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
  • - Involuntary
  • - Cardiac

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 muscles.

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.

Incomplete: when 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 fracture takes:

  • transversal
  • longitudinal
  • oblique

Multiple: when 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.

Complicated: when 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.

Incrusted: When 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.

The 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 System

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 environment. 

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 previous phase.

    The Dog Heart and Cardiovascular System

    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 halves 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 vena cava.

    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 eliminated.

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 deference.

The 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 Organ
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 which 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 conscience.

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 flavours, especially those that are prohibited to them.