PPBM 1211 Anatomy and Histology of Urinary System PDF

PPBM 1211 Gross Anatomy and Histology: Urinary System Che Anuar Che Mohamad 11/12/2024  Learning outcome Able to describe the gross anatomy and histology of urinary system: kidneys, ureters, bladder and urethra Able to discuss the brief...

PPBM 1211 Gross Anatomy and Histology: Urinary System Che Anuar Che Mohamad 11/12/2024  Learning outcome Able to describe the gross anatomy and histology of urinary system: kidneys, ureters, bladder and urethra Able to discuss the brief function of certain selected important structures Able to relate with the clinical relevance of the structures Able to identify and discuss some common related fiqh issues Male Urinary Organs Female Urinary Organs Function of the Urinary System Two Kidneys – Perform all functions except actual excretion. Two Ureters – Convey urine from Kidneys to Urinary Bladder Urinary Bladder – Holds Urine until excretion Urethra – Conveys urine from bladder to outside  KIDNEYS: Introduction Shape: bean-shaped, paired. Average size – 12cm (long) x 6cm(wide) x 3 cm (thick) Weights 125-170 grams Location: Retroperitoneal, at posterior abdominal region. Both kidneys are immediately lateral to the vertebral column. They extend from vertebrae T12→ L3. Right kidney a bit lower than Left kidney (due to the position of liver). Location and Position of the Kidneys Pararenal fat Kidneys are enclosed by Renal fat and fascia.  Kidneys are enclosed by Renal fat and fascia: 1. Renal Capsule 2. Perirenal Fat / perinephric fat 3. Renal Fascia (fibrous connective tissues) 4. Pararenal Fat / paranephric fat “Capsule – fat – fascia – fat”  External Anatomy of the Kidney Superior pole Inferior pole Medial border-concave Renal Hilum Lateral border Anterior surface Posterior surface Renal hilum and sinus Internal Anatomy of the Kidney Cortex - Superficial region of kidney. It is light and granular Renal column- Extensions of cortex that separate renal pyramids within the medulla. Medulla - Deep central region of the kidney and darker Renal pyramids- Cone shaped structure within the renal medulla.  Kidney Internal Anatomy Renal Pelvis Flat funnel-shaped expansion of ureter Major Calices Large cup-shaped branches of renal pelvis Minor Calices Cup-shaped divisions of major calices Surround papilla of pyramid Combination of a few minor calices forms major calyx 2 or 3 major calices will unite to form renal pelvis.  Renal Lobe Consists of: One renal pyramid overlying area of renal cortex ½ half adjacent tissues of renal columns Blood supply O.5% of total body mass- receive 20-25% Supply by the renal arteries – from aorta @ 2nd lumbar Renal artery divide into 5 segmental arteries Blood Supply and Flow  Nephrons The functional unit of kidney is the nephron. There are about 1 million nephrons in each kidney. There are 2 types of nephrons depending on the position in the kidney. Cortical nephrons (80-85%) Juxtaglomerular nephrons.(15-20%) Cortical vs Juxtaglomerulas Cortical nephron: >>> peritubular capillaries. Juxtamedullary nephron: >>> vasa recta. Vasa recta are special type of peritubular capillaries. They arise from efferent arteriole of Juxtamedullary nephrons and surround their LOH. Vasa recta are highly permeable to solute and water.  Microscopic structure of kidney (Nephron) One Nephron = Renal Corpuscle + Renal Tubules. 1. Renal corpuscle = Glomerulus (capillaries tuft) + Bowman’s capsule. 2. Renal tubules = Proximal Convoluted Tubule (PCT), Collecting Loop of Henle (LOH), Distal duct Convoluted Tubule (DCT). From each nephron, urine drains into collecting tubule→ Collecting Duct Note that (in general): → renal papilla → minor & major Cortex: Renal corpuscles, PCT, DCT Calyx → Renal Pelvis → Ureter. Medulla: Loop of Henle, Collecting Duct.  Histology of the Nephrons Structurally nephrons is made of 2 parts: Renal corpuscle Renal tubule  Cortex and Medulla Cortex – There is the presence of glomeruli in the cortex. Medulla –It is characterized by the presence of collecting tubule.  Histology of the Nephrons Renal Corpuscle has 2 parts: Bowman’s capsule – cup-shaped extension of the renal tubule that surrounds the glomerulus Inner membrane is made of visceral epithelium - modified simple squamous epithelial (podocytes). Outer membrane is made of parietal epithelium (simple squamous epithelia). Capsular space: b/w parietal and visceral epithelium. Glomerulus – is a specialized capillary bed inside the bowman’s capsule. attached to afferent and efferent arterioles on both sides surrounded by podocytes. The blood pressure in the glomerulus is high - large afferent arteriole and smaller efferent arteriole. This result in high rate of filtration.  