EXAM 6: Urinary Flashcards
List several functions of the kidneys. (7)
Filtration: The kidneys filter waste products and excess substances from the blood to form urine.
Regulation of Blood Pressure: Through the renin-angiotensin-aldosterone system (RAAS).
Acid-Base Balance: The kidneys regulate the body’s pH by excreting hydrogen ions and reabsorbing bicarbonate.
Electrolyte Balance: The kidneys regulate levels of sodium, potassium, calcium, and other electrolytes.
Erythropoiesis Regulation: The kidneys release erythropoietin, which stimulates red blood cell production.
Detoxification: Removal of metabolic waste products, drugs, and toxins from the blood.
Water Balance: Regulation of fluid levels through reabsorption of water in the nephron.
Name the general structures in the urinary tract.
Kidneys: Filter blood and produce urine.
Ureters: Tubes that transport urine from the kidneys to the bladder.
Bladder: Stores urine until excretion.
Urethra: The tube that carries urine from the bladder out of the body.
Identify the following regions/terms as they relate to the kidney: renal capsule, cortex, medulla, retroperitoneal location, hilum, pyramids, sinus, pelvis, calyces, columns.
Renal Capsule: A fibrous membrane that surrounds and protects the kidney.
Cortex: The outer layer of the kidney that contains the renal corpuscles and proximal/distal convoluted tubules.
Medulla: The inner part of the kidney, containing the renal pyramids.
Retroperitoneal Location: The kidneys are located behind the peritoneum, outside the abdominal cavity.
Hilum: The area on the medial side of the kidney where blood vessels, nerves, and the ureter enter/exit.
Pyramids: Cone-shaped structures in the medulla, where urine is collected.
Sinus: The cavity inside the kidney that contains the renal pelvis and calyces.
Pelvis: The funnel-shaped cavity where urine collects before entering the ureter.
Calyces: Tubes that collect urine from the renal pyramids and funnel it into the renal pelvis.
Columns: Extensions of the renal cortex that separate the renal pyramids.
Know the names of blood vessels in the path of blood through the kidney.
Renal Artery: Carries oxygenated blood to the kidney.
Segmental Arteries: Branches of the renal artery that supply different parts of the kidney.
Interlobar Arteries: Run between the renal pyramids.
Arcuate Arteries: Arch over the base of the renal pyramids.
Interlobular Arteries: Branch off the arcuate arteries and supply the cortical regions.
Afferent Arterioles: Supply blood to the glomerulus for filtration.
Glomerulus: A network of capillaries where filtration occurs.
Efferent Arterioles: Carry blood away from the glomerulus.
Peritubular Capillaries: Surround the tubules and help with reabsorption and secretion.
Venous System: Blood returns via the interlobular veins, arcuate veins, and interlobar veins, eventually to the renal vein, which empties into the inferior vena cava.
What is a renal corpuscle? How does the filtrate moves through the nephron? Where does filtration, secretion, and reabsorption occur .
Renal Corpuscle: The functional unit of the kidney, consisting of the glomerulus (a network of capillaries) and Bowman’s capsule (the surrounding structure that captures the filtrate).
Bowman’s Capsule: Filtrate enters from the blood in the glomerulus.
Proximal Convoluted Tubule (PCT): Major site for reabsorption of water, ions, glucose, and amino acids (occurs in the cortex).
Loop of Henle: Descends into the medulla and then ascends. It helps concentrate urine by reabsorbing water and salts.
Distal Convoluted Tubule (DCT): Further adjustment of ion concentrations and water (occurs in the cortex).
Collecting Ducts: Collect urine from multiple nephrons and pass it through the medulla to the renal pelvis.
Filtration: Occurs in the glomerulus (renal corpuscle).
Reabsorption: Occurs in the PCT, loop of Henle, and DCT.
Secretion: Occurs primarily in the DCT and collecting ducts to eliminate additional waste and ions into the urine.
Identify the difference in layout of the cortical and juxtamedullary nephrons. Which type is more numerous in the human? How do they differ in their urine concentrating ability?
Cortical Nephrons: The majority of nephrons, with their glomeruli located in the outer cortex. They have shorter loops of Henle.
Juxtamedullary Nephrons: Less common, with glomeruli located near the medulla. They have long loops of Henle that help in the concentration of urine, allowing for greater water reabsorption and the ability to produce concentrated urine.
Urine Concentration Ability: Juxtamedullary nephrons are more specialized for concentrating urine, whereas cortical nephrons are more involved in filtration and reabsorption.
Describe the glomerulus, and the 3 anatomical barriers to filtration. Be able to qualitatively describe the composition of the filtrate compared to whole blood. What percentage of renal plasma is filtered? What is the force that drives filtration?
Glomerulus: A network of capillaries located in the renal corpuscle of the nephron. It functions as the site for blood filtration, where blood pressure forces plasma and small solutes into the Bowman’s capsule, forming the filtrate.
Fenestrated Endothelium: The capillary walls have pores that allow small molecules to pass but restrict larger cells (e.g., blood cells).
Basement Membrane: A gel-like matrix between the endothelial cells and podocytes that restricts the passage of large proteins based on size and charge.
