Анатомия домашних животных миология = Anatomy of domestic animals Myology. Учебно-методическое пособие

PEOPLES' FRIENDSHIP UNIVERSITY OF RUSSIA

Agricultural-Technological of Institute

Department of Veterinary Medicine

S.B. Seleznev, G.A. Vetoshkina, V.M. Byakhova

ANATOMY

OF DOMESTIC ANIMALS:

MYOLOGY

For the students of 1-2 courses of Faculty of Agriculture in the specialty «Veterinary Medicine»

Moscow

Peoples’ Friendship University of Russia

2017

Селезнев, С. Б.

С29 Анатомия домашних животных: миология = Anatomy of domestic animals: Myology : учебно-методическое пособие /

С. Б. Селезнев, Г. А. Ветошкина, В. М. Бяхова. – Москва :

РУДН, 2017. – 28 с.

The guidelines include charts and tables, each is accompanied with instructions and explanations, aimed at consolidating the material on myology.

The purpose of the guidelines is to teach students to understand the comparative anatomy of the skeletal muscles and muscle tissue.

For the students of 1–2 courses of Faculty of Agriculture in the specialty «Veterinary Medicine».

Prepared by the Department of Veterinary Medicine of the Peoples' Friendship University of Russia.

Introduction

Myology is a branch of the anatomy of animals concerning structure of muscle system. The muscle tissue being the basis of this system, provides all locomotor processes of an organism. Due to the muscle system body holds in particular position and moves in space, breathing movements of the thorax and the diaphragm, movements of the eyes, swallowing, mobility of the internal organs, including heart work are provided.

The muscle tissue possesses of special contractile organelles – myofibrils. Myofibrils consist of thin protein filaments (myofilaments), that can be unstirated (smooth) or striated (cross-striated). Thus smooth muscle tissue and striated muscle tissue are distinguished.

Table 1

Muscle tissue

Unstriated muscle tissue consists of spindle-shaped cells (smooth myocytes). These cells comprise muscle layers in walls of blood and lymph vessels, in wall of internal organs (stomach, intestines, urinoexcretory ducts, uterus etc.). The length of cells is from 20 µm (in wall of vessel) to 500 µm (in wall of uterus of springer cow), diameter is from 2 to 20 µm. Unstriated muscle tissue has several functional particularities: it possesses of greater strength (e.g. great amounts of chime is moving through the intestines),poorfatigability,slowcontractionandrhythmicmotion (in wall of intestines, smooth muscle contracts 12 tomes in a minute, in a spleen – 1 time in a minute).

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Striated muscle tissue is characterized by striate myofibrils and has two types.

Striated cardiac muscle tissue consists of elongated cylinder-shaped cells (cardiomyocytes). Their ends connect to each other in chains, forming so called “functional muscle fibers”, thickness is 10-20 µm. functional muscle fibers closely interlock and form muscle coat of the heart (myocardium), its constant and rhythmic contractions set in motion blood.

Striated skeletal muscle tissue doesn’t consists of cells as opposite to cardiac muscle, but of multinucleated muscle cylindershaped formations (myosymplasts). The length of myosymplasts varies from several millimeters to 13-15 cm, diameter is from 10 to 150 µm. The number of nuclei can range up to several tens of thousands. Myosymplasts (called “muscle fibers”) comprise skeletal muscles and are found in several organs (tongue, pharynx, larynx, esophagus etc.). According to function skeletal muscle tissue is lightly irritable and contracts in lesser time than smooth muscle (e.g. in normal conditions skeletal muscle contracts during 0.1sec and smooth muscle – during several seconds). But versus smooth muscle of internal organs skeletal muscle is more fatigue.

Musclesystemisdividedinsomaticandvisceralaccording to structure particularities, type of motion function and innervation.

