Urinary system
Lab 7
Announcements
• Urinary system
• Lab Practical Week after Spring Break
• Practical Review this Sunday 23rd at 3-5
pm
Functions of Urinary System
• Kidneys carry out four functions
– Filter nitrogenous wastes, toxins, ions, etc. from blood
to be excreted as urine.
– Regulate volume and chemical composition of blood
(water, salts, acids, bases).
– Produce regulatory enzymes.
• Renin – regulates BP/ kidney function
• Erthropoeitin – stimulates RBC production from marrow.
– Metabolism of Vitamin D to active form.
Urinary System
• Two Kidneys
– Perform all functions except actual excretion.
• Two Ureters
– Convey urine from Kidneys to Urinary Bladder
• Urinary Bladder
– Holds Urine until excretion
• Urethra
– Conveys urine from bladder to outside of body
Complete System
Kidney general info
• Lie against posterior abdominal wall at level of
T12-L3.
• Right kidney is lower than left kidney due to the
shape of the liver.
• Lateral surface of kidney is convex while medial
is concave.
– Concave side has a cleft – Renal Hilus
– Inside hilus is Renal sinus
• Where kidneys receive renal vessels and nerves.
Kidney External Anatomy
• Average size – 12cm x 6cm x 3 cm
• Weights 150 grams or 5 oz
• Surrounded by three membranes (deep to
superficial)
– Renal capsule – fibrous barrier for kidneys.
– Adipose capsule – fatty tissue designed for protection /
stability.
– Renal fascia – dense fibrous CTP anchors kidneys/
adrenals/ membrane 1 and 2 to surroundings.
Kidney Anatomy
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Renal arteries and veins
Renal cortex
Renal medulla
Nephron
Renal pyramids (6-10)
Renal papilla
Calyx (ces)
Renal pelvis
Ureter
Kidney- External Anatomy
• Lateral surface- convex
• Medial is concave– Renal Hilum
• Opening to Kidney
– Renal Sinus
• Space within hilus
• Kidneys receive blood vessels and nerves.
Kidney Internal Anatomy I
• Renal arteries and veins
– Bring blood in and out of kidney
• Renal cortex
– Outer layer of Kidney
• Renal medulla
– Inner layer of Kidney
• Nephron
Kidney Internal Anatomy II
• Renal Pyramids
• Renal Columns
– Space between pyramids
within the medula
• Renal Papilla
– Narrow end of pyramid
• Calyx (ces)
– Collecting tubes
• Renal Pelvis
– Collecting vessel prior to
ureter
Human Kidney
Nephron
• Blood processing unit which serves to
produce urine
• 1 million per kidney
• Consists of a glomerulus and tubules
Nephron: Vascular System
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Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries
– Capillary beds
reabsorb in cortex
• Vasa recta
– Capillary beds
reabsorb in medulla
Nephron
• Tubular system
– Glomerular Capsule
– Proximal convoluted tubule
– Loop of Henle (nephron loop)
• Descending limb
• Ascending limb
– Distal convoluted tubule
– Collecting duct
Nephron
Dynamic Human
Gross Anatomy
Urinary system
Kidney
Nephron
Urine Formation I
• Glomerular filtration
• Water, ions, amino
acids, and glucose get
into capsular space
from blood
• Proteins stay in blood
– too big to leave
capillaries.
Urine Formation II
• Proximal convoluted
tubule and Peritubular
capillary
• Na+ goes down
gradient and brings
glucose, amino acids,
etc. back into blood
stream (cotransport).
• Reabsorbs about 65%
of filtrate.
Urine Formation III
Countercurrent Multiplication
in the Nephron Loop
• Descending limb
• Ascending limb
• Goes into medulla
- increasing salt
gradient
• Water leaves
• Fluid concentrates
• Goes up toward cortex
- decreasing salt
gradient
• Na+ pumped out
• Fluid relatively diluted
Nephron Loop
Urine Formation IV
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Collecting duct
Travels down into medulla
Water leaves tubule and enters blood
Urine becomes concentrated and enters
renal papilla
• ADH controls water channel
• ADH – Antidiuretic hormone
Collecting duct
Dynamic Human
Urine Formation
Micturition
• Ureters
– 25 cm long
– Enters on the floor of bladder
• Urinary Bladder
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Muscular sac on floor of pelvic cavity
Muscle layer formed by detrusor muscle
Average bladder volume is 500 ml
Max capacity is 700-800 ml
Micturition
• Urethra
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Conveys urine out of body
Female urethra – 3 - 4 cm
Opens into external urethral oriface
Lies between vaginal oriface and clitoris
Male urethra – 18 cm
3 regions
• Prostatic urethra – 2.5 cm
• Membranous urethra – 0.5 cm
• Penile urethra – 15 cm
Micturition Reflex
Bladder with >= 200 ml of urine
Sensory input to parasympathetic system
Contraction of detrusor muscle and relaxation
of internal urethral sphincter
Relaxation of external urethral sphincter
Micturition
Kidney stones
• A hard granule of calcium, phosphate, uric acid
and protein.
• Form in renal pelvis and get lodged in pelvis or
ureter.
• Caused by urinary tract infections, dehydration,
pH imbalances, or an enlarged prostate gland.
• Treated with stone dissolving drugs, surgical
removal, or lithotripsy (ultrasonic vibrations)
Dynamic Human
Visualizing the Urinary System
Intravenous pyelography
Ultrasound
Dissection
• Be able to identify layers of the kidney on
human material
• Be able to locate kidneys, ureters, urinary
bladder, and urethra on cat.
Next Week – Spring Break
Week After - Practical II
• Material over lymphatic, respiratory, and
urinary systems
• Review Sunday (end of break) at 3-5pm
• Remember – some questions will be based
on identifying structures on the cats.