Excretory System Report

EXCRETORY SYSTEM
Members:
Samuel Rosales Romao
Elias Raul Roca Castedo
Leyla Verónica Araúz Herrera
Specialty: Physical Education and Sports 3rd Year

Training unit: Exercise Physiology Biochemistry and Sports Nutrition
Teacher: Lic. Edwin Calzada
Date: 11/12/2021
Santa Cruz - Bolivia

Introduction:
Generalities
Excretory system
The excretory system is one of the systems of the human body, and is responsible for
eliminating substances that our body does not need once it has taken advantage of the nutrients
that they have provided. This system is of great importance for the body, since it allows the
elimination of toxins and waste and, by extension, the correct functioning of the body.
Waste elimination occurs mainly through three routes: urination (expulsion of urine), breathing
(absorption of oxygen and expulsion of carbon dioxide) and sweating (elimination of toxins
through the skin).
Parts
The excretory system is made up of four organs or structures: the urinary system (formed, in
turn, by four structures that we will see below), the skin, the lungs and the liver.
We are going to see in detail the four organs that make up the excretory system below, knowing
their anatomy and functions.
urinary system
The urinary system (also generically called the “excretory system”) is made up of the following
structures: the kidneys, ureters, bladder and urethra. The urinary system has a double function:
producing and excreting urine. Urine is basically made up of water, although it also contains
traces of other substances, such as urea (a toxic substance).
Urine is produced in the kidneys, and once formed, it descends from the kidneys to the bladder
through tubes called ureters (there are two, one for each kidney).
Once in the bladder, urine accumulates until the person feels the need to urinate (this need
arises from a series of nervous impulses, which detect that the bladder is beginning to fill). A
curious fact is that although the bladder has a storage capacity of up to one liter, the need to
urinate begins to be felt when about 400 or 500 cubic centimeters of urine accumulate.
Another interesting fact is that urine cannot return to the kidneys once it is in the bladder; This
occurs because the bladder contains a series of valves that block urine from entering the
ureters.
Let's see what each of these already mentioned structures that make up the urinary system
consists of.
Kidneys
The kidneys are two bean-shaped organs, each about the size of a fist. They are located just
below the ribcage (ribs), one on each side of the spine.
Healthy kidneys filter about half a cup of blood per minute, removing waste and excess water to
produce urine. Urine flows from the kidneys to the bladder through two thin muscular tubes
called ureters, one on each side of the bladder. The bladder stores urine. The kidneys, ureters,
and bladder are part of the urinary tract .
Why are kidneys important?
The kidneys remove waste and excess fluid from the body. The kidneys also remove acid
produced by the body's cells and maintain a healthy balance of water, salts, and minerals (such
as sodium, calcium, phosphorus, and potassium) in the blood.
Without this balance, nerves, muscles, and other tissues in the body may not function normally.
The kidneys also produce hormones that help
 control blood pressure
 produce red blood cells NIH external link
 keep bones strong and healthy

How do the kidneys work?
Each kidney is made up of approximately one million filtration units called nephrons. Each
nephron includes a filter, called a glomerulus, and a tubule. Nephrons function through a two-
step process: the glomerulus filters the blood and the tubule returns necessary substances to
the blood and removes waste.
Each nephron has a glomerulus that filters the

blood and a tubule that returns necessary
substances to the blood and removes extra
waste. Waste and excess water become urine.
The glomerulus filters the blood
As blood flows to each nephron, it enters a group of tiny blood vessels: the glomerulus. The thin
walls of the glomerulus allow smaller molecules, waste, and fluids, mostly water, to pass into the
tubule. Larger molecules, such as proteins and blood cells, remain in the blood vessel.
The tubule returns necessary substances to the blood and removes waste
A blood vessel flows next to the tubule. As the filtered fluid moves along the tubule, the blood
vessel reabsorbs 99 percent of the water, along with the minerals and nutrients the body needs.
The tubule helps remove excess acid from the blood. The remaining fluid and waste in the
tubule becomes urine.
How does blood flow through the kidneys?
Blood flows to the kidney through the renal artery. This large blood vessel branches into smaller
and smaller blood vessels until the blood reaches the nephrons. In the nephron, blood is filtered
by the tiny blood vessels of the glomeruli and then flows out of the kidney through the renal vein.
Blood circulates through the kidneys many times a day. In a single day, the kidneys filter about
150 quarts of blood. Most of the water and other substances that are filtered through the
glomeruli are returned to the blood by the tubules. Only 1 to 2 quarts become urine.
Blood flows to the kidneys through the renal artery and