Somatic muscle system comprises 40% of body weight and consists of myosymplasts. It is voluntary contracted and is innervated by somatic nervous system. Somatic muscles contract rapidly, energetic, but short-term and they are very fatigue. This type of contraction is called tetanic and is typical for somatic musculature. It consists of:

1. Cutaneous muscles, that don’t have connection with skeleton and are attached to the skin. Its

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contraction provides skin movement and grab it into the folds;

2.Skeletal muscle, that is attached to skeleton;

3.Diaphragm is an arched muscle, that separates thorax and abdominal cavities of the body.

4.Muscles of tongue, pharynx, larynx, pinnae, eye, middle ear, esophagus and externalia (external organs of reproduction).

Visceral muscle system comprises 8% of body weight and consists of myocytes. It is involuntary contracted and is innervated by vegetative (autonomic) nervous system. Smooth muscles contract slowly, log-term and don’t need much energy. This type of contraction is called tonic and it is typical for visceral musculature, that forms muscle bundles, layers and coat of internal organs.

PART 1. GENERAL MYOLOGY

1.1General characteristics of cutaneous musculature.

Cutaneous muscles – musculi cutanei – are attached to integument, fasciae and doesn’t have any connection to skeleton. Its contraction provides movement of skin and grabs it in folds. These muscles include:

1.Cutaneous cervical muscle – m. cutaneous colli – is well developed in dogs. It lies longitudinally to neck, closer to its ventral surface, and it continues on facial surface to snout and lower lip muscles.

2.Cutaneous muscle of scapula and humerus (scapulohumeral) – m. cutaneus omobrachialis. It covers scapula area and partly brachium. It is well developed in horses and cattle.

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3.Cutaneous trunk muscle – m. cutanues trunci. It is situated laterally from thoracic and abdominal walls, and caudally gives bundles into genual fold.

4.Infemalesinmammaryglandsareatherearecranial and caudal muscles of mammary glands (mm. supramammilaris cranialis et caudalis), that provide folds of the skin and aid to excrete milk. They are well developed in carnivores.

5.In males in this area there are cranial and caudal prepuce muscles (mm. preputialis cranialis et caudalis), that provide folds of prepuce and function as its sphincter.

1.2General characteristics of skeletal musculature

Skeletal musculature is active part of locomotor apparatus. It consists of skeletal muscles and its accessory units, that consist of fasciae, synovial bursas, mucous sheaths of tendons, trochlea, sesamoid bones.

There are around 500 muscles in animal’s body. Most of them are paired and situate symmetrically on both sides of the animal’s body. Its overall weight is 38-42% of horse body weight, 42-47% of cattle body weight, 30-35% of swine body weight.

Muscles aren’t situated irregularly in body, but regularly according to action of body weight gravity and performing functions. They have an impact on that parts of skeleton, that have movable connection, i.e. muscles acts on joints, syndesmoses.

Main places for muscle connection are bones, bit sometimes they are connected to cartilages, ligaments, fasciae, skin. They cover skeleton in that way, that only in several areas bones lie just under the skin. Connecting to skeleton like a leverage, muscles induce different movements of the body, fix the

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body in definite position and give form to the body by its contractions.

1.2.1General functions of skeletal muscles

1.Main muscle function is dynamic. Contracting muscle shortens on 20-50% of its length and thus changes position of connected bones. The performed work results in movement.

2.The other muscle function is static. It performs in fixing body in definite position, maintaining shape of whole body and its parts. One of presentations of this function is the ability to have a standing sleep (horses).

3.Participation in metabolism of nutrients and energy. Skeletal muscles are “source of heat”, because by their contraction about 70%of energy turns into heat and only 30% of energy provides breathing. Skeletal muscles contain around 70% of organism’s water, that why they are called “water sources”. Moreover, adipose tissue can accumulate between muscle bundles and inside them (especially in pigs during fattening).

4.During contraction, skeletal muscles help heart work by simultaneous pushing venous blood through vessels. Experimentally it was found that skeletal muscles work as a pump, providing blood flow through veins. Thus, skeletal muscles are called “peripheral hearts”.

