Question 1. What underlies the evolutionary changes in the musculoskeletal system?

The basis of evolutionary changes in the musculoskeletal system lies, first of all, in the transition of animals from an aquatic habitat to a land-air habitat. The new environment required greater strength from the musculoskeletal system and the ability to carry out more complex and varied movements. An example is the appearance of compound paired limbs with movable (articular) joints of parts and complex muscles in representatives of the class of amphibians - the first land vertebrates.

Question 2. Which animals have an exoskeleton?

All representatives of the phylum Arthropods have an exoskeleton: insects have a chitinous shell, arachnids and crustaceans have integuments impregnated with lime.

Question 3. Which vertebrates do not have a bony skeleton?

Representatives of the classes of cyclostomes and cartilaginous fish do not have a bony skeleton.

Question 4. What does the similar structure of the skeletons of different vertebrates indicate?

The general plan of the structure of the skeletons of different vertebrates indicates a common origin and evolutionary relationship. And the presence of similar private formations means that animals lead a similar lifestyle in similar environmental conditions. For example, both flying birds and bats have a bony ridge (keel) on the sternum.

Question 5. What conclusion can be drawn after becoming familiar with the general functions of the musculoskeletal system in animal organisms?

Despite significant differences in the structure of musculoskeletal structures in different animals, their skeletons perform similar functions: supporting the body, protecting internal organs, moving the body in space.

37. Musculoskeletal system

4.5 (90.29%) 35 votes

Searched on this page:

• what underlies evolutionary changes in the musculoskeletal system
• what animals have an exoskeleton
• which vertebrates do not have a bony skeleton
• What does the similar structure of the skeletons of different vertebrates indicate?
• what underlies evolutionary changes in the musculoskeletal system

Skeleton of limbs.

Limbs tetrapods developed from the paired fins of lobe-finned fish, the skeleton of which contained elements homologous to the bones of the shoulder and pelvic girdle, as well as the front and hind legs.

Originally there were at least five separate ossifications in the shoulder girdle, but in modern animals there are usually only three: the scapula, the clavicle and the coracoid. In almost all mammals, the coracoid is reduced, attached to the scapula, or absent altogether. In some animals, the scapula remains the only functional element of the shoulder girdle.

The pelvic girdle includes three bones: the ilium, the ischium and the pubis. In birds and mammals they completely merged with each other, in the latter case forming the so-called. innominate bone. In fish, snakes, whales and sirens, the pelvic girdle is not attached to the spine, which therefore lacks the typical sacral vertebrae. In some animals, both the shoulder and pelvic girdles include accessory bones.

The bones of the front free limb in quadrupeds are basically the same as those in the hind limb, but they are called differently. In the forelimb, if you count from the body, first comes the humerus, followed by the radius and ulna, then the carpals, metacarpals and phalanges of the fingers. In the hind limb they correspond to the femur, then the tibia, tibia, tarsus, metatarsal bones and phalanges of the fingers. The initial number of fingers is 5 on each limb. Amphibians have only 4 toes on their front paws. In birds, the forelimbs are transformed into wings; the bones of the wrist, metacarpus and fingers are reduced in number and partially fused to each other, the fifth finger on the legs is lost. The horses only have their middle finger left. Cows and their closest relatives rest on the third and fourth toes, and the rest are lost or reduced. Ungulates walk on their toes and are called phalangeal walkers. Cats and many other animals, when walking, rely on the entire surface of their fingers and belong to the digitimate type. Bears and humans press their entire sole to the ground when moving and are called plantigrade walkers.

Rice. 9 Picture of mammalian foot types

Exoskeleton.

U Vertebrates of all classes are represented in one way or another by the exoskeleton. The head plates of scutes (extinct jawless animals), ancient fish and amphibians, as well as the scales, feathers and hair of higher tetrapods, are skin formations. The shell of turtles is of the same origin - a highly specialized skeletal formation. Their skin bone plates (osteoderms) moved closer to the vertebrae and ribs and merged with them. It is noteworthy that the shoulder and pelvic girdles parallel to this have shifted inside the chest. In the crest on the back of crocodiles and the shell of armadillos there are bone plates of the same origin as the shell of turtles.

The body consists of segments that are combined into body sections.

Jointed mobile limbs.

Phylum Arthropods.

Arthropods are the most numerous type of animals, more than 1.5 million species.

Type Features:

Skeletal muscles are formed by individual muscles that have a striated structure. The body cavity is mixed, filled with hemolymph, which performs the function of blood and cavity fluid. And it circulates in an open circulatory system.

