Urinary System PDF

THE URINARY SYSTEM  URINARY SYSTEM The urinary system consists of: Two kidneys Two ureters One urinary bladder One urethra  STRUCTURE OF KIDNEY Consists of:  Stroma  Parenchyma  Stroma of the kidney is represented by a dense fibrou...

THE URINARY SYSTEM  URINARY SYSTEM The urinary system consists of: Two kidneys Two ureters One urinary bladder One urethra  STRUCTURE OF KIDNEY Consists of:  Stroma  Parenchyma  Stroma of the kidney is represented by a dense fibrous CT capsule, formed mainly of many reticular fibers and few collagenous bundles.  The Parenchyma of the kidney is formed of uriniferous tubules  KIDNEY Renal tissue is divided into an outer cortex and an inner medulla. The cortex has a brown red color and granular appearance due to presence of Malpighian renal corpuscles The medulla is light grey in color and it consists up to 18 medullary pyramids The cortex occupies the spaces between the bases of the pyramids and the kidney capsule  THE KIDNEY LOBULES Each kidney is formed of up to 18 lobes. Each lobe consists of lobules. Each lobules is demarcated by two interlobular arteries.  KIDNEY Uriniferous tubules Formed of: A- Nephrons Which are active secretary parts of uriniferous tubules(Produces urine) B- Collecting tubules Which are excretory parts of uriniferous tubules(Concentrates urine and conveys it to the calyces).  THE NEPHRON The nephron is structural and functional unit of the kidney.  Each nephron is about 30-40mm long  Each kidney contains 1-1.5 millions of nephrons. Each nephron is formed of: 1- Malpighian renal corpuscle 2- Proximal convoluted tubules 3- Distal convoluted tubules 4- Loop of Henle NEPHRON STRUCTURE AND FUNCTION  THE MALPIGHIAN (RENAL CORPUSCLE) They are rounded bodies, present mainly in the cortex of the kidney. Each Malpighian corpuscle consists of: Renal Glomerulus Bowman’s capsule Function: Filtration of blood Renal Glomerulus consist of:  Afferent arteriole(enters). Bed of Fenestrated blood capillaries (glomerulus ). Efferent arteriole(leaves ).  Mesangial cells(phagocytic and contractile cells).  BOWMAN’S CAPSULES Double-walled capsule surround the glomerular blood capillaries Formed of two layer of epithelium: An internal or visceral layer which is adherent to the glomerular blood capillaries (line with podocytes cells) An external or parietal layer of Bowman’s capsule which is formed of simple squamous epithelium Two layer are separate by a space which receive the glomerular filtrate, known as capsular or Bowman’s space. RENAL CORPUSCLE  THE PROXIMAL CONVOLUTED TUBULES It is connected of one end with renal corpuscle and with loop of Henle at its other end, lined with simple cubical cells Function:  Reabsorption of sodium, chloride and phosphate Active absorption of glucose, amino acid and plasma proteins of low molecular weight Excretion of creatinine, iodine and certain drugs  DISTAL CONVOLUTED TUBULES It is shorter in length than proximal tubules, lined with simple cubical epithelium Function: Reabsorption of water (controlled by anti diuretic hormone) Reabsorption of sodium (controlled by aldosterone hormone) Excretion of sodium and potassium (controlled by Atrial Natriuretic factor “ANF”) PROXIMAL AND DISTAL CONVOLUTED TUBULES  THE LOOP OF HENLE It is U-shaped tube, which connects the proximal and distal convoluted tubules of the nephron. There are two type of Henle’s loop: Nephrone with long Henle’s loop (juxta-medullary nephron) Nephrone with short Henle’s loop: (cortex).  THE LOOP OF HENLE Formed of: Thick descending portion of Henle’s loop, it is continuation of proximal tubules, lined by simple cubical cells. A very thin descending portion of Henle’s loop, lined with simlpe squamous epithelium A very thin ascending portion of Henle’s loop, line with simple squamous cells A thick ascending portion of Henle’s loop lined with simple cubical cells.  THE COLLECTING TUBULES The formed urine by the nephrons is collected into different collecting tubules, lined by simple cubical epithelium. They reabsorb water (ADH) About 6 to 8 collecting tubules open into a wide duct called duct of Bellini which lined with simple columnar epithelium.  THE URINARY PASSAGES Urine is collected through minor and major calyces, renal pelvis of the ureter, urinary bladder and urethra Each wall of these passage are similar in their structure, formed of: Mucosa (Transitional epithelium resting on CT corium) Musculosa (Smooth muscles) Adventitia (Areolar CT)  THE URETER & URETHRA Ureter Female Urethra Male Urethra URINARY BLADDER HISTOLOGY  URINARY SYSTEM FUNCTIONS Regulate the fluid and electrolyte balance of the body Form renin hormone (regulation of electrolyte balance and regulation of blood pressure) Secrete Erythropoietin (stimulate development of blood cells) Secrete Medullipin hormone (control blood pressure)