25.3 Gross Anatomy of the Kidney
4 min read•june 18, 2024
The kidneys are bean-shaped organs crucial for maintaining homeostasis. Located in the retroperitoneal space, they filter blood, produce urine, and regulate various bodily functions. Their complex internal structure enables efficient waste removal and fluid balance.
From the to the medulla, filter blood and form urine. Blood flows through a network of arteries, capillaries, and veins, allowing for , , and . This intricate system ensures proper waste elimination and fluid regulation.
Gross Anatomy of the Kidney
External anatomy of kidneys
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- Location in retroperitoneal space between T12 and L3 vertebrae with right kidney slightly lower due to liver position
- Bean-shaped organs approximately 11 cm long, 6 cm wide, and 3 cm thick
- is a medial concavity where , , and enter/exit the kidney
- Support structures include that anchors kidney to abdominal wall, perirenal fat capsule surrounding kidney, and thin, fibrous directly surrounding kidney
- Superior pole is the upper end of kidney and inferior pole is the lower end of kidney
Internal structures of kidneys
- Renal cortex is the outer region of kidney containing (Bowman's capsules and glomeruli) and convoluted tubules (proximal and distal)
- is the inner region of kidney consisting of containing straight tubules (loops of Henle) and collecting ducts
- is a funnel-shaped structure that collects urine from major and minor and is continuous with the ureter
- Major and minor calyces are cup-shaped structures that collect urine from the tips of
- are extensions of cortex between renal pyramids
- Nephrons are the functional units of the kidney consisting of a ( and ) and a renal tubule (, , , and )
- is a cavity within the kidney that contains the renal pelvis, major calyces, and branches of renal blood vessels and nerves
Blood flow through kidneys
- Renal artery branches from abdominal aorta and carries oxygenated blood to the kidney
- branch from renal artery and supply different regions of the kidney
- branch from segmental arteries and travel between renal pyramids
- branch from interlobar arteries at the and form arcs along the base of renal pyramids
- (interlobular arteries) branch from arcuate arteries and ascend through the cortex
- branch from cortical radiate arteries and supply glomeruli in renal corpuscles
- Glomeruli are capillary networks within Bowman's capsule where occurs
- carry blood away from glomeruli and form or
- surround cortical portions of renal tubules and are sites of and secretion
- are straight capillaries that descend into and ascend from the medulla and participate in and exchange
- Venous drainage follows the reverse path of arterial supply: interlobular veins → arcuate veins → interlobar veins → segmental veins → renal vein
- Renal vein carries deoxygenated blood from the kidney and drains into the inferior vena cava
Cortical vs juxtamedullary nephrons
- are located entirely in the renal cortex, have shorter loops of Henle that extend only into the outer medulla, are surrounded by peritubular capillaries, and constitute approximately 85% of nephrons
- are located near the corticomedullary junction, have longer loops of Henle that extend deep into the medulla, are surrounded by vasa recta (straight capillaries), constitute approximately 15% of nephrons, and are important for concentrating urine
Key structures in renal regions
- Renal cortex structures include renal corpuscles (Bowman's capsules and glomeruli), proximal convoluted tubules, , and cortical collecting ducts
- Renal medulla structures include renal pyramids, loops of Henle (descending and ascending limbs), medullary collecting ducts, and vasa recta
- , located where the afferent arteriole contacts the distal convoluted tubule, plays a role in regulating blood pressure and glomerular filtration rate
Functions of renal regions
- Renal cortex functions involve filtration in renal corpuscles (Bowman's capsules and glomeruli), reabsorption of selective substances from tubular fluid in proximal and distal convoluted tubules, and secretion of selective substances into tubular fluid in proximal and distal convoluted tubules
- Renal medulla functions include concentration of urine in loops of Henle and collecting ducts through countercurrent multiplication and exchange, maintenance of medullary osmotic gradient allowing for water reabsorption in collecting ducts, and urea recycling contributing to the concentration of urine
Kidney's role in the urinary system
- The kidneys are essential components of the , which also includes the ureters, urinary bladder, and urethra
- Kidneys produce urine through filtration, reabsorption, and secretion processes
- Urine flows from the renal pelvis through the ureters to the urinary bladder for storage before being expelled through the urethra
- , consisting of a renal pyramid and its associated cortical tissue, are the functional subunits of the kidney that contribute to urine formation
Key Terms to Review (61)
Afferent Arterioles: Afferent arterioles are small blood vessels that carry blood from the renal artery into the glomeruli of the kidney's nephrons. They play a crucial role in regulating renal blood flow and controlling the filtration of blood within the kidney.
