Urinary System Study Notes PDF

The Urinary System ​ Part of the excretory system Colon -​Part of the excretory system -​Three parts of the colon; -​The ascending colon; absorbs water, salts, and some nutrients from partially digested food to form solid stool. It pushes waste upward to the transverse colon,...

The Urinary System ​ Part of the excretory system Colon -​Part of the excretory system -​Three parts of the colon; -​The ascending colon; absorbs water, salts, and some nutrients from partially digested food to form solid stool. It pushes waste upward to the transverse colon, while bacteria help break down undigested food, producing gases and fatty acids. -​The transverse colon is the part of the large intestine that moves waste across the abdomen from right to left. It continues absorbing water and salts from the waste to help form solid stool. -​The descending colon moves the waste downward on the left side of your abdomen. It stores the remaining solid waste, and bacteria further break down any leftover nutrients before the waste moves to the rectum for excretion. Urethra -​The urethra is a tube that carries urine from the bladder out of the body. It is the final part of the urinary system. In males, the urethra is longer and also carries semen during ejaculation. In females, the urethra is shorter and only carries urine. -​The urethra is located between the bladder and the external opening of the body, called the urethral meatus. It plays a key role in removing waste (urine) from the body. -​In Females -​Short, straight -​Opens on floor of vestibule of vulva -​Transitional epithelium -​In males -​Longer, curved -​Runs along ventral aspect of penis -​Shared with reproduction system (carries urine and semen) -​Transitional epithelium (ish) Bladder -​The bladder is a hollow, muscular organ that stores urine produced by the kidneys before it is excreted from the body. Its main function is to hold urine until it is full and the body is ready to eliminate it. -​The bladder is located in the lower abdomen, behind the pubic bone. It can expand as it fills with urine, and when it's time to go to the bathroom, the muscles of the bladder contract to push the urine out through the urethra. The bladder’s ability to store and release urine helps the body manage waste efficiently. Uterus -​The uterus is a hollow, muscular organ in females that is primarily responsible for housing and nurturing a developing baby during pregnancy. Its main function is to provide a safe environment for a fertilized egg to implant and grow into a fetus. -​The uterus is located in the pelvic region, between the bladder and the rectum. It has a thick lining that changes throughout the menstrual cycle. If pregnancy does not occur, the lining is shed during menstruation. The uterus also plays a role in labor, contracting to help push the baby out during childbirth. -​Endometrium (Inner layer): -​Location: This is the innermost layer of the uterus. -​Function: The endometrium is responsible for nourishing a fertilized egg. Each month, it thickens to prepare for pregnancy. If no pregnancy occurs, it sheds, causing menstruation. -​Myometrium (Middle layer): -​Location: The myometrium is the thick, muscular layer that surrounds the endometrium. -​Function: It plays a crucial role in contractions during labor and delivery. The myometrium helps push the baby out during childbirth and also contracts during menstruation.  -​Perimetrium (Outer layer): -​Location: This is the outermost layer of the uterus, a thin membrane that covers the uterus. -​Function: The perimetrium helps protect the uterus and provides support, holding it in place within the pelvic cavity. Ureters -​The ureters are two narrow tubes that carry urine from the kidneys to the bladder. Their main function is to transport the urine produced by the kidneys so it can be stored in the bladder until it’s ready to be excreted. -​Each ureter is about 10-12 inches long and runs from the kidneys down to the bladder, one on each side of the body. The ureters use rhythmic muscle contractions called peristalsis to move urine along, and they have special valves to prevent urine from flowing backward. This ensures that urine moves in the right direction, from the kidneys to the bladder.  -​2 tubes which exit the kidneys at the hilus’s, they then connect to the urinary bladder at the caudal end Kidneys -​The kidneys are two bean-shaped organs that play a crucial role in filtering and removing waste products and excess fluids from the blood. Their main function is to produce urine, which contains waste like urea, excess salts, and water, and then send it to the bladder for excretion. -​The kidneys are located on either side of the spine, just below the rib cage, in the lower back. They also help regulate blood pressure, maintain the balance of electrolytes (like sodium and potassium), and produce hormones that control red blood cell production. The kidneys are essential for keeping the body’s internal environment balanced and healthy. Urinary meatus -​The urinary meatus is the external opening of the urethra, the tube that carries urine from the bladder out of  the body. Its main function is to serve as the passage through which urine is expelled from the body. -​In males, the urinary meatus is located at the tip of the penis, and in females, it is located just above the vagina, between the clitoris and the vaginal opening. The urinary meatus plays a crucial role in the elimination of urine and is the final point in the urinary system before urine exits the body. Kidneys retroperitoneal -​The kidneys are described as retroperitoneal, which means they are located behind the peritoneum. The peritoneum is a membrane that lines the abdominal cavity and covers many abdominal organs. Since the kidneys are behind this membrane, they are not inside the abdominal cavity but rather in the lower back, just outside the peritoneal lining. Image: -​Right kidney more cranial (except pigs and grasscutters) -​Visceral Peritoneum: -​This layer directly covers the abdominal organs, such as the intestines and liver, providing them with protection and lubrication. -​It allows friction-free movement of organs during digestion and other abdominal activities. -​Parietal Peritoneum: -​This layer lines the inner surface of the abdominal wall. -​It anchors and separates the abdominal cavity from surrounding  structures while maintaining structural integrity. Basic function of the renal system - Homeostasis! -​Fluid Balance: The kidneys control water levels by filtering excess water from the blood or retaining it, ensuring optimal blood volume and pressure. -​pH Balance: By excreting hydrogen ions (H⁺) and reabsorbing bicarbonate (HCO₃⁻), the kidneys maintain blood pH within a narrow range (around 7.35–7.45), crucial for cellular function. -​Electrolyte Balance: Key electrolytes like sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), and chloride (Cl⁻) are regulated by the kidneys to support nerve function, muscle contraction, and hydration. -​Nitrogenous Waste Removal: The kidneys eliminate metabolic byproducts like  urea, creatinine, and uric acid, preventing toxic accumulation. -​Filters blood -​Reabsorbs good stuff from filtrate -​Secretes more of other stuff into filtrate that it needs to get rid of -​Decides how much water to send with filtrate -​Filtrate urine voided -​Erythropoietin (EPO): The kidneys produce this hormone when oxygen levels in the blood are low. It tells the bone marrow to make more red blood cells, which carry oxygen to the rest of the body. -​Prostaglandins (PGs): These are made by the kidneys to help control blood flow in the kidneys, reduce inflammation, and keep blood pressure stable. -​Renin: The kidneys release this enzyme when blood pressure is low or when the body needs to hold on to more water and salt. Renin starts a process  (called RAAS) that increases blood pressure by helping the body retain water and sodium. -​ADH and Aldosterone: The kidneys respond to these hormones. ADH helps the kidneys save water, while aldosterone helps save sodium and get rid of extra potassium. Both work with the kidneys to regulate blood pressure and fluid balance. Renal cortex: -​Outer portion of the kidney -​Involved in blood filtration (removes waste substances) -​Reddish brown colour with rough & granular appearance Renal medulla: -​Inner portion that surrounds renal pelvis -​Darker reddish brown colour, smooth appearance Notes about image Similarities: Cortex and Medulla: Both kidneys have an outer renal cortex and an inner renal medulla, responsible for filtering blood and concentrating urine. Renal Pyramids: Found in the medulla of both kidneys, these structures aid in urine production and transport. Renal Columns: Extensions of the cortex that separate the pyramids in both kidneys. Renal Sinus: A cavity containing fat, blood vessels, and the renal pelvis