Urinary System Anatomy and Functions

The primary functions of the kidney are to filter blood and convert filtrate into urine.

The four layers of kidney tissue from innermost to outermost are: fibrous capsule, perinephric, renal fascia, and paranephric.

The fibrous capsule of the kidney is composed of dense irregular connective tissue.

<p>The perinephric layer of the kidney is adipose connective tissue that provides cushioning and stabilization.</p> Signup and view all the answers

<p>The renal fascia is composed of dense irregular connective tissue which anchors the kidney to surrounding structures.</p> Signup and view all the answers

<p>The paranephric layer is composed of adipose connective tissue which provides cushioning and stabilization.</p> Signup and view all the answers

<p>Failure of the supportive tissue in the kidney would undermine its structural and functional integrity. It could lead to impaired filtration, increased susceptibility to injury and infection, and potentially irreversible kidney damage.</p> Signup and view all the answers

<p>Both sympathetic and parasympathetic nerves innervate the kidney.</p> Signup and view all the answers

<p>The parenchyma of the kidney is composed of the renal cortex and the renal medulla.</p> Signup and view all the answers

<p>The renal cortex is the outer layer of the kidney and contains renal corpuscles.</p> Signup and view all the answers

<p>The renal medulla is the inner layer of the kidney and contains renal pyramids and collecting ducts.</p> Signup and view all the answers

<p>Renal columns are inward extensions of the renal cortex that dip down between the renal pyramids and renal medulla.</p> Signup and view all the answers

<p>A renal pyramid is a cone-shaped structure located within the renal medulla. It contains the nephron loop, the tip of which is called the renal papilla.</p> Signup and view all the answers

<p>A nephron is the functional unit of the kidney. It is responsible for filtering blood and producing urine.</p> Signup and view all the answers

<p>A renal corpuscle is an expanded portion of a nephron, located within the renal cortex. It consists of a glomerulus and a Bowman's capsule.</p> Signup and view all the answers

<p>A glomerulus is a network of capillaries located within the Bowman's capsule.</p> Signup and view all the answers

<p>Bowman's capsule has two layers: a visceral layer and a parietal layer.</p> Signup and view all the answers

<p>The capsular space is the space located between the visceral and parietal layers of Bowman's capsule. It receives the filtrate formed during glomerular filtration.</p> Signup and view all the answers

<p>The renal tubule makes up the remainder of the nephron. It is responsible for reabsorbing and secreting substances to refine the filtrate.</p> Signup and view all the answers

<p>The proximal convoluted tubule is the first portion of the renal tubule. It is lined with simple cuboidal epithelium.</p> Signup and view all the answers

<p>The nephron loop is a U-shaped structure located between the proximal and distal convoluted tubules. It extends into the medulla, and is divided into an ascending limb and a descending limb.</p> Signup and view all the answers

<p>The distal convoluted tubule is the final segment of the renal tubule. It is lined with simple cuboidal epithelium.</p> Signup and view all the answers

<p>The two types of nephrons are cortical nephrons and juxtamedullary nephrons.</p> Signup and view all the answers

<p>Cortical nephrons are located towards the periphery of the renal cortex and their renal corpuscle is located near the edge.</p> Signup and view all the answers

<p>Juxtamedullary nephrons are located adjacent to the cortico-medullary junction and their renal corpuscle is located nearby.</p> Signup and view all the answers

<p>Collecting tubules drain the DCT and collect urine from multiple nephrons. Multiple collecting ducts eventually convey the urine to the renal pelvis.</p> Signup and view all the answers

<p>The two specialized epithelial cell types found within the collecting tubules and collecting ducts are principal cells and intercalated cells.</p> Signup and view all the answers

<p>Principal cells contain receptors for aldosterone and antidiuretic hormone, which regulate water reabsorption and maintain urine pH.</p> Signup and view all the answers

<p>Intercalated cells are specialized epithelial cells that regulate urine pH and blood pH by removing excess acid or base.</p> Signup and view all the answers

<p>The juxtaglomerular apparatus is an important structure of the kidney, crucial for regulating filtrate formation and regulating systemic blood pressure.</p> Signup and view all the answers

<p>Granular cells are modified smooth muscle cells of the afferent arteriole that are located near the entrance to the renal corpuscle.</p> Signup and view all the answers

<p>Granular cells are responsible for synthesizing, storing, and releasing renin.</p> Signup and view all the answers

