Chapter 26: The Urinary System

1
Chapter 26 The Urinary System
2
What are the components of the urinary system
and the functions it performs?
3
Functions of Urinary System

• Excretion
• Elimination
• Urination or Micturition
• Homeostatic regulation

4
Organs of Urinary System

• kidneys
• ureters
• urinary bladder
• urethra

5
Figure 261
6
What are the location and structures of the
kidneys?
7
The Kidneys

• Are located either side of vertebral column
• superior surface capped by adrenal gland
• Position maintained by
• supporting connective tissues
• renal capsule
• adipose tissue
• renal fascia

8
The Position of the Kidneys
Figure 262
9

• Hilus
• Point of entry for renal artery and renal nerves
• Point of exit for renal vein and ureter

10
Gross Anatomy of the Urinary System
Figure 263
11

• Renal Sinus
• Internal cavity within kidney
• Renal Cortex
• Superficial portion of kidney in contact with
  renal capsule
• Renal Medulla
• distinct triangular structures called renal
  pyramids

12

• Renal Pelvis
• Large, funnel-shaped chamber
• Consists of 2 or 3 major calyces
• Connected to ureter, which drains kidney

13

• Renal Columns
• Bands of cortical tissue separate adjacent renal
  pyramids
• Extend into medulla
• Renal Papilla
• Ducts discharge urine into minor calyx
• Combine to form major Calyx

14
Renal Lobe

• Consists of
• renal pyramid
• overlying area of renal cortex
• adjacent tissues of renal columns
• Produces urine

15
The Structure of the Kidney
Figure 264
16
What is the structure of the nephron and the
processes involved in the formation of urine?
17

• Nephrons
• Microscopic, tubular structures in cortex of each
  renal lobe
• Functional unit of the kidney
• Where urine production begins
• Consists of renal tubule and renal corpuscle

18

• Renal Corpuscle
• Bowmans capsule
• capillary network (glomerulus)
• Plasma-derived fluid (filtrate) is forced out of
  the capillaries, trapped in the capsule then
  processed by the renal tubules to form urine

19
Segments of Renal Tubule

• Located in cortex
• proximal convoluted tubule (PCT)
• distal convoluted tubule (DCT)
• Separated by loop of Henle
• U-shaped tube
• extends partially into medulla

20
3 Functions of Renal Tubule

• Reabsorb useful organic nutrients that enter
  filtrate
• Reabsorb more than 90 of water in filtrate
• Secrete waste products

21
Juxtaglomerular Apparatus

• An endocrine structure that secretes
• hormone erythropoietin
• enzyme renin
• mechanoreceptors sense blood pressure in the
  afferent arterioles
• macula densa cells act as chemoreceptors which
  respond to changes in solute concentration of
  filtrate

22
Collecting Ducts

• Receive fluid from many nephrons
• Each collecting duct
• begins in cortex
• descends into medulla
• carries fluid to papillary duct that drains into
  a minor calyx
• site of final adjustments to urine concentration

23
Functional Anatomy of Nephron and Collecting
System
Figure 266
24

• Cortical Nephrons (85)
• Located within superficial cortex
• Loop of Henle is relatively short
• Efferent arteriole delivers blood to a network of
  peritubular capillaries which surround entire
  renal tubule

25

• Juxtamedullary Nephrons (15)
• long loops of Henle that extend deep into medulla
• Peritubular capillaries connect to vasa recta
• long, straight capillaries parallel with loop of
  Henle

26
Cortical and Juxtamedullary Nephrons
Figure 267
27
What are the major blood vessels associated with
each kidney and the path of blood flow through a
kidney?
28
Blood Supply to Kidneys

• Kidneys receive 2025 of total cardiac output
• 1200 ml of blood flows through kidneys each
  minute
• Kidney receives blood through renal artery and is
  drained by renal vein
• Glomerulus is supplied by afferent arterioles and
  drained by efferent arterioles

29
Blood Supply to the Kidneys
30
Renal Nerves

• Innervate kidneys and ureters
• Enter each kidney at hilus
• Follow tributaries of renal arteries to
  individual nephrons

31
Sympathetic Innervation

• Adjusts rate of urine formation
• by changing blood flow and blood pressure at
  nephron
• Stimulates release of renin
• which restricts losses of water and salt in urine
• by stimulating reabsorption at nephron