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PowerPoint® Lecture Slides
prepared by
Janice Meeking,
Mount Royal College
CHAPTER
25
The Urinary
System: Part A
Copyright © 2010 Pearson Education, Inc.
Kidney Location and External Anatomy
• The kidneys lie in a retroperitoneal position in the
superior lumbar region
• The right kidney is lower than the left because it is
crowded by the liver
• The lateral surface is convex; the medial surface is
concave
• Ureters, renal blood vessels, lymphatics, and nerves
enter and exit at the hilus
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• Kidney is protected by 3
layers:
• A fibrous renal fascia –
outermost
• Adipose capsule – cushions
and holds in place
• Renal capsule – fibrous sac
- innermost
http://www.portfolio.mvm.ed.ac.uk/studentwebs/session5/37/ALBL_kidney.htm
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InterActive Physiology ®:
Anatomy Review, page 4
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Kidney Functions
• Filter 200 liters of blood daily, allowing toxins,
metabolic wastes, and excess ions to leave the body in
urine
• Regulate volume and chemical makeup of the blood
• Maintain the proper balance between water and salts,
and acids and bases
• Production of rennin to help regulate blood pressure
and erythropoietin to stimulate RBC production
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Internal Anatomy
• Cortex – the light colored, granular superficial region
• Medulla – exhibits cone-shaped medullary (renal)
pyramids separated by columns
• The medullary pyramid and its surrounding capsule
constitute a lobe
• Renal pelvis – flat funnel shaped tube lateral to the
hilus within the renal sinus
• Minor and Major calyx – large branches of the renal
pelvis
• Collect urine draining from papillae
• Empty urine into the pelvis
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Blood Supply
• Approximately one-fourth (1200 ml) of systemic cardiac output flows
through the kidneys each minute
• Arterial flow into and venous flow out of the kidneys follow similar
paths
interlobular
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InterActive Physiology ®:
Anatomy Review, page 5
Blood vessels in and around the nephron
• The interlobular artery ascends through the cortex,
become the arcuate, and a series of afferent arterioles
arise from it
• It leads to a spherical structure – glumerulus
• The blood from the glumerulus is carried out by efferent
arteriole
• The capillaries in the glumerulus are found between 2
arteries
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Blood vessels
• The efferent arterioles divide to form the peritubular
capillaries that surround the tubules of the nephron in
the renal cortex
• blood return from the peritubular capillaries to the
cortical radiate veins.
• Some efferent arterioles give rise to long loop-shape
capillaries called vasa recta; these capillaries enter the
medulla
• Vasa recta eventually return blood to arcuate veins
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Nephrons
• Each kidney contains over million nephrons – the
anatomical units responsible for urine formation.
Nephron functions include
• Production of filtrate
• Reabsorption of organic nutrients, water and ions
• Secretion of waste products into tubular fluid
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Nephron’s parts
• Consists of 2 parts:
• The renal corpuscle which is the location of blood
filtration
• It is composed of
• Bowman’s capsule
• Glomerulus
• The renal tubule is the location of filtrate processing into
urine
• It is consists of
• Proximal convoluted tubule (PCT)
• Loop of Henle
• Distal convoluted tubule (DCT)
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Renal corpuscle – in the cortex
• Bowman’s capsule is the outer, simple squamous ET wall (parietal
layer)
• Bowman’s space also called "urinary space", is the space lying
within Bowman's capsule.
• The glumerulus is the "little ball" which occupies most of the
corpuscle:
• Glumerular capillaries have an endothelium that is fenestrated
• The capillaries are wrapped by Podocytes (visceral layer of
Bowman’s capsule)
• the filtration membrane is found between the podocytes and the
capillary endothelium.
• Fluid leaving the glumerular capillaries enter the Bowman’s space
and is called filtrate
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Anatomy of the Glomerular Capsule
• The external parietal layer is a structural layer
(Bauman’s capsule)
• The visceral layer consists of modified, branching
epithelial podocytes
• Extensions of the octopus-like podocytes terminate in
foot processes
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Renal Tubule
• Proximal convoluted tubule (PCT) – composed of cuboidal
cells with numerous microvilli and mitochondria
• Reabsorbs water and solutes from filtrate and secretes
substances into it
• Loop of Henle – a hairpin-shaped loop of the renal tubule
• Proximal part is similar to the proximal convoluted tubule
• Proximal part is followed by the thin segment (simple
squamous cells) and the thick segment (cuboidal to
columnar cells)
• Distal convoluted tubule (DCT) – cuboidal cells without
microvilli that function more in secretion than reabsorption
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Nephrons
• Cortical nephrons – 85% of nephrons; located in the
cortex
• Juxtamedullary nephrons:
• Are located at the cortex-medulla junction
• Have loops of Henle that deeply invade the
medulla
• Have extensive thin segments
• Are involved in the production of concentrated
urine
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The ureters
• Pair of muscular tubes
• Extend from renal pelvis to the bladder
• Peristaltic contractions force urine toward the urinary
bladder
• Walls have layers
• Mucosa consists of transitional epithelium
• Muscularis of circular & longitudinal muscle layers
• Adventitia that is composed of loose connective tissue
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The urinary bladder
• Hollow, muscular organ
• Reservoir for the storage of urine
• Contraction of detrusor muscle voids bladder
• Internal features include
• Trigone
• Neck
• Internal urethral sphincter – smooth muscle
• External urethral sphincter – skeletal muscle
• Ruggae
• Detrusor (muscularis) is 3 layers of smooth muscle: inner
longitudinal, middle circular and outer longitudinal.
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The urethra
• Extends from the urinary bladder to the exterior of the
body
• Passes through urogenital diaphragm (external
urinary sphincter)
• Differs in length and function in males and females
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