Urinary System Overview

The kidneys dispose of waste products, regulate blood pressure, stimulate red blood cell production, and convert vitamin D.

The kidneys are located behind the parietal peritoneum, against the dorsal body wall, between the 12th rib and L3 vertebrae. The right one is slightly lower.

Adult kidneys are about 12 cm long and 6 cm wide and have a medial indentation called the renal hilum.

The medial indentation of a kidney where the ureter, blood vessels, and nerves connect to or exit the kidney.

Nitrogenous wastes, toxins, drugs, and excess ions are eliminated by the kidneys.

A substance produced by the kidneys that helps maintain healthy blood pressure.

A substance produced by the kidneys to stimulate red blood cell production.

The kidneys convert vitamin D into its active form.

The structural and functional unit of the kidneys, each kidney contains millions of nephrons.

The first part of a nephron, consists of a glomerulus and a Bowman's capsule.

The second part of a nephron, responsible for filtering waste and reabsorbing useful substances.

Part of the nephron. Filters blood to create urine.

Nephrons located primarily in the renal cortex.

Nephrons in the renal medulla and critical for concentrating urine.

Part of the nephron that collects urine from multiple nephrons.

A capillary network within the renal corpuscle, filters blood.

The process of urine elimination from the bladder, involving muscular contractions and voluntary sphincter control.

Blood composition is influenced by three major factors: diet (what you eat), cellular metabolism (how your body utilizes fuel), and urine output (how much waste is excreted).

Kidneys play crucial roles in maintaining blood composition: 1) excreting nitrogenous wastes, 2) balancing water, 3) balancing electrolytes, and 4) regulating blood pH.

Fluid located within cells, comprising two-thirds of the body's total fluid volume.

Fluid outside cells, including blood plasma, interstitial fluid, lymph, and transcellular fluid.

The process where blood is filtered in Bowman's capsule, separating waste products and water from the blood.

The first part of the renal tubule where most reabsorption of water, glucose, amino acids, and electrolytes occurs.

A low-pressure capillary network surrounding the renal tubules, involved in reabsorption and secretion.

The blood vessel carrying blood away from the glomerulus.

The blood vessel carrying blood to the glomerulus.

The final part of the renal tubule, where fine-tuning of electrolyte balance and pH occurs.

A specialized structure where the afferent arteriole meets the DCT, regulating blood pressure.

The state where water intake equals water output, keeping the body properly hydrated.

Water comes from ingested foods and fluids, as well as metabolic processes producing water.

The driving force for water intake, triggered by changes in plasma solute concentration and a dry mouth.

Specialized cells in the hypothalamus sensitive to changes in plasma solute concentration.

A brain region containing the thirst center, which is activated by osmoreceptors.

Water leaves the body through urine, feces, sweat, and insensible losses like breathing.

Water loss that occurs unnoticed, like through breathing and skin.

The primary route for water output, regulated by the kidneys.

Aldosterone, a hormone, regulates blood composition and volume by acting on the kidneys. It increases sodium reabsorption, causing water to follow, leading to increased blood volume and pressure.

This mechanism is the primary trigger for aldosterone release. When blood pressure drops, the juxtaglomerular apparatus in the kidneys releases renin. Renin activates reactions that produce angiotensin II, which constricts blood vessels and stimulates aldosterone release, ultimately increasing blood pressure and volume.

Angiotensin II is a powerful hormone produced by the Renin-Angiotensin mechanism. It causes vasoconstriction, narrowing blood vessels, and stimulates aldosterone release. These actions lead to increased blood pressure and volume.

Small changes in electrolyte concentrations cause water to shift between fluid compartments. For example, when sodium ions are reabsorbed in the kidney, water follows passively, increasing blood volume.

Sodium reabsorption in the kidneys is crucial for water balance. For every sodium ion reabsorbed, a chloride ion also follows, and water passively follows sodium, contributing to increased blood volume.

Specialized structure where the afferent arteriole meets the distal convoluted tubule. It regulates blood pressure by sensing blood flow and releasing renin.

The first segment of the renal tubule where most reabsorption of water, glucose, amino acids, and electrolytes occurs. Think of it as the 'workhorse' of the nephron, responsible for reclaiming valuable substances from the filtrate.

