The Dog's External Aspect
The external aspect of the dog varies in function of the breed or type that
each individual belongs to, but it is convenient to become familiar with the
main, common points of reference among all of them; which in some cases might
have a specific terminology proper of the cinofilia.
Basic Types of Tissue
There are four basic types of tissue depending on their structure and the
precise function that they serve in the body:
Epithelial: Its main mission is to protect the organism,
it is a simple tissue formed by several layers of cells united to one another;
it doesn't only cover the outer parts of the body, but also the heart, blood
vessels and digestive, respiratory, urinary and genital tracts.
Muscular: Consists of cells that are capable of reducing
their size and are closely related with the capacity of maintaining the body's
posture and movement, also their capacity of transporting substances such ass
food, blood or sperm through out the body. There are three types of these:
- Voluntary muscular tissue
Nervous: Is based in cells which are capable of
transmitting information that allows the animal to know what is going on around
it and also allows the animal's organism to control what goes on inside it.
Conjunctive: This is the most abundant tissue, which has
a fundamental role in the animal's organism since it extends around all the
other tissues connecting them, putting them into place and sustaining
them. There are several types of conjunctive tissues, depending on their own
characteristics: blood (fluid), bones (solid), cartilage (flexible), tendons and
ligaments (dense) and fibers (detached).
Muscle Diagram of a Dog
Dog Skeletal System
As in all vertebrate animals this system is the
combination between the bones which are activated and controlled by the muscles
and support their whole anatomy through the central nervous system.
There are four different types of bones, the
long ones, flat, irregular and short ones; then we have the articulations, which
allow the bones to move in relations to others and can be of three types: fixed,
mobile and semi-mobile.
The cranium deserves special consideration which
holds the brain, eyes, hearing system and the initial parts of the digestive and
respiratory systems, including the maxillaries and the teeth. The bones of the
cranium are divided into two large groups, the neuro-cranium and the espacno-cranium.
There are three types of muscles, the fluted
ones, which can be long or short, the cardiac muscles, that are distinguished
because they are directly controlled by the central nervous system and the soft
Types of Fractures
Bone fractures can be different, but the most common
are the following:
Fissure: when the
bone cracks, it doesn't break apart; unless it is one of those cases where they
come with a collateral hemorrhage. They are the fractures that heal the fastest.
the bone partially cracks; also when even though there is a fracture the tissue
which wraps the bone does not rip. In dogs these are very common, except when
they receive a hard blow.
Simple: when there
is a clean breakage of the bone, and it cracks into two pieces which are
separated, these can be distinguished depending on the direction that the
there is total fracture and the bone breaks into different fragments; these
usually require a surgical intervention and the application of nails in order to
fix the stability of the affected bone. These usually produce debris and some
small parts of the bone are totally separated. These eventually die because of
the lack of blood irrigation.
the broken bone sticks out through the skin; in these cases a serious risk of
infection is produced in the parts of the bone that are exposed to the air.
some a fragment of the broken bone literally is incrusted into another one, most
of the time forming an angle
Dog Digestive System
The Dog Digestive System is composed of all the necessary organs
so that a complete digestion can take done, beginning in the moment when the
food is ingested and chewed until the moment that they are processed and turned
into energy, which are later expelled as residue. Beginning at the mouth and
ending at the anus.
food must reach the stomach as a skittle, with the help of chewing, the tongue
and saliva; it is then passed through the esophagus to the stomach, where the
food is digested, and the fluid mass will then pass to the small intestine.
Finally the wastes pass to the large intestine where they are turned into feces,
which then pass through the rectum to the anal opening.
Anatomy Dog Respiratory
The Anatomy of a Dog Respiratory System is composed of the nose,
larynx, pharynx, trachea, bronchi, and lungs. It has two main functions, to
regulate the body's temperature and to provide the body with oxygen and release
the carbon dioxide.
The act of breathing is automatic and is performed under the
control of the respiratory center, which is located in the medulla
oblongata. Breathing happens in two ways, inspiration and expiration, in the
case of dogs, in normal
conditions, it happens with a rhythm of 15 to 30 per minute.
It is convenient to have in mind that the respiratory rhythm can
be altered by different circumstances and by internal or external factors, like
for example the increase of decrease of the dog's body temperature, after doing
exercise, running, jumping, etc., due to emotional alterations like fear, anger
or sexual excitement or due to the change in the temperature of the
Phases of Respiration in Dog
Inspiration: it is due to a muscular effort that dilates the chest in its
three dimensions, so that the lungs have to expand to fill up the empty space,
which would otherwise be produced; the difference of pressure produced causes
the penetrating flow of air.
Expiration: it is the elastic regression through which the diaphragm moves
forward and the ribs return to their initial position due to the muscular
tension and the elasticity of the cartilage; this lasts a bit longer than the
The Dog Heart and
The dog cardio system is composed of the dog heart, veins,
arteries, conducts and lymphatic glands.
The dog heart, which we can compare to a pump that pushes
blood through out the whole body, has a round aspect and is divided into two
and four cavities which are vertically connected.
