Xue Zhou Department of Histology & Embryology, Sichuan University Urinary System 泌尿系统 Xue Zhou Department of Histology & Embryology, Sichuan University

Function 1. Excretion metabolic waste products 2. Maintaining the balance of fluid and electrolyte 3. Secretion of some substances

Composition Kidney----main organ Ureter Excretory ducts Urinary bladder Urethra

     Kidney 肾 Structure bean shaped Nephron---function unit Parenchyma Collecting tubule Interstitial tissue: a little loose connective tissue

Renal corpuscle Nephron Renal tubule Uriniferous tubule minor calyx major calyx renal pelvis ureter medullary ray cortical labryinth renal column renal pyramid (Medulla) renal papilla cortex Cortex Nephron Renal corpuscle Renal tubule Collecting tubule Uriniferous tubule

// The structural & functional unit; Nephron 肾单位 // The structural & functional unit; // Include renal corpuscle, proximal tubule, thin segment , distal tubule; // Produce urine. Proximal straight tubule Henle’s loop Thin segment Distal straight tubule

Structure and function of each segment ① Renal corpuscle 肾小球 Function: filtration of blood plasma to form primary urine.

Structure spherical body Renal glomerulus Renal capsule Vascular pole Urinary pole

Renal corpuscle, HE

Renal glomerulus, SEM

A. Renal glomerulus 肾血管球 √afferent arteriole √efferent arteriole Which one should be thicker? Why? √capillary ----- which type? fenestrated capillary

Fenestrated capillary & Podocytes

B. Renal capsule( a double layered capsule) 肾小囊 ·Parietal layer 壁层: simple squamous epi connect with proximal tubule ·Visceral layer 脏层: podocytes（足细胞）, primary & secondary process, filtration slit

Fenestrated capillary & Podocytes

Fenestrated capillary, TEM

Filtration barrier, TEM

Filtration barrier 滤过屏障 // The structure separate the cap blood from the capsular space. // It consists of fenestrated endothelial cell, basement membrane & filtration slit membrane. // Filtrate blood plasma to form primary urine.

slit B.M Endo. water cation glucose anion 白蛋白 protein

Primary urine waste products 180L/day water electrolytes nutrients: glucose, amino acids… Primary urine waste products 180L/day water electrolytes A lot of nutrients, water, electrolytes will be reabsorbed by following segments.

② Proximal tubule 近端小管 the largest, longest segment of nephron Function: reabsorption --- 85%H2O, NaCl, all G, AA, proteins excretion--- H+, NH4+…  

Proximal convoluted tubule

Proximal convoluted tubule, EM

simple cuboidal epi with classical structure of reabsorption.  Proximal convoluted tubule 近曲小管: simple cuboidal epi with classical structure of reabsorption. EM LM Free surface microvill,tubular pits brush border Lateral margin lateral process unclear border Basal end infolding,mitochondria basal striations All above increase the surface of cell greatly,permit reabsorbing rapidly from tubule lumen and giving away reabsorbing substances to interstitial tissue quickly.

③ Thin segment 细段 Small sized tubule line with simple squamous epithelium. Function: urine concentration by it’s thin wall and hyperosmat of medullary interstitial tissue.

④ Distal tubule 远端小管: Simple cuboidal epithelium. This segment is thinner and shorter than proximal tubule. Function: In the influence of aldosteron(醛固酮) regulate the acid-base equilibrium of body: reabsorption Na+, Cl- and water; excretion K+, H+, NH4+ .

⑤ Collecting tubule 集合小管 Simple cuboidal or columnar epithelium. LM: lumen--- largest cytoplasm--- lightest cell border--- clearest Function: collecting urine of nephron, regulating the concentration of urine as distal tubule.

Juxtaglomerular apparatus 球旁复合体

*Modified smooth muscle cells in the wall of afferent arteriole. ①Juxtaglomerular cell 球旁细胞 *Modified smooth muscle cells in the wall of afferent arteriole. *Large and pale epitheoid cells *Secretion rennin(肾素) into blood for regulation the blood pressure and the function of distal & collecting tubule.

②Macula densa 致密斑 *The epithelium of distal tubule become columnar and form a elliptic spot. *Sense the urine Na+ concentration in lumen & influence the function of Juxtaglomerular cell.

③Extraglomerular mesangial cell 球外系膜细胞 A group of cells, lying between the macula densa & afferent, efferent arterioles. The function is not well understood.

I. The Development of Urinary System nephrotome,nephrogenic cord urogenital sinus pronephros mesonephros urinary bladder and urethra metanephros (epithelium) (permanent kidney)

The Metanephros 5th week caudal to the mesonephros permanent functional ureteric bud two sources metanephric mesoderm

mesonephric duct metanephric mesoderm ureteric bud metanephric tubules ureter, renal tubules renal pelvis, major & minor calyces, collecting tubules one end another end communicate invaginated by capillaries collecting tubule nephron

Horse-shoe Kidney Ectopic Kidney

Ectopic Kidney

Horse-shoe kidney

Polycystic kidney

Polycystic kidney

Double Ureters

Double Ureters

Double ureters