![Stages of Urine Formation (Micturition)
[glomerular filtration rate = 125 ml/min]
1. Filtration: glomerulus
2. Reabsorption: tubules
– Proximal convoluted tubules
•
Major reabsorption of electrolytes
–
Na, K, Ca, Mg, Cl
– Loop of Henle
•
Major reabsorption site for Na
– Collecting tubule
•
H2O reabsorption
3. Secretion
ANATOMY
h_noveno@hotmail.com
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Unit 13 Genitourinary System
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- 3. ORGANS OF THE URINARY SYSTEM Kidneys Ureters Urinary bladder Urethra ANATOMY h_noveno@hotmail.com 3
- 4. LOCATION OF THE KIDNEYS • • • • Against the dorsal body wall At the level of T12 to L3 The right kidney is slightly lower than the left Attached to ureters, renal blood vessels, and nerves at renal hilus • Atop each kidney is an adrenal gland ANATOMY h_noveno@hotmail.com 4
- 5. COVERINGS OF THE KIDNEYS • Renal capsule – Surrounds each kidney • Adipose capsule – Surrounds the kidney – Provides protection to the kidney – Helps keep the kidney in its correct location ANATOMY h_noveno@hotmail.com 5
- 6. REGIONS OF THE KIDNEY • Renal cortex – outer region • Renal medulla – inside the cortex • Renal pelvis – inner collecting tube ANATOMY h_noveno@hotmail.com 6
- 8. KIDNEY STRUCTURES • Medullary pyramids – triangular regions of tissue in the medulla • Renal columns – extensions of cortex-like material inward • Calyces – cup-shaped structures that funnel urine towards the renal pelvis ANATOMY h_noveno@hotmail.com 8
- 11. BLOOD FLOW IN THE KIDNEYS ANATOMY h_noveno@hotmail.com 11
- 12. Stages of Urine Formation (Micturition) [glomerular filtration rate = 125 ml/min] 1. Filtration: glomerulus 2. Reabsorption: tubules – Proximal convoluted tubules • Major reabsorption of electrolytes – Na, K, Ca, Mg, Cl – Loop of Henle • Major reabsorption site for Na – Collecting tubule • H2O reabsorption 3. Secretion ANATOMY h_noveno@hotmail.com 12
- 15. NEPHRONS • The structural and functional units of the kidneys • Responsible for forming urine • Main structures of the nephrons – Glomerulus – Renal tubule ANATOMY h_noveno@hotmail.com 15
- 19. GLOMERULUS • A specialized capillary bed • Attached to arterioles on both sides (maintains high pressure) – Large afferent arteriole – Narrow efferent arteriole ANATOMY h_noveno@hotmail.com 19
- 20. RENAL TUBULE • • • • Glomerular (Bowman’s) capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule ANATOMY h_noveno@hotmail.com 20
- 22. TYPES OF NEPHRONS • Cortical nephrons – Located entirely in the cortex – Includes most nephrons • Juxtamedullary nephrons – Found at the boundary of the cortex and medulla ANATOMY h_noveno@hotmail.com 22
- 24. PERITUBULAR CAPILLARIES • • • • • Arise from efferent arteriole of the glomerulus Normal, low pressure capillaries Attached to a venule Cling close to the renal tubule Reabsorb (reclaim) some substances from collecting tubes ANATOMY h_noveno@hotmail.com 24
- 25. URETERS • Slender tubes attaching the kidney to the bladder – Continuous with the renal pelvis – Enter the posterior aspect of the bladder • Runs behind the peritoneum • Peristalsis aids gravity in urine transport ANATOMY h_noveno@hotmail.com 25
- 27. LINING OF THE URETER ANATOMY h_noveno@hotmail.com 27
- 28. URINARY BLADDER • Smooth, collapsible, muscular sac • Temporarily stores urine • Trigone – three openings – Two from the ureters – One to the urethrea • Urinary Bladder Wall – – – – ANATOMY Three layers of smooth muscle (detrusor muscle) Mucosa made of transitional epithelium Walls are thick and folded in an empty bladder Bladder can expand significantly without increasing internal pressure h_noveno@hotmail.com 28
- 31. URETHRA • Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis • Release of urine is controlled by two sphincters – Internal urethral sphincter (involuntary) – External urethral sphincter (voluntary) ANATOMY h_noveno@hotmail.com 31
- 32. URETHRA GENDER DIFFERENCES • Length – Females – 3–4 cm (1 inch) – Males – 20 cm (8 inches) • Location – Females – along wall of the vagina – Males – through the prostate and penis • Function – Females – only carries urine – Males – carries urine and is a passageway for sperm cells ANATOMY h_noveno@hotmail.com 32
- 33. DEVELOPMENTAL ASPECTS OF THE URINARY SYSTEM • Functional kidneys are developed by the third month • Urinary system of a newborn – Bladder is small – Urine cannot be concentrated • Control of the voluntary urethral sphincter does not start until age 18 months • Urinary infections are the only common problems before old age ANATOMY h_noveno@hotmail.com 33
- 34. AGING AND THE URINARY SYSTEM • There is a progressive decline in urinary function • The bladder shrinks with aging • Urinary retention is common in males ANATOMY h_noveno@hotmail.com 34