out through the renal vein. The ureter carries urine from
the kidney to the bladder.
Ureters
The ureters are two hollow tubes that connect the kidneys to the back of the bladder.
• Approximate length of 30 centimeters. (the left one is slightly longer than the right one)
Structure
Structure The wall of the ureters is made up of three layers:
• The outermost is the adventitia (composed of connective tissue with abundant blood
vessels, lymphatics and nerves).
• The intermediate lamina or muscular layer (formed by smooth muscle fibers)
• The innermost layer or mucosa (made up of lining epithelium).
The Ureter is not a tube of uniform caliber:
• It begins in the renal pelvis with a funnel 4 to 9 cm long and 8 to 10 mm in diameter;
• The neck of the ureter follows. Hence a long lumbar spindle, which progressively
swells from 9 to 15 mm in diameter and reaches a length of 8 to 9 cm;
• Then it progressively decreases in volume to the iliac vessels.
• There is a second widening, the pelvic spindle, which routes the ureter to the bladder
wall, opens through the urethral meatus.
Function
Function The ureters act similarly to the esophagus. Both are only passageways, but not
passive. Through a series of contractions and relaxations of its walls, the tubular
structure advances its contents forward. The ureters distill urine drop by drop into the
bladder located at the bottom of the puvis, where it is stored until it is expelled to the
exterior through the urethra.
At the end of the ureter at its junction with the urinary bladder are the ureteral orifices,
which allow the passage of urine. These act as valves that regulate the passage of
content, in a single direction. However, they do not function like other body sphincters:
preventing reflux. Therefore, if there is any defect or anomaly in these conducting tubes
and in the ureteral orifices, it is most likely that urine will return to the kidneys, generating
complications.
muscle layer
Its muscle fibers are arranged intertwined in three layers that allow peristalsis of the ureter from
the kidneys to the bladder.
 Internal longitudinal layer. They are sets of muscle fibers that move.
 Intermediate muscular layer , whose fibers are circular and arranged forming powerful rings
like a sphincter.
 External longitudinal layer formed at the expense of fibers
Bladder
Definition
The bladder is a hollow organ in the lower abdomen where urine is stored. There are many
conditions that can affect bladder function. Among the most common are:
 Cystitis: an inflammation of the bladder, usually caused by an infection
 Urinary incontinence : loss of bladder control
 Overactive bladder : a condition that causes the bladder to pass urine when it doesn't have to
 Interstitial cystitis – a chronic problem that causes pain in the bladder and urgency to urinate
 Bladder cancer :
Doctors diagnose bladder diseases using different tests. These include urinalysis , x-rays, and
examinations of the bladder wall with an instrument called a cystoscope. Treatment depends on
the cause of the problem. It may include medicines and, in severe cases, surgery.
 When the bladder is full, it swells into a round shape.

 The nerves in the bladder are responsible for sending the order to the brain to urinate.
 The brain tells the bladder muscles to contract, while it causes the sphincters to relax.
 Urine leaves the bladder through the urethra and urination (or the act of urinating) occurs.
What is the bladder ?
 The bladder is a hollow, balloon-shaped muscular organ.

 It is located above the pelvis , and is supported by ligaments attached to the pelvic bones
and other organs.
 Its function is to store urine .
 The bladder swells when full , but is small when empty.
If the urinary system is healthy, the bladder can easily hold up to 2 cups of urine for 2 to 5
hours.
Urethra
What is the urethra?