Digestive system: mouth, pharynx, esophagus, stomach, intestines, anus.

Breathing varies depending on lifestyle:

• Gill (modified limbs)
• Pulmonary
• Tracheal

The circulatory system is not closed, the heart is on the dorsal side.

Excretory organs:

• Aquatic forms have a pair of green glands
• In terrestrials - Malpighian vessels
• In insects, there is a fat body that serves as a storage bud.

Nervous system of the nodal type: peripharyngeal nerve ring and ventral nerve cord. The sense organs are well developed. The organs of touch, chemical sense, hearing, and balance are most often located on the limbs. Eyes can be simple or complex.

Reproduction is sexual, most animals are dioecious, and sexual dimorphism is often pronounced. Fertilization is internal, development is direct and indirect.

The phylum arthropods include the following classes:

1. Crustaceans.

2. Arachnids.

3. Insects.

Class Crustaceans .

Crayfish lives in clean fresh waters. Leads a nocturnal lifestyle, mostly bottom-dwelling.

The body consists of a cephalothorax and abdomen. The cephalothorax is covered from the back and sides with a cephalothorax shield. The abdomen consists of movably articulated segments.

1) On the cephalothorax there is:

1. a pair of stalked compound eyes, they have mosaic vision.
2. two pairs of antennae:

• long – organs of touch
• short – olfactory organs

3. 6 pairs of limbs around the mouth:

• 1 pair – upper jaws
• 2 pair – lower jaws
• 3 pair - jaws for delivering food to the mouth.

4. 5 pairs of walking legs, the first pair are claws, which are used to capture food, attack and defend.

2) The abdominal segments bear swimming legs, the last of them is modified and acquires a caudal fin. The legs of females hold the eggs.

Crayfish are omnivores, often feeding on rotting organic matter. The stomach consists of:

• The chewing section contains powerful chitinous teeth that grind food.
• The fishing section forms a lattice through which only highly crushed food is filtered. The midgut forms a pair of hepatic outgrowths. It is involved in the digestion and absorption of nutrients.

Breathing through the gills. Gills are outgrowths of the thoracic limbs. Gas exchange takes place here.

The circulatory system is not closed, the heart is a pentagonal muscular pouch with three pairs of holes located on the dorsal side.

The excretory organs are a pair of green glands located at the base of the antennae.

The suprapharyngeal ganglion is well developed in the nervous system. The sense organs are well developed: eyes, antennae, the organ of balance is located at the base of the short antennae.

Crayfish are dioecious with pronounced sexual dimorphism. The genital organs are located on the cephalothorax under the heart and opening holes at the base of the walking legs.

They walk along the bottom and dry land with their head end first, and swim with their tail end.

Class Arachnida.

Arachnids live mainly on land, their body consists of a cephalothorax and abdomen, covered with a thin cuticle and numerous hairs. Scorpions have a more dismembered body, while mites have a united body. On the cephalothorax are located:

Four pairs of simple eyes

Mouthparts (a pair of claws and a pair of claws)

Four pairs of walking legs

No antennae

The limbs of the abdomen are reduced or modified, breathing with the help of lungs or tracheas.

Spider - cross- a typical representative.

Its body consists of a cephalothorax and abdomen. The mouthparts serve to capture and kill prey; these are jaws (chelicerae) containing poisonous glands and a claw; the claws (pedipalps) are thinner and longer than the chalicerae, and also serve as organs of touch.

The walking legs are covered with sensitive hairs and end with three claws (for weaving webs and moving along them).

The abdomen is large, all its segments are fused together, on the dorsal side there is a peculiar pattern - a cross. There are special organs on the abdomen (transformed limbs):

Lung sacs

Three pairs of arachnoid warts, through which 3 types of web are released from the arachnoid glands:

A) thick, not sticky for the radial threads of the web

B) thin, sticky, for spirally twisted threads

B) intended for weaving cocoons

With the help of webs, spiders build shelters, spread out, and often use them to catch flying insects. The spider, having caught the vibrations of the signal thread, kills the victim with poison, while digestive enzymes are introduced into the victim’s body. After some time, the Spider absorbs semi-digested food using its muscular pharynx. The spider does not have a stomach; food is digested and absorbed in the intestines and liver.

The spider breathes with the help of its lungs and trachea.

The circulatory system is not closed, on the dorsal side there is a tubular heart, from which the aorta emerges into the cephalothorax, through which oxidized hemolymph is pushed into the body cavity.

The excretory organs are a pair of thin Malpighian vessels located in the abdomen.