Arcuate Arteries: The arcuate arteries are a network of small blood vessels that form an arc-like pattern within the kidney. These arteries play a crucial role in the blood supply and filtration processes of the kidney, which is the focus of the 25.3 Gross Anatomy of the Kidney topic.
Bowman’s capsule: Bowman's capsule is a cup-like sac at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine. It encases the glomerulus and is involved in filtering blood plasma.
Bowman's Capsule: Bowman's capsule is a cup-shaped structure that forms the initial part of the nephron in the kidney. It is a crucial component in the process of urine formation, serving as the site where the filtration of blood takes place to produce the primary filtrate that will eventually become urine.
Calyces: Calyces are the cup-shaped structures in the kidney that collect urine before it passes into the ureter. They form part of the renal pelvis, funneling urine from the nephrons to the ureter.
Collecting Duct: The collecting duct is a key component of the kidney's nephron, the functional unit responsible for filtering blood, reabsorbing useful substances, and excreting waste. It serves as the final pathway for urine before it is expelled from the body, playing a crucial role in the regulation of fluid volume and electrolyte balance.
Cortical nephrons: Cortical nephrons are a type of nephron located primarily in the outer portion of the kidney's cortex, characterized by their short loops of Henle, which do not extend deeply into the medulla. They are responsible for most of the kidney's reabsorptive and filtrative functions.
Cortical Nephrons: Cortical nephrons are the most numerous type of nephrons found in the kidney. They are located in the outer region of the kidney, known as the renal cortex, and are responsible for the majority of the kidney's filtration and reabsorption processes.
Cortical Radiate Arteries: The cortical radiate arteries are a network of blood vessels that originate from the arcuate arteries and radiate outward into the renal cortex of the kidney. These arteries play a crucial role in distributing oxygenated blood throughout the functional units of the kidney, known as nephrons.
Corticomedullary Junction: The corticomedullary junction is the boundary between the renal cortex and the renal medulla in the kidney. It is an important anatomical landmark that delineates the transition between the outer and inner regions of the kidney.
Countercurrent multiplication: Countercurrent multiplication is a mechanism in the nephron of the kidney that enhances the concentration of urine by utilizing the opposing flow of fluid in the loops of Henle. This process allows for the efficient reabsorption of water and solutes, playing a crucial role in regulating body fluid balance and urine concentration.
Distal Convoluted Tubule: The distal convoluted tubule is a segment of the nephron, the functional unit of the kidney, located between the loop of Henle and the collecting duct. It plays a crucial role in the kidney's ability to regulate fluid volume and composition within the body.
Distal convoluted tubules: The distal convoluted tubule is a portion of the kidney nephron that lies between the loop of Henle and the collecting duct, playing a crucial role in the reabsorption of water and ions to maintain body fluid balance. It regulates pH and electrolyte levels by selective reabsorption and secretion.
Efferent Arterioles: Efferent arterioles are small blood vessels that carry blood away from the glomeruli in the kidneys. They play a crucial role in regulating the flow of blood and the filtration process within the nephrons, which are the functional units of the kidneys.
Filtration: Filtration in the context of capillary exchange is the process by which blood pressure forces fluid and small solutes through the capillary wall, leaving larger components like proteins and blood cells behind. It is a crucial mechanism for the movement of water and nutrients from blood into tissues.
