Gross Anatomy and Histology of the Urinary System PDF

4.06 Nov 26, 2015 GROSS ANATOMY AND HISTOLOGY OF THE URINARY SYSTEM Dra. Sta Ana I. Gross Anatomy of the Urinary System LEARNING OBJECTIVES...

4.06 Nov 26, 2015 GROSS ANATOMY AND HISTOLOGY OF THE URINARY SYSTEM Dra. Sta Ana I. Gross Anatomy of the Urinary System LEARNING OBJECTIVES A.Component Parts  Demonstrate knowledge and understanding of the B.Functions gross anatomy of the kidney by: C. Kidney o Identifying the right and left kidneys, their position 1. Gross Structure of the Kidney in the posterior abdominal wall and laterality once 2. Position of the Kidney dissected from the cadaver. 3. Anatomic Relations o Describing the different coverings of the kidney. 4. Renal Fascia and Renal Capsules o Identifying the renal arteries, veins and ureters at 5. Structure of the Kidneys the renal sinus. 6. Renal Parenchyma o Describing the vascular supply, innervation and D. Blood Supply to the Kidney lymphatic drainage of the kidneys. 1. Vascular Renal Segments and Arterial Blood o Differentiating the outer cortex and inner medulla Supply on the sectioned kidney. 2. Vascular Drainage o Describing the renal pyramid, major and minor 3. Medullary Blood Supply calyces, renal columns of Bertin, and renal papillae E. Suprarenal Glands (Adrenal Glands) of the medulla. 1. Parts o Identifying the subcapsular zone, cortical arches 2. Supply to the Suprarenal Glands and medullary rays at the cortex. a. Arterial Blood Supply  Demonstrate knowledge and understanding of the b. Venous Drainage histology of the kidney by: c. Nerve Supply o Defining the principal parts of the uriniferous F. Ureters tubules. 1. Ureteric Relations o Enumerating the parts of the nephron and 2. Parts recognizing the two types of nephrons in the 3. Ureters: Uterine Vessels and Urinary Bladder kidney, the juxtamedullary and cortical nephrons. 4. Ureteric Constrictions o Describing the histological features of each 5. Blood Supply and Venous Drainage of the segment of the nephron relating structure to Ureters function. G.Innervations of Kidneys, Ureters and o Describing the parts of the juxtaglomerular Adrenal Glands apparatus and gives its clinical importance. H. Lymphatics of the Urinary System o Differentiating the composition of the cortex and I. Urinary Bladder medulla. 1. Parts o Defining the lobes and lobules of the kidney. 2. Orientation of the Urinary Bladder o Stating the hormonal function of the kidney. 3. Ligament Support o Describing the histologic features of collecting 4. Blood Supply tubules and tracing the flow of the glomerular 5. Venous Drainage filtrate from the DCT to minor calyces. 6. Innervations  Demonstrate knowledge and understanding of the 7. Lymphatic Drainage gross anatomy of the urinary passages (ureters, urinary J. Urethra bladder, urethra) by: 1. Male Urethra o Describing the parts, course and relations of the 2. Female Urethra ureters. 3. Blood Supply and Venous Drainage of the o Identifying the areas of normal constrictions along Urethra the course of the ureter. 4. Innervation o Enumerating and identifying parts of the urinary 5. Lymphatic Drainage bladder (fundus, apex, body base and neck) and its II. Histology of the Urinary System ligaments. A.Nephrons o Describing the mucosal surface of the urinary 1. Renal Corpuscle bladder. 2. Renal Tubules o Differentiating between the male and female 3. Organization of the Renal Vasculature urethra. B.Ureters o Identifying the female urethra as it extends from C. Urinary Bladder the neck of the bladder to the vestibule. D. Urethra o Describing the blood supply, innervation, and III. Embryology lymphatic drainage of the ureters, urinary bladder, and urethra. 1 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System  Demonstrate knowledge and understanding of the I-C-2. POSITION OF THE KIDNEY histology of the urinary passages (ureters, urinary  Left kidney is 1-2cm higher than the right kidney due to bladder and urethra) by: the position of the liver (from the lecturer) o Describing the layers of the walls of the urinary  The transpyloric plane passes through the superior passages. pole of the right kidney, which is approximately o Defining the transitional epithelium. 2.5cm lower than the left pole, propbably due to the o Comparing the lining of the urethra in its proximal presence of the liver (Moore) and distal portions.  Right kidney beside Inferior Vena Cava  Demonstrate knowledge and understanding of the  Left Kidney beside Aorta embryonic development of the urinary system by: o Describing the development of the different parts  Between Left and Right Kidneys: Celiac plexus, ANS of the urinary system arising from the ganglia metanephros and the ureteric bud (from the mesonephros). o Differentiating the development of the male from the female urinary system. I. GROSS ANATOMY OF THE URINARY SYSTEM I-A. COMPONENT PARTS  Kidneys – process a filtrate of the blood to form the urine  Ureters – conduct urine from the kidney to bladder  Urinary bladder – temporary storage of urine  Urethra – passage through which urine is voided I-B. FUNCTIONS  Excretory: Waste products of metabolism is excreted through production of urine  Maintenance of body homeostasis: Kidneys maintain the acid base balance of the body and maintain the normal body fluid by eliminating excess water Figure 1. Diagram of kidneys in situ. (Netter)  Endocrine: Releases of hormones erythropoietin and renin I-C-3. ANATOMIC RELATIONS  