<p>Macula densa cells are modified epithelial cells found in the wall of the distal convoluted tubule, where they are adjacent to the granular cells.</p> Signup and view all the answers

<p>Macula densa cells detect changes in the concentration of sodium chloride in the tubular fluid. They signal the granular cells to release renin, which ultimately helps regulate blood pressure and GFR.</p> Signup and view all the answers

<p>The two fluid flow patterns in kidney function involve: the flow of blood into and out of the kidney, and the flow of filtrate, tubular fluid, and urine through the nephron and other urinary structures.</p> Signup and view all the answers

<p>The afferent arteriole is the vessel that supplies blood to the glomerulus.</p> Signup and view all the answers

<p>The efferent arteriole is the vessel that carries blood away from the glomerulus.</p> Signup and view all the answers

<p>Peritubular capillaries are tiny blood vessels that intertwine around the proximal and distal convoluted tubules.</p> Signup and view all the answers

<p>Vasa recta are specialized blood vessels that are associated with the nephron loop, a U-shaped structure in the medulla.</p> Signup and view all the answers

<p>Filtrate is blood plasma minus the large solutes. It is formed during glomerular filtration and is the initial stage of urine formation.</p> Signup and view all the answers

<p>Tubular fluid is the filtrate after it has entered the proximal convoluted tubule and undergone some reabsorption.</p> Signup and view all the answers

<p>Urine is the final product of the filtration and reabsorption processes that occur within the nephron. It is the fluid that is collected from the collecting ducts and transported to the ureters.</p> Signup and view all the answers

<p>The three main processes of urine formation are glomerular filtration, tubular reabsorption, and tubular secretion.</p> Signup and view all the answers

<p>Filtrate production occurs within the renal corpuscle, a structure located within the renal cortex.</p> Signup and view all the answers

<p>Urine is formed through three interrelated processes: filtration, reabsorption, and secretion.</p> Signup and view all the answers

<p>Glomerular filtration is the movement of substances from the blood within the glomerulus into the Bowman's capsule.</p> Signup and view all the answers

<p>Tubular reabsorption is the movement of substances from the tubular fluid back into the blood.</p> Signup and view all the answers

<p>Tubular secretion is the movement of substances from the blood into the tubular fluid.</p> Signup and view all the answers

<p>The filtration membrane is a porous, thin, negatively charged structure that acts as a filter, allowing only certain substances to pass from the blood into the filtrate.</p> Signup and view all the answers

<p>The three layers of the filtration membrane are the endothelium of the glomerulus, the basement membrane, and the visceral layer of Bowman's capsule.</p> Signup and view all the answers

<p>The endothelium of the glomerulus forms the innermost layer of the filtration membrane. It is a fenestrated layer, meaning it has pores that allow plasma and dissolved substances to pass through, while preventing the passage of larger formed elements like red blood cells.</p> Signup and view all the answers

<p>The basement membrane of the glomerulus is a porous layer composed of glycoproteins and proteoglycans. It serves as a selective barrier, restricting the passage of large plasma proteins, such as albumin, while still allowing smaller molecules to pass.</p> Signup and view all the answers

<p>The visceral layer of the glomerular capsule is the outermost layer of the filtration membrane and is composed of podocytes, which are specialized cells with foot-like processes called pedicels. The pedicels wrap around the glomerular capillaries and are separated by filtration slits, which act as the final barrier for filtration.</p> Signup and view all the answers

<p>Mesangial cells are specialized smooth muscle cells that are located between capillary loops in the glomerulus.</p> Signup and view all the answers

<p>Mesangial cells produce extracellular matrix to support the glomerulus, release growth factors to promote glomerular development, release molecules to mediate inflammation, and contract to decrease the surface area of the filtration membrane.</p> Signup and view all the answers

<p>Substances are filtered through the filtration membrane based on three categories: freely filtered, not filtered, and limited filtration.</p> Signup and view all the answers

<p>Freely filtered substances are small substances that are not bound to proteins. Examples include glucose, water, amino acids, ions, urea, and small hormones.</p> Signup and view all the answers

<p>Substances that are not filtered include formed elements like red blood cells, white blood cells, and platelets, as well as large proteins.</p> Signup and view all the answers

<p>Limited filtration applies to substances that are too large or negatively charged, making them less likely to pass through the filtration membrane.</p> Signup and view all the answers