Filtration: Filtration is the process by which substances are separated from a solution or mixture by passing it through a filter or membrane that allows the desired components to pass through while retaining the unwanted ones. This process is essential in various physiological contexts, including the function of epithelial tissues, capillary exchange, and the regulation of fluid volume and composition in the urinary system.
Glomerulus: The glomerulus is a network of capillaries located at the beginning of a nephron in the kidney, where blood filtration occurs. It serves as the initial step in the process of urine formation by filtering blood plasma.
Hilum: The hilum is a crucial anatomical feature of the kidney, defined as the concave surface where blood vessels, nerves, and ureters enter and exit the organ. This area serves as the primary gateway for renal blood supply and urine drainage, connecting the kidney to the vascular and urinary systems. Understanding the hilum's location and function helps clarify how kidneys maintain homeostasis by regulating fluid balance and electrolyte levels.
Interlobar Arteries: The interlobar arteries are a set of blood vessels that run between the renal lobes within the kidney. They play a crucial role in the gross anatomy and blood supply of the kidney.
Juxtaglomerular Apparatus: The juxtaglomerular apparatus is a specialized structure located at the junction between the afferent arteriole and the distal convoluted tubule of the nephron in the kidney. It plays a crucial role in the regulation of renal blood flow and the maintenance of electrolyte balance within the body.
Juxtaglomerular apparatus (JGA): The juxtaglomerular apparatus is a specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole in the kidney. It plays a crucial role in regulating blood pressure and the filtration rate of the kidneys.
Juxtamedullary nephrons: Juxtamedullary nephrons are a specific type of nephron found in the kidneys, characterized by their long loops of Henle that extend deep into the medulla. These nephrons play a crucial role in concentrating urine and conserving water.
Loop of Henle: The loop of Henle is a U-shaped tube in the nephron, within the kidney, that plays a crucial role in concentrating urine and conserving water. It accomplishes this by creating a gradient of salinity that allows for the reabsorption of water from the filtrate.
Loop of Henle: The loop of Henle is a U-shaped structure within the nephron of the kidney that plays a crucial role in the reabsorption and concentration of urine. It connects the proximal convoluted tubule to the distal convoluted tubule, and its unique structure and function are integral to the kidney's ability to maintain fluid and electrolyte balance in the body.
Major calyx: The major calyx is a large, funnel-shaped structure in the kidney that collects urine from multiple minor calyces before it drains into the renal pelvis. This part of the urinary system plays a critical role in the flow of urine, serving as a transitional area where urine is gathered from smaller collecting units and funneled towards the ureter. Each major calyx corresponds to a region of the kidney and helps maintain an efficient system for waste removal.
Merocrine secretion: Merocrine secretion is a process by which cells release their products (like enzymes or sweat) through exocytosis without losing any part of the cell's structure. It is one of the most common types of secretion in the body, involving secretory vesicles moving to the cell surface and releasing their contents into the extracellular space.
Mesangial Cells: Mesangial cells are specialized cells found within the glomerular tuft of the kidney's nephrons. They play a crucial role in maintaining the structural and functional integrity of the glomerular filtration barrier, which is essential for the kidney's ability to filter blood and produce urine.
Minor Calyx: The minor calyx is a small, funnel-shaped structure within the kidney that collects urine from the renal pyramids. It is a key component of the kidney's gross anatomy, playing a vital role in the urine collection and transport system.
Nephron: The nephron is the functional unit of the kidney, responsible for the filtration, reabsorption, and secretion of substances to form urine. It is the basic structural and functional unit that carries out the essential processes of urine formation, fluid and electrolyte balance, and the maintenance of homeostasis within the body.
Nephrons: Nephrons are the functional units of the kidney, each consisting of a glomerulus and its associated tubule, where blood filtration and urine formation occur. They play a critical role in the body's ability to regulate water and soluble substances by filtering the blood, reabsorbing what is needed, and excreting the rest as urine.
