Human Anatomy: The Kidneys and Fluid Balance

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Questions and Answers

What percentage of body weight does water account for in men?

75%

70%

60% (correct)

50%

Which fluid compartment contains 2/3 of the body's fluid?

Transcellular fluid

Extracellular fluid

Intracellular fluid (correct)

Interstitial fluid

What triggers the thirst mechanism in the body?

An increase in plasma solute content of 2 to 3 percent (correct)

A sharp increase in blood pressure

A decrease in plasma solute content

A significant loss of extracellular fluid

What are the four major roles of the kidneys?

Excreting nitrogen wastes, maintaining water and electrolyte balance, blood pH control Signup and view all the answers

Through which routes does water leave the body?

Urine, perspiration, and respiration Signup and view all the answers

Which blood vessels directly supply the renal cortex?

Cortical radiate arteries Signup and view all the answers

What is the role of collecting ducts within the nephron?

Conveying fluids to the renal pelvis Signup and view all the answers

What is the shape of the kidneys?

Kidney-bean Signup and view all the answers

Which structure is primarily responsible for filtration in the renal corpuscle?

Glomerulus Signup and view all the answers

What structure surrounds the glomerulus in the renal corpuscle?

Bowman's capsule Signup and view all the answers

Which protective layer of the kidney is responsible for its glistening appearance?

Fibrous capsule Signup and view all the answers

What is the significance of filtration slits in the nephron?

To form a porous membrane around the glomerulus Signup and view all the answers

What is the function of the renal calyces?

Collect urine from the pyramids Signup and view all the answers

Where are the kidneys located in the human body?

Retroperitoneally in the superior lumbar region Signup and view all the answers

Where does venous drainage from the kidneys ultimately lead?

Inferior vena cava Signup and view all the answers

What part of the kidney faces towards the cortex?

Broad base of the renal pyramids Signup and view all the answers

What gives the medullary pyramids their striped appearance?

Arrangement of collecting ducts Signup and view all the answers

Which of the following about the right kidney is true?

It is slightly lower than the left kidney. Signup and view all the answers

How long is the renal tubule approximately?

3 cm Signup and view all the answers

What structure is continuous with the ureter leaving the hilum?

Renal pelvis Signup and view all the answers

What types of tissue separates the renal pyramids?

Renal columns Signup and view all the answers

What primarily differentiates cortical nephrons from juxtamedullary nephrons?

Cortical nephrons are found in the cortex while juxtamedullary nephrons are located near the cortex-medulla junction. Signup and view all the answers

What is the primary function of the peritubular capillary bed?

It absorbs solutes and water from the renal tubules. Signup and view all the answers

What role does the afferent arteriole play in the glomerulus?

It supplies blood to the glomerulus. Signup and view all the answers

Why is there a higher blood pressure in the glomerular capillaries compared to other capillary beds?

The afferent arteriole has a larger diameter than the efferent arteriole. Signup and view all the answers

What is meant by glomerular filtration?

A nonselective process where fluid passes from blood into the glomerular capsule. Signup and view all the answers

Which characteristic defines the filtrate produced in the renal tubules?

It is blood plasma without the blood proteins. Signup and view all the answers

What distinguishes the glomerulus from the peritubular capillaries?

The glomerulus is specialized for filtration. Signup and view all the answers

What happens to fluid and small solutes in the glomerular capillaries?

They are filtered into the glomerular capsule. Signup and view all the answers

Which component is NOT part of the major chemical buffer systems in blood?

Ammonium buffer system Signup and view all the answers

What happens to carbonic acid (H2CO3) when a strong acid like hydrochloric acid (HCl) is introduced?

It remains mostly intact while binding excess H+ ions. Signup and view all the answers

In the bicarbonate buffer system, what is the role of sodium bicarbonate (NaHCO3) when a strong acid is added?

It acts as a base, binding H+ ions. Signup and view all the answers

Which of the following statements correctly describes the function of the respiratory system in maintaining acid-base balance?

