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Anatomy of the Urinary System
Exercise 43 Anatomy of the Urinary System
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Functions of the kidney
Excretory Keeps the electrolyte balance Keeps the acid-base balance Keeps the water balance
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Gross anatomy Kidney The right kidney is in a lower position than the left. Located at the superior lumbar region of the dorsal body wall Hilus Renal artery, vein and ureter
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Figure 25.3
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Gross anatomy Capsules
They hold the kidney in place and also protect them Adipose capsule Fibrous capsule
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Gross anatomy Cortex Superficial kidney region immediate bellow the capsule Light color Medulla Darker color Deep to the cortex
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Gross anatomy Medullary pyramids Base Papilla or apex Renal columns
Cortical tissue between the pyramids Minor calyces Major calyces
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Gross anatomy Renal pelvis
Cavity formed by the joining of the major calyces and is continuous with the ureter Blood flow to the kidneys Aorta Renal arteries Segmental arteries (5 branches) Interlobar arteries
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Gross anatomy Arcuate arteries Interlobular arteries
Afferent arterioles Supply the nephron Glomerulus (capillaries) Efferent arterioles
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Gross anatomy Peritubular capillaries Interlobular veins Arcuate veins
Interlobar veins Renal veins Inferior vena cava There is no segmental veins
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Gross anatomy Ureters Drain urine from the kidney to the bladder
Trigone 2 ureteral orifices 1 urethral orifice
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Gross anatomy Detrusor muscle Rugae Parietal peritoneum
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Gross anatomy Urethra Drains urine from the bladder Males
Belongs to the urinary and reproductive systems Prostatic, membranous, penile or spongy Female Belong to the urinary system only
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Figure 25.18a
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Gross anatomy Internal urethral sphincter Smooth muscle
Superior to the external one External urethral sphincter Skeletal muscle Inferior to the internal one
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Microscopic anatomy of the kidney
Nephrons Functional unit of the kidneys Formed by: 1) Glomerulus Glomerular capsule or Bowman’s capsule Visceral layer with podocytes cells that interdigitate with each other and cling to the endothelial cells. Pedicels
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Microscopic anatomy of the kidney
Capsular space Parietal layer Renal corpuscle Glomerulus + Bowman's capsule 2) Renal tubules Proximal convoluted tubules (PCT) Simple cuboidal epithelium with microvilli
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Microscopic anatomy of the kidney
Loop of Henle Descending loop Thick filament Thin filament with simple squamous epithelium and small number of microvilli
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Microscopic anatomy of the kidney
Ascending loop Thick filament Thin filament - simple squamous epithelium Distal convoluted tubule (DCT) Simple cuboidal epithelium
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Microscopic anatomy of the kidney
Collecting ducts Receives urine from many nephrons Run through the medullary pyramids Papillary ducts Collect urine from the collecting ducts Empty the urine into the minor calyces
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Microscopic anatomy of the kidney
Types of nephrons Cortical Located within the renal cortex Juxtamedullary Locted at the cortex-medulla junction Loops of Henle penetrate the medulla
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Figure 25.5a
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Microscopic anatomy of the kidney
Renal circulation for the nephron Glomerular capillaries It produces the filtrate It is a high hydrostatic pressure capillary bed because: It is fed by 2 arterioles The afferent arterioles is larger than the efferent
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Microscopic anatomy of the kidney
Peritubular capillary bed Low pressure capillaries Porous walls Absorbs contents of the filtrate
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Microscopic anatomy of the kidney
In the cortical nephrons the efferent arterioles will form the peritubular capillaries. From there the blood will flow to the vein system
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Microscopic anatomy of the kidney
In the juxtamedullary nephrons, the peritubular capillaries descend immediately into the medulla and give rise to the vasa recta. They run parallel to the loop of Henle and from there the blood will flow to the vein system
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Microscopic anatomy of the kidney
Juxtaglomerular apparatus (JGA) Macula densa Specialized epithelial cells of the DCT Juxtaglomerular cells Specialized smooth muscle cells of the wall of the arterioles
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Figure 25.6
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Urine formation Filtration
Filtrate is forming by the passage of fluid from the afferent arteriole to the Bowman’s capsule Reabsorption Occurs mainly in the PCT It is passive for water It is active for many substances
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Urine formation Secretion
Substances pass from the tubular cells or from the blood to the tubular lumen It happens mainly on the DCT
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Bladder For urine storage Micturition or voiding
Mechanism of micturition Urine is collected until it reaches 200 ml Stretching of the bladder wall Activation of the stretching receptors Impulse is sent through the parasympathetic fibers
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Bladder Impulse reaches the CNS
CNS sends motor command for the bladder to contract Relaxation of the internal sphincter Urine passes to the posterior portion of the urethra Voiding or not (voluntary action)
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Bladder Incontinence Lack of voluntary control of the external urethral sphincter Microscopy Transitional epithelium Detrusor muscle Inner longitudinal layer Central circular layer Outer longitudinal layer
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Microscopic Identification
Kidney Cortex Renal Corpuscle Glomerulus Bowman’s capsule and space Medulla Renal tubules
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Kidney dissection Whole kidney Hylus Capsule: fibrous and fat
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Kidney dissection Frontal cut Cortex Medulla Pyramids Papilla Columns
Calyces: major, minor Pelvis
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Cat Dissection Urinary System Kidneys Ureters Bladder Urethra
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