The final segment of the renal tubule where fine-tuning of electrolyte balance and pH occurs. It is the final 'checkpoint' for adjusting the composition of the urine before it exits the nephron.

The process in which useful substances (like water, glucose, and amino acids) are taken back into the bloodstream from the renal tubule. Imagine a sieve where valuable things are recovered from the filtrate.

The process in which waste products and excess substances are moved from the blood into the renal tubule to be excreted in urine. Like actively removing 'trash' from the blood.

A specialized form of secretion, where substances like hydrogen and potassium ions, creatinine, and some drugs move from the blood into the renal tubule for elimination. Think of it as a 'last chance' to filter out harmful substances from the bloodstream.

The collecting duct collects urine from multiple nephrons and further adjusts its composition and concentration before it flows into the renal pelvis. It acts like a 'final collection point' before urine is sent to the bladder.

It surrounds the glomerulus and acts as the first stage of filtration. Think of it as the 'initial filter' for the blood, capturing everything that's too big to pass through.

The loop of Henle is a part of the nephron that descends deep into the medulla. The loop plays a critical role in regulating the concentration of urine. Think of it as the 'water regulator' of the nephron, fine-tuning the concentration of urine.

Aldosterone, a hormone, regulates blood composition and volume by acting on the kidneys. It increases sodium reabsorption, causing water to follow, leading to increased blood volume and pressure.

This mechanism is the primary trigger for aldosterone release. When blood pressure drops, the juxtaglomerular apparatus in the kidneys releases renin. Renin activates reactions that produce angiotensin II, which constricts blood vessels and stimulates aldosterone release, ultimately increasing blood pressure and volume.

Angiotensin II is a powerful hormone produced by the Renin-Angiotensin mechanism. It causes vasoconstriction, narrowing blood vessels, and stimulates aldosterone release. These actions lead to increased blood pressure and volume.

Small changes in electrolyte concentrations cause water to shift between fluid compartments. For example, when sodium ions are reabsorbed in the kidney, water follows passively, increasing blood volume.

Sodium reabsorption in the kidneys is crucial for water balance. For every sodium ion reabsorbed, a chloride ion also follows, and water passively follows sodium, contributing to increased blood volume.

The process where the renal tubules actively transport substances from the blood into the filtrate, removing excess ions, drugs, and waste products not already filtered.

Waste products containing nitrogen, like urea, uric acid, and creatinine, produced from breakdown of proteins and nucleic acids. These are poorly reabsorbed by the kidney and excreted in urine.

A nitrogenous waste product formed from the breakdown of nucleic acids (DNA and RNA).

A nitrogenous waste product formed from the breakdown of creatine, a compound primarily used in muscle.

Substances that are not reabsorbed in the renal tubules, like nitrogenous wastes, remain in the filtrate and are excreted in the urine.

Tubular secretion helps regulate blood pH by actively secreting excess hydrogen ions (H+) into the filtrate, removing them from the blood.

Materials that are left in the renal tubule after filtration and reabsorption move towards the ureter, eventually forming urine.

The kidney's reabsorption mechanisms are not designed to retrieve nitrogenous wastes, so these substances are largely excreted in urine.

The final product of urine formation, after filtration, reabsorption, and secretion, reaches the renal pelvis and then flows into the ureter.

Water intake ensures proper cell function and healthy blood volume. For example, if your body doesn't have enough water, your cells can't function properly, and your blood may become too thick. Your body functions optimally when it has the right amount of water!

A dry mouth is a signal that your body needs more water. This happens because salivary glands produce less saliva when you're dehydrated. It's like your body signaling 'I need a drink!' through your mouth.

The normal pH range of blood is between 7.35 and 7.45. Maintaining this range is crucial for proper bodily function.

A condition where blood pH is above 7.45, indicating excess alkalinity.

A condition where blood pH is below 7.35, indicating excess acidity.

Substances in the blood that resist changes in pH by either accepting or donating protons.

Acids that dissociate completely in water, releasing all of their hydrogen ions.

Acids that only partially dissociate in water, releasing fewer hydrogen ions.

Bases that readily dissociate in water and bind hydrogen ions.

Bases that bind hydrogen ions at a slower rate compared to strong bases.