in both kidneys. Differences: Shape: -​The porcine kidney is more lobulated and larger, showing distinct pyramids with clear renal papillae (the tips of pyramids). -​The feline kidney appears smoother and less lobulated, with renal pyramids converging at a single renal crest rather than individual papillae. Pelvis and Ureter: -​In pigs, urine flows through multiple minor calyces before reaching the renal pelvis. -​In cats, the renal pyramids drain directly into a single renal pelvis. Fat in the Renal Sinus: -​The porcine kidney shows a more distinct fat layer in the renal sinus compared to the feline kidney. In summary, while both kidneys share the same basic structure and function, the pig kidney is more lobulated with multiple drainage points, while the cat kidney is smoother and more streamlined for urine flow. The nephron: -​Functional unit of the kidney = the nephron -​Filtration: Blood enters the kidney through the renal artery, which branches into smaller vessels until it reaches the tiny capillaries in the glomeruli. Here, waste, water, and small molecules are filtered out of the blood to form urine. -​Reabsorption and Secretion: After filtration, the blood travels through capillaries around the nephron (the kidney's functional unit). These capillaries allow the kidneys to reabsorb useful substances like water, glucose, and electrolytes back into  the blood while secreting waste products into the urine. -​Oxygen and Nutrient Supply: Blood vessels deliver oxygen and nutrients to the kidney tissues to keep them functioning efficiently. -​Blood Pressure Regulation: Specialized blood vessels in the kidney sense blood pressure and release renin to help control it, ensuring the kidneys receive enough blood to function. -​In summary: Without the network of blood vessels, the kidneys couldn’t filter waste, balance fluids, or regulate blood pressure. Notes about image Key Components: -​Renal Artery: Brings blood from the heart to the kidney for filtration. Afferent Arteriole: A small blood vessel that carries blood into the glomerulus. -​Glomerulus: A cluster of tiny capillaries where blood is filtered. Waste products, water, and small molecules pass through its walls to  form the initial urine, while larger components like blood cells and proteins stay in the blood. -​Efferent Arteriole: Carries filtered blood away from the glomerulus. -​Peritubular Capillaries: Surround the nephron tubules. These vessels allow for the exchange of water, nutrients, and waste between the blood and the tubules. Useful substances are reabsorbed into the blood, and additional waste products are secreted into the tubules. Notes about image Key Parts: Renal Artery and Vein: -​The renal artery (red) brings oxygenated, unfiltered blood into the kidney.  -​The renal vein (blue) carries filtered blood out of the kidney. Branching Arteries: -​The renal artery branches into segmental arteries, which further divide into interlobar arteries (between kidney lobes) and arcuate arteries (arching over the base of the pyramids). -​Cortical radiate arteries (small branches) supply blood to the glomeruli, where filtration begins. Afferent and Efferent Arterioles: -​Afferent arterioles bring blood to the glomerulus (a tiny capillary cluster for filtration). -​Efferent arterioles carry filtered blood away and lead to the peritubular capillaries, which surround nephron tubules for further exchange. Returning Veins:  -​Blood travels back through cortical radiate veins, arcuate veins, and interlobar veins, finally exiting through the renal vein. Notes for filtration -​Renal corpuscle = glomerulus + Bowman’s capsule -​Glomerulus = ‘nest’ of blood vessels btwn 2 arterioles ( high BP) -​diameter of the afferent arteriole (Aff art.) is greater than the diameter of the efferent arteriole (Eff art.) Definition of Fenestrations -​tiny holes or pores in the walls of the glomerular capillaries (the small blood vessels in the kidney's glomerulus). -​Glomerular capillaries have lots of fenestrations -​Big fenestrations in caps of glomerulus -​Blood cells and plasma proteins too big to get through Podocytes definition -​specialized cells that form the inner layer of the Bowman’s capsule. They are a key part of the filtration barrier in the kidney. -​Podocytes – make up inner layer of Bowman’s capsule -​GFR – mL/min (Glomerular Filtration Rate) -​10 kg dog – 250 mL blood through kidneys each minute -​Only about 1-2 liters of urine are