Urinary System Flashcards
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Urinary system parts
The urinary system or tract includes the kidneys, the ureters (tubes that connect the kidneys to the bladder), the bladder, and the urethra (the tube through which urine exits the body).
Kidneys
The kidneys filter the blood by removing all the substrate and waste which creates urine.
are vital organs responsible for filtering waste products and excess substances from the blood, regulating electrolyte balance, and maintaining proper hydration. Here’s a detailed look at the anatomy, function, and common kidney-related issues in canines:
Anatomy of Canine Kidneys:
Location: Canine kidneys are located on each side of the spine, just below the ribcage, towards the back of the abdominal cavity. Structure: Each kidney is bean-shaped and reddish-brown in color. They are composed of millions of tiny structures called nephrons, which are the functional units responsible for filtration. Blood Supply: The kidneys receive a rich blood supply through the renal arteries. Blood is filtered through the nephrons, and waste products are excreted while essential substances are reabsorbed back into the bloodstream. Ureters: The kidneys are connected to the urinary bladder via long, narrow tubes called ureters. These tubes transport urine from the kidneys to the bladder. Renal Pelvis: Inside each kidney, urine collects in a structure called the renal pelvis before being transported through the ureters.
Function of Canine Kidneys:
Filtration: The primary function of canine kidneys is to filter waste products, toxins, and excess substances (such as urea, creatinine, and electrolytes) from the bloodstream. Fluid Regulation: They help regulate the volume and composition of body fluids by adjusting the concentration of electrolytes and the volume of urine produced. Blood Pressure Regulation: Canine kidneys play a role in regulating blood pressure by secreting hormones such as renin, which helps control blood volume and systemic vascular resistance. Acid-Base Balance: They help maintain the body's acid-base balance by excreting acids and reabsorbing bicarbonate ions. Red Blood Cell Production: Canine kidneys produce erythropoietin, a hormone that stimulates the production of red blood cells in the bone marrow.
Common Kidney-Related Issues in Canines:
Chronic Kidney Disease (CKD): CKD is a progressive condition characterized by the gradual loss of kidney function over time. Common causes include aging, genetic predisposition, infections, and certain toxins. Acute Kidney Injury (AKI): AKI is a sudden and severe decrease in kidney function, often caused by toxins, dehydration, urinary tract obstruction, or infections. Urinary Tract Infections (UTIs): Bacterial infections of the urinary tract can affect the kidneys, leading to inflammation and potential damage if left untreated. Kidney Stones: Like humans, dogs can develop kidney stones, which are mineral deposits that form within the urinary tract. These stones can cause pain, obstruction, and infection. Congenital Disorders: Some dogs may be born with congenital kidney abnormalities or genetic predispositions to kidney diseases.
Symptoms of Kidney Issues in Dogs:
Increased thirst and urination Decreased appetite and weight loss Vomiting and diarrhea Lethargy and weakness Blood in the urine Pain or discomfort in the abdominal area Changes in coat condition (dullness or excessive shedding)
Hilus
The term “hilus” (plural: hili) refers to a specific anatomical structure found in various organs, including the kidneys, lungs, and spleen. The hilus is also known as the hilum or hilus of an organ. Here’s what it means in different contexts:
Kidney:
In the context of the kidney, the hilus (or renal hilum) refers to the medial depression or concavity on the surface of the kidney where the renal artery, renal vein, and ureter enter or exit the kidney. The renal hilum serves as the point of entry and exit for structures that supply blood to the kidney (renal artery), drain blood from the kidney (renal vein), and carry urine away from the kidney (ureter). It is also the site where nerves, lymphatic vessels, and smaller blood vessels enter and exit the kidney.
Lung:
In the lung, the hilus (or pulmonary hilum) is a depression on the mediastinal surface of each lung where structures such as the bronchi, pulmonary blood vessels, lymphatic vessels, and nerves enter and exit the lung. The pulmonary hilum is where the root of the lung is located, connecting the lung to the mediastinum of the thoracic cavity.
Spleen:
In the spleen, the hilus (or splenic hilum) refers to the area on the concave surface of the spleen where the splenic artery, splenic vein, and lymphatic vessels enter and exit the organ. It is also the site where nerves and lymphatic vessels enter and exit the spleen.
