Chickens are the most common poultry. They belong to the pheasant group, to the genus crested. Knowledge of the anatomical structure of the chicken and physiological features will help the farmer learn to quickly recognize abnormalities in the development of pets and painful conditions, as well as solve some of the nuances when cutting the carcass after slaughter.

Bird Features

Poultry is divided into keel and ratites. Chickens belong to ratites. In their anatomical structure, they are close to reptiles, but due to the ability to fly and think, they are distinguished by a number of unique characteristics.The main distinguishing features of birds:

• lack of teeth;
• the presence of a horny cover on the jaws forming a beak;
• ability to lay eggs;
• dry skin;
• the presence of plumage;
• indicative zygomatic orthodrome;
• mobility of a square bone;
• ribs with hook-shaped processes;
• metatarsal adhesion of the pelvic bones;
• highly organized brain;
• streamlined contours;
• uneven muscle position, providing movement and flight;
• entrails are displaced closer to the center of gravity of the body;
• the intestines are shortened, but the secretory functions of the gastrointestinal tract remain at a high level.

Did you know? The chicken brain is able to simulate 24 behavioral signals that are used in various situations. Moreover, the formation of the signal can be produced not only by visual inspection, but also with an audio signal from another bird. Upon receiving such a message, the chicken’s brain immediately gives her an image that causes a certain reflex: to run to the feeder, to flee or to transmit a war cry.

The structure of the skeleton of a chicken

The chicken skeleton is facilitated due to compact mineralization, high spongy friability and pneumatization in combination with early fusion of seeds. A porous structure accumulates in the bone marrow sinus of chickens before the entry into the egg-laying phase.

If there is enough calcium in the diet of the bird, the porous structure completely fills the bone marrow sinus. In the process of life, it is spent on the formation of the hard shell of the egg.With calcium deficiency, the porous structure does not have time to restore its volumes, and the building material is consumed from the bones from the bones, which makes them brittle.

The skull box consists of:

• occipital;
• wedge-shaped;
• trellised;
• two temporal;
• the crown of the head;
• frontal bone plates.

In the first 24–48 hours from the moment the chicks hatch, the seams connecting the bones are still visible. In adults, the seams on the cranium are not noticeable. The skull forms under the weight of the eyeballs. Under their influence, the ocular pterygoid processes of the sphenoid bone grow to the ethmoid plate, forming a septum between the eyes.

The brain part of the cranium does not grow beyond the orbits. The occipital lobe contains 1 condyle, which increases the amplitude of movement.

In the construction of the facial skeleton involved:

• 2 mobile intermaxillary;
• maxillofacial;
• nasal;
• tearful;
• pterygoid;
• palatine;
• zygomatic;
• squared;
• mandibular;
• opener;
• hyoid bones.

Incisors, maxillary and nasal structures form the top of the beak. Nasal lamellar segments have a springy structure, which ensures the simultaneous raising of the upper and lowering of the lower beak.

Did you know? In the tyrannosaurus soft bone tissues, proteins were found that are identical to those found in similar tissues in chickens.

In the cervical region of the chicken there are 13-14 mobile shortened vertebrae with spinous processes. Their transverse compartments are well developed. The bone heads are distinguished by a complex relief, which allows for reduction, relaxation, abduction and limitation of rotation.

The thoracic segment is shortened, hardly moves, in addition to the sternum, includes 7 ribs. From the 2nd to the 5th vertebrae are combined and form an integral bone of the back, the 1st and 6th are free, and the 7th is combined with the first sacral. Each rib is formed from vertebral and sternal ossified cavities.

2-3 initial ribs are asternal, the rest are sternal. Vertebral ends end with hook-shaped processes that protect the sternum. Between her and the ribs are localized joints.

The sternum is represented by an elongated flat bone structure with a concave upper lobe and keel on the ventral plane. The department is a fastening material for the most powerful muscle tissues.

The final thoracic, lumbar, sacral and initial vertebrae of the tail form the lumbosacral part, which includes 11-14 segments. On both sides of the sacro-lumbar bone are pelvic segments. The tail of the chicken includes 5 scattered vertebrae and 4-6 connected in a triangle to which the tail feathers are attached.The ability to fly appeared due to a decrease in bird weight due to hollow bones and the formation of a wing consisting of a belt and a limb.

The shoulder girdle includes:

• paddle plate;
• collarbone;
• coracoid bone.

Extremity make up:

• shoulder segments;
• forearm;
• shortened brush.

