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09 urinary system
The urinary system regulates blood composition and excretes waste through the kidneys, ureters, bladder and urethra. The kidneys filter blood to form urine and regulate electrolyte and fluid levels. Urine passes from the kidneys through the ureters to the bladder, where it is temporarily stored until urination. During urination, urine exits the body through the urethra under control of sphincter muscles. The urinary system helps maintain homeostasis by regulating water balance and removing toxins and wastes from the bloodstream.
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09 urinary system
- 1. URINARY SYSTEM • ONEOF THE SYSTEM THAT CONTRIBUTES HEMOSTASIS • THIS SYSTEM REGULATES BLOOD PLASMA COMPOSTION THROUGH CONTROLLED EXCRETION OF ORGANIC WASTES, SALTS & WATER
- 2. COMPONENTS OF URINARY SYSTEM •2 kidneys, which secrete urine • 2 ureters, which convey the urine from the kidneys to • urinary bladder where urine collects and is temporarily stored • 1 urethra through which the urine is discharged from the urinary bladder to the exterior.
- 4. KIDNEYS • Paired, reddish,bean shaped organ • Lies on posterior abdominal wall one on each side of vertebral column • Right kidney is slightly lower than left • Each-10-12 cm long, 5-7 cm wide, 3 cm thick weighs about 1300150 gm
- 5. External anatomy ofkidneys • Renal Hilum- fissure • 3 layers of tissue surrounds 1. Renal capsule- immermost, smooth transparent sheet of dense irregular tissue, continuous with outer layer of ureters. 2. Adipose capsule- mass of adipose tissue, surrounding renal capsule. It holds it firmly in place within abdominal cavity 3. Renal Fascia -outer, thin layer of dense irregular c.t. It anchors kidneys to surrounding structures & to abdominal wall
- 6. Internal Anatomy ofKidney
- 7. RENAL CORTEX -Superficial, smooth, reddisharea -extend from renal capsule to bases of renal pyramid -divided into outer cortical zone & inner juxtamedullary zone -portions that extend bet. Renal pyramids called renal column RENAL MEDULLA -Deep, Reddish Brown Region -Consists Of 8-12 Cone Shaped Renal Pyramid -Apex of pyramid-papilla • Renal Lobe: Renal cortex, renal pyramid & one-half of each adjacent renal column
- 8. • The renalpelvis is the funnel-shaped structure which acts as a receptacle for the urine formed by the kidney. It has a number of distal branches called calyces, each of which surrounds the apex of a renal pyramid • Urine formed in the kidney passes through a papilla at the apex of a pyramid into a minor calyx, then into a major calyx before passing through the pelvis into the ureter.
- 9. Microscopic Structure ofKidneys The kidney is composed of about 1 million functional units, the nephrons, and a smaller number of collecting tubules.
