1-it consist of two kidneys, two ureters, urinary bladder and urethra. capsule removed easily because absence of septa. 2- Each kidney consist [ in longitudinal section ] of outer dark cortex and inner pale medulla divided into two part outer and inner part. Unilobar kidney ( unipyramidal kidney ) ( cat, dog, Horse, small ruminant) renal pelvis Multlobor ( multipyramidal ) kidney ( pig, large ruminant ) calyx miner and calyx major Urinary System Microscopic structure : Medullary ray Renal column

Capsule : It have the Functional unit called (Nephron) There are two types short nephron and long nephron, it consist of : 1.renal corpuscle 2.convoluted & straight of proximal tubule 3.thin segment 4.straight & convoluted distal tubule proximal & distal convoluted tubule line in the cortex and summoned the renal corpuscle. loop of Henle consist of straight part of proximal and distal convoluted tubule thin segmented. urinfereous tubules = Nephron + collecting duct.

renal corpuscle glomerulus Bowman's capsule renal corpuscle vascular pole ( contains afferent and efferent arteriole ) urinary pole. Bowman's. space 1-Endothelium of the Glomerular capillary Filtration Barrier 2- Glomerular basement membrane 3- Glomerular epithelium ( podocytes process ) inter capillary cell, ( Mesangeal cells )

Filtration Barrier: 1.Endothelium of the Glomerular capillary: endothelial cells of the Glomerular capillaries possess a large number of aquaporin – 1 (AQP – 1) water channels that allow the fast movement of water through the epithelium. 2.Glomerular basement membrane (GBM): the cells of the visceral layer of Bowman's capsule. Because of its thickness, the GBM is the principal component of the filtration barrier. 3.Glomerular epithelium (podocytes process) (Bowman's capsule): which the filtration take place.

Proximal convoluted tubules (convoluted and straight) longest segment ( bulled of the cortex ) Has more section More acidophilic pyramidal cell with basal spherical nucleus have brush border intercellular surfaces not dear Thin segment: (thin descending and ascending portion of Helen's loop ) lined by simple squamous epithelium nuclei bulge into the lumen The surface has few short microvilli not visible with light Outer luminal diameter 12 – 15 M

Thin segment capillary 1- nucleus bulge 1- nucleus oval or elongated 2- Epithelial cell is thicken 1 – 2 m 2- pointed end 3- Microvilli little 3- contains blood – 15 m in diameter 4- (7–2) M (8) in diameter Distal convoluted tubule : 1.Fewer sections than proximal convoluted tubules. 2.Lumen is longer because the epithelial is lower. 3.The cells are narrower and there is more cell nuclei than in cross sections of proximal convoluted tubules. 4.No Brush border except out lunge cilium projection in lumen. 5.The cytoplasm is less acidophil. 6.the basal in folding are more. 7.large slimy mitochondria line between the basal cytoplasmic in holding lending to basal striation.

Collecting tubule : They are not, apart of nephron although the nephron join the collecting tubule in the cortex. The collecting duct finally converge into large straight collecting ducts called papillary ducts ( duct of Bellini ) which open onto the apex of papilla the area crib Rosa. there are : a.arched collecting duct. b.straight collecting duct.

Pelvis : expanded proximal end of the ureter that faces are the apex of the renal papilla and is lined with transitional epithelial it rest on loose C.T. propria – sub mucosa, tunica muscularis of 3 layers, inner and outer longitudinal and middle circulation covered with thin adventitia. Blood, Vein and Nerve supply : Some aspects of the blood supply of the kidney have been described in relation to specific functions ( Glomerular filtration, control of blood pressure ) each kidney receives a large branched from the abdominal aorta called the renal artery. The renal artery branches within the renal sinus and sends interlobar branches into the substance of the kidney. The venous flow in the kidney follows a reverse course to arterial flow, peritubular cortical capillaries drain into interlobular veins which drain into renal vein. Medullary vascular network drains into interlobar veins. Peritubular capillaries near the kidney surface and capillaries of the capsule drain into interlobular veins.

The nerve supply from the renal plexus derived from sympathetic division of autonomic nervous system : 1.constriction of the afferent arterioles to the glomeruli reduces the filtration rate and decreases the production of urine. 2.constriction of the efferent arterioles to the glomeruli increases the filtration rate and decreases the production of urine. 3.loss of sympathetic innervation leads to increased urinary out put. Note : the extrinsic nerve supply is note necessary for normal renal function.

Ureter : the ureter leaves the kidney at the hilu and inter the urinary bladder, coursing oblique through the tunica muscularis where it pierces the bladder microscopic structure : The wall of the ureter has three layers 1.Mucosa membrane which lined by 5 – 6 layers of transitional epithelium and thrown into longitudinal folds. ( satellite – shaped lumen in cross section ) 2-Tunics muscularis ( three layers ) 3-Adventitia or serosa

Urinary bladder : ( reservoir of urine ) Histologically it is an expanded ureter. because most of the layers present in the ureter are present in the bladder. The difference is : 1.Urinary bladder has thicker T. muscularis layer 2.presence of a scanty muscularis mucosa Microscopic structure : 1-Transitional epithelium, 2- (3-14) cell layers thickener, 3- loose C.T. lamina propria. The distinguishing feature of the bladder is the inter weaving pattern of the muscle layers which composed of three layers, an inner and outer longitudinal and a middle circular. Urethra : Female urethra : is a short tube extending from the bladder to the external urinary orifice. it's wall has four coats : 1. mucosa 2. sub mucosa 3. muscularis 4. adventitia.

Microscopic structures : Shallow longitudinal folds transitional epithelium near the bladder neck, and gradually changed to stratified squamous near the orifice. Between these two sites are areas of stratified cuboidal or columnar. Male urethra : a.pelvic portion ( from the urinary bladder to the bulb ). b.bulbar portion c.penile portion ( from the end of bulb to external urethral opening ). The entire urethral mucosa is thrown into longitudinal folds which disappears during erection and micturition.