excreted daily after reabsorption, but 60 liters of filtrate are initially processed in a single day. -​Glomerular damage  -​Drugs: Certain medications can harm glomeruli over time. -​Diabetes: High blood sugar damages the filtration barrier. -​Lupus: Autoimmune attacks can inflame and injure glomeruli. -​Infections: Severe infections may cause inflammation and scarring. -​Toxins: Harmful substances can directly damage kidney cells. -​Idiopathic causes: When the exact cause is unknown. Reabsorption notes This diagram shows how substances are reabsorbed from the glomerular filtrate in the proximal convoluted tubule back into the bloodstream. -​Substances Reabsorbed: -​Ions (Na+, K+, Ca2+, Mg2+, Cl-, H+): These are reabsorbed through active transport (requires energy)  and diffusion (moves from high to low concentration). -​Glucose and Amino Acids: These are reabsorbed alongside sodium using special transport proteins. -​Water: Follows the movement of ions by osmosis (water flows to areas with more dissolved particles). -​Bicarbonate (HCO₃⁻): Helps maintain pH balance and is reabsorbed into the blood. -​Layers the Substances Cross: -​To move back into the bloodstream, substances must pass through: -​Tubule Cell (Proximal Convoluted Tubule): The first barrier that actively or passively transports substances. -​Interstitial Space: The area between the tubule cells and blood vessels. -​Capillary Wall (Bloodstream): The final layer substances cross to return to the blood. -​Transport Mechanisms:  -​Active Transport: Requires energy (ATP) to pump substances like sodium across membranes. -​Osmosis and Diffusion: Moves water and solutes passively to maintain balance. Notes about image -​Reabsorption; PCT (proximal convoluted tubule) – 65%, most of Na, Cl, H2O, all glucose and a.a. -​Sodium actively pumped out via transport protein -​Glucose and amino acids hitch a ride – passive transport (aka sodium cotransport)  -​Potassium diffuses out -​Loop of Henle -​Desc permeable to water -​Ascend. impermeable to water, sodium pumped out -​Creates salty (hyperosmotic) medulla -​DCT (distal convoluted tubule) -​Sodium leaves in exchange for H+, NH4+, K+ -​Aldosterone controls this -​Collecting Duct -​Water reabsorbed under the influence of ADH Secretion Notes -​If substances are not filtered out by the glomerulus but still need to leave the body, the kidney has a backup process called secretion. Here's what happens: -​Active secretion:  -​The substances are moved directly from the blood in the peritubular capillaries into the nephron's tubules (mainly the distal convoluted tubule (DCT) and the collecting ducts). -​This process requires energy because it goes against the natural concentration gradients. -​Substances removed through secretion: -​H+ ions: To help balance the body's pH. -​K+ ions: To regulate potassium levels in the blood. -​Ammonia (NH3) and urea: Toxic waste products from metabolism. -​Drugs and toxins: Medications like penicillins and other unwanted chemicals are secreted into the urine. -​Purpose of secretion: -​Ensures that harmful substances or excess ions that were not removed by filtration are eliminated from the body. -​H+ (hydrogen ions): To help regulate blood pH. -​K+ (potassium ions): To maintain the right balance of potassium in the blood. -​NH3 (ammonia): A waste product of protein metabolism. -​Urea: A waste product from the breakdown of proteins. -​Medications like penicillins and sulfonamide antibiotics (used to treat infections) can also be actively secreted into the urine in the DCT to ensure they leave the body. -​Choices for treating urinary tract infections (UTIs) include antibiotics like sulfonamides. These drugs are secreted into the urine in high concentrations, which makes them effective at killing bacteria in the urinary system. Reabsorption and Secretion image Water regulation (which also affects blood pressure) -​Anti-diuretic hormone (ADH) – opens water pores in the collecting ducts (ADH made in hypothalamus, stored in posterior pituitary) -​Aldosterone – increases sodium reabsorption in DCT and collecting duct – sodium moves out of tubules water follows (if ADH present) – aldosterone is made by adrenal gland Notes about image Blood Pressure homeostasis -​Juxtaglomerular cells – mostly on afferent arteriole (green) -​monitor BP, secrete renin if needed (i.e. if BP falls) -​Macula densa (orange) – specialized cells in ascending thick L of H where meets DCT  -​monitor