The urinary system
Urinary system is closely associated with the reproductive system. In many animals, the eggs
and sperm are emitted through the urinary tract, and the two systems have a shared embryonic
development and adult anatomical relationship. the urinary and reproductive systems are often
collectively called the urogenital system.
The urinary system consists of six principal organs: two kidneys, two ureters, the urinary bladder,
and the urethra.
Nitrogenous wastes
A waste is any substance that is useless to the body or present in excess of the body’s needs. A
metabolic waste, is a waste substance produced by the body. The food residue in feces, for example,
is a waste but not a metabolic waste, since it was not produced by the body and never entered the
body tissues.
Among the most toxic of our metabolic wastes are small nitrogen-containing compounds called
nitrogenous wastes
Other nitrogenous wastes in the urine include uric acid and creatinine, produced by the catabolism
of nucleic acids and creatine phosphate respectively. The level of nitrogenous waste in the blood is
typically expressed as blood urea nitrogen ( BUN). Normal concentration of blood 10 to 20 mg/l. an
elevated bun is called azotemia indicate renal insufficiency. It can progress to uraemia, a syndrome
of diarrhoea, vomiting, dyspnea and cardiac arrhythmia stemming from the toxicity of the
nitrogenous wastes.
,Excretion: is the process of separating wastes from the body fluids and eliminating them from the
body.
1.The respiratory system excretes co2, small amounts of other gases and water.
2.The integumentary system excretes water, inorganic salts, lactate, and urea in the sweat.
3.The digestive system not only eliminates food residue (which is not a process of excretion) but
also actively excretes water, salts, carbon dioxide, lipids, bile pigments, cholesterol, and other
metabolic wastes.
4. The urinary system excretes a broad variety of metabolic wastes, toxins, drugs, hormones, salts,
hydrogen ions, and water.
Anatomy of kidney
Position and associated structure:
The kidneys lie against the posterior abdominal wall at the level of vertebrae T12 to L3. rib 12
crosses the approximate middle of the left kidney. The kidneys are retroperitoneal.
Gross anatomy:
Each kidneys weights about 150 gm and about 11 cm long, 6cm wide and 3cm thick. The lateral
surface is convex and the medial surface is concave and has a slit, the hilum, that admits the renal
nerves, blood vessels, lymphatics and ureter. The kidney is protected by 3 layers.
1. renal fascia – immediately deep to the parietal peritoneum, binds the kidney and associated
organs to the abdominal wall.
2. perirenal fat capsule – a layer of adipose tissue, cushion the kidney and holds it in place
3. fibrous capsule - encloses the kidney like a cellophane wrapper and protect it from trauma and
infection.
the kidneys drop about 3 cm when one goes from lying down to standing, as when getting out of
bed in the morning. The renal parenchyma—the glandular tissue that forms the urine—appears C-
shaped in frontal section. It encircles a medial cavity, the renal sinus, occupied by blood and
lymphatic vessels, nerves, and urine-collecting structures. The parenchyma is divided into two
zones: an outer renal cortex about 1 cm thick and an inner renal medulla facing the sinus.
Extensions of the cortex called renal columns project toward the sinus and divide the medulla into
6 to 10 renal pyramids. Each pyramid is conical, with a broad base facing the cortex and a blunt
point called the renal papilla facing the sinus. One pyramid and the overlying cortex constitute one
lobe of the kidney. The papilla of each renal pyramid is nestled in a cup called a minor calyx2(CAY-
lix), which collects its urine. Two or three minor calyces (CAY-lih-seez) converge to form a major
calyx, and two or three major calyces converge in the sinus to form the funnel-like renal pelvis.
