Transcript The Urinary System This system includes the organs that

The Urinary System
This system includes the organs
that produce and excrete the
waste substance urine. These
organs are:
*kidneys
*ureters
*bladder
*urethra
The Kidneys (nephro or reno)
These are bean shaped organs located
on both sides of the vertebral column.
Kidneys are retroperitoneal: situated
outside the peritoneal cavity.
Renal fasciae surrounds the kidneys,
holding them in place. Each kidney has
a concave depression (hilus) on it’s
medial margin. This provides entrance
for blood vessels, nerves and the ureter
The kidneys are dark reddish
brown (except feline which are
yellowish red). A cross section
shows the external cortex and
the internal medulla
The renal sinus contains the
renal pelvis, blood vessels and
fat. The renal pelvis is a funnel
shaped reservoir that occupies
most of the sinus. Passing out of
the sinus is the ureter, the outlet
tube that extends to the bladder
Medullary pyramids make up
the medulla, stud the walls of
the renal sinus. Urine collects
through ducts
The nephron is the functional unit
of the kidney, consisting of the
renal corpuscle and the renal
tubule. There are about 1 million
nephrons I the kidney
The renal corpuscle consists of a
double walled cup shaped
structure called the glomerular or
Bowman’s capsule, which
contains a twisted cluster of
capillary channels called the
glomerulus
Kidney functions as a filter for
waste products from the blood and
excretes them in the urine. These
waste products include:
*nitrogenous waste from the
breakdown of proteins, toxic
substances, mineral salts, excess
glucose and water.
Video the urinary system
Video the anatomy of the kidney
The speed that the blood filters
through the kidneys is affected
by the blood pressure. If
systemic blood pressure drops,
as in shock, it may cause blood
filtration to slow to a point to
where the kidneys stop
functioning. If the blood
pressure is too high, kidney
damage may result
The kidneys affect the rate of
secretion of some hormones,
synthesize other hormones and
maintain the pH of the blood so
it remains neutral.
The Ureters
These are muscular tubes
extending from the renal pelvis
of the kidneys. The walls of the
ureters are made up of an outer
fibrous tissue layer, two central
layers of smooth muscle and a
mucous membrane lining.
The ureters enter the neck of the
bladder at the trigone. The
ureters enter the bladder
obliquely, the flow of urine back
to the kidney is effectively
controlled by a natural valve
Urine enters the bladder on average of
every 10 to 30 seconds in spurts, rather
than a continuous flow. These spurts
are produced by peristaltic waves. At
the bladder entrance there is is a ureteral
opening that opens every 2 – 3 seconds,
then it closes until another peristaltic
wave open it again. This prevents urine
from flowing back into the ureters
during bladder contraction
The Urinary Bladder
This is an elastic sac lying in the
pelvis.. It is formed of three
layers of smooth muscle lines
with mucous membrane. The
size and position depends on
how much urine it contains. It
has two openings to receive
urine from the ureters and
another opening into the urethra
The neck of the bladder, uniting
with the urethra contains a
sphincter muscle that controls the
amount of urine into the urethra.
The bladder has two main
functions:
*to store urine
*to excrete urine
The voiding of urine from the
bladder is called micturition.
The act of preventing or
concluding urination is a learned
and voluntary action in more
intelligent forms of animal life
The urethra is a membranous
tubular canal that carries urine
from the bladder to the exterior
of the body. In the female the
urethra length varies by species.
The exterior opening of the
urethra is called the urinary
meatus
In the female the urinary meatus
is located between the vagina
and the clitoris directly cranial
to the vulva. The only function
of the urethra is urination.
The male urethra varies in length
by species and penile structure.
It is narrower than the female and
this makes the male more prone
to blockages from urolithiasis.
(stone formation) It extends from
the neck of the bladder through
the accessory sex glands,
between the fascia and through
the penis.
The male urethra is divided in to
three sections.
*prostatic
*membranous
*cavernous.
