MODULE 17.

LESSON PROPER

URINARY SYSTEM

The kidney and urinary systems help the body to get rid of liquid waste called urea. They also
help to keep chemicals (such as potassium and sodium) and water in balance. Urea is produced
when foods containing protein (such as meat, poultry, and certain vegetables) are broken down in
the body. Urea is carried in the blood to the kidneys. This is where it is removed, along with water
and other wastes in the form of urine.

FUNCTIONS OF THE URINARY SYSTEM

The function of the kidneys are as follows:

1. Filter. Every day, the kidneys filter gallons of fluid from the bloodstream.
2. Waste processing. The kidneys then process this filtrate, allowing wastes and excess
ions to leave the body in urine while returning needed substances to the blood in just the
right proportions.
3. Elimination. Although the lungs and the skin also play roles in excretion, the kidneys bear
the major responsibility for eliminating nitrogenous wastes, toxins, and drugs from the
body.
4. Regulation. The kidneys also regulate the blood’s volume and chemical makeup so that the
proper balance between water and salts and between acids and bases is maintained.
5. Other regulatory functions. By producing the enzyme renin, they help regulate blood
pressure, and their hormone erythropoietin stimulates red blood cell production in the bone
marrow.
6. Conversion. Kidney cells also convert vitamin D to its active form.

ANATOMY OF THE URINARY SYSTEM

The urinary system consists of two kidneys, two ureters, a urinary bladder, and a urethra. The
kidneys alone perform the functions just described and manufacture urine in the process, while the
other organs of the urinary system provide temporary storage reservoirs for urine or serve as
transportation channels to carry it from one body region to another.
 1. The Kidneys

The kidneys, which maintain the purity and constancy of our internal fluids, are perfect examples
of homeostatic organs.

• Location. These small, dark red organs with a kidney-bean shape lie against the dorsal body
wall in a retroperitoneal position (beneath the parietal peritoneum) in the superior lumbar
region; they extend from the T12 to the L3 vertebra, thus they receive protection from the
lower part of the rib cage.
• Positioning. Because it is crowded by the liver, the right kidney is positioned slightly lower
than the left.
• Size. An adult kidney is about 12 cm (5 inches) long, 6 cm (2.5 inches) wide, and 3 cm (1
inch) thick, about the size of a large bar of soap.
• Adrenal gland. Atop each kidney is an adrenal gland, which is part of the endocrine system
is a distinctly separate organ functionally.
• Fibrous capsule. A transparent fibrous capsule encloses each kidney and gives a fresh
kidney a glistening appearance.
• Perirenal fat capsule. A fatty mass, the perirenal fat capsule, surrounds each kidney and
acts to cushion it against blows.
• Renal fascia. The renal fascia, the outermost capsule, anchors the kidney and helps hold it
in place against the muscles of the trunk wall.

• Renal cortex. The outer region, which is light in color, is the renal cortex.
• Renal medulla. Deep to the cortex is a darker, reddish-brown area, the renal medulla.
• Renal pyramids. The medulla has many basically triangular regions with a striped
appearance, the renal, or medullary pyramids; the broader base of each pyramid faces
toward the cortex while its tip, the apex, points toward the inner region of the kidney.
• Renal columns. The pyramids are separated by extensions of cortex-like tissue, the renal
columns.
 • Renal pelvis. Medial to the hilum is a flat, basinlike cavity, the renal pelvis, which is
continuous with the ureter leaving the hilum.
• Calyces. Extensions of the pelvis, calyces, form cup-shaped areas that enclose the tips of
the pyramid and collect urine, which continuously drains from the tips of the pyramids into
the renal pelvis.
• Renal artery. The arterial supply of each kidney is the renal artery, which divides into
segmental arteries as it approaches the hilum, and each segmental artery gives off several
branches called interlobar arteries.
• Arcuate arteries. At the cortex-medulla junction, interlobar arteries give off arcuate
arteries, which curve over the medullary pyramids.
• Cortical radiate arteries. Small cortical radiate arteries then branch off the arcuate arteries
and run outward to supply the cortical tissue.

2. Nephrons

Nephrons are the structural and functional units of the kidneys.