Reproductive: Male: Urethra is also a passageway for semen I-C. KIDNEY I-C-1. GROSS STRUCTURE OF THE KIDNEY  Bean shaped, reddish brown organ  Retroperitoneal  Extends from T12 – L3 ***Editor’s Note: Superior parts of the kidneys lie deep to the 11th and 12th ribs. The levels of the kidneys change during respiration and with changes in posture. Each kidney moves 2-3cm in a vertical direction during the movement of the diaphragm that occurs with deep breathing. The inferior pole of the right kidney is approximately a finger’s breadth superior to the iliac crest***  Weight: 120-170g (average: 150g)  Length: 10-12 cm  Width: 5-6cm  Anterior-posterior thickness: 3-4cm Figure 2. Posterior Abdominal wall showing the great vessels, kidneys and suprarenal glands (Moore) 2 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System  Anterior Relations: I-C-4. RENAL FASCIA AND RENAL CAPSULES The principal anterior relation of the kidneys is the Serve as protection and cushion for kidneys peritoneum and organs that are in close approximation to the posterior abdominal wall  Fibrous/True Renal Capsule o Right Kidney: o Thin/fibrous glistening membrane  Liver o Encloses the renal parenchyma  Ascending colon o Represents true capsule  Duodenum – 2nd part o Directly in contact with the kidney o Can be stripped off from normal parenchyma ***Right kidney is separated from the liver by the o Provides barrier against spread of infection hepatorenal recess***  Perirenal/Perinephric Fat ***The right suprarenal gland is at the level of the o Surrounds kidneys and adrenal glands as it extends omental foramen (Foramen of Winslow)*** to their hollow centers, the renal sinuses o Left Kidney: o Serve as cushion  Tail of pancreas o Superior:  Spleen – connected to kidney via splenorenal  Anterior and posterior fuse ligament  Separates the kidney from adrenal gland  Stomach – greater curvature  Continuous with the diaphragmatic fascia  Descending colon  Causes the kidney to move during respiration  Jejunum o Inferior: no fusion of anterior and posterior  Posterior relations: covering; posterior descends downward and fuses o Upper 1/3: with iliac fascia  Diaphragm o Clinical Significance:  12th rib During infection/injury, pus or blood from the kidney o Lower 2/3: can travel inferiorly toward pelvic area or vice versa.  Psoas major muscles medially  Fibrous Renal Fascia/Gerota’s Fascia  Quadratus lumborum o Membranous layer  Transversus abdominis fascia – laterally o Fascia enclosing perirenal fat, kidneys and o Nerves: (descend diagonally across the posterior suprarenal glands surface of the kidney)  Continues medially to ensheath the renal  Subcostal or 12th intercostal n. vessels, blending with the vascular sheath  Iliohypogastric n. o Referred to as renal fascia  Ilioinguinal n. o It also sends collagen bundles through the Clinical Importance: paranephric fat The usual surgical approach to kidneys is from the  Periureteric Fascia posterior abdominal wall since they are retroperitoneal. If o Extension of the renal fascia prolonged along the the approach will be from the anterior, more organs will have ureter inferomedially to be crossed making them prone to injury.  Pararenal/Paranephric Fat o Continuous with extraperitoneal fat of the lumbar region that is most obvious posterior to the kidney o External to the renal fascia Figure 4. Renal Fascia. (Netter) Figure 3. Posterior relations of kidneys (Netter) 3 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-C-5. STRUCTURE OF THE KIDNEYS Figure 6. External and internal appearance of kidneys (Moore) Figure 5. Right kidney sectioned in several planes. (Netter) I-C-6. RENAL PARENCHYMA  Cortex (outer) – contains all the nephrons; dark brown;  Convex lateral border; concave medial border grainy  Renal hilum o Cortical arches – separate renal pyramids from o entrance to renal sinus and transmits renal vessels surface of kidney  renal vein o Medullary rays – fine delicate processes  renal arteries (2) representing bundles of tubules  ureter  Medulla (inner) – contains 6-10 medullary pyramids Tip: Knowing the arrangement of the vessels will help in o Apex – cupped within minor calyx identifying the laterality of the kidney  Renal papilla  Renal Hilum  Area cribrosa – perforations at the renal o A vertical cleft in the concave medial margin of papilla where urine passes towards the ureter each kidney o Renal columns of Bertin – between pyramids o Entrance to a space within the kidney, the renal o Base – medullary rays made up of collecting sinus tubules and loop of Henle o The renal vein is anterior to the renal artery, Note: which is anterior to the renal pelvis Each medullary pyramid plus the cortical tissue at its base  Renal sinus and along its sides constitute a renal lobe. o Structures that serve the kidneys (vessels, nerves, In infants, renal lobules are outlined on the outer surface of renal pelvis, calices, that drain urine from the the kidney. kidney) enter and exit the renal sinus through the renal hilum I-D. BLOOD SUPPLY TO THE KIDNEY ***The hilum of the left kdiney lies near the transpyloric plane, approximately 5 cm from the median plane***  Renal pelvis o Flattened, funnel-shaped extension of the superior end of the ureter o Receives 2-3 major calyces, each of which divides into 2-3 minor calyces o Each minor calyx is indented by a renal papilla, the apex of the renal pyramid, from which the urine is exreted o Apex of the renal pelvis  Continuous with the ureter **The renal sinus and renal pelvis are located in the concave part of the kidney*** 4 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-D-3. MEDULLARY BLOOD SUPPLY  Vasa Recta Vera o “True” vasa recta o Arise directly from arcuate or interlobular arterioles  Vasa Recta Spuriae o “False” vasa recta o From efferent arterioles of JGA I-E. SUPRARENAL GLANDS Figure 7. Renal blood supply. I-D-1. VASCULAR RENAL SEGME NTS AND ARTERIAL BLOOD SUPPLY  The renal arteries arise at the level of the IV disc Figure 8. Suprarenal glands above the kidneys. between L1 and L2 vertebrae.  