<p>When a substance becomes trapped in the filtration membrane, mesangial cells phagocytize the macromolecules. This helps maintain the cleanliness of the filtration membrane by removing trapped substances.</p> Signup and view all the answers

<p>The renal corpuscle is influenced by three pressure gradients: glomerular hydrostatic pressure, blood colloid osmotic pressure, and capsular hydrostatic pressure.</p> Signup and view all the answers

<p>Glomerular hydrostatic pressure (HPg) is the blood pressure within the glomerulus.</p> Signup and view all the answers

<p>Blood colloid osmotic pressure (OPg) is the osmotic pressure exerted by the dissolved proteins in the blood.</p> Signup and view all the answers

<p>Capsular hydrostatic pressure (HPc) is the pressure within the Bowman's capsule.</p> Signup and view all the answers

<p>Net Filtration Pressure (NFP) is calculated as: NFP = HPg - (OPg + HPc).</p> Signup and view all the answers

<p>A positive NFP indicates that the pressure driving fluid and solutes out of the glomerulus (HPg) is greater than the forces opposing it (OPg + HPc). This results in net filtration, allowing fluid to move from the blood into the Bowman's capsule.</p> Signup and view all the answers

<p>A negative NFP indicates that the forces opposing filtration (OPg + HPc) are greater than the pressure promoting filtration (HPg). This results in net reabsorption, where fluid moves from the Bowman's capsule back into the blood.</p> Signup and view all the answers

<p>GFR is the rate at which filtrate is formed in the glomerulus, typically measured in milliliters per minute.</p> Signup and view all the answers

<p>Net Filtration Pressure (NFP) is directly proportional to Glomerular Filtration Rate (GFR). This means that an increase in NFP leads to an increase in GFR, and vice versa.</p> Signup and view all the answers

<p>All of the above.</p> Signup and view all the answers

<p>Increased filtrate reabsorption.</p> Signup and view all the answers

<p>Macula densa cells are specialized sensory cells that monitor the concentration of sodium chloride (NaCl) in the tubular fluid. They provide feedback to the juxtaglomerular apparatus, indirectly regulating blood pressure and GFR.</p> Signup and view all the answers

<p>The two primary factors influencing GFR are the luminal diameter of afferent arterioles and the surface area of the filtration membrane in the glomerulus.</p> Signup and view all the answers

<p>Intrinsic control of GFR refers to mechanisms within the kidneys themselves that regulate GFR, independent of external factors.</p> Signup and view all the answers

<p>Extrinsic control of GFR refers to mechanisms outside the kidneys that regulate GFR. These include nervous system regulation and hormonal regulation.</p> Signup and view all the answers

<p>Renal autoregulation is the intrinsic ability of the kidneys to maintain a constant GFR despite changes in systemic arterial blood pressure.</p> Signup and view all the answers

<p>Renal autoregulation relies on two main mechanisms: the myogenic response and tubuloglomerular feedback. The myogenic response is triggered by stretching of the smooth muscle in the afferent arteriole, leading to vasoconstriction or vasodilation to regulate blood flow. Tubuloglomerular feedback is initiated by macula densa cells, which monitor NaCl levels and signal the juxtaglomerular apparatus to adjust blood flow.</p> Signup and view all the answers

<p>The myogenic response is the contraction and relaxation of smooth muscle in response to stretch. When systemic blood pressure rises, the afferent arteriole stretches, causing the smooth muscle to contract and constrict the vessel. This reduces blood flow into the glomerulus and helps maintain a stable GFR. Conversely, when blood pressure falls, the afferent arteriole relaxes, allowing for greater blood flow and maintaining GFR.</p> Signup and view all the answers

<p>Tubuloglomerular feedback is a mechanism that involves the interaction between macula densa cells in the distal convoluted tubule and granular cells in the afferent arteriole. When NaCl levels in the tubular fluid increase, macula densa cells signal to granular cells, leading to the release of renin. Renin initiates the renin-angiotensin-aldosterone system, which ultimately constricts the afferent arteriole, decreasing GFR and maintaining homeostasis.</p> Signup and view all the answers

<p>Renal autoregulation is most effective at maintaining a stable GFR when mean arterial blood pressure falls within a &quot;normal&quot; range, typically between 80 and 180 mmHg. However, when blood pressure falls below this range (hypotension) or rises significantly above it (hypertension), renal autoregulation may become less effective.</p> Signup and view all the answers