sodium concentration of filtrate -​senses decreased Na+ flowing by (indicates decreased GFR (less fluid is being filtered from the blood into the nephron), and decreased BP) -​MD cells -​In response to low sodium, MD cells release chemical messengers called prostaglandins. These prostaglandins help by widening (vasodilating) the afferent arteriole (the blood vessel entering the glomerulus). This increases blood flow to the kidney and improves filtration. -​Telling JG cells to release renin: -​The MD cells also signal the juxtaglomerular (JG) cells, which are located nearby, to release renin. Renin is an enzyme that starts a process to raise blood pressure and retain sodium and water in the body. JG cells monitor BP – if detect low BP OR MD detects less Na JG cells release RENIN Renin converts angiotensinogen angiotensin I angiotensin I angiotensin II via ACE (angiotensin converting enzyme) Arteries constrict and aldosterone and ADH released to increase H20 reabsorption Blood pressure increases Notes about image -​The ureters are tubes that carry urine from the kidneys to the bladder. They have several important layers, each playing a specific role: -​Fibrous layer: This outermost layer provides structure and protection to the ureter. -​Smooth muscle: The middle layer of smooth muscle contracts in waves  (called peristalsis) to push urine down toward the bladder. -​Transitional epithelium: The innermost lining of the ureter is made of this special type of tissue. It stretches to allow the ureter to expand when urine flows through and prevents urine from leaking into surrounding tissues. -​The lumen is the hollow space in the middle of the ureter where the urine travels. -​Peristalsis – continuous -​Enter ur. bladder obliquely so no back flow Notes about image -​Ectopic ureters occur when one or both ureters (the tubes that carry urine from the kidneys to the bladder) do not connect to the bladder in the normal position. Instead, they open abnormally into other parts of the urinary or reproductive system, such as the urethra, vagina, or even outside the body. Key Points:  -​Normal ureter openings lead to the bladder, allowing urine to flow properly. -​Ectopic ureter openings (as shown in the diagrams) bypass the bladder, causing issues like urine leakage or incontinence. -​This condition is often congenital (present at birth). -​The X-ray and images help locate the abnormal ureter openings. The arrows highlight the kidneys, ureters, and bladder, showing the unusual pathways of the ureters. Symptoms and Effects: -​Involuntary urine leakage. -​Increased risk of infections. -​Treatment usually involves surgery to reposition the ureter to its correct location in the bladder. Notes about urinary bladder images – Stores urine -​Muscular Sac: -​The bladder is a muscular sac that stores urine. -​Its walls are made of smooth muscle that can stretch to hold urine and contract to push urine out during urination. -​Neck: -​The neck of the bladder is the narrow, funnel-like region at its base that connects to the urethra  (the tube that carries urine out of the body). -​It contains a sphincter muscle that controls the release of urine, helping prevent leakage until it's time to urinate. -​Trigone – arrangement of openings of ureters into bladder and opening from bladder into urethra The epithelial lining of the urinary bladder has a special purpose: -​Stretch and Protect: -​The lining is made of transitional epithelium, a type of tissue that can stretch and change shape. -​This allows the bladder to expand as it fills with urine and contract when it's empty. -​Barrier Against Urine: -​The lining acts as a protective barrier, preventing harmful substances in the urine (like waste and toxins) from damaging the bladder's tissues. -​The three layers of the urinary bladder: -​Mucosa (Inner Layer): -​Made up of transitional epithelium and connective tissue. -​It allows the bladder to stretch and protects it from urine. -​Muscular Layer (Detrusor Muscle): -​Made of smooth muscle. -​This layer contracts to push urine out during urination. -​Adventitia or Serosa (Outer Layer): -​Adventitia is connective tissue that attaches the bladder to surrounding structures. -​Serosa is a thin layer of tissue on the top of the bladder in some areas, providing additional protection. -​Detrusor muscle -​The detrusor muscle is the smooth muscle layer of the urinary  bladder. Its purpose is to contract and push urine out of the bladder during urination. It also relaxes to allow the bladder to fill and store urine. This muscle plays a key role in controlling the bladder’s ability to hold and release urine when needed. -​Empty bladder is round and sits in pelvic canal -​As bladder fills, it becomes pear shaped and extends cranially into abdominal cavity Micturition aka urination 1.