Anatomy of the Urinary System Exercise 43 Anatomy of the Urinary System

Functions of the kidney Excretory Keeps the electrolyte balance Keeps the acid-base balance Keeps the water balance

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

Figure 25.3

Gross anatomy Capsules They hold the kidney in place and also protect them Adipose capsule Fibrous capsule

Gross anatomy Cortex Superficial kidney region immediate bellow the capsule Light color Medulla Darker color Deep to the cortex

Gross anatomy Medullary pyramids Base Papilla or apex Renal columns Cortical tissue between the pyramids Minor calyces Major calyces

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

Gross anatomy Arcuate arteries Interlobular arteries Afferent arterioles Supply the nephron Glomerulus (capillaries) Efferent arterioles

Gross anatomy Peritubular capillaries Interlobular veins Arcuate veins Interlobar veins Renal veins Inferior vena cava There is no segmental veins

Gross anatomy Ureters Drain urine from the kidney to the bladder Trigone 2 ureteral orifices 1 urethral orifice

Gross anatomy Detrusor muscle Rugae Parietal peritoneum

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

Figure 25.18a

Gross anatomy Internal urethral sphincter Smooth muscle Superior to the external one External urethral sphincter Skeletal muscle Inferior to the internal one

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

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

Microscopic anatomy of the kidney Loop of Henle Descending loop Thick filament Thin filament with simple squamous epithelium and small number of microvilli

Microscopic anatomy of the kidney Ascending loop Thick filament Thin filament - simple squamous epithelium Distal convoluted tubule (DCT) Simple cuboidal epithelium

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

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

Figure 25.5a

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

Microscopic anatomy of the kidney Peritubular capillary bed Low pressure capillaries Porous walls Absorbs contents of the filtrate

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

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

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

Figure 25.6

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

Urine formation Secretion Substances pass from the tubular cells or from the blood to the tubular lumen It happens mainly on the DCT

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

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)

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

Microscopic Identification Kidney Cortex Renal Corpuscle Glomerulus Bowman’s capsule and space Medulla Renal tubules

Kidney dissection Whole kidney Hylus Capsule: fibrous and fat

Kidney dissection Frontal cut Cortex Medulla Pyramids Papilla Columns Calyces: major, minor Pelvis

Cat Dissection Urinary System Kidneys Ureters Bladder Urethra