1. Urinary System

2. Urinary System: Overview

3. Kidneys: Anatomical Location
The kidneys lie in the posterior surface of the abdomen, on either side of the vertebral column between the levels of vertebrae T12 and L3.
The kidneys are retroperitoneal organs, meaning they are located outside (behind) the peritoneal cavity.
The right kidney lies typically lower than the left kidney because of the position of the liver.

4. Retroperitoneal organs (labeled d to i)
Diaphragm
Esophagus
Spleen
Left kidney
Pancreas
Ureters
Common Iliac artery & vein
Duodenum
Right kidney b a c i d h e g f

5. Kidneys: Location

6. Kidneys: External Aspect
Kidneys are bean shaped organs with their long axis parallel to the body axis.
On the superior pole of each kidney an adrenal gland is sitting.
The hilum, a prominent medial indentation is the point of entry for the renal artery and renal nerves, and the point of exit for the renal vein and the ureter.

7. Kidneys: Supporting Structures
Each kidney is secured and protected by three concentric layers of connective tissue:
The renal fascia, the outer dense fibrous layer, anchors the kidney to the abdominal wall.
The adipose capsule, a mass of fat tissue, covers and cushions each kidney.
The renal capsule, al layer of collagen fibers, covers the outer surface of the organ itself and internally delineates a cavity named renal sinus.

8. Kidney_Internal antomy
Segmental
artery

9. Kidney Internal anatomy
Renal capsule
Minor calyces
Renal cortex
Renal pyramid
Renal papillae
Ureter
Renal pelvis
Major calyx
Renal medulla B I H G C D F E

10. Kidneys: Internal Structure
The kidney has an outer cortex and an inner medulla
The renal cortex is the reddish brown superficial portion in contact with the fibrous capsule.
The renal medulla is the inner area consisting of 6 to 18 conical structures called renal pyramids whose bases are adjacent to the cortex and whose tips, called renal papillae project deep into the renal sinus.
Adjacent renal pyramids are separated by bands of cortical tissue called renal columns.
A renal lobe consists of a renal pyramid, the overlying area of renal cortex and the adjacent renal columns.

11. Kidney: Internal Structure (cont.)
Ducts within each renal papilla discharge urine into a cup-shaped drain called minor calyx.
Four or five minor calyces merge to form a major calyx.
Two or three major calyces combine to form the funnel shaped renal pelvis that fills most of the renal sinus and connects to the ureter, a cylindrical tube that drains each kidney toward the urinary bladder.

12. Nephrons: The Filtrating Units
The kidney functional filtrating unit is a microscopic, tubular structure, called nephron
Each kidney has roughly 1,250,000 nephrons, with a combined length of tubular structures of about 145 km (85 miles).
Around 85% of all nephrons are cortical nephrons, located almost totally in the renal cortex.
The remaining 15% of nephrons, have longer nephron loops that extend deep into the medulla, they are called juxtamedullary nephrons

13. Renal Pyramid & Nephrons

14. Renal Corpuscle G E F Proximal convoluted tubule
Glomerular (Bowman’s) capsule
Capsular (glomerular) space
Glomerulus
Afferent arteriole
Efferent arteriole
Distal convoluted tubule
Podocytes H D B C A

15. Nephron: Structure Each nephron consists of two regions:
A renal corpuscle and a renal tubule
The renal corpuscle consists of a glomerular capsule (Bowman’s capsule) that houses a tangled capillary network called the glomerulus.
An afferent arteriole brings blood to the glomerulus; as this blood filtrates through the numerous pores in the capillary wall, materials are forced out of the blood and into the capsular space in the Bowman’s capsule.
The artery emerging from the glomerulus is the efferent arteriole

16. Nephron & its associated blood vessels
Arcuate artey & vein
Renal corpuscle
Distal convoluted tubule
Cortical arteriole
Renal glomerulus
Proximal convoluted tubule
Descending limb of nephron loop
Nephron loop
Ascending limb of nephron loop
Collecting duct