Histology of the Nephrons Renal Tubule is made of: Proximal convoluted tubule (PCT) – lies nearest to Bowman’s capsule. It wall has simple cuboidal epithelium with microvilli. Loop of Henle – Descending limb has simple squamous epithelium in the wall. Thin ascending limb has simple squamous epithelium in its wall. Thick ascending limb has simple cuboidal to low columnar Distal Convoluted tubule (DCT) – extends beyond the ascending limb of Henle’s loop; loops back passing near the glomerulus to form juxtaglomerular apparatus. The wall is made of simple cuboidal epithelium Collecting tubule/duct – extends from the DCT to the papillary ducts. Its wall is made of simple columnar epithelium. Receives urine from many nephrons and passes through the medullary pyramids to reach the papillary ducts. Papillary ducts - Collect urine from the collecting ducts. It empties the urine into the minor calyces  At each nephron: Juxtaglomerular Apparatus Juxtaglomerular apparatus (JGA) is a specialized structure formed by: (i) Macula Densa of Distal convoluted tubule (DCT), (ii) Juxtaglomerular cells (aka granular cells) of Afferent Arteriole (AA) (secretes renin) and, (iii) Extraglomerular mesangial cells. Main function of JGA is secretion of renin, which regulates systemic blood pressure via the Renin- Angiotensin system (RAS). **Macula densa detect sodium concentration in fluid in tubule. **each JGA is located within the same nephron, next to its glomerulus (hence ‘juxta’)  JGA (of Afferent arterioles) PCT, JGA, Glomeruli and DCT Functions of Kidneys Carry out four(4) functions Filter nitrogenous wastes, toxins, ions, etc. from blood to be excreted as urine. Regulate volume and chemical composition of blood (water, salts, acids, bases). Produce regulatory enzymes. Renin – regulates BP/ kidney function Erythropoietin – stimulates RBC production from marrow. Metabolism of Vitamin D to active form.  Clinical relevance 1. Blood supply of the kidney Renal cortex receives ~90% of the blood supply to the kidneys. Renal medulla: relatively ischemic ▪ Renal vessels are end arteries and there is no collateral circulation. Therefore occlusion of any branch of a renal artery produces infarction 2. Renal transplantation Definitive treatment for end stage renal failure (ESRF) 3. Renal Cell Carcinoma Ureters 25-30cm Continuation of renal pelvis Thick-walled and narrow tube Slender tubes that transport urine from kidneys to bladder Retroperitoneal Runs behind the peritoneum Ureter behind peritoneum Constriction of ureter Blood supply Renal, testicular/ovarian, common iliac and inferior vesicle arteries (from internal iliac artery) Veins terminate in the corresponding trunks  Histology of Ureters: Histology: comprised of three layers of tissue. a. Mucosa: inner layer – Made of transitional epithelium and lamina propria. Secretes mucus and protects the walls of the ureters from urine which is much more acidic. b. Muscularis: Middle layer - Made of smooth muscle tissue whose primary function is peristalsis. c. Adventitia – Connective tissue that functions to protect and anchor the ureters in place within the abdominopelvic cavity Ureters Clinical Relevance Ureteral narrowing are clinically significant because they are common locations for urinary calculi to lodge during passage.  Urinary Bladder A collapsible muscular sac Bladder wall- detrusor muscle Full bladder – spherical Expands into the abdominal cavity *Empty bladder – lies entirely within the pelvis Urinary Bladder It is a muscular sac that stores and expels urine. Capacity averages 700-800ml Smaller in female Location Pelvic floor Posterior to public symphysis Anterior to Rectum in males Vagina & uterus in females Location of the Bladder Trigone of the bladder  Urethral Sphincter Internal urethral sphincter Involuntary smooth muscle External urethral sphincter Skeletal muscles Voluntarily inhibits urination Relaxes when one urinates Blood supply of the bladder -superior and middle vesical arteries (from umbilical artery) -inferior vesicle artery (from internal iliac Artery) -vein pass to the internal iliac trunk Urinary Bladder  Histology of the Urinary Bladder Wall of bladder Mucosa -Transitional epithelium. - Lamina propria: loose connective tissue Submucosa: Loose connective tissue and blood vessels and nerve endings. Muscular layer: Three layers of smooth muscle (detrusor muscle) Adventitia Histology of Urinary the Urinary Bladder Histology of the Urinary Bladder Clinical Relevance 1. Relation with urinary incontinence In infant - due to incomplete development of neurons to external ureteric sphincter Also occurs in adults Eg: Flaccid Bladder – Spinal Cord Transection S2-S4 2. Bladder stone/calculi 3. Bladder Ca  Urethra In females Length of 3–4 cm In males – 20 cm in length – three named regions Prostatic urethra Passes through the prostate gland Membranous urethra Through the urogenital diaphragm Spongy (penile) urethra Passes through the length of the penis Male urethra  Female Urethra The urethra is located anterior to the anterior vaginal wall. Anterior vaginal wall is the posterior wall of the female urethra. Epithelium of the Urethra Transitional epithelium At the proximal end (near the bladder) Stratified and pseudostratified columnar – mid urethra (in males) Stratified squamous epithelium At the distal end (near the urethral opening) Male Urethra in Corpus Spongiosum Urethra in relaxed vs distended  Disorders Urinary tract infections More common in females Burning sensation during micturition  Jurisprudence/fiqh issues The superiority of purity and cleanliness in Islamic faith and jurisprudence “There are ten qualities of fitrah: trimming the moustache, sparing the beard, siwak (brushing the teeth), rinsing the mouth and inhaling water (to clean the nose), clipping the nails, washing the finger knuckles, plucking the armpit hai, shaving the pubic hair, washing the private part with water, and circumcision”. (Muslim, Abu Dawud and others). disorder in urinary system may affect physical impurity rukhsoh/ concessionary law to those affected by urine incontinence With urine bag  Thank You May Allah guide us all