Function:
The hilus of an organ serves as a conduit for the structures that supply and drain the organ, as well as for nerves and lymphatic vessels. It facilitates the transport of blood, lymph, and other substances to and from the organ, allowing for proper function and communication with other parts of the body.
Renal Cortex
The renal cortex is the outer region of the kidney, lying directly beneath the kidney capsule, which is a tough fibrous layer surrounding the kidney. It’s one of the two major regions of the kidney, with the other being the renal medulla.
Renal pyramids
Renal pyramids are cone-shaped structures located within the renal medulla, the inner region of the kidney. They are named for their shape, which resembles a pyramid, with the base facing outward toward the renal cortex and the apex (papilla) pointing inward toward the renal pelvis. Here’s more detail about renal pyramids:
Renal Medulla
The renal medulla is the innermost region of the kidney, located deep to the renal cortex. It consists of structures known as renal pyramids, renal columns, and the renal pelvis.
Renal columns
Renal columns, also known as columns of Bertin, are extensions of the renal cortex that project into the renal medulla between the renal pyramids. These structures provide structural support to the kidney and contain blood vessels, tubules, and interstitial tissue.
Collecting Ducts
Collecting ducts are tubular structures in the kidney that play a crucial role in the final concentration of urine and the regulation of water and electrolyte balance in the body.
Calyx’s
Calyces are cup-like structures in the kidney that serve as the first point of collection for urine produced by the nephrons, located within the renal sinus, receiving urine from the papillary ducts, merging into major calyces, functioning as conduits for transporting urine to the renal pelvis, and facilitating efficient drainage of urine, with disorders affecting them potentially leading to urinary tract obstruction and kidney dysfunction.
Nephron
The nephron is the functional unit of the kidney, responsible for filtering blood and producing urine. It consists of a renal corpuscle (glomerulus and Bowman’s capsule) and a renal tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct), involved in processes such as filtration, reabsorption, secretion, and excretion, playing a crucial role in regulating electrolyte balance, fluid volume, and acid-base balance in the body, with millions present in each kidney, and disorders affecting nephron function potentially leading to kidney dysfunction and various renal disorders.
glomerulus
The glomerulus is a key component of the nephron, the functional unit of the kidney. It is a tiny tuft of capillaries located within the renal corpuscle, which is the initial part of the nephron responsible for filtering blood to produce urine. Here’s a concise overview of the glomerulus:
The glomerulus is a network of fenestrated capillaries that allows for the filtration of blood. It is surrounded by Bowman’s capsule, a cup-shaped structure that collects the filtrate.
Proximal Convoluted Tubule
The proximal convoluted tubule (PCT) is a segment of the renal tubule located in the renal cortex, immediately after the glomerulus and Bowman’s capsule, characterized by convoluted tubules with microvilli increasing surface area for reabsorption and secretion, responsible for reabsorbing approximately 65-70% of filtered water, electrolytes, glucose, amino acids, and other solutes, and secreting substances such as organic acids, bases, drugs, and waste products, contributing to pH regulation, with dysfunction implicated in renal disorders, drug interactions, and providing insights into kidney function through diagnostic tests.
Loop Of Henle
The loop of Henle, located in the renal medulla, is a U-shaped nephron segment consisting of descending and ascending limbs responsible for countercurrent exchange, creating an osmotic gradient crucial for urine concentration, with the descending limb permeable to water and impermeable to solutes, allowing passive water reabsorption, and the ascending limb actively transporting solutes out of the tubule, contributing to dilute tubular fluid formation, loop diuretics act on the thick ascending limb to inhibit sodium and chloride reabsorption, facilitating increased urine volume, crucial for maintaining body fluid balance, dysfunction implicated in renal disorders such as Bartter syndrome, loop diuretic resistance, and diagnostic tests aiding in the assessment of kidney health.
⦿ Descends from the PCT into the medulla, turns, then goes back to the renal cortex.
⦿ Descending loop has epithelial cells similar to those of the PCT
⦿ At the bottom of the loop, the epithelial cells flatten to simple squamous epithelial cells and lose their brush border since at that stage it is no longer a necessary thing.
⦿ The ascending loop wall becomes thicker again.
