URINARY SYSTEM

I.   INTRODUCTION
–  Urinary System: kidneys, ureters, urinary bladder, and urethra
*  urinary tract: ureters, bladder and urethra

–  main functions:  filter blood

and transport the liquid waste (urine) outside the body

*  kidneys reponsible for filtering blood

*  urinary tract transports the urine
*  process of releasing urine:  urination, or micturition

–  What is urine?

–  urinary system primarily innervated by autonomic nervous system

II.  KIDNEYS
A.  External Gross Anatomy:
-- on posterior abdominal wall
-- right kidney lower than the left

-- renal hilum: indentation in medial portion of kidney

 

 

B.  Internal Gross Anatomy:
-- outer cortex and an inner medulla

 

–  renal columns:

 

 

 

--  renal pyramids:

 

 

 

 

–  each renal pyramid drains urine into a minor calyx

–  several minor calyces unite to form a major calyx

-- major calyces drain into the renal pelvis, which connects to the ureter

 

C.  Blood Supply:

1.  renal artery:  receives arterial blood from aorta

 

 

2.  segmental arteries

3.  interlobar arteries
*  travel in the renal columns

 

4.  arcuate arteries
*  found at the CORTEX-MEDULLA JUNCTION

5.  interlobular arteries

 

 

6.  afferent arterioles

7.  each afferent arteriole brings blood to a glomerulus
*  glomerulus = a  capillary “ball”

*  blood is filtrated here!

 

8.  efferent arteriole

 

 

9.  peritubular capillaries

 

or vasa recta

 

 

 

 

10.  interlobular veins

 

11.  arcuate veins

 

12.  interlobar veins

 

13. renal vein

 

III.  NEPHRONS OF KIDNEYS

A.  Introduction
-- nephron: functional filtration unit of the kidney
** function:  filters blood and modifies this “filtrate” squeezed out of the glomerulus

–  each kidney contains over 1 million nephrons!

-- the nephron consists of:

1) Renal Corpuscle (glomerulus + glomerular capsule)
2) Proximal Convoluted Tubule
3) Nephron Loop (loop of Henle)
4) Distal Convoluted Tubule

B.  Renal Corpuscle:
–  glomerulus

plus glomerular capsule, which surrounds glomerulus

*  capsular space:

**  filtrate is squeezed into here!

-- filtrate then enters the:

 

C.  Proximal Convoluted Tubule (PCT):

– function: to resorb some materials and water in the filtrate

*  resorbed material sent to peritubular capillaries

–  then the filtrate passes into the:

D.  Nephron Loop (Loop of Henle):

– function: to resorb more materials and water in the filtrate
*  resorbed material is sent to the vasa recta

-- remaining filtrate then travels to the:

E.  Distal Convoluted Tubule (DCT):

-- last segment of the nephron

 

–  function: to resorb more materials and water in the filtrate

*  resorbed material sent to peritubular capillaries

IV.  FLOW OF FILTRATE/URINE

1.  filtrate squeezed out of glomerulus, enters capsular space
2.  proximal convoluted tubule
3.  nephron loop
4.  distal convoluted tubule

5.  the filtrate travels through the collecting duct       

* when filtrate leaves the collecting duct, it now may be called urine

6.  minor calyx
7. major calyx
8.  renal pelvis

9.  ureter
10. bladder
11. urine exits the body via the urethra

V.   URETERS

A.  General Description and Function
–  long, thin, paired muscular tubes
-- function: transport urine (via peristalsis)from kidney to urinary bladder

What do you think? Why do the ureters use peristalsis (as opposed to relying on gravity) to pump urine to the urinary bladder?

B.  Layers

1.  Mucosa:

-- transitional epithelium

 

2.  Muscularis:

3.  Adventitia:

-- areolar connective tissue

 

VI.  URINARY BLADDER

A.  General Description and Function
-- function: urine reservoir (muscular storage sac for urine)  

            
-- it’s shape changes as it fills:
* empty:

* full:

–  neck of the bladder = narrow base of bladder

B.  Layers

1.  Mucosa:

-- transitional epithelium

2.  Submucosa: dense irreg CT

 

3.  Muscularis:
-- 3 specific layers of smooth muscle
--  together, these layers are known as the detrusor muscle

-- internal urethral sphincter

 

 

** involuntary sphincter

4.  Adventitia:

-- areolar CT

VII. URETHRA

A.  General Morphology & Function
-- single muscular tube running from bladder to exterior of body

-- function: expels urine from body

-- urethra pierces a group of skeletal muscles called the urogenital diaphragm
** some of the skeletal muscle fibers thicken and form an external urethral sphincter around urethra
** voluntary sphincter

B.  Female Urethra

 

 

C.  Male Urethra              

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