The urethra is a tube-shaped duct that allows urine to escape from the urinary bladder to the
outside. The act of eliminating or expelling urine is called urination. In men, in addition to this
function, it is responsible for the transfer of semen from the seminal vesicles to the outside
during ejaculation.
Therefore, the urethra is different in men and women, both in function and in some
characteristics, as we will see later.
Urethra function
As we have already mentioned previously, the main function of the urethra is to conduct urine
outside the body, from the bladder to the urinary meatus. The urinary meatus in men is located
at the tip of the glans while in women it is located in the vestibule of the vulva, between the
opening of the vagina and the clitoris.
In men, the urethra also has another function: to conduct semen from the seminal vesicles to the
outside during ejaculation . But how does the release of these two substances occur through
the same duct? During sexual intercourse, the flow of urine from the bladder to the urethra is
"blocked" and leaves the duct free for the semen to exit the seminal vesicles and, through the
urethra and, crossing the prostate (an organ that is only found in males), it reaches the exterior
through the urinary meatus.
Features of the urethra

The urethra is an organ that, as we have already seen, varies greatly between men and
women, so its characteristics also vary greatly.
On the one hand, the female urethra is much shorter than the male urethra . While the
urethra in women can measure approximately 4.5 cm, the urethra in men can measure about
20 cm . This is because in men the urinary meatus is displaced to the tip of the glans and the
urethra has to run from the end of the urinary bladder to the end of the penis.
In women, the urinary meatus is much closer to the bladder, in the vestibule of the vagina, just
above the opening of the vagina. Due to its short length, in women it is more common for
pathogenic microorganisms to reach the urethra and give rise to an infection, which is medically
called urethritis and is commonly known as a urine infection .
Another characteristic that differentiates a man's urethra from that of a woman is that in the latter
the prostate is not crossed. The prostate is an organ that is only found in men since its function
is to generate most of the compounds that form seminal fluid, a substance that joins with sperm
and makes up semen.
Finally, the female and male urethra are different in the parts that compose them: while in
women we find four regions (intramural, pelvic, membranous and perineal), in men three
regions are distinguished (prostatic, membranous and spongy).
Similarities between the male and female urethra

A characteristic common to both sexes is the existence of two sphincters in the urethra. Just at
the exit of the urinary bladder there is a first sphincter, formed by circular smooth muscle and
whose control is involuntary. This internal urethral sphincter is responsible for the sensation of
urination.
Further ahead of the duct, another sphincter appears, the external urethral sphincter , which is
formed by striated muscle and this does allow us to control urination since it is voluntary. The
external urethral sphincter is located, in both sexes, in the membranous urethral region (which in
men is located at the base of the penis).
These two sphincters are joined by the levator ani muscle, which also helps control urination
since it is a constrictor of the urethra.
Physiology
Urine, Urine Toxicity
Conclusion:
Bibliography:
https://www.niddk.nih.gov/health-information/informacion-de-la-salud/enfermedades-
rinones/rinones-functionación
https://es.slideshare.net/SuhallMtz/urteres-54319855
 Wikipedia (May 20, 2019). Urethra. Recovered from https://es.wikipedia.org/wiki/Uretra
 Know-it-all (sf). Anatomy of the human urethra. Retrieved from

http://www.sabelotodo.org/anatomia/uretra.html
 Center for Reconstructive Urology and Urethral Surgery (sf). What is the Urethra?
Recovered from http://www.uretra.cl/sitio/la-uretra/ique-es-la-uretra
https://www.saberespractico.com/anatomia/cual-es-la-funcion-de-la-uretra/

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EXCRETORY SYSTEM

Specialty: Physical Education and Sports 3rd Year

Santa Cruz - Bolivia

Why are kidneys important?

The kidneys also produce hormones that help

 control blood pressure

 produce red blood cells NIH external link

 keep bones strong and healthy

Each nephron has a glomerulus that filters the

How does blood flow through the kidneys?

Blood flows to the kidneys through the renal artery and

 When the bladder is full, it swells into a round shape.

What is the bladder ?

 The bladder is a hollow, balloon-shaped muscular organ.

What is the urethra?

Features of the urethra

Similarities between the male and female urethra

 Wikipedia (May 20, 2019). Urethra. Recovered from https://es.wikipedia.org/wiki/Uretra

 Know-it-all (sf). Anatomy of the human urethra. Retrieved from

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