Renal circulation
Kidney receive about 1.2 liters of blood per minutes or 21 % of cardiac output. Each kidney is
supplied by a renal artery arising from the aorta. The renal artery divides into a few segmental
arteries, further divides int a few interlobar arteries. and travels between the pyramids toward the
corticomedullary junction, the boundary between the cortex and medulla. Along the way, it branches
again to form arcuate arteries. Each arcuate artery gives rise to several cortical radiate arteries,
which pass upward into the cortex. A series of afferent arterioles arise and supplies one functional
unit of the kidney called nephron. The afferent arteriole leads to a ball of capillaries called a
glomerulus. enclosed in a sphere called the glomerular capsule. Blood leaves the glomerulus by
, way of an efferent arteriole. The efferent arteriole usually leads to a plexus of peritubular
capillaries. A network around another part of the nephron, the renal tubule. The renal tubule
reabsorbs most of the water and solutes that filtered out of the blood at the glomerulus and returns
these to the bloodstream by way of these peritubular capillaries. The peritubular capillaries carry it
away to the cortical radiate veins, arcuate veins, interlobar veins, and the renal vein, in that
order. The renal medulla receives only 1% to 2% of the total renal blood flow, supplied by a network
of vessels called the vasa recta. the efferent arterioles descend immediately into the medulla and
give rise to the vasa recta instead of peritubular capillaries. Capillaries of the vasa recta are wedged
into the tight spaces between the medullary parts of the renal tubule, and carry away water and
solutes reabsorbed by those sections of the tubule.
nephron
each kidney has about 1.2 million nephrons. Each nephron is composed of 2 principal parts. A renal
corpulse and a renal tubule.
Renal corpulses: consists of glomerulus and 2 layered glomerular capsule that encloses it. The
parietal (outer) layer is a simple squamous epithelium and visceral (inner) consists of elaborate cells
called podocytes. The 2 layers are separated by capsular space. Opposite sides of the renal
corpuscle are called the vascular and urinary poles. At the vascular pole, the afferent arteriole enters
the capsule, bringing blood to the glomerulus, and the efferent arteriole leaves the capsule and
carries blood away. At the urinary pole, the parietal wall of the capsule turns away from the corpuscle
and gives rise to the renal tubule.
Urinary system is closely associated with the reproductive system. In many animals, the eggs
and sperm are emitted through the urinary tract, and the two systems have a shared embryonic
development and adult anatomical relationship. the urinary and reproductive systems are often
collectively called the urogenital system.
The urinary system consists of six principal organs: two kidneys, two ureters, the urinary bladder,
and the urethra.
Nitrogenous wastes
A waste is any substance that is useless to the body or present in excess of the body’s needs. A
metabolic waste, is a waste substance produced by the body. The food residue in feces, for example,
is a waste but not a metabolic waste, since it was not produced by the body and never entered the
body tissues.
Among the most toxic of our metabolic wastes are small nitrogen-containing compounds called
nitrogenous wastes
Other nitrogenous wastes in the urine include uric acid and creatinine, produced by the catabolism
of nucleic acids and creatine phosphate respectively. The level of nitrogenous waste in the blood is
typically expressed as blood urea nitrogen ( BUN). Normal concentration of blood 10 to 20 mg/l. an
elevated bun is called azotemia indicate renal insufficiency. It can progress to uraemia, a syndrome
of diarrhoea, vomiting, dyspnea and cardiac arrhythmia stemming from the toxicity of the
nitrogenous wastes.
,Excretion: is the process of separating wastes from the body fluids and eliminating them from the
body.
1.The respiratory system excretes co2, small amounts of other gases and water.
2.The integumentary system excretes water, inorganic salts, lactate, and urea in the sweat.
3.The digestive system not only eliminates food residue (which is not a process of excretion) but
also actively excretes water, salts, carbon dioxide, lipids, bile pigments, cholesterol, and other
metabolic wastes.
4. The urinary system excretes a broad variety of metabolic wastes, toxins, drugs, hormones, salts,
hydrogen ions, and water.
Anatomy of kidney
Position and associated structure:
The kidneys lie against the posterior abdominal wall at the level of vertebrae T12 to L3. rib 12
crosses the approximate middle of the left kidney. The kidneys are retroperitoneal.