<p>Sympathetic stimulation, often triggered by stress or emergency, can decrease GFR through vasoconstriction. This decrease in GFR is mediated by the release of renin from granular cells, which activates the renin-angiotensin-aldosterone system, ultimately reducing blood flow into the glomerulus and decreasing filtration.</p> Signup and view all the answers

<p>Atrial natriuretic peptide (ANP), released from the heart in response to increased blood volume or blood pressure, increases GFR by dilating the afferent arteriole, inhibiting the release of renin, and promoting vasodilation of the efferent arteriole. These actions increase blood flow to the glomerulus, facilitating filtration and promoting the excretion of water and sodium, thereby reducing blood volume.</p> Signup and view all the answers

<p>The kidneys produce urine at a constant rate despite fluctuations in systemic blood pressure, ensuring that waste products and excess fluids are effectively eliminated from the body.</p> Signup and view all the answers

<p>The myogenic response detects changes in blood pressure within the afferent arteriole, causing the smooth muscle to contract or relax, thereby regulating blood flow to the glomerulus. Tubuloglomerular feedback monitors sodium chloride levels in the tubular fluid, providing a regulatory mechanism that adjusts blood flow to the glomerulus based on the filtrate composition. Working together, these two mechanisms ensure that the kidney maintains a stable GFR despite fluctuations in blood pressure.</p> Signup and view all the answers

<p>Renal autoregulation is the intrinsic ability of the kidneys to maintain a constant GFR, despite changes in systemic blood pressure. This is achieved through two primary mechanisms: the myogenic response and tubuloglomerular feedback. When systemic blood pressure decreases, the afferent arteriole dilates, increasing blood flow and maintaining GFR. Conversely, when blood pressure increases, the afferent arteriole constricts, decreasing blood flow and maintaining GFR.</p> Signup and view all the answers

<p>Maintaining a constant GFR is crucial for the kidneys to effectively filter waste products and toxins from the blood. A stable GFR ensures that the kidneys are able to regulate blood volume and electrolyte balance, maintaining the homeostasis of the body's internal environment.</p> Signup and view all the answers

<p>The sympathetic nervous system is responsible for stimulating the release of renin, which ultimately leads to vasoconstriction of blood vessels. This reduces blood flow to the kidney and decreases urine production. In contrast, the parasympathetic nervous system promotes the release of acetylcholine, which triggers vasodilation and increases blood flow to the kidney, potentially increasing urine production.</p> Signup and view all the answers

<p>Aldosterone is a steroid hormone produced in the adrenal cortex. It plays a critical role in regulating sodium and water reabsorption by the kidneys, ultimately impacting blood pressure.</p> Signup and view all the answers

<p>ANP is a hormone released from the heart, particularly the atria, in response to increased blood volume or blood pressure. It promotes the excretion of sodium and water by inhibiting sodium reabsorption in the kidneys, ultimately lowering blood pressure.</p> Signup and view all the answers

<p>Water reabsorption in the kidneys occurs through two pathways: paracellular transport between cells and transcellular transport through aquaporins. Paracellular transport involves water moving between cells due to osmotic pressure differences. Transcellular transport involves water moving through aquaporins, specific protein channels that allow for the passage of water across cell membranes.</p> Signup and view all the answers

<p>The primary site of water reabsorption in the nephron is the proximal convoluted tubule (PCT).</p> Signup and view all the answers

<p>Obligatory water reabsorption refers to the movement of water out of the proximal convoluted tubule (PCT) that follows the movement of sodium. This movement is driven by osmosis, as water passively follows sodium, which is actively reabsorbed along the osmotic pressure gradient.</p> Signup and view all the answers

<p>ADH is a hormone released from the posterior pituitary gland in response to dehydration. It promotes water reabsorption by binding to receptor cells in the collecting tubules and ducts, increasing the permeability of these tubules to water. This results in greater water reabsorption, concentrating the urine and conserving fluids in the body.</p> Signup and view all the answers

<p>ADH increases water reabsorption by binding to receptors on principal cells in the collecting tubules and ducts. This binding triggers a cascade of events, including the migration of vesicles containing aquaporins (water channels) to the cell membrane. The increased number of aquaporins enhances water permeability, allowing for increased water reabsorption into the blood.</p> Signup and view all the answers