Urinary System

What is the function of the urinary system in humans?

To remove wastes and water from the body, maintaining homeostasis.

List the organs included in the urinary system.

Kidneys, ureters, urinary bladder, and urethra.

What are the major functions of the kidneys?

Removal of metabolic wastes, regulation of fluid and electrolyte balance, regulation of acid-base balance, maintenance of blood pressure, regulation of erythropoiesis, and performing metabolic functions.

Describe the retroperitoneal position of the kidneys.

The kidneys are located behind the peritoneal membranes against the posterior abdominal wall.

What is the role of the nephron in the kidney?

Nephrons filter blood and produce urine through filtration, reabsorption, and secretion.

What are the main structures of the nephron?

The nephron consists of the renal corpuscle (glomerulus and Bowman's capsule) and renal tubules (proximal tubule, nephron loop, distal tubule, and collecting duct).

What is the function of the renal corpuscle?

The renal corpuscle filters blood to form filtrate, which is the first step in urine formation.

What is the significance of the proximal tubule in the nephron?

The proximal tubule reabsorbs the majority of filtered water, electrolytes, and nutrients back into the bloodstream.

Describe the nephron loop (Loop of Henle) structure.

The nephron loop includes a descending limb that is permeable to water and an ascending limb that is impermeable to water but allows for sodium reabsorption.

How do collecting ducts function in the nephron?

Collecting ducts adjust water reabsorption in response to hormones like ADH and help concentrate urine.

What is the role of the juxtaglomerular cells in nephrons?

Juxtaglomerular cells regulate blood pressure and glomerular filtration rate by releasing renin.

What distinguishes juxtamedullary nephrons from cortical nephrons?

Juxtamedullary nephrons have long nephron loops that extend deep into the medulla, playing a crucial role in concentration of urine, whereas cortical nephrons have shorter loops primarily located in the renal cortex.

What are the three major physiological processes of homeostasis performed by the kidneys?

Glomerular filtration, tubular reabsorption, and tubular secretion.

Define glomerular filtration.

The process of filtering blood in the renal corpuscle, forming filtrate.

What is the average glomerular filtration rate (GFR)?

About 125 ml/min.

What is the primary function of the filtration membrane in the kidneys?

To filter blood and prevent larger molecules, such as proteins and blood cells, from passing into the urine.

What barriers constitute the filtration membrane in the kidneys?

The glomerular capillary endothelial cells, basal lamina, and podocytes.

What is the role of glomerular capillary endothelial cells in the filtration membrane?

They provide a porous barrier that allows water and small solutes to pass while restricting larger molecules.

What is the function of the basal lamina in the filtration membrane?

It acts as a filter that prevents the passage of proteins and supports filtration by providing structural integrity.

What are podocytes and their role in the filtration membrane?

Podocytes are specialized cells that wrap around glomerular capillaries and have foot-like processes that create slits, further restricting larger particles.

What is the process of filtration in the kidneys?

The process by which blood is filtered in the renal corpuscle to produce filtrate, consisting of water, electrolytes, and small solutes.

What is the first step in glomerular filtration?

Blood enters the glomerulus through the afferent arterioles.

What is formed in Bowman's capsule after filtration?

The filtrate, which consists of water, electrolytes, and small waste molecules.

What factors influence glomerular filtration rate (GFR)?

Blood pressure, permeability of the filtration membrane, and surface area available for filtration.

What role do mesangial cells play in glomerular filtration?

Mesangial cells help regulate blood flow within the glomerulus and support the structure of the filtration barrier.

How does the diameter of the afferent arterioles affect glomerular filtration?

Constriction of afferent arterioles decreases blood flow and lowers GFR, while dilation increases blood flow and raises GFR.

What happens to larger molecules during glomerular filtration?

Larger molecules, such as proteins and blood cells, are retained in the bloodstream and do not enter the filtrate.

What is the significance of hydrostatic pressure in glomerular filtration?

Hydrostatic pressure in the glomerulus drives the filtration process by pushing water and solutes through the filtration membrane.

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

The filtration membrane acts as a barrier that selectively allows small molecules to pass while blocking larger ones.

What is glomerular filtration pressure (GFP)?

The net pressure that drives fluid from the glomerular capillaries into Bowman's capsule, influencing the rate of filtration.

What components contribute to glomerular filtration pressure?

Glomerular filtration pressure is influenced by the hydrostatic pressure of blood in the glomerulus and the osmotic pressure of blood plasma.

What is the hydrostatic pressure in the glomerulus?

The pressure exerted by blood within the glomerular capillaries, typically around 55 mmHg, driving filtration into Bowman's capsule.

How does colloid osmotic pressure affect glomerular filtration?

Colloid osmotic pressure opposes filtration, as it pulls water back into the capillaries, generally around 30 mmHg in glomerular plasma.

What is the importance of capsular hydrostatic pressure in glomerular filtration?

Capsular hydrostatic pressure (about 15 mmHg) opposes filtration by exerting pressure against the filtration membrane in Bowman's capsule.

What is the net filtration pressure (NFP)?

NFP is calculated by subtracting the opposing pressures (osmotic and capsular) from the glomerular hydrostatic pressure, influencing GFR.

What determines the glomerular filtration rate (GFR)?

GFR is determined by net filtration pressure, the surface area available for filtration, and the permeability of the filtration membrane.

How does the renal blood flow influence glomerular filtration pressure?

Increased renal blood flow raises hydrostatic pressure in the glomerulus, enhancing glomerular filtration rate.

What is the effect of dehydration on glomerular filtration pressure?

Dehydration can decrease renal blood flow, leading to reduced hydrostatic pressure in the glomerulus and lower GFR.

