Kidney, Ureters and Bladder Anatomy

• Paired organs responsible for filtering blood to create urine, situated retroperitoneally on either side of the vertebral column.
• Functions include filtering blood to eliminate excess water, salts, and protein metabolism waste, returning nutrients and chemicals to the blood, and maintaining homeostasis through electrolyte balance, blood pressure regulation, and acid-base balance.

Urinary Passages

• Ureters are long muscular tubes, approximately 25-30 cm long, that transport urine from the renal pelvis of the kidneys to the urinary bladder via peristaltic waves.
• The urinary bladder is a hollow viscus with strong muscular walls that temporarily stores urine until voiding and can expand significantly.
• When empty it lies in the lesser pelvis, and when full it can ascend into the abdominal cavity.
• The urethra serves as a passageway for excreting urine from the bladder to the external environment; its length varies by sex.
• Approximately 18-20 cm long in males (also serves as a passage for semen)
• Approximately 4 cm long in females.
• Facilitates micturition (urine voiding).

Functions of the Urinary System

• Excretory Function: Filtration and excretion of metabolic wastes, removes nitrogenous wastes (urea, creatinine) and other metabolic byproducts, and ensures the elimination of toxins and waste products through urine.
• Body Homeostasis Maintenance:
• Acid-Base Balance: Regulates blood pH by excreting hydrogen ions (H+) and reabsorbing bicarbonate (HCO3).
• Fluid Balance: Maintains normal body fluid levels by eliminating excess water when hydration is high and conserving water during dehydration.
• Electrolyte Balance: Adjusts the reabsorption and excretion of essential ions like sodium (Na+), potassium (K+), and calcium (Ca²+).
• Endocrine Function:
• Erythropoietin (EPO): Stimulates the production of red blood cells (erythrocytes) in the bone marrow and is released in response to low oxygen levels in the blood.
• Renin: Plays a role in the Renin-Angiotensin-Aldosterone System (RAAS)
  • Regulates blood pressure by controlling blood volume via increasing vasoconstriction
• Activation of Vitamin D: Converts inactive Vitamin D into calcitriol, which aids in calcium absorption and bone health.
• Reproductive Function: Male urethra has a dual function: a passageway for urine excretion and a conduit for semen transport during ejaculation.

Gross Anatomy of the Kidneys

• Paired, bean-shaped, and ovoid positioned retroperitoneally on the posterior abdominal wall.
• Shape: Lateral surface is convex, while the medial surface is concave, containing the renal hilum for renal vessels, nerves, and the ureter.
• The right kidney is slightly lower than the left due to the liver.
• The kidneys move 2-3 cm vertically during deep breathing.
• Vulnerable to trauma due to their retroperitoneal location.
• Respiratory movement allows palpation of the kidney during a deep breath in thin individuals.

Dimensions of Each Kidney

• Weight: 120-170 g
• Length: 10-12 cm
• Width: 5-6 cm
• Thickness (Anteroposterior): 2.5-3 cm
• Vertebral Level Span T12 to L3 vertebrae in the erect position.

Relations Anterior

• The principal anterior relationship of the kidneys is with abdominal viscera and mesenterie
• Suprarenal glands cap the kidneys superomedially Right kidney capped by right suprarenal gland (pyramidal-shaped) and the left suprarenal gland being crescent-shaped

Relations to the Right Kidney

• Medial Relations: Descending part of the duodenum.
• Lateral Relations: Ascending colon.
• Superior Contact: Right colic flexure and upper 1/3 in contact with the liver.
• Anterior surface covered by peritoneum where relating to the liver and other intraperitoneal organs.
• The area where the kidney contacts the duodenum, suprarenal gland, and colonic structures lacks peritoneum.

Relations to the Left Kidney

• Medial Relations: Tail of the pancreas and the Spleen.
• Superior Contact: Left colic flexure and descending colon.
• The anterior surface relates to intraperitoneal organs, such as the stomach, jejunum, ileum, spleen, and pancreas where the peritoneum is present.
• Areas in contact with the descending colon, suprarenal gland, and colonic flexure lack peritoneal coverage.

Intraperitoneal vs. Retroperitoneal Relations

• Intraperitoneal Organs: Liver, Jejunum, Ileum, Stomach, and Pancreas (partly intraperitoneal).
• Retroperitoneal Organs: Suprarenal glands, Descending duodenum, Descending colon, and Right and left colic flexures.

