorbed quickly by blood so the salt conc stays relatively high in tissue fluid, causing more water to keep moving out of tubule. the conc of salt is greater in direction of inner medulla (water cannot leave ascending limb bc impermeable to water. Large arrow shows inner medulla has highest conc of solutes. Not due to salt bc active transport of salt does not start until fluid reachers the thinck portion of ascending lim.

1. Water Reabsorption UNIT B
Chapter 13: Urinary System Section 13.3 1. Water Reabsorption Descending loop is permeable to water [water] inside tubule > than out (due to NaCl movement). So water moves out (into tissue then capillaries) Water is reabsorbed along the whole length of the nephron, but excretion of hypertonic urine depends on reabsorption of water in Loop of Henle and Collecting Duct TO PREVIOUS SLIDE

Water Reabsorption UNIT B Ascending limb: Not permeable to water
Chapter 13: Urinary System Section 13.3 Water Reabsorption Ascending limb: Not permeable to water Solutes diffuse out of the ascending limb and into the blood of the surrounding capillaries Water is not reabsorbed TO PREVIOUS SLIDE

Water Reabsorption UNIT B Ascending limb (upper, thick portion)
Chapter 13: Urinary System Section 13.3 Water Reabsorption Ascending limb (upper, thick portion) Active transport of Na+ and passive transport of K+ and Cl- out of the ascending loop and into the blood of the surrounding capillaries No reabsorption of water Fluid enters collecting duct from distoal convoluted tubule. Isotonic to cells of renal cortex. TO PREVIOUS SLIDE

Figure 13.9 Reabsorption in the loop of Henle occurs through both active and passive transport. TO PREVIOUS SLIDE

Water Reabsorption UNIT B
Chapter 13: Urinary System Section 13.3 Water Reabsorption If the body is dehydrated (blood hypertonic), the pituitary gland releases antidiuretic hormone (ADH) Promotes water reabsorption at collecting duct  more concentrated urine ADH does this by increases the number of aquaporins (water channels) of the collecting duct Blood volume and pressure rise As blood becomes more dilute, less ADH produced (neg feedback loophomeostasis) In the absence of ADH: collecting duct is impermeable to water, and urine is dilute Diuresis - increased amount of urine (decreased water in blood) Antidiruresis - decreased amount of urine (increased blood vol) ADH adjusts the permeability off collecting ducts Reabsorption of water and ions continues from the loop of Henle to the distal convoluted tubule and the collecting duct. The reabsorption of water and ions at this point is regulated by the needs of the body. antidiuretic hormone (ADH): a hormone released by the posterior pituitary gland when the urine needs to be hypertonic to body fluids. ADHCauses water to be reabsorbed at collecting duct. aquaporins: proteins embedded in the plasma membrane

2. Reabsorption of Salt Kidneys regulate salt balance by controlling excretion and reabsorption of ions: Na +, K+, HCO3 –, Mg 2+ Usually 98% of filtered sodium is returned to blood. ~ 67% reabsorbed at proximal tubule ~ 25% reabsorbed by ascending limb of loop of Henle Remaining is reabsorbed from distal convoluted tubule and collecting duct Two hormones regulate the reabsorption of Na+ at the distal convoluted tubule: aldosterone and atrial natriuretic hormone (ANH)

2. Reabsorption of Salt UNIT B Aldosterone Secreted by adrenal cortex
Chapter 13: Urinary System Section 13.3 2. Reabsorption of Salt Figure 13.6 Juxtaglomerular apparatus. The afferent arteriole and the distal convoluted tubule usually lie next to each other. The juxtaglomerular apparatus occurs where they touch. The juxtaglomerular apparatus secretes renin, a substance that leads to the release of aldosterone by the adrenal cortex. Reabsorption of sodium ions and water then occurs. Thereafter, blood volume and blood pressure increase. Aldosterone Secreted by adrenal cortex promotes reabsorption of Na+  reabsorption of water  Blood volume and BP increase Juxtaglomerular apparatus: secretes renin, an enzyme that leads to the secretion of aldosterone from the adrenal cortex aldosterone: a hormone secreted by the adrenal cortex; promotes the excretion of K+, reabsorption of Na+ Juxtaglomerular apparatus: a region of contact between afferent art and distal conv tubues. When blood voume and therefore BP is too low for glomerular filtration, Jux App secretes renin which converts angiotensinogen into angiotensin I, then converted to Angiotensin II a powerful vasoconstrictor that also stimulates the adrenal cortex to relaes aldosternone. Reabsorption of Na+ is followed by the reablorption of water. Increasing Blood volume and BP. TO PREVIOUS SLIDE

