Renal System

Kidneys function

Excretion of wastes, Regulation of blood ionic composition, blood pH, blood volume, blood pressure, blood osmolarity,blood glucose level and production of hormones. They filter blood to produce urine.

Ureters Function

to transport urine from the kidneys to the bladder for storage before excretion.

Urinary Bladder function

to store urine until it is expelled from the body.

Urethra Function

to carry urine from the bladder to the outside of the body for excretion.

Anatomy of Kidneys

The kidneys (2) are bean-shaped organs located in the lower back that filter blood to produce urine. They regulate fluid balance, electrolyte levels, and waste elimination.

Renal capsule

The renal capsule is a tough, fibrous membrane that surrounds and protects each kidney, providing structural support and maintaining organ shape.

Adipose capsule

The adipose capsule is a layer of fat tissue that surrounds the kidneys, providing cushioning and insulation.

Renal fascia

The renal fascia is a layer of connective tissue that anchors the kidneys to surrounding structures and provides additional support and protection.

Renal cortex

The renal cortex is the outer region of the kidney, located between the renal capsule and the renal medulla, containing nephrons and playing a crucial role in filtering blood and producing urine.

Renal medulla

The renal medulla is the inner region of the kidney, situated beneath the renal cortex. It contains the renal pyramids and is involved in the concentration of urine and the transport of urine to the renal pelvis.

Parenchyma

The parenchyma refers to the functional tissue of the kidney, primarily composed of nephrons, which are responsible for filtering blood and forming urine.

Nephrons

Functional units of the kidney responsible for filtering blood and producing urine, composed of a renal corpuscle and renal tubules.

Papillary ducts

the final segments of the nephron's collecting system, located in the renal medulla, that transport urine from the renal pyramids to the minor calyces.

Minor and Major Calyces

are funnel-shaped structures in the kidney that collect urine from the papillary ducts and channel it into the renal pelvis for drainage into the ureter.

Renal pelvis

the funnel-shaped structure that collects urine from the major calyces and channels it into the ureter for transport to the bladder.

Nephron

the functional unit of the kidney responsible for filtering blood and forming urine, consisting of a renal corpuscle and a renal tubule.

Glomerulus

a network of tiny blood vessels located within the renal corpuscle of the nephron, where the filtration of blood occurs.

Bowmans/Glomerular capsule

the cup-like structure that surrounds the glomerulus in the nephron, facilitating the filtration of blood and collection of filtrate.

Renal Tubule

the portion of the nephron responsible for processing the filtrate from the glomerulus, which includes segments called the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

Renal Corpuscle

the structural unit of the nephron consisting of the glomerulus and Bowman's capsule, where blood filtration begins.

Proximal Convoluted tubule (PCT)

the first segment of the renal tubule that reabsorbs water, ions, and nutrients from the filtrate back into the bloodstream.

Nephron Loop/Loop of henle

the section of the renal tubule that creates a concentration gradient in the medulla, enabling the reabsorption of water and ions, consisting of descending and ascending limbs.

Distal Convoluted tubule (DCT)

the segment of the renal tubule that further adjusts the filtrate composition through reabsorption and secretion processes, leading to the collecting ducts.

Collecting Duct (CD)

a portion of the renal tubule that finalizes the urine concentration by reabsorbing water and sodium, influenced by hormones such as aldosterone and antidiuretic hormone (ADH).

Visceral Layer

of the Bowman's capsule that intimately surrounds the glomerulus, consisting of specialized podocytes that facilitate the filtration of blood into the nephron.

Parietal Layer

the outer layer of Bowman's capsule that provides structural support and protection, not directly involved in the filtration process. Consists of simple squamous epithelium.

Proximal Convoluted tubule

the first segment of the renal tubule where a majority of nutrient reabsorption occurs, including glucose, amino acids, and ions, as well as water.

Simple cuboidal epithelial cells

that line the proximal convoluted tubule, facilitating reabsorption through microvilli for increased surface area.

Macula densa

a group of specialized cells in the distal convoluted tubule that detect changes in sodium chloride concentration and regulate glomerular filtration rate.

Juxtaglomerular apparatus

a structure formed by the juxtaglomerular cells and macula densa that regulates blood pressure and kidney function by secreting renin. JGA is composed of juxtaglomerular cells, macula densa, and extraglomerular mesangial cells.

Principal cells

are the main type of cells in the collecting ducts of the kidneys, responsible for the regulation of water and sodium reabsorption in response to hormonal signals such as aldosterone.

Intercalated cells

are specialized cells in the collecting ducts of the kidneys that play a key role in acid-base balance by secreting or reabsorbing hydrogen ions and bicarbonate.

Simple filtration

is the process by which blood plasma is filtered through the glomerular membrane in the kidneys, allowing water, ions, and small molecules to pass while retaining larger molecules such as proteins and cells.

Selective reabsorption

is the process by which the kidneys selectively reclaim water, ions, and nutrients from the filtrate produced in the nephron, ensuring the retention of essential substances while excreting waste products.

Glomerular Filtration

is the process by which blood is filtered in the renal corpuscle, forming a filtrate that moves into the nephron for further processing. This process is crucial for the removal of waste and regulation of blood composition.