• Nephrons. Each kidney contains over a million tiny structures called nephrons, and they
are responsible for forming urine.
• Glomerulus. One of the main structures of a nephron, a glomerulus is a knot of capillaries.
• Renal tubule. Another one of the main structures in a nephron is the renal tubule.
• Bowman’s capsule. The closed end of the renal tubule is enlarged and cup-shaped and
completely surrounds the glomerulus, and it is called the glomerular or Bowman’s capsule.
• Podocytes. The inner layer of the capsule is made up of highly modified octopus-like cells
called podocytes.
• Foot processes. Podocytes have long branching processes called foot processes that
intertwine with one another and cling to the glomerulus.
• Collecting duct. As the tubule extends from the glomerular capsule, it coils and twists
before forming a hairpin loop and then again becomes coiled and twisted before entering a
collecting tubule called the collecting duct, which receives urine from many nephrons.
• Proximal convoluted tubule. This is the part of the tubule that is near to the glomerular
capsule.
• Loop of Henle. The loop of Henle is the hairpin loop following the proximal convoluted
tubule.
• Distal convoluted tubule. After the loop of Henle, the tubule continues to coil and twist
before the collecting duct, and this part is called the distal convoluted tubule.
• Cortical nephrons. Most nephrons are called cortical nephrons because they are located
almost entirely within the cortex.
• Juxtamedullary nephrons. In a few cases, the nephrons are called juxtamedullary nephrons
because they are situated next to the cortex-medullary junction, and their loops of Henle
dip deep into the medulla.
• Afferent arteriole. The afferent arteriole, which arises from a cortical radiate artery, is the
“feeder vessel”.
• Efferent arteriole. The efferent arteriole receives blood that has passed through the
glomerulus.
• Peritubular capillaries. They arise from the efferent arteriole that drains the glomerulus.
 3. Ureters

The ureters do play an active role in urine transport.

• Size. The ureters are two slender tubes each 25 to 30 cm (10 to 12 inches) long and 6 mm
(1/4 inch) in diameter.
• Location. Each ureter runs behind the peritoneum from the renal hilum to the posterior
aspect of the bladder, which it enters at a slight angle.
• Function. Essentially, the ureters are passageways that carry urine from the kidneys to the
bladder through contraction of the smooth muscle layers in their walls that propel urine
into the bladder by peristalsis and is prevented from flowing back by small valve-like folds
of bladder mucosa that flap over the ureter openings.

4. Urinary Bladder

The urinary bladder is a smooth, collapsible, muscular sac that stores urine temporarily.

• Location. It is located retroperitoneally in the pelvis just posterior to the symphysis pubis.
• Function. The detrusor muscles and the transitional epithelium both make the bladder
uniquely suited for its function of urine storage.
• Trigone. The smooth triangular region of the bladder base outlined by these three openings
is called the trigone, where infections tend to persist.
• Detrusor muscles. The bladder wall contains three layers of smooth muscle, collectively
called the detrusor muscle, and its mucosa is a special type of epithelium, transitional
epithelium.
 5. Urethra

The urethra is a thin-walled tube that carries urine by peristalsis from the bladder to the outside of
the body.

• Internal urethral sphincter. At the bladder-urethral junction, a thickening of the smooth

muscle forms the internal urethral sphincter, an involuntary sphincter that keeps the urethra
closed when the urine is not being passed.
• External urethral sphincter. A second sphincter, the external urethral sphincter, is fashioned
by skeletal muscle as the urethra passes through the pelvic floor and is voluntarily
controlled.
• Female urethra. The female urethra is about 3 to 4 cm (1 1/2 inches) long, and its external
orifice, or opening, lies anteriorly to the vaginal opening.
• Male urethra. In me, the urethra is approximately 20 cm (8 inches) long and has three
named regions: the prostatic, membranous, and spongy (penile) urethrae; it opens at the tip
of the penis after traveling down its length.