The longer right renal artery passes posterior to  Also called the Adrenal Glands the IVC  Yellowish in living persons  Each artery divides close to the hilum into 5  Endocrine glands located between the superomedial segmental arteries that are end arteries aspects of the kidneys and the diaphragm containing o Meaning they do not anastomose significantly considerable amount of perinephric fat with other segmental arteries, so that the area  Enclosed by renal fascia by which they are attached to supplied by each segmental artery is an the crura of the diaphragm independent, surgically resectable unit or renal  Major attachment is to the crura of the diaphragm and segment not the kidneys (kidneys are just their primary  Segments: relationship) o Apical: Apical Segmental Artery  Right Suprarenal Gland o Anterosuperior: Anterosuperior Segmental o Pyramid shaped Artery o Lies behind the right lobe of the liver o Anteroinferior: Anteroinferior Segmental Artery o Extends medially behind the IVC o Inferior: Inferior Segmental Artery o Situated over the superior pole relative to the ***Apical, anterosuperior, anteroinferior and inferior kidney arteries originate from the anterior branch of the renal o Lies anterolateral to the right crus of the artery*** diaphragm o Posterior: Posterior Segmental Artery  Left Suprarenal Gland  Originates from a continuation of the posterior o Crescent shaped branch of the renal artery o Lies medial to the superior half of the kidney I-D-2. VASCULAR DRAINAGE o Lies behind the pancreas, lesser sac, and stomach  Both kidneys drain to the renal veins which then o Rests posteriorly on the diaphragm drains to the inferior vena cava o Renal veins lie anterior to the right and left renal arteries  Left renal vein is longer than the right renal vein, because of the location of the inferior vena cava (right) o Receives the left suprarenal vein, left gonadal vein and a communication with the ascending lumbar vein 5 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-E-1. PARTS I-F. URETERS  2 muscular tubes (one from each kidney) whose peristaltic contractions convey urine from the kidneys to the urinary bladder  Retroperitoneal in location  20 – 25 cm in length  Thick walled and narrow Figure 9. Cross section of adrenal gland  Suprarenal Cortex o Outer region (in cross section image above) o Derived from neural crest from the lecturer o Derives from mesoderm (Moore) o Function: secrete androgen and corticosteroids to retain sodium and water in response to stress, increased blood volume and BP  Suprarenal Medulla o Inner part (in cross section image above) o Mass of nervous tissue permeated with capillaries and sinusoids that derives from neural crest cells associated with the sympathetic nervous system (Moore) o Derived from neuroectoderm (from lecturer) o Contains Chromaffin cells  Secrete catecholamine (epinephrine & Figure 10. The course of the ureters norepinephrine) As the ureters cross the bifurcation of the common iliac I-E-2. BLOOD SUPPLY, VENOUS DRAINAGE, AND artery, they pass over the pelvic brim, thus leaving the INNERVATION OF SUPRARENAL GLANDS abdomen and entering the lesser pelvis. The pelvic Abundant blood supply due to endocrine functions parts of the ureters run on the lateral walls of the pelvis, parallel to the anterior margin of the greater sciatic  Arterial blood supply notch, between the parietal pelvic peritoneum. o Superior suprarenal artery (branch of inferior Opposite the ischial spine, they curve anteromedially, phrenic artery) superior to the levator ani, and enter the urinary o Middle suprarenal artery (direct branch of bladder. The inferior ends of the ureters are abdominal aorta) surrounded by the vesical venous plexus o Inferior suprarenal artery (branch of renal artery) I-F-1. URETERIC RELATIONS  Venous drainage  Right ureter: lateral to the IVC o Short Right suprarenal vein which will drain to  Left Ureter: lateral to the abdominal aorta; inferior the inferior vena cava mesenteric vein lies close to its medial aspect o Longer Left suprarenal vein often joined by the I-F-2. PARTS inferior phrenic vein which will drain to the left renal vein then to the inferior vena cava  Renal pelvis – funnel-shaped, superior part  Nerve Supply  Abdominal ureter – runs medially to the psoas muscle o Celiac plexus and crosses the genitofemoral nerve then obliquely o Abdominopelvic splanchnic nerves crossed by the gonadal vessels (males: testicular o Presynaptic sympathetic fibers – derived from arteries & veins; females: ovarian arteries & veins) lateral horn of gray matter of the spinal cord o Closely adherent to the parietal peritoneum; the (T10-L1) ureter can be tended up as the peritoneum is drawn anteriorly and can lead to injuries  Pelvic ureter (pelvic brim) – as it passes the common iliac artery; it lies anterior to the internal iliac artery  Intravesical ureter – as it enters the