The exterior opening is also clled
the urinary meatus and serves a
dual function, carrying both
urine and reproductive secretions
Normal Urine:
Urine in most species is clear,
pale amber with a characteristic
odor. Urine is approx 95% water
containing dissolved substances
such as nitrogenous waste,
electrolytes, toxins, pigments,
hormones, and abnormal
substances like glucose, albumin
or blood
The average urine output in a 24
hour period varies by:
*species
*temperature
*water intake
*type of work animal is
performing
Male Reproductive Organs:
The basic male reproductive organs
(gonads) are the testes. The ducts are
the epididymides, vas deferentia,
ejaculatory ducts and urethra.
The accessory sex glands (not present in
all species) include the seminal vesicles,
prostate, bulbourethral and coagulating
glands. The penis, scotum and
spermatic cord are the primary structures
The Testes:
A pair of egg shaped glands
normally located in a sac like
structure called the scotum. The
size shape and location vary
depending on the species. Each
testicle is enclosed in a fibrous,
white capsule called the tunica
albuginea.
The interior of the testicle is
divided into compartments each
containing a mass of coiled
seminiferous tubules and
interstitial cells (cells of Leydig),
which join into a cluster and enter
the head of the epididymis.
The testes have two functions:
*producing spermatozoa
*secreting hormones
the sperm cells are produced by
the seminiferous tubules. The
primary hormone, testosterone, is
secreted by the cells of Leydig.
Testosterone has several
functions:
*induces and maintains male
secondary sex characteristics
such as massive head and
shoulders, crest of withers, tusks
on boars and horns on rams. It
also influences muscle and bone
growth
Male
Female
Male animals generally have less
subcutaneous fat and the meat is
less tender and juicy. Castration
is performed on all animals
intended for meat production to
eliminate accumulation of
testosterone after maturity.
Testosterone also has an influence
on fluid and electrolyte
metabolism as well as as an
excitatory effect on the kidney
tubule and suppresses anterior
pituitary secretions
Epididymus:
a pair of tightly coiled tube like
structures. They act as a place for
sperm to mature, store sperm
before ejaculation and they
secrete a small portion of the
seminal fluid
Vas Deferens:
a pair of muscular tubes with diameters that
vary by species. They are the continuation of
the tail of the epididymis and runs through
the inguinal canal. Each epididymis is
encased in the spermatic cord. Then they
travel to the bladder and connect with the
seminal vesicle and form the ejaculatory duct.
The vas deferens moves sperm from the tail
of the epididymis to the ejaculatory duct
Ejaculatory ducts:
two short tubes formed by the
joining of the vas deferens with
the ducts of the seminal vesicles.
They pass through the prostate
gland and extend to the urethra
Vesicular glands (seminal
vesicles, term used in stallions):
two twisted pouches lying along
the dorsal and caudle surface of
the bladder, ventral to the
rectum. They are lacking in the
dog and cat. They secrete the
mucid, liquid part of the semen
Prostate gland:
smooth muscle and glandular
tissue. It secretes a viscous,
alkaline substance that makes up
most of the seminal fluid. The
alkalinity protects the sperm.
Spermatic cords:
White fibrous tissue encasing the
vas deferens, blood and lymph
vessels and nerves
Scrotum:
saclike structure that houses the
testicles. It is separated
internally by the scrotal septum.
The scrotum regulates the
temperature of the testicles
Penis:
made up of three rounded masses
of erectile tissue encased in a
fibrous capsule. The penis
contains the urethra which
carries both reproductive
secretions and urine
Female reproductive organs:
The ovaries:
located caudle to the kidneys. Each
ovary is connected to the uterus by
a ligament. A single layer of cells
forms the ovarian surface. The
interior consists of a network of
connective tissue where the
follicles are embedded, and these
contain the ova.
The functions of the ovaries are
ovulation and hormonal
secretion (estrogen and
progesterone)
Estrogen induces female
characteristics and uterine
preparation.
