Urinary system


The urinary system consists of the uropoetic organs, that is, in charge of elaborating the urine and storing it temporarily until the opportunity to be eliminated abroad. In urine we find uric acid, urea, sodium, potassium, bicarbonate, etc.

This apparatus may be divided into secretory organs & #8211; that produce urine & #8211; and excretory organs & #8211; who are in charge of processing the drainage of urine out of the body.

The urinary organs include the kidneys (2), which produce the urine, the ureters (2) or ducts, which carry the urine to the bladder (1), where it is held for some time, and the urethra (1), through the which is expelled from the body.

In addition to the kidneys, the remaining structures of the urinary system act as a pipeline constituting the urinary tract pathways. These structures - ureters, bladder and urethra - do not change urine along the way, but rather store and conduct urine from the kidney to the outside.



The kidneys are even, bean-bean-shaped organs located just above the waist between the peritoneum and the posterior wall of the abdomen. Its coloration is reddish brown.

The kidneys are located on either side of the spine, in front of the upper region of the posterior abdominal wall, extending between the 11th rib and the transverse process of the 3rd lumbar vertebra. They are described as retroperitoneal organs, because they are positioned behind the peritoneum of the abdominal cavity.

KIDNEY The kidneys are covered by the peritoneum and surrounded by a mass of fat and loose areolar tissue. Each kidney is about 11.25 cm long, 5 to 7.5 cm wide and slightly more than 2.5 cm thick. The left is a little longer and narrower than the right. Adult kidney weight ranges from 125 to 170 g; in the adult woman, between 115 to 155 g. The right kidney usually lies slightly below the left kidney due to the large size of the right lobe of the liver.

In the concave medial margin of each kidney is a vertical slit - the RENAL HILO - where the renal artery enters and the renal vein and pelvis leave the renal sinus. In the hilum, the renal vein is anterior to the renal artery, which is anterior to the renal pelvis. The renal hilum is the entrance to a space within the kidney.

The renal sinus, which is occupied by the renal pelvis, calyxes, nerves, blood and lymphatic vessels and a variable amount of fat.

External Kidney Configuration:

Each kidney has two faces, two edges and two ends.

FACES (2) & #8211; Previous and next. Both are smooth, but the former is more flat and the latter flatter.

EDGES (2) & #8211; Medial (concave) and Lateral (convex).

ENDS (2) & #8211; Upper (Adrenal Gland) and Lower (L3 level).

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Internal Kidney Configuration:

In a frontal section through the kidney, two distinct regions are revealed: a reddish smooth-textured area called the renal cortex and a deep reddish-brown area called the renal medulla. The medulla consists of 8-18 cuneiform structures, the Kidney Pyramids. The base (widest end) of each pyramid looks at the cortex, and its apex (narrowest end), called the renal papilla, points to the kidney hilum. The parts of the renal cortex that extend between the renal pyramids are called renal columns.

Together, the renal cortex and renal medulla pyramids constitute the functional part, or parenchyma of the kidney. In the parenchyma are the functional units of the kidneys - about 1 million microscopic structures called Nephron. The urine, formed by the nephrons, drains into the large papillary ducts, which extend along the renal papillae of the pyramids.


The ducts drain into structures called Smaller and Larger Kidney Goblets. Each kidney has 8-18 smaller chalices and 2-3 larger chalices. The smaller renal chalice receives urine from the papillary ducts of a renal papilla and transports it to a larger renal chalice. From the larger renal chalice, urine drains into the large cavity called Renal Pelvis and then out at Ureter, to the urinary bladder. The renal hilum expands into a cavity in the kidney called the renal sinus.

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.


The nephron is the morphofunctional unit or the urine producing unit of the kidney. Each kidney contains about 1 million nephrons.

The shape of the nephron is peculiar, unmistakable, and admirably suited to its function of producing urine.

The nephron is made up of two main components:

1. Renal Corpuscle:

 Glomerular Capsule (from Bowman);

 Glomerulus - network of twisted blood capillaries within the glomerular capsule

2. Renal Tubule:

 Proximal contorted tubule;

 Nephron Handle (by Henle);

 Distal contorted tubule;

 Collecting tubule.