​ Urine collects in the bladder, and it stretches as it fills. 2.​ Stretch receptors in the bladder wall send signals to the spinal cord. 3.​ The spinal cord sends a message back to the bladder, telling the detrusor muscle (bladder muscle) to contract slightly. 4.​ This creates the feeling of needing to pee (“gotta go”). 5.​ The internal sphincter (a smooth muscle valve) relaxes automatically. 6.​ The external sphincter (a skeletal muscle valve you can control) stays closed until you decide to pee. 7.​ The brain can delay urination by keeping the external sphincter closed and stopping the detrusor muscle from fully contracting. 8.​ If the bladder gets too full, the external sphincter will eventually relax, and urination will happen. 9.​ When you’re ready, both sphincters open, and the detrusor muscle contracts to empty the bladder. -​Kidney disease -​Acute vs. chronic -​Acute: -​Sudden loss of kidney function. -​Caused by dehydration, infections, toxins, or blockages. -​Can be reversible with quick treatment.  -​Symptoms: Decreased urine output, swelling, and fatigue. -​Chronic: -​Gradual and progressive loss of kidney function over time. -​Often caused by diabetes, high blood pressure, or long-term damage. -​Irreversible but manageable to slow progression. -​Symptoms: Poor appetite, nausea, high blood pressure, and anemia. -​Cystoscopy definition: a medical procedure used to examine the inside of the bladder and urethra. Canine, Feline and Ovine- Traditional bean shaped unipyramidal Sub-capsular veins in cats x2-3 L2 length  Bovine Lobulated – multipyramidal/multilobar No pelvis – papillae drain into branches of ureter Both kidneys on the right Equine R-heart shaped; left bean shaped unipyramidal Pelvic cells produce mucin- cloudy appearance Porcine Huge pelvis, flat unipyramidal Renal cortex Hints to identification: -​The cortex has a rich supply of capillaries associated with the glomeruli, which contributes to the filtration process. -​The round, dense structures scattered throughout the image are glomeruli. These are unique to the renal cortex and are absent in the renal medulla. Renal medulla Hints to identification: -​Straight Tubules: These include parts of the loop of Henle and collecting ducts, which appear as parallel lines or clusters of circular profiles in cross-section. -​Vasa Recta: The blood vessels in the medulla that run parallel to the loops of Henle, appearing elongated or circular depending on the section. -​Lack of Glomeruli: Unlike the renal cortex, the medulla lacks glomeruli, which is a defining feature. Glomerulus Hints to identification: -​Tuft of Capillaries: The dense cluster of capillaries within the glomerulus is visible as a network of small blood vessels. These capillaries are crucial for the filtration process. -​Bowman's Space: The white space surrounding the glomerular capillaries represents Bowman's space, where the filtered fluid (glomerular filtrate) collects before entering the proximal tubule. -​Podocyte Nuclei: The nuclei of podocytes, the specialized cells that wrap around the capillaries, can be seen as larger, darker, and more irregularly shaped structures. Bowman's capsule -​Bowman's Space: The space between the inner visceral layer (closely attached to the glomerular capillaries) and the outer parietal layer is visible as a clear, open area in the image. This is the Bowman's space, where the filtrate from blood enters. -​Distinct Layer of Cells: The outer parietal layer of Bowman's capsule is composed of simple squamous epithelium, which is visible as a thin, continuous line outlining the capsule. Proximal & distal convoluted tubules PCT -​Brush Border: The PCT has a prominent brush border (microvilli) that appears as a fuzzy, irregular lumen. This helps in reabsorbing water, ions, and nutrients. -​Cytoplasm Appearance: The cells of the PCT are larger, with more granular cytoplasm due to the presence of abundant mitochondria required for active transport. -​Smaller Lumen: The lumen of the PCT is often smaller and irregular in shape due to the prominent microvilli. -​Darker Staining: The cytoplasm stains darker compared to the DCT.  -​Tubules on the outer areas of the image DCT -​No Brush Border: The DCT lacks a brush border, resulting in a smooth and more open appearance of the lumen. -​Larger and Clearer Lumen: The lumen of the DCT is larger and more regular in shape compared to the PCT. -​Lighter Staining: The cells in the DCT have less cytoplasm, and they stain lighter compared to the PCT. -​Smaller Cells: The cells of the DCT are generally smaller and less granular than those in the PCT. -​Tubules on the middle inner area of the image Loop of Henle -​Tubular Structures with Thin Walls -​The structures in the image are tubular with thin, flattened epithelial linings, characteristic of the thin limbs of the Loop of Henle. -​Some tubules show thicker epithelium, which may represent the thick ascending limb. -​Narrow Lumen -​The lumens of these tubules are narrow and surrounded by a minimal  cytoplasmic border, typical of the thin portions of the Loop of Henle. -​The clear and uniform lumens are distinct compared to the proximal tubules with a brush border. -​Location in the Medulla -​The Loop of Henle is typically located in the medullary region of the kidney, and this image reflects the medullary architecture with closely packed tubules. Collecting ducts ​ 1. Large, Regularly Shaped Lumens The tubules in the image have large, clearly defined, and regular lumens compared to proximal or distal tubules. The lumens are generally open and unobstructed, a hallmark of collecting ducts. 2. Cuboidal to Columnar Epithelium The epithelial cells lining the collecting ducts appear cuboidal or low columnar, with nuclei located near the center of the cells. This is distinct from the squamous cells of the thin Loop of Henle or the taller cuboidal cells of proximal tubules. 3. Distinct Cell Boundaries Cell boundaries are clearly visible, giving the appearance of "tiles" around the lumen. This characteristic helps distinguish collecting ducts from other tubular structures. 4. Uniform Nuclei The nuclei are round and evenly spaced within the epithelial lining, contributing to a regular appearance of the duct. Macula densa 1. Dense Arrangement of Cells The macula densa consists of closely packed epithelial cells, which can be seen as a region with a higher density of nuclei compared to the surrounding tubular cells. 2. Location The macula densa is part of the distal convoluted tubule, positioned adjacent to the glomerulus, which is identifiable in the background of this image. 3. Tall, Columnar Cells Unlike the typical cuboidal epithelial cells of the distal convoluted tubule, the macula densa cells are taller and more columnar in shape, making them distinct in histological sections. 4. Nuclei Placement The nuclei in the macula densa cells are densely packed and appear closer together, a hallmark feature when compared to the more spaced-out nuclei in neighboring cells. 5. Functional Association Its proximity to the glomerulus and its distinct cellular arrangement are consistent with the role of the macula densa in sensing sodium chloride concentration as part of the juxtaglomerular apparatus. Ureter 1. Star-Shaped Lumen The lumen of the ureter often has a distinctive star-shaped appearance due to the folded mucosa, as seen in this image. This folding allows for expansion when urine passes through. 2. Transitional Epithelium The epithelial lining of the lumen is composed of transitional epithelium (urothelium), which is characteristic of the urinary tract, including the ureter, bladder, and renal pelvis. This epithelium appears as several layers of cells that can stretch and accommodate the flow of urine. 3. Thick Muscularis Layer Surrounding the mucosa, there is a prominent muscularis layer. The ureter has two layers of smooth muscle (an inner longitudinal layer and an outer circular layer) that aid in peristalsis to propel urine toward the bladder. 4. Adventitia The outermost layer, the adventitia, consists of connective tissue that anchors the ureter to surrounding structures. This layer is visible as a dense, fibrous region on the periphery of the section. 5. Lack of Glandular Structures Unlike some other tubular structures in the body, the ureter does not have mucosal glands, which helps distinguish it from other organs. Transitional Epithelium of ureter Urinary bladder 1. Transitional Epithelium (Urothelium): The inner lining is composed of transitional epithelium, characteristic of the urinary bladder and other parts of the urinary tract. This epithelium allows for stretching and recoiling to accommodate varying volumes of urine. 