Chapter 17 Urinary System Flashcards
What are the main functions of the kidneys in regulating the extracellular fluid environment?
The kidneys regulate the volume of blood plasma affecting blood pressure remove wastes balance electrolytes maintain pH and secrete erythropoietin.
Describe the path that urine takes from formation to exiting the body.
Urine is made in the kidney nephrons drains into the renal pelvis moves down the ureter to the urinary bladder and then passes through the urethra to exit the body transported by peristalsis.
What are the two distinct regions of the kidney and what structures are involved in urine drainage?
The kidney has the renal cortex and renal medulla (made of renal pyramids and columns). Each pyramid drains into a minor calyx then a major calyx and finally the renal pelvis.
What are kidney stones (nephrolithiasis) and what factors increase their formation?
Kidney stones are hard objects formed in the kidneys from crystallized minerals or waste products most commonly calcium stones. Dehydration increases the tendency to form stones.
How can kidney stones affect urine flow and cause pain?
Large stones in the calyces or pelvis can obstruct urine flow and smaller stones (usually less than 5 mm) passing into a ureter can produce intense pain.
What muscles and neurons control the urinary bladder and urethral sphincters?
Detrusor muscles in the bladder wall are lined with smooth muscle connected by gap junctions and innervated by parasympathetic neurons releasing acetylcholine on muscarinic receptors. The internal urethral sphincter is smooth muscle and the external urethral sphincter is skeletal muscle.
What role do stretch receptors in the bladder play in controlling urination?
Stretch receptors send signals to the S2-S4 spinal cord regions which normally inhibit parasympathetic nerves to detrusor muscles and stimulate somatic motor neurons to the external urethral sphincter producing the guarding reflex to prevent involuntary emptying.
What happens during the voiding reflex initiated by bladder stretch?
Information about bladder stretch passes to the micturition center in the pons activating parasympathetic neurons that cause detrusor muscle contraction leading to urination.
What causes the internal urethral sphincter to relax during urination?
Inhibition of sympathetic innervation causes the internal urethral sphincter to relax.
How can a person control the urge to urinate?
The person feels the need to urinate but can control it with the external urethral sphincter.
What is urinary incontinence and what are some common causes?
Urinary incontinence is uncontrolled urination due to loss of bladder control and can be caused by factors like weakened pelvic floor support in women or treatments for prostate cancer in men.
What characterizes stress urinary incontinence and why does it commonly occur in women?
Stress urinary incontinence occurs when urine leaks due to increased abdominal pressure (like sneezing coughing laughing) and commonly occurs in women when the pelvic floor no longer adequately supports the urethra due to childbirth or aging.
How is stress urinary incontinence often treated in women?
It is often treated by sling surgery where inserted mesh provides additional support for the urethra.
What is the nephron and what is its primary function in the kidney?
The nephron is the functional unit of the kidney consisting of small tubules and associated blood vessels where blood is filtered fluid enters the tubules is modified and leaves as urine.
Describe the main segments of the nephron tubules that filtrate passes through to become urine.
Filtrate passes through the glomerular Bowman’s capsule proximal convoluted tubule loop of Henle (descending and ascending limbs) distal convoluted tubule and finally the collecting duct.
What makes up the renal corpuscle in the nephron?
The renal corpuscle is made up of the glomerulus and the glomerular Bowman’s capsule.
What are the characteristics of the capillaries in the glomerulus and what is their role?
The capillaries are fenestrated with large pores that allow water and solutes to pass but not blood cells and plasma proteins enabling filtration of blood to form filtrate.
Through what layers must the filtrate pass in the glomerular corpuscle?
Filtrate passes through capillary fenestrae glomerular basement membrane and the visceral layer of the glomerular capsule composed of podocytes with pedicles.
What forces contribute to the formation of filtrate in the glomerular capsule?
Hydrostatic pressure of the blood colloid osmotic pressure and the permeability of capillaries produce a net filtration pressure of about 10 mmHg.
What is the glomerular filtration rate (GFR) and why is it significant?
GFR is the volume of filtrate produced by both kidneys each minute typically 115 to 125 ml filtering the total blood volume every 40 minutes indicating kidney efficiency.
How is glomerular filtration rate regulated?
Filtration rate is regulated by vasoconstriction or dilation of afferent arterioles controlled by extrinsic regulation via the sympathetic nervous system and intrinsic regulation via internal kidney signals.
What happens to the afferent arterioles during a fight-flight reaction and why?
During a fight-flight reaction the afferent arterioles undergo vasoconstriction to help divert blood to the heart and muscles decreasing urine formation to compensate for the drop in blood pressure.
How does renal autoregulation maintain glomerular filtration rate (GFR) when blood pressure fluctuates?
Renal autoregulation maintains GFR at a constant level by dilating the afferent arterioles if blood pressure drops below 70 and constricting them if blood pressure is normal or increased.
What role do smooth muscles in the arterioles play in renal autoregulation?
Smooth muscles in the arterioles sense an increase in blood pressure and respond with myogenic constriction causing afferent arterioles to constrict to regulate GFR.
