The urinary system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter waste and regulate fluid and electrolyte balance by producing urine. Urine travels from the kidneys through the ureters to the bladder, where it is stored until excretion through the urethra. The kidneys contain nephrons, which filter the blood to remove wastes and produce urine through a complex process involving filtration, reabsorption, and secretion.

1. Urinary system
Course: B.Sc.(Micro./Biotech) sem II
Subject: Animal & Plant Physiology
Unit 2.2

2. 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.

3. 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

4. Complete System
1

5. Kidney general info
• Lie against posterior abdominal wall
• 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.

6. 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.

7. Kidney Anatomy
• Renal arteries and veins
• Renal cortex
• Renal medulla
• Nephron
• Renal pyramids (6-10)
• Renal papilla
• Calyx (ces)
• Renal pelvis
• Ureter

8. 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. 2

9. 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

10. 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
3

11. Nephron
• Blood processing unit which serves to produce
urine
• 1 million per kidney
• Consists of a glomerulus and tubules
• Two part:
– Renal corpuscle : blood plasma is filtered
• glomerulus( capillary network)
• Glomerulus capsule(Bowman’s)
– Renal tubule: filtered fluid passes.

12. Nephron: Vascular System
• Afferent arteriole
• Glomerulus
• Efferent arteriole
• Peritubular
capillaries
– Capillary beds
reabsorb in cortex
4

13. Nephron
• Tubular system
– Glomerular Capsule
– Proximal convoluted tubule
– Loop of Henle (nephron loop)
• Descending limb
• Ascending limb
– Distal convoluted tubule
– Collecting duct

14. Nephron
5

15. 6

16. 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.

17. 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.
7

18. Urine Formation III
• Descending limb
• Goes into medulla
- increasing salt
gradient
• Water leaves
• Fluid concentrates
• Ascending limb
• Goes up toward
cortex - decreasing
salt gradient
• Na+ pumped out
• Fluid relatively diluted
Countercurrent Multiplication
in the Nephron Loop

19. Nephron Loop
8

20. Urine Formation IV
• 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

21. Collecting duct
9

22. Dynamic Human
Urine Formation

23. Micturition
• Ureters
– 25 cm long
– Enters on the floor of bladder
• Urinary Bladder
– 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

24. Micturition
• Urethra
– 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

25. 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

26. Micturition
10

27. 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)

28. References:
Image 1: http://postimg.org/image/rbccc1f7t/
Image 2: http://postimg.org/image/kkr9ov2o9/
Image 3: http://postimg.org/image/a0hc69y6h/
Image 4: http://postimg.org/image/87efhyczt/
Image 5: http://postimg.org/image/8rtgkn689/
Image 6: http://postimg.org/image/qgl7c9hzd/
Image 7: http://postimg.org/image/5nisnupft/
Image 8: http://postimg.org/image/zac3td4y1/
Image 9: http://postimg.org/image/fpxkql4cp/
Iamge 10: http://postimg.org/image/mhnztftc9/
Book: 1. Human Physiology 4th
edition by Lauralee Sherwood