- 10. NEPHRON RENAL CORPUSCLE RENALTUBULE Glomerulus Glomerular Proximal (Capillary (Bowman’s Convoluted Network) Capsule) Tubule Loop of Henle Distal Convoluted Tubule
- 11. Cortical Nephrons (80-85%) -Renal corpuscleslie in outer portion of cortex -have short loop of Henle & lie mainly in cortex -Ascending limb of loop of Henle has only thick ascending limb Juxtamedullary Nephrons (15-20%) -Renal corpuscles lie in the deep cortex, near to medulla -have long loop of Henle that extend into deepest region of medulla -Ascending loop of Henle has 2 portions: Thin ascending limb & Thick ascending limb
- 12. Histology of Nephron •Glomerular Capsule: -Inner visceral layer of modified simple squamous epithelium-Podocytes- a cell with thousands foot like projections wrap endothelial cells of glomerulus. -Outer parietal layer of simple squamous epithelium -Bowman’s / Capsular space: space between two layers, Fluid filtered from glomerular capillaries enters this space
- 14. • Proximal ConvolutedTubule-Simple cuboidal epithelial cells with microvillus • Loop of Henle: Descending limb & thin ascending limb-Simple Squamous Epithelial cells • Loop of Henle: Thick ascending limb- Simple Cuboidal to Columnar epithelial cells • Most of Distal convoluted tubule- Simple Cuboidal epithelial Cells • Last part of DCT & all of collecting duct- Simple Cuboidal epithelial cells
- 15. RENAL PHYSIOLOGY Formation ofUrine- Nephrons & collecting ducts perform 3 basic processes to produce urine 1. Golmerular Filtration Renal Capsule 2. Tubular Reabsorption Renal tubule & 3. Tubular Secretion Collecting duct For any substance ‘S’ excretion rate= Filtration rate of ‘S’ – Reabsorption rate of ‘S’ + Secretion rate of ‘S’
- 16. Golmerular Filtration On average, daily volume of glomerular filtrate is 150 liters in female, 180 liters in male GFR- the volume of fluid filtered in all Bowmann Capsules of both kidneys each minute is GFR GFR – 125 ml / min in male 105 ml / min in female
- 17. Tubular Reabsorption • Aprocess f returning of most of filtered water & solutes to bloodstream • About 99% of filtered water is reabsorbed • Proximal convoluted tubule makes largest contribution • Solutes are reabsorbed by both active & passive processes • It includes glucose, amino acids, urea & ions –Na+ ,K+ ,Ca++ ,Cl- ,HCO3 - , HPO4 --
- 18. • Some solutesare completely reabsorbed, unless they are present in blood in excessive amount. E.g. Glucose • Reabsorption of some solutes is regulated by hormones: -Parathormone & Calcitonin- Calcium & Phosphate -ADH- Water -Aldosterone - Na+ , K+ • Urea & uric acid are reabsorbed only to slight extent • Creatinine is not absorbed at all
- 19. Tubular Secretion • Itis process of transfer of substances from blood & tubule cells into tubular fluid. • Process takes place in proximal convoluted tubule & collecting duct only • Secreted substances include H+ , K+ ,NH4 + , Creatinine & certain drugs
- 20. Kidney controls urineoutput & maintain water balance by 3 ways ANTI-DIURETIC HORMONE Increased blood osmotic pressure Osmoreceptors in hypothalamus Stimulation of post.Pituitary Release of ADH promotes Reabsorption of water Reduces loss of water in urine (reduced blood osmotic pressure)
- 21. ALDOSTERONE Decrease in bloodvolume & pressure Secretion of Renin by Kidneys Angiotensinogen Angiotensin I Angiotensin II Stimulation of Adrenal Cortex release of aldosterone Promotes urinary reabsorption of Na+ & Cl- ; simultaneously increases water reabsorption via osmosis Reduces loss of water in urine
- 22. ATRIAL NATRIURETIC PEPTIDE Increasedblood volume Secretion of ANP by atria of heart Reduces Reabsorption of Na+ , Cl- by Kidneys Promotes natriuresis, increased urinary excretion of Na+ , Cl- Increases loss of water in urine via osmosis
- 23. Composition of Urine: Water-96%,Urea-2% & remaining solutes- 2% which includes uric acid, Creatinine, sodium, potassium, chlorides, phosphates, sulphates, oxalates, ammonia. Abnormal constituents of Urine: Albumin- permeability of glomerulus Glucose- Dibetes Ketone bodies-ketoneurea-Diabetes, starvation, anorexia RBC- hematuria Microbes- infection of Urinary Tract
- 24. Kidney Functions • Regulationof blood ionic composition: Kidneys help regulate blood level of several ions, most importantly Na+ , Ca++ , Cl- & PO4 — • Regulation of blood pH: Kidneys excrete variable amount oh H+ ions into urine and conserve HCO3 ions, which are buffer for H+ in blood • Regulation of blood volume: Kidneys adjust volume by conserving or eliminating water in urine
- 25. • Regulation ofblood pressure: Kidneys help regulate blood pressure by secreting enzyme renin, which activates RAA pathway • Maintenance of blood osmolarity: By separately regulating loss of solutes in the urine, kidneys maintain relatively constant blood osmolarity close to 300 mOsm/L • Production of hormones: Calcitriol, the active form of vit. D, helps regulate calcium and Erythropoetin stimulates production of red blood cells.