bladder 6 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-F-3. UTERINE VESSELS AND URINARY Clinical Correlation: Inflammation and distention of the BLADDER RELATIONS ureter secondary to ureteric stones/ calculi may manifest as intense, colicky (abdominal pain), intermittent pain. Pain is usually felt ipsilaterally (same side as the pathology), from the flank to the inguinal region. The pain distribution reflects the pathway where the renal pelvis and the ureters send their visceral afferent fibers to spinal cord segments T11-L2. However, pain is felt at the cutaneous areas at the lumbar and inguinal regions that are innervated by the spinal cord segments and sensory ganglia T11-L2 – referred pain – pain is also perceived in the dermatomes supplied by T11-L2. Pain may also extend to the proximal anterior thigh by projection through the genito-femoral nerve (L1-L2) and scrotum (males) and labia majora (females). I-F-5. BLOOD SUPPLY AND VENOUS DRAINAGE OF THE URETERS Figure 11. Superior view of pelvic viscera of female (peritoneum removed). (Netter)  Arterial blood supply o Renal arteries (giving a constant supply) o Testicular arteries / Ovarian arteries  Cross iliac vessels to enter pelvis near the bifurcation of o Common iliac artery internal and external arteries o Some branches of the abdominal aorta  Ureters course under the uterine vessels very near the o Branches approach the ureters medially and divide isthmus of the uterus to enter the bladder posteriorly into ascending and descending branches, (water under the bridge) forming a longitudinal anastomoses on the ureteric wall I-F-3. URETERIC CONSTRICTIONS o Blood vessels of ureters are easily traumatized during surgery  Venous drainage o Renal vein o Gonadal vein I-G. INNERVATION OF THE KIDNEYS, URETERS, AND ADRENAL GLANDS Figure 12. Ureteric Constrictions. (A) The arrows represent papillae bulging into the minor calices. (B) Sites at which relative constrictions normally appear: 1). At the junction of the ureters and renal pelvis; 2) Where the ureters cross the pelvic brim; 3) During their passage through the wall of the urinary bladder/vesico-ureteric junction Figure 13. Innervation of kidneys, ureters and adrenal glands. (Netter) 7 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System  Renal nerve plexus is supplied by fibers from the abdominopelvic (especially the least) splanchnic nerves. The nerves of the abdominal part of the ureters derive from the renal, abdominal aortic and superior hypogastric plexus. o Parasympathetic – vagus nerve and pelvic splanchnic nerves from S2-S4 supllies the kidneys, adrenals and ureters o Sympathetic – lesser and least splanchnic nerves from T10- supply the kidneys and ureters, secretomotor to adrenal medulla  Lumbar splanchnics from L1-L2  Abdominal part of ureters o Renal, abdominal aortic and hypogastric plexuses  Suprarenal glands o Celiac plexus, and the abdominopelvic (greater, lesser and least) splanchnic nerves ***Ureteric pain is usually referred to the ipsilateral lower quadrant of the anterior abdominal wall and especially to the groin*** I-H. LYMPHATICS OF THE UR INARY SYSTEM Figure 14. Lymphatics of the urinary system  The renal lymphatic vessels follow the renal veins and drain into the right and left lumbar (caval and I-J. URINARY BLADDER aortic) lymph nodes  Extraperitoneal organ that lies within the pelvis behind  Kidneys, suprarenal glands and superior part of ureter the pubic bone -> lumbar nodes o Include the caval (near the IVC) and aortic nodes  Acts as receptacle for urine (along the abdominal aorta)  Strong muscular wall (Detrusor muscle)  Middle part of ureter drain into the common iliac  It is distensible nodes whereas vessels from its inferior part drain into  When empty, it appears “boat” shaped and is located in the common, external and internal iliac lymph the lesser pelvis, lying partially superior to and nodes partially posterior to the pubic bones ***The suprarenal lymphatic vessels arise from a  As the bladder fills, it enters the greater pelvis as it plexus deep to the capsule of the gland and from one in ascends in the extraperitoneal fatty tissue of the its medulla. The lymph passes to the lumbar lymph anterior abdominal wall. nodes*** ***In some individuals, a full bladder may ascend to the level of the umbilicus***  Lymphatic vessels drain to the nodes it is nearest to. So the upper part is associated with the lumbar nodes.  Retropubic Space (of Retzius) Ureter, suprarenal glands and kidneys drain to lumbar o Separates the bones from the urinary bladder nodes. Middle and inferior part drain to common iliac,  Assumes oval shape when filled with urine. external and internal nodes.  In adults, the bladder lies within the lesser pelvis, but in infants, the bladder is found in the abdominal cavity  The bladder is enveloped by a loose connective tissue visceral fascia 8 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-J-2. ORIENTATION OF THE URINARY BLADDER  In males: prostate gland is attached directly to the base of the bladder and it lies anterior to the rectum o Fundus is separated from the rectum centrally by only the fascial rectovesical septum and laterally by the seminal glands and ampullae of the ductus deferentes  In females: bladder rests directly on the pelvic floor inferior to the uterus and is closely related to anterior vaginal wall Figure 15. Superior view of the urinary bladder (Netter) I-J-1. PARTS  Fundus – central and superior-posterior part that expands freely, rises above pubic crest o Opposite the apex, formed by the somewhat convex posterior wall  Apex – Anterior-superior portion connected to anterior abdominal wall by median umbilical ligament o Points toward the superior edge of the pubic Figure 17. Comparison of male (top) and female (bottom) urinary symphysis when empty bladder orientations (Netter)  Body – between the apex and fundus, postero-inferior part, has the two ureteric orifices I-J-3. LIGAMENT SUPPORT  Base – lies on the pelvic floor where the ureteric orifices and the internal urethra meatus form the  Contain smooth muscle fibers that hold bladder in trigone position.  