PHYSIOLOGY OF THE URINARY SYSTEM

Every day, the kidneys filter gallons of fluid from the bloodstream. The normal physiology that
takes place in the urinary system are as follows:

URINE FORMATION

Urine formation is a result of three processes:

• Glomerular filtration. Water and solutes smaller than proteins are forced through the
capillary walls and pores of the glomerular capsule into the renal tubule.
• Tubular reabsorption. Water, glucose, amino acids, and needed ions are transported out of
the filtrate into the tubule cells and then enter the capillary blood.
• Tubular secretion. Hydrogen, potassium, creatinine, and drugs are removed from the
peritubular blood and secreted by the tubule cells into the filtrate.
CHARACTERISTICS OF URINE

In 24 hours, the marvelously complex kidneys filter some 150 to 180 liters of blood plasma through
their glomeruli into the tubules.

• Daily volume. In 24 hours, only about 1.0 to 1.8 liters of urine are produced.
• Components. Urine contains nitrogenous wastes and unneeded substances.
• Color. Freshly voided urine is generally clear and pale to deep yellow.
• Odor. When formed, urine is sterile and slightly aromatic, but if allowed to stand, it takes
on an ammonia odor caused by the action of bacteria on the urine solutes.
• pH. Urine pH is usually slightly acidic (around 6), but changes in body metabolism and
certain foods may cause it to be much more acidic or basic.
• Specific gravity. Whereas the specific gravity of pure water is 1.0, the specific gravity of
urine usually ranges from 1.001 to 1.035.
• Solutes. Solutes normally found in urine include sodium and potassium ions, urea, uric
acid, creatinine, ammonia, bicarbonate ions, and various other ions.

MICTURITION

Micturition or voiding is the act of emptying the bladder.

• Accumulation. Ordinarily, the bladder continues to collect urine until about 200 ml have
accumulated.
• Activation. At about this point, stretching of the bladder wall activates stretch receptors.
• Transmission. Impulses transmitted to the sacral region of the spinal cord and then back to
the bladder via the pelvic splanchnic nerves cause the bladder to go into reflex contractions.
• Passage. As the contractions become stronger, stored urine is forced past the internal
urethral sphincter into the upper part of the urethra.
• External sphincter. Because the lower external sphincter is skeletal muscle and voluntarily
controlled, we can choose to keep it closed or it can be relaxed so that urine is flushed from
the body.
 FEMALE REPRODUCTIVE SYSTEM

Women have the responsibility of bringing forth life into the world, hence the creation and the
function of the female reproductive system. This system performs a miracle from the conception
of life until the birth of the growing life within, and it is only proper to be introduced to the main
characters and supporting roles of this play.

INTERNAL STRUCTURES

1. OVARIES

The ovaries are the ultimate life-maker for the females.

• For its physical structure, it has an estimated length of 4 cm and width of 2 cm and is 1.5
cm thick. It appears to be shaped like an almond. It looks pitted, like a raisin, but is grayish
white in color.
• It is located proximal to both sides of the uterus at the lower abdomen.
• For its function, the ovaries produce, mature, and discharge the egg cells or ova.
• Ovarian function is for the maturation and maintenance of the secondary sex characteristics
in females.
• It also has three divisions: the protective layer of epithelium, the cortex, and the central
medulla.
 2. FALLOPIAN TUBES

The fallopian tubes serve as the pathway of the egg cells towards the uterus.

• It is a smooth, hollow tunnel that is divided into four parts: the interstitial, which is 1 cm
in length; the isthmus, which is2 cm in length; the ampulla, which is 5 cm in length; and
the infundibular, which is 2 cm long and shaped like a funnel.
• The funnel has small hairs called the fimbria that propel the ovum into the fallopian tube.
• The fallopian tube is lined with mucous membrane, and underneath is the connective tissue
and the muscle layer.
• The muscle layer is responsible for the peristaltic movements that propel the ovum forward.
• The distal ends of the fallopian tubes are open, making a pathway for conception to occur.

3. UTERUS

The uterus is described as a hollow, muscular, pear-shaped organ.