Distal Convoluted Tubule
The distal convoluted tubule (DCT) in the kidney, located between the loop of Henle and the collecting duct, regulates electrolyte balance, pH, and water reabsorption, characterized by convoluted tubules with active reabsorption and secretion of ions, hormonally regulated by aldosterone and parathyroid hormone (PTH), involved in acid-base balance by secreting hydrogen ions and reabsorbing bicarbonate ions, fine-tuning urine composition before entering the collecting duct, dysfunction implicated in renal disorders like Bartter syndrome and Gitelman syndrome, affected by drug interactions, and assessed through diagnostic tests measuring electrolyte levels and acid-base status.
⦿ Continuation of the ascending loop of henle
⦿ The DCT’s from all nephrons in the kidney empty into the collecting ducts
⦿ The Collecting ducts carry tubular filtrate (produced by the glumerulus) through the medulla. They empty into the renal pelvis and it is the primary site of action of ADH (Anti-diuretic hormone) and regulation of potassium and acid-base balance.
Blood Supply
⦿ The renal artery enters the kidney at the hilus. then it divides into smaller arteries and arterioles.
⦿ Afferent glomerulus arteries carry blood into the glumerulus. glomerulus capillaries filter some of the plasma from the blood.
Ureters
The ureters are muscular tubes that transport urine from the kidneys to the urinary bladder via peristaltic contractions, featuring three layers including mucosa, muscular, and fibrous layers, with a ureterovesical junction preventing backflow, and can be affected by conditions such as obstruction or injury, diagnosed through imaging studies, and treated with surgical interventions.
⦿ Leave the kidney at the hilus. Outer fibrous layer, middle visceral smooth muscle layer, and inner layer lined with transitional epithelium.
⦿ When the bladder is full, it collapses the opening of the ureter, preventing urine from backing up into the ureter.
⦿ Wall of the urinary bladder contains smooth muscle bundles.
⦿ Neck of the bladder extends caudally from the sac into the pelvic canal and joins the urethra.
Renal Physiology
Renal physiology encompasses the study of the structure and function of the kidneys, including processes such as filtration, reabsorption, secretion, and excretion, which are essential for maintaining homeostasis in the body. Key aspects of renal physiology include glomerular filtration, tubular reabsorption and secretion, regulation of electrolyte balance, acid-base balance, blood pressure regulation, and hormone production. Understanding renal physiology is crucial for comprehending the mechanisms involved in urine formation, fluid and electrolyte regulation, and the excretion of metabolic waste products, as well as for diagnosing and managing kidney-related disorders and diseases.
Waste products found in urine:
⦿ Carbon dioxide and water from carbohydrate and fat metabolism.
⦿ Nitrogenous waste, primarily urea, from protein metabolism.
⦿ Bile salts and pigments from red blood cell breakdown.
⦿ Various salts from tissue breakdown and excessive consumption.
The body has several routes by which wate products are eliminated:
The respiratory system- carbon dioxide and water vapor.
The sweat glands- water, salts, and a small amount of urea.
The digestive system- bile salts and bile pigments.
The urinary system- urea, salts, water, and other soluble waste products. The urinary is the single most important route of waste-product removal in the body
⦿ The kidney is located in the dorsal abdominal area ventral to and on either side of the first few lumbar vertebrae
⦿ Retroperitoneal to abdominal cavity; between peritoneum and dorsal abdominal muscles
⦿ Most domestic animals, the right kidney is more cranial than the left.
⦿ Thick layer of parirenal fat usually surrounds the kidneys to help protect them from pressure exerted by surrounding organs.
Retroperitoneal- doesn’t sit within the abdominal cavity, it sits between the peritoneum and the dorsal abdominal muscles.
Kidney Functions
⦿ Blood filtration, reabsorption, secretion, recycle and toss.
⦿ Fluid balance regulation - diuresis, oliguria, anuria, antidiuretic hormone (ADH) and aldosterone.
⦿ Acid-balance regulation - removal of acidic hydrogen and basic bicarbonate ions.
⦿ Hormone production - friends with the endocrine system.
⦿ Blood pressure regulation - blood pressure sensors and release of renin.
⦿ If the body has excess water and needs to get rid of it more urine is formed, that’s called diuresis
⦿ If the body needs to conserve water then less urine will be produces, that’s called oliguria
⦿ If the body is conserving all of the water and no urine is being produced, that’s called antidiuretic
⦿ Anuria is a medical term that refers to a condition characterized by an extremely low urine output, It indicates a significant reduction or absence of urine production by the kidneys.
