Unit 10 - Notes

Unit 10 – Urinary System

  • Produces, stores, and excretes urine.
  • Organs include 2 kidneys, 2 ureters, 1 urinary bladder, and 1 urethra.


I.                  Kidney

a.     Lie just above the waistline in the posterior wall.

b.     Left kidney sits higher than right.

c.      20% of all blood enters kidneys to remove waste products.

II.               Kidney Stones

a.     Metallic Ions crystallize in the Kidney and then try and make their way through the urinary system. 

b.     Due to a lack of water to dissolve metal ions

c.      Very painful

III.           Internal Structure of the Kidneys

a.     Cortex – Outer layer

b.     Medulla – Inner portion

c.      Pyramids – Triangular divisions of the medulla

d.     Papilla – Narrow end of pyramid

e.      Pelvis – Enlarged portion   of upper ureter

f.       Calyx –  Small divisions     of renal pelvis

IV.           Microscopic Structure of the Kidney

a.     Made up of millions of nephrons.

b.     Nephron composed of renal corpuscle (in cortex) and renal tubule.

c.      Renal Corpuscle

·  Glomerulus – Network of capillaries in Bowman’s capsule

·  Bowman’s capsule – Cup shaped top of nephron.

·  Afferent arteriole – To glomerulus

·  Efferent arteriole - Away from glomerulus

d.    Renal Tuble

·  Proximal convoluted tubule – 1st segment.

·  Loop of Henle – Extension of proximal tubule.

·  Distal convoluted tubule – Distal portion.

·  Collecting tubule – Tube made up of several distal tubes.

V.               Functions of the Kidneys

a.     Form urine

b.     Balance substances entering and leaving the blood

c.      Excretion of toxins containing nitrogen (urea and ammonia)

d.     Regulates levels of chemicals in blood (Cl, Na, K, and bicarbonate)

e.      Regulate blood pressure

VI.           Formation of Urine

a.     Formed in 3 processes

·   Filtration

1.     Occurs in Bowman’s capsule and glomeruli

2.     Blood pressure increases in glomeruli which pushes dissolved substances into Bowman’s capsule and then into tubules.

·  Reabsorption

1.     Movement of substances out of tubules into blood capillaries

2.     Water, glucose, and sodium are reabsorbed

3.     Reabsorption occurs in Proximal tubule, Loop of Henle, and Distal tubule

·  Secretion

1.     Waste products (those substances not reabsorbed) move into collecting duct and ureters.

2.     Waste products include H ions, K ions, NaOH, Urea, Ammonia, and Drugs. 

VII.        Control of Urine Volume

a.     ADH (Hormone of Pituitary Gland) causes tubules to become impermeable, therefore retaining water.

b.     Aldosterone (hormone of Adrenal Glands – salt retaining hormone) retains water.

c.      ANH causes tubules to secrete more salt, therefore, losing water.

d.     Anuria – Absence of urine

e.      Oliguria – Trace amounts of urine

f.       Polyuria – Large amounts of urine

VIII.    Ureters


a.     Collects urine from collecting ducts.

b.     Transports urine by peristalsis to urinary bladder.

c.      Membrane of ureters are rich in nerve endings

d.  Internal Anatomy of tube

  • Outer layer of connective tissue called adventitia
  • Middle layer of Visceral muscle for peristalsis
  • Inner layer of transitional epithelial tissue for tube expansion



IX.           Urethra

a.     Lowest part of urinary tract.

b.     4 cm long (woman),  20 cm long (man)

c.      In men, urethra serves as passageway for urine and semen.

d.     In women, only a urinary structure


X.               Micturation / Urination / Voiding

a.     Refers to passage of urine from the body.

b.     2 sphincters control urine flow

c.      Internal urethral sphincter at bladder exit (involuntary)

d.     External urethral sphincter circles urethra (voluntary)

e.      Urinary Retention – No urine is voided

f.       Urinary Suppression – Kidneys produce no urine

g.     Incontinence – Urine is voided involuntarily