• It is located at the lower pelvis, which is posterior to the bladder and anterior to the rectum.
• The uterus has an estimated length of 5 to 7 cm and width of 5 cm. it is 2.5 cm deep in its
widest part.
• For non-pregnant women, it is approximately 60g in weight.
• Its function is to receive the ovum from the fallopian tube and provide a place for
implantation and nourishment.
 • It also gives protection for the growing fetus.
• It is divided into three: the body, the isthmus, and the cervix. f
• The body forms the bulk of the uterus, being the uppermost part. This is also the part that
expands to accommodate the growing fetus.
• The isthmus is just a short connection between the body and the cervix. This is the portion
that is cut during a cesarean section.
• The cervix lies halfway above the vagina, and the other half extends into the vagina. It has
an internal and external cervical os, which is the opening into the cervical canal.

EXTERNAL STRUCTURES

1. MONS VENERIS

The mons veneris is a pad of fat tissues over the symphysis pubis.

• It has a covering of coarse, curly hairs, the pubic hair.

• It protects the pubic bone from trauma.

2. LABIA MINORA

The labia minora is a spread of two connective tissue folds that are pinkish in color.

• The internal surface is composed of mucous membrane and the external surface is skin.
• It contains sebaceous glands all over the area.

3. LABIA MAJORA

Lateral to the labia minora are two folds of fat tissue covered by loose connective tissue and
epithelium, the labia majora.

• Its function is to protect the external genitalia and the distal urethra and vagina from trauma.
• It is covered in pubic hair that serves as additional protection against harmful bacteria that
may enter the structure.

4. VESTIBULE

It is a smooth, flattened surface inside the labia wherein the openings to the urethra and the vagina
arise.
 5. CLITORIS

The clitoris is a small, circular organ of erectile tissue at the front of the labia minora.

• The prepuce, a fold of skin, serves as its covering.

• This is the center for sexual arousal and pleasure for females because it is highly sensitive
to touch and temperature.

6. SKENE’S GLANDS

Also called as paraurethral glands, they are found lateral to the urethral meatus and have ducts that
open into the urethra.

• The secretions from this gland lubricate the external genitalia during coitus.

7. BARTHOLIN’S GLAND

Also called bulbovaginal gland, this is another gland responsible for the lubrication of the external
genitalia during coitus.

• It has ducts that open into the distal vagina.

• Both of these glands secretions are alkaline to help the sperm survive in the vagina.

8. FOURCHETTE

This is a ridge of tissue which is formed by the posterior joining of the labia minora and majora.

• During episiotomy, this is the tissue that is cut to enlarge the vaginal opening.

9. PERINEAL BODY

This is a muscular area that stretches easily during childbirth.

• Most pregnancy exercises such as Kegel’s and squatting are done to strengthen the perineal
body to allow easier expansion during childbirth and avoid tearing the tissue.
 10. HYMEN

This covers the opening of the vagina.

• It is tough, elastic, semicircle tissue torn during the first sexual intercourse.

MALE REPRODUCTIVE SYSTEM

In cooperation with the women, men were also given the task of supplying generations upon
generations of brethren for mankind’s race. They are also equipped with miracle-inducing parts
that enable them to propagate with the woman and bring forth life into the world.

INTERNAL STRUCTURES

1. Epididymis

• This is a tightly coiled tube that is responsible for conducting the sperm from the tubule to
the vas deferens.
• It has a length of approximately 20 feet long.
• Some sperm are stored in the epididymis, along with the semen.
• The sperm takes an estimated 12 to 20 days of travel along the epididymis, and a total of
64 days to reach maturity.
2. Vas Deferens

• The function of the vas deferens is to carry the sperm through the inguinal canal from the
epididymis into the abdominal cavity where it will end at the seminal vesicles and the
ejaculatory duct.
• It is a hollow tube that is protected by a thick fibrous coating and surrounded by arteries
and veins.

3. Seminal Vesicles

• These are two convoluted pouches along the lower portion of the posterior surface of
the bladder.
• The seminal vesicles secrete a liquid that is viscous and alkaline and has high protein,
sugar, and prostaglandin content, which makes the sperm increasingly motile.

4. Ejaculatory Ducts

• These ducts pass through the prostate gland to join the seminal vesicles and the urethra.

5. Prostate Gland

• This is a chestnut-sized gland that is situated below the bladder.

• It secretes a thin, alkaline fluid that adds protection to the sperm from being immobilized
by the low pH level of the urethra.
• The urethra passes through its center like a doughnut.