Aldosterone When blood volume decreases, so does BP
When BP is too low for glomerular filtration, Jux Apparatus secretes renin Renin converts angiotensinogen into angiotensin I, Angiotensin-converting enzyme (in lung capillaries) then converts Angiotensin I  Angiotensin II, a powerful vasoconstrictor that also stimulates the adrenal cortex to release aldosterone, causing reabsorption of Na+ (and K+ to be excreted) resulting in reabsorption of water Increasing Blood volume and BP. Angiotensin is a powerful vasoconstrictor (constricts blood vessels) so it directly raises the blood pressure After BP rises, renin no longer needed (neg feedback )

Figure 13.7 Regulation of blood pressure and volume. Bottom: When the blood Na+ is low, low blood pressure causes the kidneys to secrete renin. Renin leads to the secretion of aldosterone from the adrenal cortex. Aldosterone causes the kidneys to reabsorb Na+, and water follows. Blood volume and pressure return to normal. TO PREVIOUS SLIDE

2. Reabsorption of Salt UNIT B Atrial natriuretic hormone (ANH)
Chapter 13: Urinary System Section 13.3 2. Reabsorption of Salt Atrial natriuretic hormone (ANH) promotes the excretion of Na+ (natriuresis) Secreted by the atria of the heart when cardiac cells are stretched due to increased blood volume Inhibits the secretion of renin and aldosterone  excretion of water into the urine  Blood volume and blood pressure decrease atrial natriuretic hormone (ANH): a hormone secreted by the atria of the heart when cardiac cells are stretched due to increased blood volume Natiuresis - excretion of sodium in the urine. TO PREVIOUS SLIDE

Figure 13.7 Regulation of blood pressure and volume. Top: When the blood Na+ is high, high blood volume causes the heart to secrete ANH. ANH causes the kidneys to excrete Na+, and water follows. The blood volume and pressure return to normal. TO PREVIOUS SLIDE

3. Establishment of a Solute Gradient
UNIT B Chapter 13: Urinary System Section 13.3 3. Establishment of a Solute Gradient Reabsorption of water at the loop of Henle and the collecting duct is due to the establishment of a solute gradient. Ascending limb: Salt (NaCl) is actively transported out of the ascending limb and into the renal medulla Less salt is available to transport as the fluid moves up the ascending limb, establishing a solute gradient that increases toward the inner medulla TO PREVIOUS SLIDE

3. Establishment of a Solute Gradient
UNIT B Chapter 13: Urinary System Section 13.3 3. Establishment of a Solute Gradient Urea moves out of the collecting duct, further contributing to the increasing solute concentration at the inner medulla Because of this solute gradient, water leaves the descending limb and the collecting duct and returns to the blood Figure 13.8 Reabsorption of water at the loop of Henle and the collecting duct. Salt (NaCl) diffuses and is actively transported out of the ascending limb of the loop of Henle into the renal medulla. Also, urea is believed to leak from the collecting duct and to enter the tissues of the renal medulla. This creates a hypertonic environment, which draws water out of the descending limb and the collecting duct. This water is returned to the circulatory system. (The thick black outline of the ascending limb means that it is impermeable to water.) The solute concentration is 300 mOsm/L in the glomerulus and peritubular capillary network. TO PREVIOUS SLIDE