Posterior Relations of the Kidney

• The kidneys are retroperitoneal organs that primarily rest on the posterior abdominal wall muscles.
• Upper 1/3 of the kidney lies on the arcuate ligament of the diaphragm and the 11th and 12th ribs.
• Lies on the quadratus lumborum muscle (forming a large portion of the kidney's posterior bed) and on the medial (concave) side: related to the psoas major muscle and Lateral (convex) side, associated with the aponeurosis of the transversus abdominis muscle.
• Three major nerves cross diagonally on the posterior surface passing over the psoas muscle: subcostal nerve (12th intercostal nerve) and vessels, iliohypogastric nerve, and ilioinguinal nerve.
• The lumbar vertebral column protrudes into the abdominal cavity, causing the kidneys to be positioned obliquely.
• Superior pole is closer to the midline than the inferior pole.

Key Anatomical Relations of the Kidney

• Surfaces: Anterior (related to abdominal organs) & Posterior (related to muscles, nerves).
• Margins: Medial containing the hilum & Lateral (convex).
• Poles: Superior (near adrenal gland) & Inferior.

Renal Coverings & Clinical Correlation

• The kidneys are enclosed in layers of fascia and fat, serving as protection, support, and insulation.

Layers from Deep to Superficial

• Kidney then Renal Capsule, Perirenal (Perinephric) Fat, Renal Fascia (Gerota's Fascia), and Pararenal (Paranephric) Fat.
• Renal Capsule: Firm, fibrous connective tissue covering the kidney, providing structural support to the renal parenchyma.
• Perirenal (Perinephric) Fat: Fatty tissue immediately outside the renal capsule, extending into the renal sinus and cushioning the renal vessels.
• Renal Fascia (Gerota's Fascia): Membranous condensation of extraperitoneal fascia enclosing the kidney, suprarenal glands, and perinephric fat, blending with the vascular sheath of the abdominal aorta and inferior vena cava.
• Attachments of the Renal Fascia is superiorly to the anterior and posterior layers fuse and connect with the diaphragmatic fascia securing the kidney and suprarenal glands with primarily attached to the diaphragm and laterally fuses with the transversalis fascia and medially and inferioly continues as the sheath for renal vessels, joining the iliac fascia respectively
• Pararenal (Paranephric) Fat: Located external to the renal fascia, derived from extraperitoneal fat, accumulating posterior and posterolateral to the kidney.

Parts of the Kidney

• Ovoid-shaped organs with a convex lateral border and concave medial border where the renal hilum is located.
• Renal Hilum is a deep vertical split in the kidney where the renal sinus lies
• Renal Sinus: A cavity surrounded by perinephric fat containing Renal vessels , Lymphatic vessels and Nerves
• Arrangement of structures at the hilum (anterior to posterior): VAUA: Renal vein Two renal segmental arteries and Renal pelvis/Ureter

Renal Cortex

• Outer region of the kidney, consisting of a continuous band of brownish tissue surrounding the renal medulla.
• Includes Renal Columns (of Bertin) and Medullary Rays

Renal Medulla

• Inner region of the kidney, made up of 6-10 conical-shaped renal pyramids.
• Key Structures of the Medulla Renal Pyramid: Apex: Also known as the renal papilla, where filtrate exits, base that faces cortex and is associated with medullary areas.
• The renal papilla is composed of small perforated openings called Area Cribrosa
• Small perforated openings at the renal papilla, which allows urine passage into the minor calyx

Renal Calyces and Pelvis

• Minor Calyx cups renal papilla to collect urine - several minor calyces merge forming major calyx
• Major Calyx: Formed by the union of 2-3 minor calyces which merge forming the renal pelvis
• Funnel-shaped structure at the superior end of the ureter.
• Urine pathway is through the renal pelvis -> ureter -> bladder -> urethra for excretion

Embryology of the Kidney

• Fetal and Newborn Stage the renal Lobes are outlined on the kidneys surface
• Adult: the lobes fuse resulting in a smooth surface of the kidney

Arterial supply of the Kidneys

• Renal Hilum arrangement is Renal Vein, Renal Artery, Ureter & Segmental Artery (VAUA mnemonic).
• Main arterial supply of the kidneys:
• Originate as branches of the abdominal aorta, at the level of L1-L2 Right passes posterior to the inferior vena cava (IVC) and is longer than the left renal artery which lies slightly higher than the right renal artery
• Each artery divides into five segmental arteries, each supplies different kidney segment which do not connect.