The suprapharyngeal ganglion fuses with the ventral nerve cord to form the primitive brain; which is located in the cephalothorax. The organs of touch and smell are very well developed, capable of perceiving air vibrations and humidity.

Spiders are dioecious, with clearly expressed sexual dimorphism: the female is much larger than the male. The gonads are located in the abdomen, fertilization is internal. The female lays eggs in a cocoon, development without metamorphosis.

Class Insects

This is the largest class of animals on Earth (more than a million). They have adapted to a wide variety of habitats and are the only invertebrate animals capable of flight. All insects are characterized by: the body has three sections - head, chest and abdomen; on the chest there are three pairs of walking legs.

Chafer- a typical representative of insects. Its body is divided into head, chest and abdomen. On the head there are:

A pair of articulated antennae (containing tactile and olfactory receptors);

A pair of compound compound eyes (see UV rays);

A mouth surrounded by an oral apparatus (modified limbs) of a gnawing type - paired upper and lower jaws, lower lip.

Depending on the nature of the insect's feeding, the oral apparatus has a different structure. The initial oral apparatus is considered to be of the gnawing type. For example, such oral apparatus is found in beetles, cockroaches, grasshoppers, and butterfly caterpillars. Other types of mouthparts can be: piercing-sucking (in bedbugs, aphids, mosquitoes, mosquitoes, sucking (in butterflies); licking (in flies).

The beetle's chest consists of three segments. A pair of articulated walking legs equipped with claws is attached to each segment - three pairs of legs in total.

Depending on the method of movement, the legs have a different structure: jumping (in grasshoppers, locusts, fleas); digging (for mole crickets); swimming (in the swimming beetle).

On the second and third segments of the chest there are wings- two-layer folds of the body wall, with tracheas and nerves entering them.

The shape, structure and degree of development of wings varies in different groups of insects. Both pairs of wings are approximately equally developed in primitive insects, such as dragonflies. In beetles and cockroaches, the first pair of wings turns into hard elytra. In flies, mosquitoes, and horseflies, only the first pair of wings is developed, and the second is transformed into halteres - an organ of stabilization in flight. There are insects that have lost their wings due to a flightless lifestyle, for example fleas and lice.

The beetle's abdomen consists of eight segments, like notches on the gel (hence the name insects), and is motionlessly connected to the chest. It contains most of the internal organs.

The muscular system is highly organized. Striated skeletal muscles, attached to the internal projections of the chitinous skeleton, provide movement. The wing muscles are capable of contracting at speeds of up to 1000 times per second.

The digestive system includes: the mouth (the ducts of several pairs of salivary glands flow into it), in many insects it often expands into a crop), the gizzard (has thick muscular walls and carries chitinous teeth for grinding).

Breathing only tracheal. Tracheas begin with paired openings - spiracles, along the edges of the abdominal segments into which air enters during muscle contraction.

The circulatory system is simplified due to the presence of a developed tracheal system. On the dorsal side of the abdomen lies a tubular heart, divided by valves into chambers, with a pair of lateral openings in each. When the heart contracts, hemolymph is pushed into the aorta towards the head and then into the body cavity, and from the cavity it returns back through the holes: Hemolymph is usually colorless, its main function is the distribution of nutrients.

The excretory organs are malpighian vessels And fat body(storage bud).

In the fat body, excretory products accumulate in the form of crystals that remain in it until the end of life, and nutrients are deposited. The fat body also serves as a source of metabolic water.
Modified areas of the fat body in some insects (fireflies) form luminescent organs.

The nervous system is formed brain(large suprapharyngeal ganglion, from which nerves go to the sensory organs on the head), peripharyngeal nerve ring And ventral nerve cord. The brain, especially in social insects, has a complex structure. In the abdominal nerve chain, the nerve ganglia of the thoracic segments are more developed than others, because they innervate the legs and wings. The behavior of insects can be very complex: along with instinctive behavior, it often has a pronounced conditioned reflex character.

Sense organs are complex and diverse, which is associated with a high level of organization and complex behavior of insects. There are two compound eyes on the head (can distinguish color
and item details). Antennae with expanded plates on
at the end is the organ of smell. Palps on the lower lip and jaws -
organ of taste.

Many insects, in addition to compound eyes) may have several simple
The sense of smell is perfectly developed: the males of some butterflies find
female by smell at a distance of several kilometers. Row, insects
(crickets, grasshoppers, cicadas) have organs, hearing, located most often
on the limbs.