Neck – continuous with urethra  Median umbilical ligament o Where the inferolateral surfaces meet o Remnant of urachus inferiorly o Fibrous cord extending from apex of urinary bladder to umbilicus  Lateral umbilical ligament o Stabilizes bladder anteriorly together with the medial umbilical ligament  Puboprostatic ligament in males/pubovesical ligaments of the bladder o Stabilizes the neck of the bladder Figure 16. Parts of the Urinary Bladder 9 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-J-5. VENOUS DRAINAGE O F THE BLADDER median umbilical ligament  Perivesical plexus (Trans 2018) o Around the base of bladder then drain into inferior vesicle v. lateral o Inferior vesical vein umbilical  Vesical Venous Plexus (Moore) ligament o The venous network that is most directly associated with the bladder itself. o Mainly drains through the inferior vesical veins  internal iliac veins. o May also drain through the sacral veins into the internal vertebral venous plexus. o In males:  Vesical venous plexus is continuous with the prostatic venous plexus and the combined puboprostatic ligament plexus complex envelops the fundus of the bladder and prostate, the seminal glands, the ductus deferentes and the inferior ends of the ureters. Figure 18. Diagram of the ligaments supporting the bladder  Also receives blood from deep dorsal vein of the penis  prostatic venous plexus I-J-4. BLOOD SUPPLY TO T HE BLADDER o In females:  Vesical venous plexus envelops the pelvic  Internal iliac artery (main) part of the urethra and the neck of the o Superior vesical artery - supplies bladder. superolateral/anterosuperior parts of bladder  Receives blood from the dorsal vein of the o Inferior vesical artery – supplies ureter fundus and clitoris  vaginal/ uterovaginal venous neck of bladder, prostate and urethra in males plexus  In females: have the vaginal a. instead of inferior vesicle a. and send small branches to postero-inferior parts of the bladder. o Obturator and Inferior Gluteal Arteries- supply small branches to the bladder. Figure 19: Pelvic Veins Figure 18: Pelvic Arteries 10 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-J-6. INNERVATIONS A median ridge containing the utricle which opens into the urethra  Sympathetic  Prostatic sinuses (where prostatic glands o Conveyed from inferior thoracic and upper open) lumbar spinal cord levels to the visceral (pelvic) plexuses  Seminal Colliculus: rounded eminence in o Hypogastric plexus (L1-L2) or “filling nerves” the middle of the urethral crest with a slit- o Inhibit detrusor ms. contraction like orifice that opens into a small cul-de- o Increase urethral sphincter tone sac.  Parasympathetic  Prostatic Utricle (homologue of vagina and o From Sacral spinal cord levels cervix) – slit-like orifice that opens into a o Pelvic splanchnic nerves and inferior hypogastric small cul-de-sac nerves (S2-S4) or “emptying nerves”  Ejaculatory ducts – opens into the o Contracts the bladder verumontanum found at the lateral o Int. urethral sphincter relaxes margins of the ureter it is where urinary o In males int. urethral sphincter contracts during and reproductive system of males merge ejaculation which is a sympathetic function, to o Membranous Urethra prevent backflow. Retrograde flow of semen to  Shortest; 2 – 2.5 cm long (1.0-1.5 cm Moore) bladder. That is why there is no semen in the  Least dilatable o With the exception of the bladder. external orifice, the narrowest section of the urethra **Orgasm in Females: internal urethra contracts (Sta. Ana  Found within the urogential diaphragm from Elevazo, 2015)  Surrounded by urethral sphincter muscle o Spongy or Penile Urethra I-J-7. LYMPHATIC DRAINAGE  15 cm long  Anterior/superolateral wall  external iliac lymph  Longest and most mobile nodes  Found within the urogenital diaphragm  Posterior/fundus and neck  internal iliac lymph surrounded by the urethral sphincter nodes > sacral nodes and common iliac nodes  Traverses bulb, body, and glans of the body of the penis  Enclosed within the corpus spongiosum of I-K. URETHRA penis I-K-1. MALE URETHRA  Enlarges into Fossa Navicularis at the area of  Muscular Tube the glans  18 - 22 cm in length  Terminates at the external urethral meatus  Starts from internal urethral orifice in the urinary **See Appendix for the tabulated table bladder to external urethral orifice, located at the glans penis in males  4 Parts (Moore, for descriptive purposes) ; 3 Parts (2018 trans) o Intramural (preprostatic) part of urethra (Moore)  Varies in diameter and length  Depends when bladder is filling or emptying  Filling: Bladder neck is tonically contracted so the internal urethral orifice is small and high (Filling internal urethral orifice)  Emptying: The neck is relaxed so the orifice is wide and low (Emptying Internal Urethral Orifice) o Prostatic Urethra  3 cm long  Traverses through prostate gland and Figure 20: Interior of Male bladder and urethra terminate at superior fascia of urogenital diaphragm  Widest and most dilatable portion  Parts:  Urethral crest (posterior wall): Most prominent feature of prostatic urethra. 