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Kidney Functions

The kidneys perform the main work of the urinary system, with the other parts of the system acting mainly as passageways and storage areas. With blood filtration and urine formation, the kidneys contribute to homeostasis of body fluids in a number of ways.

Kidney Functions include:

 Regulation of the ionic composition of blood;

 Maintenance of blood osmolarity;

 Regulation of blood volume;                                                                    

 Blood pressure regulation;                                                                                                                

 PH regulation of blood;                                                                                            

 Hormone release;

 Regulation of blood glucose level;

 Excretion of waste and foreign substances.


Adrenal Glands

The adrenal (adrenal) glands are located between the superomedial faces of the kidneys and the diaphragm. Each adrenal gland, surrounded by a fibrous capsule and a fat cushion, has two parts: the cortex and the adrenal medulla, both producing different hormones.

The cortex secretes hormones essential to life, while spinal hormones are not essential to life. The adrenal medulla can be removed without causing life-threatening effects.

The adrenal medulla secretes two hormones: epinephrine (adrenaline) and norepinephrine. The adrenal cortex secretes the steroids..


 They are two tubes that carry urine from the kidneys to the bladder.

URETERSPoorly sized organs, the ureters are less than 6 mm in diameter and 25 to 30 cm in length.

Renal pelvis is the upper end of the ureter, located inside the kidney.

Descending obliquely downward and medially, the ureter travels in front of the posterior abdominal wall, then penetrates the pelvic cavity, opening into the ureter ostium on the floor of the urinary bladder.

Because of its course, two parts of the ureter are distinguished: abdominal and pelvic. The ureters are capable of performing rhythmic contractions called peristalsis. Urine moves along the ureters in response to gravity and peristalsis.


 The urinary bladder acts as a temporary reservoir for urine storage. When empty, the bladder is located inferiorly to the peritoneum and posterior to the pubic symphysis: when full, it rises to the abdominal cavity.

It is a hollow, elastic muscular organ that, in men It lies directly anterior to the rectum.


Nas women It is in front of the vagina and below the uterus.


When the bladder is full, its inner surface becomes smooth. A triangular area on the posterior surface of the bladder shows no wrinkles. This area is called bladder trine and is always smooth. This trine is limited by three vertices: the entry points of both ureters and the exit point of the urethra. The trigone is clinically important because infections tend to persist in this area.


The urinary bladder outlet contains the sphincter muscle called the internal sphincter, which contracts involuntarily, preventing emptying. Inferior to the sphincter muscle, surrounding the upper urethra, is the external sphincter, which is voluntarily controlled, allowing resistance to the need to urinate.

The average urinary bladder capacity is 700 - 800 ml; It is smaller in women because the uterus occupies the space immediately above the bladder.

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.



The urethra is a tube that conducts urine from the bladder to the external environment and is lined with mucosa that contains large amount of mucus secreting glands. The urethra opens outwards through the outer ostium of the urethra.

The urethra is different between the two sexes.

Male and female urethra differ in their path. In women, the urethra is short (3.8 cm) and is exclusively part of the urinary system. Its external ostium is located anterior to the vagina and between the smaller lips. In men, the urethra is part of the urinary and reproductive systems. Measuring about 20 cm, it is much longer than the female urethra. When the male urethra leaves the bladder, it passes through the prostate and extends along the length of the penis. Thus, the male urethra acts for two purposes: it conducts urine and sperm.

Portions of Men's UrethraMen's Urethra

The male urethra extends from the internal urethral orifice in the urinary bladder to the external urethral orifice at the tip of the penis. It has double curvature in the common state of relaxation of the penis. It is divided into three parts: the Prostatic, a Membrane and the Spongy, whose structures and relations are essentially different. In the male urethra there is a tiny slit-shaped opening, an ejaculatory duct.

Portions of Men's Urethra

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Female Urethra

It is a narrow membranous canal extending from the bladder to the external orifice in the vestibule. It is placed dorsally to the pubic symphysis, included in the anterior wall of the vagina, and slanting downwards and forwards; It is slightly curved, with the concavity directed forward. Its diameter, when not dilated, is about 6 mm. Its external orifice is immediately in front of the vaginal opening and about 2.5 cm dorsally to the clitoris glans. Many small urethral glands open in the urethra. The largest of these are the paraurethral glands, whose ducts flow exactly into the urethral ostium.

Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.