Podocytes: Specialized epithelial cells that cover the glomerular capillaries. Their foot processes form filtration slits that further restrict larger molecules from entering the filtrate.
Composition of Filtrate: The filtrate contains water, electrolytes, glucose, amino acids, and waste products like urea, but lacks larger proteins and blood cells.
Percentage of Renal Plasma Filtered: About 20% of the plasma that enters the kidney is filtered into the renal corpuscle.
Force Driving Filtration: Glomerular Hydrostatic Pressure (GHP), the blood pressure within the glomerulus, is the main force that drives filtration.
Which part of the nephron is most suited to high volume reabsorption and give a structural adaptation for this function.
- The proximal convoluted tubule (PCT) is most suited to high-volume reabsorption.
- Structural Adaptation: The PCT has microvilli (forming a brush border) on its epithelial cells that greatly increase the surface area for the reabsorption of water, ions, glucose, and amino acids. Additionally, it has numerous mitochondria for energy required in active transport processes.
What are peritubular capillaries? Describe their location with regard to the nephron. Describe the special vasa recta. Where are they found?
Peritubular Capillaries: These are small capillaries that surround the proximal and distal convoluted tubules and are involved in the reabsorption of water and solutes from the filtrate back into the bloodstream.
Location: They are located in the cortex of the kidney, adjacent to the nephron’s tubules.
Vasa Recta: These are long, straight capillaries that run parallel to the Loop of Henle in juxtamedullary nephrons. They play a critical role in maintaining the medullary concentration gradient needed for water reabsorption and urine concentration.
Location: The vasa recta are found in the medulla of the kidney, near the juxtamedullary nephrons.
Identify the cells which are part of the juxtaglomerular apparatus. What are their functions? What happens during the juxtaglomerular reflex?
Juxtaglomerular Apparatus (JGA): A structure located where the distal convoluted tubule passes near the afferent arteriole of the glomerulus.
Cells in the JGA:
Macula Densa Cells: Located in the distal tubule, these cells monitor sodium chloride concentration in the filtrate.
Juxtaglomerular (Granular) Cells: Found in the afferent arteriole, these cells secrete renin in response to low blood pressure or low sodium levels.
Juxtaglomerular Reflex: When the macula densa detects low sodium levels, it signals the granular cells to release renin. This initiates the renin-angiotensin-aldosterone system (RAAS), leading to vasoconstriction, increased aldosterone secretion, and ultimately increased blood pressure to restore homeostasis.
Describe the lining of the ureter and how peristalsis plays a role. What is special about the mucosal lining here?
Ureter Lining: The ureter is lined by transitional epithelium, which is capable of stretching as the ureter expands to accommodate the passage of urine from the kidneys to the bladder.
Peristalsis: Peristaltic waves in the muscular layer of the ureter help propel urine from the renal pelvis to the bladder, even against gravity. This smooth, coordinated contraction ensures continuous flow of urine.
Special Feature of Mucosal Lining: The transitional epithelium allows the ureter to stretch and maintain a protective barrier to prevent backflow or irritation from the acidic urine. It also has a lamina propria (connective tissue layer) that supports the epithelium and allows for further expansion.
Describe the entry of ureters into the bladder. Describe the shape and appearance of the bladder, and name its specialized mucosal lining. What is the trigone? How is it different structurally?
Entry of Ureters: The ureters enter the bladder at an oblique angle, passing through the detrusor muscle of the bladder wall. This creates a one-way valve to prevent backflow of urine.
Bladder Shape and Appearance: The bladder is a hollow, muscular organ with a distensible shape, able to expand as it fills with urine. The shape can vary depending on the volume of urine and the surrounding anatomy.
Mucosal Lining: The bladder is lined by transitional epithelium, which allows for stretching.
Trigone: A triangular area on the inner surface of the bladder, located between the two ureteral openings and the internal urethral orifice. It is more rigid and less distensible than the rest of the bladder wall. The trigone acts as a funnel, directing urine to the urethra during urination.
How can any type of ureteral blockage affect kidney function?
Ureteral Blockage: A blockage in the ureter (such as a kidney stone or a tumor) can lead to urinary retention in the kidney, causing hydronephrosis (swelling of the kidney due to urine buildup).
- This increases renal pressure and can lead to damage or atropy of the kidney tissue, impairing kidney function and potentially leading to renal failure if not resolved.
Identify the urethra; differences in male and female urethra.
- The urethra is the tube that carries urine from the bladder to the outside of the body.
Differences in Male and Female Urethra:
Male Urethra: Longer (about 18-20 cm), runs through the prostate gland, and has three parts: prostatic, membranous, and spongy (penile) urethra. The male urethra also serves as a passage for semen during ejaculation.
Female Urethra: Shorter (about 4 cm) and opens directly above the vaginal opening. It only serves the function of excreting urine.
Identify the internal and external urethral sphincters; the type of muscle in each sphincter. How does that relate to their different function?
Internal Urethral Sphincter: This sphincter is made of smooth muscle and is involuntary. It is located at the junction of the bladder and the urethra and helps control the release of urine by maintaining bladder pressure until urination is initiated.
External Urethral Sphincter: This sphincter is made of skeletal muscle and is voluntary, allowing conscious control over urination. It is located in the pelvic floor and can contract to prevent urination when desired.