17. Nephron: Structure (cont.-)
The renal corpuscle empties its filtrate into the renal tubule, whose first segment is called the proximal convoluted tubule.
The following tubular segment is the loop of Henle, whose most proximal segment, the descending limb extends deep into the renal medulla, then returning toward the cortex as the ascending limb.
The ascending limb leads to a second twisted tube, called the distal convoluted tubule that empties into a collecting duct.
The collecting duct collects filtrate from multiple nephrons, it joins another collecting ducts that drain into a papillary duct at the tip of a renal pyramid. There are 25 to 35 papillary ducts per renal pyramid

18. Juxtaglomerular Capsule

19. The Juxtaglomerular Complex
At its superior end, the ascending limb of the loop of Henle twists toward the renal corpuscle, so the first portion of the distal convoluted tubule makes contact with the afferent arteriole.
This region is called the macula densa, its cells closely associate with smooth muscle fibers in the wall of the afferent arteriole, these being called juxtaglomerular cells.
Together, the macula densa and the juxtaglomerular cells form the juxtaglomerular complex, an endocrine structure that secretes:
1. The hormone erythropoietin, an activator of the red bone marrow to produce RBCs
2. The enzyme renin, an inductor of a potent response, that increases blood pressure. (renin-angiotensin system)

20. Nephron: Functional Anatomy

21. Urine Production
Glomerulus: Filtration produces a fluid that has the same composition of the plasma, except it does not contain proteins
Proximal Convoluted Tubule and Descending Limb of the Loop of Henle: Ions and organic substrates are removed out of the filtrate returning to the blood; some water is also removed by osmosis.
Ascending Limb of the Loop of Henle: Impermeable to water, its tubular cells actively transport Na+ and Cl, water and urea mostly remain in the passing filtrate.
Distal Convoluted Tubule: Ions, acid radicals, drugs and nitrogenous toxins are removed, mainly by active transport (reabsorption/secretion), water, sodium, calcium, are reabsorbed under hormonal mediation (ADH, Aldosterone, Calcitriol)
Collecting Ducts: Final adjustments in the volume and osmotic concentration occur here, (reabsorption/secretion of Na+, K+, H+ Bicarbonate ions and Water). Beyond this point the fluid has the same composition of the excreted urine.

22. Ureters
Ureters are paired muscular tubes, around 30 cm long each. They descend through the retro-peritoneum connecting the renal pelvis to the urinary bladder.
The wall of each ureter consists of an inner mucosa, a middle smooth muscular layer and an outer connective tissue layer.
Peristaltic contractions help in moving the urine downward toward the bladder
The ureters penetrate the postero-inferior wall of the urinary bladder at an oblique angle, without entering the peritoneal cavity; the ureteral openings are slit-like, what prevents urine backflow toward the ureter when the urinary bladder contracts during micturition

23. IV Urogram

24. The Urinary Bladder
A hollow muscular organ that functions as a reservoir to store urine.
Its dimensions vary depending on its distension; a full urinary bladder can contain as much as a liter of urine.
The internal mucosa lining the urinary bladder is a transitional epithelium; it forms folds or rugae that disappear as the bladder fills and distends.

25. Histology of the Urethra
In both sexes , where the urethra passes through the urogenital diaphragm, a circular band of skeletal muscle forms the external urinary sphincter
It is under voluntary control via the perineal branch of the pudendal nerve; it has a resting tone and must be voluntarily relaxed to allow urination.
In the male urethra, mucin-secreting cells, located in the epithelial pockets lubricate and neutralize the pH of the urine, protecting the sperm cells.

26. Male Low Urinary Tract Urinary bladder
Location of internal urinary sphincter
Prostatic urethra
D) Membranous urethra &
location of external urinary
sphincter in urogenital
diaphragm
Spongy (penile) urethra
F) External urethral orifice B A C D E F

27. Female Low Urinary Tract
Urinary bladder
Internal urethral
orifice, around it,
internal urinary
sphincter.
Membranous urethra,
around it, external
urinary sphincter in
urogenital diaphragm.
D) External urethral orifice on vulvar vestibule. A B C D

28. Ureterolithiasis and Hydronephrosis

29. Lithotripsy
Ultrasound waves are used to crush/fragment impacted kidney stones so they are then eliminated as “sand”, suspended in urine.