2. Thick Muscular Layers (Detrusor Muscle): The bladder is surrounded by several layers of smooth muscle collectively referred to as the detrusor muscle. These layers are visible in this image and are organized in irregular bundles running in various directions (longitudinal, circular, and oblique). This muscle is critical for contraction during urination. 3. Mucosal Folds (Rugae): The surface exhibits folds or undulations, which are indicative of the rugae. These folds allow the bladder to expand significantly as it fills with urine. 4. Dense Connective Tissue in the Lamina Propria: Beneath the epithelium, the lamina propria is composed of dense connective tissue that supports the mucosa. 5. Absence of Glandular Structures: The urinary bladder lacks significant glandular structures within the wall, differentiating it from other organs like the stomach or intestines. 6. Location Context: The combination of transitional epithelium, muscularis propria (detrusor muscle), and rugae are highly specific to the urinary bladder. Transitional epithelium of urinary bladder Functioning units filtering the blood and producing the urine Hilaus - artery goes in (all vessels come into) Renal crest where urine goes before entering the ureter Adrenal glands video; Medula is dark and on the inside Cortex is outer layer, lighter colour Unipyramidal (empty into one renal pelvis), multipyramidal Vascular system and tubules (nephron associated with both) Pyramids only included in loop of henle and collecting duct Kidney characteristics same for animals: All have capsule of fibrous material, cortex and medulla Highlum and ureter Kidney characteristics different for animals: What happens at end of pyramid and ureters Pig and Ox have multipyramidal kidneys Cat, dog and horse are unipyramidal; Each pyramid opens up into its own collecting section Minor Calyx in Ox Each structure in pig and ox is a lobe Collecting sections collect fluid coming out of collective duct Equine kidneys: Left kidney is further back Right kidney has a heart shape Bovine Kidney: Minacalyx join up to create a major calyx Do not have renal pelvis When you see glomerulus you know you are in the cortex Microvilli = increases surface area Macula densa- detect sodium levels and detect triggers in sodium levels in order to modify blood pressure. Group of dense cells. Typically more concentrated on one side of the tube. One side is closer to glomerulus. In the collecting duct right before it gets excreted. Transitional epithelium - has elasticity, aids in ureter allowing it to expand Arterioles are circles on the ends of the kidneys overall structure All of those circles in the nephron of the kidney are the cortex Visceral layer has podocytes (nephron image, bowman's capsule) Parietal layer - squamous epithelium Structures where they are relative to each other (Histo - penis, testes, uterus) Uterus - know the three layers Round ligament (cord-like) holding uterus in place (look like wider red globs) Ligament that folds over and is attached to many places of the uterus - broad ligament Suspensory ligament - attaches ovary to body wall (During dissection or surgery must stretch and break down suspensory ligament to reposition ovary) Properly ligament between ovary and ovarian horn During spay removal of ovaries, ovarian horns and the uterine body Uterine horn has uterine arteries attached to it Follicles in different rates of development = circles coming out of ovaries Rabbits 2 cervixes, to uterine bodies, one vagina Uterus fills up all of abdomen when pregnant Need to know: Root Body Glands Urethra is found inside the prostate gland Corpus spongiosum (helps penis to become erect) surrounds the urethra Urethral grove where urethra travels through the bone If dog has inflamed prostate that can place pressure on the urethra which can lead to difficulty urinating Bobus glandus = area of tissue where it has spaces that can fill up with blood Need to know - Corpuis catheresum, spongiosum and the urethra Duct efferents going into the epidermis Closed castration is quicker, material from the abdomen could flow into the duct Open castration is beneficial for animals because it does not allow material from abdomen to flow into the duct and it is also easier to tie it off Epididymis is where sperm travels down