1.2.2Biochemical structure of muscles

Skeletal muscle consists of organic and inorganic substances. The inorganic substances are water, minerals (calcium, phosphorus, magnesium). The organic substances are presented by proteins, carbohydrates (glycogen), lipids (phospholipids, cholesterol).

Table 2

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Chemical structure of skeletal muscles is effected dramatically by age, in a smaller extent by species, breed and sex variations, mostly due to different water concentrations (water percent decreases by age).

1.2.3 Muscle as an organ

Skeletal muscle (musculus skeleti) is an active organ of locomotion apparatus, which shape and structural particularities are determined by performing function and location of the skeleton. Muscle comprises a contractile part – myogaster, and passive part – tendon, due to later muscle connects to bones.

Table 3

Skeletal muscle

Myogaster (ventor) is composed of striated muscle bindles (myosymplasts), each is covered by thin connective tissue coat – endomysium. Muscle bundles are connected into bundles of 1st, 2nd, 3rd order by loose connective tissue (perimysium). Externally these bundles are covered by dense connective tissue (epimysium), which covers each muscle. Connective-tissue elements of intermuscularlocationcontinueintotendonsonendsofmyogaster.

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Tendon (tendo) consists of dense connective tissue and is glitter light-gold in color, in contrast with brown-red myogaster. Commonly tendon is performed on both sides of muscle and connects to bones. Even tendon is much thinner than myogaster, itsstrengthisgreat,itcanholdsevereloadandalmostinextensible. Studies performed that to tear calcaneal tendon in animal a power of 670-930 kg/m3 should be applied.

Vessels and nerves enter the muscle from its internal side. Arteries divide into capillaries, that form dense network in muscle bundles. Each muscle bundle has at least one blood capillary. Blood comes to each muscle by arteries, and flows away bi veins and lymph vessels.

Innervation of skeletal muscles is provided by somatic and sympathetic nerves, containing motor and sensitive nerve fibers.

Muscle growth in length undergoes in so called “growth zones”,thatare at the site of myogaster continuation in tendon, and contain a lot of nuclei, and muscle growth in width is present due to functional load, that is performed by this muscle.

1.2.4 Muscle classification

Each muscle is an individual organ and has definite shape, size, structure, function, origin and site in body. Due to this all skeletal muscles are divided into following categories.

I.By shape muscles are divided into long, short, wide.

Long muscles correspond long leverages and thus present mostly in limbs. They are spindle-shaped, middle part is called myogaster, end corresponding the beginning of muscle is called head, opposite end is called tail. Tendon of long muscles is tapeshaped. Some muscles begin with several heads (multicapitate) on different bones, that increases its anchorage. Muscles can be two-

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headed (biceps), three-headed (triceps) and four-headed (quadriceps).

Short muscles are presented in those areas of the body, where movement amplitude isn’t large (between vertebrates etc.)

Broad muscles site mostly on the trunk and limb girdles. They have extended tendons, called aponeurosis. Broad muscle provides not only motion functions, but also serve as support and protection (e.g. muscles of abdominal wall protect and hold internal organs).

There is also another form of muscles: square-, triangle-, round-, delta-shaped, trapezoidal, serratus etc.

II. By direction of muscle fibers muscle are divided into muscles with straight parallel fibers, with obliquus fibers, with transverse and circled fibers.

If obliquus fibers connect to tendon at an angle to length of myogaster from one side, then these muscles are called unipennate, if from two sides – bipinnate. Sometimes muscle bundles have complex connections, and they reach tendons from several sides. In this case multipinnae muscle id formed (e.g. deltoid muscle).

III. By histostructure all muscles are divided into 5 types: dynamic, dynamo-static, semistato-dynamic, stato-dynamic and static.

Dynamic type of muscles provides active various work, is characterized by prevalence of striated muscle tissue over connective tissue.

Versus dynamic, static muscles don’t have any muscle fibers. They can’t actively participate in animals’ locomotion, but they carry out great static work during standing and footing to the substrate during movements, fixing joints in appropriate position.

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