Insects are dioecious; many have pronounced sexual dimorphism. The gonads are paired, located in the.
1brupgke. Fertilization is internal. Development in primitive insects is direct. In highly organized insects with metamorphosis (pre-agcenation).
In this case, a worm-like larva emerges from the egg. Metamorphosis can be incomplete or complete (Table 2. 1).
The development cycle of the cockchafer passes, with complete transformation. The female lays eggs in the soil and then dies.
The larvae that emerge from the eggs live in the soil and feed on humus. The larvae overwinter deep underground, and next spring they rise to the surface and begin to feed on the roots of herbaceous plants. After the second winter in the soil, the larvae
begin to eat the roots of bushes and trees, thereby causing
The most significant harm is the death of young plants.

The larvae have a whitish body with soft coverings. The head is covered with a dense, dark head capsule. There are three pairs of jointed limbs on the thoracic segments. There are spiracles on the sides of the body. The trachea and intestines are visible through the thin covers of the larvae,
full of food.

After the fourth winter, the larva pupates in the soil.
The pupa has a dense chitinous cover, is motionless and does not
rages. In autumn, an adult beetle emerges from the pupa and
overwinters in the soil and rises to the surface only in the spring

The main meaning of insects:
-- the most important link in natural trophic chains

Soil-forming role

Decompose organic residues;

Agricultural pests;

Forestry pests

Laboratory animals

Aesthetic value.

Subtype Skullless

Class Cephalochordates(Lancelets)

Body length is 4-8 cm. The body of the lancelet is translucent, fusiform, laterally compressed, there is no separate head. A fin fold runs along the body, in which the dorsal lanceolate caudal and subcaudal sections are distinguished.

The notochord stretches from the head to the caudal end (internal skeleton), covered with connective tissue, which provides support for the fins. Adjacent to the notochord are muscle segments of striated muscle tissue. The skin is formed by a single layer of epithelium (which secretes a thin cuticle with a thin layer of connective tissue.

Lancelet is a biofilter. It has a pre-oral funnel formed by tentacles (they create a flow of water), a mouth and a pharynx penetrated by gill slits. Divergence, intestines, a blind outgrowth departs from it - the liver, which secretes enzymes, anus. Gas exchange occurs in the interbranchial septa covered with ciliated epithelium. Diffusion of oxygen through the skin is possible.

The circulatory system is closed. One circle of blood circulation, no heart, it was replaced by the abdominal aorta, located under the pharynx. The blood is colorless.

Excretory organs – nephridia, 100 pairs that open.

The nervous system has tubes, with an expanded anterior end, from which nerves extend.

Sense organs are poorly developed. There are light-sensitive eyes (they live in shallow water), organs of touch and chemical sense, tentacles of the preoral funnel scattered in the skin, and an olfactory fossa at the anterior end of the body.

The lancelet is a dioecious animal. The gonads, about 25 pairs, are located on the sides of the body in the region of the gill tentacles and do not have excretory ducts. Gametes are excreted through breaks in the walls of the gonads into the peribranchial cavity and further into the external environment, external fertilization, development with metamorphosis. The larva is covered with cilia.

Lancelet studied by A.O. Kovalevsky.

Subphylum cranial or vertebrate .

Character traits:

• Internal skeleton (cartilaginous or bone, its basis is the vertebral column)
• The brain has five sections
• The skull is cartilaginous or bone, covering the brain.
• Organs of vision - two eyes
• Hearing organs (paired)
• Closed circulatory system, heart on the ventral side of the body
• Excretory organs – kidneys

Pisces class .

Fish live in an aquatic environment and have specialized respiratory organs - gills, which are capable of absorbing dissolved oxygen. The fish class includes two subclasses:

1. Cartilaginous fish

2. Bony fish

Subclass Bony fish

There are about 20 thousand species of fish. Wide range area and numerous intraspecific diversity, progressive group.

Features of the structure:

• Limbs - fins (bone axes covered with membrane)
• Two-chambered heart, one circle of blood circulation - only in fish.
• Brain of 5 sections
• The organ of hearing is the inner ear.

River perch- a representative of bony fishes. The body of the perch is streamlined, divided into a head, body and tail (there are no clear anatomical boundaries). Convergent body shape in all moving organisms. The skin contains many glands that secrete mucus, which reduces friction. Bone scales are different in shape and structure, one edge is immersed in the skin of the other free, laid according to the principle of tiles, which also reduces friction.

Organs of movement - fins:

• Paired (thoracic and abdominal)
• Unpaired (dorsal, anal, caudal)

The skeleton of the perch is bony, divided into sections:

1) Axial skeleton:

1. spine

2. skeleton of the head - skull

2) the skeleton of the limbs - fins.

