BIO 308 Urinary System

What are the main components of the urinary system?

Kidneys, ureters, urinary bladder, and urethra.

What is the primary function of the kidneys?

To filter blood, remove waste products, and convert filtrate into urine.

What is the role of the ureters in the urinary system?

To transport urine from the kidneys to the urinary bladder.

What is the capacity of the urinary bladder?

It can store as much as 1 liter of urine.

What is the function of the urethra?

To eliminate urine from the body.

What processes occur as filtrate is converted to urine?

Elimination of metabolic wastes, regulation of ion levels, acid-base balance, blood pressure regulation, and elimination of biologically active molecules.

What hormone do the kidneys produce in response to low blood oxygen?

Erythropoietin (EPO).

What is the size and shape of the kidneys?

They are symmetrical, bean-shaped organs, about the size of a hand to the second knuckle.

What is the hilum of the kidney?

The concave medial border where vessels, nerves, and the ureter connect to the kidney.

Where are the kidneys located?

On the posterior abdominal wall, lateral to the vertebral column.

What is the protective structure surrounding the kidneys?

The fibrous capsule, which is dense irregular connective tissue.

What are the two regions of functional tissue in the kidney?

The outer renal cortex and the inner renal medulla.

What are renal pyramids?

Portions of the medulla divided by renal columns, with a wide base at the external edge of the medulla.

What is the renal pelvis?

The structure formed from merged major calyces.

What type of nerves innervate the kidneys?

Both sympathetic and parasympathetic nerves.

What is the nephron?

The microscopic functional filtration unit of the kidney.

What are the components of the renal corpuscle?

Glomerulus and glomerular capsule.

What is the function of the proximal convoluted tubule (PCT)?

To reabsorb substances from the filtrate, lined with simple cuboidal epithelium and microvilli.

What distinguishes cortical nephrons from juxtamedullary nephrons?

Cortical nephrons have renal corpuscles near the peripheral cortex and short nephron loops.

What is the role of the nephron loop (loop of Henle)?

To create a concentration gradient in the medulla for urine concentration.

What type of epithelium lines the distal convoluted tubule (DCT)?

Simple cuboidal epithelium without microvilli.

What is the function of the renal fascia?

To anchor the kidney to surrounding structures.

What is the paranephric fat?

The outermost layer surrounding the kidney, providing cushioning and support.

What is the function of calcitriol produced by the kidneys?

To increase the absorption of calcium from the small intestine and raise blood calcium levels.

What are juxtamedullary nephrons?

Nephrons with renal corpuscles adjacent to the corticomedullary junction and long nephron loops extending deep into the medulla.

What role do juxtamedullary nephrons play?

They help establish a salt concentration gradient in the interstitial space, allowing for regulation of urine concentration by antidiuretic hormone (ADH).

What is the function of collecting tubules and collecting ducts?

Nephrons drain into collecting tubules, which then empty into larger collecting ducts that lead to the papillary duct within the renal papilla.

What is the juxtaglomerular (JG) apparatus?

A structure that helps regulate blood filtrate formation and systemic blood pressure.

How is blood delivered to each kidney?

Blood is delivered by the renal artery, which arises from the abdominal aorta.

What are segmental arteries?

Arteries that branch from the renal artery within the renal sinus.

What do interlobar arteries do?

They branch from segmental arteries and travel through renal columns toward the corticomedullary junction.

What is the function of arcuate arteries?

They branch from interlobar arteries at the corticomedullary junction and run parallel to the base of the medullary pyramid.

What are interlobular arteries?

Also known as cortical radiate arteries, they branch from arcuate arteries and project peripherally into the cortex.

What is the role of the afferent arteriole?

It enters the renal corpuscle and forms the glomerulus, where blood plasma is filtered.

What happens at the efferent arteriole?

It carries blood exiting from the glomerulus and branches into peritubular capillaries or vasa recta.

What are peritubular capillaries?

Capillaries that intertwine around the proximal and distal convoluted tubules, primarily residing in the cortex.

What is the vasa recta?

Capillaries associated with the nephron loop, primarily residing in the medulla.

What is filtrate?

The fluid formed when blood flows through the glomerulus, filtering water and solutes into the capsular space.

What is tubular fluid?

