Mice are small mammals. The average body length of the animal is 10 cm. The largest animal grew up to 15 cm. The size of the crumb mouse reaches 7 cm.
The mouse muzzle has an elongated and slightly pointed shape. The ears of the mammal are large and rounded. Eyes are black. The tail is thin, reaches the length of the body. It is almost not covered with wool and has ring scales.
The animals adapt perfectly to various living conditions, so mice are distributed around the world.
The mouse coat is smooth and pleasant to the touch. The color of the individuals living with us varies from gray to black and depends on the type of mouse. In the photo you can find rodents of sand or brown color. These animals live in deserts.
The fur coat helps the pest to hide from enemies, so its color is so different.
The front legs of the mice are shorter than the hind legs and have four fingers. The hind limbs have five fingers. Mice have tenacious claws at the ends of their fingers.
The sensory organs of domestic mice are not as developed as those of their wild relatives. Their vision is not sharp.
The structure of the senses has the following features:
- Spherical eyes. They do not respond to blue and green. The mice see yellow and red.
- Ears pick up high-pitched sounds.
- Oriented to smells. The nose helps to distinguish “your” from the enemy, find food, determine your location.
- At night, a mustache helps them navigate.
If the mouse is frightened, then its urine acquires a special smell, reporting the danger to the members of the pack. In this case, the animals begin to run away and seek shelter.
Female urine reacts to the urine of the females. Urine of males affects all members of the family.
The limbs have special glands that secrete secretions. He is needed to mark his territory.
The skeleton of the mouse is flexible, but the skeletal system is strong.
The mouse skull is elongated, has eye sockets. In adults, five ridges are distinguished (places in which bones connect):
- parietal temporal,
The roof of the cerebral cranium is formed by unpaired inter-dark and paired parietal bones. The vertebrae are attached to the paired occipital bone.
The mouse spine is divided into five sections:
The cervical vertebrae in the mouse are seven. They form a short column. The thoracic section consists of thirteen vertebrae. The lumbar region includes two real and two false vertebrae that form the sacrum. The tail section is formed of twenty vertebrae. The halves of the pelvis are divided. Rodents have no pubic fusion.
The pubic bones of young females are connected by ligaments. As soon as she gives birth, the bones diverge. This feature helps pests to safely produce large numbers of large cubs.
The chest of the mouse is narrow. Some individuals do not have a key, which allows them to squeeze into the narrowest holes. The bones in mice are mobile and light.
The structure of teeth in a mouse has one interesting feature - its incisors have no roots, and therefore are constantly growing. The pest has to constantly nibble something, otherwise its incisors will grow and take an ugly shape.
Each jaw is equipped with two pairs of incisors, capable of growing one millimeter per day. Their front part is covered with durable enamel, which is not on the back. Because of this, the teeth of mice are erased unevenly. This feature makes the incisors sharp.
Mice cannot gnaw through metal. If the animal tries to do so, it will break the lower incisors. This will bite the bite - the upper incisors will be bent. The animal will not be able to eat and will die of hunger.
There are no fangs, but there are molars with which the rodent grinds food. The surface of some of them has tubercles. Between the molars and incisors is a diastema - a toothless area.
The molars are also constantly growing, therefore, small branches of trees or special additives that can be ground can be present in the mouse diet.
Pests behave actively all year round. But the body temperature of the mouse does not adapt well to sudden changes in the environment. Therefore, in winter, the animal prefers to settle near a person. So it provides itself with warm shelter. In cold weather, they need as much food as is required to maintain heat.
In nature, rodents prepare for the winter period and make provisions. Home mouse products do not store, because they always have a power source. They devote more time to breeding and raising offspring. Wild animals, such as field and forest mice, do not breed as actively in nature as domestic animals do.
Although the size of the mouse is small, it has the courage. The animal is able to attack a large animal if it cuts off its escape routes.
Pests are more active at night. But in the cold season, they are active even before sunset. Decorative animals adapt to the rhythm of human life - they become mobile during the day, and at night they try to relax.
Mice prefer to live in a group. So it’s easier to find food and defend the territory. Conflicts in the family are regulated by the leader of the pack.
To understand it, let's start with the origins. As early as the beginning of the 19th century, Eduard Weber formulated the principle: “The strength of muscles, all other things being equal, is proportional to its cross section”. What does this mean? It is necessary to find the “thickest” place in the muscle and cut it across at that place. If we do this for spindle-shaped muscles, then the cross section of the muscles, which is drawn across the muscle length (the straight line connecting the beginning and end of the muscle), is drawn across the muscle fibers.
It was found that the cirrus muscles showed greater strength than the spindle-shaped muscles, although the cross-sectional area of these muscles was approximately the same. In this regard, it was suggested that differences in muscle strength are associated with a denser “packing” of muscle fibers in the cirrus muscles. Because with the same volume, cirrus muscles contained more muscle fibers. The question arose: “How to compare skeletal muscles with different architectures?” For this, it was decided that the cirrus muscles should be evaluated not physiologically, but physiologically.
If a muscle is cut in a plane perpendicular muscle fibers and measure the area of the resulting figures, then the sum of the areas will characterize the value physiological muscle diameter (fig. 1 right).
From these definitions it follows that in a muscle having a parallel course of muscle fibers (for example, spindle-shaped), the anatomical and physiological diameters are equal. But the cirrus muscles physiological diameter is more anatomical. So, for example, in men who are not involved in physical education and sports, the anatomical and physiological diameter of the biceps of the shoulder (spindle-shaped muscle) is 15 cm 2, and for the broad lateral muscle (cirrus) the anatomical diameter is 24.5 cm 2, and the physiological - 30, 6 cm 2.
Assessment of the anatomical and physiological diameters
The value of the anatomical diameter of the muscle (i.e., its cross-sectional area) is estimated using computed tomography (CT) or magnetic resonance imaging (MRI), Fig. 2.
Fig. 2. Computed tomogram of the muscles of the upper limb. BB - the cross-sectional area of the biceps of the shoulder (anatomical diameter)
The structure and functions of muscles are described in more detail in my books “Hypertrophy of human skeletal muscles” and “Biomechanics of muscles”
To determine the physiological diameter, you need to know the volume of the muscle. Muscle volume is determined on the basis of CT or MRI, however, not one section is made as in the case of the anatomical diameter, but several, sometimes 8-10. That is, the muscle volume is much more difficult to determine than the cross-sectional area of the muscle. Then, according to the formula below, determine the physiological diameter of the muscle:
Physiological diameter = muscle volume x cos α / fiber length.
In conclusion, I can add that when assessing muscle hypertrophy, they most often resort to determining the anatomical diameter. The physiological diameter is evaluated extremely rarely.