The pelvis forms the iliac, uterine and ischial bones. The uterine and sciatic parts are not fused. The female’s pelvis is different from the male’s pelvis with a wide entrance with soft bone walls, which allows the egg to exit without injuring the bird.

Important! The mass fraction of bones in the carcass of an adult is 10%. During the first 2 months. life skeleton is developing rapidly. The ability of bones to grow is maintained for 6 months.

Lower limb includes:

• hip;
• shin;
• metatarsus with well-developed long finger-shaped processes.

The bones of the upper and lower extremities are long, tubular, pneumatic.

The structure of the internal organs

The insides of the chicken in anatomical structure differ from mammals familiar to humans. Most sensory organs are highly developed due to the improved organization of nervous activity. Let us consider in more detail the internal structure of the chicken body.

Respiratory system

The chicken body is provided with oxygen through:

• nasal passages;
• upper and lower larynx;
• trachea;
• bronchi;
• lungs;
• valves with air.

The nasal space is reduced. The nasal passage is formed by three cartilaginous curls. Here, the air is filtered and purified from harmful impurities, and then enters the oropharyngeal cavity and trachea. The upper larynx is located behind the root of the tongue.

It is an oval pillow-shaped soft tissue, divided by the entrance to the larynx. The singing larynx is located at the end of the trachea. It is formed by 3 rings, simultaneously participating in the formation of the drum department for reproducing sound frequencies along with the left bronchus.

A trachea is an elongated tubular cavity made up of ossified and cartilaginous rings connected by a ligamentous material. Infusing into the chest cavity, the trachea branches into 2 bronchi. The motor function of the trachea is provided by the clavicular-tracheal and sterno-tracheal muscles.

The bronchi flow into the corresponding lungs. At the entrance to the lungs, the bronchial branches expand, lose their cartilaginous rings and, under the guise of elongated membranes, enter the airway valves.

Nervous system

In a hen, the nervous system is divided into central and peripheral, providing communication with the outside world and behavioral reactions to stimuli by transmitting ion impulses.

CNS is represented by:

• the brain;
• spinal cord;
• spinal nodes.

The brain segments are distinguished by a highly developed organization. PNS is represented by nerve receptors - branches of the brain and spinal cord.

Important! Analyzers are located throughout the chicken’s body, representing a complex structure of the interaction of the brain, receptors, and conductors. Analyzers have their own peripheral system consisting of receptors, each of which is responsible for the perception of a certain stimulus.

A large number of ion-transmitting receptors provides an accelerated response of chicken to irritants. Even after chopping off the head, the bird is able to survive for some more time, because the nerve cells still continue to give signals to the body, prompting it to act.

Digestive system

The digestive system provides:

• food intake;
• its machining;
• splitting to easily digestible particles.

The digestive apparatus includes:

• beak;
• pharynx;
• upper and lower esophagus;
• goiter;
• stomach;
• small intestine;
• appendix;
• liver;
• pancreas;
• gall bladder;
• the rectum;
• cesspool.

Through the beak, food is captured. The mouth is divided into 2 parts. The first includes a narrowed, hard palate, covered with mucous tissue, and papillary processes directed to the throat, pushing food. At the bottom is the tongue.

Its tip is covered with a layer of a keratinized dermis, and filiform processes are localized on its root. The pharynx is located between the mouth and esophagus.The external section of the esophagus begins from the pharyngeal cavity and ends with goiter, the lower stretches from the goiter to the secretory gastric section.

Important! Goiter is a supplement to the esophagus. This is the result of evolution. Food is stored in it and partially decomposes into carbohydrate compounds. In aquatic representatives, this organ is absent.

In the glandular stomach, hydrochloric acid is produced, which is necessary for the breakdown of food. The muscle stomach is located on the left side of the liver. In shape resembles a disk with thickened shells. The intestines are represented by a hollow tube, folded in rings, fixed on the mesentery.

Its length is proportional to the age of the bird and depends on the structural features of the food. The intestines are divided into thin and thick.

The first includes:

• appendix;
• jejunum
• epigastrium.

The small intestine has a length of 150 cm. Located at the back of the liver. At the junction of the small and large intestine is a valve of 1-2 ring folds. The large intestine is histologically similar to the thin one, but contains a larger number of goblet bodies, providing an abundant secretion of mucus.

The rectum is the widest section of the system. It forms feces. The rectum ends with a cloaca, which is divided into rings into 3 sections.