Clinical Correlation

• Partial nephrectomy is a surgical procedure with no significant anastomosis that allows preservation of kidney tissue

Venous drainage of the Kidneys

Venous drainage follows the arterial supply and major veins drain directly into the IVC Left is 3x longer and crosses between the superior mesenteric artery( SMA) to enter the IVC.

• Tributaries from the Left Renal Vein drain the inferior phrenic vein, left suprarenal vein, the left gonadal vein (testicular in males, and the ovarian in females) , and the left ascending Lumbar

Lymphatic Drainage

• Aortic (para-aortic) & Caval (paracaval)

Innervation of the Kidneys

• The nerves are sympathetic & parasympathetic with supply from the abdominopelvic Splanchnic nerves
• Also linked to Celiac, Aorticorenal Ganglion and Plexus
• In direct contact with vasculature, tubules, juxtaglomerular that serve regulation
• Decreases bloodflow and glomerular filtration by acting via: Enhancing tubule and henle function while also stimulating Renin, leading to angiotensin stimulation

Ureters

• Paired muscular tubes
• Retroperitoneal lie
• Length: 25-30 cm
• Thick walled and narrow
• Peristaltic contractions propel urine from the kidneys to the urinary bladder

Course of the Ureters

• Originate at renal hilum
• Runs inferiorly towards the abdomen
• Continues along the pelvis and lateral wall
• Enters the urinary bladder obliquely

Relations

• Superior relations include the funnel shaped like shape to the tubules.
• Inferior relations include relations that are continuous with the bladder

Parts of Ureter

• Includes Renal pelvic, Abdominal/False, Pelvic and terminal Intravesical section
• Abdominal is along Middle aspect of Psoas Major Right lies to the IVC and left side, side Lateral to the Aorta Gonadal Vessels cross over

Pelvic Ureter

Passes over common lilac or beginning of external

• Runs towards the internal lilac arteries by the time it enters it transitions into the bladder
• Has relations to the uteral vessel near the isthmus upon entering the bladder

Mnemonic (Water Under The Bridge)

• Passing over the top causes injury
• Water → Ureter (carries urine)
• Bridge → Uterine vessels (which pass over the ureter)
• Gonadal vessels also act as a bridge over the abdominal ureter

Vas deferens is the male counterpoint to the bladder connection at posterior wall. Precautions should be given that may result its damage

Arterial Supply

• Renal arteries and medial branches are consistent in the midsection anastomies Gonodal arteries and aorta are useful additional routes for abdominal parts Distal parts common and internal with consistent inferior artery on distal

Caution

Arteries will have ascending and sending branches

• Avoid retractions during this period

Venous drainage of the Ureters

• Is Renal and Gonodal

Innervation with nerve Plexuses

• Renal and Aortic are involved
• The hypogastric and the inferior are common

Ureter pain

• Is Felt between T11-L2 segment Pain is felt from loin to the groin region with dilated spasms
• Issues occur in the abdomen, groin and scrotum
• Reason for Referral: Due to similar pain and similar location as the issue.

Lymphatic drainage is regional to ureters

• Common, external, and internal iliac nodes
• Distention, constrictions from ureters.
• Sharp rhythmic, ureter colic

Mnemonic to keep in mind

UPJ at Pelvis brim and Bladder being UP PB

Urinary bladder

• Acts as reservoir
• Strong musculature: Detrusor ability to contract and expand

Position and location

• Shape: tetrahedral when boat shaped Location on Lesser pelvis in adults

Bladder State

• Apex is on Anterosuperior wall and connects through Ligament
• Fundus contains Two ureter orifices in Posterior Border
• The body is between the apex and the orifices
• The base is where the bladder empties into the urethra
• the part in males rest on the prostate

Vesical Trigone

• Is triangular and located in the fundus
• Superior location is in the ureter and the inferior is urethra

Orientation

• Rests on the pelvic floor in Females Males have prostrate and connects through the glads and through The anterior of gland landmark in identification

Ligaments

Lateral with tendons connected in the pelvic

Pubovesical

• Femal: stabilizes pelvic floor
• Male functions but also aids the prostate

Umbilical

• Apex to the urachus

Bloodflow

• Inner Lilac as branches contributes.