The blood that is low in oxygen and has a high content of
carbon dioxide leaves the right ventricle toward the pulmonary artery, where
the exchange of gases is made, so that the carbon dioxide is substituted by
the oxygen. The blood goes back to the heart through the pulmonary vein toward
the left auricle and is the pumped into the left ventricle through the aorta,
to all the body parts. After that the blood goes back to the heart through the
There is a second circulatory system, the lymphatic, which is
responsible for fighting the infections and of returning any fluid to the
heart that has been lost through the blood vessels. The spleen is also part of
the lymphatic system and acts as a reservoir of red blood cells, while the
lymphatic nodules are distributed through out the whole body and are composed
of white blood cells. The thymus is another gland that is part of this system.
Dog Genitals &
Urogenital System of Dogs
It has two parts which are independent and
perfectly defined. On one hand we have the organs that compose the urinary
system, which have the mission of eliminating the body's wastes. It consists
of two kidneys and the urinary tract. The dog genitals and its system
is composed of the gonads, which have the mission of producing cells that
intervene in reproduction together with the reproductive tract and the organs
that intervene in the copulation.
Description of the Urinary Apparatus
Kidneys: their main function is to purify the blood
through filtering; they usually way from 40 to 60 grams, depending on the size
of the individual. It retains toxic substances which are diluted into urine.
Bladder: it is the
only organ in the shape of a bag that holds urine until it is finally
Urethra: it leaves
the bladder and gets rid of the urine. It is longer in males than in females.
Description of the Male's Genital Apparatus
It is formed by two oval testicles, which are held
inside a bag called the scrotum which keeps them below the normal body
temperature; the testicles are in charge of producing the sperm and the
testosterone, the male hormone.
Each of them has an epididymis and vas
male's genital apparatus consists of this gland called the prostate, which it
shares with the urinary system, the urethra and the penis. In the base of the
penis, which is made of erectile tissue; during sexual intercourse the top of it
gets swollen; this is known as the knot.
We must say that in the dog's penis there is a
small bone formation, known as the pineal bone.
Description of the Female's Reproductive
It is formed by two ovaries which are located behind
each kidney and wrapped in a protective bag, which are connected with the uterus
through fine tubes, known as the fallopian tubes. The primary mission of the
ovaries is the production of ovules and the female hormones responsible for
ovulation and gestation.
The uterus in females has the shape of a Y. The
uterine horns leave each fallopian tube and ovary, this is where the embryos are
kept during the first part of gestation; they are very fine. Both of these end
up in the uterus, which is wider and shorter and is separated from the vagina by
a muscle known as the cervix. The vagina is long in proportion to the animal, it
connects with the exterior through what is called the vestibule, in which the
orifice of the urethra coincides. Finally at the end you will find the vulva,
which is the visible part of the female's genital apparatus.
The females also have five or more pairs of
mammary glands in two parallel lines and they each end up in a nipple.
The Dog Nervous System
The dog nervous system could be compared with a control central
in a certain way, it is in charge of knowing the animal's state and physical
condition, and of identifying the environment that surrounds it. It emits the
necessary signals for the circumstantial adaptation on one side, coordinating at
the same time each of the organs and body systems for them to act according to
their own needs at all times.
It is divided into several subsystems
are known as the Central Nervous System, also knows as the neuroaxial system,
the peripheral nervous system and the autonomous nervous system, which consists
of the sympathetic and parasympathetic.
Description and Function of the Nervous System
The CNS (central nervous system) consists of the brain, the cerebellum and
the raquideous bulb, the pituitary gland and the spinal chord.
It controls most of the functions in the animal's body, such as
respiration, the rhythm and heart activity, the digestive functions,
reproduction and thermo regulating; it also acts over the body's balance, the
position of it and its movement, the muscular contractions and the sensation of
Dog Senses Organs
Smell Sense in Dogs: The dog's smell is the most
developed of all its senses and the one that it uses most frequently to identify
the surroundings, those of its kind, people and other animals. The smell is
associated with the dog's hearing and sight, which play a secondary role, which
is just as important.
It is most probably that dogs use their smelling abilities to
locate and follow their owners, even when a long time has gone by, they can
still locate their old house and environment. It is also useful to follow track
s, chase a prey or locate a female in heat even when she is kilometers away.
Dog Sense of Sight: Even though we have heard that dogs
see in black and white, science has confirmed that they are capable of
distinguishing colors and have a very sophisticated visual capacity; especially
when it comes to night vision.
On the other hand, in some breeds where the nasal passage is
long and narrow and the eyes are placed in a lateral position, the visual range
of the dog is of 180 degrees, which is why they are capable of noticing any
movement that happens around them, even when it happens hundreds of feet
away. This explains why hunting dogs trust their eye sight to carry out their
role, as much as their smell.
Dog Sense of Hearing: The importance of this second sense is that the
dog is capable of hearing something very neatly, even if the sound has been
produced 25 meters away, identifying perfectly where the sound came from, while
humans have a very narrow range of hearing. This sense plays an important role
in orientation, combined with the smell and they can both substitute the third
sense when it is deficient or inexistent.
Dog Sense of Touch": The dog's skin has an erectile
muscle, which is why in different circumstances the dog's hair gets prickly or
sticks up. The animal is extraordinary sensitive to caressing and hitting, it is
known that the touching and thermal sensations are rapidly carried through the
skin to their brain; nevertheless, almost everything that has to do with their
mechanism of transmission is unknown.
Dog's sense of Taste: This is the least studied of all
the dog's senses. The number of taste buds that a dog has is inferior to ours
and they have to use their sense of smell to see if the food they are about to
taste is good or not. Dogs usually like foods with strong sweet or salty
especially those that are prohibited to them.