What is the role of the juxtaglomerular apparatus (JGA)?

To regulate blood pressure and glomerular filtration rate.

How do the kidneys regulate blood pressure?

Through control of blood volume and release of the enzyme renin.

What is urine composed of?

Water, electrolytes, and metabolic wastes.

What is nephron loop's significance in urine concentration?

It allows for varying permeability and helps maintain osmotic gradient for water reabsorption.

How does aldosterone affect the kidneys?

Promotes sodium reabsorption and potassium secretion in the distal tubule and collecting ducts.

What is the function of antidiuretic hormone (ADH)?

Increases water reabsorption in the collecting ducts by promoting aquaporin insertion.

What happens to urine concentration when ADH is increased?

Urine becomes more concentrated.

What type of epithelium lines the urinary bladder?

Transitional epithelium.

What is micturition?

The process of discharging urine from the urinary bladder.

What reflex controls micturition?

The micturition reflex, mediated by the parasympathetic nervous system.

What is the function of the ureters?

To transport urine from the kidneys to the urinary bladder.

What role do the vasa recta play in the kidneys?

They act as a countercurrent exchanger to maintain the osmotic gradient.

How do the kidneys help maintain acid-base balance?

By adjusting the secretion and reabsorption of hydrogen and bicarbonate ions.

What is renal clearance?

The rate at which the kidneys remove a substance from the blood, used to estimate GFR.

What is the primary waste product excreted in urine?

Urea, a product of protein metabolism.

What determines the concentration of urine?

The amount of water reabsorbed during the final stages of urine formation.

What triggers the release of renin?

Decreased blood flow to the kidneys.

What is the effect of sympathetic nervous system activation on the kidneys?

It decreases GFR by constricting afferent arterioles.

How do the kidneys respond to low blood pressure?

By activating the renin-angiotensin-aldosterone system to increase blood volume and pressure.

What triggers the secretion of atrial natriuretic peptide (ANP)?

Increased blood volume.

What is the impact of ANP on kidney function?

It decreases blood volume and promotes diuresis by increasing GFR.

What is obligatory water reabsorption?

The reabsorption of water that occurs automatically in response to solute reabsorption in the proximal tubule.

What is facultative water reabsorption?

The variable reabsorption of water in the distal tubule and collecting ducts, regulated by hormones.

How does the osmolarity of filtrate change in the nephron loop?

It becomes more concentrated in the descending limb and less concentrated in the ascending limb.

Describe how urea contributes to urine concentration in the kidneys.

Urea diffuses into the medullary interstitial fluid, aiding in the creation of the osmotic gradient.

How does the body respond to metabolic acidosis?

The kidneys excrete more hydrogen ions and reabsorb bicarbonate to help raise blood pH.

What substances are commonly checked in a urinalysis?

Glucose, proteins, leukocytes, and ketones.

What are the two major types of transport processes in renal tubules?

Paracellular and transcellular transport.

What happens during the micturition reflex?

Stretch receptors activate parasympathetic pathways causing detrusor muscle contraction and sphincter relaxation.

What is the significance of the trigone region of the bladder?

It plays a role in preventing backflow of urine from the bladder into the ureters.

What is the difference in the urethra between males and females?

The male urethra is longer and serves both urinary and reproductive functions, while the female urethra is shorter and serves only urinary functions.

What physical actions contribute to urine elimination during micturition?

Contraction of the detrusor muscle and relaxation of the internal and external urethral sphincters.

How do hormones influence the kidney's function?

Hormones like aldosterone and ADH regulate sodium and water reabsorption, affecting blood volume and pressure.

What changes occur in renal function when the secretion of aldosterone is inhibited?

Sodium reabsorption decreases, leading to increased urine output and possible electrolyte imbalance.

What is the general structure of the urinary bladder?

The urinary bladder is a hollow, muscular organ that stores urine before excretion.

What type of muscle makes up the bladder wall?

The bladder wall is made up of smooth muscle, allowing for expansion and contraction.

What is the name of the muscle that surrounds the bladder?

The detrusor muscle.

What is the function of the detrusor muscle?

The detrusor muscle contracts to expel urine from the bladder during micturition.

What is the role of the transitional epithelium in the bladder?

Transitional epithelium allows the bladder to stretch and accommodate varying volumes of urine.

What anatomical feature prevents backflow of urine from the bladder into the ureters?

The trigone region, formed by the openings of the ureters and urethra.

How do the ureteral openings contribute to bladder function?

They are positioned in a way that prevents backflow during bladder contraction.

What is the significance of the urethral sphincters in bladder function?

The internal and external urethral sphincters control the release of urine from the bladder.

What structure does the urethra connect to the bladder?

The urethra connects at the bladder neck, where urine is stored until excretion.

What is the primary function of the urethra in the urinary system?

The urethra serves to transport urine from the bladder to the external environment.

What types of epithelium line the urethra?

The urethra is lined with transitional epithelium near the bladder, transitioning to stratified squamous epithelium as it reaches the external opening.

What is the average length of the male urethra?

The male urethra is approximately 18 to 20 centimeters long.

What is the average length of the female urethra?

The female urethra is about 4 to 5 centimeters long.

What are the three segments of the male urethra?

The male urethra is divided into the prostatic, membranous, and spongy (penile) urethra.

Which segment of the male urethra passes through the pelvic floor?

The membranous urethra passes through the pelvic floor.

What surrounds the male urethra in the penis?

The spongy (penile) urethra is surrounded by erectile tissue called the corpus spongiosum.

What anatomical feature prevents urine leakage in males?

The internal urethral sphincter, which is under involuntary control.

What role do the external urethral sphincters play in both males and females?

The external urethral sphincters provide conscious control over urine