The liver is the largest gland in the body of the chicken. Provides the accumulation of glycogen and minerals, as well as protection against toxins penetrating the stomach. At the stage of development of the embryo, the liver performs a hematopoietic function.

It is located behind the heart muscle. It has the shape of a dome directed upward. Divided into 2 parts by a thin jumper.

The pancreas tubular-alveolar gland includes 2-3 segments. Located in the loop of the appendix. It features an elongated shape.

The gallbladder is located at the right hepatic lobe. It has an elliptical shape. Bile from it enters directly into the duodenum.

Circulatory system

Hens are warm-blooded creatures.

Their circulatory system is represented by:

• heart;
• blood vessels;
• structures transporting lymph.

In chickens, blood flow passes through a closed chain of large and small circles that are not in contact with each other. The heart is represented by a large muscular organ enclosed in a pericardium. Compared to the description of the location of the heart of mammals, in chickens it is shifted to the right, covered by air-breathing valves.The heart is divided into 4 cameras:

• left and right atria;
• left and right ventricles.

Blood supply to the heart muscle is via 2 coronary arteries, and outflow through 3 veins.

The lymphatic system is presented:

• lymph nodes;
• capillaries;
• lymph spaces;
• lymph vessels.

The main function of lymph is to return protein compounds, trace elements and water from organ tissues to blood vessels for subsequent processing and use.

Highlight system

The urine excretion system is represented by the kidneys and ureters, which flow into the middle part of the cloaca. The kidneys support the physiological functionality of cells by increasing or decreasing the performance of alkalis and acids. Bodies are divided into 3 indistinctly marked shares.

Unlike mammals, chickens do not have a bladder, and urine is converted into a mushy mixture, which makes it indistinguishable from feces.

The ureters are represented by primary and secondary branches that originate from the kidneys. There are no glands in the ureters. Organ contraction controls the sympathetic nerve.

Reproductive system

In the female, the reproductive system is represented by the oviduct and the ovary, in which the yolk is formed. In an adult, left appendages fully located on the right are fully developed - they remain in an atrophied state.

The yolk moves along the oviduct, where it grows:

• protein;
• subshell film:
• lime shell.

Did you know? In a chicken that has not yet entered the egg production phase, the length of the oviduct is 10–20 cm with a diameter of 0.3–0.8 mm. During the period of maximum productivity, its length increases to 40-60 cm, and its diameter reaches 10 cm.

By functionality and morphology, the oviduct is divided into:

• funnel-shaped process;
• protein division;
• adapter;
• uterine cavity;
• vagina.

The outer part of the oviduct is a funnel, which, due to muscle contraction, can move back and forth and capture the yolk from the ovarian cavity.In the protein department are glands that secrete protein compounds. Through a short isthmus, a full-fledged egg moves into the uterus, and then into the vagina, which opens into the cloaca.

In the male, the reproductive system is represented by the testes and vas deferens. The left testis functions better than the right. They are oval and localized above the kidneys. Each testis together with the appendage is enclosed in a joint capsule.

Appendages are clearly visible only during sexual activity. 2 vas deferens, representing crimped tubes, depart from the appendages. When entering the cesspool, the vas deferens expands. Around this expansion are capillaries.

Important! Roosters lack mating organs.

Breeding of chickens occurs through the cloaca, which bulges outward. At the moment when the rooster tramples the chicken, their cesspools touch and the seminal fluid from the testes enters the female genitals.

Feather & Leather Features

The outer layer of the dermis is small in thickness. Under it is located the malpigian layer, consisting of cylindrical cells that are distinguished by the ability to reproduce their own kind.

A characteristic feature of the epidermis of chickens is the ability to form feathers. True skin is hidden by the epidermis. It consists of subepithelial and friable layers. The first is the skin muscles that provide the movement of the feathers.Fat deposits accumulate in the loose layer, the thickness of which depends on seasonality and nutrition. Fat is the reserve structure of the body, from which the bird draws energy during a period of increased activity.

Nerve processes and tactile tubules are located in the skin, which are highly sensitive, especially in places free from plumage. The pigment is concentrated in the epidermis and feathers, which is responsible for the color of the skin and feathers. May be a derivative of melanin or keratinoids.

Feathers play a protective role for the epidermis and are involved in coordinating the movements of the musculoskeletal system.

Chickens differ in their morphological and physiological structure from most mammals. Improved sensory organs and a complex system of higher nervous activity ensure high survival of birds in any corner of the planet.