It eliminates carbon dioxide and regulates oxygen levels. Signup and view all the answers

What mechanism do the kidneys primarily use to manage acid-base balance in the blood?

Excreting bicarbonate ions and reabsorbing or generating new bicarbonate ions. Signup and view all the answers

How does sodium hydroxide (NaOH) affect a bicarbonate buffer solution?

It forces carbonic acid to dissociate, releasing H+ ions. Signup and view all the answers

What is the primary form in which carbon dioxide is transported in the blood?

As bicarbonate ion (HCO3). Signup and view all the answers

Which of the following components primarily stabilizes pH in the bicarbonate buffer system?

Carbonic acid (H2CO3) Signup and view all the answers

What is the role of the glomerular filters in the urinary system?

To prevent proteins and blood cells from entering the urine Signup and view all the answers

Where does tubular reabsorption primarily take place?

Proximal convoluted tubule Signup and view all the answers

Which of the following substances is primarily involved in active transport during tubular reabsorption?

Sodium ions Signup and view all the answers

What is a key function of tubular secretion in urine formation?

Elimination of certain drugs from the blood Signup and view all the answers

Which nitrogenous waste product is formed by the liver during protein breakdown?

Urea Signup and view all the answers

What is the normal range for urine pH?

6.0 to 7.0 Signup and view all the answers

What causes urine to take on an ammonia odor when allowed to stand?

Bacterial action on urine solutes Signup and view all the answers

What can cause urine to appear darker yellow?

Dehydration or high solute concentration Signup and view all the answers

Which structure prevents urine from flowing back into the ureters?

Mucosal valve-like folds Signup and view all the answers

Where in the urinary system is the trigone located?

At the base of the urinary bladder Signup and view all the answers

Which of the following solutes is NOT normally found in urine?

Glucose Signup and view all the answers

What are the ureters responsible for?

Transporting urine to the bladder Signup and view all the answers

Which part of the nephron is primarily responsible for the reabsorption of water?

Collecting duct Signup and view all the answers

Study Notes

Urinary System Overview

The urinary system is responsible for removing waste products from the body and maintaining fluid balance.
Key organs: kidneys, ureters, urinary bladder, and urethra.

Kidneys

Dark red, kidney-bean shaped organs.
Lie retroperitoneally in the superior lumbar region.
Extend from T12 to L3 vertebrae.
Protected by the lower ribs.
Right kidney is slightly lower than the left.
Adult kidney: 12 cm (5 in) long, 6 cm (2.5 in) wide, 3 cm (1 in) thick.
Convex laterally.
Renal hilum: a medial indentation where ureter, renal blood vessels, and nerves enter/exit the kidney
Three protective layers:
- Fibrous capsule: transparent, encloses the kidney.
- Perirenal fat capsule: fatty mass, cushions the kidney.
- Renal fascia: dense fibrous connective tissue, anchors the kidney and adrenal gland.
Renal Cortex: light outer region.
Renal Medulla: darker reddish-brown inner region with triangular regions called renal pyramids/medullary pyramids.
Renal Columns: cortex-like tissue that separates renal pyramids.
Renal Pelvis: a flat, funnel-shaped tube lateral to the hilum, continuous with the ureter, collecting urine from the calyces.

Blood Supply to Kidneys

Renal artery supplies the kidney.
As it reaches the hilum, it branches into segmental arteries.
Interlobar arteries pass through renal columns.
Arcuate arteries branch at the cortex-medulla junction.
Cortical radiate arteries branch off arcuate arteries, supplying the renal cortex.
Venous drainage: Cortical radiate vein -> arcuate vein -> interlobar vein -> renal vein -> IVC.