Diuretics Chemicals that increase flow of urine:
Alcohol inhibits the secretion of ADH  diuresis Caffeine increases glomerular filtration rate and decreases tubular reabsorption of Na+ Drugs (water pills) for high blood pressure inhibit active transport of Na+ at the loop of the nephron or at the distal convoluted tubule  decreased water absorption  blood volume  decreased blood pressure Diuretics have been abused for quick weight loss (water loss), and by individuals attempting to pass a urine drug test Side effects: electrolyte imbalances, dehydration, death

Acid-Base Balance UNIT B The normal pH of blood is 7.4.
Chapter 13: Urinary System Section 13.3 Acid-Base Balance The normal pH of blood is 7.4. pH can be changed by the foods we eat and by metabolic processes (e.g., CO2 from cellular respiration combines with water to form carbonic acid) Several mechanisms in the body help maintain blood pH: Acid-base buffer systems Respiratory centre in the medulla oblongata Kidneys TO PREVIOUS SLIDE

Acid-Base Buffer Systems
UNIT B Chapter 13: Urinary System Section 13.3 Acid-Base Buffer Systems Bicarbonate Buffer System in blood carbonic acid (H2CO3) and bicarbonate ions (HCO3-) When the blood is too acidic (excess H+ ): When the blood is too basic (excess OH- ): These reactions prevent any significant change in blood pH The pH of the blood is maintained at 7.4 because it is buffered. Buffer: a chemical or combination of chemicals that take up excess hydrogen ions (H+) or excess hydroxide ions (OH-) Carbon dioxide, a by-product of cellular respiration, is dissolved in the blood, where it is taken up by red blood cells and converted to carbonic acid by carbonic anhydrase. Most of the carbonic acid then dissociates to bicarbonate and hydrogen ions. TO PREVIOUS SLIDE

Respiratory Centre UNIT B
Chapter 13: Urinary System Section 13.3 Respiratory Centre If the H+ concentration of the blood rises, respiratory centre in the medulla oblongata increases breathing rate. Increasing breathing rate rids the body of H+ because of the following reaction in the pulmonary capillaries: When CO2 is exhaled, the reaction shifts to the right, and H+ is reduced Excretion of CO2 by lungs helps keep the pH within normal limits, pushes reaction to right and H+ are tied up in water. When blood pH decreases, chemoreceptors in carotid bodies and aortics bodies stimulate respiratory center to increase rate and depth of breathing. When blood pH rises, resp cener is depressed and level of bicarbonate ions increase in the blood. TO PREVIOUS SLIDE

UNIT B Chapter 13: Urinary System Section 13.3 The Kidneys The kidneys can rid the body of a wide range of acidic and basic substances to adjust pH. Slower than other two but more powerful effect on pH Reabsorb bicarbonate ions (HCO3-) and excrete H+ as needed to maintain blood pH Ammonia (NH3) produced in the tubule cells also helps to buffer and remove H+ in urine: If blood is acidic, H+ excreted and biccarb ions reabsorbed. If basic, H+ not excreted, bicarb ions not reabsorbed Urine is acidic – excess of H+ are usually excreted. Ammonia produced in kidneys by deamination of aa. Phosphate also buffers H+ in urine. TO PREVIOUS SLIDE

Figure Acid–base balance. In the kidneys, bicarbonate ions (HCO3–) are reabsorbed and hydrogen ions (H+) are excreted as needed to maintain the pH of the blood. Excess hydrogen ions are buffered, for example, by ammonia (NH3). Figure Acid–base balance. In the kidneys, bicarbonate ions (HCO3–) are reabsorbed and hydrogen ions (H+) are excreted as needed to maintain the pH of the blood. Excess hydrogen ions are buffered, for example, by ammonia (NH3). TO PREVIOUS SLIDE

What happens if you drink too much water today?
What else would increase our need to pee? 1. ADH NOT released, less water reabsorbed, more urine produced (more water excreted)

Urinary Urgency One of the more common causes of urinary frequency is a urinary tract infection (bladder or prostate). Frequent urination can be caused by prolapse of the bladder (dropped bladder). Sometimes urinary frequency can be caused by stones in the urinary tract. ... Diabetes mellitus can cause frequent urination.

Hormonal Communication

True or False? Urine is sterile.

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True or False? Urine is sterile.

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