11 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System I-K-2. FEMALE URETHRA II. HISTOLOGY OF THE URINARY SYSTEM  Shorter than that of the male; 4 cm long(6mm II-A. NEPHRON diameter)  Structural and functional unit of the kidney  Passes antero-inferiorly from the internal urethral  Composed of the renal corpuscle and renal tubules orifice of the urinary bladder, posterior and then  Can be classified according to location: inferior to the pubic symphysis, to the external o Cortical nephron urethral orifice.  Located almost completely in the cortex  Exclusively a urinary organ  Shorter loop of Henle  Corresponds to the prostatic and membranous o Juxtamedullary nephron portions of male urethra  Found in the junction of the cortex and the  Extends from the bladder neck where it opens into the medulla vestibule below the clitoris and at the sides of the  With a longer loop of Henle going deeper into external urethral meatus the medulla  Paraurethral glands (homologue of prostate glands in o Note that all nephrons are found in the cortex males) found at sides of the external urethral meatus(present particularly at the superior part of urethra) I-K-3. BLOOD SUPPLY AND VENOUS DRAINAGE OF THE URETHRA  Male o Arterial Blood Supply  Prostatic branches of the inferior vesical and middle rectal a. – in prostatic urethra  Dorsal artery of the penis – in membranous and spongy urethra o Venous drainage  Prostatic venous plexus  Female o Arterial Blood Supply  Internal pudendal a. and vaginal a. o Venous drainage  Internal pudendal v. and vaginal v. Figure 21. Diagram showing juxtamedullary nephron (left) and cortical nephron (right) I-K-5. INNERVATION II-A-1. RENAL CORPUSCLE  Male o Prostatic nerve plexus(mixed sympathetic, parasympathetic, and visceral afferent fibers) proximal from hypogastric plexus (proximal urethra) o Dorsal nerve of penis from pudendal nerve (distal urethra)  Female o Vesical nerve plexus o Pudendal nerve plexus I-K-6. LYMPHATIC DRAINAGE  Male o Prostatic and membranous urethra → Internal iliac LN and external iliac LN o Spongy urethra → deep inguinal LN and external iliac LN  Female Figure 22. Micrograph of renal corpuscle. The glomerulus (G) of o Mostly on Sacral and Iliac nodes capillaries is surroundedby the capsular space (CS) covered by the simplesquamous parietal layer (PL) of Bowman capsule. Near the o Distal urethra: Inguinal nodes corpuscle is that nephron’s macula densa (MD) and sectionsof proximal convoluted tubules (PCT) and distal convoluted tubules (DCT). (Junqueira, 2013) 12 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System  Initial dilated part enclosing a tuft of capillary loops  Renal Corpuscle Poles  Always located in the cortex o Vascular pole  Site of blood filtration; always located in the cortex  Where the afferent arteriole enters and the  Composed of the glomerulus and glomerular efferent arteriole leaves (Bowman’s) capsule  Where you would find mostly the distal o Glomerulus – tuft of capillary loopsthat filter blood convoluted tubule and the juxtaglomerular o Bowman’s capsule – double-walled epithelial lining apparatus of the glomerulus  Simple squamous epithelium  Parietal layer o Urinary pole  forms the outer surface of the capsule  Continuous with the proximal convoluted  lined by simple squamous epithelium tubule  supported by basal lamina with reticular  Lining changes to simple cuboidal epithelium fibers in this area  Visceral layer – closely envelopes the glomerular capillaries, which are finely  Glomerular Filtration Membrane fenestrated o Made up of fenestrated capillary endothelium, glomerular basement membrane and filtration slits *Mesangium o Primary urine (filtrate) passes through the  Found in interstices between capillaries filtration slits into the urinary space; large that lack podocytes proteins, RBCs and other large solutes are  Made up of mesangial cells and matrix prevented from entering  Functions: o Responsible for ultra-filtration of blood o Physical support of capillaries within the glomerulus o Helps maintain hydrostatic pressure for optimal filtration rate because it is responsive to vasoactive substances o Mesangial cells phagocytose protein aggregates adhering to the glomerular filter o Secretes cytokines, prostaglandins and other factors for immune defense and repair within the glomerulus Figure 17. Diagram showing parts of the glomerlar filtration membrane (Junqueira, 2010) II-A-2. RENAL TUBULES  Proximal Convoluted Tubule o Initial segment of the renal tubule Figure 23. Diagram of mesangium. Mesanglial cells in areas not o Longest part of the nephron covered by podocyte processes (Junqueira, 2013) o Has 2 parts  Pars Convoluta – a long convoluted part,  Capsular/urinary space – between the 2 located entirely in the cortex capsular layers; receives the fluid filtered  Pars recta –a shorter straight part that enters through the capillary wall and visceral layer the medulla 13 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System o Primary function is to reabsorb 65% of the water, electrolytes and organic nutrients from the ultra- filtrate o Both reabsorption and secretion o Lined by simple cuboidal