- 26. • Regulation ofblood glucose level: Like liver, kidneys can use amino acid glutamine in gluconeogenesis. It release glucose into blood to help maintain normal blood glucose level • Excretion of wastes & foreign substances: By forming urine, kidneys excrete wastes- substances that have no useful function in body. These include ammonia, urea, bilirubin, creatinine & uric acid.Foreign substances such as metabolites of drugs and environmental toxins are excreted
- 27. URETERS • Each ureteris continuation of renal pelvis • 25-30 cm long, • diameter of about 3 mm • At the base of urinary Bladder, ureters curve medially & pass obliquely through wall of bladder
- 28. As urinary bladderfills with urine, pressure within it compresses oblique openings prevents back flow -Consists of 3 layers of tissue: • an outer covering of fibrous tissue, continuous with the fibrous capsule of the kidney • a middle muscular layer consisting of inner longitudinal & outer circular smooth muscle fibers, and an additional outer longitudinal layer in the lower third • an inner layer, the mucosa, lined with transitional Epithelium Function-to transport urine from kidneys to urinary bladder
- 29. URINARY BLADDER • Hollow,distensible, muscular, pear- shaped organ, situated in pelvic cavity In males, directly anterior to rectum In females, anterior to vagina & inferior to uterus
- 30. • The bladderwall is composed of three layers: • the outer layer of loose connective tissue, containing blood and lymphatic vessels and nerves, covered on the upper surface by the peritoneum • the middle layer, Muscularis (detrusor muscle) -consisting of 3 layers of smooth muscle fibers : inner Longitudinal, middle Circular & outer Longitudinal • the mucosa, lined with transitional epithelium
- 31. The three orificesin the bladder wall form a triangle or trigone. The upper two orifices on the posterior wall are the openings of the ureters. The lower orifice is the point of origin of the urethra. When the bladder is empty the inner lining is arranged in folds, or rugae, and these gradually disappear as the bladder fills.
- 32. • The bladderis distensible but when it contains 300 to 400 ml the awareness of the desire to urinate is initiated. The total capacity is rarely more than about600 ml. • Where the urethra commences is a thickening of the smooth muscle layer forming the internal urethral sphincter. This sphincter is not under voluntary control. Functions: 1.Reservoir of Urine 2.Micturition
- 33. MICTURITION In developednervous system, stimulation of Spinal reflex but sensory impulse pass upwards to cerebral cortex. There is perception of desire of Micturition By conscious effort, reflex contraction of the bladder wall and relaxation of the internal sphincter can be inhibited for a limited period of time
- 34. URETHRA • A Canal/tube starting from internal urethral orifice in urinary bladder to exterior of body as external urethral orifice • Female Urethra: length- 4cm, directed obliquely, inferiorly & anteriorly External urethral orifice located between clitoris & vaginal opening
- 35. Male Urethra: •Length-20cm • It first passes through prostate, then through deep muscles of perineum finally through Penis • External urethral orifice located in penis
- 36. Walls of urethra:In both sexes the structure is the sameIts walls consist of three layers of tissue: • the muscle layer, continuous with that of the bladder. At its origin there is the internal urethral sphincter, consisting mainly of elastic tissue and smooth muscle fibers, under autonomic nerve control. Slow and continuous contraction of this sphincter keeps the urethra closed. In the middle third there is skeletal muscle surrounding the urethra, under voluntary nerve control, that forms the external urethral sphincter • the submucosa, a spongy layer containing blood vessels and nerves • the mucosa, which is continuous with that of the bladder in the upper part. In the lower part the lining consists of stratified squamous epithelium, continuous externally with the skin of the vulva. Function: Discharge of urine. In males, it also discharges semen