The spine consists of vertebrae. Between them, the remains of the chord are preserved - cartilaginous layers. Notochord is a cartilaginous elastic cord. The spine is divided into sections:

1. trunk (ribs are attached to the vertebrae)

2. caudal section

Each vertebra consists of a body and an upper arch with a process. The combination of the superior arches forms the spinal canal, which contains the spinal cord.

The skull is divided into two sections:

1. cerebral
2. visceral (gill and jaw arches, gill covers - an advantage of bony fish, protection from damage)

The skeleton of the fins consists of bony rays covered with skin - organs of balance and movement.

The fish's muscles are well developed. The muscles are attached externally. The trunk muscles retain their segmental structure. Separate muscle groups appear - muscles of paired fins and gill covers.

The digestive system consists of:

• mouth with teeth (bone plates protruding from the skull) - to hold food and capture prey.
• Pharynx
• Esophagus
• Stomach
• Small intestine (liver ducts)

The appearance of additional organs related to the nature of nutrition

1. large intestine

2. anus

Digestive glands:

2. pancreas

Associated with the food system is a swim bladder filled with gases. It allows the fish to move vertically in the water column and stay in the water column.

Respiratory organs - gills. Gill filaments permeated with capillaries sit on the gill arches; gas exchange takes place here. Gill rakers are a device that prevents large food particles from entering the gill slits. The respiratory system is permeated with food, the lungs and gills are the anterior outgrowths of the intestine. The respiratory and digestive systems are derived from the endoderm. Water entering the pharynx through the mouth washes the gill slits and comes out from under the gill covers.

The circulatory system has the abdominal aorta, which carries venous blood to the gills. From the gills, arterial blood flows into the dorsal aorta, which passes under the spine, branches and supplies blood with oxygen and nutrients to organs and tissues. Venous blood enters the atrium through large veins.

Heart contractions are weak, slow, metabolism is slow, so fish are cold-blooded.

The excretory organs are the kidneys, which are ribbon-shaped and stretch under the spine along the body. The ureters extend from the kidneys, and the bladder opens to the outside with a separate independent opening.

Respiratory organs - gills. They sit on the gill arches gill filaments, permeated with capillaries (gas exchange takes place here), and gill rakers(a filtering apparatus that prevents large food particles from entering the gill slits). Water entering the pharynx through the mouth washes the gill filaments, passes through the gill slits and comes out from under the gill covers.

The circulatory system has one circle of blood circulation and a two-chamber heart (atrium and ventricle). The abdominal aorta departs from the ventricle: it carries venous blood (saturated with carbon dioxide) to the gills. From the gills, arterial blood (saturated with oxygen) enters the dorsal aorta (passes under the spine, branches and supplies blood and oxygen to organs and tissues). Venous blood enters the atrium through large veins.

Heart contractions are slow, weak; metabolism is slow. Fish - cold-blooded animals.

Excretory organs - kidneys(have a ribbon-like shape and stretch under the spine along the body), ureters, bladder(open to the outside with an independent urethral opening).

The nervous system consists of central department (brain and spinal cord) And peripheral department.

The brain consists of five sections:

Forebrain (well-developed olfactory lobes);

Diencephalon (optic nerves arise from it);

Midbrain (visual centers developed); cerebellum (responsible for coordination of movements);

Medulla oblongata (it contains centers for regulating respiratory, circulatory And digestive systems; centers of some sense organs (hearing, lateral line). ■ Well developed sense organs:

Olfactory organ - paired olfactory sacs (open on the surface of the head with nostrils and are lined with olfactory epithelium)

The organ of vision is the eye (spherical lens and flat cornea); organ of hearing - the inner ear;

Taste organ - taste buds in the oral cavity and on the surface of the skin;

Organs of touch - skin, antennae;

Lateral line organ - perceives water vibrations.

Lateral line - groups of sensory cells immersed in channels passing under the skin and opening onto the surface of the body with openings.

Participate in reproduction male And female. Males have paired testes and vas deferens, and females have paired ovaries and oviducts. External fertilization during spawning A larva emerges from the egg (feeds from the yolk sac), which turns into a fry when it switches to independent feeding. In some groups of fish, fertilization is internal, and the embryo develops using the nutrients of the eggs in the female genital tract (ovoviviparity). There are fish that spawn a huge amount of eggs (perch - up to 300 thousand, cod - up to 10 million eggs), most of which die in the early stages of development. Others (three-spined stickleback, etc.) spawn a small number of eggs, but take care of them, and the offspring have a better chance of survival. There is even less caviar in fish that are characterized by ovoviviparity (swordtails, guppies, etc.).