epithelium with brush border o Appears to have a small, hazy lumen because of the brush border that function for absorption o Larger cell size compared to DCT, acidophilic- staining because it has more mitochondria  Loop of Henle (nephron loop) o U-shaped structure with a thin descending and thin ascending limb composed of simple squamous epithelium  Thick descending and ascending parts are made up of the straight segment of the PCT and DCT respectively Figure 23. a) Micrograph showing continuity of the (TP) urinary  The thin ascending limb of the loop becomes pole of the renal corpuscle and (P) PCT. (U) Urinary Space (G) the thick ascending limb, with simple Glomerulus cuboidal epithelium. b) Comparison of PCT and (D) DCT. (Junqueira, 2013) o Only the loops penetrate the medulla, the rest of the  Juxtaglomerular Apparatus nephron is located in the cortex o Seen in the vascular pole of the glomerulus o Important in making the urine hypertonic; o Main function is regulation of blood flow to keep conserves water the GFR constant o The thin limb is lined by simple squamous o Components: epithelium while the thick limb is lined by simple  Macula Densa cuboidal epithelium with some brush border  Part of the DCT  the thin limb has a more distinct lumen  Appears as closely packed columnar o Thick Ascending Limb cells  The cuboidal cells of the loops of thick  Comes into contact with the smooth ascending limb actively transport sodium muscles of the afferent arteriole and chloride ions out of the tubule against a  JG cells of afferent arterioles concentration gradient into the  Lacis cells – functions similarly to mesangial hyaluronate-rich interstitium, making the cells within the glomerulus compartment hyperosmotic. o Look for this in Histo Lab because the JGA is always o Thin Ascending Limb asked in the exam  Reabsorbs NaCl but are impermeable to  Collecting Tubules water. o Found in the medulla o Composed mainly of pale-staining principal  Distal Convoluted Tubule cells with few organelles, sparse microvilli, and o Has 3 parts: pars recta, pars convoluta, pars usually distinct cell boundaries maculata (macula densa) o Receive urine from the DCT o thick straight part ascending from the loop of Henle o Tubules join to form the collecting duct or papillary back into the cortex and a convoluted part ducts of Bellini to empty into the minor calyces completely in the cortex o Carries out final mechanism of urine concentration o Transports ions to maintain the acid-base balance system – there is still reabsorption of water in the blood o Large compared to the DCT, pale-staining o Smaller compared to the PCT; more distinct nuclei; o Lined by simple cuboidal epithelium lumen appears widerand empty o Principal cells with aquaporins – pore proteins that o Lined by simple cuboidal epithelium with very few help the tubule absorb water to no brush border o ADH- released from the pituitary gland as the o Rate of Na+ absorption here is regulated by body becomes dehydrated aldosterone from the adrenal glands. o Intercalated cells – scattered among the principal cells; darker; more abundant mitochondria and projecting apical folds; helps maintain acid-base balance by secreting H+ or HCO3 14 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System II-B. URETERS  Stellate-shaped lumen  Lined by transitional epithelium or urothelium – expands and flattens with distension o Single layer of small basal cells o Intermediate region containing one to several layers of columnar cells o Umbrella cells  Bi- or Multi-nucleated cells  Very large, polyhedral or bulbous cells  Highly differentiated to protect underlying cells against the cytotoxic effects of hypertonic urine Figure 24. Cross section through a medullary pyramid showsthe  Responsible for expression of uroplakin simple squamous epithelium of the thin descendingand ascending limbs of loops of Henle (T) and its thickascending limbs (A), as proteins – protect the lining of the ureter, wellas the pale columnar cells ofcollecting ducts. (Junqueira, 2013) bladder and parts of the urethra from the formed urine  Lamina propria – Highly vascularized  Muscularis mucosa – Urine moves through peristaltic II-A-3. ORGANIZATION OF THE RENAL movement VASCULATURE o Inner longitudinal layer Renal artery o Outer circular layer ↓  Adventitia Segmental artery ↓ Interlobar artery (between the pyramids) ↓ Arcuate artery (at the base of each pyramid) ↓ Interlobular artery ↓ Afferent arteriole ↓ Glomerulus ↓ Efferent arteriole Figure 25. Cross section of the ureter (Junqueira, 2013) ↓ ↓ Peritubular capillaries vasa recta (associated with II-C. URINARY BLADDER (associated with nephron loop, participates convoluted tubules, in counter-current  Lined by transitional epithelium with umbrella cells supplies the glomerulus ) mechanism) o When the bladder is empty, the mucosa is highly ↓ ↓ folded interlobular vein o When the bladder is full, the mucosa is pulled ↓ smooth, the urothelium is thinner, and the arcuate vein umbrella cells are flatter ↓  Lamina propria – connective tissue bed that contains interlobar vein blood vessels (highly vascularized) ↓  Muscularis mucosae consists of 3 poorly delineated segmental vein layers of the detrusor muscle ↓ o Inner and outer longitudinal smooth muscle layers o Middle circular smooth muscle layer renal vein ↓  Upper part of bladder is covered by serous peritoneum, the rest of the urinary passages are covered by IVC adventitial layer. (Junquiera, 2010). 