The name for filtrate once it enters the proximal convoluted tubule (PCT) and flows through the nephron.

What is urine?

Fluid that enters the papillary duct located within the renal papilla and flows through the renal sinus to be stored and excreted.

What are the three processes involved in urine formation?

Filtration, reabsorption, and secretion.

What occurs during glomerular filtration?

Water and dissolved solutes are separated from blood plasma and enter the capsular space, forming filtrate.

What happens during tubular reabsorption?

Components move from the lumen of tubules and collecting ducts to capillaries, with vital solutes and most water being reabsorbed.

What remains in the tubular fluid after reabsorption?

Excess solutes, waste products, and some water.

How does urine exit the kidney?

Urine flows from the renal pelvis to the ureter, which connects to the urinary bladder.

What is tubular secretion?

Movement of solutes, usually by active transport, from blood into tubular fluid.

What is the role of the filtration membrane in glomerular filtration?

It is a porous, thin, negatively charged structure formed by the glomerulus and visceral layer of the glomerular capsule.

How much filtrate is produced daily by the kidneys?

180 liters of filtered plasma.

What types of substances are freely filtered by the filtration membrane?

Small substances like water, glucose, amino acids, and ions.

What substances are not filtered by the filtration membrane?

Formed elements and large proteins that cannot pass through.

What is glomerular hydrostatic pressure (HPg)?

Blood pressure in the glomerulus that pushes water and solutes out into the capsular space.

What opposes glomerular filtration?

Blood colloid osmotic pressure (OPg) and capsular hydrostatic pressure (HPc).

What does the glomerular filtration rate (GFR) measure?

The rate at which the volume of filtrate is formed, usually expressed in volume per minute.

What factors influence glomerular filtration rate (GFR)?

Luminal diameter of the afferent arteriole, surface area of the filtration membrane, and intrinsic/extrinsic controls.

What is paracellular transport?

Movement of substances between epithelial cells.

What is transcellular transport?

Movement of substances across epithelial cells using transport proteins.

What is the primary site of nutrient reabsorption in the nephron?

The proximal convoluted tubule (PCT).

How is sodium (Na+) reabsorption regulated?

By hormones such as aldosterone, which stimulates Na+ channels and Na+/K+ pumps.

What is the role of aquaporins in water reabsorption?

They facilitate water reabsorption through transcellular transport.

What happens to urine concentration when ADH levels are high?

Urine becomes more concentrated due to increased water reabsorption.

What is the main nitrogenous waste product in urine?

Urea, produced from protein breakdown.

What are renal calculi?

Kidney stones formed from crystalline minerals in the kidney.

What are common risk factors for kidney stones?

Inadequate fluid intake, frequent urinary tract infections, and abnormal chemical levels in urine.

What is incontinence?

The inability to voluntarily control urination.

What causes urinary retention?

Failure to eliminate all urine from the bladder, often due to anesthesia or enlarged prostate.

What is the composition of normal urine?

95% water and 5% solutes including salts, nitrogenous wastes, and some hormones.

What is the normal pH range of urine?

Between 4.5 and 8.0.

What is the average daily urine volume?

1 to 2 liters per day.

What is the significance of specific gravity in urine?

It indicates the density of urine compared to water, usually slightly higher due to solutes.

What is the role of the vasa recta in kidney function?

It helps maintain the solute concentration gradient through countercurrent exchange.

What is urea recycling?

The process where urea is cycled between the collecting tubule and nephron loop to help concentrate urine.

What is the effect of dehydration on ADH release?

Increased ADH release leads to more water reabsorption and concentrated urine.

What happens to ADH levels when a person is overhydrated?

ADH levels decrease, leading to less water reabsorption and diluted urine.

What is the primary function of the nephron loop?

To establish the concentration gradient of interstitial fluid necessary for water reabsorption.

What is the impact of aldosterone on sodium and water reabsorption?

It increases both sodium and water reabsorption in the nephron.

What are the main treatments for renal failure?

Dialysis or kidney transplantation.

What is the role of the collecting duct in urine formation?

It regulates water reabsorption based on hormonal signals like ADH.

What is the function of the renal corpuscle?

To filter blood and form filtrate.

What is the significance of the countercurrent multiplier?

It enhances the concentration gradient in the medulla for efficient water reabsorption.