Perinephric Fat: Perinephric fat, also known as perirenal fat, is the adipose tissue that surrounds the kidneys and serves as a protective cushion. This layer of fat is significant for providing insulation and structural support to the kidneys, helping to maintain their position within the abdominal cavity. Additionally, it plays a role in energy storage and can also influence kidney function through its metabolic activities.
Peritubular capillaries: Peritubular capillaries are a network of tiny blood vessels that surround the tubules of the nephron in the kidneys, where substances are exchanged between blood and the tubular fluid. They play a crucial role in reabsorbing water and solutes back into the bloodstream from the filtrate produced in the glomerulus.
Peritubular Capillaries: Peritubular capillaries are a network of small blood vessels that surround the renal tubules in the kidneys. They play a crucial role in the filtration and reabsorption processes that occur within the nephrons, the functional units of the kidneys.
Podocytes: Podocytes are specialized epithelial cells that play a critical role in the filtration barrier of the kidney's glomerulus. They have unique foot-like extensions called pedicels that interdigitate with each other, forming filtration slits that help regulate the passage of substances from blood into urine.
Proximal convoluted tubule: The proximal convoluted tubule (PCT) is a highly coiled section of the nephron in the kidney, situated between the Bowman’s capsule and the loop of Henle. It plays a crucial role in reabsorbing essential nutrients, ions, and water from the filtrate back into the bloodstream, making it vital for maintaining homeostasis and fluid balance.
Proximal convoluted tubules (PCTs): Proximal Convoluted Tubules are the twisted segments of the nephron located in the kidney’s cortex, immediately following Bowman's capsule, where most of the reabsorption of water, ions, and nutrients from the filtered blood takes place. Their structure increases surface area to maximize reabsorption efficiency.
Reabsorption: Reabsorption is the process by which water and solutes that have been filtered out of the blood capillaries are taken back into the bloodstream. It primarily occurs in the capillaries surrounding nephrons in the kidneys, ensuring essential nutrients and water are retained by the body.
Reabsorption: Reabsorption is the process by which substances, such as water, glucose, amino acids, and ions, are selectively taken back into the bloodstream from the filtrate in the kidneys. It is a crucial mechanism that allows the body to maintain fluid balance and regulate the composition of the blood and urine.
Renal Artery: The renal artery is a major blood vessel that supplies oxygenated blood to the kidneys, which are vital organs responsible for filtering waste and excess fluid from the body. It is a crucial component in the overall functioning of the urinary system.
Renal Capsule: The renal capsule is a tough, fibrous membrane that surrounds and protects the kidney. It serves as the outermost layer of the kidney and plays a crucial role in the gross anatomy and function of this vital organ.
Renal columns: Renal columns are extensions of cortical tissue that project into the medulla of the kidney, separating the renal pyramids. They provide a pathway for blood vessels to enter and exit the cortex from the medulla.
Renal Columns: Renal columns are extensions of the renal cortex that project between the renal pyramids in the kidney. These structures play a significant role in supporting the kidney's overall architecture, separating the renal pyramids, and providing a pathway for blood vessels and nerves to reach the nephrons within the renal medulla.
Renal corpuscle: The renal corpuscle is the initial blood-filtering component of a nephron in the kidney, consisting of a glomerulus and Bowman's capsule. It functions to filter blood, beginning the process of urine formation.
Renal Corpuscles: Renal corpuscles are the fundamental structural and functional units of the kidney's filtration system. They are responsible for the initial filtration of blood to form the primary urine, which is then further processed and modified as it travels through the nephron.
Renal cortex: The renal cortex is the outer layer of the kidney where initial filtration of blood takes place. It contains nephrons, the functional units that filter waste and reabsorb essential substances back into the bloodstream.
