Urinary system
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Urinary system. 2 Kidneys. 2 ureters. Urinary bladder. Urethera. A hemisected vew of the kidney. Kidney. Cortex ---Dark brown and granular. Medulla--- 6-12 pyramid-shape regions (renal pyramids) The base of pyramid is toward the cortex ( corticomedullary border)

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Urinary system
Urinary system

  • 2 Kidneys.

  • 2 ureters.

  • Urinary bladder.

  • Urethera.


  • Cortex---Dark brown and granular.

  • Medulla---6-12 pyramid-shape regions (renal pyramids)

    The base of pyramid is toward the cortex (corticomedullary border)

    The apex (renal papilla) toward the hilum that perforated by 12 openings of the ducts of Bellini in region called area cribrosa . The apex is surrounded by minor calyx.

  • Pyramids are separated by cortical columns of Bertin

  • 3or4 minor calyces join to form 3or 4 major calyces that form renal pelvis.

Cortical arch
Cortical arch

Is formed of:

  • Renal corpuscles (red dots).

  • Convoluted tubules

    (cortical labyrinth).

  • Medullary rays

    (cortical continuation of pyramids).

  • NB. Lobe of the kidney is formed of:

    a- Renal pyramid.

    b-Cortical columns.

    c-Cortical arch

    *Each medullary ray with part of the cortical labyrinth surrounding it form kidney lobule.

Uriniferous tubule
Uriniferous tubule

  • Is the functional unit of the kidney.

  • Is formed of:

    1- Nephron.

    2-Collecting tubule.

  • They are densely packed.

  • They are separated

    by thin stroma

    and basal lamina.


  • There are 2 types:

    a-Cortical nephrons.


    *It is formed of :

    1-Renal corpuscle.

    2-Proximal tubule.

    3-Thin limbs of Henle’s loop.

    4-Distal tubule

Renal corpuscle
Renal corpuscle

  • Glomerulus (tuft of fenestrated capillaries)

  • Bowman’s capsule (Parietal layer, urinary or glomerular space and visceral layer or podocytes).

  • Mesangial cells (intraglomerular & extraglomerular).

Renal cortex
Renal cortex

Renal corpuscle

Filtration barrier
Filtration barrier

  • Endothelialwall of the capillaries.

  • The basal lamina (inner and outer laminaerarae and middle lamina densa).

  • Visceral layer of Bowman’s capsule (podocytes)

  • Podocytes have primary (major) processes and secondary (minor) processes (pedicles).

  • Between pedicles (on the surface of capillaries) there are filtration slits that

    have slit diaphragm

Proximal tubule
Proximal tubule

  • It has 2 regions:

    1-Pars convoluta (Proximal convoluted tubule).

    2-Pars recta (descending thick limb of Henle’s loop).

    It is composed of simple

    cuboidalepith.with acidophilic

    cytoplasm. The cells have striated

    or brush border and lateral

    interdigitations. They have

    well-defined basal lamina.

Thin limb of henle s loop
Thin limb of Henle’s loop

  • It has 3 regions:

    1-Descending thin limb.

    2-Henle’s loop.

    3-Ascending thin limb.

    NB. It is longer in juxtamedullary

    nephron than in cortical nephron.

  • It is composed of simple

  • squamousepith.

Distal tubule
Distal tubule

  • It has 3 regions:

    1-Ascending limb of Henle’s loop (low cuboidal epith.).

    2-macula densa (tall &narrow cells).

    3-Pars convoluta (distal convoluted tubule) formed of low cuboidal epith.

    NB. Because distal convoluted are much shorter than proximal convoluted tubules, any section of renal cortex presents many more sections of proximal convoluted tubules.

    *Distal tubules drain into collecting tubules.

    *Aldosterone hormone increase the active rebsorbtion of sodium from the lumen of tubule into interstitium.

Juxtaglomerular apparatus
Juxtaglomerular apparatus

Juxtaglomerular apparatus1
Juxtaglomerular apparatus

  • It has 3 components:

  • A-The macula densa of distal tubule.

  • B-Juxtaglomerular cells of afferent glomerular arteriole (modified smooth muscle of tunica media). They secrete renin,angiotensin-converting enzyme and angiotensin.

  • C-The extraglomerularmesangial cells.

Collecting tubules
Collecting tubules

  • Are composed of simple cuboidal epithelium.

  • They aren’t part of nephron.

  • They have 3 regions:



    3-Papillary (ducts of Bellini) they open in area of cribrosa.

    *They are formed of: a-principle cells.

    and b-intercalated cells.

    *They are impermeable to water except in presence of antidiuretic hormone.

Renal interstitium
Renal interstitium

  • It is a very flimsy, scant amount of CT contains.

  • 1-Fibroblasts.

  • 2-Macrophages.

  • 3-Interstitial cells (their nuclei are elongated and they contain lipid droplets). They secrete medullipin I, which is converted in the liver into medullipin II, that lowers blood pressure.


  • Each calyx accepts urine

    from the renal papilla of

    a renal pyramid.

  • They are lined with

    transitional epith., lamina propria

    and smooth muscle.

  • Minor calyces merge to form major calyces (with same lining tissue as minor calyces).

  • Major calyces open into renal pelvis.


  • 1.Mucosa is formed of transitional

    epith. And lamina propria.

  • 2.Muscularis (muscular coat)

    is formed of 2 layers of smooth muscle:

    A-Inner longitudinal.

    B-Outer circular.

  • 3.Adventitia (fibrous CT covering).

Urinary bladder
Urinary bladder

  • It has the same structure as the ureter EXCEPT:

  • The dome-shaped cells have plaques (rigid, thickened regions of plasmalemma)

  • Between plaques there are normal cell membrane (interplaque regions).

  • It has 3 layers of smooth muscle,

    inner and outer longitudinal and

    middle circular.

  • Its outer covering is serosa.

Female urethra
Female Urethra

  • Female urethra is short and lined by :

    1-Transitional epith. Near the bladder.

    2-Pseudostratified columnar epith. And stratified squamous non-keratinized epith.

    3-Subepth.fibroelastic CT that contains glands of Littre (mucus secreting glands).

    4-Smooth muscle (inner longitudinal and outer circular layer).

Male urethra
Male Urethra

  • It is long and is divided into 3 regions:

    1-The prostatic urethra—lined with transitional epith.

    2-Membranous urethra---lined with pseudustratified columnar and stratified columnar epith.

    3-Penile (spongy) urethra---lined with pseudostratified columnar, stratified columnar and stratified squamous non-keratinized epith.

    * Its lamina propria contains mucus secreting glands of Littre.