HISTOLOGY OF THE URINARY SYSTEM

1
HISTOLOGY OF THE URINARY SYSTEM

• Prof. Dr. Fauziah Othman
• Department of Human Anatomy
• Faculty of Medicine and Health Sciences
• Universiti Putra Malaysia

2
Contents

• Kidney
• Parts of nephron and structures
• Juxtaglomerular apparatus
• Functional aspects
• Blood circulation
• Ureter and urinary bladder
• General features
• Urinary epithelium Urethra
• Structure of male and female urethra

3
Kidney

• Main organ of the excretory system
• Kidney is built of billions of little tubes
  called the nephrons.
• At the beginning of each nephron, a web of
  capillaries releases much water and other
  molecules into the nephron.
• The urine is collected in the urinary bladder
  and, when it fills up, it is excreted via urethra
  into the outside environment.

4
Kidney's Internal Structure

• Cortex -- the outer part of the kidney
• Medulla -- the inner portion of the kidney
• Pyramids -- the triangular-shaped divisions of
  the medulla of the kidney
• Papilla -- narrow, innermost tip of the pyramid
• Pelvis -- the kidney or renal pelvis is an
  extension of the upper end of the ureter (the
  tube that drains urine into the bladder)
• Calyx -- each calyx is a division of the renal
  pelvis opening into each calyx is the papilla of
  a pyramid.

5
(No Transcript)
6
(No Transcript)
7
Nephron

• basic structural and functional unit of the
  kidney.
• Its chief function is to regulate the
  concentration of water and soluble substances
  like sodium salts by filtering the blood,
  reabsorbing what is needed and excreting the rest
  as urine.

8

• A nephron eliminates wastes from the body,
  regulates blood volume and blood pressure,
  controls levels of electrolytes and metabolites,
  and regulates blood pH. Its functions are vital
  to life and are regulated by the endocrine system
  by hormones such as antidiuretic hormone,
  aldosterone, and parathyroid hormone.

9
(No Transcript)
10

• microscopic units of a kidney, have 2 main parts,
  
• renal corpuscle (Bowman's capsule with
  glomerulus)
• renal tubule.

11
RENAL CORPUSCLE

• glomeruli surrounded by Bowman's capsules.
• Bowman's capsule -- the cup-shaped top of a
  nephron. It is the sack-like Bowmans's capsule
  that surrounds the glomerulus.
• Glomerulus -- a network of blood capillaries
  tucked into Bowman's capsule.

12
(No Transcript)
13
Juxtaglomerular apparatus

• The juxtaglomerular apparatus is a microscopic
  structure in the kidney, which regulates the
  function of each nephron.
• There are three cellular components of the
  apparatus which are the
• macula densa,
• extraglomerular mesangial cells,
• juxtaglomerular cells (also known as granular
  cells).

14
RENAL TUBULE

• Proximal convoluted tubule -- the first segment
  of a renal tubule, called proximal because it
  lies nearest the tubule's origin from Bowman's
  capsule, and convoluted because it has several
  bends in it.
• Loop of Henle -- the extension of the proximal
  tubule observe that the loop of Henle consists
  of a straight descending (directed downward)
  limb, a loop, and a straight ascending limb
  (directed upwards).

15
Cont.

• Distal convoluted tubule -- the part of the
  tubule distal to the ascending limb of Henle. It
  is the extension of the ascending limb of Henle.
• Collecting tubule -- a straight (not convoluted)
  part of a renal tubule distal tubules of several
  nephrons join to form a single collecting tubule

16
Histology Bowman's capsule

• Cells of the outer or parietal layer of Bowman's
  capsule form a simple squamous epithelium.
• Cells of the inner layer, podocytes in the
  visceral layer, are extremely complex in shape.
  Small foot-like processes, pedicles, of their
  cytoplasm form a fenestrated epithelium around
  the fenestrated capillaries of the glomerulus.
• The openings between the pedicles are called
  filtration slits. They are spanned by a thin
  membrane, the filtration slit membrane. Between
  the podocytes and the endothelial cells of the
  capillaries a comparatively thick basal lamina,
  which can be subdivided into an outer lamina
  externa, a middle lamina densa and an inner
  lamina interna.
• The basal lamina and the slit membranes form the
  glomerular filtration barrier, which prevents
  some large molecules from entering the capsular
  space between the outer and inner epithelial
  layers of Bowman's capsule.
• Mesangial cells in the glomerulus form the
  connective tissue that gives structural support
  to podocytes and vessels.