15 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System Lined  by stratified columnar epithelium and pseudostratified epithelium  Muscularis externa: inner longitudinal and outer circular layer o Spongy urethra  Enclosed within erectile tissue of the penis.  Initially lined by stratified columnar epithelium and pseudostratified epithelium becoming non-keratinized stratified squamous epithelium as it nears opening (for protection)  In females o Lining epithelium:  Proximal: transitional epithelium  Distal: stratified squamous non- keratinized epithelium Figure 26. Micrograph showing the 4 layers of the urinary bladder  Middle: surrounded by external Wal (LP) Lamina Propria (IL) Inner Layer (OL) Outer Layerl sphincter (striated ms.) (Junqueira, 2013) Figure 28. Micrograph showing the folds of the urethra as well as the transitional epithelium (Junqueira, 2013) Figure 27.A. The micrograph shows the folded mucosa, submucosa, III. EMBRYOLOGY and muscularis of the empty bladder wall, with an enlargement The kidneys develop from 3 slightly overlapping systems showing the urothelium and lamina propria. B. The bladder formed in a cranial-to-caudal sequence. These systems expands upward and becomes more oval in shape as it fills with urine. (Junquiera, 2010) originate from the intermediate mesoderm.  Pronephros o Earliest nephric stage II-D. URETHRA o Rudimentary and non-functional  lumen is also stellate-shaped o Arises from intermediate mesoderm  proximal part is lined by urothelium o Beginning of 4th week, it is represented into groups  distal part transitions into stratified squamous which forms pronephric tubules and ducts epithelium (vestigial structures = non-functional) o protection from the external environment o These groups form vestigial excretory units, o seen in Histo lab slide boxes nephrotomes o End of 4th week, all indications of these system have  In males (3 parts): disappeared o Prostatic urethra:  Mesonephros  Lined by transitional o Functions for a short time during the early fetal epithelium(urothelium) period.  Extends through the prostate gland o 2nd stage of nephric development. o Membranous urethra o It becomes segmented and gives rise to  Short segment that passes through mesonephric tubules and ducts an external sphincter of striated o When tubules appear, they lengthen rapidly muscle and form an S-shaped loop, and acquire a tuft of 16 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System capillaries that will form a glomerulus at their medial extremity. o Around the glomerulus, the tubules form a Bowman’s capsule, and together these structures constitute a renal corpuscle. o Principal excretory organ during embryonic life from the 4th to 8th week of life. o In females, there is COMPLETE degeneration of the mesonephric duct. o In males, the mesonephric duct will persist to become the Wolffian duct.  Metanephros o Forms the permanent kidney o Appears in the 5th week o Metanephros comes from the Metanephrogenic tissue  This tissue originates from the intermediate mesoderm  Gives rise to tubules and parts of the nephron Figure 30. Penetration of ureteric bud into the metanephrogenic o Collecting ducts of the permanent kidney develop tissue. (2018A trans) from the Ureteric bud  A derivative of mesonephric duct REVIEW QUESTIONS  It gives rise to the ureters, renal pelvis, major 1. The lining epithelium of the female urethra near and minor calyces, and collecting ducts the opening into the vestibule is best classified as: o The ureteric bud penetrates the metanephrogenic a) Simple cuboidal epithelium tissue to give rise to the tubules invaginated by tufts b) Stratified squamous non-keratinized of capillaries. This would give become the epithelium glomerulus and the remaining parts of the nephron. c) Pseudostratified columnar epithelium 2. The uteric bud is an outgrowth of which of the following embryonic structure: a) Pronephric b) Mesonephric c) Metanephric 3. What is the shortest part of the male urethra: a) Membranous urethra b) Prostatic urethra c) Spongy urethra 4. The internal urethral sphincter is innervated by which nerves: a) Renal nerve plexus b) Celiac plexus c) Hypogastric plexus 5. The inferior suprarenal artery supplying the adrenal gland is a direct branch of which of the Figure 29. A. Relationship of the intermediate mesoderm of the following arteries? pronephric, mesonephric, and metanephric systems. Note the a) Renal arteries longitudinal collecting duct, formed initially by the pronephros but b) Ovarian arteries later by the mesonephros (Mesonephric duct). B. Excretory tubules c) Testicular arteries of pronephric and mesonephric systems in a 5-wk embryo. (Sadler, Answers: B,B,A,C,A 2012). REFERENCES  Mescher, A.L. (2013). Junqueira’s Basic Histology Text and Atlas 13th ed. McGraw Hill.  Moore, K.L., Dalley, A.F., Agur, A.M.R. (2014). Clinically Oriented Anatomy. 7th edition. Philadelphia: Lippincott Williams & Wilkins.  Netter, F.H..Atlas of Human AnatomySaunders Elsevier.  Sadler, TW (2012). Langman’s Medical Embryology12th ed. Philadelphia, PA: Lippincott Williams & Wilkins 17 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]  4.06 Gross Anatomy and Histology of the Urinary System  Sta. Ana. (2015). Gross Anatomy and Histology of the Urinary System. Lecture. Quezon City.  2018 A & B transcriptions APPENDIX Table 1: Parts if male urethra 18 of 18 Gross Ana and Histo of the Urinary System [De Paz, Delmoro, Dizon, Dorosan, Enriquez]