A low-pressure capillary network surrounding the renal tubules. Involved in reabsorption of filtered substances back into the blood and secretion of waste.

Cone-shaped structures within the medulla of the kidney. They contain collecting ducts and contribute to urine concentration.

The process where useful substances like water, glucose, and amino acids are taken back into the bloodstream from the renal tubule.

The process where waste products and excess substances are moved from the blood into the renal tubule to be excreted in urine.

Surrounds the glomerulus and acts as the first stage of filtration in the nephron.

A part of the nephron that descends deep into the medulla and plays a critical role in regulating urine concentration.

The total amount of water in your body, typically about 60% of your body weight.

The blood's pH should remain between 7.35 and 7.45 for proper body function.

When blood pH goes above 7.45, it's called alkalosis, and when it goes below 7.35, it's called acidosis. Both are unhealthy states.

The kidneys play a critical role in maintaining the acid-base balance of the blood.

Charged particles (ions) that conduct electricity in body fluids. Important examples include sodium, potassium, and calcium.

Blood buffers are substances that minimize changes in blood pH by accepting or releasing hydrogen ions (H+).

Electrolytes are dissolved in water and are crucial for maintaining water balance within and outside cells. They help regulate fluid movement and maintain proper cell function.

Strong acids completely release H+ in water, while weak acids release fewer H+.

Strong bases readily bind H+ in water, while weak bases bind H+ at a slower rate.

Kidneys regulate blood composition, filter waste products, balance electrolytes, and regulate blood pressure.

The glomerulus, a network of capillaries within the kidney, filters blood to separate waste products and water from the blood.

By excreting excess hydrogen ions (H+) in the urine.

Lungs help regulate blood pH by releasing carbon dioxide (CO2), which is acidic.

The collecting duct, a part of the nephron, collects urine from multiple nephrons and adjusts its composition and concentration before it flows into the ureter.

Kidneys start forming in the first few weeks of pregnancy and are actively excreting urine by the third month.

Infections caused by fecal bacteria, sexually transmitted infections, and Streptococcus bacteria are common urinary issues in children and young adults.

Voluntary control of the urethra doesn't start until around 18 months of age, and nighttime control might not come until 4 years old.

A serious condition where the kidneys lose the ability to concentrate urine, requiring dialysis to maintain blood chemistry.

As we age, our kidneys filter less effectively and have difficulty concentrating urine, which can lead to frequent urination, urgency, and incontinence.

Renin is an enzyme produced by the juxtaglomerular cells in the kidneys. It plays a vital role in regulating blood pressure by initiating the Renin-Angiotensin-Aldosterone System.

Angiotensin II is a powerful hormone produced by the Renin-Angiotensin System. It causes vasoconstriction (narrowing of blood vessels) and stimulates the release of aldosterone, ultimately increasing blood pressure.

Angiotensin II causes the blood vessels to constrict. This narrowing effect increases the blood pressure, as the heart forces blood through smaller channels.

Aldosterone, a hormone produced by the adrenal glands, increases sodium reabsorption in the kidneys. This causes water to follow sodium, resulting in an increase in blood volume and, subsequently, blood pressure.

This system is activated when blood pressure drops. The juxtaglomerular cells in the kidneys detect low blood pressure and release renin, starting the cascade of events.

Baroreceptors, located in the walls of blood vessels, sense changes in blood pressure. When blood pressure drops, baroreceptors send signals to the brain to activate mechanisms that increase blood pressure, like heart rate and vasoconstriction.

The sympathetic nervous system, part of the autonomic nervous system, is activated in response to stress or low blood pressure. It triggers vasoconstriction, increasing blood pressure and heart rate.

ADH, produced by the posterior pituitary gland, increases water reabsorption in the kidneys. This action increases blood volume and contributes to maintaining blood pressure.

Both systems aim to increase blood pressure. The Renin-Angiotensin System primarily works by vasoconstriction and sodium reabsorption, while ADH focuses on increasing blood volume by retaining water.

The hypothalamus, a region in the brain, contains osmoreceptors that sense changes in blood solute concentration. When blood pressure drops, the hypothalamus triggers thirst, causing us to drink water and increase blood volume, ultimately affecting blood pressure.