Renal fascia: Renal fascia is a layer of connective tissue that surrounds the kidneys, anchoring them in place within the abdominal cavity. This structure is crucial for providing stability to the kidneys and separating them from surrounding organs and tissues, thus playing an important role in maintaining the overall organization of the retroperitoneal space.
Renal fat pad: The renal fat pad is a collection of fatty tissue surrounding the kidneys, providing cushioning and support against physical shock and injury. It also helps in anchoring the kidneys to their surrounding structures within the abdominal cavity.
Renal hilum: The renal hilum is the entrance gateway located on the inner concave surface of the kidney through which the renal artery enters, and the renal vein and ureter exit. It serves as a crucial passage for blood vessels, nerves, and the ureter to access or leave the kidney.
Renal Lobes: Renal lobes are the distinct anatomical subdivisions that make up the outer portion of the kidney. These lobes are the fundamental structural units of the kidney and are essential for its proper functioning.
Renal medulla: The renal medulla is the innermost part of the kidney, consisting of renal pyramids and playing a crucial role in urine formation. It contains the structures responsible for concentrating urine and regulating water and electrolyte balance, linking it closely to both the gross and microscopic anatomy of the kidney, as well as its physiological functions in maintaining homeostasis.
Renal papillae: Renal papillae are the apexes of the renal pyramids that project into the minor calyces of the kidney, where urine is funneled into these calyces before passing into the ureter. They contain openings from which urine flows, collected from the collecting ducts.
Renal pelvis: The renal pelvis is a funnel-shaped structure located within the kidney that collects urine from the collecting ducts and channels it into the ureter. This region plays a crucial role in urine transport, acting as the central hub for urine drainage from the kidney, before it enters the ureter for further movement towards the bladder. The renal pelvis is closely associated with the overall structure and function of the kidney and is vital for maintaining homeostasis within the urinary system.
Renal pyramids: Renal pyramids are cone-shaped tissues found in the kidneys, composed primarily of tubules that transport urine from the outer part of the kidney (the cortex) to the inner parts (the calyces and renal pelvis). They are instrumental in the process of urine formation and its passage into the ureter.
Renal Sinus: The renal sinus is a cavity located within the kidney that contains the renal blood vessels, nerves, lymphatic vessels, and the renal pelvis. It serves as a central hub for the structures that enter and exit the kidney.
Renal Vein: The renal vein is a blood vessel that carries deoxygenated blood from the kidney back to the inferior vena cava, the major vein that returns blood to the heart from the lower body. It is an important component of the kidney's vasculature and plays a crucial role in the kidney's function of filtering waste and excess substances from the blood.
Secretion: Secretion is the process by which cells release various substances, such as hormones, enzymes, or other molecules, to the exterior of the cell or into the extracellular space. This process is essential for various physiological functions, including digestion, excretion, and maintaining homeostasis within the body.
Segmental Arteries: Segmental arteries are a group of small arteries that branch off from the renal artery and supply blood to specific segments or regions of the kidney. They play a crucial role in the gross anatomy and vascular supply of the kidney.
Ureter: The ureter is a muscular tube that transports urine from the kidneys to the bladder. This structure is vital for the urinary system, ensuring that waste products filtered by the kidneys are properly delivered for storage before elimination. The ureters play an important role in maintaining fluid balance and excretion in the body.
Urinary System: The urinary system is responsible for the production, storage, and elimination of urine from the body. It consists of a complex network of organs and structures that work together to filter waste and excess water from the bloodstream, regulate fluid and electrolyte balance, and maintain overall homeostasis within the body.
Vasa recta: The vasa recta are a series of straight capillaries in the medulla of the kidney that run parallel to the loop of Henle. They play a critical role in the concentration and dilution of urine by participating in the counter-current exchange mechanism.
Vasa Recta: The vasa recta are a network of blood vessels found in the renal medulla of the kidney. They play a crucial role in the kidney's ability to concentrate urine and maintain the appropriate osmotic environment for reabsorption and secretion processes.