Gross anatomy:
Each kidneys weights about 150 gm and about 11 cm long, 6cm wide and 3cm thick. The lateral
surface is convex and the medial surface is concave and has a slit, the hilum, that admits the renal
nerves, blood vessels, lymphatics and ureter. The kidney is protected by 3 layers.
1. renal fascia – immediately deep to the parietal peritoneum, binds the kidney and associated
organs to the abdominal wall.
2. perirenal fat capsule – a layer of adipose tissue, cushion the kidney and holds it in place
3. fibrous capsule - encloses the kidney like a cellophane wrapper and protect it from trauma and
infection.
the kidneys drop about 3 cm when one goes from lying down to standing, as when getting out of
bed in the morning. The renal parenchyma—the glandular tissue that forms the urine—appears C-
shaped in frontal section. It encircles a medial cavity, the renal sinus, occupied by blood and
lymphatic vessels, nerves, and urine-collecting structures. The parenchyma is divided into two
zones: an outer renal cortex about 1 cm thick and an inner renal medulla facing the sinus.
Extensions of the cortex called renal columns project toward the sinus and divide the medulla into
6 to 10 renal pyramids. Each pyramid is conical, with a broad base facing the cortex and a blunt
point called the renal papilla facing the sinus. One pyramid and the overlying cortex constitute one
lobe of the kidney. The papilla of each renal pyramid is nestled in a cup called a minor calyx2(CAY-
lix), which collects its urine. Two or three minor calyces (CAY-lih-seez) converge to form a major
calyx, and two or three major calyces converge in the sinus to form the funnel-like renal pelvis.
Renal circulation
Kidney receive about 1.2 liters of blood per minutes or 21 % of cardiac output. Each kidney is
supplied by a renal artery arising from the aorta. The renal artery divides into a few segmental
arteries, further divides int a few interlobar arteries. and travels between the pyramids toward the
corticomedullary junction, the boundary between the cortex and medulla. Along the way, it branches
again to form arcuate arteries. Each arcuate artery gives rise to several cortical radiate arteries,
which pass upward into the cortex. A series of afferent arterioles arise and supplies one functional
unit of the kidney called nephron. The afferent arteriole leads to a ball of capillaries called a
glomerulus. enclosed in a sphere called the glomerular capsule. Blood leaves the glomerulus by
, way of an efferent arteriole. The efferent arteriole usually leads to a plexus of peritubular
capillaries. A network around another part of the nephron, the renal tubule. The renal tubule
reabsorbs most of the water and solutes that filtered out of the blood at the glomerulus and returns
these to the bloodstream by way of these peritubular capillaries. The peritubular capillaries carry it
away to the cortical radiate veins, arcuate veins, interlobar veins, and the renal vein, in that
order. The renal medulla receives only 1% to 2% of the total renal blood flow, supplied by a network
of vessels called the vasa recta. the efferent arterioles descend immediately into the medulla and
give rise to the vasa recta instead of peritubular capillaries. Capillaries of the vasa recta are wedged
into the tight spaces between the medullary parts of the renal tubule, and carry away water and
solutes reabsorbed by those sections of the tubule.
nephron
each kidney has about 1.2 million nephrons. Each nephron is composed of 2 principal parts. A renal
corpulse and a renal tubule.
Renal corpulses: consists of glomerulus and 2 layered glomerular capsule that encloses it. The
parietal (outer) layer is a simple squamous epithelium and visceral (inner) consists of elaborate cells
called podocytes. The 2 layers are separated by capsular space. Opposite sides of the renal
corpuscle are called the vascular and urinary poles. At the vascular pole, the afferent arteriole enters
the capsule, bringing blood to the glomerulus, and the efferent arteriole leaves the capsule and
carries blood away. At the urinary pole, the parietal wall of the capsule turns away from the corpuscle
and gives rise to the renal tubule.
