Urinary System:The urinary system consists of the paired kidney, ureters, bladder, and
urethra this system contributes of the maintenance at homeostasis by a
complex
process
that involves filtration,active absorption passive absorption, and:
secretion . the result is the production of urine in wich various
metabolic waste products are eliminated.
Urine produced in the kidneys passes through the
to the bladder
.where it is temporarily stored and then released of the exterior through
the urethra the tow kidneys produce about 125 ml of filtrate per minute of
this amount. 124 ml is absorbed in the organ, and only 1 ml is released
into the urelers as urine.
Kidney: cortex and pyramidal
The kidney is subdivided and outer region,the cortex and an inner region,
the
medulla. externally ,the cortex is covered with aconective tissue capsule
in the cortex the convoluted tubules glomeruli, straight tubules and
medullary rays, are found, the cortex also contain renal corpuscles
(glomerular or bowman capsule and glomeruli), the glomerulus is a tuft
of capillaries formed from the afferent glomerular arterioles and
supported by fine connective tissue.
The visceral layer of the glomerular capsule consists of modified
epithelial cells called the podocytes, these cells closely follow the
contours of the glomerulus and invest the capillary tuft. At the vascular
pole the visceral epithelium reflects to become the parietal layer of the
glornerular capsules. the space between the visceral layer and the parietal
layer of the capsule is the capsular space,which become continuous with
the lumen of proximal convoluted tubule at the urinary pole Numerous
tubules sectioned in various planes, lie adjacent to the renal
corpuscles the tubules are primarily of two types the proximal convoluted
and distal convoluted, these tubules are the initial and terminal segments
of nephron, respectively. the proximal convoluted tubules are numerous
in the cortex, exhibit a small ,irregular lumen,and contain a single layer
of large cuboidal cells with intensely eosinophilic mgranular cytoplasm
the well— developed brush borders are present but are not always well
preserved in sections.
Distal convoluted tubules are fewer in number and-exhibit a larger lumen
with smaller ,cuboidal cells. The cytoplasm stanis less intensely and the
brush borders are not present also the number of these cells are more than
those in prximal tubules.
The medulla:
The medulla contain only straight portion of tubules and thin segments of
loop of Henle. Illustrated in the outer medullary region are thin segments
of loops of Henle lined with squamous epithelium straight segments ofdistal tubules(ascending have simple cuboidal ep.) and straight segments
of proximal tubule (descensing have simple cuboidal ep.) and collectingtubules, in medulla contain the terminal portions of the collecting tubules,
the papillary ducts ,these ducts have large diameters and wide lumina and
are lined by tall, pale— staining columnar cells.
Juxtaglomerular Apparatus:
Adjacent to the renal corpuscle the tunica media of the afferent arteriole
has modified smooth muscle. These cells are called juxtaglomerular cells
and-have cytoplasm full of secretory granules secretion of JG cells play a
role in the maintenance of blood pressure. The macula densa of the distal
convoluted tubule is, usually located near the region of the afferent
arteriole that contain the JG cells ;together, this portion of the arteriole
and macula densa form the JG apparatus. the JG cells produce the
enzyme rennin which regulate. the blood pressure.
Bladder & Urinary passages
The bladder and the urinary passages store the urine formed in the kidney
and conduct it to the exterior .the calyces ,renal pelvis ,ureter, and urinary
bladder have the same basic histological structure, with the walls of the
ureters becoming gradually thicker as proximitry. to the bladder
increases.
The mucosa of the organs consists of transitional epithelium and lamina
propria of loose—to- dense connective tissue. Surrounding the lumina
proporia of these organs is a dense woven sheath of smooth muscule.
Urethra:
The urethra is a tube that, carries the urine from the bladder to the
exterior.in man , the sperm also pass through it during ejaculation .. in
woman the urethra is exclusively a urinary oragen