Nephrons number variations in species
⦿ Every specie has a different number of nephrons.
-Medium sized cats- 200.000T
-medium sized dogs- 700.000T
-sheep, pigs, humans- 1.000.000m
-cattle- 4.000.000m
Renal corpuscle
-Located in the renal cortex its function is to filter the blood in the first stage of urine production, composed of the glumerulus which is surrounded by the bowman’s capsule and the proximal convoluted tubule (PCT). It’s lined with cuboidal epithelial cells that have a brush border which assists with surface area. All of this makes a twisting path throughout the renal cortex.
Filtation of blood
⦿ Filtration of blood happens in the corpuscle
⦿ Glomerular capillaries are unique, they are under high pressure (30% aorta) and they are between two arterioles.
⦿ Glomerular capillaries contain many large fenestrations in capillary endothelium
⦿ Fenestrations not large enough to allow blood cells or large proteins to pass through - glomerular filtrate.
⦿ High blood pressure in the glomerular capillaries forces some plasma out of the capillaries and into the capsular space of the bowman’s capsule
⦿ Glomerular filtration rate (GFT): how fast plasma is filtered through the glomerulus.
Proteinuria
Proteinuria, abnormal protein excretion in urine, indicative of kidney dysfunction, caused by various factors including kidney diseases, systemic conditions, infections, medications, or physical stress, diagnosed through urine analysis and quantification, warrants further evaluation for underlying causes and kidney function assessment, serves as a prognostic marker for disease progression and cardiovascular complications, managed by treating underlying conditions and reducing protein excretion to preserve kidney function and prevent complications.
Reabsorption
Reabsorption is the process of transporting filtered substances from the renal tubules back into the bloodstream, involving active or passive transport mechanisms, key substances reabsorbed include water, electrolytes, glucose, and amino acids, dysfunction implicated in renal disorders and drug interactions, diagnosed through urine analysis, essential for maintaining fluid and electrolyte balance, and regulated by hormones such as antidiuretic hormone (ADH) and aldosterone.
⦿ Both good things and bad things sneak out of the capillaries.
⦿ Substances to be reabsorbed pass out of the tubular lumen through or between tubular epithelial cells
⦿ Substances to be reabsorbed then enter interstitial fluid and pass through endothelium into peritubular capillaries.
⦿ The substances make their way through the proximal convoluted tubule (PCT and this is where reabsorption really begins (tubular filtrate)
⦿ Sodium reabsorption: The goal there is to pump sodium out of the filtrate back into the blood
⦿ Sodium starts off by floating in the nothingness of the PCT internal space.
⦿ Then it has to make its way back into the (body proper) so it laches onto a carrier protein to get actively placed into the PCT epithelial cells.
⦿ Then, it has to be actively pumped out of the cell into the interstitial space, space between cells, where it can be picked up by the bloodstream through the peritubular capillaries.
⦿ Sodium ions are also reabsorbed in the ascending loop of henle and the DCT.
-Usually exchanged for hydrogen, ammonium, or potassium ions.
⦿ Magnesium is reabsorbed from the PCT, ascending loop of henle, and the collecting duct
-Parathyroid hormone release increases the reabsorption of magnesium.
⦿ Potassium and calcium reabsorption takes place in the PCT, ascending loop of henle and DCT.
-Calcium moves from the filtrate under the influence of vitamin D, parathyroid hormone (PTH), and calcitonin.
⦿ Chloride (Cl-) diffuses from the tubular filtrate into the epithelial cells and interstitial space in response to electrical imbalance created by (Na+) removal.
⦿ Some of the water in the filtrate moves into the interstitial space and peritubular capillaries by osmosis once sodium, glucose, amino acids, and chloride have left the tubular filtrate.
Secretion
Secretion is the process of actively moving substances from the blood into the renal tubules for excretion in urine, involving active transport mechanisms, key substances secreted include hydrogen ions, potassium ions, creatinine, and drugs or toxins, dysfunction implicated in renal disorders and drug interactions, essential for maintaining acid-base balance and eliminating waste products, regulated by hormones and neural signals.