Progesterone prepares the uterus
to receive the fertilized ovum
Fallopian tubes (ovaducts):
consist of an inner ciliated
mucous membrane layer, a
middle smooth muscle layer and
outer layer of serous tissue. This
acts as ducts to the uterus for the
ova. Fertilization usually takes
place in the fallopian tubes
Uterus (metro, hystero):
This is thick walled hollow organ. It is
made up of the body (corpus), the
cervix (neck), and two horns (cornus)
The walls are made of three layers
* endometrium (inner)
myometrium (middle)
perimetrium (external)
The perimetrium is continuous with a
band of the peritoneum known as the
broad ligament.
The uterus has several functions:
* prepares for the acceptance of the
fetus
* develops specialized structures
for attachment of placenta
* produces uterine milk to nourish
the embryo before implantation
* maintains and supports
developing fetus
* contracts to move fetus into birth
canal
The Cervix:
Composed of smooth muscle
arranged in a ring like structure
called a sphincter.
It prevents foreign bodies from
entering the uterus during gestation.
It is usually tighly closed exceot
during estrus when it relaxes to
allow sperm to enter. During
pregnancy the cervix is filled with a
mucous plug.
The Vagina:
an elastic tube lined with a mucous
membrane. Before sexual maturity the
external vaginal orifice may be
occluded by a fold of mucous
membrane called the hymen.
The vagina acts as a sheath to accept
the penis during copulation and
provides passage for uterine secretions
and the neonate during pregnancy
The Vulva:
The vulva consists of the vaginal
orifice, vestibular glands,
clitoris, hymen, and the urethral
orifice.
Mammary Glands:
These are milk producing glands
composed of connective and adipose
tissue. The milk secreting cells
(alveoli), these form larger ducts called
the udder cistern. This transports milk
to the base of the teat.
Milk production is stimulated by the
lactogenic hormone prolactin. The
emptying of milk secreting tissue is
caused by the hormone oxytocin.
The estrous cycle:
The purpose of the estrous cycle is to
prepare the uterus to receive a fertilized
ovum.
At the beginning of the cycle, ova within
the follicles in the ovaries begin to
develop. They will continue to develop
until they reach ripened follicle size
(graafian follicle). One or more of the
graafian follicles rupture and the ovary is
expelled
Ovuation usually occurs during
estrus. The ruptured follicle grows
larger and fills with a yellow lipoid
material and becomes the corpus
luteum. The corpus luteum secretes
progesterone. If fertilization occurs,
the corpus luteum continues to
secrete progesterone and prevent
future estrous cycles during
pregnancy.
If fertilization does not take
place the corpus luteum and its
secretions deminish forming a
corpus albicans.
The Stages of Estrus:
The estrus cycle is divided into four
phases
*proestrus
*estrus
*metestrus
*diestrus and in some species
*anestrus
Proestrus
this is the building up phase. During
this phase, follicle stimulating
hormone (FSH) is secreted by the
pituitary gland and causes the
follicle to develop within the ovary.
FSH stimulates the ovary to release
increased amounts of estrogen
which causes changes to the vagina,
uterus, oviducts and ovaries.
Estrus
This is the period of sexual
receptivity. Ovulation occurs
during this phase and in some
cases right after this phase. FSH
levels decrease and luteinizing
hormone (LH) increases causing
the ripened follicle to rupture
Metestrus
this is the postovulatory phase.
During this phase the corpus luteum
forms and produces progesterone.
Amounts of estrus decrease.
Progesterone is responsible for proper
implantation and maintaining pregnancy.
If pregnancy does not occur the corpus
luteum decreases in size to a corpus
albicans. The cycle continues metestrus
will be followed by pregnancy, false
pregnancy, diestrus, anestrus.
Diestrus and Anestrus
Diestrus is a short inactive phase
before the onset of the next
proestrus in polyestrus animals
Anestrus is a period of sexual
inactivity. Canines are in estrus
twice a year and have long
periods of anestrus between
cycles
Pregnancy:
This is the period between conception
and parturition. After fertilization, the
ova moves from the uterine tube to the
uterus. Until implantation the organism
is called an embryo. After implantation
the organism is called a fetus. The
placenta is the only connection between
the dam and the fetus.
Gestation periods vary:
bovine: 280 days
equine: 336 days
caprine, ovine: 150 days
porcine: 114 days
canine and feline: 63 days