6. Bulbourethral Glands

• Also called as Cowper’s gland, these glands also secrete alkaline fluid to counteract the
acidic environment in the urethra.
• These are twp glands located at either side of the prostate gland and seminal vesicles and
empty through the short ducts towards the urethra.
• Semen is a product of 60% from the prostate gland, 30% from the seminal vesicles, 5%
from the epididymis, and 5% from the bulbourethral glands.

7. Urethra

• This structure passes through the prostate gland towards the shaft and glans penis.
• It is a hollow tube from the base of the bladder and lined with mucous membrane.
• It has a length of approximately 8 inches or 18 to 20 cm.
EXTERNAL STRUCTURES

1. Scrotum

• The scrotum is responsible for the support of the testes and it regulates the temperature of
the sperm.
• It is a rugated, muscular, skin-covered pouch over the perineum.
• To promote the production and viability of the sperm, the scrotum contracts towards the
body during a very cold weather and relaxes away from the body during a hot weather.

2. Testes

• In each scrotum lies two oval-shaped glands called the testes.

• These are 2 to 3 cm in width and are encapsulated in a protective, white fibrous capsule.
• Several lobules are contained in each testis, which also contains Leydig’s cells that
produce testosterone and seminiferous tubules that produce spermatozoa.
• In most men, one testis is slightly lower than the other to prevent trauma and easily sit or
do any muscular activity.

3. Penis

• The penis has three parts: two are called the corpus cavernosa, and the other is the corpus
spongiosum.
• These erectile tissues also contain the urethra, making the penis an outlet for both urinary
and reproductive functions.
• Erection of the penis is stimulated by the parasympathetic nerve innervations, and
the blood supply for the penis is from the penile artery.
• The glans, a sensitive, bulging ridge of tissue, is located at the distal part of the penis.
• The prepuce, which is a retractable casing of skin, protects the glans at birth. It is also the
part that is surgically removed during circumcision.

Human reproductive system, organ system by which humans reproduce and bear live offspring.
Provided all organs are present, normally constructed, and functioning properly, the essential
features of human reproduction are:

1. liberation of an ovum, or egg, at a specific time in the reproductive cycle,

2. internal fertilization of the ovum by spermatozoa, or sperm cells,
3. transport of the fertilized ovum to the uterus, or womb,
4. implantation of the blastocyst, the early embryo developed from the fertilized ovum, in the
wall of the uterus,
5. formation of a placenta and maintenance of the unborn child during the entire period of
gestation,
6. birth of the child and expulsion of the placenta, and
7. suckling and care of the child, with an eventual return of the maternal organs to virtually
their original state.
For this biological process to be carried out, certain organs and structures are required in both the
male and the female. The source of the ova (the female germ cells) is the female ovary; that of
spermatozoa (the male germ cells) is the testis. In females, the two ovaries are situated in the pelvic
cavity; in males, the two testes are enveloped in a sac of skin, the scrotum, lying below and outside
the abdomen. Besides producing the germ cells, or gametes, the ovaries and testes are the source
of hormones that cause full development of secondary sexual characteristics and also the proper
functioning of the reproductive tracts. These tracts comprise the fallopian tubes, the uterus, the
vagina, and associated structures in females and the penis, the sperm channels (epididymis, ductus
deferens, and ejaculatory ducts), and other related structures and glands in males. The function of
the fallopian tube is to convey an ovum, which is fertilized in the tube, to the uterus, where
gestation (development before birth) takes place. The function of the male ducts is to convey
spermatozoa from the testis, to store them, and, when ejaculation occurs, to eject them with
secretions from the male glands through the penis.

At copulation, or sexual intercourse, the erect penis is inserted into the vagina, and spermatozoa
contained in the seminal fluid (semen) are ejaculated into the female genital tract. Spermatozoa
then pass from the vagina through the uterus to the fallopian tube to fertilize the ovum in the outer
part of the tube. Females exhibit a periodicity in the activity of their ovaries and uterus, which
starts at puberty and ends at the menopause. The periodicity is manifested by menstruation at
intervals of about 28 days; important changes occur in the ovaries and uterus during each
reproductive, or menstrual, cycle. Periodicity, and subsequently menstruation, is suppressed
during pregnancy and lactation.