Rut Beyene P3 Anatomy of the Kidneys and Bladder

URINARY SYSTEM ORGANS   Kidneys (2)   Ureters (2)   Urinary bladder   Urethra

KIDNEY ANATOMY   Retroperitoneal   Partially protected by the 11 th and 12 th ribs   Right kidney slightly lower due to liver

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KIDNEY ANATOMY   Protected by three connective tissue layers Renal fascia Attaches to abdominal wall Adipose capsule Fat cushioning kidney Renal capsule Fibrous sac Protects from trauma and infection

KIDNEY ANATOMY Gross anatomy Renal sinus Renal parenchyma Hilum

KIDNEY ANATOMY Renal sinus Surrounded by renal parenchyma Contains blood & lymph vessels, nerves, urine-collecting structures

KIDNEY KIDNEY ANATOMY Renal parenchyma Glandular tissue Forms urine Two zones Outer cortex Inner medulla

KIDNEY ANATOMY Renal Flow Renal columns divide medulla into 6 – 10 renal pyramids Renal columns divide medulla into 6 – 10 renal pyramids The point of the pyramid is the renal papilla The point of the pyramid is the renal papilla Papilla is attached to the minor calyx Papilla is attached to the minor calyx

KIDNEY ANATOMY Renal Flow 2 – 3 minor calices  Major calyx 2 – 3 minor calices  Major calyx 2 – 3 major calices  Renal pelvis 2 – 3 major calices  Renal pelvis Renal pelvis  Ureter Renal pelvis  Ureter Ureter  Bladder Ureter  Bladder Bladder  Urethra Bladder  Urethra

Kidney Anatomy Renal Vasculature   Blood is supplied by the renal artery   Kidney receives about 21% of cardiac output

Nephron   The functional unit of a kidney Filtration Tubular reabsorption Tubular secretion   ~1 million nephrons per kidney

Nephron   The nephron is partly in the renal cortex and partly in the renal medulla   Contains the following structures Afferent/efferent arterioles Glomerulus Glomerular (Bowman’s) capsule Renal tubule

Nephron Renal arterioles   Afferent arterioles bring in unfiltered blood into the kidney (renal corpuscle)   Efferent arterioles take filtered blood back into the body

Nephron Renal corpuscle   Glomerulus enclosed in two-layered glomerular capsule “Bowman’s capsule”   Fluid filters from glomerular capillaries “Glomerular filtrate”   Fluid collects in capsular space   Fluid flows into renal tubule

Nephron Glomerular filtration   Filtration membrane Fenestrated endothelium of capillaries Basement membrane of glomerulus Slit membrane between “feet” of podocytes

Nephron Renal tubule   Leads from glomerular capsule   Ends at tip of medullary pyramid   ~3 cm long   Four major regions Proximal convoluted tubule Nephron loop (loop of Henle) Distal convoluted tubule Collecting duct

Renal Tubule Vasculature of tubule   Reclaim filtrate from renal tubule   Proximal and distal convoluted tubules Peritubular capillaries   Loop of Henle Vasa recta Vasa recta

Vasa Recta

Renal Tubule Proximal convoluted tubule (PCT)   Arises from glomerular capsule   Longest, most coiled region   Prominent microvilli Function in absorption

Renal Tubule Nephron loop (Loop of Henle)   “U” – shaped, distal to PCT   Descending and ascending limbs   Thick segments Active transport of salts High metabolism, many mitochondria   Thin segments Permeable to water Low metabolism

Renal Tubule Distal convoluted tubule (DCT)   Coiled, distal to nephron loop   Shorter than PCT   Less coiled than PCT   Very few microvilli   Contacts afferent and efferent arterioles (regulation imparted)

Renal Tubules Collecting duct   DCTs of several nephrons empty into a collecting duct   Several collecting ducts merge into papillary duct   Drain into minor calyx

Juxtaglomerular Apparatus (JGA)  A group of cells found in the nephron which control renal function  Have three components Macula densa Macula densa Granular cells Granular cells Mesangial cells Mesangial cells

JGA Cells  Macula densa Chemoreceptor cells, detect sodium chloride Chemoreceptor cells, detect sodium chloride Found on the DCT Found on the DCT  Granular cells Mechanoreceptor cells, detect pressure change Mechanoreceptor cells, detect pressure change Found on afferent arterioles Found on afferent arterioles  Mesangial cells Relay messages between macula densa and granular cells Relay messages between macula densa and granular cells

The Ureters  The ureters are muscular tubes leading from the renal pelvis to the lower bladder.

The Urinary Bladder  A muscular sac on the floor of the pelvic cavity.  Contains the urine formed by the kidney.  Highly distensible and expands superiorly.

Bladder Anatomy   CAPACITY: about 300 ml with a maximum capacity of 500 ml Distended bladder is circular in shape Bulges upward into abdominal cavity

Distended Empty

Bladder Anatomy The openings of the two ureters and the urethra mark a triangular area called the trigone on the bladder floor.

Bladder Muscles  Internal urethral sphincter Round muscle that is under involuntary control Round muscle that is under involuntary control  External urethral sphincter Round muscle that is under voluntary control Round muscle that is under voluntary control  Detrusor Muscle The muscle that surrounds the bladder and aids in micturition. The muscle that surrounds the bladder and aids in micturition.

The Urethra  Conveys urine form the urinary bladder to the outside of the body.  Male ~18 cm long ~18 cm long  Females 3-4 cm long, puts women at greater risk of urinary tract infections 3-4 cm long, puts women at greater risk of urinary tract infections

Urothelium  Transitional epithelium that can contract and expand to accommodate for organ size shift.