Nephrons

Structural and functional units of the kidneys, responsible for forming urine.
Each kidney has millions
Collecting ducts: collect fluids from nephrons, conveying them to the renal pelvis; run through the medullary pyramids (giving them a striped appearance); deliver the final urine product into the calyces and the renal pelvis.
Renal Corpuscle: -Glomerulus: knot of capillaries. -Bowman’s capsule: surrounds the glomerulus. -Podocytes: octopus-like cells with foot processes that form filtration slits.
Renal Tubule:
- Proximal convoluted tubule (PCT): reabsorbs water, nutrients, and ions.
- Loop of Henle: establishes osmotic gradient.
- Distal convoluted tubule (DCT): fine-tunes fluid composition, and controlled by hormones.
Capillary beds:
- Glomerulus: specialized for filtration.
  - Afferent arteriole (larger): high blood pressure forces fluid and small solutes into Bowman’s capsule.
  - Efferent arteriole (smaller): lower blood pressure in peritubular capillaries.
- Peritubular capillaries: specialized for reabsorption and secretion.

Urine Formation and Characteristics

Glomerular Filtration: nonselective passive process of fluid passing from blood into Bowman’s capsule.
Filtrate: essentially blood plasma without proteins.
Tubular Reabsorption: reclaiming essential substances from the filtrate and returning them to the blood (passive and active transport).
Tubular Secretion: moving substances from blood to the filtrate.
Nitrogenous wastes: urea, uric acid, creatinine.
Urine Characteristics:
- Volume: 1 to 1.8 L/day.
- Color: clear to deep yellow.
- Odor: slightly aromatic, may become ammonia scented.
- pH: slightly acidic (around 6).
- Specific gravity: 1.001-1.035.
Solutes present: sodium, potassium, urea, uric acid, creatinine, ammonia, bicarbonate.
Solutes absent: glucose, blood proteins, RBCs, hemoglobin, bile, pus (WBCs).

Ureter, Urinary Bladder, and Urethra

Ureters: 2 slender tubes carrying urine from kidneys to urinary bladder.
Urinary bladder: smooth, collapsible muscular sac storing urine.
- Has 3 openings: 2 ureteral orifices.
- 1 internal urethral orifice.
- Trigone: smooth triangular region of the bladder base outlined by the openings. Important clinically for infections.
Urethra: thin-walled tube carrying urine from bladder to the exterior.
- 2 sphincters: internal and external urethral sphincters.
- Male urethra is longer and has 3 parts: prostatic, membranous, spongy.
- Female urethra is shorter, only a single region and is situated between the vaginal opening and the clitoris.

Urinary System Function

Fluid, electrolyte, and acid-base balance.
Maintaining water balance.
- water intake (from food and beverages), water output (urine, perspiration, feces, & insensible losses from Lungs)
- Role of hormones ADH
Maintaining electrolyte balance.
- Crucial electrolytes: Sodium, potassium
- Role of hormone Aldosterone
Maintaining acid-base balance.
- Maintaining appropriate pH.
- Buffer Systems:
- Three Major Chemical Buffer Systems- bicarbonate, phosphate, protein buffer
  - Respiratory and Renal Mechanisms- maintain appropriate blood pH

Diseases of the Urinary System

Hydronephrosis: urine backs up into the kidney.
Oliguria: abnormally low urinary output.
Anuria: less than 100ml of urine/day.
Renal calculi: crystals formed when urine is concentrated, precipitation of salts (uric acid).
Nephrolithiasis, Ureterolithiasis , Cystolithiasis - stones in urinary tract, back pain, bacterial infections, urinary retention, alkaline urine.
Urinary tract infection (UTI): symptoms- dysuria, urinary urgency, frequency, fever, cloudy or bloody urine; Pyelonephritis, Urethritis, and Cystitis form different parts of UTI
Incontinence: inability to control urine flow
Urinary retention: inability to empty bladder.
Adult polycystic kidney disease: kidney enlargement.
Hypospadias: abnormal urethral opening.
Glomerulonephritis: inflammation of glomerulus.

Developmental Aspects

Discusses developmental aspects of the Urinary system - especially in children.

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Description

Test your knowledge about the kidneys, their structure, and function in regulating fluid balance in the human body. This quiz covers essential topics such as fluid compartments, kidney roles, and anatomical features of the renal system. Challenge yourself with questions on water regulation and the mechanisms involved.