17
Histo proximal tubule

• walls - low columnar epithelium.
• The eosinophilic cells of the epithelium have a
  wide brush border and are active in endocytosis.

18
Histo of Loop of Henle

• It is 'U' shaped and has descending and ascending
  segments.
• Thin descending segment has flattened
  epithelium( squamous). It is permeable to water
  but not solutes.

19
Histo Distal convoluted tubule

• straight part of the DCT is formed by the low
  cuboidal cells without a brush border. The
  diameter of the tubule gradually expands to about
  35 microns.
• convoluted part and comes in contact with the
  Glomerulus forming the Macula Densa.

20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
Nephron structure characteristic
Renal corpusle Capillary ball covered by podocyte surrounded by simple squamous epithelial capsule, capsular space.
Proximal convulated Lined with simple cubodial epithelium prominent brush border
Loop of Henle Tubule that form a loop, there are thick thin ascending desecnding portion the most distal part of the loop often extends into the medulla. Thick limb are lined with simple squamous/ cuboidal epithelium Thin limb are lined with simple squamous epithelium
Distal convulated Lined with simple cuboidal with only sparse brush border cytoplasm of cells tend to be paler than that of proximal convulated
24
Ureter

• The wall of the ureter is made 3 layers. From
  inside outwards they are
• Mucosa- which is made up of epithelium
  lamina propria
• Muscular coat made of smooth muscles
• Fibrosa made of fibrous connective
  tissue
• Mucosa- is thrown into folds and thus gives the
  appearance of star shaped lumen.

25

• 1. Transitional epithelium. 3-5 layers
  thickness.
• 2. Lamina propria- dense, irregular layer of
  
  fibroelastic connective tissue
• The epithelium is separated from the lamina
  propria by a basal lamina.

26

• Muscular layer Upper 2/3 of the ureter is made
  of two layers of smooth muscle cells.
• Inner longitudinal and outer circular layer( in
  contrast to the wall of GIT which has inner
  circular outer longitudinal !).
• Lower 1/3 of the ureter has a third outer layer
  of longitudinal muscles( inner longitudinal,
  middle circular, outer loingitudinal ).
• Fibrous coat is made up of fibrous connective
  tissue

27
(No Transcript)
28
(No Transcript)
29
The urethra

• Female relatively short, exits just anterior to
  the vagina
• Male longer, divided into three sections the
  prostatic, membranous and spongy urethra.  The
  prostatic urethra is enclosed in the prostate
  gland.  The membranous urethra is a short section
  that penetrates the urogenital diaphragm.  The
  spongy urethra or penile urethra extends from the
  membranous urethra to the external urethral
  orifice (meatus).

30

• Histology  In both male and females the urethra
  starts out as transitional cell but quickly
  becomes stratified squamous in the female. 
• The male urethra is more variable but ends up
  stratified squamous as well.

31
(No Transcript)
32
Histology of the bladder

• mucosa of transitional epithelium, Submucosa, and
  thick muscular layer know as the detrusor muscle

33
(No Transcript)
34
(No Transcript)
35
Clinical correlates

• Urinary incontinence
• Childbirth and other events can injure the
  scaffolding that helps support the bladder in
  women. Pelvic floor muscles, the vagina, and
  ligaments support your bladder.
• Overactive bladder

Specifically, the symptoms of overactive
bladder include urinary frequencybothersome
urination eight or more times a day or two or
more times at night urinary urgencythe sudden,
strong need to urinate immediately urge
incontinenceleakage or gushing of urine that
follows a sudden, strong urge nocturiaawaking
at night to urinate
36
THE END
THE END
THE END
THE END
THE END
THE END