Subclass Cartilaginous fish

Subclass lobe-finned (meat-legged)

They are extremely primitive in many ways. They do not develop vertebral bodies, have a notochord, a conus arteriosus in the heart, and a spiral valve in the intestine. In the blood, like cartilaginous fish, there is a lot of urea. The subclass is divided into two suborders - lungfishes and lobe-fins.

Lungfishes, along with gills, have paired or unpaired lungs, developing from a swim bladder, in the walls of which blood capillaries branch abundantly (it is preserved in the brown protopter). They breathe with their mouth closed, through their nostrils.

The atrium is divided by an incomplete septum into right and left halves, i.e. it is already three-chambered. They have two circles of blood circulation (first: heart - lungs - heart; second: heart - whole body - heart).

Modern lungfishes - cattails or ceratodes, lepidosirens, protopterans live in drying up reservoirs, and survive the dry season by burrowing into the ground.

Lobe-finned fishes evolved from common ancestors with lungfishes. They originally lived in fresh water bodies, in which there was a periodic lack of oxygen. With a lack of oxygen, they rose to the surface like modern lungfish and swallowed air.

A feature of these fish is the presence of muscles in the limbs and the dismemberment of their skeleton. This turned out to be a prerequisite for the transformation of fins into five-fingered limbs.

In the early stages of their development, lobe-fins split into two branches. One of them became extinct, becoming the ancestors of amphibians, and through them, other vertebrates. The other part went to sea and was considered extinct until 1939. The coelacanth turned out to be ovoviviparous; its large eggs mature for a year in the oviducts of the female, which then gives birth to living descendants.

Superclass Quadrupeds

Class Amphibians (Amphibians)

Amphibians occupy an intermediate position between true terrestrial and aquatic vertebrates: reproduction and development (of eggs and larvae) occurs in the aquatic environment, and adults live on land. About 3,500 species are known.

Adult amphibians are characterized by:

Five-fingered limbs;
lungs;.

Three-chambered heart and development of the second (pulmonary) circle
blood circulation;

Formation of the middle ear.

Lake frog lives in bodies of water or on their banks. The body consists of a head, torso and limbs. The head is relatively movably connected to the body, flattened, with a large mouth and a pair of external nostrils, bulging eyes, behind which are two rounded eardrums.

Frog skin naked, rich in skin glands that secrete slime(it has bactericidal properties and facilitates gas exchange); equipped with a dense network of blood capillaries.

Skeleton: spine, skull, limbs.

The spine is divided into four sections:

cervical- one vertebra, movably attached to the occipital part of the skull and providing mobility of the head;

trunk(the frog has no ribs or chest);

sacral- one vertebra articulated with the pelvic girdle;

tail- vertebrae of the caudal section, fused into one single bone.

The skull is wide and flat, represented by the bones of the braincase and jaws, and contains a lot of cartilaginous tissue. The limb skeleton includes:

Skeletons of limb belts: shoulder girdle(lies in the thickness of the muscles) - paired shoulder blades, collarbones And crow bones(coracoids) connected to the sternum; pelvic girdle(attached to the sacral vertebra) - paired iliac, sciatic And pubic bones fused together to form pelvis;

Skeleton of free limbs: skeleton of the forelimb - shoulder(brachial bone), forearm(fused radial
And ulna bones), brush(bones of the wrist, metacarpus and phalanx
fingers); skeleton of the hind limb - hip(femoral
bone), shin(fused big And small tibia bones)
And foot(bones of the tarsus, metatarsus and phalanges of the fingers).
The musculature differs between the muscles of the head, torso and limbs. Part of the trunk muscles is segmented.
Well-developed muscles provide movement of the limbs and movement of the lower jaw.