GFR and Renal Clearance

refers to the measurement of the rate at which blood is filtered through the glomeruli of the kidneys, known as the Glomerular Filtration Rate (GFR), and the ability of the kidneys to clear substances from the blood, assessing kidney function and efficiency.

Inulin

is a polysaccharide used for measuring GFR because it is freely filtered by the kidneys and not reabsorbed or secreted by the renal tubules.

Clearance > GFR

indicates that the kidneys can excrete a substance more effectively than they filter it. This can occur if the substance is actively secreted into the renal tubules or if its reabsorption is minimal.

Clearance < GFR

indicates that the kidneys filter a substance more effectively than they can excrete it, often occurring with substances that are significantly reabsorbed by the renal tubules.

Myogenic Response

is the intrinsic ability of vascular smooth muscle to respond to changes in pressure through contraction. This mechanism helps regulate blood flow to the kidneys and maintain glomerular filtration rate.

Tubuloglomerular Feedback

is a regulatory mechanism involving the juxtaglomerular apparatus that detects changes in sodium chloride concentration in the distal convoluted tubule. This feedback helps adjust glomerular filtration rate and maintains homeostasis.

Reabsorption

is the process by which kidneys recover water, ions, and nutrients from the filtrate back into the bloodstream, playing a crucial role in maintaining fluid and electrolyte balance.

Transcellular vs Paracellular

is a term used to describe two different pathways of substance transport in epithelial cells. Transcellular transport involves substances passing through the cell membranes, while paracellular transport occurs between the cells, allowing substances to diffuse through the intercellular space.

Glucose Reabsorption

is the process by which glucose is moved from the renal tubules back into the bloodstream, primarily occurring in the proximal convoluted tubule through specific transporters.

Potassium reabsoroption along the nephron

is the process by which potassium ions are reabsorbed from the filtrate in the nephron, predominantly occurring in the proximal convoluted tubule and the loop of Henle, helping to regulate potassium balance in the body.

Aldosterone

is a steroid hormone produced by the adrenal cortex that regulates sodium and potassium levels in the body by promoting sodium reabsorption and potassium excretion in the kidneys.

H2O Reabsorption

is the process by which water is reabsorbed from the renal tubules back into the bloodstream, primarily occurring in the proximal convoluted tubule and the loop of Henle, playing a crucial role in maintaining fluid balance and concentration of urine.

Decending loop of Henle

is the portion of the nephron that allows for the passive reabsorption of water while being impermeable to solutes, crucial for concentrating urine.

Ascending loop of Henle

is the segment of the nephron that is impermeable to water but allows for the active reabsorption of sodium and chloride ions, playing a vital role in the dilution of urine and the formation of the osmotic gradient in the medulla.

Secretion

is the process by which substances are actively transported from the blood into the renal tubules. This process plays a key role in the elimination of waste products and regulation of electrolyte balance.

Hydrogen ions (H+)

are actively secreted into the renal tubules, helping to regulate the body's acid-base balance by maintaining pH levels.

Potasium Ions (K+)

are crucial for maintaining cellular functions and are primarily reabsorbed in the renal tubules. They also play a significant role in the regulation of fluid balance and nerve impulses.

Creatinine

is a waste product formed from muscle metabolism and is excreted by the kidneys. Its levels in blood are used to assess kidney function.

Urine

is a liquid by-product of metabolism in humans and many animals, excreted by the kidneys and composed of water, urea, creatinine, and various ions.

Urine Composition

refers to the various substances found in urine, including water, urea, creatinine, electrolytes, and metabolic waste products.

Angiotensin 2

is a peptide hormone that plays a crucial role in regulating blood pressure and fluid balance by causing blood vessels to constrict and stimulating aldosterone secretion from the adrenal glands.

Detrusor muscles

are smooth muscle fibers of the bladder wall that contract to expel urine during urination.

Internal urethral sphincter

is a muscle located at the junction of the bladder and urethra that helps control the flow of urine by maintaining closure of the urethra until voluntary relaxation occurs.

External urethral sphincter

is a skeletal muscle surrounding the urethra that allows for voluntary control over urination, enabling an individual to initiate or stop the flow of urine.

Micturition

is the process of expelling urine from the bladder through the urethra, commonly known as urination.

Guarding Reflex/ Continence Reflex

is a neurological response that inhibits micturition, allowing for the voluntary control of urination by signaling the bladder to remain contracted until the appropriate time to void.

Voiding Reflex/ Micturition Reflex

is the neurological response that facilitates the process of micturition by signaling the bladder to contract and the external urethral sphincter to relax, allowing urine to be expelled from the body.

Cold-Induced diuresis

is the increased production of urine due to exposure to cold temperatures, often resulting from the constriction of blood vessels and increased blood pressure, which promotes kidney function.

Circulatory system

Transports blood to the kidneys for filtration

Endocrine system

Produce hormone that regulate kidney function

Digestive system

Provide nutrients some of which are processed by the kidneys and the urinary system helps maintain a healthy balance of water salts and chemical in the body by removing waste.

Renin-Aniotensin-Aldosterone Pathway (16 steps)

A hormone system that regulates blood pressure and fluid balance. It involves renin release, the production of angiotensin II, and the secretion of aldosterone to promote sodium retention and water reabsorption by the kidneys.