Interior Vesical

• Posterior wall with bladder on the end of the inferior

Lilica

• Replaced by arterial Arteries drained into the inferior Veins pass through ligaments

Innervation

• Autonomic innervation that regulates urination
• Sympathetic T11-L2 allows muscles to facilitate filling and retain urine

Pari sympathetic innervation S2-S4

• Allows bladder emptying by contracting and urinating
• Pundal allows voluntary urination

Bladder Damage

• can lead to infections and malignancies.

What Is the Distal End Called

• A muscular passage to conduct from the bladder to the external environment
• In males it also passes semen

Main Male Function

• 18-20 cms ( way longer ) begins to opens opens at at the tips
• Dual Function Excretion + Expel Smen

Spongy Urethra

• Prostatic - Passes through prostrate ducts Ejaculatory are received Crest and sinuses
• Membranous are the diaphragm and surrounded by voluntary control injury
• Spongy (Penile) is the longest portion in a corpus

Neurons

• Arterial depends on the segments with different regions to the same vein.
• Innerveation from Inferior has auto control over penile sensation

Female Functions

• Short 4-6 cm range that has many areas of high function
• In contact with the vaginal wall ( higher infection rates
• No well - defined and surrounded by muscle sphincter

Glandular Function

Mucus and lining and Paraurethral from Glands

Arterial Supply

Internak with Secondary vaginal regions Venous draining is both inner draining, and lymph drains to the lymph nodes Visceral for nerve endings (auto) for sensation

Kidney Histology

• divided into regions : outer renal cortex, and renal medulla, collecting tubules
• outer consists of filtration structures Inner consist of loops if hemline concentration drainage parts. Nephron is structural functional unit of kidney

Corpuscle Parts

• Glomulerous filtration for blood and water
• Capsule is for filtration and cells

Renal tube Functions

• Reabsorbtion loop (65-70%) by absorbing and releasing through diffusion
• Loop Creates balance through gradient Distal creates fine tuning by having specific reulation
• system for modification by draining parts.

Cortex for the Nephrons for filtrate/urine function There's corticol an juxt for short and longer loops

• Hilum is main spot for extraction

• Glomeruli in capsules with vessels on the pole Capsules filter and the outside allow passage / support

Mesangium

• For structure, blood flow regulation, and phagocytosis + cytokine relations

Tubules

• Convoluted tubule is an long kidney tubule

Henle

• Has hairloops involved in maintain fluid volume Thick and thin sides, Loops make hypertonic as important function

Tubules ( DCT )

• Are shorted and help perform acid - vase with low absorption and high regulation Help with kidneys function with sensors.

Collecting system

• Has urine receptipon Function: regulates water, determine concenreation Also has 3d pathways to urine transfer
• The renal pelvis
• Cortex has all the nephron units
• The Cortex has pyramids for loops and collecting
• The medulla can then get rid in this part.

Kidney supply and veins for draining.

• arterioles supply glomerouls loops for blood filtration. Venules has reverse with the aorta Flow is in the capsular in tube. Passahe loops for modification
• ducts as delivery

The Passages

Urine is passed toward bladder.

• Ureter is lined in a specialized state to adapt

Walls and Layers

• Mucosa, muscularis for urine transport and protection. Three layer of muscosa that transport and connect
• The upper is smooth, while the lower contains three other muscles. Outer is to assist other support. The bladder is same but stronger with muscle. This has transctions for structural similiaties

Male Urethreas

• Are longer with change that helps transition The uterus has similar changes, but it's shorter.

Embryo Parts

• The Kidneys have three sections developing in stages to move :
• Pronephos ( rudimetr )
• Mesonephros (Partially functional)
• Metanephos (permanent kidney)

Stages of the Kidney

• Begining of 4th week till it dissipates, and disappears to allow connections tubules mesonnephrite. The function is in the later months where structures are derived in functions. Tissues cause shapes and elongation to the flow of sections allowing urine with the same kidney development. There has to be bud which gives all parts needed to allow all systems functions. Blasema allows the systems too with cap Shape formation allows creation for all functions needed and specified with all the tissues functions used.

Test your knowledge of the kidney, ureters and bladder. This quiz covers renal blood supply, nerve supply, function, and anatomical features of the urinary system. Review the key structures and mechanisms involved in urine transport and bladder function.