In the digestive system, the following are distinguished: the oropharyngeal cavity (contains the tongue, attached at the front end to the lower jaw, and its rear end is thrown out of the mouth when catching prey); the teeth on the upper jaw serve only to hold prey; the secretion of the salivary glands does not contain digestive enzymes), esophagus, stomach, small intestine (the ducts of the liver and pancreas flow into the duodenum), large intestine, cloaca - a special expansion of the rectum into which both the ureters and the ducts of the reproductive organs flow. All amphibians feed only on mobile prey. Respiratory organs: lungs of simple structure, having a small respiratory
surface; respiratory tract: nostrils, oropharyngeal cavity, choanae, laryngeal-tracheal chamber (vocal cords are located here); air is forced into the lungs due to the movement of the bottom of the oropharyngeal cavity (while the external
the nostrils are closed by valves); "

skin and mucous membrane of the oropharyngeal cavity - additional respiratory organs;

Gills are found in tadpoles and some aquatic amphibians. In the circulatory system two circles of blood circulation(large and small - pulmonary). Three-chambered heart consisting of two atria(in the right atrium - blood is predominantly venous, in the left - arterial) and one ventricle(mixed blood ) . The conus arteriosus emerges from the ventricle, and from it comes the trunk of the aorta, which is divided into three

pairs of vessels:

Carotid arteries, which carry arterial blood to the head;
aortic arches, which carry mixed blood to the organs of the body;

Pulmonary cutaneous arteries carry venous blood to the lungs and skin.

The pulmonary (pulmonary) circulation begins with the cutaneous pulmonary arteries and ends with the pulmonary veins flowing into the left atrium. The systemic circulation begins with the aortic arches and carotid arteries, and ends with the vena cava flowing into the right atrium. In addition, oxidized blood from the skin enters the superior vena cava, so the blood in the right ventricle is mixed, and not

venous.

Due to the fact that the body organs are supplied with mixed blood, amphibians have a low metabolic rate, so they, like fish, are cold-blooded animals.

The excretory organs include: paired trunk kidneys (here the blood is freed from waste products), ureters, cloaca, bladder (in it, like in the kidneys, water is reabsorbed). After the bladder is full, concentrated urine returns to the cloaca and is excreted from the body. Some metabolic products and a large amount of moisture are released through the skin. These features did not allow amphibians to completely transition to a terrestrial lifestyle.

The nervous system includes: the brain, spinal cord and

nerves. The brain consists of five sections:

The forebrain, relatively large, is divided into two hemispheres, has large olfactory lobes;

Diencephalon, well developed;

Midbrain, relatively small;

Cerebellum, poorly developed, which is associated with monotony

movements;

the medulla oblongata, relatively large, serves as the center for the regulation of the respiratory, circulatory and digestive systems.

The sense organs correspond to the transition to a partially terrestrial lifestyle of amphibians:

The organ of vision is the eye, protected by movable eyelids
(the secretion of special glands moistens the cornea and protects it from drying out), has a convex cornea and a lens-shaped lens; many have developed color vision; the organ of smell is the olfactory sacs, which open outward with the nostrils, and into the oropharyngeal cavity with the choanae and

operating only in air);

Organ of taste - taste buds in the oral cavity and on the tongue;

Hearing organ - except the inner ear, middle ear(device
amplification of sound vibrations), in which there is one auditory ossicle; the middle ear is separated from the external environment bar
bath membrane.

Lateral line organ - only in tadpoles and aquatic animals
representatives.

All amphibians are dioecious, and sexual dimorphism is often pronounced. Reproductive organs: in females - paired ovaries and oviducts flowing into the cloaca; in males - paired testes, vas deferens, flowing into the ureters (Wolffian canal), opening into the cloaca. In most amphibians, fertilization is external (in water). Development with metamorphosis occurs in water. Larvae emerge from the eggs - tadpoles, similar to fish: they breathe with gills, a two-chambered heart and one circle of blood circulation, there is a lateral line organ, there are no paired limbs. After two to three months, the tadpole turns into a frog. Some amphibians have developed care for their offspring (midwife toad, tree frogs, South American pipa).

What are the functions of the musculoskeletal system?

The musculoskeletal system performs the functions of support, maintaining a certain shape, protecting organs from damage, and movement.

Why does the body need a musculoskeletal system?

The musculoskeletal system is necessary for the body to maintain vital functions. It is responsible for maintaining shape and protecting the body. The most important role of the musculoskeletal system is movement. Movement helps the body in choosing habitats, searching for food and shelter. All functions of this system are vital for living organisms.

Questions

1. What underlies the evolutionary changes in the musculoskeletal system?

Changes in the musculoskeletal system had to fully ensure all evolutionary changes in the body. Evolution has changed the appearance of animals. In order to survive, it was necessary to search for food more actively, to hide or defend better from enemies, and to move faster.

2. Which animals have an exoskeleton?

The exoskeleton is characteristic of arthropods.

3. Which vertebrates do not have a bony skeleton?

Lancelets and cartilaginous fish do not have a bony skeleton.

4. What does the similar structure of the skeletons of different vertebrates indicate?

The similar structure of the skeletons of different vertebrates indicates the unity of origin of living organisms and confirms the evolutionary theory.

