College of dentistry / Baghdad university Lect.6 Urinary system
Urinary System
Urinary system consists of: paired kidneys; ureters; bladder; and
urethra.
Urine is produced in the kidneys, passing through the ureters to the
bladder, where it is temporarily stored and then released to the exterior
through the urethra.
General functions of urinary system:
1-Maintenance of homeostasis by production of urine, in which various
metabolic waste products are eliminates.
2- kidneys also regulate fluid and electrolytes balance of the body.
3- kidneys are the site of production of two hormones: rennin and
erythropoietin.
Rennin: participate in the regulation of blood pressure.
Erythropoietin: is a growth factor glycoprotein, which stimulate
erythrocyte production.
Kidneys: (Figure 1 left)
Each kidney has a concave medial border (the hilum) where nerves
enter, blood and lymph vessels enter and exit, and the ureter exit. Kidney
also contain convex lateral surface. The renal pelvis (the expanded
upper end of the ureter is divided into two or three major calyces).
Several small branches arise from each major calyces (the minor
calyces).
Each kidney divided into outer region (cortex) and inner region
(medulla). In humans, the renal medulla consists of 8-10 medullary
pyramids (conical or pyramidal structures). Medullary rays extended
from the base of each medullary pyramid (parallel arrays of kidney
tubules). Medullary rays then, penetrate kidney cortex.
Kidney nephron: (Figure 1 right)
Each kidney composed of 1-4 million nephron. Which are the functional
unites of the kidney.
1
, Each nephron consist’s of : 1-renal corpuscle; 2-proximal convoluted
tubule; 3- thin and thick limps of Henle’s loop; 4-distal convoluted
tubule; and 5-the collecting tubule and collecting duct.
Renal corpuscles: (Figure 2)
Each renal corpuscle is about 200µm in diameter, and consists of tuft of
capillaries (the glomerulus), surrounded by a double walled epithelial
capsule (Bowman’s capsule). The internal layer (the visceral layer) of
Bowman’s capsule envelops capillaries of the glumerulus. The external
layer forms the outer limit of the renal corpuscle and is called the
parietal layer. Between the two layers of Bowman’s capsule is the
urinary space.
Each renal corpuscle has a vascular pole (where the afferent
arteriole enter and the efferent arteriole leave; and urinary pole
(where the proximal convoluted tubule begin.
After entering renal corpuscle, the afferent arteriole usually divided
into two to five branches, each subdivided into capillaries and forming
the renal glomerulus.
The parietal layer of Bowman’s capsule consists of a simple squamous
epithelium which is changes to simple cuboidal or low columnar
epithelium at the urinary pole. The visceral layer of bowman’s capsule is
modified to form the podocytes, these cells have a body from which
arise several primary processes. Each primary processes give rise to
secondary processes, which is called pedicels, that embrace the
capillaries of the glomerulus.
2
Urinary System
Urinary system consists of: paired kidneys; ureters; bladder; and
urethra.
Urine is produced in the kidneys, passing through the ureters to the
bladder, where it is temporarily stored and then released to the exterior
through the urethra.
General functions of urinary system:
1-Maintenance of homeostasis by production of urine, in which various
metabolic waste products are eliminates.
2- kidneys also regulate fluid and electrolytes balance of the body.
3- kidneys are the site of production of two hormones: rennin and
erythropoietin.
Rennin: participate in the regulation of blood pressure.
Erythropoietin: is a growth factor glycoprotein, which stimulate
erythrocyte production.
Kidneys: (Figure 1 left)
Each kidney has a concave medial border (the hilum) where nerves
enter, blood and lymph vessels enter and exit, and the ureter exit. Kidney
also contain convex lateral surface. The renal pelvis (the expanded
upper end of the ureter is divided into two or three major calyces).
Several small branches arise from each major calyces (the minor
calyces).
Each kidney divided into outer region (cortex) and inner region
(medulla). In humans, the renal medulla consists of 8-10 medullary
pyramids (conical or pyramidal structures). Medullary rays extended
from the base of each medullary pyramid (parallel arrays of kidney
tubules). Medullary rays then, penetrate kidney cortex.
Kidney nephron: (Figure 1 right)
Each kidney composed of 1-4 million nephron. Which are the functional
unites of the kidney.
1
, Each nephron consist’s of : 1-renal corpuscle; 2-proximal convoluted
tubule; 3- thin and thick limps of Henle’s loop; 4-distal convoluted
tubule; and 5-the collecting tubule and collecting duct.
Renal corpuscles: (Figure 2)
Each renal corpuscle is about 200µm in diameter, and consists of tuft of
capillaries (the glomerulus), surrounded by a double walled epithelial
capsule (Bowman’s capsule). The internal layer (the visceral layer) of
Bowman’s capsule envelops capillaries of the glumerulus. The external
layer forms the outer limit of the renal corpuscle and is called the
parietal layer. Between the two layers of Bowman’s capsule is the
urinary space.
Each renal corpuscle has a vascular pole (where the afferent
arteriole enter and the efferent arteriole leave; and urinary pole
(where the proximal convoluted tubule begin.
After entering renal corpuscle, the afferent arteriole usually divided
into two to five branches, each subdivided into capillaries and forming
the renal glomerulus.
The parietal layer of Bowman’s capsule consists of a simple squamous
epithelium which is changes to simple cuboidal or low columnar
epithelium at the urinary pole. The visceral layer of bowman’s capsule is
modified to form the podocytes, these cells have a body from which
arise several primary processes. Each primary processes give rise to
secondary processes, which is called pedicels, that embrace the
capillaries of the glomerulus.
2