5. What conclusion can be drawn after becoming familiar with the general functions of the musculoskeletal system in all animal organisms?

The musculoskeletal system in all animal organisms performs three main functions - supporting, protective, and motor.

6. What changes in the structure of protozoa led to an increase in the speed of their movement?

The first supporting structure of animals - the cell membrane - allowed the body to increase the speed of movement due to flagella and cilia (outgrowths on the membrane)

Tasks

Prove that the complication of the amphibian skeleton is associated with changes in the habitat.

The skeleton of amphibians, like other vertebrates, consists of the following sections: the skeleton of the head, torso, limb girdles and free limbs. Amphibians have significantly fewer bones than fish: many bones are fused, and in some places cartilage is preserved. The skeleton is lighter than that of fish, which is important for terrestrial existence. The wide flat skull and upper jaws are a single formation. The lower jaw is very mobile. The skull is movably articulated to the spine, which plays an important role in terrestrial food production. The spine of amphibians has more sections than that of fish. It consists of the cervical (one vertebra), trunk (seven vertebrae), sacral (one vertebra) and caudal sections. The tail of a frog consists of a single tail bone, while that of tailed amphibians consists of separate vertebrae. The skeleton of the free limbs of amphibians, unlike fish, is complex. The skeleton of the forelimb consists of the shoulder, forearm, wrist, metacarpus and phalanges of the fingers; hind limb - thigh, tibia, tarsus, metatarsus and phalanges. The complex structure of the limbs allows amphibians to move in both aquatic and terrestrial environments.

Exoskeleton

hard parts that cover the body of an animal and serve to protect it and attach muscles. They can be an external secretion of the skin (for example, the chitinous skeleton of articularopods) or develop in the thickness of the skin itself (for example, the N. skeleton of echinoderms). N. skeleton of the first kind is sometimes called cutaneous, in contrast to the second - cutaneous.

Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron. - S.-Pb.: Brockhaus-Efron. 1890-1907 .

See what “Exoskeleton” is in other dictionaries:

exoskeleton- exoskeleton The outer covering of an animal, which both provides rigidity to the body and serves for protection; usually developed in crustaceans and echinoderms Topics oceanology Synonyms... ... Technical Translator's Guide

This term has other meanings, see Skeleton (meanings). Skeleton of a blue whale ... Wikipedia

- (from the Greek skeletos, literally dried), a collection of hard tissues in an animal body that serve as support for the body or department. its parts and (or) protecting it from mechanical damage. damage. In some invertebrates the S. is external, usually in the form of a shell or... ... Biological encyclopedic dictionary

SKELETON- (from the Greek skeletos dried) animals is a system of relatively dense formations that make up a more or less durable skeleton of the animal or its parts. On the one hand, skeletal formations protect more delicate tissues and organs... ... Great Medical Encyclopedia

Dense formations located inside the body of an animal and constituting its skeleton (internal S.) or covering the animal’s body from the surface (external S.). Internal S. is characteristic of vertebrates. Some vertebrates also have an external S.... ... Geological encyclopedia

Skeleton- (human): 1 skull; 2 collarbone; 3 spatula; 4 shoulder; 5 spine; 6 pelvic bones; 7 thigh; 8 foot; 9 tibia; 10 brush; 11 ulna and radius bones; 12 ribs; 13 sternum. SKELETON (from the Greek skeletos, literally dried out), the totality of... ... Illustrated Encyclopedic Dictionary

- (from the Greek skeletos, lit. dried), a set of hard tissues in the body of animals and humans, giving the body support and protecting it from mechanical damage. Many invertebrates have an external skeleton, usually in the form of a shell or cuticle.… … Big Encyclopedic Dictionary

SKELETON, huh, husband. 1. A set of solid formations that make up the support, the skeleton of the human and animal body. S. human. Skeletal bones. External village (in invertebrate animals). Like s. who n. (very thin, emaciated). 2. transfer Frame (in 1 digit), frame... Ozhegov's Explanatory Dictionary

Solid support for the animal’s body, places of muscle attachment, and sometimes protection if the S. is external. It is necessary to distinguish S. from the shell, which serves primarily for protection and then for muscle attachment. The shell is a selection of famous... ... Encyclopedia of Brockhaus and Efron

- (from the Greek skeletos, literally dried) a set of hard tissues in the body of animals and humans that provide support to the body and protect it from mechanical damage. There are external and internal S. In most invertebrates S.... ... Great Soviet Encyclopedia